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THE
PAINTER AND VARNISHER'S
GUIDE;
OR,
BOTH IN THEORY AND PRACTICE,
ON THE ART OF
MAKING AND APPLYING VARNISHES ;
ON THE
DIFFERENT KINDS OF PAINTING j
AND ON
THE METHOD OF PREPARING COLOURS
BOTH SIMPLE AND COMPOUND:
WITH NEW OBSERVATION'S AND EXPERIMENTS ON COPAL; OW THE NATURE OK THE
SUBSTANCES EMPLOYED IN THE COMPOSITION OF" VARNISHES AND OF
COLOURS-, AND ON VARIOUS PROCESSES USED IN THE ART.
BEDICATED TO THE SOCIETY AT GENEVA FOR THE ENCOURAGEMENT
0Î THE ARTS, AGRICULTURE, AND COMMERCE.
BY P. F. TINGRY,
PROrEJSOR OF CHEMISTRY, NATURAL HISTORY, AND MINERALOOT
IN THE ACADEMY OF GENEVA.
ILLUSTR.\TED WITH ENGRAVINGS.
LONDON:
PP.1NTED FOR G. KEARSLEY, FLEET-STREET,
By J. Taylor, Black-Horse-Court.
1804.
5os-
TC '4':^'
^
AUTHOR'S PREi^gfe.^^
The Society established at Geneva for the En-
couragement of the Arts, Agriculture, and Com-
merce, charged its Committee of. Chemistry to
take into consideration those arts of which no
methodical descriptions had been given by the
Academy of Sciences at Paris. It was, indeed,
intended by the Academy that the art of var-
nishing should form a part of their collection ;
and de Machy, one of the members, had, I
believe, prepared some materials for that pur-
pose, but on the publication of Watin's work
in 1772 he seems to have abandoned his
design.
This art, which is of modern date in Europe,
notwithstanding the assistance thus given to it
by Watin, still required that the principles on
which it is founded, and by which it can be
carried to perfection, should be more fully ex-
plained and illustrated. Every thing that re-
lates to the history of the colouring parts, and
to the operations which make them appear witli^
their true properties, has in that publication
been either omitted or neglected. The Com-
a2
74-
IV AUTHOR S PREFACE.
mittee of Chemistry, in consequence of some
observations which I had made on the arts in
my pubHc or private lectures, were of opinion
that a new work on this subject would form a
valuable and even necessary addition to that of
Watin: they conceived also, that as this art is
one of those wliich are entirely founded on
chemistiy, it ought to be treated according to
the modern system. I engaged to undertake
this labour; and I now present the result of it
to the public, with the approbation of the So-
ciety to whom I have dedicated it.
INTRODUCTION.
1 HOUGH it is commonly supposed that painting in oil was
not known before the fourteenth century, it is probable ^hat
the antients employed it for ornamenting their porticoes.
The fragments of painting with which the fronts of some
of the edifices discovered among the ruins of Hercvdaneum
and Pompeia are still decorated, and which have escaped the
ravages of time, and the impression of the volcanic ashes
under which they were buried, appear to me sufficient au-
thority for this observation.
But the wars which hastened, and those which followed,
the fall of the Roman empire j the almost general devasta-
tion which was the result of them ; the conversion of po-
lished nations, by a series of calamitous circumstances, into
Goths and Vandals ; and the ages of barbarism which suc-
ceeded, dissipated the last traces of industry and of the
progress of civilization ; changed or corrupted every thing,
and even the language of the subjected nations, which
a state of oppressive servitude reduced and accustomed to
the mere necessaries of life.
Those accumulated scourges to which Europe was ex-r
posed were, however, confined within certain limits, by
that desire wJiich men have for peace when nothing more
remains for them to destroy ; and by that peace itself^ which'
gradually restores them to the use of their reason, and
brings them back to the dignity of their nature.- Their
physical strength is then employed in seconding the efiorts
of the imao;ination and of genius. Their thou i>;hts are em-
ployed on new objects ; discoveries are multiplied ; com-
mercial intercourse is re-established between nations ; the
wants of society are enlarged in proportion to the extent of
a.3
AI INTRODUCTION.
this communication^ and a desire of enjoyment increaseâ.
All these effects, the result of a more settled state of go-
vernment, soon tended to ameliorate agriculture j to im-
prove the necessary arts ; to extend those which contribute
to heighten the comforts of life; and to call forth those
sciences which form the chief glory of nations.
It is, no doubt, unfortunate that the scourges which,
during the different convulsions among mankind, poison in
this manner all the sources of public happiness ; which fall
heavily on enlightened nations, and either disperse or en-
tirely destroy them, should leave to their successors only
fragments that have escaped the general devastation. Th»
sciences disappear with men of talents. It then becomes
necessary to open new routes on a degraded soil, and the
genius which advances in the career of discovery often ar-
rives, after much labour, at results of which anterior ages
have left some faint traces. Every thing connected with
the secrets of industry would, no doubt, have been saved,
had the valuable discovery of those processes which consti-
tute the art of printing preceded that of the mechanical
arts.
It appears almost certain, that the varnishes which have
been made and employed for many centuries by the nations
who inhabit the eastern parts of Asia were in part known
also to the Romans. The ruins of Pompeia remove every
doubt in regard to the use which these people made of oil
painting to ornament their buildings. Some pieces of their
copper coin, struck under the reign of Trajan, and dug up
from antient ruins, are covered, as Count Caylus remarks,
with a kind of resi'^ious varnish, similar to that which
would result from a mixture of oil and black pitch*. If the
* It is not possible to conceive what advantage could result from the ap-
|/!icadM of a coarse varnish, which deprived the coin of iu metallic spleji-
dour, and destroj^ed the relief of the impression, wlxicU displays the talents
of the engraver, and gives an ideal value to coin».
lîîTRODUCTION. yA
antients were ignorant of the art of grinding, mixing up,
and combining oil colours, which, however, there is no
reason to suppose ; and if they did not carry to such an ex-
tent as the moderns those mechanical processes which assist
painting of the first kind (that of picturas), it cannot be
doubted that the Greeks, in particular, were acquainted
with the art of giving lustre to the colours which they em-
ployed in their fine compositions, and also of preserving
them.
The names of a Timanthes, a Zeuxis, an Apollodorus, a
Polygnotus, a Pausias, and a Parrhasius, who by their warm
compositions added lustre to the ages of Pericles and of
Socrates ; who combined grace of disposition with bright-
ness of colouring ; boldness of design with mellowness of
execution ; and who produced masterpieces which exist
only in the descriptions transmitted to us, show how great
were the losses which followed the destruction of liberty
among the Grecian republics. Their means, without being
so extensive as ours, were sufficient, according to the ex-
pression of Parrhasius, to give their compositions as much
solidity as enabled them to withstand the influence of the air.
It is well known that oily or resinous matters were mnch employed amon-^
the Romans. The use of perfumes, sepulchral lights, and flambeaux, was
very extensive In their public and private ceremonies. A resinous kind of
cement was much employed also by these people in building. It is, there-
fore, probable that the conflagrations by which Rome and so many other
fine cities were destroyed, and the revolutions of which Italy was tliq
theatre, may have been the real causes of that resinous incrustation ob-
terved on some of the Roman copper coins dug up from antient ruins. It
seems to be probable also, that similar accidents, by which various jnatters
were mixed in confusion and buried for so many centuries, may have given
rise to thzt patine so much esteemed by antiquaries, which they seek for on
certain coins, and which seems to be merely a production of time. Thç
decomposition of water, and the oxidation which is a certain result of it,
are, no doubt, the principal causes of the formation of this crust, or smooth
and sometimes shining paste, which is so gratifying to the eager eye of th#'
antiquary.
VIIl INTRODUCTION*.
But were Apellcs, Protogcncs^ and Aristitles, who suc-
ceeded to the glory of these early painters, and who in some
things even surpassed them, better acquainted with the art
of preparing colours, and the means of giving them more
body and more solidity? — If the preservation of the colour-
ing was owing to a varnish, or to substances capable of
making a varnish, did thev mix them, as some modern
painters do, with the colouring parts, even when distributed
on the palette ? — or did they reserv'e them to be applied to
the composition after it was finished ?
There is no monument in existence which can enable us
to resolve these jjuestions. The masterpieces of Apelies,
and those of the painters who preceded him, disappeared
with the generations who saw them produced. Gum water
and wliite of egg, which are still employed for certam
pieces of painting, v;erc not perhaps neglected. Being ill
calculated, however, by their nature to resist the impression
of moisture, and the vxashing rendered necessar)' in conse^
quence of their being dirtied by insects, they could not be
any security to artists that their v.orks would be handed
down unimpaired to posterity. The mixture of oils and
resins, and that of resins with alcohol (spirit of ^^ine),
which form real varnishes, are alone endowed with the va-
luable property of checking the ravages of time. Since no
trace of the compositions of the antient masters remains,
there is reason to presume that our means were unknown to
them; or that they employed processes less effectual; or that
their works were condemned to the same fate as so many
other productions of human industry, and were lost in the
wreck of time.
If we even suppose that the Greeks had acquired by their
commercial intercourse some knowledge of the Chinese
varnish, they could not apply it to their fine paintings, both
on account of the consistence which that varnish is known
INTRODUCTION. IX
to possess, and of its colour, which must have presented an
obstacle still more insurmountable.
The same Greeks, however, were in possession of a kind
of painting which was attended with the advantage of brav-
ing the influence of the air and of the sun, and of not being
subject to those reflections of light which render it neces-
sary that oil paintings, to be seen with advantage, should
be placed in a particular situation ; I here mean encaustic,
or painting in wax, which was lost, and which was revived
by two celebrated men in the last century.
Vieu, a very ingenious painter, to whom the fine arts are
under great obligations, made an attempt, under the au-
spices of Count Caylus, to paint in this way a head of the
Virgin, which was engraved in the chalk manner. En-
caustic found a no less enlightened protector a few years
ao-Q in Counsellor Rafelschtein. Some Italian artists, assist-
ed by his advice, and by the encouragement which he gave
them, executed several paintings of this kind, which ob-
tained the approbation of connoisseurs.
Encaustic painting possesses more strength than that in
distemper. Its uniform mellowness produces more har-
mony in the tones, which the spectator readily catches in
every position. This method of painting does not adniit
of any kind of varnish applied after the work is tinished.
Wax, which is the essential basis of it, and which com-
bines exceedingly well vvith the colours, becomes the causa
of the consistence and pliablcness of the painting, vv'hen it
)ias received from a pretty strong heat that inustion, which
makes it penetra.te into the canvas. The canvas, v^hen it
has thus imbibed the wax, exhibits a thin flexible stratum^
which is nevertheless susceptible of a very fine polish.
Nothwithstanding all those kinds of degradation which,
the fine arts experienced under the Lower empire, and par-
ticularly towards its fall, Greece might, perhaps, still boast
of masterpieces of encaustic, from the hands of Polygno-
if INTRODUCTION.
tus of Thasos, had they not, after nuie centuries of admira-
tion, become a subject of envy or emulation to one of the-
Rôman praetors, who caused them to be transported to the
capital of the world, where they shared in the fate of so
many other valuable monuments of antiquity.
All the arts approach each other in more or fewer points,
atid in a manner more or less perceptible. This affinity is
more sensible in the mechanical arts, which are employed
on objects of the first necessity, than in those the principles.
of which depend on the progress of civilization, and which
require a knowledge of combinations, and an intimate ac-
quaintance with the materials which they consume or which
Ihey modify. A knowledge of the analogies discovered be-
tween certain resinous substances belongs to the analytical
part of chemistry : it consequently comprehends a long
series of processes ; and it docs not appear that this science,
which led to the discovery of varnish, formed a part of the
gérions occupations of the Greeks.
The greater part of the mechanical, and we may even say
of all the arts, began to be attended with conspicuous suc-
cess onlv at that period when the facts relating to them
were sufficiently connected to admit of their being formed
into a theory. This assertion;, which might be generalized,
is more particularly applicable to those arts which depend
on the cffiects of chemical combinations. At every step ob-
stacles occur ; every thing appears new and strange; and
inconstancy in the results of experiments, often intrusted
to chance, discourages in enterprises which the least know-
ledge of theory vvould render successful. It may readily be
believed that the discovery of varnish was the fruit of re-
peated trials ; and though those who made them had conti-
nually in their hands the essential materials, there was still
wanting a motive, which was soon created among peaceable
and industrious nations, by a taste for luxury, and by com-
jDercial communication.
4
INTRODUCTION, XI
Bat, if a knowledge of the theoiy which is now appHed
to certain manipulations in the arts, founded on the em-
ployment of chemical combinations, is deduced from a great
number of leading facts, so intimately connected with these
manipulations that they are a necessary and even expected
result of them, the cause of them would, perhaps, have
remained long unknown, without the influence of societies
established for the purpose of exciting and calling forth the
energies of the human mind. The public respect attached
to these associations of learned men and artists distinguished
by their merit, and still more the support of governments,
which promote experiments and enterprises that require en-
couragement, have contributed not a little towards those
interesting discoveries for which the present period is cele-
brated.
In regard to painting, some of the happiest results arising
from these associations were, that the study of history was
facilitated to young artists ; that they were surrounded, jri
some measure, with masterpieces of the old painters ; that
their judgment was exercised with respect to chasteness of
execution, propriety of arrangement, and correctness of
design ; this was rendering them familiar with real beauty,
and inspiring them, at length, with the genius of the
Greeks.
This genius, which among the Athenians in particular
was exalted by the establishment of liberty, which was
kept in full activity by commerce, and to which a spirit of
enterprise was conmiunicated by prosperity, necessarily
raised them above that simplicity of manners by which na-
tions who apply to agriculture, to those arts which are
purely mechanical, or to a pastoral life, are characterized.
This genius was formed to direct taste, to create it even,
and to soar to the sublime in all its great conceptions. This
was the case at Athens by the intercourse which the Greeks
kept up v/ith their neighbours j the latter were made to
Xll INTRODUCTION,
participate in their glory. The fine arts ha\'e their con-
quests j and these conquests arc tlie more certain as they
become minçïlcd with, and increase, our dearest enjoyments.
They produce emulation; and conduct, by a sure path, to
that taste for real heauty which announces the progress of
civihzation. ^
In tracing out these grand effects, one is naturally led to
inquire into the cause v\hich produced them. This cause
we can look for only in that rational liberty which inspires
men with the desire of employing all the resources of their
talents; which, by an insensible gradation, raises one indivi-
dual above another ; which induces them to divest them-
selves of all envy on account of merit different from their
own, or which surpasses it ; and which makes them seek
happiness in a continued intercourse with virtuous citizens,
Avhom the public opinion has invested with respect. Such
v.as the use which Athens made of her liberty during the
period of her splendour : it was in this manner that plain
citizens, but distinguished by particular talents, concurred
to produce those important results with vt'hich the interests
of nations are so intimately connected; which raise them
into notice, and which turn to the greatest benefit of man-
kind the intercourse they maintain with others.
The Greeks, in consequence of their republican institu-
tions, were able to extend much further those advantages
which we make to depend on difîerent learned societies,
such as those established in Italy, in France, and in other
countries, of Europe. Their progress, therefore, was much
more rapid than ours, and their enterprises were more
marked with grandeur. We are indebted to them for all
the splendour displayed by the fine arts among us ; but
im fortunately we do not yet possess all their riches.
But, in matters of government, the best institutions are not
sheltered from the instability attached to human affiiirs. The
prosperity of the Greek republics \va5 soon blasted by their
INTRODUCTION. • xKi
intestine divisions. The fine arts laiigmshéd, and seemed
to expire along with the flame of Ubcrty ; /and if the inter-
course afterwards renewed between the na,tiGns of antient
Greece, and those of Asia and India in particular, by the
conquests of Alexander the Great, seemed to revive the
arts in their antlent country ; if it seemed to recall the
flourishing periods of a Pericles ; it was only, as we may say,
to afford an opportunity of collecting those valuable ma-
terials which Italy and other countries were afterwards, ia
some measure, to naturalize and to improve.
The Thebaid, the most remote part of Egypt, which is
now a desert, notwithstanding the ravage of time, still
attests the influence of the fine arts of Greece on the people
of that country. It would appear, from the recent observa-
tions of some travellers who visited the ruins of Thebes,
that the antient inhabitants of this country were well versed
in all the branches of design and of painting. If the fresh-
ness which still characterizes some fragments discovered in
antient galleries buried amidst ruins, seems to prove that the
painters were then acquainted with the" same means, or others
equivalent to them, v.hich the modern painters employ to
preserve their works for posterity, — this circumstance must
afford new motives for applauding the v/onderful discovery
of the art of printing, which becomes the most certain
safeguard to the productions of the human mind against
that spirit of devastation by \Ahich all conquering nations
are animated.
I have already observed, that a state of peace in a nation
which has been agitated by long convulsions has^ a much
greater influence on the arts than any other circumstance
depending on its particular genius. The Chinese, situated
in the extremity of Asia, seem to form an exception to this
remark, the justness of which in regard to the freer na-
tions of Europe can be better appreciated. Among the
former, the uninterrupted exercise of their arts is never ex-
XIV INTRODUCTION.
tended beyond habit and routine ; but it corrects^ to a cer-
tain degree, the faults which arise from their aversion to
imitation. They are never excited by a spirit of emulation.
The son becomes the servile copyist of the works of his fa-
ther : he has no idea of improvement ', and while manipu-
lations are thought to be every thing, theory is neglected.
This is clearly observed in the methods which the Chinese
pursue in the application of their lakes -, in the style of their
painting ; in the forms which they give to the difFerent ar-
ticles of their manufacture, , and which appear to be as im-
mutable as their empire. Their transparent varnish is com-
posed of two substances only. The addition of common
colours, without variation, constitutes their different lakes ;
and the physical properties of these two substances contri-
bute more than art to the solidity of their compositions.
If the nations of Europe, and particularly the French, had
found in their territories the natural production which sup-
plies the Chinese with the principal ingredient of their var-
nish, solidity combined wàth elegance of fonn ; highly
finished painting, delicacy of design, and splendour of co-
lours, would have soon made the art of the varnisher and
painter be considered as one of the first sources of national
riches, in consequence of the extent it would have given to
various branches of commerce.
But the spirit of imitation, strengthened by the know-
ledge acquired in regard to chemical analysis, at length na-
turalized in France an art which seemed to be confined to
the remotest parts of Asia. The observations of the Jesuit
missionaries on certain arts cultivated by the Chinese, and
on some of the most important branches of their industry,
excited a spirit of emulation among artists, and induced
them to repeat the processes of their inventors ; to supply
those deficiencies which might arise from want of suffi-
cient inibrmation, in consequence of the reserve which
forms a prominent feature in the character of these people ;
INTIl)DDUCTION. XV
and to correct those faults which might' proceed from a dif-
ference in the substances employed*. The publicity of these
observations marks out the period of Our enterprises and
success in a new series of processes before unknown ; and
the execution of them, whether servile imitations or modi-
fied according to the ingenuity of the artists, seemed to be
so much connected with our enjoyments, that there was rea-
son to conclude the result w^ould be a suflkiency of mate-
rials and information to enable artists to subject the. mecha-
nical processes to correct principles, as well as invariable
rules; and to add a new art to those already known.
In the year 173/ such a spirit of emulation was excited
among the French artists, in consequence of some models
or varnished articles brought from China, and such an en-
thusiasm for imitating this varnish, which was rqjrescnted
as being unalterable in the fire, that people were almost dis-
posed to prefer varnishe' to metallic vessels.
The dreams of the credulous alchemists were not entirely
useless to the chemists who succeeded them : in the same
manner, this ephemeron enthusiasm was not lost to society.
The imagination, when it dwells for a long time on one ob-
ject, will at length arrive at some valuable discovery. These
attempts to obtain an incombustible varnish gave birth at
length to a new art, which was the more lucrative to France
as it has not, like so many other objects, experienced the
effects of the inconstancy of taste. I here allude to the art
of making varnished paper snufi-boxes, &c.
Among the artists employed in this new branch of in-
dustry, there was one for whom it was reserved to extendits
limits, by applying it to objects of luxury of the highest
importance. The celebrated Martin, being furnished with
good compositions of varnish, soon combined the two kinds
* See Lettres édifiantes et cvricuses published by the Jesuits. The details of
Father d'Incarville respecting the Cliijiese varaish may be found in the M/'
mvires des Savons Mirangers, vol. iii.
Xvi /•■' , /? INTRODUCTION.
." •^' ., ■ '-:-'^
cf.p,gnntihg. Ifft>talled in to his aid the art of the gilder,
anid gàye ib^that importance which always arises from the
wants of mé public. In a word, all the arts belonging to
coach-making received from it an assistance the more cer-
tain as thev all depend on an inexhaustible source, namely,
a taste for show, to which the opulent sacrifice every thing.
An art so fertile in resources could no longer be confined
to external objects of luxury. A taste4"or the decorations
applied to apartments, during this continued and progres-
sive improvement, was extended from palaces to the habita-
tions of the rich, and by the effect of imitation was trans-
ferred thence to the humble abode of the citizen in easy
circumstances.
The processes, however, employed at this period were
agreeable to the experience of artists who had been engaged,
for the most part, in those simple operations used for paint-
ing in distemper. The m.ost intelligent confined themselves
to a series of processes for which they were indebted to par-
ticular researches, or to communications from amateurs di-
stinguished by their fortune or their knowledge, or w hich
ihey obtained from venders of secrets, a kind of people who
are very common in professions founded on chemical opera-
tions. Each process, therefore, bore evident marks of the
ignorance or inexperience of the artist. Hence the differ-
ences obser\'ed in the colouring, brilliancy, consistence,
tenacity, or dr\Tiess of the varnish employed. The operator,
too easily satisfied with his first attempts, proceeded no
further in the improvement of his art. The secret was the
more strictly observed, as it seemed to secure a certain re-
source to the industry and family of the possessor. Hence
also that incoherence in the formulae which different works
seemed to confirm, and which they extol as the properest
for answering the intended purpose. Hence, also, that im-
jnense collection of obscure recipes, said to be derived from
the best sources, which artists of ability sooa condemn;^
INTRODUCTION.!
because they find them at variance withX&^trué-^irii^fflles
of the art. The works intitled Les Secretsn^^-ts<^ $Ie-
tiers*. Le Dictionnaire des Arts, L'Art du Veritvs^^r, Le
Parfait Vernisseurf and other small essays; of this kind,
abound with faults, arising from the bad choice of the
editors, and which deprive them of the merit attached to
good elementary works, and to methodical descriptions of
the arts.
The interest of the practitionei*, therefore, raised a barrier
which prevented the art from approaching towards theory.
It wasj however, necessary that the latter should become
the basis of all future researches, in order to throw light on
the different processes, to ascertain the nature of the results
by a rigorous comparison, and thus to establish the real
principles of the art. This happy effect was, in part, pro-
duced by the public spirit of an artist who was so generous
as to disclose some processes which I here propose to ex-
amine, presenting them in a new order of distribution, and
adding the necessary observations.
Watin, to whom I here allude, did not forget the interest
of the artist when he intrusted his precepts to the writer
charged with preparing them for the press. But while he
reserved the secret of certain processes, which were his
own, he did not observe that by contributing to reduce the
art to certain principles, he at the same time prepared means
for lessening its difficulties, and of enabling artists to arrive
speedily at that happy period when all reserve becomes use-
' A work in four large volumes, %vlth the attracting title of Secrets emu-
ctrnanr les -irts et Meiiers, was published a fewyears ago. It is a crude com-
pilation of all the processes with which the different periods of the various arts
On whicli it treats have been encumbered. The art of varnishing occupies 2
whole volume, which contains, without choice, every thing, good or bad,
relating to it. One may ri-adily perceive that it is more calculated to mislead
the arti§t amid?t a labyrinth of contradictory formula;, than to guiMe him ift
Lis progrt-ss by a series of principles which might enable him to bUiupfe
iVt^ry tiling foreign to the main ob;ect of his researches.
less.- 6r ri^iailoug. Had he lard open all his processes, he
would certainly have acted more consistent with those prin-
cijiles by which he seemâ to have been guided.
Notwithstanding his reserve, which displays in a striking
manner the spirit by which e'v'en the most experienced artists
tife influenced, his work will always form an epoch in the-
art of \'amishing. He unites in the same point of view a
series of practical precepts founded on long experience, and
which have hitherto been followed by the most intelligent
painters : but the greater part of those who in country place»
exercise thiâ profes-sion are guided in their operations by a
faulty routine. Whatever treatise may in future be written
eft this ttsêful art, it can only clear the path, which this
author has in some measure traced out, from the shackles
which real theory always imposes on the artist who is
i^ierel/ a manipulator; and no addition in this respect can
:••; .mv manner lessen the favourable opinion with A\'hich
Watin's work was received. With this spirit I undertook
to review a subject which ha» been treated by various au-
IhorSy coi\&ideriinfg it under its different aspects, combining
iif with every thing reserved for it by the new chemistry,
aftd with many other arts which seem to require from it a
.new support.
It is much to be wished that this devotion to the public
.ihtercèt were more imitated by artists of every class; but
l^artieidarly by tkose whose manipulations depend on che-
mical mixtures or combinations, as in the manufacturing
of printed cottons, the art of making paper hangings, in
dyeing. Sec, the various formulae of which are scattered
among the conductors of manufactories. These processes,
which for the most part have been the fruit of some acci-
dental circumstances, would soon experience, by the free
concurrence of artists and chemists, advantageous modifi-
«•ations which w^oyijd lead to new discoveries. Society
would thus be writhed with good descriptions of the artsj
INTRODUCTION. xix
and thege would add to the great importance attached to
those valuable collections published by the ci-devant Aca-
demy of Sciences at Paris, in regard to objects which have
a powerful influence on the happiness and prosperity of
empires.
It is not my intention to follow the art of the varnisher
through all the details which may seem suited to those
artists who are more particularly employed in the decoration
of carriages and other objects of luxury. I shall more im-
mediately confine myself to an illustration of the principles.
These alone are applicable to all circumstances in which the
painter and varnisher are interested. They will lose no-
thing by being condensed: and if they conduct the pupil
and amateur, ûy a sure path, to that eminence from which
they can see the extent of the art, they cannot be foreign to
those complete artists who, by their talents and their mas-
terpieces, contribute to feed the luxury of large cities.
My object is to place in a conspicuous point of view every
thing that can assist the varnisher and painter in regard to
matters which fall within the province of their profession ;
and, in some measure, to conduct the amateur by the hand.
The composition of varnish is connected with a particular
ki^id of knowledge respecting the physical and chemical
properties of the dry or liquid substances which form its
constituent parts. The study of these objects must induce
artists to follow them in the effects which arise from the
extreme division they expeyience, wnen brought into con-
tact, according to certain laws. The kind of chemical phse-
nomenon which takes place in the latter case depends, then,
on rules and precepts established by experience. The art is
gradually enlarged by all those parts which seem to have a
coincident, relation. Painting in distemper preceded the
discovery of painting in oil ; and the latter was some years
anterior, as appears, to the invention and application of.
varnish. These three parts touch each other in inseparable
b2
XX IXTÊODtTCTION.
points; but thcy have each their distinct rules, and are suffici-
ently rich inmattcrs to iustifv the appropriation of one divi-
sion of the work to a particular description of then». I have,
therefore, been induced to divide this treatise into two
parts.
The first comprehends an historical account of the diy or
liquid substaiices which concur towards the composition of
varnish.
The ingrredients employed in the different compositions
of varnish arc (k'scribi d, in general, in works which form
no part of the libraries of pupils or of artists.' I there-
fore considered it mv duty to introduce this subject, to
banish from it all tliose articles which are foreign to the art,
and to subjoin sucli ol^servationJ as I thought iiseful, be-
cause tliey appeared to me proper to excite a taste for study,
to facilitate insiructic i, and to concur in a direct manner
to produce that body of inlormation which is expected in a
methodical work.
It was necessary that an examination of the dry substances
should be followed by an account of the duTcrent fluids em-
ployed as excipients or vehicies in these compositions. A
mere nomsnclç'ture would not have excited that interest
which the study of thein requires : the case, however, is
different when they are exhibited under all those relations
which tend to make knov. n their nature, their particular
properties, and the modi lications resulting from the prelirai-
narv preparations to v.hich they are subjected.
I then proceed to genc^ral observations on varnishes j
which are followed by 3 distribution of them into two
classes. The latter of thtse, or that which I have here
chietly in view, is subdivided mto five genera, each contiiin-
jng a certain nuriiber of spcries, or particular kinds, whjch
are admitted into these genera according to their nature,
their consistence, and the properties of their component,
pp.vts.
INTRODUCTION. XXÎ
- This division, which is well calculated to facilitate a.
knowledge of them, is followed by an examination of gene-
ral precepts in regard to the composition of varnish on a.
large scale. The object I had here in view could have been
answered onlv In an imperfect manner if, in following all
the details of rhe manipulations, I had neglected the means
of rectifyinç^ them, in such a manner as to secure artists from
those serious accidents with which these operations are often
accompanied. I conceived that the use of an alembic of a
new form might facilitate that rotary motion \\hich must
necessarily be given to the matters inclosed in it, and at the
same time prevent those inconveniences which arise from
the too sudden tumefaction or evaporation of the Inflamma-
ble liquid.
It was neccssar)', also, that I should communicate to
artists some observations, which are still more particularly
my own, in regard to the solution of copal in essence of
turpentine, a fact contested by Watin, though it seemed to
be proved by some experiments of Lehman. The secret
cause of this difference of opinion deserves to be known,
as well as every thing that can facilitate the use of copal
varnish made with essence or with ether.
If the first part of this treatise is destined to make known
the substances which concur to the composition of varnish,
as well as the processes by which artists are en^tbled to o;ive
them the requisite properties, the second, which contains
an examination of the colouring substances, and of every
thing tliat relates to the different branches of common paint-
in<r, can be no less interesting to the artist and the amateur.
After describing these substanc :.-, I proc^'f^d to ob£er\'ations
which seem to arise f;. mt the subject ; such as those on the
origin of colours, and o;i the particr.îar processes which
cnrighthe art of varnishing ^^ith a great number of colour-
ing substances, not always fuir-lshed by nature in that state
' b3
XXU nSTTRODUCTION.
in which the painter employs them. The artist is then pre-
sented with some particular results which may encourage
him to give greater extent to the use of certain varnishes
proper for repairing enamelled aiiicles damaged by accidents.
These varnishes are attended also with another advantage,
that of favouring a new kind of manufacture, which may be
distinguished by the name of false enamel, or enamel by
varnish.
In describing the different preparations, the reader will be
conducted from the simple to the compound. He will be
enabled to follow the transitions from the lightest colours
to those which, with the same varnishes, borrov. <^rom the
nature of the colouring substances modifications of tints,
well calculated to enlarge the ideas he may have formed in
regard to the richness of the art, and the extent of the re-
sources it displays by the efforts of genius, w hen destined
for the sublime kind of painting.
It is not sufficient that artists should know how to pre-
pare or to procure the colours or varmshes which they in-
tend to apply to any article: they must know also how to
make use of them. This department of the art has its rules
and precepts, which mast be studied or consulted when the
colours employed are destined for distemper, for varnish, or
for oil. This object is of as much importance as that of
composition, and required to be treated separately.
I have taken advantage of some particular experiments to
give an account of several processes belonging to a branch
of manufacture which has a direct relation with the subject
of this work, and \\'hich, as far as I know, has never yet
been described : I here mean the art of making wax cloths
(oil cloths).
This order in the distribution of the matters to be treated
©i" would not have entirely answered the proposed purpose,
had remitted to describe^ according to the principles of th^
INTRODUCTION. XXlU
pneumatic doctrine, such objects as are susceptible of it.
There can be no doubt that this part of the work will be
that least acceptable to the artist who through habit is pn-
vvilling to give up his old nomenclature. But persons in
the least-familiar with this language will find full compen-
sation in the satisfaction which accompanies an examination
of the physical and chemical properties of the substances I
shall have to describe, and in the historical account ©f the
changes produced in then^ by art. I shall, however, still
keep in mind, that I ought to confine myself to those points
which justify the changes prescribed by the present system
of chemistry in the common expressions employed to di-
stinguish them. The addition of the terms established by
the new nomenclature, to those which are familiar to them,
will gradually accustom artists to adopt them readily wilh-
Oilt any loss to the art.
b4
TABLE OF CONTENTS.
PART THE FIRST.
CHAPTER I.
Historical account of the nature and properties of the sulsiancos
which form the basis of varnishes, and of the external qualities
ly ivhich the lest kinds may he known page 1
Asphaltum ibid.
Benjamin '. . 3
Camphor -4
Caoutchouc. Elastic resin 8
Isinglass. Fish glue 11
Copal 12
Gum adraganth or tragacanth 15
Gum arabic , » iG
Gum lac. Seed lac \y
Shell lac , ip
Mastic ibid.
Gum anima 21
Gum elemi 22
Gum guttae. Gamboge 23
Sandarac. Gum sandarac 24
Dragon's blood 25
Amber. Karabé. Yellow amber 27
Turpentine . . , 35
Turpentine of Chlo , 37
Venice turpentine 'ibid.
Turpentine of Strasburgh , 38
Common turpentine ibid.
Essential oil of turpentine. Essence of turpentine 40
Colophonium 41
White incense. Gallipot. Barras. ....,.,,,,. , "ibid,
1
XXVI TABLE OF COKTENTS.
Pine resin. Resin 42
Another method of preparing resin . . ibid.
liungnndy pilch. White pitch 43
Black solid pitch 44
T<;rc. Tar. Liquid black pitch. Brai gras ibid.
Proc::;5s for making tar accoiding to the German method. ... 45
Process for obtaining tar according to tlie Russian metliod . . 46
Black solid pitch -widi a smooth shining surface 49
Naval pitch , 50
J^mp black ibid.
CHAPTER II.
Of the Jluids which serve as an excipient or vehicle to varnish, and
tvhich painters denote l-y the improper name of solvents . . 54
Alcohol. (Rectified spirit of wine) , . . . 57
Composition of it ibid.
Insufficiency of Dutch proof 58
Obsen'ations on proof by gunpowder 59
What ought to be the specific giavity of alcohol destined for
varnish 60
Method of rectifying it ibid.
Ether 62
Its specific gravity compared with that of alcohol 63
Essence of turpentine 65
Observations on the word essence ibid.
Adulterations of it 66
JVIethods of detecting tliem ibid.
Solution of essence in alcohol. Difficulty of mixing essence
with drying oils in tlie preparation of varnish accounted for
on physical principles. , Gy
Ethereous essence of turpentine. Rectified spirit of turpentine 6S
Pirst method of rectifying essence. 69
Second method 70
Specific gravity of.ethereous esgence compared with that of
common essence 71
Essential oil of lavender ibid.
How extracted , ibid,
4
T4EI.E OP CONTENTS. 'StXVM
Adulterations of It, how detected 72
Essential oil of spike "^^
Adulterations of it ibid.
Oil of white poppy seeds, commonly called oil of pinks .... 7^4
Unfounded prejudices respecting the internal use of it .... jbi<3.
It8 physical qualities ']^
Processs for giving •) drying quality to oil of pinks 76
Observations on the use of water in freeing oils from their
greasy qualities ibid.
Process of Wsdn for this purpose 77
Nut oil ibid.
Why pieferred to linseed oil in painting 7S
Linseed oil ibid,
Observations ou the preparation of it ibid.
Methods employed to give to fat oils a drying quality 80
Fir . proc 'ss , ibid.
Second process , 61
Tliiid process 82
Circumstances "which admit tlie use of drying oils in large
doses ibid.
Fourtli process. Its inconveniences S3
Fifth process '. 84
Watin's process for nut oil, w'hich may be applied to linseed
oil S5
Sixth nrocess. Use of snow in communicating a diying qua-
lity to oils 85
Composition of painters' cream 47
Modification of tlie sixth process , 88
IVîéthod of separating a mass of arying oil into parts, the spe-
cific gi-avity of which is different ibid.
Seventh process 89
Use of oxygen gas . - . ' pO
Eighth process 01
Application of oxygenated muriatic acid ibid.
Satisfactory results 93
General observations which confirni the tlieory on the con^er-
sion of fat oils into dj7ing oils 95
XXVm TABLE OF COXTENTS.
Observations on the dr}^ing substances which are fittest to be
employed in the common processes 95
Etfect of garlic on oils 100
Purposes for which drying oil is employed ib:d.
Eesinous drying oil : 101
Drying oil for printers" ink 102
CHAPTER III.
General olservations on varnishes ; with a distrilution of them
into Jive genera, determined ly their nature and state of consist-
ence 104
Cleaning of the word varnish ibid.
Definition of the art of varnishing. . 105
Wlien first introduced into Europe 106
Parts of which the art of the varnishcr is composed 107
Composition. First part ibid.
Application and polishing. Second and third part lOg
Recapitiilation respecting tlie varied nature of resins, and the
necessity of uniting several of them at the same time in the
composition of varnish 110
Division of varnishes into genera and species 112
FiKST Genus. Diying vamiahes made with alcohol. First
species^ No. 1 114
Metliod of preparation applicable to the first four genera. ... 115
Observations on the use of pounded glass .....'•... ibid.
Power of alcohol over resins how far limited 1 16
Theory on the resistarice which even the most soluble resins
oppose to alcohol II7
Second species of varnish of the same genus. No. 2 118
Third species of varnish of tlie ?anie genus destined for the
same articles. No. 3 1 19
Second Genus of varnishes. Alcoholic varnishes less diy-
ing than the former, and having a weaker smeJl 120
First species for cut paper \\T)rks, dres.=iing-boxes, and otlier
small articles of the like kind, I'c. No. 4 ibid.
Second species of the same genus, destined for tl:e same pur-
pojCj No. 5. 121
TABLE OF CONTENTS. Xxix
Third Species of the same genus, for wainscoting, small articles
of furniture, balustrades^ and railing ia the inside of a house.
No. (J .. 122
Particular kind of waxing, which answers the purpose of var-
nishing 123
Composition used for that puxpoic 124
Fourth species of the same genus. Varnish slightly coloured
for violins and other stringed instruments^ and even for
furniture of plum-trea wood, mahogany, and rose- wood.
No. 7 ibid.
Means of giving it more colour ibid.
Fifth species of the same genus, which the turners of St.
Claude employ for boxes made of box- wood, of the roots
of trees, 8cc. No. 8 I2S
Precautions reouired when .solar infusion is employed ibid.
Advantages attending articles turned in the lathe 12(>
Sixth species of the same genus, for giving a gold tint to arti-
cles of brass. No. 9 ibid.
Seventh species of the same genus. Changing varnish, or
varnish destined to change or to modify the colour of those
bodies to which it is applied, No. 10 12^
XJi^es of it ibid.
Varnish employed by the artists of Geneva for giving a gold
colour to die heads of small nails, used for ornamentir.g
watch-cases 123
Eight species of the same genus. Changing varnish whicîi
may be emplo) ed to give a gold colour to watch-cases,
watch-keys, and articles made of brass, No. 11 ibid.
Comparison between varnishes of tlie first and second genera
and those of the third and fourth •. . . . 129
•TiURD Gen'us of varaishes. Varnishes with essence of tur- -
pontine 13d
Colouring parts soluble hi alcohol and insoluble in essence . . 131
Superiority of v?,rnlshes made with eseence to those corn-
posed with alcohol ibid.
First species of variiish for valuiblf' paintings. No. 12 133
Observations on the varnl^hfe? .ipplicd to paintings 134
■SX. TABLE OF CONTENTS,
Methods of preserving and cleaning pictures ". 135
Second species of the same genus, for grinding colours.
No. 13 13S
Third species of the same genus. Varnish proper to be em-
ployed in mixing up colours for gi-ounds, No. 1-1 139
Fourth species of the same genus. Changing varnish of a less
dr)-ing quality than tlie species Nu. 10., and applicable to
metal. No. 15. 140
E.Kplanation of the term changing varnisb, * 141
Process for var/ii\g, vithout confusion, tlie different tints of
changing varnish 142
Fifth species of the same genus. Varnish distinguished by
the name of mordant. No. l6 143
Uses to which mandants of this hind are applied ibid.
Mixtures which are often used for mordants 144
New mordant , ibid.
FouHTH Genus. Copal varnishes made with ether and es-
sence of turpentine' 145
Observations on the nature of this genus compared witli that
of the preceding ibid.
First species. Copal varnish \\'ith etlier. No. 17 14/
Eemarks on ether ibid.
Quaiitity of copal dissolved by etlaer 14S
Second species. Copal varnish witli esseiice of turpentine.
No. 18 149
Observations on this process, which gives a solid varnish ex-
ceedingly beautiful when applied to nietnliic surfaces .... 150
Third species. Copal varnish made witli essence by means of
au iatcrmedlate substance. No., I9 15]
Method of making copal held in solution hi oil of lavender to
pass into essence 152
Fourtli species. Copal varnish by an intermed.Jtc substance
according to a mediod given in tiie Jorrnai de Physique,
No. 20 I5i
Observatloni on this method ibid-
Fll'tîx species. Cop;.d varnish by the m.edium of cafr^phOi and
eiieiulal oil of lavende? destined for article* which require
TABLE OP CONTEN-TS. XXX\
durability, pliableness, and transparency ; such as the var-
nished wire-gauze used in ships instead of gkiss. No. 21. 154^
Observations and experiments in regard to tlie influence -of
intermediate substances, and particularly that of camphor
on the solution of copal in idcohol 15(5
Singular effect of camphor on resins ibid.
Repetition of Mr. Sheldrake's experiments 157
First experiment with essence ibid.
Second experiment with alcohol ibid.
Third experiment, Etfect of camphor in strong doses .... 158
Fourth experiment. Effects produced by the varieties of
copal 150
Fifth experiment. Kind of elasticity given to copal l6Ô
Sixth experiment 16"1
Seventh experiment ibid.
Singular anomalies arising from the particular nature of the
different specimens of copal l63
Description of a furnace destined for the liquefaction of copal
and amber in order to render them more soluble 105
Method of conducting the operation 1(X)
New properties of copal when treated according to the pro-
posed method Ijro
Sixth species. Copal vai'nish with essence of turpentine with-
out any intermediate substance. No, 22. lyi
New experiments and observations on copal iy:i
Object of these experiments and conclusions deduced from "
them 1 S j
Essence better suited than alcohol to the composition of var-
nish isg
Observations on the varieties of copal, and the chemical pro-
perties it exhibits , igi
Fifth Genus. Fat varnishes 1q3
First species. Extracted from Watin's work. No. 23 195
Second species of the same genus, employed in the manfac-
tories of Geneva for watch-cases in imitation of torfeoise-
shell. No. 24 106
Third species. Amber varnish, No, 25 « . jo/
XSXlt TABLE OP COKTENTs^
Vessels employed for tlie liquefiiction of amber . .'". . ...... igB
New preparation of amber to render it fitter for the composi-
tion of varnish 200
Amber varnish with essence of turpentine 203
Fourth species. Fat amber or copal varnish. No. 26' 204
Fifth species of the same genus. Fat varnish of a gold co-
lour. No. 27 206
Sixth species of the same genus. Fat varnish which may serve
as a mordant to gold and at the same time to dark colours,
No. 2S ibid.
Se\enth species of the same genus. Caoutchouc varnish.
No. 29 20r
Another varnish which may belong to this genus, and wi''.ich
is destined for nautical purposes 209
CHAPTER IV.
Gsr.cral ohscrvulkmi and precepts respecting the preparation of var-
nish on a large scale. Description of an alemlic 7t'ifli a lalneum
maricc, the use of ivtù«h prevents all those accidents that fre-
quently, accompany the making of varnish 210
Peculiar qualities which distinguish good varnishes 211
All resins not proper for this preparation 212
Origin of the art of making boxes and toys of papier mâché,
gilt leather, &c 214
Advantage of essence of birpentine as a \ elude in the compo-
sition of certain varnishes 215
Causes which assign certain limits to oils in the preparation of
varnish ibid.
Distinction to be made between the efi'ccts of chemical disso-
lution and those arising from simple solution 21(5
Washing of resins before they are employed in the composi-
tion of varni.:,h , 218
Oa the necessity of a reduction in the number of the formulae 219
Of the choice of the matters 220
Of the respective doses of the dry and liquid substances .... 221
Of the effects of mechanical division on resins which oppose
the i-rep.test resistaiico to solution 223
TABLE OF CONTENTS. XXXÎil
Of the use of pounded glass T7.V . . 7. . . 223
Of clarification 225
Of filtration through cotton 226
Of tlie preparation of varnishes in open vessels, and the pre-
cautions they require 227
Description of an alembic proper for the preparation of var-
nish 230
Method of conducting the operation with this varnish 234
CHAPTER V.
Observations on the influence which the solar light has to render es-
sence of turpentine pr&perfor the solution of copal, so as to com-
pose a durable and colourless varnish ^ 239
Object of these researches founded on the difierence of opi-
nion amCTig chemists and artists in regard to the solubility
of copal in essence 240
Anomalies observed in the same essence in regard to the solu-
bility of copal 242
Particular crystallizations observed in essence exposed to the
sun in close vessels 244
Chemical characters of this salt re-dissolved in water 246
Conclusive experiments in regard to the influence of time and
light on essence to render it fit for the solution of copal . . 250
Conjectures respecting the composition of copal 256
Comparative table showing the addition made to tlie specific
gravity of essence^ and the degrees of the influence exer-
cised by the solar light in the course of a year 2^5
Geaeral consequences and conclusion Q,6g
XXXIV TAELE OF CON'TÊKxi,
PART THE SECOND.
CHAPTER I.
Historical account of the colouring suh s tunc es used in painting, u'ith
a description of the processes employed to extract them, and of
the methods of preparing or modifying them 2/9
Bougival white,, nature of it 280
Cremnitz ^^'hite 281
. Composition of a white to which the author gives the name of
Cremnitz white 285
Spanish white 28d
(îypsum 28/
White of Moudon or of Morat 289
White lead. White oxide of lead by vinegar ibid.
Method of preparing it 29O
Precautions in regard to grinding it 292
Ceruse. Oxide of lead by vinegar ibid.
Mixed with white clay in different doses 2g3
Rouen wJiite 294
AVhite of Troyes. White chalk. Carbonate of lime 295
Inconvenience which attends chalk when not twice washed 296
White of zinc. Sublimated oxide of zinc. Calx of zinc.
Flowers of zinc , 297
StTpposed fault in consequence of its dryness. ............. 2Q9
Method of preparing it ibid.
Azure. Enamel blue. SafFer blue. Saxon blue. Vitreous
oxide of cobalt 300
Method of preparing it ibid.
Smalt or coarse Saxon blue 302
Ultramarine ibid.
Preparation of ultramarine according to Kunckel's method . . 305
Neumann's process 306
Metliod of ascertaining v^-hether ultramarine be adulterated. . 30/
Researches respecting tins mineral colour ..,,., 308
TABLE OF CONTENTS, XXXV
New observations on it by G^iyton de Morveau 30^
Prussian blue. PjTissiate of iron ibrtL
Method of preparing it 3 ià\
Cause of the sfrsenish tint observed in sonàe kinds of Prussian .
"-- ■»' r , '.' '
blue .",.,.,.. I. . . 312 ,
Artificial Saxon blue made with prussiate of u-on ........... 313
Blue verditer 314'.
Pelletiev's process for the preparation of it 31(5 .
Green verditer 31/
Cinnabar. Vermilion, Red sulphurated oxide of mercury . . 3 IS
Naples yellow. Yellow oxide of lead mixed with white oxide
of antimony by nitre 319
Method of preparing it 320
Montpelier yellow. Yellow oxide of lead by the muriatic acid 322
Chaptal's mediod of preparing it . . ibid.
Indigo 324
Easy method of pulverizing it . ; ; . . . ibid.
Of lakes 326
Carmine, method of preparing it .............. 329
Carminated lake. No. 1., preparation of : . . . . ibid.
Another method of preparing carminated lake by extracting
the colouring part from scarlet clotli .....' 332
Rouge for the toilette •....." 333
False carminated lakes in which the colouring part is different
from tliat of cochineal ......'..... 334
Carminated lake extracted from madder. No. 2 ibid.
EiFect of acetite of lead and arseniate of potash'on madder
lake. No. 3 336
Lake from Brasil wood. No. 4 ••..:... ibid.
Another process. No. 5 . . , . , . 33jj7
Keason for preferring carbonate of soda to carbonate of potash, ••
in preparing lakes by chemical decomposition .-...,- 33B
New researches respecting the means of distinguishing real
■ carminated lakes from those of an irifèrlor quality ... ■ .33'9
Comparative table exliibiting the results of these researches ' 340
Oxides of lead. First degree of oxidation. Gray' oxide . . . . 343
Massicot'. Yellow oxide of lead. Second dégree-'ôf oxidafîdH' ^44
C2
yX3«yi TABLE OF CONTENTS.
Minium. Red oxide of lead. Third degree of oxidation .T.. 344
I/itliargeof gold or of silver. Vitreous oxide of lead. Fourth
degree of oxidation 345
Lamp black. Fat soot resulting from the decomposition of
resins and oils by fire 34/
Particular kind of lamp black 348
Beech black. Beech charcoal ibid.
Black from wine lees 34g
Black from burnt peach stones ibid.
Black from burnt vine twigs 350
Ivory black. Bone black ibid.
Of ochres 351
Brown ochre ibid.
Ochre de rue 352
Calcined ochre de rue ibid.
Natural yellow ochres ibid.
Red ochre ibid.
English red. Reddish brown and dark red oxide of iron with-
out raixtnre 354
Method of pulverizing it 355
Prussian red. How prepared 356
Litmus. Method of preparing it ibid.
Orpiment. Yellow sulphurated oxide of arsenic 35/
Considerations on the use of it ibid.
Realgar. Red sulphurated oxide of arsenic 358
Anatto. Charged extract of a colouring fecula ibid.
Bastard saffron. Flowers of cartliamus 360
Spanish vermilion 36l
Red sandal wood. Colouring part soluble in water and in
alcohol, but insoluble in oils 362
Dutch pinks 363
Dutch pink from -woad ibid.
Another kind of Dutch pink 364
Dutch pink from yellow berrries ibid.
Brownish yellow Dutch pink by tlie decomposition of sul-
phate of alumine (alum) 365
TABLE OF CONTENTS. XXxfA
putch pink with Spanish wliite, or with ceruse, preferable
for oil painting ,. 365
Umber earth 3(5/
Green earth of Saxony 308
Green earth of Verona 369
Terra mérita ibid.
Verdigris. Green oxide of copper by vinegar 370
Purification of it. Distilled verdigris. Acetite of copper .. 372
Liquid verdigris for colouring maps 3/5
Sap green ibid.
CHAPTER II.
Philosophical account of the origin of colours, npplied to materiat
colours, simple and compound; ivith a description of the processes
wMch art employs to vary the number and richness of the tints re-
sulting from a mixture of them , . 37/
Idea of Isaac Vossius respecting colours ibid.
Theory of Newton 378
Observations on white and black, which the theory of optics
does not admit as colours 37p
Primitive material colours , , 3S0
Secondary colours ibid.
General view of the etTect produced by the mixture of colour-
ing bodies , SSI
Of virgin tints 38$
Particular characters which render certain coloured bodies
proper for painting 384
Composition of coloms 33/
Black ibid.
Composition of brown applied to tobacco-boxes 388
White -380
Difference between whites destined for distemper and those
reseiTed for varnish and oil painting ibid.
Composition of colours in which ceruse pre4ominates 39I
Light gray ibid.
Means of destroying tlie smell of varnish made with essence ibid,
5
rXXiVlU TABLE OF CON'TENTS.
Pearl gray 3g%
Flaxen gray ibid.
Colour of oak wood SgA
Colour of walnut-tree wood ibid.
Ydlow 395
Pure and modified yellows ibid.
Naples and Montpelier yellow ibid.
Jonquil ibid.
Lemon yellow 396
Observations on the use of orpiment mixed with ceruse .... ibid.
Golden yellpw colour 397
Chamois colour. Buff colour 398
Olive colour ibid.
Blue ibid.
Observations on the use of prussiate of iron and indigo .... 399
Blue made with Saxon blue 401
Green colour and its compounds '. 402
Sea green ibid.
Sea green for distemper ibid.
Sea green for varnish 403
Green colour for doors, shutters, iron or wooden railing, pali'
sades, balustrades, and for all articles exposed to the air ... 404
Compound colours for rooms 405
Compound green ibid.
Green colour for articles exposed to friction and blows, such
as the wheels of carriages, &c 4Q&.
Ked colour for the bodies of carriages, coach-wheels, kc. . . ibid.
Red for buffets 408
Mixed reds ibid.
Bright red ibid.
Crimson. Rose colour 409
"Violet colour ibid.
Chesnut coloiu- ihid.
Precepts in regard to dark colours 410
TABLE OF CONTEXT^. XXxl*
CHAFTER III.
Of the extent which may le given to the use of the turpentine copal
' varnishes Nos. 18. and 22., ly impregnating them ivith various
solid colouring parts, transparent and proper for ans?vering the
purpose of glazing on metalliclaminœ, sinootkor ornamented; for
imitating transparent enamel, nnd for repairing those accidents
if hie h frequent I II happen to enamelled articles 412
Transparent green colour 415
Another green colour 417
Another green colour by composition 413
Blue colour • . v ibid.
Superb liquid blue .-. . . 420
Yellow 42 1
Dark red . .' 422
Violet .' ibid.
Observations on the application of turjxnrtine copal varnish
to brilliant metaliic surfaces ". . 423
Application of copal varnish to the reparation of opake en-
amel 425
Method of making the coloured pastes 426
White paste ' 42/
Black ibid.
Yellow ibid.
Blue ■ 428
Qreen. . ibid.
Red ibid.
Purple ibid.
Brick red ibid.
Chr.mois colour ; ibid.
Violet 429
Pearl gray ibid.
Flaxen gray "........ ibid.
Remarks '. ibid.
On the method of making coloured foil 430
First preparation ■ .' . 43 1
Second preparation ibid.
Blue colour .,'...".,. 433
''-'' : TABLE OP CONTENTS*
.A iiéfhcr blu'e .'. . . i v é ..... . 432
(jieeri. \ ibid.
lied ,, . 433
Violet ibid.
I.ilac 434
r»uby colour ibid.
Hose colouf ibid.
Ponceau. Poppy red. 435
Prune colour and other browTis ibid.
ObseiTations on the application of these colours ibid,
CHAPTER IV.
Precepts respecting the application of varnishes, coloured or not co-
loured, which the artist or araateur ought always to keep in re-
membrance. Of the different kinds of painting. Of varnished
linen and silk 43/
Precepts respecting pulverization 43S
Necessary relation between the nature of varnish and that of
the bodies to which it is to be applied ibid.
Advantages arising from the gi'eat division of colours 440
Metliods of knowing when a colour is properly ground .... 441
Quantity of matter which may be ground at one time 442
Consistence requisite in mixing up colours ibid.
Precautions to be observed when colours are ground in essence 443
Application of the different kinds of varnish to particular pur-
poses 444
Methods employed by painters in tlie application of varnish
on a large scale 445
Reasons for preferring varnish of the third and fourth genera 44S
Method of applying varnish 450
Comp^'ison between the European and Chinese method of
varnishing 451
On the nature of Chinese varnish 45%
Diiierent method of applying the European and Chinese var-
nish 454
How to destroy the smell of vaiTiish 455
Metltod of cleanifig varnish 458
TABLE OF CONTENTl. - /^ ' ''! \ ^^
Method of cleaning clothes stained with oil ^ofê;irs. •C^; • >^'\Q0
How to preserve colours and brashes^ so thh^^iey n^^be2;_\
again fit for use .^^^^/.^^.^ ib|d.
Of oil painting '►■vr^.v-^'461
Oils proper for painting articles exposed to the weather, and
articles kept in apartments. . 402
Precepts in regard to oil painting ihid.
Observations on tlie two kinds of oil panting 4G8
Polishing 46g
Wax cloth or oil cloth 4/2
Common wax clotli or varnished cloth 4/4
Metliod of making the liciuid paste to be appHed to the clodi 475
Fine printed varnished clotlis 477
Comparison between the process employed for these clotlis
and calico printing 4/3
Varnished siik ibid.
Two kinds of it ibid.
Apparatus for preparing it 4/9
Remnants of silk how employed to advantage 4S0
Another kind of varnished silk 482
Covul plaster ibid.
Adulteration of it how detected 484
CHAPTER V.
Of painting in distemper. Sizing. Composition of colours for di^
s temper. General precepts in regard to this Iranch of the art 485
Origin of distemper ibid.
Différent kinds of glue proper for this purpose 486
Glue of the first quality. Fish glue 487
Consistence which glue ought to have for different purposes 488
Glue of the second quality) or that made from glovers' clip- ^
pings and parchment 489
Glue of the tliird quality, or common glue ibid.
Sizing 4Q1
("^ases which require size to be cold or warm 492
General precepts applicable to painting in distemper ibid.
Three kinds of distemper 4(j4
XÎii TABLE OF CONTENTS.
First kind. First example 4Q5
Second example. Painting in milk 49S
Resinous painting in milk 500
Third example. Painting for the fire-places and hearths in
kitchens, &c. Genevese method 501
Fourth example. Distemper for parquets or floors of inlaid
work 503
Fifth example. Red for corridors and halls paved with tiles 504
Œconomical method of reddening new tiles 505
Sixth example. Distemper in badigeon 506
Genevese method of giving a new appearance to the walls of
old edifices 50/
Second kind of distemper. Varnished distemper. Chipolin. . ibid.
Imitation of Chipohn 511
Third kind of distemper. Royal white 513
Simple method of discovering whether chalk or Spanish white
has been substituted in painting for ceruse 515
CHAPTER VI.
Of the instruments necessary in the art of varnishing. Observations
on the use of some of them 51/
Meaning attached to tiie term painter 518
Situation proper for the workshop of tlie varnisher 5I9
Of die laboratory, and instruments necessary for the labour 521
Of tlie different kinds of brushes 524
Report made to tlie committee of chemistry of tlie society at
Gene\ a for the encouragement of the arts on this new trea-
tise on the art '^f preparing varnishes, and of composing the
colours mixed up with them. ByM, Senebier 527
PART THE FIRST,
CONTAINING-
AN ACCOUNT OF THE SUBSTANCES USED IN MAKING
VARNISHES,
AND
THE METHOD OF PREPARING THEM.
TREATISE ON VARNISHES,
PART THE FIRST.
CHAPTER I.
Historical account of the nature and properties of the sul"
stances which form the lasis of varnishes j and of the eX'
ternal qualities by which the lest kinds, may he known.
ASPHALTUM.
AspHALTUM is a bituminous substance, which in some
countries is very abundant. The Peruvians, and in
particular the Egyptians, formed it into a paste, and
filled with it the cavities of those dead bodies which
they were desirous of embalming. They gave to it
also, by the help of certain mixtures, the consistence of
varnish, and dipped in it the cloth which they wrapped
round these bodies after they had been embalmed.
This substance is a kind of mineral pitch, susceptible
of acquiring a certain degree of consistence. The prin-
ciples of its composition appear to be different from
those which distinguish certain artificial kinds of pitch,
resulting from the spontaneous or accidental decompo-
sidon of a vegetable substance of an ir flammable nature.
Asphaltum seems to participate a little in animal matter,
B
s Treatise on varnishes.
It is of a black colour, the tone of which is not uni-
form. Sometimes the surface of the pieces exhibits a
capuchin black, while the interior is darker and glos-
sier. It is employed, under certain circumstances, by
painters in oil-colours', though its application in this
kind of painting has by some been condemned. In
common painting it is admitted into the composition
of black lakes, and mixtures destined for coloured
grounds, and for representing articles of iron : it is,
however, rarely mixed with other substances. When
employed, it is dissolved over a slow fire^vith prepared
cil, until the result is a pretty thick liquid, which, when
a rod has been immersed in it, runs from it as oil would
do, and not at intervals or in separate portions. It may
be readily conceived that this circumstance will depend
on the proper proportions v\'hich must be observed, in
the respective quantities of the two ingredients.
Asphaltum issues in a liquidi form from the bottom
of the lake Asphaltis in Judsea ; and hence the name of
Jew's pitch, -which is given to it. It rises to the sur-
fiice of the water, where it is dried by the combined
action of the sun and of the air.
To be good, it ought to be solid and brittle ; to have
a brilliant surface as if poHshed; and to be almost black.
If fragments of asphaltum, formed into thin laminse,
be held between the eye and the light of a candle, the
colour of them appears to incline to red. When cold
it einits very little smell ; but when inflamed it has a
.strong, penetrating, bituminous odour.
It is often adulterated with pisasphaltum, another kind
of bitum<=n, lees solid, the odour of which holds a meaa
rank between that of pitch and that of bitumen.
BENJAMIN. ô
BENJAMIN.
Benjamin . is a hai'd, dry, brittle, inflammable sub-
stance, of a resinous taste, and which v/hen thrown on
burning coals emits a sweet penetrating odour.
It results froiri .1 resinous sap, which distils by incision
from a kind of hadamier very abundant in some parts
of India ; on the Malabar coast, and particularly in
Cochinchinaj and in the islands of Sumatra, Java, &c.
When this resin is fresh it has the consistence of a
balsam, such as it is seen in turpentine ; it then gradu-
ally thickens, and forms white tears, which are com*
bined with other tears more coloured, either by the im-
pression of the light, or by mixture with some part of
the bark of the tree, or with dust driven abaut by the
winds. This mixture of white tears, which the brown-
ness of the mass renders still more striking, makes the
whole have the appearance of nougat*, containing
portions of peeled almonds ; and hence the name of
amygdaloid given to this benjamin in commerce, to
distinguish it from a more common kind of a fawn-
colour, which is mixed with saw-dust, seeds, and other
impurities.
By sublimation, without any intermediate substance,
and even by simple ebullition in water, benjamin fur-
nishes a salt which assumes the form of snowy flakes,
in consec^uence of the union of small tufts of very ii:^^ht
argentine needles, exceedingly odorous, which to the
taste manifest a remarkable principle of acidity.
* Nov^at is a kind of preparation made in France from
almonds.-^T. »
b2
4 TREATISE ON VARNISHES.
This particular salt, which forms the essential cha-
racter of balsams, is foreign to the composition of var-
nish. Benjamin ought to be chosen with as little colour
as possible ; and if purity be required in the varnish, it
will be proper to employ only the v/hite tears.
Benjamin readily dissolves in alcohol (spirit of wine),
and forms a tincture charged with a reddish colour.
This tincture, under the name of balsamic milk, makes
part of the formidable apparatus of the toilette.
Benjamin, when in this state of extreme division by
means of alcohol, forms a varnish of an agreeable odour,
which retains a considerable degree of tenacity, and
belongs to those kinds which are slightly coloured*.
CAMPHOR.
Camphor is a light vegetable substance, in part friable,
transparent, slightly unctuous, and of a very strong
aromatic odour. It has a bitter and highly acrid taste,
though it at the same time occasions a sensation of cold.
It dissolves entirely and with great facility in alcohol
(rectified spirit of wine). It combines with oils both
fixed and volatile ; it readily inflames and burns even
on water, over which the part liquefied by the heat ex-
tends, in consequence of its great lightness, and form^
a kind of bason, or crater, the circular edge of which,
being cooled by the water, remains solid. As this kind
of circumvallation preserves the centre from immersion,
the camphor continues to burn, even below the level
of the water. The flame is accompanied with a fuligi-
nous smoke.
* See die second kindj No. / , in tlie First Part.
CAMPHOR. 5
ît appeîirs that no certain opinion has yet been formed
in regard to the rank which camphor ought to hold in
the order of vegetable substances. Naturalists consider
ii as a resin ; but most of the chemists class it among
the essential oils. The arguments on both sides seem
tvo rest on a pretty solid foundadon.
In camphor, indeed, we find particular properdes,
which facilitate a comparison, and which indicate, at
the same tini.^, that it participates more in the nature of
essendal oils than in that of resins.
1 St. Like essential oils, it is volatilized at a degree of
heat superior to that of boiling water.
2d. It dissolves entirely in alcohol. It combines with
oils, both fixed and volatile, without disengaging heat
and without leaving any residuum.
3d. When v/ater is added to a spirituous solution of
camphor, the whole of it, the aroma or odorous prin-
ciple excepted, abandons the alcohol and floats on the
surface.
4th. In burning, it disengages a fuliginous smoke,
like essential oils, and leaves no residuum.
5th. Solution of camphor in alcohol gives, by disdl-
lation, a very abundant aromatic principle.
In this respect no resin can be compared to it. Resins
are fixed in the iire ; they do not entirely dissolve in
alcohol ; a solution of them, v/hen mixed with water,
forms a sediment ', they burn more slowly, and leave a
great deal of charcoal.
Camphor then appears to be of an oily nature. It
would form a particular concrete oil, the origin of
which does not seem to be attached* to one kind of
B 3
6 TREATISE ON VARNISHES.
plants, since it is found in vegetable individuals of dif-
ferent families.
The camphor sold in the shops is extracted from a
kind of laurel which grows in great abundance in the
large islands of the East Indies, such as Sumatra, Bor-
neo, Java, Japan, &c. This tree is distinguished by
the name of the camphor laurel. The camphor of the
island of Java is of the lirst quality.
The knowledge v.e have acquired in regard to the
process employed to obtain camphor has been commu-
nicated to us by the Jesuit missionaries*.
The camphor is dispersed over every part of the tree :
it is even often found under the form of small concrete
lartiinœ. The peasants have a simple method of ex-
tracting it. They cut off the young shoots, branches,
and roots of the camphor tree, and, having bruised them,
boil them in v^^ater, taking care to beat the mixture with
a Idnd of broom formed of small twigs. When they ob-
serve that these twigs are covered with a sort of v.hite
jelly, they conclude that the separation of the camphor-
ous matter has been effcdted. They then take the ves-
sel from the fire ; leave the matter at rest for twenty-
four hours ; and at the end of tliat time separate the
camphor, which is found coagulated into one mass.
This mass is composed of small balls, or grains, ren-
dered impure by being mixed with fragments of bark,
wood, and other foreign substances, which ah^ays ac-
company the first process on a large scale. The worI%,-
men, however, have a very simple method of purifying
* Lettres édifiantes et curieuses des Jésuites Miîsionaires a la
Chine, 24ine recueil^ &c.
CAMPHOR. Y
it, by means of sublimation with a sixteenth part of
quicklime : but this purification is very inferior to that •
practised in Europe ; for the Dutch, who have made
this article a considerable branch of commerce, subject
to a new sublim.ation the purified camphor which they
import from India.
This substance readily evaporates, especially when
in contact with the atmosphere. It is even volatilised in
the close boxes in which it is contained. The upper
part of these boxes becomes covered with a beautiful
crystallization, which disappears and reappears accord-
ing as the temperature of the atmosphere is higher or
lower. Some have imagined that the contact of the air
might be prevented by covering the camphor with flax-
seed ; but this method does not answer the intended
purpose. The quantity of camphor thus lost by neglect
cannot be estimated, but it is certainly very great. There
is only one method of effectually preventing this spon-
taneous evaporation, which is, to put the camphor into
wide-mouthed bottles well closed with cork stoppers. •
The use of camphor for vamish is limited : too great
a quantity would render it mealy. It possesses the
property of facilitating the solution of certain resinSj
which are exceedingly refractory to the dissolving action
of their appropriate liquors. Its union with copal is not
easily destroyed : in this combination camphor loses its
volatility, and the copal its hardness and consistence :
the result at length is a small flexible mass, which re-
tains a long time its elasticity. Camphor, however,
when united in proper doses to other resins, gives tough-
ness to the varnish, and prevents it from crr.cking. The
B 4
8 TREATISE ON VARNISHES.
weight of half an ounce or from five-eighths to a pound
of alcohol must not be exceeded. The latter proportion
is that suited to essence of turpentine.
This substance does not admit of any choice. It is
circulated in commerce pure and without any mixture,
and only requires to be carefully preserved.
CAOUTCHOUC, ELASTIC RESIN.
The physical and chemical properties of caoutchouc,
or elastic resin, do not completely justify the latter ap-
pellation. Nothing indeed has less resemblance to a
resin in its chemical properties, since it resists alcohol
(rectified spirit of wane) ; nor is it a gum, since it is not
soluble in water. These considerations are sufficient to
make us admit the denomination of caoutchouc^ which
is given to this substance by the people who inhabit the
banks of the river of the Amazons.
It is extracted, by incision, from a large tree known
under the name of the syringe-tree^ or seringat ; and
v/hich appears to be very abundant in eveiT part of
South x\merica. The Cy^aguas, one of those tribes
who inhabit Popayan, form of the inspissated juice of
this tree a kind of hollow elastic pears, which serve
them as syringes. This circumstance explains the ety-
mology of the generic name given by the Portuguese to
the tree which furnishes the caoutchouc.
Though this substance differs in a great many respects
from the particular properties of resins, it participates
with them in an cKiinent degree in that of being inflam-
Unable. The American tiibes know how to turn this
property to advantage by converting the caoutchouc
CAOUTCHOUC. 9
into a kind of tapers, two feet in length, and of the
size of the finger, the flame of which emits a strong
light, and lasts a long time.
This singular substance when taken from the tree is
fluid. At first it is a white juice, susceptible of inspis-
sation by exposure to the air, and particularly by a pro-
cess peculiar to the inhabitants ot these countries. When
it fias acquired a certain degree of consistence, they
wrap it round wooden or baked earth moulds, and ex-
pose the moulds, covered in this manner, to the impres-
sion of a thick smoke. It is this smoke which commu-
nicates that brown or blackish colour observed in the
caoutchouc imported to us under the form of pears.
A temperature of from 75 to 1 00 degrees of Fahren.
facilitates the elasticity, which is one of the most distin-
guishing characters of this substr»nce ; and indeed it is
the most astonishing when we consider the extent of it.
Attempts have been made to apply this elasticity
to new purposes of the utmost utihty. Som*e have
endeavoured to dissolve caoutchouc in certain liquids
supposed to be fittest for that purpose j but though
various processes have been employed to restore to it its
former elasticity, after a careful evaporation, none of
them has succeeded, except that of its solution in sul-
phuric ether. Macquer is the first chemist who made re-
searches with a view to extend the utility of caoutchouc.
He found that when dissolved in ether it experienced
no modification capable of altering its elastic property.
This ethereous solution poured on water deposits and
extends the substance of the caoutchouc under the form
of a pellicle, which may be easily removed by evapo-
10 TREATISE ON VARNISHES.
ratiiifr the cihsr. The elasticity of this caoutchouc is
astonishing. If this pclhcle be stretched over moulds it is
capabl 3 of assuming every form, and of acquiring that
state of consistence in which it appears after it has been
subjected to this process. By these means it might be
converted into boots and caps impenetrable to v/ater, and
Vv'hich wculd be more pliable than leather. But the
utility of these articles seems to vanish v/hen the ex-
pense attending such processes is considered.
Many chemists, howevsr, have since that time repeated
Macquer's experiments, but without success. Among
this number is Berniard, who found means to charge
with caoutchouc oil of lavender as well as oil of turpen-
tine, and to dissolve it in oil of camphor and in ex-
pressed oils.
I repeated Macquei's experiments with more success,
by suffering the caoutchouc to digest in ether for twenty-
four hours, and then keeping the matrass in the heat of
a balneum maris to evaporate the most subtile part of
the eth::r. The solution of the caoutchouc did not
take place till the ethe% had decreased nearly one half
in volume.
One of the cases to vdiich the great elasticity of
this substance may be applied with the best success,
is to afford relief in diseases of the bladder which re-
quire the use of a catheter. The fabrication of hollow
elastic catheters seems to be one of the most striking
and best contrived objects of the discovery of* caout-
chouc, considered under the view of its utihty to society.
Draftsmen employ it to wipe out stains from paper,
false strokes, and outlines done with a black-lead pencil.
ISINGLASS. 11
Caoutchouc was employed in the composition of the
varnish with which the first balloon launched at Paris
was covered. The constructors of it endeavoured to
unite strength with a certain degree of pliableness, ccn-
didons which appear to be essentially neccessar)- in such
machines 3 but this varnish is very long in drying.
ISINGLASS, FISH GLUE.
Isinglass, fish glue, or ichthyocolla, is extracted from
the air-bladder of a large fish (sturgeon), which emi-
grates from the Black sea into the Danube, and v/hich
is ver)^ abundant in that river from autumn to the month
of January. During the fishing season the fishermen
employ themselves in the preparadon of this substance
on a large scale. They first take out these bladders,
and, having opened them^, remove, by means of weak
lime water, all the viscid matter which adheres to them.
They separate from them also the fine membrane by
which they are covered, and then expose «-hem to the
air to make them experience a commencemient of desic-
cation ; after which they roll around each of them the
membrane separated from it, in order to convert it into
a kind of cord of the size of the finger. This cord is
twisted into the form of a heart v/ith obtuse angles ;
the two ends are brought together, and fastened in that
manner by a small wooden peg, which prevents the se-
paration of the laminrs during 'the rest of the desicca-
tion. These rolls are hung up in the open air to dry.
They have the shape of small handles, and are brought
to us under this form.
When it is necessary to extract the glue, these rolls
4
1*2 TREATISE ON VARNISHES.
are bruissd ; and, being torn into small portions, arc
boiled with a sufficient quantity of water. The mem-
branaceous part, which remains insoluble, soon gives up
its gelatin, or glue, which is separated by straining it
through a piece of linen ; and in this state it forms^ at
most, a 25th part of the whole matter employed for
the decoction.
Fish gelatin (fish glue) is much used for giving a
lustre and stilfness to ribbons and gauzes. It is a kind
of varnish ; ir is the basis of the English court plaster,
the preparation of which is terminated by the applica-
tion of a coating of balsam of Peru.
In the art oi varnishing, it ts employed for defending
cut-paper works, &c. from the attacks of the varnish
applied to them. Without this precaution the varnish
would be imbibed, and form spots.
This gelatin, when baked with a little sugar, consti-
tutes lip-glue. It is employed, on account of its visco-
sity, for clarifying coffee and purifying wines : for the
latter purpose, liowever, albumen or ivhiîe of egg is
preferable, because it is not attended widi the fault of
incorporating with the wine, and of remaining in it in
a state of solution.
COPAL.
Copal is a r::r,inous substance which distils naturally
from a large tree abundant in New Spain. Copal is
produced also in the East Indies; but in that country it
is rarer. It passes gradually from the consistence of oil
to the state of solid resin. The injects, such ar. flies
and ants, inclosed in it sufliciently prove that this mat-.
COPAL. 13
ter has been liquid ; and that it is indebted for its soli-
dity to two causes united : the contact of the air, which
dissipates its volatile principles, and the action of the
solar rays.
Copal, such as exhibited to us in commerce, emits a
strong- odour when burnt. It is hard, sohd, and trans-
parent ; has a shining surface of a faint lemon colour,
but sometimes inclining to orange.
Of all those who, through taste or by profession,
have employed themselves in the preparation of varnish,
no one seems to have observed a very rem.arkable cha-
racter of copal, v/hich is, that it form.s an intermediate
line between the common resins and amber, in regard
to their property of dissolving in spirituous liquors.
Like amber, theii, it exhibits a pardcular substance. It
resembles those? resins most commonly employed in var-
nishes, by suffering itself, under certain circumstances,
to be attacked by oily substances v/hich exercise no
action on amber ; and it approaches the latter by the
resistance it opposes to the action of spirituous liquors,
Avhich readily lay hold of all the real resins.
AVhen destined for the composidon of varnish it
ought to be chosen pure. I have remarked that the
copal which exhibits a very ambcry colour opposes less
resistance tp solution than tlie purest and consequently
the least coloured copal : the cause of this will be-ex-
plained hereafter.
It was first known under the name of gum copal ;
but the phenomena it exhibits in the fire, a,nd the re-
sistance it opposes to the action of water, have induced
naturalists to distinguish it by the appellation of copal
14- TREATISE ON VARNISHES.
resin. This name, however, is as improper as the for-^
mer, because alcohol (spirit of wine) does not exercise
its action on copal with the same energy as it does on
resins. These distinctions, which are more or less cor^
rect, show the necessity of admitting the specific name
of copal, laying aside any expression that might tend
to define its particular nature. The principal cheraical
properties of copal are as follow :
1st, Copal is in part soluble in alcohol, when directly
applied ; that is to say, without any intermediate sub-
stance.
Çd. It is wholly soluble in alcohol, when, bing very
much divided, it is first subjected to the action of a
fluid less aqueous than alcohol, and which becomes a
medium that facilitates its union with it. This effect is
obtained by beginning the solution in essence of la-
vender.
3d. It is wholly soluble in essence of turpentine, and
without any intermediate substance, after the latter has
acquired from the solar light a state of density and a
particular modification, which establish in it a sort of
homogeneity wi;:h the principles of the copal ; or when
the copal has undergone a particular modification from
heat.
4th. It is wholly soluble in sulphuric ether, and with-
out any intermediate substance, when that liquor is
proved by its specific gravity to be in a state of great
purity ; for it must not be imagined that every fluid
called ether is proper for the particular case to which I
here allude.
It is then certain that alcohol cannot be considered as
GUM TRAGACANTH. ---■•.,.: IJ
a vehicle proper for the solution of copal. iThe author
of The Complete Varnisher does not appear to be of the
same opinion, since he introduces copal into several re-
i:ipes for varnish composed with alcohol. I have, hov\^-
ever, ascertained one fact, which proves that the addi-
tion of copal to certain resins contributes to the durabi-
lity and even to the splendour and brilliancy of the var-
nish ; but when this mixture is used the copal ought to
be ground in small quantities on a piece of porphyry,
with strong dosas of resins readily soluble in alcohol.
GUM ADRAGANTH, OR TRAGACANTH.
This gum distils spontaneously, or by incisions, from
a small shrub named tragacanlha, which is very abun-
dant in the Levant, and particularly in the island of
Candia. The gummy sap hardens into long filaments,
or small ribbons, twisted in the form of worms. This
gum, of a colour more or less white, is diy, inodorous,
and has a sweetish insipid taste j a character which be-.
longs to ail gummy juices.
It ought to be chosen pure, white, and transparent :
that which is yellow, black, or mixed wiih foreign bo-
dies, must be rejected.
When put to soak in water it swells up a great deal,
and assumes the consistence of very thick mucilage.
This mucilage is sometimes employed by miniature
painters, when they are desirous of rendering the vel-
lum on Y/hich they paint as smooth as a plate of ivory.
For this purpose, they put the mucilage into a pi :ce of
fine linen, tie it into a knot, and rub it over the vallum.
In painting in distemper a solution of gum tragacanth
is subsdtuted for aqueous solution of gum arable, in
16 Treatise on varnishes.
mixing up colours of a saline nature. This mucilage,
at least, is used with that beautiful liquid blue which
admits into its composition concentrated muriatic acid
(marine acid*). This mucilage has more body than
that of gum arable.
GUM ARABIC.
This gum distils naturally from the fissures in the
bark, and from incisions made in the trunk of the real
Egyptian acacia, which abounds in Egypt, in Arabia,
Senegal, and several places on the coast of Africa. This
gummy juice is found in pieces of different sizes, some-
times round, sometimes angular, and sometimes folded
double. They are of a yellowish-white colour, brittle
and brilliant. They communicate to v/ater in which
they are dissolved a glutinous viscosity, and give it an
insipid taste, but unaccompanied with any smell.
This gum often exhibits a dark amber yellow colour :
it is found even sometimes . reddish, and in globular
fragments. The latter kind is more particularly known
under the name of Senegal gum. The mucilage it pro-
duces is more viscid, and dries with difficulty. The sur-
face of preparations made with this gum often dries ra-
pidly by the contact of the air, while the interior part
assumes a softer consistence than it had before. In ge-
neral, the mucilage resuldng from Senegal gum has not
the same softness as that of gum arable : dry white
gum arable then is, in all cases, preferable.
When it is necessary to employ gum arable in mix-
ing up colours, or to form a coating for the purpose
* See this composition in the Second Part.
GUM ARABIC. GUM LAC. l7
of preventing varnish from p' -netratiiig those articlvis
to wltich it IS iippli-d, it will b-^ proper to select pieces
which have the least colour ; \\-hich are driest, most
friable, and in particular free irom any mixture of
straw, bark, &c.
Mucilage of gum arabic is never so thick as that
produced by gum tragacanth. When the gum is good
and well chosen, it is colourless, and as transparen ' as
water. This mucilage, when a little diluted with
water, forms one of thoce matters which ought to con-
stitute the first class of varnishes, as we shall show in
treating on the division of its compositions. It per-
forms, indeed, in a certain degree, the office of a var-
nish when water colours are employed ; but the appa-
rently vitreous coating which it forms is subject to the
impressions of moisture. It is however used for cover-
ing delicate articles intended to be varnished, such as
cut paper work, &c. This mucilage preserves the
ground and the colours from being attacked by the
varnish.
GUM I.AC, SEED LAC.
This substance, called improperly a gum, is the re-
sult of the industry of a kind of winged and flying ants
found in several parts of India, such as Bengal, the
kingdoms of Pegu and Siam, 8:c.
These ants deposit the resin on the branches of a
kind of jujube, or on reeds and tvv'igs, which the iriha-
bitants take care to plant in the earth, in order that they
may turn to advantage the industry of these insects.'
If the reddish and tuberous covering v/ith which
these a}its surround certain parts of a twig be carefully
c
18 TREATISE ON VARNISHES.
examined, it will be found that each tubercle contains
small cells, or alveoli, nearly similar to those in a honev-
^comb. They crver their cells on the outside with a
thick; r coating than that in the inside, in order to de-
fend from the rain the young generation contained in
them. This substance, the resinous nature of which is
proper for accomplishing the latter object, is of a dark
red or lateritious colour, and is of a tolerable consist-
ence.
Each cell contains a small round, and as it were
moulded, body. This body is of a beautiful red colour,
and when bruised gives a powder as red as cochineal.
These small bodies, which, no doubt, are the em-
bryos of the insect, communicate their .colouring part
to water, and to resinous or oily substances. It is this
matter which gives to gum lac its peculiar colour.
Lac is known in three states. Lac in sticks is that
still attached to the extremities of the small twigs on
which it has been deposited ; seed lac is the same after-
it has been separated from these tv.igs ; and shell lac is
also the same which has been melted and cast into thin
laminse.
I^ac is not a pure resin : it does not di&solve entirely
in alcohol (spirit of wine). There remains an insoluble
matter, which seems to participate in the nature of wax.
Seed lac gives a tough strong varnish, \.hicli is em-
ployed for musical instruments, such as violins, basses,
^c. For this purpose, it may be used in the state in
which it comes from the shops, that is to say, in grains;
but in this state it is deprived of its colouring parts,.,
which the Indians apply to their printed cottons^^so mucL
SHELL LAC. MASTIC. 19
sought after in Europe on account of the fixity and
brightness of their colours. The want of this colouring
part may be supplied by an infusion of anatto, which
increases the beauty of the varnish desdned for musical
instruments.
SHELL LAC.
Shell lac is prepared with that separated from the
twiffs td which it adheres. It is washed in water to
carry off the colouring part ; it is then melted, and
poured on a marble table, over which it is spread out
to be formed into thin laminss : these laminse are then
distinguished by the name of shell lac.
Under this form it becomes one of the principal in-
gredients of sealing wax, which is coloured with ver-
milion to form red wax, or with lamp black to form
black. This sealing wax is also made to have a shining
and speckled appearance by mixing "the shell lac with
small scales of mica or aventurine, or with laminas of
orpiment ; but the latter mixture is noxious, and emits
a bad smell.
MASTIC.
Mastic is a resin ; by which expression is understood
a friable inflammable substance, more or less odorous,
soluble in whole or in part in alcohol (spirit of wine),
and insoluble in water. Such are the chemical charac-
ters by which we are enabled to distinguish substances
whose external appearance is sometimes nearly the same,
though they are very different in regard to their compo-
nent principles.
Masdc is sold in small grains or transparent tears of
c 2
'JO' . TRrATlSE ON VAP-NISHES.
■<\ lemon colour. It distils by incirion, or even without
incision, from the bark of the lentiscus, a tree very
îibund?Jit in the Levant. This resin readily melts over
the fire ; it has a sweet and slightly aromatic smell,
with a weak balsamic savo,ur.
The purest mastic is found in the island of Chio ; but
it is reserved for the. use of the Turkish ladies, w^ho
chew it, as it has the. property of cleaning the teeth,
sÉrengthening the gums, . and rendering the breath
sweet.
The distinction of m.ale and female mastic is void of
foundation. That intended for varnish ought to possess
all . the characters already mentioned. The mastic
brought to us by the way of Marseilles is not always
pu-;e: it is a mixture of bjautiful tears with grains dirtied
and. adulterated bv fragments of the bark of the len-
tiscLi;;. Varnish compositions admit only the purest
mastic, as little coloured and as transparent as possible.
Mastic is often confounded with <rum sandarac : the for-
o
liier, howçver, may be easily known, as it is always in
round tears cf a greenish white colour, while those of
sandarac are long, a little more coloured, and somewhat
y<?riovr. Besides, all uncertainty m^ay be removed by
two very simple tests. Rlasiic readily dissolves in alco-
hol, which exercises a weaker action on sandarac. Mas-
tication, for which this substance is reserved in the
Levant, affords a second means of distinguishing these
two resins: mastic under the teeth becomes pliable, and
may be draw"n out in.the form of a cord, like turpentine
boiled in water; but sandarac separates into small grains,
and has a bitter taste, v/hich is not found iit mustk»
GUM ANIMA. 21
This resin trivas toii:»-hncss to varnish, and sui]ici2nt
hardness to bear polishing. Cgmpositions in wliich k
does not enter are incapable of endiuing that operation.
GUM VNIMA.
There are two kinds of this resin : one found in the
East, which was formerly brought from Ethiopia ; and
that of the West, which comes in particular from
Brasil. The former has a sweeter odour than the çther,
which is more common in commerce.
The best pieces are of a pretty large size : they ap-
pear marbled with white, opake and yellow transpa-
rent veins. This substance has a sweet and agreeable
smell. Externally it often exhibits the same appear-
ance as copal; but it is more brittle, less solid, and melts
more readily over the fire, or while burning emits a
bright flame.
The tree which produces this resinous substance is
known in America under the name of courtaril. It is
found also in Afiica.
Its use in the composition of varnish is very limited.
It forms part of the least dr)'ing alccholic varnishes;
"When treated alone with that licuior it does not unie
into a mass, even though subjected to a balneum
marias ; and it always remains in a pulverulent state.
This residuum, however, vv^hich condnues insoluble
when there is no mixture, dissolves in p?rt in alcohol
when mixed with other resins that are soluble. It com-
municates to A'arnish an agreeable odour, A^hich renders
it proper for being employed on articles belonging to
the toilette. It ought to be chosen new, and exceed-
c J
^2'^- ."''' -ÇREATISE ON VARNISHES.
.TUttglj ^ipure j>»\vhich may be known by the extent of the
trâ|»sp£^mit parts.
GUM ELEMI.
There are two sorts of gum elemi ; one of which comes
from Ethiopia, and the other from America.
That of Ethiopia is the real kind. It is brought to
us by the way of Marseilles in small cylindric frag-
ments, seven or eight inches in length, and nearly two
pounds in weight. It emits a very agreeable odour of
fennel : it is almost entirely soluble in alcohol (spirit of
wine). It has a greenish colour, and is interspersed with
some reddish veins or glands. It has a solid consist-
ence, and yet is susceptible of becoming soft under the
fingers. This sort is enveloped in the leaves of the
palm tree, or of that kind of reed called the Indian
cane. It is believed that this resin distils from a species
of middle-sized wild olive tree.
The gum elemi imported from Brasil and New Spain
is far from exhibiting the same characters. It is brought
to Europe in large, soft, glutinous masses, and becomes
solid only in the course of time. It is yellowish, semi-
transparent, and has a resemblance to gallipot or white
incense. Its smell seems to give reason for suspecting
that the latter substance is mixed with it.
It is believed that the tree which produces it is a kind
of balsam tree, and that it grows to the height of the
beech. In regard to this point naturalists are still di-
vided in their opinions. But whatever may be the
origin of gum elemi, it is not proper, unless pure, for
being introduced into the composition of varnish. The
GUM ELEMI. GAÀIBOG'Jl^ 'J X >'MS
elemi of Ethiopia ought therefore to be pj^?|j?rrë(i:;>o (^
of America, both on account of its consisteH^e, "v^cll
is bt'tter suited to this composition, and of tTi^s^et
smell wliich it communicates to varnished articles. Ba-
sides, it gives to the composition a toughness and dura-
bility, v.'hich it would be in vain to expect f.om that
of America.
GUM GUTT^, GAMBOGE.
This substance forms one of the resinous gums ; but,
as the resinous part predominates, it perhaps may not
be improper to distinguish it by the name of resin. It
is the dried product of a milky juice, extrac:ed by in-
cision from the bark, the trunk, and the uncovered
roots of a large tree, the species of which has mul-
tiplied veiy much in the country of Gamboge, in part
of the kingdom of Siam, and in China. The inhabi-
tants of the country, according to the relation of tra-
vellers, give to this tree the name of carcapi;!!!.
This resin, in the state of desiccation in which it is
imported, is dry, solid and compact, hard, opake and
inflammable, and of a yellow colour inclining a little to
red. Such are its physical quahties. A greater quantity
of it is taken up by alcohol (spirit of wine) than by
water. In both these fluids the insoluble part is preci-
pitated : these are its principal chemical characters :
It gives a very beautiful yellow colour, which ren- V - «
ders it exceedingly proper for water colours. In this
respect it is used for washing and for miniatures. It
possesses a colouring principle, much sought after for
giving a gold colour to the composidons of changing
c 4
24 TREATISE ON VARNISHES.
varnishes. It communicates to them also body and
brilliancy.
This substance is not susceptible of much choice. It
ought to be smooth and brilliant on the fracture. It has
a kind ofvitrcQus appearance. It may be proper here
to observe that it is a violent purgative, and that a very
small dose of it is capable of producing the most irri-
tating effects. This observation is addressed to painters
who iiave the bad practice of v/iping their brushes v.ith
their mouth.
SANDARAC, GUM SANDARAC.
Gum sandarac is extracted from a large kind of ju-
niper, which grows in varm countries, sucli as Italy,
Spain, and in particular Africa. It distils from the tree
naturally, or from incisions made in the trunk during
the hot weather. It exhibits itself under the form or
tears, sometimes elongated, sometimes round, and
sometimes folded together. That most esteemed is in
bright, shining, and transparent tears of a pale yellow
colour. It has a balsamic odour, and its taste is some-
what acrid.
It is called also rcDii.r, because it was the iirst sulv
stance emploved by the antients in the composition of
varnish, to which it gives solidity.
As a resin, it is soluble in alcoliol, in essential and
fixed oils*, but less so than niastic. By this union,
and particularly by that with alcohol and essence oi
* However, when it is necessary toamite it to drying oils, tht:
same process must be employed as that used for the preparntinii «if
ciiv.ber mid copal varnish.
CUM SANDARAC. DRAGON S BLnQD. 2.5
turpentine, it forms a varnish which possesses great
spLndour ; but it is soft, and is easily scratched by the
It-ast friction. The varni.-h, however, may be rend^ -.^d
harder by mixinp- the sandarac with other resinous sub-
Stances, not so dry, such as gum elemi and gum anima.
It is one of the.principal bases of alcoholic varnishes.
If this resin, when in the pulverulent state, be rubbed
over scratched paper, it restores the surface. The paper
may then be Vviitten upon v^'ithout the ink sinking.
Though the exterior or physical characters of san-
darac may be easily distinguished, there are numerous
examples of other substances being fraudulently sub-
stituted in its stead, to the great prejudice of the artists
who employ it, and v» ho apply, in confluence, to fi'ag-
mjnts of copal, processes proper only for sandarac. I
have often been consulted on similar occasions respect-
ing the inactivity of alcohol applied to supposed sanda-
rac. Artists, therefore, before they purchase large quan-
tities of • what is usually sold in the shops under the
name of this substance, ought to trv a small portion
of it, by which means they may save both time and
money ; for it is not possible to trace back these adul-
terations to their source, in" order to be mdemnihcd.
dr-Agon's blood.
DracTon's blood is a dry, fripb^e, imlammable resin,
of a dark red and almost brown colour on the outside.
When in large thin lamin :« it is transparent. It 'las nei-
ther savour nor smell when cold ; but w^hen buj-nt it
emits a balsamic odour.
26 TREATISE ON VARNISHES.
This resin is produced by a tree very common in the
Canaries, in Jamaica, and in the East Indies. This tree,
called the dragon tree, rises to a considerable height :
its trunk is smooth, like that of the palm tree.
There are several kinds of dragon's blood. That
most esteemed comes to us in small masses of the size
of an olive, wrapped up in the leaves of a species of
reed. Some enveloped in this manner is brought from
India: no difference is observed but in the globular
form given to it. In general, the dragon's blood sold
under the globular form, or that of an olive, is of the
fmest quality.
Another kind is of a soft consistence, and requires
some time to become solid. This sort is also of a good
quality, but inferior to the former.
There is even a third kind known in commerce, which
is sold in the form of round cakes. It is of a dull red
or brick colour ; and appears to be a compound of diffe-
rent resins coloured by brickdust, or by Brasil wood, or
with a portion of real dragon's blood. In the fire it
does not inflame, but swells up. This kind is abso-
lutely improper for the composition of varnish.
Real dragon's blood readily unites M-ith alcohol and
with essential and drying oils : it is, however, employed
only for alcoholic varnishes, or those made wdth es*
sences, and particularly in the case when it is required
to make a chanc-incr varnish destined for foil or tinsel,
or for gilt leather.
YELLOW AMBER. 27
AMBER, KARABÉ, YELLOW AMBER.
Amber, generally known under the name oij/cllow
amber and harahe^ is one of those substances on which
a great deal has been written. It has bc-en an object of
the combined researches of mineralogists and chemists.
The results of the chemical analysis of it were well cal-
culated to excite their curiosity, and to induce them to
continue their experiments. 1 he physical and chemical
properties of amber, so different from thote of other
resinous substances, and the places where it v/as found,
indicated, in some measure, its real origiii, and inclined
them to consider it as a particular substance.
It does not, indeed, appear to have a direct afEnity
to any of the pure resins. Copal, though essentially
different, seems to be the only substance that ap-
proaches nearest to the nature of amber, which has no-
thing in common with resinous substances but the pro-
perty of being very inflammable. These were sufficient
motives to induce naturalists to attempt to discover its
origin; but notwithstanding the numerous researches
made on that subject, there are few substances respect-
ing which so much uncertainty prevails. Laying aside,
therefore, all conjectures which have appeared proba-
ble to the different persons who have applied to this
research, we shall confine ourselves to those facts best
estabhshed, and most capable of giving us certain ideas
in regard to its nature.
Some philosophers believed, with Philemon, that
amber originated from the earth, and did not depend on
any particular organization. Some of our philcsc-
28 TREATISE ON VARNISHES.
pliers, at prcsjnt, have revived this idea in regard to the
oiigin of bitumen. Phny the naturalist adopted the
opinion of the Greeks, by assigning to amber a vege-
table origin. He considered it as the resin of the pine
tree liardened by the autumnal cold. In these remote
ages, comparative analyses, being unknown, could not
contribute to rectify tliis idea.
This instability of opinions required direct observa-
tions, or the concurrence of various circumstances;
which fortunately took place under the reign of Fre-
deric William, king of Prussia.
Ducal Prussia, of all the countries with v.-] 'ich we are
acquainted, is that v/hich seems to be most favoured by
nature in regard to mines of amber. This production
afforded considerable exeixise to the national industry
under the reign of that prince, as a strong taste pre-
vailed at that time for ornaments and trinkets made of
amber. 'At that period the resources of cliL'micid ana-
lysis were sufficiently certiiin to inspire confidence in
reg-ard to the result of them. The study of natural
history, the success of which seemed to depend on that
of chemistry, acquired then a consistence which gave
the best hopes of its future advancement. Such was
the state of circumstances which seemed most favour-
able for fixing the opinion of naturalists in regard to
the nature of amber.
Hoffman, a celebrated chemist, required onl)' the in-
vitadon of that prince to emplov himself in researches,
which he had the better opportunity of bringing to a
fortunate conclusion, as he was in the centre of a coun-
try where this substance abounds, and is dug up ircru
YELLOW AMBER. 2"9
a mine." It was of importance to examine the soil,
which exhibits different strata ; but Hoiiman does not
mention their thickness. The first is of sand ; the
second of clay, fifteen or sixteen feet in thickness ; and
the third is composed of trees impregnated with sul-
phurets of iron (martial pyrites), bituminous, and as it
w.-re burnt. These trees have no consistence : some
of them are of a large diameter, and in a state of
pretty good preservation. This stratum of mineralized
wood is not of equal thickness : some travellers make
it to be forty or fifty feet.
Under tins collection of bituminous v/cod is found
a stratum of sulphurets and of sulphate of iron (py-
rites of iron, and vitriol of iron, or green copperas) ;
and it is not uncommon to meet with pieces of amber
still adhering to the lower part of the trunks of the
trees. They appear there under the form of stalactites.
This stratum of sulphurets and sulphate of iron rests
on a bed of coarse sand. This sand is the reser^'oir of
tlie amber, which is often found there in scattered
fragments, but sometimes also in large masses. Under
this bank of sand the argillaceous bank comniLLc^s,
and prevents the amber from penetrating further.
The large fragments of amber have always a pyra-
midal form, which attests its distillation from the
trees above, and removes every doubt in regard to its
vegetable origin. The most conclusive argument, how-
ever, is that deduced from the pieces of amber which
partly penetrate into the sand, and still adhere by their
upper extremity to the maternal stock.
I'hls substance, being at first lir.uid, carried with ir.
4.
so TREATISE ON VARNISHES.
and enveloped difierent insects adhering to the bark of
the tree, and, together with the vegetable mass, must
have been buried by the efFect of one of those grand
revolutions to which our earth has been subjected.
Witli the period of these revolutions we are unac-
quainted, but evident traces of them are still every
wliere visible.
Bernard de Jussieu, the object of whose ruling pas-
sion was the sciences, and who applied to them with
as much success as ardour, has remarked that the in-
sects inclosed in amber do not belong to our continent.
The schistous impressions found in our soil and in the
neighbourhood of Toningen confirm this opinion, by
the kind of plants the type of which they represent.
As the obser\'ations of Hoffman have been fully
confirmed by Neuman and later philosophers, a vege-
table origin may be assigned to amber. It is probable
that the impression of mineral waters, and the action
of different gases developed by the intestine fermenta- -
tion, which must take place in the mass of these bu-
ried vegetables, are the causes of the principal differ-
ences observed between an •"•er and resins, which have
not been exposed to the same circumstances.
However, when it is considered that copal in a cer-
tain degree participates in some of its properties, one'
might almost be induced to believe that the tree which
produces amber is the same as that which furnishes
copal, and which grows only in the torrid zone*.
* If It be considered, on the other hand, that amber, besides the
characters which distinguish it from other resins, possesses a pro-
perty which st?ems to give it an affinity to certain resins or balsam»
YELLOW AMBER. 51
Amber exhibits itself under various appearances. It
is found white and opake, sometimes exceedingly trans-
parent, and of a pale yellow colour; at other times
of a beautiful dark golden colour. ït is described as a
bituminous substance, dry, brittle, and inflammable.
It is hard, and susceptible of a fine polish : it is easily
worked in the lathe, and is then highly brilliant, and
forms beautiful trinkets.
When rubbed on a soft body, or piece of cloth, it
exhibits an electric property, on which account it was
called by the antients clccirum. Its other name, karal-e,
is originally Persian: it signifies the at tractor ofstrcuus^
an effect arising from its electric virtue.
Its specific gravity is very little superior to "that of
pure v/ater. If the v/ater be mixed v. ith a saline body,
or only slightly charged with sulphate of lime (selenite),
as unboiled water often is, or if it be very near the term
of congelation, it becomes equiponderable to amber. It
is, no doubt, owing to one of these circumstances that
we are indebted for the discovery of pieces of amber
carried away by the rolling of the v/aves of the Baltic,
which detach them from the deep mines where they
are uncovered, and convev them to the shores.
If amber be only rubbed, it has no smell ; but if ex-
posed to a strong heat, it emits an odour far from being
that furnish a volatile essential salt, have we not as mr.ch reason to
think that the anibc-r-tree belongs to the lar-ily of the Iculamh'ts,
some of which are tall, and furnish benjamin ? or to those
large trees which give by incision balsam of Peru, a substance
vvhich, as is mcU known, furnishes an acid aiid volatile esseniiiil
sal: ? ,
32 Treatise on varnishes.
disagreeable : when melted over the fire it is in paiT
decomposed, and exhales a strong, disagreeable, bitu-
minous smell.
Some chemists and certain artists, it is said, have
found means to communicate to amber ductility and
permanent elasticity, as well as dilierent colours, and
to make it serve as a covering to various reptiles, with-
out altering its nature, as a forced liquefaction would
do. It is even said that certain miners have been able
to r ender opake amber transparent, by subjecting it to
ch jmical proc .'sses. All this may be true ; but it ap-
pears certcdii ihat the pretended elastic amber was not so.
By the addition of camphor to copal I obtained a
small, fje:>vible, elastic mass, which has retained its
ductility already six months*. Would the case be the
same \^ith amber ? All the attempts hitherto made to
modify its nature have had no other object than
that of enhancing the price of it. No discovery the
sole object of whi::h is avarice, exhibits motives sufn-
ciently noble to induce the philosopher to employ
himself in researches respecting it.
The amber mines are not confined to Ducal Prussia,
or to the Bakic sea, vvhich v/ashes its shores. It is
found in many other countries, such as the march of
Ancona, Sicily, Saxony, Poland, and Sweden. It is
met with in several cantons of France ; but Prussia
has the noble privilege of presenting it in large masses,
and sufiiciently pure to form a very lucrative object to
the national industrv.
■•• I shall enlarge furLker on this subjcQt in the article on copal
vanii.^h. »
YELLOW AMBER. 33
Amber formed into trinkets and various female or-
naments maintained formerly a very important branch
of commerce, the ramifications of which extended to
eveiy part of Europe and to Asia. The use of precious
stones, which acquired, a preference in consequence of
their brilliancy, has very much abridged the advan-
tages of this commerce, which is now confined to
Persia, India, and China.
The art of varnishing, however, has opened to it
another channel of consumption in Europe. It forms
the base of those beautiful varnishes, the splendour
and durability of which have so much contributed to
extend the reputation of the celebrated Martin.
Amber does not unite indiscriminately with all spiri-
tuous liquors, or with all the different oils usually em-
ployed in the composition of varnishes. It would even,
resist fat drying oils, if the preliminary preparations
which convert it into varnish were neglected.
Essential oils exercise very little action on amber ;
and this is the case even with essential oil of lavender,
which some authors suppose in this case to be suffi-
ciently powerful.
Ether, according to experiments which I made,
effected a sort of division of this substance. It swelled
up as cork does when placed on burning coals, and
became pulverulent. But, notv/ithstanding this tumes-
cence, which announces a division of parts, there was
no solution. By evaporating the ether the amber re-
sumes its original form and consistence.
Alcohol (spirit of wine) distilled in a balneum mari£e
over amber detaches a portion of it, which constitutes
JO
34 TREATISE ON VARNISHE5.
essence or tincture of amber, an article veiT much
used in medicine. V\^hen the first pordons of the al-
cohol distilled are re-disdlled several times over the
powder contained in the balneum marise, the tinc-
ture is sufficiently charged to form a kind of var-
nish ; especially if a fourth part of the vehicle be sepa-
rated from the filtered tincture by a new .distillation :
but to succeed in this experiment the alcohol must be
very pure*.
This fact \dll appear directly contrary to the theory,
of Watin, explained at full length in his critical notes
on a work entitled Le Parfait Vernis^eur. " If am-
ber," says he, " were kept a hundred years in a bal-
neum marias under spirit of wine, it would always re-
main the same.'*
After the numerous and continued experiments of
this kind which I made on amber, both in consequence
of my situation, and with a view of rendering my re-
searches applicable to the art of varnishing, I should
not have hesitated to advise the union of amber with
the different resins employed in the composition of var-
nish, vvhen it is intended to give them more body^
had I not found in copal a substance somewhat more
tractable than amber, and which possesses in the same
degree the qualities sought for in the latter f.
* I have no doiibt of the complete solution of amber in tartarized
alcohol, as practised by, Hoffman ; but diis method, which might
be usefiil for certain medical purposes, cannot be employed in tiie
composition of Tarnish of iliis kind. In this process tlie alcohol.and
the amber experience alterations which deprive them of the qua-
lities essential to the nattire of varnish.
f See tlie fust kind of varnish. No. 2j- Part I,
TURPENTINE. Sâ
Àmber destined for the composition of varnish must
be chosen pure, transparent, and without any mixture
of foreign bodies, which render it valuable only to the
collectors of natural curiosities.
TURPENTINE.
Four kinds of resinous juice are denoted by the
name turpentine*, though this denomination seems
properly to belong only to the resinous fluid which
distils from a tree called the turpentine tree, and from
which it takes its name.
Under this denomination indeed are comprehended,
1st, The turpentine of Chio, which on account of its bal-
samic qualities is preferred to every other kind, and par-
ticularly in medicine. 2d, Venice tur £■ tine. Sd, That
of Strasburgh, or the German turpentine. 4th, The
coarse or common turpentine, brought from the south-
ern parts of France.
These kinds of turpentine have physical qualities
common to them all ; but it is observed that they are
variously modified, and produce differences which give
reason to believe that they are not all proper for the
same uses.
Turpentine has a consistence more or less. fluid. It
is viscid and tenacious j has a strong aromiatic smeli in
* In treating of turpentine I shall take a general view of all the
substances of which it formis the basis^ such as pitch, resin, tar,
&:c. I shall follow the order prescribed by the operations to whick
it is subjected, as the best method of giving a detailed and con-
nected history of this substance, which is singularly modified botli
by nature and by particular processes.
D 2
36 TREATISE ON VARNISHES.
different degrees, and a bitter taste more or less acrid.
It is produced by different resinous trees, which exhibit
to the researches pf the naturalist différences in tlieir
particular organization more remarkable than the che-
mist finds in the resinous juice which is obtained from
them.
In many cases this substance is prepared by nature
alons ; but for the most part her efibrts are assisted by
long incisions made in the bark of the trees, and which,
penetrate even to the soft part of the wood. The vis-
cous juice, which flows from these incisions, is con-
veyed into vessels placed at the bottom of the tree, by
means of pieces of ba.rk bent into the form of a gutter.
The product is imm^ediately removed, to prevent its
being exposed to the influence of the air, which would
occasion a change in its consistence. Time, and the
difîerent changes produced in this juice by art, seem to
extend or vary the degree of its utility, as applied to
medicine, to the purposes of navigation, and to the arts.
When this lioj^uid product is left to nature, the air
and the sun exercise on it a speedy acdon. The vola-
tile oily principle is dissipated, and nothing remains
but a tenacious glutinous matter, which at first is called
barras^ and v;hich is sold in the shops under the name
of gallipot or white incense. It is distinguished from
marbled incense by being cleaner and not so dry. But
in whatever state exhibited, either by nature or by art,
industi7 finds means to vary its properties by applying*
it to different uses.
CHIO AND VENICE TURPENTINE. 37
TURPENTINE OF CHIO.
Turpentine of Chio, extracted by incision, or with-
out incision, from a tree known under the name of the
turpentine tree, has a firmer consistence than the other
kinds of turpentine : but in tliis respect it varies. Some-
times it has the hardness of honey ; is viscid and flex-
' ible ; and in this state is transparent. At other times
it is friable, and breaks between the fingers into small
fragments : its colour is then blueish- white, or inclining
to green. It has a strong balsamic odour ; its taste is
acrid and bitter. This kind of turpentine is the rarest
and most esteemed. It may be employed in small
quantities in the least drying kinds of varnish, that is
to say, in those which admit the union of gum elemi,
gum anima, &c.
VENICE TURPENTINE.
The turpentine of Chio, just mentioned, was long
known under the name of Venice turpentine, because
the Venetians, who got into their hands a great part of
the Levant trade, sent to every part of Europe all the
productions of these countries. At present, that di-
stinguished by the name of Venice turpentine is pro-
duced by a kind of larch tree very abundant in the
Apennines, in part of the Alps of the Grisons, 'of
Savoy, and even of the ci-devant Grenoble. It is
fluid, limpid, glutinous, tenacious, and of a consist-
ence between that of oil and that of honey. It has a
yellowish^white colour,, and a strong penetrating yet
agreeable smell, inclining somewhat to that of oranges.
It possesses a more acrid and a bitterer taste than the tur-
D 3
S8 TREATISE ON VARNISHES.
pentine of Chio. This second kind is fit for tiie com-
position of varnish.
TURPENTINE OF STRASBURGH.
The turpentine of Ahv.ce, or of Strasbiirgh, is pro-
duced by a kind of silver fir, with leaves like those of
the yew tree. When fresh it is liquid, and more trans-
parent than that of Venice, but less viscid and tena-
cious. Its smell is verv airreeable, and has more re-
semblance to that of oranges than the smiell of the
Venice turpentine. Jt has nearly the same taste as that
of Chio.
This turpentine, like that of Venice, takes its name
firom the ciiy which carries on with it the greatest trade.
It is extracted fi-om the firs which grow in great abun-
dance in the northern parts of Germany, in Switzer-
land, the ci-devant Lorraine, &c. There are formed
on the bark of these trees vesicles filled with this re-
sinous juice, which the peasants collect by means of a
cornet of tin plate terminating in a very sharp point.
This instrument serves for piercing the vesicles, and
for receiving the juice which fiows from them.
This turpentine also is exceedingly proper for var-
nish ; but it gives less body to the composition than
that of the larch. In general, the addition of turpen-
tine to varnish contributes to give it a great deal of
splendour, but does not render it more durable,
COMMON TURPENTINE.
The fourth kind of turpentine is reserved for less
valuable purposes, and ought not to be employed iu
COMMON TURPENTINE. S9
the composition of varnish. It is ' produced from the
wild pine, and may be obtained either by or without
mcisions. It has a viscous consistence, is white.^ ahnost
opake, and more tenacious than those of Venice and
Strasburgh. It has a stronger smeli than the other
kinds of turpentine, and its taste is acrid., bitter, dis-
agreeable and nauseous. It is a production of the
southern departments of France, where these pines are
found in great abundance. It'is called coarse turpen-
tine and hijon. This turpentine, when it has acquired
consistence by exposure to the air, forms what is called
gallipot.
All the resinous trees above mentioned, of whatever
species, are a source of wealth to human industrv,
which knows how to vary the employment of them,.
On account of their great height, their lightness, and
their pliability, they are exceedingly useful for ship-
building. Their product, after it has experienced cer-
tain modifications, distinguished by particular names,
furnishes different substances which are highly useful
in navigation, in medicine, and in the arts. The same
substance, indeed, gives essence of tuipentine, ethere-
ous essence of turpentine, colophonium, white incense,
resin, white or Burgundy pitch, tar or liquid pitch,
oil of cade, dry black pitch, naval pitch, and hmp
black.
These substances, the exterior characters of which
seem to be so diilerent, and which indeed are applied
to purposes which admit of no comparison, have all
the same origin. They are all produced from turpen-
tine, such as it is formed by nature, or modiLied by the
D 4
40 TREATISE ON VARNISHES.
air, or by the action of chemical processes ; and they
all concur towards the composition of varnish, more or
less valuable or useful. This consideration alone ren-
ders it necessary to give a short description of each, in
order that their nature and properties may be better
known.
ESSENTIAL OIL OF TURPENTINE. ESSENCE OF
TURPENTINE.
Turpentine extracted from the vesicles of the silver
fir, after being mixed with a great deal of water and
subjected to common distillation, gives for result a
-light and highly volatile oil, which is sold in the shops
under the name of essence of turpentine. In Switz-
erland this oil is prepared from the cones of the silver
fir, which are collected for that purpose in the month
of June, a season when they are filled with liquid tur-
pentine. They are cut into slices, and distilled v.ith
water in large alembics. The oil is separated from the
water, which passes over at the same time, by means
of large glass funnels.
This oil is light, colourless, of a penetrating smell,
and has a singular influence on our organs ; for if a
person only touch it, or inspire air impregnated with its
effluvia, the urine acquires a strong smell of violets.
By distillation with water this essence is always cxt
ceedingly clear, limpid, and colourless : when disdlled
without water, even in a strong heat, it is less fluid,
and assumes a lemon colour : it is ako more oily an4
fatter.
WHITE INCENSF.. GALLIPOT, 4*1
COLOPHONIUM.
When turpentine is distilled with water, the solid re-
sinous part, which cannot be volatilized, remains con-
founded with the water of the bath, and constitutes
what is known in the apothecaries* shops under the
name of baked turpentine. It is separated from the
water, and, being left to drain, is again melted before
it is made an article of commerce, in which it is known
by the names of colophonium, arcancon, hrai sec,
poix Grecque,
If the distillation has been effected without water,
the colophonium is of a, darker colour ; it is red, and
often reddish-brown.
This colophonium is very much used, under the
name of arcancon, in the composition of certain kinds
of varnish. For this purpose, that which is most trans-
parent and least coloured ought to be chosen.
WHITE INCENSE. GALLIPOT. BARRAS.
These different denominations express rather the
state of purity and consistence of the resinous sub-
stance furnished by the pine and the silver fir than any
essential difference in its nature.
The name barras expresses the soft resin which ad-
heres to the bark of the tree, and which often contains
fragments of it, as Vv-ell as dust and sand conveyed to
it by the wind. It is sometimes seen resinified by the
;iction of the air and of the sun.
The word gallipot denotes the same substance, but
in a state of purity, in consequence of the care taken
42' Treatise on varnishes.
when it distils to convey it into wooden troughs placed
at the bottom of ths trees, or into pits lined with fat
earth. This matter is viscous.
What is called ivhite iiicense is gallipot resinified, and
become friable by long exposure to the air.
PINE RESIN. RESIN.
A mixture of white incense and barras, exposed to
a heat capable of rendering these substances liquid,
without experiencing any alteration, and poured upon
a kind of mats covered with straw, constitutes, after it
has cooled, what is sold in the shops under the name
of resin.
ANOTHER METHOD OF PREPARING RESIN.
The inhaL>"tants of the mountains of Switzerland are
acquainted with another process for the preparation of
this substance. They collect under sheds the old
ti'unks of resinous trees, with which they surround a
sort of hearth, and kindle a large fire on it. The heat,
by penetrating these trees, melts the resin, which di-
stils slowly into troughs fixed at the extremity of the
trunks, and the flowing of the liquid is facilitated by
the oblique position given to the trees. They then
place over a fire all the different products, and form-
them into cakes, which they sell in the neighbouring
villages. The trunks from which the resin has been
extracted are then split into fire- wood, and serve them
for fuel in the winter.
This resin is purer than that produced by a mixture
of white incense and barras ; and is preferable, when
the fire has not exercised on it too immediate an action»
BURGUNDY AND WHITE PITCH. 4S
White incense and resin are employed in the com-
position of tht common varnish with which dark co-
lours are mixed.
EUP.GUNDY PITCH. WHITE PITCH.
Turpentine extracted from the turpentine tree, from
the larch and the silver fir, is exceedingly pure ; but
that obtained from the pine and fi'om the spruce fir,
picea or epicea, is impure, as well as less fluid, less
balsiiniic, and less transparent. The Burgundy pitch
sold in the shops is either natural or adulterated.
A simple mixture of gallipot and barras, made with-
out heat, is often sold under the name of Burgundy
pitch ; but the mass resulting from this combinadoii
soon becomes fri^la. It has neither the unctuosity,
nor the viscidity, tenacity, or smell w-hich constitute
real white pitch.
The picea or epicea, spruce-fir tree, which produces
the latter, does not contain the resinous juice dissemi-
nated through particular reservoirs, as it is in the
spruce fir, nor under the bark, as in the pine. A white
resinous and pretty thick substance exudes from the
bark, and is collected by the peasants in summer. They
melt it, and, having strained it through a cloth, put it
into barrels. The real Burgundy pitch is prepared ia
this manner.
When the resinous juice is collected too late, and
has become rather too thick, they lessen its consist-
ence by mixing with it, over the fire, a little turpentine
and oil of turpentine. This substance is employed
4
44- TREATISE ON VAP.NI3HES.
only for those common kinds of varnish applied to
ships and boats.
BLACK SOLID PITCH.
Burgundy pitch melted, and mixed, at the time of
its liquefaction, with lamp black, constitutes a black
semi-friable substance, susceptible of melting at a com-
mon temperature, and which is known under the name
of black pitch. Its surface, though smooth, has a
dull appearance.
I must here observe that it ought to be diftinguished
from naval pitch, which has a smooth shining surface:
the latt-ris produced from the pme and the spruce fir,
altered by the action of heat in the preparation of tar.
TAR. LIQUID BLACK PITCH. BRAI GRAS. TARC.
The different «processes hitherto applied to turpen-
tine, or the resin resulting from the desiccation of it,
in order to modify its state and consistence, or to mul-
tiply its uses, have not such an influence over its na-
ture as to occasion any alteration in it, and much less
to produce a partial destruction of it. The degree of
heat employed only gives it a specific liquidity, which
in no m.anner deranges its composition. Even the di-
stillation, which furnishes essence of it, extracts merely
the more subtile and volatile part, which under the in-
fluence of the air and of the sun would have been lost.
But when converted into pitch the case is not the
same. The degree of heat requited for this operation,
being higher, must destroy the vegetable organization,
znà reduce it to charcoal. The resinous substance
GERMAN METHOD OF MAKING TAR. 4^
escapes complete destruction only in consequence of
the fluidity it acquires, and of the water of vegetation
it carries with ]t.
PROCESS FOP. MAKING TAR ACCORDING TO THE
GERMAN METHOD.
Various substances, which in appearance are very
different, furnish tar. Several processes are employed
for obtaining it ; but in whatever manner extracted,
whether from coals, turf, or wood, the results are the
same, as far as relates to the oily product, which is
the principal object. These processes vary according
to the nature of the matters employed.
In some parts of Germany, and particularly in the
duchy of Deux-Ponts, the mountaineers perform this
operation in furnaces of a very simple construction.
They consist of a square chimney, the base of which
is inclined towards one of its lateral parts, and in the
bottom of it is formed an aperture, through which the
product is conveyed to an external reservoir.
This furnace is filled with pieces of old resinous fir,
split, and placed in a vertical position close to each
other. When the furnace is full it is kindled at the
top, and when completely on fire it is covered with
earth, in the same manner as in the process emplo)^d
for burning common charcoal.
The heat being gradually communicated down-
wards, liquefies the resin, v^-hich flows towards the
lower part by the help of the resinous sap and the
water of vegetation, and carries v/ith it the carbona-
ceous parts. It then passes iuto the exterior réservoir.
46 TREATISE ON VAPvNISHES.
where it escapes the action of the heat, and is removed
thence by the workmen and pat nito casks.
; This, still resinous oil is thicker or thinner, according
to the age of the wood employed for the operation.
The older the firs, the more they abound with resin.
When the operation is finished, the charcoal which
has been left Is taken from the furnace. By these
means a supply of this aidcle is obtained for the use of
the mines, and for other purpos s. It is observed that
the sum of the product forms nearly a fourth of the
wood employed when it is very resinous. The char-
coal forms nearly a third.
PROCESS FOR OBTAINING TAR ACCORDING TO TH3
R.USSIAN METHOD.
In Russia this operadon is performed on a larger scale,
and in a more ceconomical manner. The immense fo-
rests with which the vast deserts of that em-oire are
covered, and the distance -of towns and villages, v/hich
lessens so much the consumption, leave to the pur-
chasers of them, when those they have chosen are not
in the neighbourhood of a mine, only one object to
be accomplished, vvhich is that of making tar.
The resinous vrcod is cut into pieces of different
lengths, according to the purposes to which it is to be
applied. Those destined to form the frame- work or
sides of the furnace. A, (Plate /.) are longer. Those
from which the tar is to be extracted are cut into
shorter pieces of equal length. This length, in gene-
ral, is three or four feet*.
* See B, Plate IL which represents a section of tlie furnace.
'^rr^a^nae^ne/Tfyâ (jtj
To front pa (je 46.
"7 /'/y/ ^/ y r ////'// / r>/ ////'^ Of ■////' p/ //f/frf.) //f /lf//j/rr yvv yy/^//r///</ - yo/r:
RUSSIAN METHOD OF MAKING TAR. 47
A circle is traced out on some eminence, as at C,
(^Flate I.) The ground is dug in the form of a fun-
nel, and at the bottom of it is constructed a small con-
duit, D *. The declivity of the ground admits of this
conduit being inclined, to facilitate the flowing of the
■ tar from the centre of the furnace to the exterior re-
servoir Ef.
In consequence of the nature of the ground, the
operation may sometimes be performed with less ex-
pense than is required when it is necessar)^ to surround
the furnace with a kind of wall, A : but on other oc-
casions all the materials are arranged on the outside,
as seen Plate III, In thisjcase the reservoir E is formed
in the ground.
When it is not possible to give to the excavation a
suiFicient depth to contain all the wood destined for this
operation, and to leave at the same tim.e a sufficient de-
clivity for the free escape of the oily product, an ex-
terior wall. A, (^Plate /.) is constructed, and of such a
height above the ground as may be judged necessary.
This wall is composed of the trunks of trees placed
above each otiier in a horizontal direction, and retained
in that position by several posts, F, of a proper length,
fixed obliquely in the ground, and supported by a
number of stays, G, which give great strength to the
whole construction.
When the work is completed, the inside of this
large inverted cone is covered with a stratum of flit
earth, H, (Plate II.) about six inches in thickness, to
* See the section of the furnace^ Plate 11.
f See Plates I. and 11.
4Ô ' TREATISE ON VARNÎSHES.
secure the exterior wall from the effects of the fire.
The pieces of wood, B, cut of equal size, are then
arranged vertically around the inside of the cone,
so as to form concentric circles, until the whole cavity
is filled. In consequence of this symmetric arrangement
the point of contact is interrupted in the centre by the
diameter of the pieces of wood, and a kind of chimney
is formed, which extends from the bottom to the upper
part of the cone. This chimney, which is a continu-
ation of the conduit D, is of great utility, as it affords
a passage to the air. When the cone is hlled, a circu-
lar stratum of shavings is placed over the last stratum
of wood ; and these being kindled, they are afterwards
covered with earth, I, to graduate the combustion, as is
done in the process for making common charcoal.
The resinous matter liquefied by the heat communi-
cated to the interior parts fiows down with the resinous*
sap, which facilitates its escape through the numerous
interstices left between the pieces of wood, and, pro-
ceeding along the conduit D, formed at the bottom of
the cone, is conveyed in the state of tar into the reser-
voir E, from which it is put into casks. By this pro-
cess it undergoes a commencement of decomposidon,
which often renders it very thick, and it carries with it
carbonacepus parts, which communicate to it a black
colour.
The least product of one of these furnaces, the cir-
cumference of which is four Russian fathoms, or nearly
twenty-eight feet, is thirty barrels of tar.
The arrangement of these furnaces is not always the
same. Some give to the heap of wood an oblong form,
\
h
BLACK PITCH. 49
jTVàke it about ten or twelve feet in height, and con-
struct it in such a manner as not to require the support
.of stays. They first erect an outer wall, composed of
trees, in the extremities of which they make deep
notches, and place them horizontally above each other,
those at the sides being joined to those at the ends by
means of the notches, so that in consequence of this
arrangement the whole acquires considerable strength.
The inside is lined with a stratum of \vell wrought clay,
and the bottom terminates in a gutter sufficiently in-
clined to facilitate the escape of the product, which is
conveyed into a reserv^oir dug out in the earth before
the furnace, and lined also Math clay. The pieces of
wood are arranged as in the preceding case ; and a
stratum of shavings being placed over them, they are
covered with a stratum of earth as soon as they are in
a state of complete combustion*.
BLACK SOLID PITCH WITH A SMOOTH SHININC
SURFACE.
Black smooth pitch has often been confounded with
naval pitch ; and these denominations have even been
considered as synonymous. Black pitch is a constant
object of commerce ; but naval pitch is prepared in the
sea ports at the time when it is employed.
Black pitch, which is transported in casks, is of a
darker or lighter colour. It appears to be dry and
friable, but flows and extends itself when exposed to a
mean temperature. It is believed to be a compound of
the m.ore solid part of tar mixed over the fire with
^ See Plate III.
so TTvEATISE ON VARNISHITS.
resin. Black pkch of a good quality, \\hen bitJ-
ken by a sudden stroke, ought to be smooth, pul-
verulent, and exceedingly brilliant on the fracture.
This kind of pitch is that used by locksmiths for var-
nishing articles which they wish to presei-ve from rust,
çuch as locks, latches, and bolts destined for the doors
of cellars, and of other places exposed to moisture.
For this purpose, nothing is necessar)'- but to heat the
article, and to rub over it a piece of this pitch, partly
^vrappcd up in paper, that it may not stick to the hand.
1 he heat of the metal liquefies the pitch ; and as it soon
dries the resinous part that has been applied, the result
is a black, durable, and shining varnish.
NAVAL PITCH.
Naval pitch is a substance which participates with
black pitch in some particular characters, though it
differs from it by the nature of its composition, and
the uses to which it is applied. It consists of a mixture
of black solid pitch, colophonium, and black Hquid
pitch, or tar-) melted together over the fire. The result
is an artificial black pitch, to which is added a new
qiiL-ntity of colophonium, orgallipot, and tallow. This
mixture is very common in sea ports, where it is
known under the name of ]ia\al pitch y and is em-
ployed for paying ships' bottoms before they are
launched. Sulphur is sometimes mixed with this kind
of varnish, to render it stronger and more durable.
LAMP BLACK.
Turpentine dried, and reduced to the state nf dry
resin, and the refuse of all the difeent kinds of resin,
Tim.
ve 30.
tA<
'/?^^r??eyiy ayiy
T rrmtpmi 50
<?u't/f'^/ ay/^Y/y/-/^/''////'// / II/ a /// r/z^/r^- /f'/- ///tf/y//f/, ^/^o
c
LAMP BLACK. ^1^
produce, in the act even of their combustion, a fuli-
ginous substance, or real black pulverulent soot, greasy
to the touch, known under the name of lamp black.
It is much used in painting, and constitutes the colour-
ing part of printers' ink, which is a real oil varnish.
It is manufactured on a large scale in Germany, and
even at Paris. It is collected in a small chamber con-
structed in some place remote from houses, to prevent
the danp-er of fire; This chamber is called sac-à-noir.
Its dimensions are proportioned to the quantity of
the materials destined to be employed, and the con-
struction of it is very simple. It is a kind of square tent,
composed of poles placed in a perpendicular direction,
and lined with canvas, which forms the sides and the
roof. Instead of canvas, sheep skins well stretched
are sometimes employed. When canvas is used, it is
often covered with strong paper pasted over it. No
aperture is left to afford a passage to the smoke, which
rises from the matters in a complete state of ignition.
Iron kettles filled with pitch broken into middle-
sized fragments, or the remains of resin and old liquid
turpentine, arc placed in the middle of this chamber*
When the remains of turpentine are employed, sulphu-
■ rated matches are thrust into the mass. It is then set
, on fire; and when combustion is fully established, the
workman leaves the chamber and shuts the door very
closely. The smoke which rises is accompanied with
a great deal of soot, which adheres to the interior sides
of the chamber. The same operation is repeated till the
sides are sufficiently covered with soot, which is aftcr-
E 2
52 TREATISE ON VARNISHES'.
wards detachLcl by beatinç; with rods on the outside of
the can\'as. The soot is then collected by sweeping it
locrether with a broom.
o
If the fioor is not paved, tb:3 scot often becomes
mixed with dust and dirt, which is separated by put-
ting the lamp black into a vessel half filled w ith water.
The foreign bodies are precipitated to the bottom ; and
the lamp black, which on account of its greasy nature
floats on the water, is removed by means of a skim-
mer : it is then spread out in the air to dry.
Lamp black is of various qualities. When resins only
are employed, the soot which thence results- is dry, and
exceedingly fine ; but when old grease is mixed with
the resins, the quaUty of the black is vei*y inferior. In
this case it is heavy, and of the nature of grease.
This series of processes applied to one substance
shows what may be accomplished by the power of
human industry when its activity is properly sdmulated.
Men have not confined themselves to the apparent re-
sults obtained from direct operations : induced by the
characters of analogy wliich seem to exist between
resins converted into tar, and that substance which natu-
ralists distinguish by the name of ma't/ia, mineral oil
or pilch., and pis.saspkaltum^ they have imagined,
perhaps too readily, that the circumstances w^hich ac-
company those combinations efi'ected in the interior
parts of the earth, or in the lieighbourliood of volca-
noes, ought to have a more uniform influence than
our chemical processes : hence the preference which
painters give to natural bitumen, and in particular to
LAMP BLACK. S3
asphaltum, over resins of that kind which art exhibits
to us disengaged from every earthy principle and every
heterogeneous substance.
This account of the physical and chemical properties
of turpentine, and its different modifications, may to
some perhaps appear too diffuse. To me, however,
it seems to be highly interesting ; because it possesses
the advantage of exhibiting under the same point of
view, and in an order not to be found in any other
author, operations of which a correct idea is not al-
ways formed, and of which the results ought to be
known, not only by those who destine themselves to
the practice of the arts, but by all those whose taste
leads them to study them in detail, and to examine
their different processes.
Besides, there is not one of the substances mention-
ed, in examining the nature of turpendne, which does
not contribute either directly or indirectly to the art of
the vamisher. All of them concur in their 1-dnd to the
formation of particular compositions, the union of
which constitutes the whole of the art here described.
This object alone has appeared of sufficient importance
'to' induce me to subjoin some engravings, which" will
enable the reader to compreliend more clearly the
nature of a process entirely unknown in our part of.
JEurope : for the drawings from which they were ex-
ecuted I acknowledge myself indebted to a learned
foreigner, who had an opportunity t)f seeing the opé-
rations performed.
e3
CHAPTER IT-
Of the Jiuids which serve as an excipient or vehicle to var-r
nish, and ivhick painters denote Inj the improper name of
solrents.
The fluidswhich enter into the composition of varnishes
are few in number, and do not always possess those
qualities which they ought to have. This circumstance
renders it necessary that those who have occasion to use
them should be well acquainted with their chemical pro-
perties, as they all require some prehminary preparations
to render them fit for the purposes to which they arc
applied. This circumstance demands some particular
details, which form the subject of the present chapter.
The liquids employed in the art of varnishing are
alcohol (highly rectified spirit of wine), ether, essence
or oil of turpentine, such as is sold in the shops ; ethere-
ous essence or rectified spirit of turpentine, oil of spike,
and essential oil of lavender.
These liquids are exc-\2edingly light ; they become
volatilized when exposed to a degree of heat equal and
even inferior to that of boiling water. This character
of volatility, which varies according to the particular
nature of each hquid, determines the different degrees
which varniihes exhibit in their drying quality.
Besides these fluids of a volatile nature, the varnisher
employs others more fixed, ard which do not become
volatilized unless v/hen subjected to a degree of heat
greater than that of boiling water, because tliey then
1
FLUIDS EMPLOYED FOR VARNISHES. 3S
experience a commencement of decomposition ; this
temperature is foreign to the manipulations of the var-
nisher. Of this kind are fat or fixed oils, such as oil
of pinks, nut oil, and linseed oil.
The unctuous nature of the latter would oppose a
permanent obstacle to the desiccation of varnish, had
not art discovered means to remove it. These fat oils,
then, must undergo particular preparations, which
give them a drying quality j and when thus modified
they become the most convenient vehicle and excipient
of every kind of varnish destined for covering bodies
exposed to blows, to friction, and to the influence of
the weather.
Several chemists and all artists are accustomed to
consider them as performJpg the office of a solvent in
the preparation of varnish. It is not, however, under
this point of view that we ought to follow their action
on the solid bodies presented to them. Every real sol-
vent changes the form and modifies the nature of the
substance which it lays hold of. The liquid body and
the solid body are not what they were before : their
ph^'sical properties have disappeared under the influence
of the chemical properties. Evaporation makes no
change in the actual result of their union, and a series
of chemical means are necessary to bring them back to
their former state. The denomination of solvent jiiay,
therefore, be happily applied to an acid such as the
nitrous acid (aquafortis), when united to a metal, an
earth, or an alkaline salt ; but this expression k im-
proper when the action of the liquid is confined to a
simple solution, such as that which watçr exercises qïï
E 4 ■ .
56 TREATISE ON VARNISHES.
a' saline body. This action of the water makes no'
change in the state of the salt, or in that of its sub-
stance ; since simple evaporation is sufficient to restore
both of them to their former condition.
The case is the same with alcohol, essential and fat
oils, when applied to resins, balsams, bitumen, &c. :
the result is merely particular solutions. The dissolved
body being reduced to a state of extreme division, by
the effect of solution, deposits itself, with all the ad-
vantages attached to that great division, on the wood,
metal, or stone, and remains there with all its former
qualities. It is more or less electric, and such as it was
before mixture : in a word, it may exhibit all the che-
mical phccnomena, or phecnomena of decomposition,
which it would have produced under its first form.
Varnish, then, is merely the result of simple solu-
tion ; of a mechanical division of a resinous or gummo-
resinous substance, effected by that fluid best suited
to its nature ; in a word, it is not a dissolution*. I
* The French chemists make a distinction bel?vveen the terms
solution and dissolu tinn. Solution is the division of the parts of any
salt in water. Dissolution is the division of a metal in an acid.
These two operations have no resemblance. In the solution of
salts the saline moleculoe are only separated from each otlier j nei-
ther the salt nor water experiences any decomposition, and botli
may be reco\'ered in the same quantity as tliat which they formed
before the operation. Tlie same thing maybe said of the solution
of resins in alcohol or other spirituous liquors. But in the disso-
lution of metals in an acid there is always a decomposition either
of the acid or of the water : the m^etal passes to the state of oxide,
and a gaseous substance is disengaged, so that after the dissolution
none of these substances is in the harae state in A\hidi it was he-.
fore : decomposition and recomposition^ tljerefore.. have taken place.
Tkans,
OF ALCOHOî;. 57-
thought it necessary to give tliis short explanation be-
fore I proceeded to examine the fluids employed in the
composition of varnish,
OF ALCOHOL (RECTIFIED SPIRIT OF WINe).
Alcohol is the product of the distillation of wine. By
this operation it is obtained of different degrees of pu-
rity. The first distillation gives weak alcohol (brandy).
Repeated distillations contribute towards its rectifica-
tion, and at length produce pure alcohol (rectified
spirit of wine).
At the period when the pneumatic chemistry arose-
on the ruins of that, of Stahl, the theory of the com-
position of alcohol had become a kind of problem, the
solution of which was attended with some difficulties.^
One hypothesis was in direct opposition to another.
Several celebrated chemists however discovered, by the
result of their experiments, a new route, which seemed
likely to conduct them to the object of their research.
They varied their processes in a thousand ways ; facts
were accumulated ; and by the help of these materials
they reared the modern theory of chemistry : I here
allude to the pneumatic doctrine. "
The composition of alcohol then ceased to be a pro-
blem. The process of fermentation, which is sponta-
neously established in the juice of the grape, or of
fermentable bodies, modifies in such a manner the prin-
ciples of the sweet and saccharine bodies found in them,
that the result is a Hquor composed of hydrogen (one of
the principles of water) and a little carbon (charcoal).
This liquor, blended with a great deal of the water of
5S TREATISE ON VARNISHES.
vegetation, a colouring part and different salts, which
are foreign to it, constitutes wine. Distillation carries
off the spirituous part mixed with a large quantity of
water; and by repeating this operation the water, which
does not exist in a state of combination, is separated.
The union of hydrogen and carbon in alcohol does not
appear to be free from oxygen (anollier principle of
water); for the inflammable part of alcohol is found
in the oily state, or approaching towards it.
Alcohol is one of those substances which have not a
fixed degree of tenuity or of purity. That commonly
sold in the shops is never pure : it is more or less mixed
with water, which weakens its force. Tasting cannot
serve as a guide in the choice of this article. The case i*
the same with the Dutch proof; an arbitrary method,
which determines the state of purity of alcohol merely
by the slower or speedier disappearance of the crown
of bubbles produced by shalung some of it in a phial.
A^yatin judiciously observes, that weak alcohol, on.
account of the great quantity of water mixed with it,
is improper for the composition of varnish. Setting
out from this principle, he says the best alcohol ought
to be chosen ; but the proof by gunpowder, which he
recommends, has been found to be insufftcient. The
certainty of this kind of proof depends on two circum-»-
stances, which require care and practice. 1st, The
state of the metallic vessel which serves as a receptacle,
2d, The quantity of the gunpowder employed for the
experiment.
If the vessel in which the proof is made be thick, it
acquires a strong heat; and the effect of this heat isj.
1
OF ALCOHOL. 5^
that it evaporates a part of the water contained in the
alcohol : it is this water which moistens the gunpowder,
ïind prevents it from inflaming.
This obstacle, however, might be removed by pla-
cing the vessel in a bason of cold water, and keeping
the bason in a st-je of agitation.
The second inconvenience arising from the quantity
of the gunpowder is such, that it may easily be made to
detonate v/ith weak alcohol, and not to detonate with
?.lcohol of a purer quality- These tricks are well known.'
to merchants. When a large quantity of gunpowder
is employed, and v/hen heaped up in the form of a
pyramid, it happens towards the end of the experiment,
and when the liquor is very much diminished, that the
point of the pyramid soon rises above the surface of the
inflamed liquor. The exterior grains of the gunpowder
speedily lose, by the effect of the heat communicated
to themx, the m.oisture they had imbibed, and detonate
befoKe the whole liquor has evaporated.
The same experiment repeated with alcohol of a
good quality, under which only a few grains of gun-
powder are placed, is not attended with the same suc-
cess, because the small quantity of water deposited by
the alcohol is sufficient to penetrate the small quantity
of gunpowder, which, in consequence of the small
space it occupies, cannot be uncovered before the end
of the inilanimation.
I should not attempt to excite any doubt in regai'd to
these means which are commonlv employed by artists,
to whom it is of importance to be well acquainted with
60 TREATISE ON VARNISHES.
the substances they use, were I not able to substitute
more certain processes in their stead.
There are two methods very efficacious, and which
alone ought to be employed, to determine the choice of
this article : these are the hydrometer, and taldng the
specific gravity, attending at the same time to the tem-
perature, which ought to be from 55 to 60 of Fahren-
heit*.
When the artist finds it necessary to rectify his own
alcohol, it may be obtained very pure by follo\ving
Baume's method. Reserve the first third of the pro-
duct of each distillation ; then unite all these first pro-
ducts, and, having distilled them again, reserve for your
varnish the two first thirds of the product. The re-
mainder may be employed for new distillations, or for
other purposes. None, however, but amateurs or en-
lightened artists will think it worth while to attend to
these minutiae : common artists will not take so much
trouble, notwithstanding the great benefit they would
derive from these operations in the use of resins, a
much larger quantity of which is taken up by pure
alcohol than by alcohol of an inferior quality ; and be-
sides this, the varnish becomes brighter, more durable,
and more drying f.
■* The atitlior here recommends Baume's areometer, an instru-
ment not to be met with by English artists. But they may easily
try themselves, or get some person who has a proper balance to try,
tlie specific gi-avity of the alcohol they use, which ought not to be
<-'reater than 815, water being taken at 1000. Alcohol of tliis
strength mav be had at Apothecaries'-hall.-~TKANS.
f Some artlits, dtsirous of giving to alcohol tliosecpalitles which
OF ALCOHOL. (Si
Alcohol exercises an action on resinous matters
proper for the composition of varnish, only in propor-
tion to its purity. By the word proper is here meant
real resins : for though different treatises on varnish,
and even Macquer in his excellent Dictionary of Che-
mistry, place resinous gums on the same footing a»
resins; in regard to such compositions, it is certain that
they are not proper for those from which a brilliant and
colourless varnish is expected. This error arises, no
doubt, from the false appellations under which artists
were accustomed to denote the greater part of those
matters employed as the basis of varnish. It was thus
that they gave the name of resinous gum, or simply of
gum, to substances purely resinous ; such as gum ani-
ma, gum elemi, gum tacamahaca, gum guttse, Sec.
It is, however, rather as an artist than as a chemist
that I endeavour to set bounds to the action of alcohol ;
because, at present, I consider only those material sub-
stances capable of furnishing to varnish a solid base,
the more or less perfect extension of which over the
body to be varnished constitutes that glazing, which
exalts and heightens, when exposed to the light, the
material colours applied to them.
arc necessary for making vaniish, have applied to it different
agents, such as carbonate of lime (chalk), carbonate of potash
(regetable alkali or potash), with a view to free it from its super-
abundant water. The latter process, recommended by Boerhaave,
separates from it a liquor denser and a little more coloured tlian
the supernatant alcohol ; but die alcohol is a little altered, it is a^
it were oily. Besides, this process, if necessary to be performed
on a grand scale, would be tedious, and more expensive tb.an distU-
Jatioii.
63 TREATISE ON VARNISHES.
Alcohol may be of use also in the art of varnishing^
m consequence oi the property it possesses of bvicoming
charged with certain colouring raat'ers; but these co-
louring parts aiorie w^uid not always constitute varnish:
besides, in regard to tins use, their number is very
small, since it is confined to one species; that is, the
changing varnishes. In a word, if these colouring.
parts , have the property of contributing, in certain
cases, to the splendour of a composition, they add
nothing to its essential principle, that is, its durability.
OE ETEIER.
Ether, like alcohol, is an artificial production. Al-
cohol treated with an equal quantity of sulphuric acid
Coil of vitriol ; that is, sulphur united to oxygen, the
base of pure air,) assumes characters which seem to
assign to it an intermediate place between alcohol itself
and the hghtest essential oils. It divests itself of a
part of its water, a principle which rendered it miscible
with water ; and it acquires, by the operation to which
it has been subjected, new physical and chemical pro-
perties which make it a new agent, exceedingly useful
in certain arts, and pardcularîy in chemistr)'-, where it
h employed in the nicest analytical researches.
During the op'jradon, the alcohol divests itself of a
gmall quantity of carbon (charcoal) and a great deal
01 water, which it exchanges for a nev*' quantity of
oxygen; and the latter cGinmunicates to it characters
y/hich bring it near to the nature of the iigiitest essen-
tial oils.
Ether is exceedingly volatile, has an agreeable odour,.
• OF ETHER. Q$
différent from that of alcohol, and a penetrating savour,
not hot and irritating like that of alcohol. By repeated
shaking, a part of it may be united to water ; but the
rest floats on the surface of the water as pure oil
would do.
Its specific gravity is a sixth less than that of alco-
hoi, which serves as the base of its formation. Its ac-
tion on resins is not so extensive as that of alcohol. A
mixture of the smallest portion of extractive, gum*
my, or mucilaginous matter is capable of weakening
its energy on the resinous part, whatever may be its
quantity. The application of it is not successful but
with pure resins. In this case it becomes an agent very
much superior to alcohol and to ever)-- other fluid.
Copal, the characters of which seem, in some respects,
to be confounded with those of amber and caoutchouc,
known under the name of gum elastic, attest, in this
point of view, the superiority of ether to alcohol.
But this liquor does not always possess that qualitv
requisite to make it answer those purposes for which it
seems most likely to be useful. Ether, in the same
manner as alcohol, has degrees of purity which depend
on the care and intelligence of the chemist who pi-e-
pares it. Among the gases disengaged during the pre-
paration of it, there is one, the sulphurous acid, which
in some measure weakens the power of ether over
copal, Vv^hich requires that this agent should be in a
estate of the greatest purity.
I confine the employment of this volatile liquor to
the composition of copal varnish, and by addition to
that of caoutchouc varnish. It might indeed be applied
64* TREATISE ON VARNISHES. *
to the composition of other kinds but the clearness of
it will always prevent the UoO oi^ it being extended to
common varnishes.
Watin and die artists who preceded him say nothing
of ether; but a chemist of Paris, Cadet the academi-
cian, had an idea, I beKeve, of extending the use of
this liquor to varnish, by taking advantage of the re-
mains of the distillation of ether, from which more may
be formed by adding new^ doses of alcohol. This idea^
however happy it may at first have appeared, was not
favourably received by artists who were most interested
in adoptmg it. The œconomy which might have struck
the chemist in employing this residuum was not suffi-
ciently apparent to the artist. Besides, the labour on
a large scale which requires the use of a very high
temperature, does not agree with the great expansi-
bility of ether, and it would be necessary that artists
should possess something more than common abilities
to foresee the consequences.
I should myself have observed silence in regard to
the use of this liquor, had not a powerful reason in-
duced me to pay attention to the solution of copal, in
order to make a particular varnish, the destination of
which does not occasion much consumption. IJving
in a city celebrated in various points of view, but par-
ticularly for the extent of its manufactory of enamelled
articles, which has been carried to the highest deo-tee
of perfection, it was proper that I should point out the
easiest and speediest means of repairing, in a durable
manner, the various accidents Vvhich befall such articles
when they are out of the v>'orkni'an's hands. The high
' ESSENCE OF TURPENTINE. 65
price of those toys will admit of these accidents being
repaired with a kind of varnish which is indeed expen-
sive, but endowed with all the required qualities, such
as splendour, durability, and readiness of evaporation.
ESSENCE OF TURPENTINE.
Commerce makes us acquainted with a very odorous
oil, highly inflammable, more or less coloured, and of
a greater or less degree of fluidity, which is distin-
guished by the name of essence or oil of turpentine.
The acceptation of the term essence is not the same
to the chemist and the perfumer. According to the
former, this word expresses that part of a mixture or
compound which is susceptible of being separated by
the application of heat. He gives the name of essence
to the sweet volatile part, v/hich he separates by distil-
lation from aromatic substances : hence all the essential
oil, volatilized in the course of the operation, is distin-
guished by the collective name of essential oil or essence.
According to the perfumer, as well as to certain artists,
the term essence denotes the union of one or more es-
sential oils with alcohol (spirit of wine). Thus essence
of lemons, bergamot, lavender, rosemary, &c. is alco-
hol impregnated with the aroma (odorous principle)
and a portion of the essential oil of these fruits, flow-
ers, &c.
It is not under the latter point of view that we ought
to consider essence of turpentine. It is an essential oil
extracted from turpentine by distillation. The lightest
and the least coloured is that which ought to be em-
ployed for varnish.
eô TREATISE ON VARNISHES.
Though this oil is common, it is subject to that spitît
of adulteration which unfortunately is extended to the
simplest articles of commerce. It may be mixed with
common alcohol or fat oils of little value, such as that
of the seeds of the white poppy, knowTi under the
name of oil of pinks. In both these cases the essence'
is altered, and the use of it would be hurtful in the
preparation of varnish. Water united to weak alcohol
(brandy) opposes the solution of resins. Fat oil, though
less dangerous, would render varnish unctuous, glu-
tinous, and difficult to dry. The first kind of adul-
teration may be known by pouring a Kttle of the essence
into a phial filled with water to the neck; placing your
finger on the mouth of the phial, and giving it two or
three shakes. If the essence is pure, it divides itself
into small, bright, limpid globules, which soon resume
their former situation and volume. If it be mixed with
alcohol, its extreme division renders the water milky,
and the volume of the supernatant oil is not the same.
In regard to the adulteration by fat oil, it may be
detected also by the following sure method: Impregnate
the surface of a bit of paper with this essence, and hold
the paper before the fire. Pure essence will evaporate
completely without leaving any traces on the paper, on
which you may afterwards write. If it be mixed with
fat oil, the paper remains transparent, and refuses every
impression of writing.
When alcohol is at hand there is still a speedier
method. Add a few drops of essence to an ounce of
alcohol : if the essence be pure, the alcohol becomes,
charged with it j if mixed with fat oil, the essence passes
ESSENCE OF TURPENTINE, 67
into the alcohol, but the fat oil is precipitated entirely
to the bottom. If you wish it, you may easily ascer-
tain the proportions which have been observed in the
quantity of the two oils.
I shall here give to this essence a chemical character,
which Watin in his work has refused to it. In the
first edition, p. 60, he announces that essence of tur-
pentine does not mix with spirit of wine. He here no
doubt means, that this mixture cannot be made in those
propordons which might be necessary to render it fit
for the preparation of varnish. It is certain that alco-
hol becomes charged with it in relative proportions, ac-
cording to the consistence of the essence. The lighter
it is it takes up the less, and vice versa. The best
alcohol can take up no more than a third of its weight
of common essence, and a seventh or an eighth part
of the lightest.
The same author considers as a disdnguishing cha-
racter of the best essence the difficulty it exhibits in its
union with drying oil, which forms a principal part of
amber and copal varnish. Very often this union is not
complete till five or six minutes after the vessel has
been taken from the fire, notwithstanding the state of
agitation in which the matters have been kept. This
effect depends entirely on the difference in the specific
.gravity of the two oils, and particularly on the state of
.the consistence or inspissation of the drying oil. The
variations which may take place in regard to these two
■ .circumstances produce reladve results. The motion
^xcited in the mixture, by the means of caloric (heat),
opposes in part the union of the lighter essential oil of
s 2
63 TREATISE ON VARNISHES.
furpentiiie: it indeed remains a long time at the surface,
and does not begin to incorporate but in consequence
of the cir^zular motion which is maintained, and when
the action of the greatest heat ceases.
ETHEREOUS ESSENCE OF TURPENTINE. RECTIFIE»
SPIRIT OF TURPENTINE.
If the influence of merited reputation induced the
iunateur of an art never to deviate from an opinion pro-
nounced by an expert master, the progress of the arts
Would be slow, and errors would long enjoy the privi-
lege of misleading the inquisitive genius, who examines
every thing susceptible of improvement. Setting out
from this principle, we might give some importance to
the idea of reprobation which Watin attaches to the
nature of ethereous or light essence. This author an-
nounces that essence can be useftd only for fat var-
nishes, in order to facilitate their extension, and that
ethereous essence has too little body to be applied to
varnishes.
If this author, whose work is held in considerable
esteem, had distributed his compositions for varnish
into classes or genera, according to the different uses
to which certain compositions may be applied, he v/ould
not have emitted so decisive an opinion. Experience,
w^hich produces and improves the arts, has induced m.e
to pe.y little attention to that importance which is gene-
rally attached to the decision of a master. Experience
therefore shall be my guide, because it is by it alone
that our Opinions ought to be regulated. It appear^
to me that the appiicatiou of ethereous essence of tur-
'^ÎTHEREOUS ESSENCE OF TURPENTINE. 69"
pentlne should be confined to the composition of var-
nish for valuable paintings. The proprietors of the
finest collections are continually recommending the use
of it, as it has more body than alcohol.
There are two methods of rectifying essence of tur-
pentine to render it light and colourless, and to give it
a less disagreeable and incommodious smell than com-
mon essence.
First Method.
Pour into a glass retort, capable of containing double
the quantity of matter subjected to experiment, three
parts of common water and two parts of the essence of
turpentine. Place this retort on a sand bath; and hav-
ing adapted to it a receiver five or six times as large,
cement v/ith paste made of flour and water some bands
of paper over the place where the two vessels are
joined. If the receiver is not tubulated, make a small
hole with a pin in the bands of cemented paper, to
leave a free communication between the exterior and
the interior of the receiver : then place over the retort
a dome of baked earth, and maintain the fire in such a
manner as to make the essence and the water boil.
The receiver will become filled with abundance of
vapours, composed of v/ater and ethereous essence,
which will condense the more readily if all the radiating
heat of the furnace be intercepted by a plate of copper,
or piece of board, placed between the furnace and the
receiver. When the mass of oil subjected to experi-
' ment has decreased nearly two thirds, the distillation
must be stopped. Then leive the product at rest, t»
F 3
*J0 ^TREATISE ON VARNISHES.
facilitate the separation of the ethereous oil, which is
afterwards separated from the water, on which it floats,
by means of a glass funnel, the beak of which is
stopped by the finger.
This etheFeous oil is often milky, or merely nebu-
lous, by the interposition of some aqueous parts, from
which it may be separated by a few days* rest. The
essence, thus 'prepared, possesses a great degree of mo-
bility, and is exceedingly limpid. It is only when it ex-
hibits these two characters that it is thought proper for
the composition of varnish.
The second method cannot be employed but by per-
sons very expert in chemical processes, and who therefore
are well acquainted with those precautions which may
be considered as essentially necessary to the success of a
distillation of this kind. It is the process I chiefly fol-
low, being performed without any intermediate sub-
stance.
Second Method.
The apparatus employed in the preceding process
may be used in the present case. I fill the retort tAvo-
thirds with essence; and as the receiver is tubulated, I
content myself with applying to the tubulure a small
square of paper m.oistened with saliva, to afford a free
passage to the incoercible vapours. I graduate the fire
in such a manner as to carry on the distillation very
slowly, until I have obtained a little more than half the
oil contained in the retort,
I separate the product from a very small quantity of
exceedingly acid and reddish water, which passes at the
1
ESSENTIAL OIL OF LAVENDER. ^l
same time as the ethereous essence : by these means the
operation is much shortened.
The oil of turpentine which remains in the retort is
highly coloured, and thicker than the primitive essence.
It may be used for extending fat varnish, or for coarse
oil painting.
The essence, when thus rectified, is lighter than the
essence commonly sold in the shops. The former is to
the latter as 31 to 32 j and the latter is to distilled water
as 32 to 56.
Its specific gravity is somewhat greater than that of
alcohol ; the latter therefore floats on the lightest es-
sence, and essence consequently has more body than
alcohol.
ESSENTIAL OIL OF LAVENDER.
The varnisher has not much occasion to make use of
this oil, which is better known to the enamel] er, be-
cause it has sufficient consistence to prevent the colours
diluted with it from running under the brush.
Besides this advantage, which is not to be found in
oils that are too fluid, it retains a sort of unctuosity,
which prevents the inconvenience of too speedy desic-
cation. It is on account of this quality that it is n\ost
interesting to the varnisher. It is indeed employed in
the composition of mordants, to which it communi-
cates a sufficient degree of unctuosity to give the painter
time to sketch out the design, which the gilder after-
wards fills up.
This essential oil is extracted by distillation from a
certain quantity of the flowers or tops of lavender. The
F 4
72 Treatise on varnishes.
calyx of these flowers contains a great deal of this oil,
which is volatilized in vapour v^ith the water, at thç
temperature of boiHng water, and which is afterwards
separated from the water over which it floats.
Though this process is followed on a pretty large
scale in the southern provinces of France, which seem
to be the true country of aromatic plants, we must not
believe that the essential oil extracted in them is brought
to us in a state of purity. Essence of turpentine, which
is far more common, is always mixed with it ; and it is
by this addition that the distillers maintain among them-
selves a competition which is always to the disadvantage
of the consumer. It is needless, therefore, to point
out the means of detecting an adulteration universally
known, and which it is impossible to prevent. I shall
only describe the principal characters, which may en-
able purchasers to be on their guard against too exces-
sive a degree of sophistication.
The addition of the essence of turpentine ought to
be considered as too strong, when the fluidity of the oU
of lavender approaches too much to that of the essence,
and when the odour of the plant is so concealed by the
latter as to be scarcely perceptible.
Another Idnd of adulteration, as lucrative to the
distiller as it is prejudicial to the essence of lavender,
destined for the composition of varnish and for paint-
ing, is practised by mixing it with fat oil, such as oil
of behen or oil of pinks. I have already detailed the
means of detecting this adulteration in treating of the
essence of turpentine.
ESSENTIAL OIL OF SPIK.E. 73
ESSENTIAL OIL OF SPIKE.
Oil of spike is the result of the distillation, on a
grand scale, of a kind of lavender with larger leaves
than that vv^hich grows in our gardens. This plant is
very common in the ci-devant Languedoc. In regard
to the oil which it furnishes in great abundance, it is
impossible to find it pure in the shops. What is sold
there emits a stronger or weaker smell of turpentine,
in which i-s perceived a slight balsamic odour of the
plant from which it takes its name. Painters are so
fully convinced of the impurity of this oil, that they no
longer use it. The varnisher, w^ho perceives no differ-
ence between this oil and essence of turpentine but in
the price, does not hesitate to supply its place by the
•latter ; and in this he acts wisely.
Distillers on a large scale bargain sometimes with
"their consciences ; and think they act with great deli-
cacy when they make choice of essential oil of spike to
enlarge the quantity of their valuable essential oils ;
such as those of m^yrrh, neroli, mint, kc. They re-
serve the essence of turpentine for oils of less value,
çuch as that of spike when it is required of the first
quality.
A process very common in the South of France is,
to distil essence of turpentine from oft a certain quan-
tity of that plant which is to give the name to the oil
extracted in the course of the operation. By this me-
thod, the odour peculiar to the plant manifests itself
in a more sensible manner than by simple mixture. To
74- TREATISE ON VARNISHES.
be able to discover this adulteration requires consider-
able practice.
This kind of adulteration, however, is not the only
one employed. The addition of alcohol and that of
fat oil is not neglected.
OIL OF WHITE POPPY SEEDS, COMMONLY CALLED
OIL OF PINKS.
The white poppy, the same kind which in the east-
ern regions, such as Natolia, Syria, Persia, and Egypt,
furnishes opium, is very abundant in many of the coun-
tries of Europe.
The oil extracted from its seeds by contusion and
expression, a method applied to almonds, is exceed-
ingly sweet and unctuous. On this account it is em-
ployed by the Orientals for cleansing and softening the
skin. ^
The great use made of it under different forms in
the East, in Bohemia, Poland, and Italy, seems to have
been founded on the opinion entertained of the somni-
ferous virtue of these seeds ; but it has been proved by
a series of excellent observations, that they do not par-
ticipate in this respect in the properties of the plant
which produces them. They afford a sweet oily nou-
rishment ; and this may serve to account for the use
made of them in certain countries by nurses, who mix
.them sometimes in broth, and administer it to their
children to cure the colic.
The accurate knowledge obtained with respect to
these seeds, and the oil they contain, is not older than
the beginning of the last centuiy ; and it is only owing
OIL OF WHITE "POPPY SEEDS. 75
to the advantages which always result from correct ob*
servations and conclusive experiments, that we are in-
debted for the non-execution of the penalties established
by the old police of France against those who mixed
oil of pinks with the oils destined for alimentary con-
sumption. Since that period, this oil, confined en-
tirely to painting, in consequence of the shackles im-
posed on its circulation, has always been sold at a
cheaper rate than olive oil, nut oil, &c. However, to
set bounds to mercantile avarice in regard to mixtures
which might be made of it, government authorized the
addition of a French pint of turpentine to each cask of
this oil, as being allowed to be used only for painting.
This mixture was made at the different offices where
the oil was entered.
Oil of pinks is not extracted from the seeds of the
white poppy alone : those of the black poppy furnish
it also, and it is used in Germany for lamps, for cook-
ing, in salad, &c. In a word, it supplies the place of
olive oil to the lower classes.
Oil of pinks is unctuous : like fat oils, it must not
be used for painting without proper choice, and it re-
quires a preliminary preparation to be rendered drying.
As it has the advantage over other oils of being colom*-
less, it is preferred for delicate kinds of painting.
Though age, in regard to this oil, supersedes the ne-
cessity of previous preparation, and gives it a drying
quality, I shall here indicate the best process for that
purpose.
T6 TREATISE ON VARNISHES.
Pt'oces.'i for giving a dnjing QiLcilitij to Oil of PiiLhs.
Into three pounds of pure water put an ounce of
sulphate of zinc (white vitriol), and mix the whole
with two pounds of oil of pinks. Expose this mixture
in an earthen vessel capable of standing the hre, to â
degree of heat sufficient to maintain it in a slight state
of ebullition. When one-half or two-thirds of the water
has evaporated, pour the whole into a large glass bottle
or jar, and leave it at rest till the oil becomes clear.
Decant the clearest part by means of a glass funnel, the
beak of which is stopped with a piece of cork : when
the separation of the oil from the water is completely
effected, remove the cork stopper, and supply its place
bv the fore finger, which must be applied in such a
manner as to suffer the water to escape, and to retain
only the oil.
Oil of pinks when prepared in this manner be-
comes, after some weeks, exceedingly limpid and co-
lourless.
liemarhs.
Many artists reject every preparation of oil in which
y/ater has been employed as an intermediate substance.
It mav, indeed, be dispensed with when they employ
coloured oils, with which they mix substances that
communicate to them a foreign colour, and which the
jicat applied to them contributes to render still stronger.
The case is not the same xÀÛi oil of pinks : it still re*
raiîis enough of its unctuous quality to impede desicca'-
NUT OIL. 77
tion for sonie time, and it cannot lose this qiuillty but
"by age, or by processes which are not very complex.
In the process here given the oil becomes cliarged with
a little water, by which it acquires a nebulous appear-
ance, and retains it for several weeks. This interposed
water gradually separates itself from it, and at the same
time carries with it a mucilaginous matter, a little
altered ; the complete separation of which adds to the
extreme purity of the oil. Perfect limpidity is the
surest sign of the absence of all its foreign particles. A
slight heat accelerates the clarification of oil prepared
with water.
Watin indicates for linseed oil a process which may
be employed for oil of pinks also ; and which might be
simplified by omitting the calcined talc. Nothing is
necessary but to expose it to the action of the sun,
during the fme weather in summer, in a vessel the.
bottom of which is covered with white lead, or, what
is better, with litharge, inclosed between two pieces of
fine muslin. Exposure to the sun for some months is
sufficient to free the oil from its greasy pardcles, and to
render it perfect»
NUT OIL.
Nut oil is extracted by contusion and expression from
the interior part of the fruit from which it derives its
name. It is well knovrn in consequence of the great
use made of it as an aliment, and in certain arts. The
most common kind, that is to say, the oil extracfed by
the application of a small degree of heat to the paste,
k reserved for lamps ; biit that extracted vvithout the
78 TREATISE ON VARNISHES.
aid of heat forms a wholesome and nutritive seasoning,
which retains an exquisite taste of the fruit.
The burnt taste which this oil acquires, when too
much heat is employed to increase the product, is the
cause of the preference given to oil of olives in cookeiy.
That destined for the arts is generally the most com-
mon. The heat occasioned by the torréfaction it expe-
riences, disposes it in a wonderful manner for the sub-
sequent operations which render it proper for various
uses in painting. It is preferred to linseed oil for every
kind of painting exposed to the injuries of the air, and
particularly to the influence of the sun.
LINSEED OIL.
Of all the fat oils, the one which forms the subject
of this ardcle requires the greatest degree of heat in
the process of its extraction ; and therefore it is always
more or less coloured and thick.
Flax seed contains a small kernel, which would give
an almost colourless oil hke that of pmks, if nothing
were required to extract the oil except contusion and
expression, as is practised for oil of sweet almonds, and
for nut oil of the first quality : but the kernel of flax
seed is inclosed in a small hard covering, which is very
TTiucilao:inous. The mucilage even is so abundant that
it would absorb the greater part of the oil during the
expression, had not experience pointed out the neces-
sity of destroying it by a pretty strong torréfaction.
During this process there arises abundance of aqueous
vapours furnished by the mucilage, which becomes diy,
and which in part is destroyed. When the whitish va-
LINSEED OIL. '*f9
pour is succeeded by a kind of dry and blackish fumes,
the torréfaction is complete, and the paste is then sub-
jected to the press. It may be readily conceived that
the preliminary labour must have an influence on the
principles of the oil, and alter its purity.
The Dutch follow this branch of the arts on a large
scale, and furnish almost the whole of the linseed oil
circulated by commerce in France. They conduct the
process with more skill than the Germans, who carry
the torréfaction of the seed to such a degree as to ren-
der the oil almost red.
This oil is destined for the purposes of painting, and
particularly for the manufacture of floor-cloths ; but to
give it that drying quality which these arts require, it
is subjected to one of the operations described at the
end of this article.
The society* employs other kinds of fat oil, such
as that extracted from the seeds of the beech tree, oil
of olives, of sweet or bitter almonds, of hemp seed,
oil of walnuts, &c. but they ail have a character of
unctuosity, from which it is difficult to free them. I
must, however, except oil of beech seed, so abundant
in the department of Aisne, and those of the ci-devant
Burgundy and Franche- Comté, which is sold there for
common nut oil : and in these countries the, painters
have never made any complaint against it. Besides,
^he high price of these oils, and particuiariy of olive
, oil aiixi oil of almonds, would add to the reason, here
mendoned. Painters and Tarnishers, therefore, adhere
* The Society of Arts^ Agriculture, and Commerce at Geneva.
so TREATISE ON VARNISHES.
to the three kinds of oil here described. Linseed oil
being inferior to nut oil for painting, is reserved for
coarser works.
METHODS EMPLOYED TO GIVE TO FAT OILS A
DRYING QUALITY.
First Process,
Take Nut oil or linseed oil 8 pounds*.
White lead slightly calcined, - - 1
Yellow acetite of lead (sal Saturn!) I of each
also calcined, ----- i i ounce.
Sulphate of zinc (white vitriol"), .
Vitreous oxide of lead (litharge) ] 2 ounces.
A head of garlic or a small onion.
When these matters are pulverized, mix them with
the garlic and oil over a tire capable of maintaining the
oil in a slight state of ebullition : continue it till the oil
ceases to throw up scum, till it assumes a reddish co-
lour, and till the head of garlic becomes brown. A
pelhcle will then be soon formed on the oil ; which in-
dicates that the operation is completed. Take the ves-
sel from the nre, and the pellicle, being precipitated by
rest, v/ill carry with it all the unctuous parts v/hich
* The proportions here gnen, ?ud in all tlie other formulae în
this v.orkj are according to the old French pound. It is necessary,
therefore, to ob-.er\"e that tliis pound is divided mto 16 ounces,
çach ounce into S gros, each gros into 3 deniers, and each denier
into 24 grains. Some further remarks on tliis subject, with a table.
for converting the^e weiglits into corresponding EngUsh denoiui-*
nations^ will be given at tiie end of tliis work. — ^Tkans.
DRYING OILS- 81
rendered the oil fat. When the oil becomes clear, se*
parate it from the deposit, and put it into wide-mouthed
bottles, where it will completely clarify itself in time,
and improve in quality.
Second Process»
Take Vitreous oxide of lead (litharge) 1 -i- ounce*
Sulphate of zinc (white vitriol) 4 of an ounce,
or 3 gros.
Linseed or nut oil 1 6 ounces.
The operation must be conducted as in the preceding
case.
The choice of the oil is not a matter of indifference.
If it be destined for painting articles exposed to the im-
pression of the external air, or for delicate painting, nut
oil or oil of pinks will be requisite. Linseed oil is used
for coarse painting, and that sheltered from the effects
of the rain and of the sun.
A Uttle negligence in the management of the fire has
often an influence on the colour of the oil, to which a
drying quality is communicated : in this case it is not
proper for delicate painting. This inconvenience may
be avoided by tying up the drying matters in a small
bag ; but the dose of the litharge must then be dou-
bled. The bag must be suspended by a piece of pack-
thread fastened to a stick, which is made to rest on the
edge of the vessel in such a manner as to keep the bag
at the distance of an inch from the bottom of the ves-
Bel. A pellicle will be formed, as in the first operation,
but it v.'ill be slower in making its appearance.
G
^
TRr.ATISrr on VAÎt^'I5H£3.
In this process the oxide of lead, v.hcn it is free, and
^/hén it rests on the bottom of the vessel, is in a great
part reduced. Small grains of lead even are often ob-
served in it. • '*
Third Troce-s.
A drying quality may be communicated to oil by
treating in a heat capable of maintaining a slight ebul-
lition linseed or nut oil, to each pound of which is
added three ounces of vitreous oxide of lead (litharge)
reduced to fine powder.
I have known painters who carried the dose of vi-
treous oxide of lead to a fourth part the quantity of
oil employed. This case is reserved in particular for'
baked oils used in painting, where speedy desiccation
and the greatest degree of durability are required. I
have often used drying oil, prepared by extending the
dose of the vitreous o:dde of lead to a fourth part of
the quantity of the oil. The preparation of floor-
cloths, and all painting of large figures or ornaments,
in w^hich argillaceous colours, such as yellow and red
boles, Dutch pink, &c. arc employedj require this kind
dî preparation, that the desiccation may not be too
slow ; but painting for which metallic oxides are used^
such as preparations of lead, copper, &c. require only
the doses before indicated, because these oxides con-
tain a great deal of oxygen (the base of pure ah'), and
the oil by their contact acquires more of a diying'
quality.
Nay, I have painted v/ith unprepared nut oil, tak-
ing the precaution to- add to the pulverized colour \'i-
Î
DRYING OILS. 83
treous oxide of lead (litharge in very fine powder*),
about 3 or 4 ounces for each pound of oil. The paint-
ing, in this case, acquired a body as speedily as if
baked oil had been employed. This method is expe-
ditious ; but it can be practised only with colours which
are not susceptible of being attacked by litharge.
Fourth Process»
Take Nut oil 2 pounds.
Common water 3 pounds.
Sulphate of zinc (white vitriol) 2 ounces.
Mix these matters, and subject them to a slight ebul-
lition till little water remain. Decant the oil, which will
pass over with a small quantity of water, and separate tl^e
latter by means of a funnel. The oil remains nebulous
for some time ; after which it becomes clear, and seems,
to be very little coloured. This method is employed by
some of the English artists, and I have tried it with
success: the oil is rendered somewhat less drying thafi
by the other processes, and is attended with this incon-
venience, that it remains nebulous for a very long time,
even when exposed to the influence of the sun.
* To reduce the vitreous oxide of lead (Iltliarge) to a state of
great division, v.ithout incurring the risk with which dry pulveri-
zation is sometimes attended, I grind the oxide with water ; I Iheu
•spread out the divided matter in an iron shovel, and place it over a
gentle fire. The moisture is soon evaporated, and the remaining
matter requires very little stirring v/heu mixed up. 1 his method
may be applied v/ith great success to painting in ^vhich different
kinds of ocliTie are employed.
Si- /;•■•'■ .l^kÈATÏSE ON VARNISHES,
f'-' >C ' ^/' Fifth Process.
. .-■Take Nut or linseed oil 6 pounds.
Common water 4 pounds.
Sulphate of zinc 1 ounce.-
One head of garlic.
Mix these matters in a large iron or copper pan ;
then place them over the lire, and maintain the mix*
ture in a state oi ebullition during the whole day :
boiling water must from time to time be added, to make
tip tor the loss of that dissipated by evaporation. The
garlic will then assume a brown appearance. Take the
pan from the fire ; and having suffered a deposit to be
formed, decant the oil, which will clarify itself in the
vessels. By this process the dn'ing oil is rendered
somev/hat more coloured : it is reserved for delicate
colom"s.
This method is one of those which require the
utmost attention; and therefore by some it has been
condemned. If the water mixed with the ingredients,
îmd that added in a state of ebullition during the pro-
cess, to supply the loss of that dis:ipated by evapora-
tion, be too abundant, and if tovv'ards the end of the
operation it be not all made to disappear by a careful
evaporation, it will unite itself to tlie drying: oil, and
communicate to it the colour and the coDsistence almost
&[ creaiu. In this case the oil will ciaiify slowly ; there
will even reuKiin an interposed portion, which it wili
DRYING OILS.^ /^n
•r ^x, 7
be difficult to separate. This incoriii^îeriGè'^se^
justify the censure passed by some artfeçs^n";^^
cess. However, when well conducted, if^^a^rds a
very simple method of obtaining oil exceedingly dry-
ing, and much less coloured than that subjected to the'
direct impression of the fire ; but it requires to be kept
for some time.
House-painters, &c. are less interested than portrait-
or landskip-painters, and those who paint decorations,
in the different researches which tend to destroy the
brown or reddish tint, which is one of the characters
of oils rendered drying by the common processes. For
brown or dark colours they employ the oil twenty-four
hours after it has been prepared, reserving that which
clarifies itself by deposition for the more delicate kinds
of painting. This, however, is not sufficient ; be-
cause the least tint communicated to fine colours vi-
sibly alters their tone. Researches, therefore, have
been made to find out for this particular case processes
different from those which we have here described,
without excepting even the last.
Watin indicates one for nut oil, which may be ap-
plied to linseed oil, and even to that made from the
seeds of the white poppy, in case artists should liave
any objection to employ water as an intermediate sub-
stance. This process is attended with complete suc-
cess, and gives a drying oil free from any foreign
colour. I have mentioned it in describing the process
for communicatmg a drying quality to the oil of white
poppy serd. In every case in which sulphate of zinc
(white vitriol) is employed, according to the English
G 3
86 TREATISE ON VARNISHES.
method, without any mixture, it is proper not to cari:y
the- evaporation of the water beyond three-fourths of
the whole.
In describing the preparation of oil of pinks, it has
been seen that water is an intermediate substance pro-
per for keeping the temperature necessary in this ope-
ration at a fixed point, and which is incapable of alter-
ing the principles of the oil by making it undergo a
commencement of decomposition. The well-known
property it possesses of being reduced to a state of va-
pour affords a certain method of avoiding the accumu-
lation of caloric (heat). By varying the process, and
following a contrary course, it may be rendered the
sole cause of the drying quality required to be given
to a fat oil. Water in the state of snow will exhibit
the two conditions essentially necessary to produce this
effect : extreme division of parts and multiplication of
contact between the rnoleculse of the oil and the oxy-
gen gas contained in the snow. It is on this principle
that the following process is founded :
Sixth Process.
When the long continued cold of winter gives to
snow a pretty dry consistence, take any quantity at
pleasure of linseed oil, nut oil, or oil of pinks, and mix
it with snow, kneading the mixture in a bason with a
wooden spatula, or in a mortar with a pestle. Form
it into a solid mass, and place it in an earthen, a glass,
or a porcelain vessel with a large aperture, and cover
the aperture with a cloth to prevent the introduction
of foreign bodies. Expose the vessel in a place acce^
'4
DP.YING OILS. ST
sible to the cold, but sheltered from the influence of
the solar rays. On the return of a milder temperature
the snow will dissolve into water, which will separate
itself from the oil. If the oil has not been exceedingly
clean and pure, the water is found to be charged with,
its impruriues. If the severe temperature continues two
months, as is the case during some winters, the oil
will acquire in a higher degree its drying quality. A
part of the oil retains then a little water, and it forms
a pellicle, which in colour and consistence resembles
that composition known under the name of painters*
cream or butter*.
The oil is decanted from off the water, or it is re-
•inoved with a spoon and put into a bottle. Rest, by
separating the interposed particles of water, is sufficient
to clarify it. This separation may even be accelerated
.by exposing the oil to the heat of a balneum mariae.
" Taiutevs who leav'e long intervals between their periods of
iabour are accustomed to cover the parts they have painted widi
.a preparation v/hich preserves the freshness of tlie colours, and
which they can remove wlmy they resume their work. This pre-
paration, which is as follows, is called painters' cream;
Take Very clear nut oil 3 oimces.
JVIaslic in tears, pulverized, 5 ounce.
Sal Saturui in powder (acetite of lead) ^ of an ounce.
Dissolve the mastic in oil over a gentle fire, and pour the mix-
ture into a marble mortar over the pounded salt of lead j stir it
widi a wooden pestle, and add water in small quantities till the
mutter assume the appearance and consistence of cream, and refuse
to admit more v/ater. I liave found means to introduce /I ounces
inio ihiii cwniposition by whipping it with a bunch of «mall twigs.
G 4
S8 TREATISE ON VARNISHES.
The oil by this simple mixture acquires a drpng
property, and appears as little coloured as it was before
it was subjected to this process. The circumstance,
therefore, of the division of the molecular of the oil,
which multiplies, and facilitates its contact with the
oxygen gas contained in the snow, concurs in an effecr
tual manner to produce the required result — that is to
say, the disappearance of that unctuous and fat state
which is one of the principal distinguishing characters
of fat and essential oils.
Modification of the same Process,
If an oil already rendered drying, by one of the
'preceding operations, be employed in this process with
as few reacting ingredients and as httle heat as possi-
ble, the oil becomes drying in an eminent degree. It
is then very thick, and a part of it is so confounded
with the water that the result is a glutinous and almost
resinous matter, which adheres so much to the inter-
posed liquid that it obstinately retains that form, what-
ever process may be employed to break the union of
the water and the oil. But in treating oil of hemp
seed in this manner, I observed, in the course'^||kp
second operation, the separation of two very distinct
oils ; one of v/hich having a greater specific gravity
than water fell to the bottom of the vessel, while the
other occupied the upper part in such a manner, that
the whole of the liquid produced by the melting of the
snow formed an intermediate stratum between these two
oils,
The first, thai: is to say the heaviest, v/as very little
\
DRYING OILS. . ' 8D ^ ■
coloiu"ed: it was less so than the second';, and even y
than the oil of hemp seed itself was before its" mixture
with the snow. The first stratum of oil formed two
zones, the upper one of which was clear; the other was
opake and of a chamois colour. The latter, which
retained water, was exceedingly thick, and as if resini^
fied. The water which served to separate these two
kinds of oil was nebulous. In general its present state
depends on the greater or less purity of the oil employed,
and on that of the snow.
These two varieties of oil arc highly drying ; and
when kept for a summer, I have found great difficulty
to extract them from the bottles in which they were
preserved.
The heaviest oil, and that found the least coloured,
may be used for the preparauon of paste made with
white lead or Cremnitz white, employed to repair bro-
ken enamel *.
Sevenlh Process.
These attempts lead to another kind of experiment,
more direct, which confirms in a complete manner the
theory respecting the causes of the state of inspissation,
and the drying property which oils acquire by the dif-
ferent processes usual among artists. The results be^
fore detailed induced me to try to discover means pro-
per for shortening the operation, by exposing oil to the
influence of a current of oxygen gas. Though I had
observed in my experiments on essence of turpentine
exposed for a considerable time to the contact of oxy?
* On tliis subject see Part IL
êo
TREATISE ON VARNISHES.
gen gas, often renewed, that this process was not suf-
ficient to facilitate a reciprocal combination, since the
gas filtered through the stratum of oil and the mass of
trater covered by this oil, without adding in a sensible
manner either to its state of inspissation or to its specific
gravity*, I could not see in this first eflect any thing
to prevent similar experiments on fat oils. It was
possible that the chemical difference which existed be-
twe(m the two kinds of oil might conduce to give
new results; and it was also possible that, by direct-
ing on the oil a current, of oxygen gas, accompanied
with caloric, I should be able to destroy that kind of
inactivity Vv^hich the gas exhibited in the experiments
just mentioned.
' With this view I exposed nut oil, inclosed in a very
narrow long tube, to a current of oxygen gas, disen-
gaged from manganese by sulphuric acid. The orifice
of the tube was arranged in such a manner as to pre-
sent a certain resistance to the too speedy dispersion of
the gas which escaped from the mass of oil. The ab-
solute weight of the oil before the experiment was three
ounces. After the disengagement of the gas, which
continued five hours, the oil had experienced no other
change than a slight modification in its colour, v/hich
was become clearer. Its weight was absolutely the
same, and it retained its taste of the fruit.
I exposed the same oil, but ^yilhout success, to a
f.ew mixture, the gaseous disengagement of which con-
fiiiucd eight hours: I then hoped that the mixture* or
* Joivrnal de Fhysifi'dCj .aIjxs et Avril I7i)^-
DRYING OILS. 91
combination of an acid with oxygen would enable me
to add a new process for giving a drying quality to oil
more siîeedily, and for obtaining it colourless.
Eighth Process,
Muriatic acid (marine acid), which of all the mineral
acids produces the least change on oils, exhibited, in
its affinity for oxygen gas, that mean state of com-
bination which seemed likely to answer the purpose I
proposed. I therefore directed into a tube filled with
,oil a current of oxygenated muriatic acid gas, employ-
ing as much care and attention as possible in the
operation. Signs of a combination instantly appeared.
The colour of the oil was altered ; and a brown but
transparent tint soon succeeded to the beautiful lemon
colour which it had retained. Its fluidity and the
odour of the fruit gradually disappeared, to give place
, to those of baked oil. When examined by a balance,
tvv/^enty-four hours after, it weighed 33 grains more.
In this state it impressed on the tongue the savour of
rancid oil, with a slight taste of acid exceedingly dif»
ficult to be perceived. The passage of the oxygenated
îicid gas had condnued six hours.
The same experiment, repeated on the same oil,
-still deprived it of its colour. The rancid odour was
more perceptible, but the weight had increased only
12 grains. The three ounces of oil then announced an
addition of 45 grains, or of 15 grains per ounce.
This oil being exposed to the sun for fi\e days, I
'nixed one part of it with tiiree parts of water. The
mixture, assisted by motion^ formed a very tliick cmuU.
92 TREATISE ON VARNISHES.
sion, which by rest separated into two parts. Thç
supernat2Lnt oil always remained white like an emuU
sion. Exposure to the sun, and afterwards in a bal»
neum marise, did not effect a separation of the inter-
posed water. This is a property peculiar to dr)ing
oils. Time alone overcomes all difficulties.
The water, when drawn off, scarcely produced any
change in blue vegetable tincture. Concentrated liquor
of carbonate of potash (alkali of potash) produced with
it no effervescence.
It was now of importance to make a trial of this
drying oil on delicate colours, such as the aluminous
rose-coloured lakes extracted from Brasil wood. This
colour, mixed up \Aith this oil and spread over a piece
of walnut-tree wood, was five days in dr) 'ng ; on white
wood it required only two days.
The union of white lead with the lake, in order to
form a dark flesh colour, required for walnut-tree wood
only tvv^o days, and for white wood twenty-four hours.
The colours retained their full brilliancy.
These trials might have appeared sufficient to give
conlidence in regard to the employment of this process,
in which a very intimate union is observed between the
eil and that principle which renders it drying in a very
little time by the help of the acid, which serves as a
midium. It is not expen.âve, and oil prepared in this
manner will abi:okiLely be colourless unless when that
of pinks or of v/hite poppy seeds is used. I employed,
jn each of these experiments, tliree ounces of pure pulve-
rized mr.gnesia, and 2-|- ounces of common sulphuric
•acid, diluted with an ounce of waier. I adapted ta-
DRYING OILS^. 93
the retort a small intermediate receiver, placed between
it and the bent tube, which was conveyed to the bot-
tom of the cylinder containing the oil. By these
means the acid emanations, which escaped from the
retort, did not reach to the oil. This operation may
be very well performed in a sand bath.
The continuance of three ounces of nut oil, ex-
tracted without heat, upon four ounces of water satu-
rated in a great part with oxygenated muriatic acid,
did not produce so speedy an effect. Two months
f lapsed before the oil had acquired the odour and con-
sistence peculiar to drying oils. It was exceedingly-
limpid, and its bright lemon colour had become orange.
I shall conclude this article with some general ob-
servations on the process which communicates to fat
oils those qualities by which drying oils are charac-
terized, and on the principles of the theory respecting
Ihem.
General Observai iom.
Eveiy oil is susceptible, without preparation, of com-
posing a colour by its mixture with a colouring body»
-and even of constitutincc a durable varnish with*the
«ame colour. In this particular case, the time necessajy
for the desiccation of such a mixture will always be
proportioned to the nature of the oil employed. The
fattest and the most unctuous will also be the slowest
in drying: there are some which will even require
several years before they attain to the necessary con-
sistence and solidity.
Art has found means to overcome this difficulty by
94 TREATISE ON VARNISHES.
certain mixtures, which modify the principles of the
oils, and render them proper for a speedy renovation of
the strata. It is probable that the mixture of certain
oils with metallic oxides, such as litharge, ceruse,
verditer, &c., the drying effect of which is very speedy,
may have served as a guide to the first person who
made researches in regard to colours. Every discovery
produced by accident remains a long time in the hands
of the author; but new trials soon multiply the results,
and increase the resources of the art. Jealousy, in
matters relating to the arts, views every thing with an
observing eye. It creates particular compositions ; and
hence that variety of formulae which art, in extending
itself, either confirms or rejects.
Roudnc taught, in general, that to free an oil from
Its greasy particles, and to give it a drying quality, no-
thing was necessary but to bring it into contact with
different substances known to be more or less effec-
tual for that purpose, and which, by help of a well
regulated fire, free it from an unctuous matter, the
presence of which would commmiicate to colours a
viscidity which would render the use of them more dis-
agneeable, and even impossible, in consequence of its
slowness to assume a body.
The effect once obtained, the first authors of such
processes would proceed no further. Whether the
oil by this application of certain foreign bodies received
any new principle, or lost one itself, or whether it ex-
perienced only a simple modification in its substance,
was to them of little importance. Satisfied with the
effect, thev gave themselves no trouble about the cause;
DRYING OILS. 95
Their only aim was to render the effect certain, at the
expense even of the colour of the oil, by adhering to
a certain regularity in the execution of the process.
This was the strict result of the experiment.
At present art goes further, by proceeding from the
effect to the cause. This is accomplished by researches
which conduct to theory ; and theory simplifies every
thing by throwing new light on what is already known,
and fixes the great value attached to good descriptions
of the arts.
If we consult experience in regard to the art of
common house-painting, it will be seen that the sub-
stances which best answer the ends proposed in the
preparation of oils are exactly those which contain the
greatest quantity of oxygen (the base of pure air),
and which are the most susceptible of abandoning it in
favour of the oil with which they are in contact. This
is the result of a real elective affinity, determined by
the application of caloric, or by a kind of particular
processes.
This essential condition is perfectly answered by me-
tallic oxides. They resign to the oil the oxygen which
deprives them of their metallic brilliancy, and v/hich
gives them the pulverulent form : this process is a kind
of combustion. The oxide deprived of its oxygen as-
sumes then its first metallic form. This is what is ob-
served in the remaining matter of an oil rendered dry-
ing by litharge. The case is the same when ceruse,
white lead, massicot, salts of lead, &c. are employed.
The direct inliuence of oxygen in the state of gas,
and united to the muriatic acid, is accompanied with
96 TREATISE ON VARNISHES.
the same effects as I have indicated in the eighth pro-
cess : in a word, the metallic salts, the acids of which
are highly charged with oxygen, have the same pro-
perty, but in a degree inferior to pure oxide*.
After all these eifects, which result from the appli-
cation of these first substances to oils, it needs excite
no astonishment that oil exposed to the sun, and parti-
cularly in leaden vessels, according to V/atin's manner,
should in the course of time acquire a dicing property.
The oxygen gas, which forms part of atmospheric air,
soon renders them rancid by the development of an
acid principle. This effect, arising from th', combi-
nation of the oxygen, would be speedier if the mixture
were exposed to a higher temperature than that given
to it by the sun : but in this case the principles of the
oil in a state of decomposition would communicate to
it a colour, which would confine the use of it to com-
mon painting.
If fat oil then be exposed in a leaden vessel in a place
where it has a free communication with the exterior
air, or if a glass vessel in which plates of lead are put
be employed, the oxidation of the lead will be effected
in both these cases by the modifications which the oil
experiences, and which are necessary to render it dry-
ing. The experiment may even be varied. If glass
vessels filled with oil to which a metallic oxide has been
added are exposed to the sun, and if the vessels be-
closely shut, the result will be exactly the same, but
slower. In the latter case, the metallic oxide will ap-
* See the word Oxidcj Part II.
DRYING OILS. ©7
proach its former state by the loss of a part of the oxy-
gen which constituted it an oxide ; and this transition
will take place according to the quantity of the oxygen
liberated and given up to the oil. It is needless to ob-
serve, that a higher temperature than that produced
by the sun would give the same results as the first pro-
cesses here described. These results are always- the
same, but produced sooner or later according to the
nature of the substances employed, and the energy of
the means which constitute the process.
If we consult all the books which treat on house-
paindng, &c. and on the matters employed for th'at
purpose, we are struck with the variety of the for-
mulae, both in regard to the doses of the re-agents and
the method of using them. Some authors recommend
the concurrence of water : but this is rejected by
others, in consequence of the property it possesses of
not being miscible with oils, and of the difficulties it
presents in regard to clarification. The first quality,
however, renders it proper for this use, and it has that
also of acquiring, over the strongest fire, only a deter-
minate degree of heat, because it carries oif in its state
of vapour the excess of caloric ; the accumuladon of
which in the oil, treated t^'ithout this medium, would
not fail to become prejudicial. The process is slower ;
but this slowness is compensated by the state of the
dr^'ing oil, which is colourless, and even pretty limpid,
when the greater part of the water is evaporated to-
wards the end by a gentle heat.
Some ardsts, imitating the author of Le Parfait
Fernisseuî'y inclose their re-agents in a small bag ; and
.»
H
^8 TREATISE ON VARNISHES.
Others, after the ej^ample ofWatin, mix the ingredients
with the oil. The fact is, that all these methods suc-
ceed, and produce a dicing oil very little colom-ed, if
the f/re has been properly managed, and if substances
■which might give to the oil a foreign colotir be kept at
a distance from these mixtures. It will, therefore, be?
proper to employ only metallic oxides, such as ceruse,
•white lead, litharge, and fiowei^s of zinc. Some me-
tallic salts participate to a certain degree in the same
property. Of this kind are the sulphate of zinc and
acetite of lead (white vitriol and salt of lead).
* Watin himself, who seems to have overlooked the
true theory of this operation, does not appear sufficiently
nice in the choice of the matters he employs for free-
ing oils from their greasy particles. He indicates as an
essential substance ombre earth, which in general con-
tains' a bituminous matter, that communicates to oil a
foreign colour. In like manner he prescribes the use
of a kind of stone, pretty rare, called Muscovy talc,
•with the influence of which on oil we are as yet lit-
tle acquainted, and the place of which is supplied in
France by a species of sulphate of lime, very common
at Paris and in the neighbourhood of that city. It is
known to the vulgar under the n^me of wiroir d'ane^
In the preceding formulae I have varied the doses as
well' as the nature of the re-agents. In this respect,
however, there is a sort of rule established in some
measure by a series of practical observations : tliat is,
to extend the quantity to one-eighth of the oil em-
ployed.' This quantity will be sufficient in the ordinary
cases of painting, if the matters used are all of the-
DRYING OILS. 99
same energy ; that is to say, if they are all capable of
furnishing during the operation the same quantity of
acting principle — oxygen. I made a point of abstaining
from substances whose influence, in this point of view,
did not appear to be fully proved, and from those
which would communicate to oil a foreign colour : in
a word, the formulas given in this work have all been
proved by experiment.
The process most common among artists who are
desirous of freeing an oil from its greasy principles,
consists in communicating to it, before they add the
drying ingredients, a degree of heat nearly equal to
that which produces ebullition. This method would
be attended with inconvenience if the whole matter
were abruptly mixed, and especially if the vessel were
not of a sufficient size to obviate the effects of the
swelling of the oil. Ceruse and acetite of lead (salt of
lead), sulphates of lime (selenites), and ombre earths,
contain moisture, which expands and distends the oil.
This tumefaction is so speedy that there is always some
danger of its catching fire.
The previous calcination recommended for certain
matters, without specifying the reason, as for ceruse
and salt of lead, is to be considered here only in a
pracdcal point of view, as a mere precaution in the
process. When these matters are employed without
previous calcination, it will be proper not to add them
to the almost boiling oil but in small separate portions.
In all cases where preparations of lead are employed
for freeing oils from their greasy principles, great care
must be taken not to stir the mixture too much with a
H 2
100 Treatise on varnishes. >
spatula, because the oil then becomes charged with the
lead, and, combining with it, retains it under the form
of soap. The oil is thus rendered exceedingly thick,
and assumes the consistence of jelly. It will be sufficient
to leave the mixture to itself over a gentle fire capable
of making the liquid enter into a slight degree of ebul-
lition.
I have known painters of ornaments, and coach
painters, who preferred adding sulphate of zinc (white
vitriol) to their colours rather than applying it to the
Jjreparation of their oil. This method is defective. The
salt refuses to incorporate with the oil. It then renders
the painting mealy, and even occasions cracks in it.
The garlic, often added to preparations of this kind,
is eVriplOy^d' merely for the purpose of indicating the
iiiôment when the whole aqueous part of a mixture is
evaporated : it however possesses of itself a very dry-?
ing 'quality.' The gTirlic alone, or the juice of garlic,
employed in a proper dose would render oil exceedingly
drying. It is even used, in certain cases to form a
ground to colours which refuse to adhere to the bodies
on -which tliev are applied.
■ Drying oil is employed for several purposes. When
colourless it is- much sought after by those who paint
pictures. It enters into the composition of varnish,
and it serves itself as varnish in oil painting, either em--
jîloyed alone, or diluted with a little essence of turpen-
tine. When destined for house painting it will be ad-
vantageous to use, for the last coating, that to which I
give the name of resinous chijmg oil, and which exhi-
bits all the qualities of a varnish. I hav€ often em- -
, RESINOUS DRYING OIL. 101
ployed it for painting applied to bodies sheltered from,
the rain and the sun, by mixing it with the delicate
colours. It is to be recommended also for strong. gc3^
lours, such as yellow, red, green, and in |jartieul.ar
ochres. The preparadon of it is as follows: -"' '.
RESINOUS DRYING OIL.
Take 10 pounds of drying nut oil if the paint is de-
stined for external articles, or 1 0 pounds of
drying linseed oil if for internal.
Resin 3 pounds.
Turpentine 6 ounces.
Remarks.
. Cause the resin to dissolve in the oil by means of a
gentle heat. When dissolved and incorporated with
the oil, add the tuipendne : leave the varnish at rest,
. by which means it will often deposit portions of resin
and other impurities ; and then preserve it in wide-
mouthed bottles. It must be used fresh-: when suf-
fered to grow old it abandons some of its resin. If
this resinous oil assumes too much coïisistence,. dilute
,, it with a little essence, if intended for articles sheltered
from the sun, or with oil of pinks. . „ ,
. ; In.my country, where the principal par4: of the mason
■^#ôrk consists of stones subject to crumble to pieces,
k is often found necessary to give* them a coating of oil
paint to stop the efi'ects of this decomposition. This
painting has a great deal of lustre, and when the last
coadng is applied with resinous oil it has the effect of a
yarnish: To give^ it more durability the first ought to
V . H 3 -
102 TREATISE ON VARNISHES.
be applied exceedingly warm, and with plain oil or oil
very little charged with the gray colour, which is added
to the two following.
In general, eveiy first coating with oil applied to a
Wall, ceiling, &c. ought to be exceedingly warm, to
harden the surface which is to receive the painting.
DRYING OIL FOR PRINTERS* INK.
Printers' ink is a real black paint, composed of lamp
Élack and linseed oil, which has undergone a degree
of baking superior to that of the different drying oils
already mentioned. A greater or less consistence is
given to it, according to the strength of the paper; and
this depends on the degree of baking given to the oil,
or on the mixture of a greater or less dose of lamp
black.
The degree of heat applied to the oil is sufficiently
great to decompose it in part, and even to make it in-
flame. Should this prepared oil retain unctuosity, it
would fill the eye of the letter, run upon the paper,
and communicate to it a semi-transparency of a yellow
colour. This effect is particularly striking in works
printed with bad ink.
The preparation of this ink is simple : Boil linseed
oil for eight hours in a. large iron pot, and add to it bits
of toasted bread, for the purpose, no doubt, of ab-
sorbing the water contained in the oil. Leave it at rest
till next morning, and then expose it eight hours more
to the same degree of heat, or until it has acquired the
necessary consistence: then add lampblack worked up
with a mixture of essence of turpentine and turpentine.
DRYING OIL FOR PRINTERS IKK. 103
ITiis operation is to be performed in the open air, to
prevent the bad effects of the vapour of the burnt oil,
and, in partie alar, to guard against accidents by fire.
This process deserves a place here, because it -form.s
a part of those employed for giving oils a drving qua-
lity, and as the result of it is real oil painting ; but,
beiiîsf foreign to the art of the varnisher, it is not
i)ecessary to jiiake any further obseiTations on this
subject.
n 4
[ 104 1
CHAPTER III.
General ohservations on varnishes ^ u>ith a dlstrilution of
them into Jive genera, determined by their nature and
state of consistence.
Xke word varnish is a general expression used to de-
note every dry or liquid substance, the extension of
which over solid bodies gives to the surfaces of them a
certain lustre by a combined effect of the reflection and
refraction of the rays of light. Confining our view to
this single effect, there are many substances which may
be confounded with those that appear to us to possess
all the essendal qualities necessary for producing this
lustre in a permanent manner. Thus water, oil^ and
indeed every fluid, spread over the surface of polished
wood, soon changes its appearance, and gives it a cer-
tain lustre, which must not be confounded with that
resuking from the application of a real varnish, because
this effect is not permanent.
The case is not the same with pure gums, such as
that of the cherry tree, plum tree, &c. and in particular
gum arabic, when diluted with a certain quantity of
water. These substances form real varnish, the effect
of which is permanent, and which is sometimes em-
ployed with success to preserve from alteradon certain
porous bodies, such as eggs ; and to heighten in other
bodies the splendour of their natural colours, as is the
case in regard to shells. The same end is aecomplish-
çd under the hand of the naturalist by albumen (the
GENERAL OBSERVATIONS ON VARNISHES. 105
white of ïin egg) diluted with a little brandy. It is the
same substance also which gives a lustre to that kind of
varnish with which boots and shoes are covered. In
the last place, gelatin (animal jelly) diluted with water
participates in the same properties. In a word, every
liquid, transparent substance which deviates from the
sim-plicity of the composition of water ; vv'hich is sus-
ceptible of uniform extension over a solid body; which
does not suffer itself to be entirely dissipated; and which,
in evaporating in part, leaves on the body it covered
some traces of its presence, exhibits the phsenomena
of a varnish, and approaches more or less to the qua-
lities of real varnish.
In consequence of these reasons I might have been
induced to form varnishes of this kind into a particular
class, had I not been prevented by considering that
the art of the varnisher can dispense with this supple-
ment. I shall yield to the same motive in regard to
stony and saline substances, which by means of certain
processes and the assistance of heat are converted into a
kind of glazing, which has been ingeniously applied
to the decoration of the fine kinds of pottery— a branch
of industry that maintains so many manufactories of
. earthen- ware .and. porcelain. These, however, are reaî
varnishes ; and in the arts are knovm Qnly under that
technical appellation. The art, then, the processes of
Ms^hich I mean here to examine and describe, is confined
■ to the composition and use of the varnishes resulting
from a solution, of , resinous or gummo-resirious sub-
stances in different spirituous or oily liquids, according
i06 TREATISE ON VARNISHES.
to the consistence required to be given to the varnishes,
and the use to which they are destined.
Confined within these limits, the art of the varnisher
consists in discovering and applying to practice certain
formulae of composition ; and in endeavouring to unite
the essential qualities which constitute good varnish ;
namely, lustre, transparency, and durability. The last
quality is the most difficult to be obtained.
From the knowledge acquired respecting the nature,
of the substances capable of being employed in the
composition of varnish, one might be induced to be-,
lieve, that if the application of it to objects of lux-
ury be of a modern date, the invention of it may be
traced back to that antient peiiod when the art of heal-
ing acquired its formulae. The apothecary was ob-
liged, in consequence of his profession, to make fre-
quent solutions of resinous substanccis in spirituous ve-
hicles. These solutions, known under the name of
tinctures^ were so many kinds of varnish, wliich to
become really so required only to be applied to objects
dilïerent from those for which they were intended. It
is probable that the period of their application to the
purposes of luxury is not much latei than that when,
the Jesuit missionaries made known, on their return
from China, the beautiful lacquered wares of that coun-
try. The chemists, who found in these beautiful spe-
cimens objects of comparison, exerted themselves to
discover the means of imitating thei^,e compositions by
substances with which they were familiar. It may he
readily conceivedj fvcm this short view, that every resi-,
COMPOSITION. 107
nous or gummo-resinous solution in a proper fluid,
suLcepùbie of depositing by evaporation the substance
k is charged with, and of making it appear under the
form of a transparent lamina, brilliant and more or
less solid, constitutes what in the language of the arts
is called varnish.
FARTS OF WHICH THE ART OF THE VARNISHER IS
COMPOSED.
The art of the vamisher comprehends three essen-
tial parts :
1st, Composition.
2d, Application.
Sd, Polishing.
FIRST PART.
Composition,
This part is confined to resinous, inflammable sub-
stances, which have a certain analogy to some spirituous
liquors, in consequence of which they are disposed
to unite with them mechanically, by that kind of afli-
nity which the integrant moleculse of resinous bodies,
and those of the fluid that serves them as a vehicle,
exercise on each other.
In consequence of these conditions, established on
the analogy and homogeneity of the substances em-
ployed, it may be readily conceived that this part must
be confined to a certain number of resinous bodies
and oily substances, the composition of which ap-
proaches very near to, and is often identically the same
Ï08 TREATISE ON VARNISHES.
as, that of resins. Thus all essential oils, the spon-
taneous or forced evaporation of which leaves a resin>
ous residuum, exercise on resins, which are only dried
essential oils, a kind of affinity, founded oft this homo-
geneity of principles, and on this necessary analogy. •■
In all cases, the solution of resins seems ta take
place iii tlie inverse ratio of the quantity gf the essential
water, or that which enters as a principle into the com-
position of the vehicle employed. Sometimes, how-
et^er, the solution depends so much on a particular
state of composition, that it forms an exc^pt-ion to this
kind of rule. A vehicle is often employed, the com-
position of which deviates so much from the nature of
essential oils, that water seems to be one of its predo-
minant principles. This difference, however, does
not constitute a character which ought to make it be
rejected ; since, on the contrar)'', water is considered
as one of the principal agents in the composition of
rarnish, when applied to resins, the choice of which
has been determined by experiment: of this kind is
alcohol (spirit of wine). '
But on the orie hand, if varnishes formed with alco-
bol seem to be those mos- endov.'ed with a drying qua-
lity, as well as the most brilliant, and the least dis-
agreeable to the sensation cf smell ; and if they are
the least liable to communicate a foreion colour to the
o
.grounds on which they are applied; they are, on the
other, destitute of that consistence and solidity which
are justly considered as the most essential qualities of
varnish, the excipient of which is of an oily nature.
The: observation of these differences has iiiduced
AEPLICATiO>f AND POLISHING. W$
artists to . confine themselves, in the employnvant of
yamish, within certain bounds. None of the compo-
sitions known are indiscriminately proper for all pur-
poses ; because a certain concordance ought to exist
between the varnish and the article to the decoration
of which it is intended to contribute. The varnisher
finds it sometimes convenient to retard the desiccation
of his composition, that proper time may be left to the
designer to delineate and even, to detail his subjects.
. In other cases, he -endeavours to give to the bodies
which he covers with his composidons a soHdity capa-
ble of oj^posing. a certain resistance to shocks and t(j
friction.
. These circumstances, which are well known to all
persons acquainted with tlie detail's of this art, render
it necessary to have compositions of various kinds,
which it Y/ill be proper to treat of separately. The
method of classing, objects, according to their essential
properties, has appeared to us that best suited to the
present case. We shall, therefore, apply it to the
distribution of varnishes, being persuaded that it will
facilitate researches respecting the different kinds of
yamish, and the varied cases of their application.
i- - SECOND,. AND THIRD PART.
AppUcation and polishhig.
■■■ The- two.- other parts which constitute the art of
the varnisher relate more directly to the artist than to
the amateur. . Tiiey require more experience than
study. The applicadon and polishing of varnish rj&.
110 TREATISE ON VARNISHES.
quire practice. The precepts, however, which are ap-
plied to this part, present no difficulty which may not
be surmounted by an intelligent and skilful amateur.
It is the mechanical part of the art; and it deserves
observations which will be introduced when we come
to treat of the use of varnishes, and of colours, and
of the means established by art for giving to the
whole the necessary beauty and splendour.
Recapitulation,
Every resinous substance, soluble in alcohol (spirit
of wine), forms a varnish fit to be employed if the
resin be of such a nature as to have no decided influ-
ence on the colour of the liquid. Resinous substances
of a soft and viscid consistence, such as turpentine,
Canadian balsam, that of Judea, &c. ; dry resins, such
as mastic and sandarac ; soft resins, such as galbanum
in tears, gum elemi, gum anima, &c. are susceptible
of forming varnishes, by dissolving wholly or in part
in alcohol. In like manner, all essential oils, as well
as expressed oils, when they have been subjected to
those preliminary preparations which give them a dry-
ing quality, form varnishes, when they keep resins,
gummo-resins, or balsams, in a state of solution.
The composition of varnish depends then on the
property of solubility, in which several substances par-
ticipate, but with modifications depending on their
particular nature. These substances, however, when
thus united, exhibit mixed properties, much superior
to those they possess individually, and which concur
to produce results that are sought for in the common^
RECAPITULATION. Ill
kinds of varnish; that is to say, speedy desiccation,
lustre, and solidity.
However apparent the different points of relation
which seem to exist between the principles that con-
stitute resins, it may readily be perceived that their
identity is not completely established. They exhibit
in their texture and in their physical properties dif-
ferences very striking. They cannot, therefore, all
present the same phasnomena, when treated separately.
The necessity of the mixtures which constitute the
common formula has soon been perceived ; and it is
on these mixtures that the variety of the compositions,
and of their results, is founded. Certain varnishes
possess a drying quality in an eminent degree : these
are the least durable. Others are glutinous, fat, and
long in drying; but these are the strongest when they
have attained to the proper degree of desiccation. Some
hold an intemiediate rank between these two kinds ;
they have therefore a mean quality between those var-
nishes the most exposed to accidents, and those which
present the greatest resistance to the impressions and
friction of hard bodies.
A careful obseiTation of these differences could not
but induce the authors who have written on the art of
varnishing, to distinguish them by the help of a classi-
fication, founded on the nature of their composition,
and on the uses for which they are destined.
I have thought it my duty to follow the same order.
It has the advantage of exhibitin'T- each varnish sur-
rounded, in some measure, by its particular properties,
and of enabling artists to refer known compositions^
112 TREATISE ON VARNISHES.
and such as may afterwards be invented, to one of the
genera or species determined by the order and nature
of their component parts. This division also indicates
the cp.se in which they may be employed, and the
mode of using them.
DIVISION OF VARNISHES.
Two classes of varnish, Qi\'ided into genera and sub-
divided into species, may be admitted in this work.
The first class comprehends the varnishes used for ob-
jects of natural history, the genera of which are bor-
rowed from that of the substances employed, and which
may belong to the vegetable kingdom, as the solution
of a pure gum ; or to the animal kingdom, such as
gelatin (the gelatinous part or jelly), extracted from
different parts of animals. I have already spoken of
those kinds of varnish which are employed under some
particular circumstances, and which depend more on
art by their effects than by die state of their compo-
sidon.
The second class, which is the principal object of this
w^ork, ought to comprehend, and indeed does so, the
varnishes resulting from the solution of one or more
resinous substances in a spirituous or oily vehicle. It
will be exceedingly convenient to divide it into five
genera, each of which has its proper species. These
genera and species depend on the essential quality of
the varnishes ; on the state of their consistence ; and
on their drying quaUty, more or less striking.
The first genus comprehends the most drying var-
nishes that can be obtained with alcohol (spirit of .wine).
"*•»!»
i C i.,. / J, .;<*
DIVISION OF VARNISHES, ll^'
The second genus presents formulas for varnish
nearly similar to those of the first ; but they are of a
less drying nature, in consequence of the addition of
less drying resins. • This second genus gives different
species of mutative or changing varnish, which do
not require so much solidity as those destined for
glazing metallic surfaces.
The third genus is reserved for composidons in
which the nature of the excipient is changed. Alco-
hol here gives place to essential oils, and in particular
to essence of turpentine. This class ought to compre-
hend changing varnishes, and those distinguished by
I the name of mordants.
The fourth genus is destined for the employment of
pure copal treated with essence of turpentine, and even
with ether. These varnishes vie, in point of solidity,
with those of the following genus, and ought even to
be preferred to them.
The fifth genus admits of fat drying oils being em-
ployed as the excipient. It contains the fat varnishes
' made with copal, with amber, and with caoutchouci
Their colour, which is pretty dark, confines the use of
them to grounds of a dark colour.
Each composition will be accompanied with parti-
cular remarks, relating to the process; to the nature
and qualities of the varnish; and to the circumstances
most favourable for its application. This new arrange-
ment appears to be the more convenient, as it will better
enable the artist to make use of the subjoined obser-
vations, than if they were united into one body and
' separated from the formulas.
I
114 TREATISE ON VARNISHES,
FIRST GENUS.
drying varnishes made with alcohol
(spirit of wine).
First species.
No. I.
1 akc Pure alcohol 32 ounces.
Purified mastic 6 ounces.
Gum sandarac 3 ounces.
Very clear Venice turpentine 5 ounces.
Glass coarsely pounded 4 ounces.
Remarks.
Reduce the nrdstic and sandarac to fine powder;
mix this pox^'der with white glass, from which the
finest parts have been separated by means of a hair
sieve ; put all the ingredients with alcohol into a short-
necked matrass, and adapt to it a stick of white wood,
round at the end, and of a length proportioned to the
height of the matrass, that it may be put in motion.
Expose the matrass in a vessel filled with water, made at
first a little warm, and which must afterwards be main-
tained in a state of ebullition for one or two hours. The
matrass may be made fast to a ring of straw.
The first impression of the caloric (heat) tends to
unite the resins into a mass : this union is opposed by
keeping the matters in a state of rotary motion, which
is easily eifected by means of the stick, without stirring
the matrass. When the solution seems to be suffi-
1
FIRST GENUS. 115
ciently extended, add the turpentine, which must be
kept separately in a phial or a pot, and which must be
melted, by immersing it for a moment in a balneum
marige. The matrass must be still left in the water for
half an hour, at the end of which it is taken off; and
the varnish is continually stirred till it is somewhat cool.
Next day it is to be drawn off, and filtered through cot-
ton. By these means it will become exceedingly limpid.
This simple process is sufficient for the composition of
all those species of varnishes which will form part of
the first four genera, unless it is necessary to operate
on a large scale. Many amateurs are satisfied with
simple digestion for such varnishes, taking care to stir
often the mixture. This method, which may be proper
for varnish composed with alcohol, would be too slow
for varnishes of the third and fourth genera. In general
the digestion is terminated by some hours' exposure to
the sun. This second exposure approaches very near
to the use of a balneum marise ; and, like it, requires
the precaution of renewing the surfaces by sdrring the
sediment with a clean rod.
The addition of glass in this case may appear extra-
ordinary; but experience induces me to recommend
the use of it. This substance divides the parts of the
mixture which has been made with the dry ingredients,
and it retains the same quality when placed over the
fire. It therefore obviates with success two inconve-
niences, which are exceedingly troublesome to those
who compose varnishes. In the first place, by dividing
the matters, it facilitates the action of the alcohol; and.
in the second its weight, v/hich surpasses that of resins,
I 2
V
1 If) /V ,..:Y.RE-^ TISE ON VARNISHES.
pre\éjiàts .these iwit's from adhering to the bottom of
the'jntat-rassj.-'aiid also the coloration acquired by the
varnish -when a sand bath is employed, as is commonly
the case.
I have obsen'ed that the best alcohol can never be-
come charged with more than a third of its weight of
the resinous isubstances subjected to its action. The
particular examination I have made of several kinds of
varnish, the consistence of which was proper, never
indicated a greater increase of weight than a fourth
part of the primitive absolute weight of the alcohol em-
ployed. In this respect I was struck with the large
doses V\'hich the best authors employ in several of their
formulae. There are some resins, indeed, so difficult ot
solution, that they suffer verv Httle of their substance to
be attacked ; and therefore the doses of them may be
increased when they are mixed with other resins. But
these particular cases may be known. There arises,
therefore, a loss of resin, which ought to be prevented
by corrections which I shall here propose, and which I
have always followed.
It would be forming a wTong idea respecting the
nature of the resins which appear to be properest for
solution in alcohol, were we to believe that they dis-
solve enuirely in that fluid v/hen employed in high
doses. One may be easily convinced, by a series of very
simple trials, that these substances are composed of
molecuise, the chemical properties of which vary in
regard to their degree of solubility. They ought to
be considered as composed of parts exceedingly soluble
m a low temperature, and even on thqir simple contact
4
riRST GENUSV<. '^x C VJl 7
with alcohol; of other parts some\Vîjnt/les3'',gpli|bIe,
- . . ^ . • ' ■ ^» <■*
and which require to be assisted by a little ihsd^ and
of others on which the impression of the air, of the
sun, and even of the heat of infusion, has effected
a modification, which is perceived by the resistance
they oifer to the action of the spirituous liquid. These
three parts, however, constitute in the resin a homo-
geneous whole; and nothing but the process of solu-
tion, and its results, can make them be observed under
their real characters. But whatever may be the quan-
tity of the liquid added to the resinous residuum, with
a view to obtain a complete solution, the effect will not
ansv/er expectation.
When too large a dose of matter, therefore, is added
to alcohol, the latter seizes on the most soluble parts,
and has very httle effect upon those which are less so.
The dry parts of the resin escape the action of the
liquid if only a moderat,e heat be employed, as is here
practised. In this case the varnish has very little
colour; but if it seems to gain in pliability, it loses in
point of consistence and solidity. It is of great ad-
vantage to unite all these three characters at the same
time ; and this may be accomplished by limited doses,
and by employing a little more time and pains in the
process.
The process of making varnish may be reduced to
simple trials; or, if conducted on a large scale, is sub-
ordinate to general precepts, a view of which will be
found in the following chapter.
The varnishes which constitute the first genus are
employed fof the most part to supply the place of
118 TREATISE ON VARNISHES.
glazing. They are brilliant, but do not all possess the
same degree of solidity. The first species exhibit more
pliability than consistence or body. The appHcation
of them seems suited to articles belonging to the toilette,
such as dressing-boxes, cut-paper works, &c. The
next species possess the same brilliancy and lustre ; but
they have more solidity, and are exceedingly drying.
Second species of varnish of the same genus.
No. IL
Take Pounded copal of an amber colour, once lique^
fied according to my method, 3 ounces.
Gum sandarac 6 ounces.
Mastic cleaned 3 ounces.
Clear turpentine 2^ ounces.
Pounded glass 4 ounces.
Pure alcohol 32 ounces.
Mix these ingredients, and pursue the same method
as that indicated for No. I.
Remarks.
The opinion generally entertained of the insolubility
of copal in alcohol might have inspired me with some
doubt in regard to the emplovment of this matter. I
might even have dreaded that criticism which has not
spared the authors of the Parfait T^^ernisseur and of
the Dictionnaire des Arts, &c. ; but I can assert that
the mixture I have here indicated will give a varnish
much more durable than if no copal had been employeti*
' FIRST GENUS. Il9-
The great division of this substance obtained by grind-
ing it on porphyry, and by its mixture with other resins,
favours the action of the alcohol over it ; and the parts
detached from it are sufficient to give to this varnish a
character or solidity very remarkable, and which it
would not have possessed in the same degree without
copal.
If you are desirous to facilitate the solution of a
greater quantity of copal, you may add to this for-
mula three gros of camphor ; but this dose must not
be exceeded.
The case already mentioned in regard to an over-
charge of dry matters, when there are any which resist,
in part, the action of the vehicle presented to them, is
here exemplified. If the copal were entirely suppressed,
the alcohol would still find a sufficient quantity of mat-
ters to form the varnish.
Uses.
This varnish ir> destined for articles subject to fric-
tion, such as furniture, chairs, fan-sticks, mouldings,
Szc. and even metals, to v/hich it may be applied with
success. The sandarac gives'it great durability.
First species of var)iis/t of the scone ^^eiuis, desliiied
J'ur {/te same articles as No. J I.
No. III.
Take Gum sandarac 8 ounces.
Pounded mastic 2 ounces.
Clear turpentine 4 ounces.
Pounded glass 4 ounces.
Alcohol 32 ounces.
i4
120 TREATISE ON VARNISHES,
Remarks.
The fomiula for this varnish is e??tracted from
Watin's work. The dose of the turpentine appears to
me to be rather too large ; because it diffuses through
the varnish a viscous matter, which renders it long ii\
drying. Besides, it communicates to it a strong smell,
which to many persons is exceedingly disagreeable.
This formula authorizes an observation which may be
applied to many other cases : when a substance, which
by its nature and consistence is exceedingly soluble, is
subjected to the action of a pound of alcohol, it preci-
pitates in part the other dry substances which do not
possess the same degree of solubility. A kind of re-
sinous crystallization which covers the bottom of the
vessel then takes place, if the mixture be left at rest.
This consideration alone would induce me to suppress,
in this formula, the half of the turpentine,
SECOND GENUS OF VARNISHES.
ALCOHOLIC VARNISHES LESS DRYING THAN THE
FORMER, AND HAVING A WEAKER SMELL.
First species for cut-paper jvorks, dressiiig-boxes, and
other articles of the like kind, ^c.
No. IV.
Take Gum sandarac 6 ounces.
Gum elemi 4 ounces.
Gum anima 1 ounce.
Camphor J^ ounce.
Pounded glass 4 ounces.
Pure alcohol 32 ounces.
SECOND GENUS. Î2Î
Make the varnish according to the prescription al-
ready indicated. The soft resins must be pounded with
the dry bodies. The camphor is to be added in pieces.
Remarks.
These varnishes of the second genus admit modifica-
tions in the nature of the substances which concur to-
wards their formation. , They are not so dry as those
of the first genus. They give pliability, brilliancy, and
solidity to the compositions, without injuring their dr)^-
jng quality.
Second species of the same genus, destined Jor the
same purposes.
No. V.
Take Gallipot or white incense 6 ounces.
Gum anima 7 ^ ,
^ , . s or each 2 ounces.
Gum elemi 3
Pounded glass 4 ounces.
Alcohol 32 ounces.
Make the varnish with the precautions indicated for
No. I.
Remarhs.
Varnishes composed according to the last two for-
mulas may be employed for the same purposes as those
which form the first genus. They are much fitter,
however, for ceilings and waintscoting, coloured or
not coloured : they may even be employed as a cover-
ing to parts pair*ted with strong Tyater colours.
122 TREATISE ON VARNISHES,
Tliird specks of (he same genus, for irainscnling^
small articles offtniilure, hilustrades, and rail-
ing in the inside of a house.
No. VI.
Take Gum sandarac 6 ounces.
Shell lac 2 ounces.
Colophonium or resin -^
White glass pounded .of each 4 ounces.
Clear turpentine - - J
Pure alcohol 32 ounces.
Make the varnish according to the directions given
for No. L
Iiemarks.
Watin prescribes eight ounces of sandarac and six
ounces of turpentine. This dose- appears to me too
strong, as it is not proportioned to that of the alcohol,
which in my formula finds more matter than it can
take up.
'iliis varnish is sufficiently durable to be applied to
articles destined to daily and continual use. Varnishes
composed with copal ought, however, in these cases,
to be preferred. There is another composition which,
v.ithout forming part of the compound varnishes, is
employed with success for giving a polish and lustre to
furniture made of wood : wax forms the basis of it.
Manv cabinet-makers are contented with waxing
common furniture, such as tables, cliests of drav/ers,
I'^rc. This covering, by means of repeated fiiction, soon
acquires a polish and transparency v/hich resemble those
oi varmsh. Waxnig seems to possess qualiucs peculiar
SF.COND GENUS. l25
to itself; but, like varnish, it is attended with its in-
conveniences as well as advantages.
Varnish supplies better the part of glazing ; it gives
a lustre to the wood which it covers, and heightens the
colours of that destined, in particular, for delicate arti-
cles. These real and valuable advantages are counter-
balanced by its want of consistence : it yields too easily
to the shrinking or swelling of the wood, and rises in
scales, or splits, on being exposed to the slightest sho(?k.
These accidents can be repaired only by new strata of
varnish, which render application to the varnisher ne-
cessary, and occasion trouble and expense.
Waxing stands shocks ; but it does not possess in the
same degree as varnish the property of giving lustre to
the bodies on which it is applied, and of heightening
their tints. The lustre it communicates is dull ; but
this inconvenience is compensated by the facility with
which any accidents that may have altered its polish
can be repaired by rubbing it with a piece of fine cork.
There are some circumstances, therefore, under which
the application of wax ought to be preferred to that of
varnish. This seems to be the case in pardcular with
tables of walnut-tree wood exposed to daily use, chairs,
mouldings, and for all small articles subject to constant
employment.
Eut as it is of importance to make the stratum of
v.'ax as thin as possible, in order that the veins of the
wood may be more apparent, I flatter myself that the
follov^'ing process, which I received from one of my
countrymen very expert in the art of making the ard.
cics alluded to, v.'ill be acceptable to my readers.
I2i Treatise on varnishes.
Melt over a moderate fire, in a very clean vessel,
two ounces of white or yellov/ wax ; and, when liquefied,
add four ounces of good essence of terpentine. Stir
the whole until it is entirely cool, and the result will
be a kind of pommade fit for waxing furniture, and
which must be rubbed over them according to the
usual method. The essence of turpentine is soon dis-
sipated ; but the wax, which by its mixture is reduced
to a state of very great division, may be extended with
more ease, and in a more uniform manner. The es-_
sence soon penetrates the pores of the wood, calls forth
the colour of it, causes the wax to adhere better, and
the lustre which thence results is equal to that of var-
nish, without having any of its inconveniences.
Fourth species of the same genus. Famish slightli/
coloured for violins and other stringed instrumentSy
and even for furniture of plum-tree wood, maho^
^any^ and rose wood.
No. VII.
Take Gum sandarac 4 ounces.
Seed lac 2 ounces.
Mastic - - - "> r ,
_. . . . : or each 1 ounce,
Benjamm m tears 3
Pounded glass 4 ounces.
Venice turpentine 2 ounces.
Pure alcohol 32 ounces.
The gum sandarac and lac render this varnish du-
rable : it may be coloured with a little saffron or dra-.
gon's blood.
SECOND GENUS. 125
Fifth species of the same gemis, ichich the turners of
St. Claude employ for boires made of box-wood, of
the roots of trees, &c.
No. VIII.
Take Seed lac 5 ounces.
Gum sandarac 2 ounces.
Gum elemi l-i- ounce.
Venice turpentine 2 ounces.
Pounded glass 5 ounces.
Pure alcohol 24 ounces.
Remarks.
The artists of St. Claude do not all employ this for-
mula, which required to be corrected on account of
its too great dryness, which is here lessened by the tur-
pendne and gum elemi. This composidon is secured
from cracking, which disfigures these boxes after they
have been used for some months.
Other turners employ the gum lac united to a little
elemi, and turpentine digested for som^e months in pure
alcohol exposed to the sun. If this method be follov/-
ed, it will be proper to substitute for the sandarac the
same quandty of gum lac reduced to powder, and not
to add the turpentine to the alcohol, which ought to be
exceedingly pure, till towards the end of the infusion.
Solar infusion requires care and attention. Vessels
of a sufficient size to allow the spirituous vapours to
, circulate freely ought to be employed, because it is ne-
cessary that the vessel should be closely shut, With-
iput this precaution the spirits would become weakened.
126 TREATISE ON VARNISHES.
and abandon the resin which they laid hold of during
the first days of exposure. This perfect obturation
will not admit of the vessels being too full.
In general, the varnishes applied to articles which
may be put into the lathe acquire a great deal of bril-
liancy by polishing. A piece of woollen cloth is suffi-
cient for the operation. If turpentine predominates too
much in these compositions the polish docs not retain
its lustre, because the heat of the hands is capable of
softening the surface of the varnish, and in tliis state it
readily tarnishes.
Sixth species of the same genus, for giciu^ a gold tint
to articles of brass.
No. IX.
Take Seed lac 6 ounces.
Amber or copal ground on porphyry 2 ounces.
Dragon's blood 40 grains.
ïixtract of red sandal wood obtained by water
30 grains.
Oriental saffron So grains.
Pounded glass 4 ounces.
Very pure alcohol 40 ounces.
Re marks.
To apply this varnish to articles or orn.iments of
brass, expose them to a gentle heat, and dip them into
the varnish. Two or three coadngs may be appHcd in
this manner if neccssarv. The varnish is durable, and
has a beautiful colour. Ardcles varnished in this man-
ner may be cleaned \^'iLh water and a bit of dry rag.
SECOND GENUS. J 27
Seventh species of the same genus. Changing var-
nish, or varnish destined to change or to modify the
colour of those bodies to which it is applied.
No. X.
Take Gum guttœ 4- of an ounce.
Gum sandarac ) ,
> each 2 ounces.
Gum elemi - - j
Dragon's blood of the best quality 1 ounce.
Seed lac 1 ounce.
Terra mérita ^ of an ounce.
Oriental saffron 12 grains.
Pounded glass S ounces.
Pure alcohol 20 ounces.
Remarks.
The tincture of saffron and of terra mérita is first
obtained by infusing them in alcohol for twenty-four
hours, or exposing them to the heat of the sun in sum-
mer. The tincture must be strained through a piece of
clean hnen cloth, and ought to be strongly squeezed.
This tincture is poured over the dragon's blood, the
gum elemi, the seed lac, and the gum guttaî, ai!
pounded and mixed with the glass. The varnish is
then made according to the directions already given.'
It may be applied with great advantage to philoso-
phical instruments : the use of it might be extended
also to various cast or moulded articles with which fur-
niture is ornamented.
If the dragon's blood be of the first quality, it may
give too high a colour 5 in this case the dose may be
15S_ TREATISE ON VARNISHES.
lessened at pleasure, as well as that of the other coIouî'-
ing matters.
It is with a similar kind of varnish that the artists of
Geneva give a golden orange colour to the small nails
employed to ornament watch-cases ; but they keep the
process very secret. A beautiful bright colour might
be easily communicated to this mixture ; but they pre-
fer the orange colour produced by certain composi-.
tions, the prepai'ation of which has no relation to that
of varnish, and which I have successfully imitated with
saline mixtures, in which orpiment is a principal ingre-
dient. The nails are heated before they are immersed
in the varnish ; and they are then spread out on sheets
of dry paper.
Eighth species of the same genus. Changing varnish
ichich may he employed to give a gold colour to
ivatch-casesy watch-keys^ and other articles made of
brass.
No. XL
Take Seed lac 6 ounces.
Amber - - t
^ 5>or each 2 ounces.
Gum guttse ^
Exti'act of red sandal wood in water 24 grains»
Dragon's blood 60 grains.
Oriental saffron 36 grains.
Pounded glass 4 ounces.
Pure alcohol 36 ounces.
Remarks,
Grind the amber, the gum lac, gum guttas, and dra-
gon*s blood on a piece of porphyry : then mix them
ÊECOND <ÎE>TÙS. 129
with the pounded glass, and add the alcohol, after
forming with it an infusion of the saffron and an extract
of the sandal wood. The vamish must then be com-
pleted as before. The metal articles destined to be
covered by this varnish are heated, and those which
will admit of it are immersed in packets.
The tint of the varnish may be vaiied by modifying
the doses of the colouring substances.
The use of alcoholic varnishes will long be preferred
to that of the varnishes which form the third and fourth
genera ; which, however, are far superior in all cases
where it is necessary to add durability to the other qua-
lities required. A comparison, which may be easily
made in regard to articles subject to constant employ-
ment, will one day support theory and experience, and
rectify the public opinion |ijjj this subject.
The varnishes of these fifet two genera can bear po-
lishing as well as the hardest com.positions which consti-
tute the three other genera : but as they are more de-
licate, they admit modifications in the operation. It
is never begun with pumice stone.
The most of these varnishes are desdned for covering
preliminary preparations whi'chhave a certain degree of
lustre. They consist of cemqnt, coloured or not colour-
ed, charged with landskips and figures cut out in paper,
which produce an effect under the transparent vamish:
most of the dressing -boxes, and other small articles of the
same kind, are covered with this particular composidon,
which, in general, consists of three or four coatings of
Spanish white pounded in water, and mixed up with
parchment glue. This first coating is smoothed with
ISO TREATISE ON VARNISHES.
pumice stone, and then polished with a piece of new
linen and water. The coating in this state is fit to re-
ceive the destined colour, after it has been ground with
water and mixed with parchment glue diluted with
'water. The cut figures with which it is to be embel-
lished are then applied, and a coating of gum or fish
glue is spread over them, to prevent the varnish from
penetrating to the preparation, and from spoiling the
figures. The operation is finished by applying three
or four coatings of varnish, which when dry are po-
lished with tripoli and water, by means of a piece of
cloth. A lustre is then given to the surface with starch
and a bit of doe skin, or very soft cloth. I shall resume
this subject when I come to treat of polishing.
THIRD GENUS OF VARNISHES.
Particular observations.
The varnishes which compose the third genus are less
exposed to the alterations to which those that form the
first two genera are sometimes subject. The nature of
the excipient is here different : essence of turpentine
is substituted in the place of alcohol ; and this sub-
stance exhibits itself under different degrees of concen-
tration. Almost all the resinous substances, and even
the colouring substances, hitherto employed, are familiar
to this third genus, and by their various mixtures with
the essence may concur to accomplish the same views,
and produce the same results.
It must not however be believed, notwithstanding
what has been here said, that the properties of alcohol
THIRD GENUSi 131
and those of essence, considered as capable to effect so-
lutions, essential to the coloration of varnishes, are
identical ; they differ in many respects. Alcohol be-
comes charged with some particular substances, which
are refractory to essence : of this kind are certain co-
louring matters, such as indigo, turnsole, red sandal
wood, saffron, &c. On these essence of turpentine
produces no effect. In like m^anner, also, essence
under certain circumstances exerts all the energy of
solution on copal, which resists alcohol unless it be di-
vided by a soluble body. At any rate, what it would se-
parate vv'ithout an intermediate substance would not be
sufficient to constitute a varnish.
These differences in the chemical properties of these
tv/o liquors are not the only ones which might be ad-
duced to justify the admission of this third genus. A
consideration of no less importance may be added,
namely, the superiority of varnishes made with es-
sence to those composed with alcohol. The former
unite pliableness and smoothness to brilliancy and du-
rability : they yield better to the operation of polishing,
and are less liable to crack than alcoholic varnishes.
All these qualities, which ai'e well knov/n, ought to
induce artists to prefer this genus in all cases where
the preservation of the articles to which they are ap-
plied is an object of importance. This preference is
necessary, in particular, for valuable paintings.
In alcoholic varnishes the deposit of the resinous
matter, divided and in a state of complete ccluticn, is
sooner formed, according as the season, or circum-
stances arising from an artificial temperature, accelerate;
K 2
132 Treatise on varnishes.
the evaporation of the dividing fluid. The nature of
this fluid is sufficiently known; and it gives no reason
to suspect that any of its parts incorporate with the
resinous moleculas, the precipitation of which confirms
the effect of a varnish : the alcohol then evaporates
en tirely.
The case is not the same with essence of turpentine,
even the most ethereous, nor with other liquids which
have all the characters of oils. They are not suscep-
tible of «itirc evaporation. These liquids form with
resins a union the more intimate, as they add to their
division by the interposition of their own substance.
The less oils are light or volatile, the greater therefore
will be the solidity of the varnishes resulting from their
mixture with resins, and vice versa. The state of dry-
ness observed in certain resinous bodies, and which
is communicated to the varnishes, resulting from their
union with alcohol, is then compensated and corrected
in the case of their solution in an oily fluid, which en-
velops them in a fixed viscous and yet drying substance.
Essence of turpentine, and oils of a greater densit)-,
which are still better, would alone form varnishes by
a continued succession in the application of coatings.
Alcohol in this case would disappear without leaving
any trace of its presence.
The consistence which varnishes acquire from- es-
sence is often increased by that arising from the par-
ticular nature of the matters which form part of' the
changing vaniishes, and particularly of that of the
varnishes distinguished by the name of mordants. In
giving the formula for varnishes of this third kind, I
THIRD GENUS. 133
shall follow the order indicated by the degree of their
tenacity, and of their resistance to desiccation.
First species of varnish for valuable paintings.
No. XII.
Take Mastic cleaned and washed 12 ounces.
Pure turpentine \^ ounce.
Camphor 4- ounce.
White glass pounded 5 ounces.
Ethereous essence of turpentine 36 ounces.
Make tlie varnish according to the method indicated
for No. I. of the first genus. The camphor is employed
in pieces, and the turpentine is added when the solu-
tion of the resin is completed. But if the varnish is to
be applied to old paintings, or paintings which have
been already varnished, the turpentine may be sup-
■ pressed, as this ingredient is here recommended only
in cases of a first application to new paintings, and just
freed from white of egg varnish.
The ethereous essence recommended for vamish
is that distilled slowly, and without any intermediate
substance, according to the second process given for
its rectification.
Remarks.
Ijj,, The question proposed by able masters respecting
3 the kind of varnish proper to be employed for paint-
Jl ings has never yet been determined. Every artist b*as
1 K 3
134 TREATISE ON VARNISHES.
his prejudices, strengthened by example or uçage, and
he inaiRCalns them by specious arguments. The value,
however, which ought to be attached to the works of
great masters, requires stabiKty of opinion in regard
to the choice of varnish which tends to embellish and
preserve works of genius.
The varnish destined for this use ought to be colour-
less, if possible, that it may communicate no foreign
tint to the tones of the painting; it ought to unite
phabiHty and smoothness to the most perfect transpa-
rency, in order to r jurish the colours and the canvas.
It must not, however, have too much glazing, as the
reflection of the light is injurious to the effect.
Alcohol renders varnishes too dry for paintings, as
they split and crack. Varnishes composed with essen-'
tial oils, which have too much body, give too great
thickness to the coating, so that they cover, or impede
the effect of the colours. But in choosing varnishes
of this sort one of the most requisite qualities is, that
the composition should be veiy simple, and of such a
nature as not to resist the means employed, when it is
necessary to substitute a new coating in the room of old
varnish.
These considerations have induced some artists to
pay particular attention to this object; but they all make
a mystery of the means they employ to obtdn the desired
effect. The real end may be accomplished by giving to
the varnish, destined for painting, pliability and soft-
ness, wdthout b' ing too solicitous in regard to what
may add to its consistence or its solidity. The lattei*
THIRD GENUS. 135
quality is particularly requisite in varnishes which are
to be applied to articles much exposed to friction, such
as boxes, furniture, &c.
The following formula I have employed for thirty
years ; and the varnish resulting from it has been ap-
plied with success to paintings in the most valuable
collections *.
* As every thing that relates to the preser\'ation or repairing of
paintings is of great importance to artists and amateurs^ the follow-
ing observations on this svibject will perhaps not be unacceptable
to the reader :
The variety of varnishes^ often destructive, which are applied
to paintings, occasions some complication in the means employed
to remove them in order to substitute others in their place.
A new painting has often no other covering than white of egg.
This varnish is of the simplest kind : it consists only of two or three
ounces of weak alcohol (brandy), in which a gros or one eighth of
an ounce of sugar, and the white of an egg, has been dissolved. The
white of egg, with the sugar reduced to the state of powder, is
beat up with the alcohol, and the varnish is then applied with a
very soft sponge to the picture, placed in a horizontal position.
This varnish, if a few drops of the juice of garlic be mixed with
it, or if the vessel in which the white of egg is beat up be only
rubbed with it, will preserve the painting from being dirtied hv
flies.
When it is necessary to remove this coating, tlie process em-
ployed is as simple as that for the preparation of the varnish. A.
sponge moistened with warm water is drawn over the surface of
the picture with a slight degree of pressure. A kind ot froth is
then formed, -which must be washed off with watery and this
operation is repeated till no more froth appear. This method is
sufficient to remove not only white of egg varnish, but also that
made with gum arable, fish glue, or any other matter soluble in
water. There is no reason to be under anv apprehension for the
K 4
ISO TREATISE QN VARNISHES,
Second species of varnish of the same gemis, for
grinding colours^
No. XIII.
Take New gallipot or white incense 4< ounces,
Mastic 2 ounces.
Venice turpentine 6 ounces.
Pounded glass 4 ounces.
Essence of turpentine 32 ounces,
colours ; because the -v^'ater has no action on the oil with which the
colours have been mixed.
Great masters rarely varnish their pictures after they are finished:
they protect their tints by a coating of white of egg, and do not
varnish tliem till a j-ear after, when tlie colours are completely dry.
The metliod here described for removing this coating requires care
and attention. The pictui:e is left to àry, and the varnish is ap-»
plied A\ith precautions which are well known to all real artists.
More ditïiculty occurs in regard to old paintings. Besides var-
nishes ou which alcohol and oil produce no effect, they are ofteij
spoilt by foreign bodies, the nature of v/hich is unknown, and
which resist tlie action of soap. Essence of turpentine Indeed may
remove many stains j but it is attended witli the inconvenience of
attacking the colovus and softening the oil which gives them body.
Olive oil, and also butter, may be substituted in its stead with ad-
vantage. These two fat unctuous bodies do not attack the coloursj,
or at least produce on them a ver}- slow eriect.
Resin, which forms the basis of the old varnishes, gives some
hold to an alkaline solution composed of one ounce of potash and
eight ounces of water. This is a metliod very much used, but it
requires great care. If the alkali removes old resins, and if it con-
verts them into a kind of soap, it exercises a similar action on tlie
fielours, or rather on the drying oil which binds the coloui-s of ths
THIRD GENUS. 137
When the varnish is made with the precautions
already indicated, add prepared nut or linseed oil two
ounces,
Remarhs.
The matters ground with this varnish, which is
nearly similar to that of Holland, dry more slowly ;
they are then mixed up with the following varnish, if
it be for a common painting, or with particular var-
nishes destined for colours and for grounds. In treat-
ing of the diiï^arent kinds of colours, I shall mention
painting. lyong habit and tlie eye of a painter, therefore, are re-
quired to judge of the inconvenience of this method.
Very pure alcohol is a powerful agents not only in removing
oily stains, but also tJiose resinous substances which constitute
varnishes 5 and it is not attended with the inconvenience of alter-
ing ,tli3 colours mixed with prepared oil. It will exercise no
action on them^ unless the colours have been mixed with oil of la-
vender or oil of turpentine. It will be proper, therefore, to ascer-
tain the nature of ilie oil which has been employed, by making a
trial in one of the corners of the picture.
In general it is proper to begin the cleaning of pictures by first
drawing a sponge, dipped in warm water, over the surface of
them : if the motion given to the sponge does not produce frotli,
the varnish is of a resinous nature. This washing is often suffi-
cient to call forth the colours, and restore their original lustre.
But if the painting is covered with varnish rendered yellow by
time, opake, and v,'hich absorbs tlie colours, place it in a hori-
zontal direction ; and having poured pure alcohol over it, keep it
moistened in this manner for some minutes without employing
friction. If cold water be then applied to the surface, it will re*
move the alcohol, and tlie portion of resin which has been dissoh'ed
or softened. But care must be taken not to use friction, for fear
of attacking the ground. When the surf ice is dry^, the operation
is renewed until the varnish is entirely removed.
138 TREATISE ON VARNISHES.
the species of varnish which ought to be employed in
grinding them and in mixing them up.
Watin substitutes in the room of the Dutch varnish,
which is commonly employed for grinding colours, a
composition which appears to me to be too much
charged with ingredients. Essence can scarcely dissolve
the half of them. The rest forms a residuum which is
mere loss*.
Sometimes^ however, tJie painting is covered with a varnish
composed of fat oil and insoluble resin, such as copal. In this
case the attempt must be abandoned, because the purest alcohol as
well as leys will produce no effect. Even essential oils, which
Hiight seem proper on such occasions, would only whiten the sur-
face of the varnish and intercept tlie light, to tlie prejudice of the
colours.
However, if the picture be of great value, and seems worth the
expense^ ether may be substituted v/ith success in the room of the
substances before mentioned. The property I discovered in this
liquor of dissolving copal is an evidence in its favour, as being fit
for the pui"pose in question. To this property it unites another no
less essenli.nl, namely, that of not attacking the drying oil by
which the colours are bound. This method is expensive, if the
proper kind of ether be employed ; but the loss occasioned by its
evaporation may in some measure be prevented, if a cloth dipped
in ether be applied to the canvas, and pressed closely down witli a
metallic plate or piece of glass.
When a picture is dirtied with smoke and dust, a sponge dipped
in ox gall drawn over it v.ill restore its original splendour. If ir
l]as not been varnished, it will revive the brightness of the colours ,
provided it be gently nibbed j andin this manner it may be pre-
pared for receiving varnish.
Flies also dirty paintings, and render it necessary to wash them
frequently. This operation is troublesome, and attended witli
danger. Some assert that the odour of laurel oil, which tliough
* See his i\rt of making Varniihj edit, of 1/72.
THIRD GENUS. 189
TJdrd species of the same genus. Fizrnish proper to
be employed in mixing up colours Jor grounds.
No. XIV.
Take Gallipot or white incense 12 ounces.
White glass pounded 5 ounces.
Venice turpentine 2 ounces.
Essence of turpentine 32 ounces.
Make the varnish after the white incense has been
pounded with the glass.
very pleasant, is disagreeable to those insects, and drives them from
apartments in which it is kept. As it is of a solid consistence, it ma/
be easily empkyed. Some of it put into tin-plate boxes might be
placed on tlie cornices of rooms containing pictures worthy of
being preserved from their approach.
Varnishes made with essence keep much longer in a mass than
those made \^'ith alcohol. They even improve by not being imme-
diately applied. My method is to expose them in a place weVL
liohted, but sheltered from the direct rays of the sun. In the space
of some months they become thick, and acquire an oily consist-
ence, vv'hich renders the application of them much more advan-
tageous. -
If the varnish I have here mentioned be applied to a picmre
when ne-vly prepared, the essence speedily makes its way to the
colours of *he painting, if it has not been before varnished, and the
app ication of it is less œconomical than if it were a year old. It
will be proper, in particular, not to apply tlie coatings too soon
after each other, especially if the picture has been newly painted,
I have known amateurs who applied three coatings of varnish in ,
tlie course of two or three hours. In this case, the first coating
serves as a vehicle to the second, which loses itself in part in tlie
first : by these means an uneven surface is formed, and the appli-
cation of a third is rendered necessary. But if an inteival of two
or tlu'ce d:'.ys be left after the application of tlie first coaling, tlie
140 TREATISE ON VARNISHES»
Remarks,
Some authors recommend mastic or sandarac m the
room of gallipot ; but the varnish is neither more beau-
tiful nor more durable. "When the colour is ground
with the varnish No. XIII. , and mixed up with the latter,
which if too thick is thinned with a little essence, and
which is applied immediately, and without any sizing,
to boxes and other articles, the coatings acquire suffi-
cient strength to resist t^e blows of a mallet. But if
the varnish be applied to a sized colour, it must be
covered with a varnish of the first or second genus.
Fourth species of the same genus» Changing var»
rush of a less drying quality than the species No. JT»
and applicable to metal.
No. XV.
Take Seed lac 4 ounces.
Sandarac or mastic 4 ounces.
Drap-on's blood -^ ounce.
Terra m.erita 1 ~ ,
_, > of each SQ grams»
Gum guttœ J
Pounded glass 5 ounces.
Clear turpentine 2 ounces. '
Essence of turpentine 32 ounces.
resinous part of the varnish, which has acquired consistence, in-
coi^rates with the colours of the picture, and is capable of en-
during the impression of a second coating, which will be sufficient
to give the painting brilliancy, and to defend it from the attacks of
moisture and of time.
THIRD GENUS. 141-
Extract by infusion the tincture of the colouring sub-
stances ; and then add the resinous bodies according to
the prescription given for No. I.
Remarks.
Varnishes of this kind are called changing ; because
when applied to metals, such as copper, brass, or ham-
mered tin, or to wooden boxes and other furniture,
they communicate to them a more agreeable colour.
Besides, by their contact Avith the common metals they
acquire a lustre which approaches tliat of the precious
metals, and to which, in consequence of peculiar in-
trinsic qualities or certain laws of convention, a much
greater value is attached. It is by means of these
changing varnishes that artists are able to communicate
to thin leaves of silver and copper those shining coloui^s
observed on foils. This product of industry becomes
a source of prosperity to the manufacturers of buttons
and v/orks formed with foil, which in the hands of the
jeweller contributes with so much success to produce
that reflection of the rays of light which doubles the
lustre and sparkling quality of precious stones.
It is to varnish of this kind that we are indebted for
the manufactory of gilt leather, which, taldng refuge in
England, has given place to that of papier mâché, whJch
is employed for the decoration of palaces, theatres, he.
In the last place, it is by the effect of a foreign tint
obtained from the colouring part of saffron, that the
scales of silver disseminated in confection d'hyocinthe
reflect a beautiful gold colour.
142 ^TREATISE ON VARNISHES.
The colours transmitted by different colouring Sub-
stances require tones suited to the objects for which they
are destined. The artist has it in his power to vary
them at pleasure. The addition of anatto to the mix-
ture of dragon's blood, saffi^on, &c. or some changes
in the doses of the more colouring bodies, will easily
lead to the modifications intended to be made in co-
lours. It is therefore impossible to give limited for-
mula.
There is one very simple method by which artists may
be enabled to obtain all the different tints they require.
Infuse separately 4 ounces of gum guttas in 32 ounces
of essence of turpentine, and 4 ounces of dragon's
blood and an ounce of anatto also in separate doses of
essence. These infusions may be easily made in the
sun. After fifteen days exposure, pour a certain quan-
tity of these liquors into a flask, and by varying the
doses you will obtain different shades of colour.
These infusions may be employed also for changing
alcoholic varnishes ; but in this case tlie use of saffron
as well as that of red sandal wood, which does not
succeed with essence, will soon give the tone neces-
sary for imitating with other tinctures the colour of
gold. The fat golden varnish already described ac-
quires its colour from a similar mixture of tinctures.
This genus of less drying varnishes admits also an-
other species, which approach nearly to the nature of
fat varni::hes, and which are known under the name"
of mordants»
THIRD GENUS. 14S
Fifth species of the same genus. Varnish distlnguislwd
by the name of mordant.
No. XVI.
Take Mastic 1 ounce.
Gum sandarac 1 ounce.
Gum guttae 4- ounce.
Turpentine -\ ounce.
Essence of turpentine 6 ounces.
Remarhs.
Some of the artists who make use of mordants sub-
stitute for the turpentine an ounce of the essence of
lavender, which renders this composition still less
drying.
In general, the composition of mordants admits of
modifications, according to the kind of work for
which they are destined. The application of them,
however, is confined chiefiy to gold. When it is re-
quired to fill up a design with gold leaf on any ground
whatever, the composition which is to serve as the
' means of union between the metal and the ground
ought to be neither too thick nor too fluid ; because
both these circumstances are equally injurious to deli-
cacy in the strokes : it will be requisite also that the
composition should not dry till the artist has completed
his design.
Besides, many artists never make use of prepared
^mordants. They substitute in their stead an extem-
pore mixture, which they correct at pleasure.
144» TREATISE ON VARNISHES.
Some prepare their mordant v/ith Jew*s pitch and
drying oil diluted with essence of turpenihie. They
employ it for gilding pale goid, or for bronzing.
Other ardsts imitate the Chinese, and mix with
their mordants colours proper for assisting the tone
which they are desirous of giving to the gold, such as
yellow, red, &c.
Others employ merely the fat varnish of the fifth
genus, No. XXL, to which they add a little red oxide
of lead (minium).
Others make use of thick glue, in which they dissolve
a little honey. This is what they call hatture. When
they are desirous of heightening the colour of thé gold
they employ this glue, to which the gold leaf adheres
exceedingly well.
Every artist makes a mystery of his composition. I
present mine because its qualities appear to me to be | i
fit for every kind of application, and in particular for ■ '
;that to metals.
Expose boiled oil to a strong heat in a pan : when a i \
black smoke is disengaged from it, set it on fire, and
extinguish it a few moments after by putting on the i
cover of the pan. Then pour the matter, still warm,
•into a heated bottle, and add to it a little essence of
turpentine.
This mordant dries very speedily ; it has body, and
adheres to, and strongly retains, gold leaf when applied,
to wood, metals, and other substances.
These examples are sufficient to show the-nature of the j
varnishes which compose the third genus. The' follow- 1
4 • \
FOURTH GENUS. 14:3.
ing genus will make the reader acquainted -ivith; others "
which have still more solidity.
Under the head No. XXV. will be found another
mordant, still fatter,- with which bro\vn colours may be
mixed.
FOURTH GENUS.
COPAL VARNISHES MADE WITH ETHER AND ESSENCE
OF turpj:ntine.
Preliminari/ obsenatio)is.
The distinction which may be established between
those composidons of varnish which constitute the
three preceding genera, is facihtated by various consi-
deradons. The dry nature of the resins which form
the basis of them, and their friability, evidently an-
nounce that solidity is not one of their inherent qualities.
The merit, indeed, of the most of these composidons
seems to be confined to their drying quality and to
their brilliancy. The two following genera will unite
to these first characters consistence and solidity.
Copal, which serves as a basis to this fourth genus,
seems to trace out an intermediate line between all the
genera of varnish. The particular nature of this sub-
stance, which unites solidity to transparency, and the
property I have found it to possess of entering readily
into solution, in a mean temperature, or a temperature
approaching that of boiling water, are so many cha-
racters which destine it to collect in varnish all the
qualities which are sought for in this kind of com-
position.
J.
\.
-■y
146 TREATISE ON VARNISHES.
A process which furnishes the arts with a colourless
Tarnish, possessed of a very drying quaUty; a sweet
odour during the time of its evaporation, and in parti-
cular a great degree of solidity ; a varnish which,
when extended over metallic surfaces, forms a stratum
of greater hardness than that found in the vitreous
crust which serves as a covering to enamel, since it
opposes greater resistance to shocks and to the friction
of hard bodies, ought justly to be classed among those
discoveries which are most interesting to certain useful
arts. Two substances only concur towards its compo-
sition : copal and rectified ether.
Had I discovered it sooner, I should not have under-
taken my researches respecting the solution of copal in
essence of turpentine; though the result of them may
serve to extend our resources in regard to a great num-
ber of different objects.
This fourth genus of varnishes comprelicnds formulai
which will give so many kinds of composition ; but
they will not all possess the drying qualities in the same
degree. This circumstance, which traces out the order
of their description, indicates at th.e same time that they
anay be employed for different objects. The least diy-
ing will be proper for metallic articles ; because their
desiccation may be accelerated by means of a stove.
The theoretical observations I have already kud before
the reader, in the preliminaiy remaries in regard to
varnishes of the third genus, are perfectly applicable to .
those which form the fourth genus, since ihcy exhibit
all the qualities of the best varnish.
iFOURTH GENUSi 147
Pir.st species. Coped varnish ichli ciher.
No. XVII.
Take Ambery copal -^ ounce.
Ether 2 ounces.
Reduce the copal to very fine powder, and intro-
duce it by small portions into the flask which contains
the ether ; close the flask with a glass or a cork stop-
per, and having shaken the mixture for half an hour,
leave it at rest till the next morning. In shaking the
flask, if the sides become covered with small undula-
tions, and if the liquor be not exceedingly clear, the
solution is incomplete. In this case add a little ether,
and leave the mixture at rest. The varnish is of a
light lemon colour.
Rernarksi
It appears to mè astonishing, that this property which
ether possesses of becoming charged with copal should
have escaped Macquer, who subjected caoutchouc to a
variety of experiments for the same purpose. It is
probable, that the knowledge he had obtained of the
little eflect which ether produces on amber, prevented
him from trying it on copal, the properties of \\'hich it
was then usual to confound with those of amber.
The affinity v/hich ether has for copal is so great,
that when the powder is poured into the flask, some
particles of it, seized by the vapour as it escapes from
the flask, soon form small stalactites, extending from
the extremity of the Card which supports the powder
L 2
Î45 TREATISE ON VARNISHES.
to a considerable distance uilhin the mouth of the
flask. The attraction of fine iron filings, put in mo-
tion by the presence of an artificial magnet, will give
to persons acquainted with magnetic effects a perfect
idea of this phsenomenon.
When copal is presented to ether in small portions,
as I have indicated, the pov^der which fails to the bot-
tom assumes the form of a small mass, the volume of
which decreases in a very sensible manner: under these
circumst-Linces it exhibits the same pha^nomena as a bit
of sugar' ill cold water, except the bubbles of air dis-
engaged from the sugar, and which are not produced
from copal.
Copal vvithout colour, or very little coloured, passes
more slowly and in less quantity into ether. Copal
\ cry much of an ambery nature was that which ap-
peared to me to succeed best.
According to the observations which I made, the
largest quantity of copal united to ether may be a
fourth, and the least a fifth. The use of copal varnish
made with ether seems, by the expense attending it, to
be confined to repairing those accidents v/liich fre-
quently happen to the enamel of toys, as it will supply
the place of glass to the coloured varnishes employed
for mending fractures, or to restoring the smooth surface
of paintings v/hich have been cracked and shattered.
The great volatility of ether, and in particular its
liigh price, do not allow the application of this varnish
to be recommended but for the purposes here indicated.
i have seen it applied to wood with complete success,
and the glazing it produced united lustre to solidity.
FOURTH GENUS. 149
In consequence of the too speedy evaporation of the
liquid it often boils under the brush. 1 found, means,
however, to retard its evaporation by spreading over
the wood a slight stratum of essential oil of rosemary,
or lavender, or even of turpentine, which I afterwards
removednvith a piece of linen rag : what remained was
sufficient to retard the evapgration of the ether.
Second species. Copal varnish with essence of
turpentine.
No. XVIII.
Take Copal of an amber colour and in powder 1'
ounce.
Essence of turpentine 8 ounces.
The specific gravity of the essence ought to be seven
gros, and from 50 to 52 grains in a flask containing
an ounce of distilled water ; Fahrenheit's thermometer
being at 59*'.
Expose the essence to a balneum mariœ, in a wide-
mouthed matrass with a short neck : as soon as the
water of the bath begins to boil, throw into the essence
a large pinch of copal powder, and keep the matrass
in a state of circular motion. When the powder 'is
incorporated with the essence add new doses of it ; and
continue in this manner till you observe that there is
formed an insoluble deposit. Then take the matrass
from the bath, and leave it at rest for some days. Drav/
oil the clear varnish, and hlier it through cotton.
It»
IJO TREAllSi: ON VARXI6Hi;i<.
Remarhf!.
At the moment when the first portion of the copal
is thrown into the essence, if the powder precipitate
itself mider the form of himps, it is needless to proceed
any further. This effect arises from two causes : either
the essence does not possess the proper degree of con-
centration, or it has not been sufficiently dephleg-
mated (deprived of water). Exposure to the sun, em-
ploying the same matrass, to which a cork stopper
ought to be added, will give it the qualities requisite
for the solution of the copal. This eflèct will be an^
nounced by the disappearance of the portion of copal
already put into it.
The excipient which I propose to apply to copal,
without any intermediate substance, is by most artists
considered as entirely destitute of cnerg)'. Some che-
mists have given a contrary opinion, and I profess
myself to be one of that number. I shall collect under
one point of vicvr, and consequently in a particular
chapter, the experiments I m.ade to decide this quesr
tion, which relates to the solubility or insolubility of
copal in essence. The results appear to me more in-
teresting, as they are not confined to this single fact,
They conducted me indeed to a series of observations
tvhich are foreio-n to the subiect of this work.
To obtain thus varnish colourless, it v.ill be proper to
rectify the essence of the shops, which is often highly
coloured, and to give it the necessary density by ex-
posure to the sun in bottles closed with cork stoppers^,
leaving an interval of some inches between the stopper
FOURTH GENUS. 151
and the surface of the liquid. A few months are thus
sufficient to communicate to it the required quahties.
Besides, the essence of the shops is rarely possessed of
that state of consistence, without having at the- same
time a strong amber colour.
The varnish resulting from the solution of copal in
essence, brought to such a state as to produce the
maximum of solution, is exceedingly durable and bril-
liant. It resists the shock of hard bodies much better
than the enamel of toys, which often becomes scratched
and whitened by the impression of repeated friction; it
is susceptible also of a fine polish. It is applied with
the greatest success to philosophical instruments, and
the paintings with which vessels and other utensils of
metal are decorated.
Third species. Copal varnish, made witli essencç by
■means oj' an intermediate substance.
No. XIX.
Take Copal in powder I ounce.
Essential oil of lavender 2 ounces.
Essence of turpentine G ounces.
Put the essential oil of lavender into a matrass of a
proper size, placed on a sand bath heated by an Ar-
gand's lamp, or over a moderate coal lire. Add to
the oil while very warm, and at several times, the
^ copal powder, and stir the mixture with a stick of white
wood rounded at the end. When the copal has en-
tirely disrsppeared, add at three different dmes the es-
L 4
152 TREATISE ON VARNISHES.
sence almost in a state of ebullition, and keep conti-
nually stirring the mixture. When the solution is
completed, the result will be a varnish of a gold colour,
exceedingly durable and brilliant, but less drying than
the preceding.
Re))ia/'iis.
This method ma}' have some advantage over the pre-
ceding, in case essence of a proper specific quality, and
such as I have recommended, can be procured.
Essence, whatever be the state of its specific gravity,
is capable in this particular case to dissolve copal, and
so also is alcohol. This may be easily proved by a very
simple experiment, which requires no great apparatus.
Put essential oil of lavender into a table spoon, and
heat it by placing it over a chaffing-dish. When it is
almost in a state of ebullition add a pinch of copal in
powder. Facilitate the mixture by means of a straw ;
and when the copal has disappeared, add a new dose till
the oil refuses to receive any more. Pour the solution
into a phial containing boiling alcohol, and stir the
mixture, keeping it always at the same degree of tem-
perature. The alcohol will soon seize upon both these
substances. The alcohol employed in this experiment
must be pure; for the smallest quantity of water,
foreign to its composition, would precipitate the copal,
which would then unite into a mass.
The success of this experiment often depends on a
dexterity, v.'hich may easily be acquired by persons ac-
customed to such operations.
IÏ' you are desirous of completing the experiment
without changing the vessel; that is to say, if you em^^
FOURTH GENUS. 153
ploy a meta'llic vessel capable of containing the alcohol
added to the oily solution of copal, a part only of the
boiling alcohol must be poured in, stirring the mixture
with the stick, llie copal, which forms itself into a
bail, soon enters into the vehicle. This circumstance
allows the remainder of the alcohol to be added, without
the least fear of any precipitation.
It may be readily perceived that this varnish belongs
to the second genus, which comprehends the less drying
spirit varnishes. I introduce it here, merely to serve as
a new proof of the existence of processes capable of ef-
fecting a complete solution of copal in the different
liquids commonly employed in the composition of var-
nishes. If stronger doses were employed in this process,
the varnish-alembic, which I shall describe in the fol-
lowing chapter, would be exceedingly proper,
Foiirfh .species. Copal varnish by an intermediate
substance, according to a meiliod given in the
Journal de Physique,
No. XX.
Take Copal 4 ounces.
Clear turpentine 1 ounce.
Put the copal, coarsely pulverized, into a vamish
pot, and give it the form of a pyramid, wliich must be
covered widi turpentine. Shut the vessel closely, and,,
placing it over a gentle lire, increase the heat gradually
that it may not attack the copal. ^ As soon as the mat-,
ter i;; well liquefied, pour it upon a plate of copper.
154 TREATISE ON VARNISHES.
and when it has resumed its consistence reduce it to
powder.
Put half an ounce of this powder into a matrass with
four ounces of the essence of turpentine, and stir the
mixture till the solid matter is entirely dissolved.
Remarks.
This varnish is coloured, and has no advantage over
that of No. XVIÎI. T:ie turpentine, which by the action
of the heat has undergone a commencement of decom-
position, even before the copal has entered into a state
of liquefaction, contributes greatly to give it this colour.
In this respect it is not better than No. XIX. It is
even inferior to it.
Fifth species. Copal varnish by the medium of cam-
phor and essential oil of lavender, destined for
articles ivhich require durabilitjj, pliableness, and
transparency-^ such as the varnislied wire gauze
iised 171 ships instead of glass.
No. XXI.
Take Pulverized copal 2 ounces.
Essential oil of lavender 6 ounces.
Camphor J- of an ounce.
Essence of turpentine a sufficient quantity, ac-
cording to the consistence required to be
given to the varnish.
Put into a phial of thin glass, or into a small matrass,
the essential oil of lavender and the camphor; div)
FOURTH GENUS. 155
place the mixture on a moderately open fire, to bring
the oil and the camphor to a slight state of ebullition.
Then add the copal powder in small portions, which
must be renewed as they disappear in the liquid. Favour
the solution by continually stirring it with a stick of
white wood ; and when the copal is incoiporated with
the oil, add the essence of turpentine boihng; but care
must be taken to pour in at first only a small portion.
An inverse method might be followed, by pouring
the essential oil camphorated and boihng on the copal,
liquefied separately in the matrass ; but this method
requires more practice. Besides, it would give to the
varnish a darker colour.
This varnish is little coloured; and by rest it acquires
a transparency which, united to the solidity observed
in almost every kind of copal varnish, renders it fit to
be applied with great success in many cases, and par-
ticularly in the ingenious invention of substituting var-
nished metallic gauze in the room of Muscovy talc, a
kind of mica in large laminae, used for the cabin
windows of ships, as presenting more resistance to the
concussion of the air during the firing of the guns.
Varnished metallic gauze of this kind is manufactured,
I believe, at Rouen, or in the neighbourhood.
All tlicse attempts, the principal object of which
was to find the means of making copal unite with any
liquid, without haying recourse to the influence of too
high a temperature, which might alter the principles of
its composition, seem to point out the boundaries of the
îiti, without destroying the hope of obtaining complete
success. The pliableness and tenacity observed in this
155 'j:;re|\ti5l on varnishes.
■ •■.■ -* *
singular siibstaiW/, when subjected to a series of pro-
C(y^ès,.> give E^a^on to believe that it may rival that
v.'fciet^ cortàtiKÎtes the Chinese varnish, provided the
solution- of it can be rendered easy, and secure from
those akerations which take place during the common
operation. It does not appear that the different inter-
mediate substances, hitherto employed, have been at-
tended with complete success, or at least such success
as supersedes the necessity of further researches.
Before I proceed to a simpler method, I must here
offer some obsen^ations and experiments in regard to
the influence of intermediate substances, and particu-
larly that of camphor, or the solution of copal in
alcohol. Though this object relates chiefly to var-
nishes of the first genus, it êeems connected with that
of which we here treat, and admits of this transposition.
The camphor which I have employed for thirty
years, as a medium to facihtate the solution of resin in
the composition of varnish destined for valuable paint-
ings *, might be applied in my process in doses of from
24 to 30 grains for every ounce of the pil of lavender.
It has indeed the singular property of altering the con-
sistence of the driest resins, and of rendering them soft.
In this union, which appears to be intimate, the cam-
phor itself loses the character which distinguishes it
from an essential oil, that is to say, dryness. Apothc-
caries have every day an opportunity of verifying this
fact, when they prescribe a mixture of camphor in
plasters the base of which is resinous. It softens them
to such a degree, that it is impossible to preserve the
■)«- Se« No. XII.
FOURTH GENUS, r " <'" . 157
or 40 grains for each ounce of resin. \ -v . y- ''* )
Mr. Timothy Sheldrake mentions campIïQj;' as à^e-
dium for dissolving copal in essence and alcohol. He
gives also another process, in which ammonia (volatile
alkaline spirit of sal ammoniac), in the proportion of
an eighth part of the essence employed, is substituted
in the room of camphor *.
Experiment I.
Of the three processes which he describes I repeated
two; those which regard the solution of copal in essence
and in alcohol by a mixture of camphor. That with
essence did not succeed. The author himself announce
that he always failed, except when he obtained the es-
sence from Apothecaries'-hall. It appears that this
essence had by chance all those essential qualities which
we endeavour to give it by time, and still more speedily
by the influence of light.
Experiment IL
The same experiment repeated with pure alcohol
was attended with too little success to make the
result be considered as a varnish. The alcohol ap-
peared milky, and the copal formed at the bottom
of the vessel a mass which did not seem to have de-
creased in volume. Next morning the interposed part
of the copal, which altered the limpidity of the alcohol,
was precipitated, and adhered to the sides of the glass.
The process I have described for spirituous tincture of
amber would give more hopes of success, Vv'ithout any
intermediate substance.
"* See Bibliothèque Britannique, vol. xiii.
158 TREATISE ON VARN!SHE3.
In regard to the moans proposed by the medium of
ammonia, the saline nature of that liquid, if the pro-
cess succeeds, will not admit of the product being'
placed in the class of varnishes destined for delicate
painting. It is a kind of saponaceous compound, the
use of which is not to be recommended in such cases.
Experiment HI.
Another process in \^hich the dose of camphor em-»
ployed as the means of union is much greater than
in the two preceding processes, may be f^^und in
tlie Philosophical Transactions, 'i'he author sa)'s, that
by maldng it equal to that of the copal, the whole of
the latter will dissolve in the alcohol. Thou2:h this
quantity of camphor appears to me to be far too great
to render the solution of the copal applicable to cases
wliich require the use of varnish, I followed the process
exactly.
I triturated forty grains of camphor with as much
amber-coloured copal. I emplo)'ed the same for all my
experiments. I put this powder into two ounces of
alcohol of tl^e first quality, stirred it strongly for a
minute, and then placed it on a fire of verv hot cinders,
continuing to stir it. Tlie liouid roon boiled, notwlth-
Jitanding the state of agitation in which I kept it, to
prevent the resin frorh adhering to the glass. I enter-
tained no doubt in regard to the power of the alcohol
over the camphor, though the intimate union which it
enters into, in this case, prevents a complete solution^ I
The case was not the same \^ith the copal ; the solution
of which, to judge by the appearance of the liquid,
seemed to me very problematical. It was indeed pi'e-
cipitated, and produced a small mas&, ^hfch adhered
FOURTH GENUS. 159
to the glass. On decanting the liquid, which had a
milky appearance, I was able to separate the copal,
which, though it retained a soft consistence, adhered
very little to the metallic spatula. This matter, when
dried in a gentle heat, weighed still twenty-three grains,
and appeared to me as dry as common copal.
The decanted liquor retained for some days its ne-
bulous appearance, notwithstanding the first separation
of the resinous parts interposed. The vessel at length
was incrusted with a thin coating of copal ; but I neg-
lected to ascertain the quantity.
Though this camphorated liquor could not be con-
sidered as a varnish, I thought it my duty to make a
trial of it on a piece of card, which had already re-
ceived two coatings of fish glue. Three successive
strata of camphorated liquor gave no satisfactory re-
sult : in a word, it was not a varnish.
Experiment IV,
- Being convinced by preceding researches respect-
ing the differences observed in experiments of this
kind, when different specimens of copal are em-
ployed, I endeavoured to clear up my doubts by
changing the copal. I therefore repeated the experi-
ment with specimens almost colourless, and of the
greatest purity. I observed a difference at the very
.moment of mixture. The resin was perfectly diluted;
and its state of division between the moleculae of the
liquid was such, that the rotary motion I maintained
gave to the whole a clouded appearance. The kind of
threads which circulated in the mass did not fall down ;
but, notwithstanding this phœnomenon, which I always
considered as very favourable to solution, ^d the mo-
1^ TREATISE ON VARNISHES.
tion I communicated to the Tcssel and tlvit occasioned
by ebullition, the resin united itscif under the form of
fibres, which settled at the bottom of the vessel. The
precipitated copal when properly dried weighed ten
grains. The liquid retained opacity, and some days
after there was formed a sediment around the vessel,
as in the preceding experiment. Still, however, it did
not form varnish, though it contained more copal than
that of the third experiment. But it presents us with
a new fact, which may be turned to advantage.
E?< périment V.
What I had done rendered it nccessarv for me to
try the union of camphor with the brown copal, mak-
ing use of an oily excipient, which hiLherto had ap-
peared to me the properest for succeeding with this
variety of copal. I therefore mixed twenty-four grains
of copal with as much camphor, and formed it into a
paste, which I treated with an ounce of the commoji
essence of turpentine. I produced from it a small
mass, which, after exposure to the sun for twenty d:i}'3,
still retained pliableness, and an elasticity which miglit
be compared to that of caoutchouc. In this state it
\veighed twenty-four grains. This result, which I veri-
fied on several other occasions, furnishes perhaps a key
to one of the processes employed by some of the miners
in Ducal Prussia, to give différent colours to amber,
and to render it elastic. The intimate union which
takes place between the parts of the camplior, the
copal, and a small quantity of oil, is, no doubt, alone
capable to explain this state of consistence. In a word,
this union appears to me to be of such a nature as to
v/eaken in these tv/o substances those properUes by
FOURTH GENUS. 161
-which they are best characterized : the extreme vola-
tiLty of the camphor, and the consistence of the copal.
Six months after, this small mass, left in a window and
exposed to the sim ft)r some hours eveiy day, still re-
tained a pretty solid nucleus, of a bi illiant and vitreous
fracture, but sufficiently soft to admit the introduction
into it of a needle» This nucltus was incrusted in a
spongy, friable matter of a grayish colour. The crust
formed about a third of the whole mass.
Experiment PL
The same dose of camphor and of colourless copal,
treated with the same quantity of essence, disappeared
almost entirely a few moments after its mixture. In
this case the liquor exhibited all the characters of var-
nish. A small portion, however, was precipitated, which
when collected and dried weighed S^- grains.
Experiment f^II.
One point still remained to be verified in regard to
the success of the last experiment : Had not the essence
I employed acquired, by the effect of chance, that
disposition or particular state which is communicated
to it by the solar light ? In a word, might it not be
compared to that which is rendered proper, without
any medium, for the solution of copal*?
To resolve this question, I subjected to an ounce of
the same essence twenty-four grains of the last-men-
tioned copal without colour. Agitation of the liquid
gave signs favourable to the required solution ; and '
after the action of heat had removed the mcleculse of
water interposed between those of the essence, there
* See Chap. V. Part I,
M
162 Treatise on varnishes.
remained no more than four grains and a half of copal
united into one mass in one part of the phial.
In the course of these different trials we observe
anomalies which depend, in a particular manner, on.
the nature of the copal, and the state of the oily liquid.
Copal which has much of an ambery colour, and even
the brown, which for fat varnishes, or those of the
fifth genus, is preferred to that destitute of colour,
loses in our third and fifth expenments its pre-eminence
over the latter, when the object is a solution in alcohol
or essence of turpentine, with or without any interme-
diate substance. As the first two experiments were
made some time before the one in question, I did not
think of making a series of comparative trials, employ-
ing all the variedes of tint observed in the copal of the
shops. I introduce them here m.erely that I may add,
if possible, to the confidence which artists ought to
place in the experiments I present to them, and to sug-
gest new subjects of research to those who may be in-
clined to pursue them.
From all these facts it is probable, that the difference
observed in the result of the attempts made by different
authors has arisen rather from the nature of the copal
employed than from the method they employed. I
must, however, confess that practice is necessaiy for
such researches, and that the same materials which
give successful results in experienced hands, give only
very uncertain results in others. I am, therefore, far
from bringing forward my own experiments, as argu-
ments sufficient to render useless all those of my pre-
decessors.
I
FOURTH GENUS. 163
itefiecting, however, on the different resources of
mercantile fraud, and the facility they afford for de-
ceiving persons of considerable experience, there is rea-
son to think, that certain solutions of copal, rendered
easy, in part or in v/hole, by the proposed medium,
may have nothing of copal but the name. This opi-
nion might appear too severe, and ever misplaced,
had we not recent instances that sandarac, copal in
sm^ali fragments, and amber, have reciprocally served
to cover each Other for sal? ; and had we not seen,
in particular, gum anima new, and consequently in
Very transparent fragments, pass for copal, notwith-
standing its greater friability, and the sweet odour
it emits by friction* I shall abstain from any obser-
vations on the high doses of camphor prescribed for
these different solutionSi It may enter with copal
into such a state of combination as to lose by it a part
of its volatility. This state of union appeared to me
very important, and well deserving of new researches.
I must here remark, that the addidon of camphor in
the sixth experiment was useless, as the solution of that
variety of copal evidently depended on the state of the
essence, as is seen in the seventh mixture.
Like many artists, I tried copal according to methods
of my ov/n : but not being satisfied with the researches,
the results of which I have here communicated, I en-
deavoured to overcome all the difficulties which occur
in the composition of copal varnish, whether it be re-
quired colourless, by employing essence subjected to
preliminary preparation, or whether, sacrificing this
advantage, which is doubtless very great, to the qua-
M 2
164- TREATISE ON VARNISHES.
lities found in drying oils, the methods reserved for
varnishes of the fifth genus be followed. I ought to
consider myself very fortunate if I should be able to
substitute a method which holds a mean place, and
which is sufficiently sure to deserve being recom-
mended.
The first object of those who compose varnish is to
preserve the particular properties of the substances
which form it. The great solubility of most resins in
their appropriate liquors, determined the choice of
some particular ones for the varnishes of the first, se-
cond and third genera ; and it supersedes the necessity
of complex researches. We have indeed seen, that
the simple contact of resins with certain oils, or with
alcohol, assisted by motion, or the temperature of from
50 to 60 degrees of Reaumur (from 144*' to 167° of
Fahrenheit), or even that of the sun, is always followed
by a success greater or less according to the nature
of the resin employed.
The series of my processes in regard to copal, and
those employed for amber, exhibit however difficulties
which I never before experienced. These substances
require other means ; and notwithstanding the differ-
ence observed between them, with respect to their so-
luble property, they seem to be nearly on the same
footing, and to deviate in a considerable degree from
all the resins yet known, when considered as connected
with the composition of varnish.
Stopped by the difficulties with which the solution of
these bodies is attended when the usual processes are
applied, the artist found himself obliged to attack, in
FOURTH GENUS. 165
some measure, the extreme cohesion of the aggregate
moleculae of which their mass is composed, and to alter
a little the state of composition, by applying to them a
degree of heat much superior to that which is proper
for simple infusion. This method corresponded very
well, in part, to his views ; but the dark colour which
the varnish assumes is an inconvem'ence which confines
the use of it to certain grounds and to certain colours.
Hitherto art has made no attempt to obtain a more
satisfactory result ; it has introduced no change in the
usual processes ; in a word, it has proposed no other
modification to preserv^e the first liquefied portions of
the copal from alterations occasioned in it by the con-
tinued impression of caloric (the heat), but the sacri-
fice of that part which is only softened. In this respect
I consider myself as more fortunate ; since my at-
tempts have always been crowned with success ; and
nothing is required to obtain it but a modification in
the process which I employ for the fifth genus of var-
nish. It is, however, necessary to have a particular
furnace, of which the following is a description :
Description of a furnace destined for the liquefaction
of copal and ajnher.
Those who have examined in detail the laboratories
destined for a course of chemistry, may easily form a
clear idea of the construction of this furnace, by recol-
lecting that employed for separating sulphuret of anti-
mony from its matrix. But to render it fit for the object
in question requires some alterations ; by the help of
which one may use it without incoiivenience for the
M 3
166 TREATISE ON VARNISHES.
liquefaction of solid resins, and even for mixing theni
with drying oils.
This furnace, a section of which is represented fig. 1 .
i?late IV, may be entirely constructed of burnt clay,
three large apertures being made in the lower chamber,
A, which supplies the place of an ash-hole in the
common furnaces. The upper part of these apertures
is arched ; and the pillars or solid parts between th?m
should be as narrow as possible, in order to enable the
artist with facility to extract the liquefied matter, and
even to mix it with the drying oil, if this kind of var-
nish be required.
The upper part, B, or fire-place of the furnace, is
separated from the lower part. A, by a bottom, or plate,
which answers the same purpose as a grate in the com-
mon furnaces. This plate has in the middle a circu-
lar aperture, the diameter of which corresponds to that
of the tube, C, which it is destined to receive, and
which extends a considerable way below it. This plate
may either form one piece with thé furnace," or may be
moveable. In the latter case it is supported by three
projections, or by a circular ledge which projects in-
wards. In my furnace this partition is composed of an
iron plate covered with a coating of potters' clay an
inch in thickness. This precaution is indispensably ne-
cessary to prevent the hea.t from penetrating to the
lower division, A.
The sides of the fire-place, B, are pierced with
holes an inch in diameter, and distant from each other
about three inches. These apertures admit air sufficient
to maintain the caloric (heat) at the degree proper for
4
FOURTH GENUS. 167
this kind of operation. The following are the propor-
tions of the three parts of this furnace, which served
me for my experiments, and in which I liquefied six
ounces of copal in the space of ten minutes, ^\ithout
altering its colour in a sensible manner.
Inches.
Total height of the furnace ----- 17-5-
Height of the lower chamber. A, including
the bottom, which was an inch in thick-
ness 11
Height of the upper chamber, B, or of the
fire-place 54-
Diameter, taken at the upper interior edge
of the fire-place, B - 9-1-
Diameter of the same, taken at the bottom or
partition --- 7
This part decreases in diameter 2-i- inches, tapering
towards the lower part of the furnace, A.
The tube, C, is conical at the upper extremity and
cylindrical towards the bottom : it is 9-i^ inches in length,
4-i- in diameter at the top, and 2^ towards the middle.
Both ends of it are open.
The tube, C, is placed in the aperture formed in the
middle of the partition, in such a manner as to rise 5" or
4 inches into the fire-place. The place where it joins
to the partition is luted with clay, to prevent the ashes
or small coals from fallintj down.
When this arrangement is made, the net, D, (see
fig. 2.) made of brass wire worked very open, is placed
M 4"
168 TREATISE ON VARNISHES.
in the tube. It has the shape of a funnel, the upper
edge of which is made fast to a ring of wire of the
same diameter as the upper part of the tube, C. The
decrease in the diameter of the tube C conduces to the
stabihty of this net, and the conical form of the latter
prevents it from coming into contact with the lateral
parts of the tube, which is a matter of great import-
ance to preserve the copal from too great alteration by
the heat,
The copal is placed on this metallic filter in pieces
not larger than a small nut, and the whole is closed up
with the iron plate or cover, E, an ii^ch in thickness,
taking care to lute the joining with clay, to prevent all
communication with the exterior air.
A shallow dish or capsule, F, filled wdth water,
(fig. 3.) is placed under the bottom of the tube, C, in
such a manner that the tube is immersed in the water
two or three fines.
The fire-place, B, being filled with burning coals so
as to rise above the iron cover of the tube, the first im-
pression of the heat on the copal is announced by a kind
of crackling, the consequence of its diIatatio;i, which
makes it split into small pieces. This noise is a sign
of beginning liquefaction, which indeed takes pb.ce
soon after. A small iron pallet-knife terminating in an
elbow is introduced under the tube, and moved in
such a manner as to cause the liquefied part of the
copal to fall down into the water, and to bring it under
the solid form towards the edge of the capsule. When
the operation is finisiied, the copal is spread out on dry
g
m
FOURTH GENUS. 2 69
linen cloths, or on unsized paper, to dry ; it is then piled
up and exposed to a gentle heat, to deprive it of all its
humidity.
While the copal is falling down there is separated a
very small portion of oil, which remains fluid after the
operation. It floats on the water as well as the copal,*'
and gives to the latter a greasy appearance. But when
the tube is of sufficient length there \\ill be no neces-
si*"y for immersing the end of it in the water, or even
for receiving the matter in the water ; but, in this case,
a kind of smoke will escape, which may be offensive to
the artist. The essential point is to graduate the hre
in such a manner as not to alter the colour of the
copal. When a very thick smoke issues through the
lower aperture of the tube; when the latter is very
red ; and when the drops which fall into the water rise
into bladders and form small explosions, there is reason
to conclude that the fire is too violent.
I have succeeded in composing varnish with fat oîî,
in the same operation, by substiîutiug for the water
drying oil in a stare of ebullition, and maintaiiiing it
in that slate by means of a mass of very hot iron, which
served it as a supporter. The mixture of the liquefied
matter is facilitated by means of a spatula, with a linee
at the extremity ; and the boiling essence is afterwards
added. The inconvenience of placing under the appa-
ratus a volatile and highly inflammable oil may be
.readily conceived.
I shall always insist more on the separate liquefac-
tion of copal, than on the possibility of completing the
•inixture of it with a drying oil, to form a varnish of the
170 TREATISE ON VARNISHES^
fifth genus. This new mean enables the artist to
compose a very dm'able varnish, very little coloured,
and superior to copal varnish composed with drying
oil, as the composition of the latter requires processes
which alter the essential qualities of the substances that
form the basis of it.
For operations on a larger scale the dimensions of
the furnace may be changed ; but in this case it will
be proper to establish the fire-place, properly so called,
on a kind of iron tripod, as represented at G, fig. 4,
in order that the workman may be more at his ease.
I must however always insist on the advantage of em-
ploying, in the process, doses of only four and six
ounces.
The valuable advantages which accompany this new
method will be perceived when a trial has been made
of the varnish composed with essence of tui-pentine,
which results from it. Copal thus prepared has pro-
perties different from, and more extensive than, those
communicated to it by the common method ; and it
has not that dark brown colour v.hich it acquires by
too high a temperature, and too long exposure to heat.
Immersed here in an atmosphere of caloric (heat), it
receives the impression only at the surface, which soon
yielding to the power of that agent escapes under the
liquid state from the continuance of its action ; new
surfaces are successively subjected to the same eflect ;
and the final result is copal as little altered as possible,
and which can have undergone but a very sUght modi-
fication in its constituent principles: the force only of
the connexion which existed between its parts, and
FOURTH GENUS. 171
which opposed so great an obstacle to the solutiotis
proposed to be effected, is diminished. In a word, it
is possible to compose fat copal varnish almost colour-
less, by making use of oil as little coloured as possible;
such as that of pinks prepared in leaden vessels, ac-
cording to Watin's method.
In like manner also this copal, simply modified, may
increase the solidity of alcoholic varnish in a more
direct manner than when it is employed without any
preliminary preparation. A second liquefaction would
perhaps give it the property of being soluble in alco-
hol in greater quantity ; but there would be reason to
apprehend that the alteration in its principles, carried
too far, would give it no superiority over those resins
which are most soluble in that liquid. I shall conclude
what relates to this fourth genus of varnishes with an ac-
count of the experiments I made by applying copal
thus prepared to the most usual vehicles.
Sivth spe&ies. Copal varnish with essence of iiu\
pentine, ivithout any intermediate substance.
No. XXII.
Take Copal liquefied, according to my method, 3
ounces.
Essence of turpentine 20 ounces.
Place the matrass containing the oil in a balneum
marise, and when the water is warm add the pulverized
copal in small doses. Keep stirring the mixture, and
add no more copal till the former be incorporated with
tan
172 TREATISE ON VARNISHES.
*he oil. If the oil, in consequence of its particular
disposition, can take up three ounces of it, add a little
more ; but stop when the liquid becomes nebulous ;
then leave the varnish at rest. If it be too thick, dilute
it with a little warm essence, after having heated it in
the balneum marise. When cold, filter it through cot-
ton, and preserve it in a clean bottle.
This varnish has a good consistence, and is as free
from colour as the best alcoholic varnish. When ex-
tended in one stratum over smooth wood, which has
undergone no preparation, it forms a very brilliant
glazing, which, in the course of two days in summer,
acquires all the solidity that may be required.
The same essence employed with copal of two fu-
sions, that is to say, copal liquefied a second time,
takes up a third more than in the former case. But
it produces very little effect on copal not prepared.
The facility which attends the preparatien of this
Varnish by the new method here indicated, will admit
of its being applied to all coloured grounds which re-
quire solidity, pure whites alone excepted. Painted
boxes, therefore, and all small articles, coloured or
not coloured, where it is required to make the veins
appear in all the richness of their tones, call for the
application of this varnish, which produces the most
beautiful effect, and which is more durable than tur-
pentine varnishes composed with other resinous sub-
stances.
FOURTH GENUS. 173
Neiu experiments and observations on copal.
Though essence of turpentine, by the state of its
composition, be more proper than alcohol for the pre-
paration of varnish, when it is required that it should
unite durability to splendour, there are many cases in
which alcoholic varnishes must be employed ; and the
latter require no less attention on the part of the artist.
To point out, therefore, the means of adding to their
intrinsic qualities already known, another of still greater
importance, namely, solidity, is doing a service to the
art. Copal treated according to my method is better
fitted to answer this end, as its colour is very little
altered. I shall here collect some experiments which
I made on this subject, with a view of pointing out to
those who pursue researches of this kind, what has
been accomplished and what still remains to be done.
I must here observe that the alcohol I employed was
exceedingly pure.
Experiment I.
Two deniers of copal, liquefied in a matrass with a
fourth of its weight of camphor, pulverized and di-
gested for ten days in an ounce and a half of alcohol,
scarcely communicated to it any colour; and the spe-
cific gravity had increased, at the same temperature,
only two grains.
The mixture being subjected to the heat of a balneum
mariae assumed a slight nebulous tint. This addition to
the process had increased the specific gravity of the
liquid 3-i- grains. The camphor seems to have been the
cause of this increase, if we may judge from the colour-
Il4f TREATISE ON VARNISHES.
of the infusion, which was not more charged than
before.
Experimeiit IL
Thirty-six grains of copal of one fusion*, and which
had been exposed to sufficient heat to undergo a flight
inflammation, occasioned by a defect in the construction
of the tube, and an ounce and a half of alcohol pre-»
sented a complete solution in t\vo days. A new dose of
the same copal increased the lemon colour of the liquid,
"uathout appearing to decrease much in volume after
ten days' digestion. At this period the specific gravity
of the liquid exhibited an increase of six grains. Its
fluidity did not seem to be sensibly affected, and the
copal retained a pulverulent form.
When treated in a balneum mari^ the copal formed
itself into a mass. This circumstance seemed to be
prejudicial to the solution, as the specific gravity of the
infusion showed an increase only of two grains. It
appears evident that the union of the free parts of the
copal had favoured the separation of a portion of that
which was in the state of solution, as I always took
care to wait for the return of the same temperature
before I verified the specific gravity of my liquors.
* To avoid circumlocution in the aqi. omit of these experiments,
I shall give the common name of copal to tliat which has been
subjected to no preliniinary preparation before being pulverized ;
tîiat of copal of one fusion to copal which has undergone liquefac-
tion only once^ according to my method 3 and that of copal of two
fusions to copal which has been tv.'ice liquefied according to the
taiiie process.
FOURTH GENUS. . 175
Experiment HI.
Thirty-six grains of copal of one fusion, and which
had been received in water at the time of its lique-
faction, on examining its specific gravity showed an
increase of only two grains and a half after being di-
gested ten days in I4- ounce of alcohol. The colour
of the liquid had experienced very little change.
This digestion treated in a balneum marias aban-
doned a part of its tint, and lost some of its specific
gravity, which was reduced to 1-^^ grain of increase.
Experiment IV\
A mixture made cold of tv/o ounces of copal of one
fusion, and an ounce and a half of coarsely pounded
glass in twelve ounces of alcohol, remained in the pul-
verulent state during the whole time of a long diges-
tion, even when assisted by some exposure to the sun*s
rays, and stirring the mixture from time to time. The
glass in this case contributes to the permanence of that
state. Some minutes after mixture the. liquid assumed
an ambery tint, which afterwards became darker.
After fifteen days' digestion the specific gravity of the
alcohol was found to be greater by seven grains.,
What had taken place in the second and third expe^
riments made me omit, in this case, to employ a bal-
neum juariae: I preferred long digestion. Three months'
infusion had carried the increase of the specific gravity
to thirteen grains per measured ounce of liquid ; but
the mixture did not form a varnish.
I7& TREATISE ON VARNiSHLS.
Experiment V,
I mixed two gros of copal of one fusion with the
sânie quantit)'' of camphor and six ounces of alcohol.
To facilitate the action of the alcohol I pounded
in a m.ortar, for a full hour, the camphor and the
copal, moistened with some drops of alcohol: the
addition then of one-sixth of alcohol extracted from
it a liquor of a limpid and ambery tint. The mass,
which had become soft, exhibited the consistence
and appearance of turpentine which has been knead-
ed in waiTn water, and drawn out into the form of a
cord between the fingers. A new dose of alcohol ren-
dered the liquid milky; but it soon after deposited the
divided portion of the copal which gave it that appear-
ance. The sediment remained pulverulent. It was
under this state that the successive addidon of alco-
hol reduced the whole of the small mass of cam-
phorated copal. The liquid separated from the divided
portion, which disturbed its transparency, had acquired
a very dark orange colour : some days after, this colour
had become more intense. At this period the specific
gi^avity showed an increase of six grains.
The use of a balneum marios carried this increase in
half an hoiu- to fourteen grains ; but during this opera-
tion the copal foiTued itself into a mass, and its con-
sistence was soft, and so tenacious that I was able to
take it from the vessel with the stick which had served
to keep it in modon : this matter had a greenish tint.
When exposed for twelve davs to the temperature of
scventy-tv/o or sevent}'-seven degrees of Fahrenheit, this
small mass still retained its flexibilitv; but its surface
FOURTH GENUS. ]77
was white and as it were farinaceous, the efFect of the
tranmdatioji of a part of the camphor.
Though the spirituous infusion appeared to be char-
ged, it did not contain a sufficiency of copal to malte it
answer the conditions of a vai'nish. However, when
spread out by means of a brush on wood prepared with
gum, the first stratum gave indications of varnish, and
the third formed a complete varnish. But this varnish,
which was exceedingly slow^ in drying, since at the end
of six days it still adhered to the fingjrs when placed
on it for some time, became tarnished during its desic-
cation. This efFect, which is unknown when our tur-
pentine copal varnishes are employed, may be ex-
plained by the particular union which copal forms with
camphor.
Experiment 11.
One gros of copal powder fused in a matrass with a
third of its weight of gum sandarac, put into a mixture
of nine gros of alcohol and three gros of sulphuric
ether, exhibits nearly the same ph^enomena as the pre-
ceding mixtures. It sustains pretty well the division
of its parts, and gives to the liquid a lemon colour.;
but it disturbs its limpidity. Its specific gravity, ex-
amined after eight days' digestion in a window which
received the solar rays three hours each day, gave an
increase of full eight grains.
It appears probable that the cloudiness which the
Kquid retains arises from a partial precipitation of the
copal attacked by the ether, and precipitated in part
by the alcohol, which does not exercise over it the
Same energy*
N
178 TREATISE ON VARNISHES.
The infusion treated in a balneum marias became
clearer, without being perfectly limpid. This effect
might be ascribed to the evaporation of a part of the
ether. The state of the solution experienced scaixely
any change from this process, since the total increase
observed in the specific gravity of the liquid vv^as only
nine grains. The matter still retained its pulverulent
form.
Experiment VII.
The same quantity of copal united to sandarac,
thrown into an ounce and a half of alcohol, becomes
very much divided, and remains pulverulent. The
liquid assumes a beautiful gold colour, without losing
any of its limpidity. Eight days' digestion added only
two grains more to the weight, which expressed its
specific gravity.
The balneum marise doubles this addition. In the
last process the matter had retained the pulverulent
form, for which it was indebted to the sandarac.
Experiment VIIL
It appeared necessary that I should compare the ef*.
feet of a mixture of alcoholized ether on copal, lique-
fied according to my method, with that of the mixture
which had served for the sixth experiment, in order
that I might appreciate better the influence of the san-
darac. The same doses were employed for the present
experiment. The copal became soft, and formed at
the bottom of the vessel a small mass, pretty similar
in consistence and colour to turpentine. It however*
yields to violent stirring, and extends in the liquids
FOURTH GENUS. 179
tinder the form of very thin leaves, which by rest are
soon collected into a mass. The liquid assumes a beau-
tiful lemon colour, somewhat greenish : but it is less
charged than in the two preceding experiments.
The ether does not. appear to have here so strildng
an influence as on copal mixed by fusion with sanda-
rac ; since digestion for eight days, in the same win-
dow, added only two grains to the specific gravity of
the liquid.
The application of a balneum mariae only doubled
this addition. This process seems to have no advan-
tage over those of the first and second experiments.
As the copal seems to give more hold to the alcohol
when divided by an intermediate body, or when modi-
fied by one liquefaction, there might be reason to hope
that a second would add to the extent of the solution,
by taldng copal of two fusions received each time in a
vessel filled with water.
Experiment IX,
Two gros of copal of tv/o fusions, one ounce of
coarsely pounded glass, and eight ounces of alcohol,
treated as the mixture of the fourth experiment, gave
to the liquid an orange colour ; and eight days after
the addition to the specific gravity was six grains : three
weeks after it was nine grains.
• The application of a balneum marias formed of it a
mass. This solution seemed to exhibit no mxore advan-
tages than that of the 4th experiment, \^ith copal of
onlv one fusion.
N 2
^
180 TREATISE ON VARNISHES.
Experhtient X.
Thirty-six grains of copal of two fusions, mixed with
an ounce and a half of alcohol, maintain themselves
pretty well under the pulverulent form, during a di-
gestion of ten days. The liquid assumes little colour,
and its specific gravity is increased only three grains.
By the use of a balneum mariîe the liquid becomes
turbid when cold ; the copal forms itself into a mass,
and the increase of its specific gravity is reduced to two
grains.
Experiment XL
The same quantity of copal of two fusions put into
the ethereous mixture of the sixth and eighth experi-
ments, unites into one viscid mass ; but still susceptible
of division by strong shaking. After twenty-four hours
the copal exhibits a firm consistence, and by a hard
body may be reduced to coarse powder, even in the
liquid, A digestion of ten days communicates to the
liquid a beautiful gold colour, and increases its specific
gravity six grains. The ethereous mixture has more
action on copal of two fusions than on that which has
been subjected to one liquefaction ; but this superiority
is not so great as to admit of its application for making
copal varnish. It is probable that it would have a more
decided advantage over every other resin employed for
alcoholic varnish, as is indicated by the mixture of
copal and sandarac in the sixth experiment. These
ethereous mixtures may be more happily applied with
resins exceedingly soluble in alcohol, and by these
means concur to the improvement of the varnishes of
^he first and second genera.
FOURTH GENUS. 181
The balneum niariïE occasioned no great change in
the state of the sokition, the specific gravity of which
by this second process was increased only l-^ grain,
forming by this increase a total of 9^ grains.
Experiment XI I.
C. Moulot, in the Journal de la Société de Médecine
à Paris, gives a process for dissolving copal entirely
in alcohol. Nothing is necessary but to project the
pulverized copal by pinches into the alcohol saturated
with camphor. The opinion which I conceived from
-my own researches on this matter induced me to repeat
the experiment, and to employ for this operation copal
■without any preparation, and that of one fusion.
The solution of the camphor was effected in alcohol
exposed for three days to the sun in a vessel closed
with a cork stopper. The specific gravity of the alco-
hol decanted from off the remaining camphor appeared
by my areometer to be thirty grains heavier than that
of the alcohol employed.
I subjected, at four different times, forty-eight grains
of common copal in powder to an ounce and a half of
this alcohol saturated with camphor. I each time stirred
the mixture to divide the copal, which appeared to nie
disposed to unite into a mass. In this state of division
the alcohol assumes a milky appearance ; but by rest
there is formed a thin sediment, w hich, under the form
of fine snow, occupies the half of the liquid. The part
of the latter which floats over the deposit shows no al-
teration, either in its colour or its limpidity. I conti-
■jivjed to shake the vessel for six days successively, in
N 3
182 TREATISE ON VARNISHES.
order to facilitate the solution ; but without any appa^
rent success, even under the influence of the sun du-
ring some hours every day. The hquor being then
filtered, I was able to observe its specific gravity. It
was inferior by one grain to that of the alcohol em-
ployed.
The sediment readily detached itself from the paper
by pouring pure alcohol over it ; but it was separated
in the form of lurnps, which I was able to unite into
one mass by kneading them in alcohol. This operation,
which laid hold of a part of the camphor united to the
copal, restored^to the latter its former state of dryness.
There was, indeed, separated a fine powder, a part of
which united itself to the small kneaded mass ; while
another remained suspended in the liquid, which as-
sumed a milky colour. ^After this washing, the small
mass of copal, in regard to consistence and colour, had
a great resemblance to the glutinous mxatter separated
from farina by washing it in water. In this state it
weighed fifty-six grains, which was eight grains more
than the weight of the copal employed. But it still
contained camphor and alcohol, which concurred to
produce that state of pliability which it still retained.
By some hours' exposure to the sun it was dried to the
centre : it then weighed no more than thirty-seven
grains. On adding to this quantity four grains of tlie
copal precipitated from the remaining solution, which
I had mixed with the alcohol of the washings, and
about two grains of the same matter lost on the filter,
I found a deficit of 5 grains of copal, which remained
in the state of solution, and which could, be precipi'
FOURTH GENUS. 185
tated by pouring pure alcohol into the Kqtiid, which
contained the solution and the alcohol of the washing.
Hence the maximuvi of the solution of copal, by
C. Moulot's niethod, may consume at m.ostfrom eight
to ten grains of this matter, with the quantity already
mentioned of camphorated alcohol.
Before the liquor was filtered I spread out some of
it on a piece of wood prepared with gum water. The
evaporation of the liquid caused to be deposited a slight
stratum, white and as it were mealy, which was re^
moved by the least friction. This was camphor iTiixed
with a little divided copal, which rendered it somewhat
rough to the touch.
Experiment XIIL
The above processes were repeated with the same
doses, and under the same circumstances, on copal of
one fusion.
On the first projection of the powder the liquid ac-
quired an ambery colour ; but the powder fell to the
bottom of the vessel, where it assumed a viscid and
soft consistence. Two days after, however, the de-
crease observed in its volume indicated a more exten-
sive solution than in the preceding experiment. The
camphorated alcohol had enough of colour, and yet it
retained its limpidity.
After being infused six hours in the sun, mere dé-
cantation was sufficient to separate the liquid from the
soft matter exhibited by the copal ; and my areometer
indicated an increase of six grains, on comparing its
N 4
184« TREATISE ON VARNISHES.
present specific gravity with that of the camphorated
alcohol.
I tried, but Avithout success, to knead the soft matter
which covered the bottom of the vessel. I therefore
contented myself with washing it, to remove the cani-
phor which gave it that consittence. The alcohol em-
ployed in washing it cam.e off clear, and after reposing
for some seconds, the copal had resumed its former
dryness. After its complete desiccation it was found to be
reduced to twenty-nine grains, estimating at two grains
the loss occasioned by the parts which adhered to the
sides of the vessel, and to the small spatula em.ployed
to detach it. The nineteen grains, then, which formed
the deficit, had passed into the camphorated liquid.
Though this circumstance proves that copal, pre-
pared according to my method, is superior, by its so-
luble property, to unprepared copal, the result is not
yet sufficient to constitute a varnish.
The application of a stratum of this solution to wood,
prepared with gum, was attended with the inconveni-
ence already mentioned ; tlie only difference was, that
the wood exhibited a light brown tint.
I confine myself to this plain account of the process
indicated by C. Moulot. My regr£t is, that I had not
time to repeat these expeiiments on different varieties
of copal, rather vv^ith a view of observing the differences
which might occur in its union with cam^phor, than with
a hope of composing a varnish by tliis method.
The principal object of this new labour was to as*
certain the utility of a mixture of copal with othu^
FOURTH GENUS. 18S
resins, more soluble than in alcohol, and not to add
•new formulae to the first two genera of our varnishes.
Though the greater part of the results I have here given
^re unsatisfactory, there are some of them which seem
to authorize, and even to require, the addition of copal
to certain compositions with alcohol.
The well-conducted digestion or maceration of copal
prepared by a first liquefaction with pounded glass, as
in the fourth experiment, or of copal treated over the
fire with a solid resin, such as sandarac, (Exp. VI.) or
of mixtures of other resins, the solubility of which in
alcohol is confirmed, m^ay still add to the durability of
the varnishes of the first and second genera. One
micfht even be induced to believe that the tinctures
formed in the fourth, sixth, and ninth experiments,
applied to one of our copal varnishes with essence weR
dried, would unite to the advantage of destroying the
disagreeable odour of the essence, that of adding evea
to the substance of the copal, if those genera of var-
nish which abandon their odour more readily than fat
varnishes with essence had need of such a palliative.
But no circumstance seems to show that the use of
camphor as an intermediate substance is advantageous
in the composition of copal vai-nishes with alcohol.
The sixth experiment exhibits some results which an-
nounce a more extensive solution than by the other
processes. However, if we compare these trials with
those already mentioned, we shall soon be stopped by
uncertainty in regard to the extent of the result, and
particularly by the inconvenience arising from the vola-
tile nature of the camphor. This inconvenience is not
186 TREATISE ON VARNISHES.
an imaginary evil ; it is sufficiently proved by the state
of the small flexible masses of the copal, which too
slow desiccation renders spongy and pulverulent. In
a word, if such a composition had not against it the
strong and disagreeable odour it emits, and the slow
desiccation of the varnish, one might be stopped by
the certainty of seeing the varnish insensibly lose its
lustre by the slow volatilization of the camphor ; split,
or exhibit a mealy and spongy surface, and abandon all
the characters which belong even to the most common
varnishes.
These experiments discover also another point of
utility. They throw light on the course proper to be
followed in the preparation of copal varnishes with al-
cohol, whether it be employed alone or m.ixed with
•similar substances, and on the superiority of simple
digestion to infusions exposed to too ardent a sun, or ,
to a balneum marise. The action of digestion is slow ;
but it must produce more effect on a substanee the
parts of which remain divided, than rapid infusion of
the same substance, which the action of the caloric
(heat) reduces to a mass. Besides, the second and
third experiments prove, in the most convincing man-
ner, that what is obtained by long maceration is often
destroyed by strong infusion in a balneum mariœ. I r
But other experiments prove also that, if long mar Mi
ceration geems to be proper in many cases in the com
position of alcoholic varnishes, and particularly oPJi
those which have copal for their basis, the case is not
the same in regard to copal varnish made with essence M ij
of turpentine. Infusion in a balneum rp^irias completes» ^ (,;
4
FOURTH GENUS. JST
m two minutes, a solution which could not be effected
jn several hours by maceration, and even motion. A,
israrnish of the first quality, and of an excellent con-^
sistence, which requires neitheir claiification nor filtra^
tion, and which possesses the property of drying speed-
ily, will at length be obtained. If ccpal, previously
liquefied according to my method, be used for the
composidon of this varnish, no preparation of the es.
sence will be necessary. That least proper for becom-
ing charged with copal can, in this case, take up 1-^
gros, and even more than two gros of the copal which
has undergone two liquefacdons. But in the latter
pase the varnish is a little coloured.
After the opinion I have given in regard to the em-
ployment of camphor, which is supposed to be very
useful for compledng the solution of copal in alcohol,
I ought to abstain from all further reflections on the
method proposed by C. Moulot. In this respect I refer
to the results of the twelfth and thirteenth experiments;
but I think it indispensably necessary here to call thç
reader's attention to the consequences which might be
deduced from a comparison of the state of the consist-
ence of a soluuon of copal in essence with that of the
came solution in alcohol, and from remarldng what
veal singularity these two solutions exhibit in their spe-
cific gravity.
. We have seen, in treating on the method of making
in a few minutes turpentine copal varnish, that though
this varnish had a very oily consistence, its specific gra-
vity was increased only fifteen grains per measured
'S>uncej according to my areometer. V/e have seen.
Ï8S TREATISE ON VARNISHES. "
nn the other hand, that the highl^'-charged tincture
of copal of the fourth and ninth experiments, .and that
of the camphorated copal of the fifth experiment, retain
the fluidity by which pure alcohol is characterized,
though their specific gravity, and particularly that of the
latter, approached very near to the specific gravity of var-
nish composed with essence. To these two results I shall
add two other observations, made on a highly charged
tincture of gum anima, the specific gravity of which
had increased fourteen grains, according to my areome-
ter ; and on a tincture of amber, the increase of which
was seventeen grains, v»ithout the state of the fluidity
of the alcohol appearing in either of these two cases to
be lessened.
Such efl'ects can arise only from the state of penetra-
tion or intimate union of the moleculse of the substances .
in contact ; and consequently must relate to their par-
ticular nature. It may, therefore, be readily conceived,
that this union is more striking and more perfect be-
tween alcohol presented to amber, or to copal, or to
gum anima, than between these resins and essence of
tui-pentine ; since two ounces in absolute weight of this
essence, which we know hold in solution nearly three
gros of copal, weigh only fifteen grains, of the seven
gTos and twTnty-six grains expressed by the specific
gravity ascertained by an areometer, the capacity of
which is an ounce of distilled water at the temperature
of 59'' lof Fahrenheit.
This chemical state of resins, in different liquids
which sen^e for the composition of varnishes, is truly
singular, and in this particular point of view deserves
Ï'OURTH GENUS. 189
to be further examined. But what proves in a very con-
vincing manner that essence is better suited than alco-
hol to the composition of varnish, is, that one stratum
of my turpentine varnish spread over wood, without
any preparation, renders the surface exceedingly bril-
liant, by depositing on it a very durable glazing ; while
three strata of the different tinctures of copal are re-
quired to produce upon wood the appearances of varnish.
Alcohol, then, does not seem to be suited to dry and
solid substances, such as copal and amber, which are
besides so different from common resins by their other
properdes. All hope, therefore, of composing with it
an alcoholic varnish must be renounced, if v/e banish
from the composition every intermediate body capable
of serving as a bond of union to the divided parts of
these two substances, which; the alcohol abandons by
the effect of evaporation*.
It is known, in general, that alcoholic varnishes are
the most delicate, and that they would have still less
consistence should those by whom they are made neg-
lect to introduce into the composition of them as an
essential inp-rcdient a viscid and tenacious substance,
such as turpentine, or some other of the same kind,
which acquires modifications either naturally or by the
effects of art. If this remark is well founded in the
case of common varnishes of the first and second ge-
* I composed very good varnish with the tincture of copal fur-
nished by tlie fourth experiment, by adding mastic and one-eighth
of turpentine, according to the quantity of the tincture ; but
though this varnish contained enough of copal, it could not be
considered as pure copal varnish made with alcohol.
J9Ù TREATISE ON VARNISHES.
nera, ought it riot to excite doubt also in regard to
qualities assigned, without any foundation, to simple
spirituous tinctures of copal and of amber, wheii
matters such as turpentine, or any other capable of
«diminishing the dryness of these two substances, are
banished from the composition of them ? But by ad-
mitting these necessary correctives we approach thé
varnishes of the fourth genus ; and in this case it is
more convenient, and even more useful, to make the
copal vamiBh -with turpentinCj following the prescrip*
tion indicated. In general, varnishes with essence hold
a proper medium between those which might be com-*
posed with alcohol and copal, and those which admit
the use of drying oils, as in our fifth genus of var-
nishes.
No theory is good unless founded on experience^
From experience, therefore, I think myself authorized
to assert, that the successive application of alcohol
charged with copal or amber, without a mixture of
turpentine Or other resins, cannot exhibit the qualities
of à superior varnish. The spirituous liquid abandons
6oon after by evaporation the substance it had appro-
priated to itself, and leaves it under an almost pulve-
rulent form, which the least friction whitens and causejl
to disappear. There is only one case capable of mode*
rating this effect, which is indeed certain : it is when
colouring parts are mixed with this kind of varnish. I
have as yet observed only one fact, which proves that
amber varnish composed with alcohol is capable of
glazing any surface. I observed it at the mouth of a
phial ccntainmg highly charged tincture of amber, em*-
FOURTH GENUS. 391
ployed for daily use. The successive accumulation of
the resinous part may alone serve to explain this fact.
Essence has a great advantage over alcohol in the com-
position of varnishes ; as it concurs by its om'U sub-
stance to the connection of the resinous pails of which
they are constituted. Alcohol, on the other hand, is
entirely dissipated. Varnishes vdth essence, therefore,
are more pliable, more brilliant, and more durable,
than those made with alcohol. I have also observed in
these new trials, ailromalies in the common properties
of copal, which embarrass those who employ it, and
which are calculated to involve in uncertainty every
thing we know, and every thing which can be an-
nounced as new in regard to this singular substance. I.
have already spolcen of them in my experiments which'
follow the article on the varnisti No. XXI.
The copal soU in the shops exhibits various shades of
colour, and the case with it is different from that of
all the resins applied to varnisheSj in which the varied
tints they may acquire do not seem to affect their che-
mical qualities, or to announce new ones contrary to
those which are the most apparent. There are some
specimens of it which might be confounded with the
purest gum arabic, that rs to say, absolutely colourless,
îind exceedingly transparent. Other morsels have a
v«ry light lemon colour, which in other pieces appears
more ambery, with the transparence and splendour of
the most beautiful topaz. In the last place, this colour
is often darker, and sometimes brown and very dull.
The numerous experiments I was obliged to make
enabled me to take advantage of these different varieties
Ï92 TREATISE ON VARNISHES".
of copal, and to observe that the property of solubility-
sought for in this substance is not sufficiently stable to
be in any measure distinguished by certain exteiior
signs. It depends, no doubt, on many circumstances
still unknown, and determined by the age of the tree
which fuiTiishes it; by its local exposure, by the nature
of the soil, and by the influence of its native atmo-
sphere : I have, however, had the satisfaction of con-
vincing myself that the copal proper, in general, for
making varnish is that which one might be tempted to
reject on account of its colour, and of a certain dull
aspect disgusting to the artist, who in this case attends
too much to the extreme purity of the substances em-
ployed in the preparation of transparent varnishes. The
colour of copal, however, may sometimes be consulted
to enable one to judge of its degree of solubility, espe-
cially in all cases of a charged composition, such as
that of the fifth genus of varnishes. This assertion
is supported by a great number of facts : but it does
not establish a general rule ; for I have seen copal ex-
ceedingly pure, and almost colourless, dissolve as speed-
ily in ether as copal of a bright topaz colour. I have
in my collection several pieces of this kind : other spe-
cimens extend themselves in that liquid under the form
of very fine snow, which yields to all the motions com-
municated to the vessel, but which resists a more ex-
tensive acdon on the part of ether.
It was copal of a similar Idnd, but somewhat more
coloured, which I employed for these latter experi-
ments. This resistance, however, is overcome by the
preparation here recommended, that is to say, lique-
FIFTH GENUS. 193
faction in the furnace above described ; but when pre-
sented to the essence, the ether or alcohol, it must be
jn. powder. When I made choice of this copal, I had
reason to hope that the results I should obtain from it
would be still more extensive, on repeating the same
processes with copal better fitted for the composition of
varnish.
FIFTH GENUS.
FAT VARNISHES.
Preliminary observations»
The varnishes of this genus are the most durable,
but they are the slowest in drying. They are destined
for objects exposed to friction, or to shocks from
hard bodies ; and are employed, in a particular man-
ner, for the decoration of carriages. They are applied
to v/ood, to iron, to brass, and to copper : they are
used also for painting waiters, Argand's lamps, tea-
pots, and other utensils of the same Idnd which are in
daily use.
The matters which enter into the composition of
these varnishes are few in number. The artist con-
fines his means to the solution of copal and of amber
in essential oils, in prepared linseed oil, and in nut oil
or oil of poppies. In the first experiments on balloons,
caoutchouc or elastic resin was added to these sub-
stances. We may place in the last rank that common
kind of varnish with which ships and other vessels are
daubed over.
In this case the processes are not confined to simple
o
194 TPvEATISE ON VARNISHES.
infuFions. The dry and solid nature of the substances
destined to serve as the basis of these varnishes requires
other means, and a higher temperature. Though these
substances have properties common to them all, they
possess others which are peculiar to each of them. It
is these differences which induce artists not to confound
them, or not to employ them collectively in the com^
position of their varnishes.
Copal, indeed, presents less resistance to liquefac-
tion, at a given temperature, than amber. It is more
susceptible of decomposiuon ; and the varnish result-
ing from the mixture of it with any oil is less coloured,
and not so dark as that obtained from a mixture of
amber with the same oil. If copal were mixed with
amber in the same operation, it would in a great
measure be destroyed before the latter were in a state
of liquefaction. There is a fat varnish then with copal,
and another with amber. To these I shall add that of
caoutchouc or elastic resin.
Though the doses indicated, in my different formula?^
for this fifth genus of varnishes have been proved, the
last portions of the copal, and particularly of the amber,
must not be melted if the varnish be required as little
coloured as possible. The portions of the amber
which have escaped liquefaction may be easily sepa-
rated by a sieve, or by deposition. Copal presents less
resistance, and, when em.ployed in small fragments, is
soon liquefied. In other respects I must recommend
the method indicated at the end of the description of •.-
my furnace ; because the matter, when once liquefied,
escapes from the burning atmosphere, the continued
3
FIFTH GENUS. 195"
influence of wj^^cb weiiki .have a prejudicial effect on
the nature of tte siibstance, and consequently hurt the
solidity of .the; Yarnish.
First species. Extracted from IVatiii^s ivork.
No. XXIII.
Take Picked copal 16 ounces.
Prepared linseed oil, or oil of pinks, 8 ounces.
Essence of turpentine 16 ounces.
Liquefy the copal in a matrass over a common fire,
and then add the linseed oil, or oil of pinks, in a state
of ebullition: when these matters are incorporated take
the matrass from the lire, stir the matter till the
greatest heat has subsided, and then add the essence
çf turpentine warm. Strain the whole, while still
warm, through a piece of linen, and put the varnish
into a wide-mouthed bottle. Time contributes towards
its clarification ; and in this manner it acquires better
qualities.
In general, there is much advantage in not employ-
ing too violent a heat. The varnish by these means
succeeds better, and acquires less colour. If it after-
wards becomes too thick, add a little warm essence,
that the mixture may take place more speedily. It
was in this manner that the celebrated Martin com-
posed his beautiful white fat varnishes.
o2
196 TREATISE ON VARx^ISHES,
Second .^ppcics of the same genus, employed in the
■mcuiKj'actorks of Geneva for ivatch-cases, m imita-
iion of iortoise-sliell.
No. XXIV.
Take Copal of an amber colour 6 ounces.
Venice turpentine l-?r ounce.
Prepared linseed oil 24 ounces.
Essence of turpentine 6 ounces.
It is customaiy to place the turpentine over the
ccpal, reduced to small fragments, in the bottom of
an earthen or metal vessel, or in a matrass exposed
to such a heat as to liquefy the copal : but it is more
advantageous to liquefy the latter alone, to add the
oil in a state of ebullition, then the turpentine lique-
fied, and, in the last place, the essence. If the var-
nish is too thick, some essence may be added. The
latter liquor is a regulator for the consistence in the
hands of the artist.
The doss of oil, in this case, appears to me to be
too great : eighteen ounces would be sufficient. This-
varnish is durable and transparent; but it dries v/ith
difficulty. In general a stove is employed to hasten
the desiccation : it is susceptible of a iine polish.
IlfTII GENUS, 197
Third .species. Amher varnish.
No. XXV.
Take Amber, coarsely pounded, 16 otinccs.
Venice turpentine, or gum lac, 2 ounces.
Prepared linseed oil' 10 ounces.
Essence of turpentine 1 .5 or ] 6 ounces.
The circumstances of the process are the same as-
those prescribed for the preparation of the copal var-
nish, No. XXI. '
Remarks.
This varnish v/as formerly much used ; but it has
given place, in part, to that of copal, which is pre-
ferred on account of its being less coloured. Watin
introduces more essence and less linseed oil : expe-
rience and long practice are the only authority on
which I recommend the adoption of the present for-
mula.
Copal and amber are the two dry substances appli-
cable to the composition of varnish, which are the
most difficult to be brought to the liquid state. They
require the direct application of heat.
A varnish might, indeed, be composed, according
to the practice of some artists, by treating simulta-
neously amber and copal ; bat the difference observed
in the phscnomena they exhibit in the fire ought to
make this method be rejected. The copal is, in part,
decomposed before the amber has completely aban-
doned its consistence. Besides, copal varnish without
mixture is of an amber colour and very transparent.
Q 3
19S TREATISE ON VARNISHES.
When mixed with amber the varnish is of a very dark
brown colour.
Setting out from this fact, the mixture of turpentine
IS more proper with linseed oil than with amber; and
the oil ought to be boiling when presented to the amber
in a complete state of liquefaction. But this precau-
tion is still not sufficient, if it be required, as ought to
be the case, that the three substances in contact should
unite in a speedy and intimate manner. If the whole
quantity of oil added to the turpentine were poured in at
one time, a portion of the amber would be precipitated.
This projecdon ought to be effected at several times,
taking care to facilitate the contact by stirring the mix-
ture with an iron rod. It will even be proper to bring
the mixed matter to a state of ebuUition before it be
taken from the fire.
Some ardsts do. not wait till the whole of the amber
is in a complete state of liquefacdon before they add
the oil: they are satisfied with liquefying a paBi^j'and
they then separate die fragments of the amber which
have not been melted. By this method the varnish is
leL.s coloured; but it requires more amber or copal than
is prescribed in my formulse.
Sonieti mes one is stopped by the fear of not finding
vessels rarable of standing the whole operation. A
cabt-irou pot will obviate this inconvenience, and ought
to be preferred to vessels of earthenware, which either
crack or split. When porous they are soon penetrated,
by the varnish : besides, they can be employed only
once ; the second varnisii made in them would acquire
too dark a colour. A cast-iron pot has this advantage
FIFTH GENUS. 199
also over pottery, that it can be cleaned, while warm,
to remove the portions of the old varnish, which would
be coloured by the ûre employed for a new com-
position.
Before I proceed to the composition of the otlier var-
nishes v.'hich belong to this last genus, it may be of
use to take a view of the processes I have followed in
treating copal in a manner entirely new, and to apply
fhem to amber. By adhering closely to the formukvi
established by usage and long experience, my principal
intention was to enable artists to compare them with
the simple method which I have substituted in their
stead. I should form an erroneous opinion of artists,
and particularly of those who are loth to sacrifice old
habits, were I to believe them capable of abandoning,
without opposition, the favourable idea they have
of the nature of aiiiber, and of the superiority they
ascribe to it, but without sufficient reason, over copal.
In general, they are much disposed to believe that the
character of solidity by which it is distinguished, when
considered in its natural state, and which appears to
render it superior to copal, is maintained in its mix-
ture with drying oijs, and that it becomes the principle
of the consistence of the varnishes of which it consti-
tutes the principal base.
One, however, may be easily convinced, on com-
paring the results exhibited by these two singular sub-
stances, in the kind of analysis to which they are sub-
jected, that the one which, v/hen it appears under
its natural characters, seems to have a superiority over
ihe other, resigns it to the other vvhen it has been
0 4
200 .. ,-V^EATISE ON VARNISHES.
•E>i^^l^ght to,'^e necessaiy degree of liquefaction, before
k. bè nii^Q v^ith oils in the process of making varnish.
What is then considered as an essential quality in amber
examined in regard to its constituent parts, becomes
prejudicial to it when applied to the composition of
varnish ; because the greater resistance it opposes to the
influence of caloric, at the time even of its liquefaction,
alters its principles in a higher degree than is the case
in the liquefaction of copal. The latter indeed requires
less heat, and passes more readily to the state of lique-
faction. The following experiment will give some
wei'jht to this assertion :
o
Preparation of amber occcordliig to my new process
already described.
Five ounces of amber, of a very dark orange colour,
but transparent, and in pieces of the size of a small
nut*, treated in my melting furnace, required a half
more time than copal before it exhibited the first indi-
cations of liquefaction, the fire in both cases being sub- '|
jected to the same regulation. A great deal of pretty
thick oil, and which always retained that consistence,
Vvas disengaged. It envelops in such a manner the
parts vvhich acquire solidity by cooling, that it is diffi-
cult to separate it by immersion in tepid water, and by
means of blotting paper. However, by exposing the
* The amber to be liquefied must not be employed in pieces too
Jaro^e, or in coarse powder, because it soon forms a raass, and does ;
not run so freely. It is indeed very slow, and fornishes more
fluid oil than in die present case : tlie varnishes also are more
coloured.
FIFTH GENUS. \^ ' ^ . ^p%
amber to the air for some days, it becoji^çs^^ sÔ^oIk|
that the laminse it forms may be broken b^i[weeif't|>e
fingers. In this state these laminœ have the transpai'en-
cy and colour of the hyacinth. The amber is obtained
under this form, when care is taken to bring it to the
edge of tlie vessel, filled with Vv^ater, into which it
fiOws, by means of a hook, or pallet-knife bent at the
extremity. This matter, which is pretty dry in appear-
ance, when pounded in a mortar forms itself into a small
mass, which readily crumbles to pieces. It is indebted
for this flexible quality only to a portion of the free oil,
which covers the surface of it under the form of a
varnish.
When this consistence is compared with that assumed
by copal under similar circumstances, one may readily
be convinced that the latter, the consistence of which
" is drier and even pulverulent, is preferable to amber
for the preparation of varnish. I'his opinion will even
be maintained in favour of copal of a second fusion,
the alteration of which is m.ore observed in the colour
it acquires than in its proper substance. This result,
which is sufFiciently confirmed, induces me to believe
that the process hitherto employed for the composition
of fat amber varnish, and in which the amber under-
goes a still greater alteration, only adds a thick oil to
that presented to it; and that the varnish thence re-
sulting can have no superiority over copal varnish,
composed a.ccording to my principles; since nothing
announces that the consistence, observed in the copal
before its mixture, can be v^eakened when it yields to
the laws of solution.
1
202 TREATISE ON VARNISHE?.
In considering, besides, the state of alteration which
amber experiences in the common processes, and the ,
degree of heat which these processes require, it may
still be beheved that the quantity of it which passes into
the varnish amounts scarcely to one half- of the whole.
One may suppose that a portion reduced to the state
of oil readily passes into the oil, and that it disposes
towards the same result another portion of amber less
altered, and nearer to its state of consistence. The
rest is composed of tho portion of the anfber destroyed,
and of th:it which resisted liquefaction. It is the
carbonaceous part suspended in die mixture which
occasions the alteration in the colour of the liquid,
and the thick deposit which is formed some time
after.
The unnatural state of amber in all the forced com-
positions^ which constitute this last genus of varnish,
is very proper for pointing out the advantages of the
formulae given for my fourth genus, and to dissi-
pate the least traces of the superiority ascribed, with-
out any reason, to amber over copal. By subjecting
amber to the processes so happily applied to copal, my
intention therefore is rather to gratify the taste of the
old artists, who are led away by habit, than to main-
tain any doubts on the place which copal and amber
ought to occupy in the composition of vaiTiishes, in.
regard to the intrinsic qualities they are capable of com-
municating to them. Essence furnishes enough of its
substance to constitute, and particularly with copal,
durable compositions. By giving a preference to the
varnishes of tlie fourth genus, the arti;st satisfies, at the
FIFTH GENUS. 205
same time, his own knowledge, and the anxiety of
those who employ him. By the speedy desiccation of
varnishes of this genus he is soon enabled to complete
the labour of polishing, which is always tedious when
varnishes of the fifth genus are employed.
Amber varnish with essence of turpentine.
Take Amber, liquefied according to my process,
and separated from the oily portions wfiich
alter its consistence, 6 or 7 ounces.
Common essence of turpentine 24 ounces.
Reduce the amber to powder, and if the operation
of pounding forms it into a paste, break it with your
fingers : then mix it with the essence, and treat the
whole in a balneum marine. It will speedily dissolve,
and the essence will take up at least a fourth part of its
weight of the prepared amber.
The varnish which results from it is more coloured
than that made with copal and turpentine; but it readily
clarifies, even without filtering it through cotton. It
may readily be conceived that this varnish forms a part
of those of the fourth genus.
When one coating of it is applied to white smooth
wood, but without any preparation, it forms a very
pure and very durable glazing, which speedily dries,
but slower than copal varnish. It appears to me to be
superior to highly coloured varnishes, which admit the
addition of oil in common composidons, and which to
be tl\oroughly dried require the use of a stove.
204 TREATISE ON VARNISHZ5.
As copal and amber must be liquefied before they
are mixed with drying oils, which serve as excipients
to fat varnishes, it may be advantageous to follow my
process under such circumstances as may seem to favour
the preference given to drying oils over essence of tur-
pentine. The following formula was attended vvith
complote success.
Fourth species. Fat amher or copal larnislu
No. XXVI.
Take Amber or copal of one fusion 4 ounces.
Essence of turpentine^
Drying linseed oil
■ If -,
roi each 10 ounces.
Put the whole into a pretty large matrass, and expose
k to the heat of a balneum mariai, or mo^■e it over the
surface of an uncovered chaffing-dish, but without
fiame, and at the distance from it of two or three
inches. When the solution is completed, add sdll a
little copal or amber to saturate the liquid ; then pour
the whole on a filter prepared with cotton, and leave
it to clarify by rest. If the varnish is too thick, add a
little vx^arm essence, to prevent the separation of any of
the amber.
This varnish is coloured, but far less so than those
composed by the usual method. When spread over
white wood, without any preparation, it forms a
solid glazing, and communicates a slight tint to the
wood.
If you ai"e desirous of charging this varnish with
fIFTH GENUS. 205
more copal or prepared amber, the liquid must be
composed of two parts of essence for one of oil *.
The whole of the processes here given, and which
may be applied to the composition of varnishes of the
fourth and fifth genera, leave no doubt in regard to
the course which will be followed by artists who know
how to make use of the advantages they offer, and to
compare them with each other. I am persuaded that
they will give a decided preference to turpentine var-
. nishes treated according to my method, and that in
future they will confine fat varnishes to common ob-
jects; if they are srill retained, notwithstanding the de-
fects with which, it is well known, they are attended.
I shall conclude this chapter with an account of three
cojiipositions which may be esteemed by some artists ,
but 1 must recommend the use of amber, prepared ac-
cording to the method which I have already described,
■* Amber prepared according to my methoJ suffers itself to be
laid hold of by the alcohol, to which it communicates a lemoa
colour. What distinguishes it from copal is, that it retains ils
pulveiiilent form in the heat used for infusion in a balneum mariae.
The tincture resulting from this mixture is attended witlji no greater
advantagq to varnishes than those extracted from copal.
Ether exercises on it a more striking miction : it readiiy attacks
it, and can take up a gros of it. The varnish it produces is coloured^
When deposited on wood dipped in oil, and afterwards well rub-
bed with a view to render the dissipation of the ether slower, it
left .a solid coating of varnish with a beautiful gold tint : \yljea
Spread over wood not immersed ia uil^, it l^ft a coating which re»
sembled pale gold.
206 TREATISE ON VARNISHES.
Fifth Species of the same genus. Fat vaniish of a
gold colour.
No. XXVII.
Take Amber, prepared according to my method,
8 ounces.
Gmn lac 2 ounces.
Drying linseed oil 8 ounces.
Essence of turpentine 16 ounces.
Dissolve separately the gum lac; and then add the
amber, prepared and pulverized, with the linseed oil
and essence very warm. When the whole has lost a
part of its heat, mix in relative proportions tinctures of
anatto, of terra mérita, gum guttœ, and dragon's blood,
as mentioned page 142. This varnish, when applied
to white metals, gives them a gold colour.
Sixth species of the same genus. Fat varnish, which
may serve as a mordant to gold, and at the same
time to dark colours '*.
No. XXVIII.
Take Boiled linseed oil 16 ounces.
Venice turpentine 8 ounces.
Naples yellow 5 ounces.
Heat the oil with the turpentine, and mix the Naples
yellow pulverized.
* The varnish No. XVI, of the third genus, that is to «ay, with
essence^ is also a mordant.
m
FIFTH GENUS.- -207
Remarks.
Naples yellow is an oxide of lead, the composition
of which will be giyen when we come to treat of colour-
ing substances*. It is substituted here for resins, on
account of its drying quality, and in particular of its
colour, which resembles that of gold. Great use is
made of this varnish in applying gold leaf.
The yellow, however, may be omitted when this
species of varnish is to be applied to solid and coloured
coverings. In this case an ounce of litharge to each
pound of composition may be substituted in its stead,
without this mixture doing any injury to the colour
\vhich is to constitute the ground (/a teinte dure).
There is still another species of varnish, which, like
the above, might form a part of those of the thii'd
genus, if the matter which serves as the basis of it did
not require a drying oil to be employed : it is that of
caoutchouc.
Sixth species of the same genus. Caoutchouc varnish.
No. XXIX.
Take Caoutchouc or elastic résina
Boiled linseed oil - - /'ofeach 16 ouncesj
Essence of turpentine - ''
Cut the caoutchouc into thin slips, and put them
ante a matrass placed in a very hot sand bath. When
the matter is liquefied, add the linseed oil in a state of
* See Part II. Cb^p. I,
20^ TREATISE ON VARNISHES.
ebullition, and then the essence warm. When ther
varnish has lost a great part of its heat, drain it through
a piece of linen, and preserve it in a wide-mouthed
bottle. This varnish dries very slowly; a fault which
is owing to the peculiar nature of the caoutchouc.
Remarh'^.
The solution of tins singular substance is not con-
fined to essential and fat oils. Macquer applied ether
to it v\ith success* ; but the processes he indicates do
not always answer, and cannot form a part of those
which we are desirous to place within the reach of the
public in general.
In repeating these experiments, I found that the
union of caoutchouc and ether did not manifest itself
till the volume of that fluid was reduced one half by
.the effect of evaporation. It appears therefore that
ether exercises a better action on this substance accord-
ing as it hsG less tenacity, and as it approaches more
to the oily nature. In consequence of this principle,
the best rectified ether refuses to form any kind of
union with caoutchouc. This, perhaps, is the che-
IPÛcal reason proper to be adduced in order to account
for the difference between the experiments of Macquer
and those of Berniardf.
The invention of air balloons led to the idea of ap-
plying caoutchouc to the composition of varnish. It
t/as necessary to have a varnish which should unite
* See Mémoires de 1" Académie des Sciences, 1/63.
f See llic article- Caoutchouc.
FÎFTîi GENUS. 209
great pliability and consistence. No varnish seemed
capable of corresponding to these views except that of
caoutchouc ; but the desiccation of it is exceedingly
tedious.
. The formula which I present is the same as that
indicated in the Journal de Physique for April 1781.
I only modify the process by omitting the long ebulli-
tion of the essence over the caoutchouc. By my
method the solution is speedier, and less of the essence
is lost.
I cannot conclude this chapter without remarldng,
that there is even another species of varnish belonging
to this last genus, the use of which is very extensive ;
and which, no doubt, would occupy the first rank,
were it considered in regard to its utility : it is that
Vhich results from a mixture of tar, black pitch, rosin,
tallow, and sometimes even sulphur, and which is
employed for covering the outside of ships, boats, and
barges. This varnish preserves them from the influ-
ence of the water, retards their desttuction, and pre-
vents the velocity of the vessel from being lessened by
the additional weio-ht which would be communicated
He . .
to it nf the water were imbibed by the wood. This
varnish then contributes as much to the celerity of th®
vessel as to its preservation.
C 210 3
CHAPTER IV,
ùcnerat olaervai'ions and precepts respecting the prêparatiùrt
of varnish on a large scale. Description of an alembic nif It
a lalneum mariœ, the use of which prevents ale those ac-
cidents that frequently acconrpany the making of varnish.
The division I have made of varnishes into five genera,
each sub-divided into its species or varieties of composi-
tion, rendered it necessary for me to place after each
formula the remarks that seemed peculiarly applicable
to it. There are others, however, of a more general
nature, v.hich seem to belong to the whole art, and
which ought to be given by themselves.
All the arts have had their state of infancy. The
progress of them has been the result of repeated triars,
and sometimes of errors ; but, for the most part, they
are extended by accident. It is on these frail and un-
certain bases that those arts which relate to the most
necessary objects have been established. A lorrg repe-
tition of the same processes has at length thrown light
on their progress ; and in this manner the first el!^nent&
of them have been acquired.
That of the vamisher could not speedrly attain to its
highest degree of perfection. Its origin depended on
thai of public wealth, and on the extinction of those
wars wliich covered Europe v/ith ruins : it depended
on the extension of commerce, which increases the
(enjoyments of life, inspires a taste for superfluities, and
multiplies our wants. An industrious people, attached
OBSERVATIONS AND PRECEPTS. 211
to the aits, and confined to the eastern extremity of
Asia, furnished us with the models. The European
industry, and particularly that of France, acquired a
stimulus ; it invented combinations ; mixtures were
muldplied ; and the results, though still imperfect, af-
forded sufficient encouragement to ardsts. New at-
tempts opened a more successful path ; the principles
of the art were discovered, and these were followed by
formula and descripdons ; cridcal examinadon deter-
mined the choice of them ; and the art was at length
established on a solid basis.
All resinous or gummo-resinous substances are the
only essential bases of varnishes. Every spirituous
liquor, resulting from vinous fermentadon, and freed
by recdficadon from its superabundance of foreign
water, such as pure alcohol (spirit of wine); every es-
'sential oil extracted from plants by disdllation ; and
even every fixed or fat oil, obtained from certain fruits
by contusion or expression, are the only matters which
can be employed as an excipient or vehicle to the resi-
nous or gummo-resinous substances destined for var-
nishes.
Perfect transparency, and even limpidity and lus-
tre, are, in the last result, the essential' qualities in the
composidon of varnish. There are others, however,
equally important, such as those of drying speedily,
and giving solidity to the resinous stratum which serves
as a glazing to the bodies it covers. A composition of
this kind must at the same time be colourless, in order
that it may not weaken or disfigure the dnts of the co-
lours, which it ought on the contrary to call forth h\
p 2
212 TREATISE OKI VARNISHES.
their full brightness, by preserving them from the in-
fluence of the air and of moisture.
From this correct view it may readily be conceived,
that it is not sufficient that a substance should be of a
resinous nature, pure and without any mixture of fo-
reign bodies, and that it should be entirely soluble in
the liquid intended for the composition of varnish : ta
be entitled to a place among those destined for this pur-
pose by use and experience, it must also have very little
colour.
There are many substances, indeed, which are re-
jected on account of their sofdsh consistence, such as
sagapenum, galbanum, &c. as v/ell as of their colour,
which would spoil that of the compositions. This would
be the case with the resins called bdellium, guiacum,
ivy gum, gum ammoniac, and olibanum, though the
last two dissolve entirely in alcohol. Some of these
J
substances did not escape the notice of those who hrst
made experiments in regard to varnishes ; but they
soon discovered the inconveniences with which they
were attended.
The choice, therefore, is very much limited ; and it
miglit still be confined within narrower boimds, with •
out doing much injury to the art. Gum sandarac, em-
ployed formerly by the Arabs for this purpose, v/as
the only matter which seemed likely to ansvv^er the pro-
posed end. It is easily prepared, and possesses lustre;
but it is attended with the disadvantage of a little dry-
ness, which however may be corrected. On account
of the preference given to it over other resinous pro-
OBSERVATIONS AND PRECEPTS. 213
-ducts, and the eftects it produces, it has been jdistin-
guished by the name of veriiioc.
Turpentine, and all the modifications of it by the
effect of evaporation ; mastic, which has more solidity
than sandarac ; gum anima, and gum elemi, gum lac,
and copal, compose nearly the catalogue of the matters
which are employed for the composition of drying var-
nishes, or those made with alcohol. The extreme
' dryness of some of them is corrected by uniting them
with others which are less dry, and which still re-
tain a portion of essential balsamic oil, such as gum
elemi, gum anima, camphor, and turpentine. The
same effect is produced also by substituting instead
of alcohol a less dry fluid, such as essence of tur-
pentine.
Industiy, however, which readily takes advantage of
every thing that can answer its purpose, and which ex-
.cites the desire of the consumer by the variety of the
■objects it presents to him, has found means to subject
the art to modifications, by extending the processes in
some peculiar circumstances which seem to favour it.
A great step was, no doubt, made by giying to the
compositions of varnish lustre, transparency, a drying
property, and freeing them from al-l colour; but when
the grand models exhibited by the Chinese trade were
exposed to view, this was not sufficient. The use of
'the European varnishes, in consequence of the nature
-of the principles of their composition, was limited to
dressing-boxes, and other small articles which served
for the decoration of apartments. But the spirit of
imitation, which in France more than in any pther
P 3
214 TREATISE ON VARNISHES,
country excites genius and leads to di^oyeries ; the
innate taste for novelty, so prevalent among that na-
tion ; that continued fickleness, vi^hich often condemns
to oblivion master-pieces about to be succeeded by
others ; and that perpetual fluctuation of fashions and
inventions, soon became the most active causes which
contributed towards the improvement of the arts of
luxury.
To the same causes we are indebted for the origin of
the art of making boxes and toys of papier mâché cor
vered with varnish ; that of gilt leather, w^hich the na-
tional fickleness seems to have banished to England ;
that of coach-making, which laid painting of every
kind under contribution. All these arts called in tp
their assistance that of the varnisher, and gave to it a
very great extent. Hence the discovery of coloured,
changing varnishes ; of very durable varnishes, in the
composition of which the artist has been able to over^
come the resistance opposed by copal and amber to
their usual solvents : hence also the use of resinous
colouring substances; such as terra mérita, gum gutt?e,
dragon's blood, saffron, sandal wood, anatto and
others.
Experience has set bounds to the number of the lir
quids proper for serving as vehicles in the composition
of varnish. The nature of alcohol was suited to light,
drying, and colourless compositions, when artists were
desirous to correct the strong odour which accompa-
nies most varnishes.
In examining the essential oils, artists must have first
distinguished those wliich on account of their lightness
^ OBSERVATIONS AND PRECEPTS. 215
seemed to exhibit intennediate qualities between alcohol
and oils of the greatest consistence : hence the use of
essence of turpentine, oil of spike, and oil of lavender.
Essence of turpentine gives to varnish more body
than alcohol : it might indeed be substituted in all cases
for alcohol, if the strong odour it emits were not, to
some persons, a cause for rejecting it. For varnishes,
however, destined to be applied to ceilings, wainscot*
ing, and furniture, it is far superior ; because it renders
them equally brilliant, and gives them more durability.
During the summer, in particular, this odour is soon
destroyed ; and if the artist takes care to employ an
alcohol varnish for the last stratum or glazing, there
will be no odour at all.
The use of essential oil of lavender is more applicable
to delicate oil painting than to the art of the varnisher.
Though naturally drier, next to essence, than essential
oils, it is still too fat and unctuous for varnishes. It
may, however, be introduced in small doses in the
composition of varnishes made with alcohol and es-
sence of turpentine, when it is necessary to lessen their
drying quality, or when metallic colom^s are used in
'■ the state of pure oxides.
The other essential oils known in commerce are ei-
ther too dear, or too fat, or too much coloured, to form
part of the liquors destined for the solution of resins.
The number of the fat or fixed oils useful to the art
is as much limited as that of the essential or volatile
pils. Oil of white poppy seed, called improperly oil
I of pinks, nut oil, and linseed oil, are the only ones
found by experience to be fit for the composidon of fat
JP 4
216 TREATISE ON VARNISHES.
varnishes, when they have undergone preliminary pre-
parations vhich deprive them of their unctuous quality,
and render them drjûng. Olive oil would answer the
purpose of the artist better than nut oil or linseed oil,
which are always coloured, if nature, which presents it
without much colour, had not communicated to it an
unctuous matter, which can be removed only by de-
stroying a part of the oil itself. The case is the same
with oil of turnips and oil of hemp seed ; and the pro-
cesses to which the seeds of the beech tree are subjected
before the oil is expressed from them, give it a red co-
lour, which renders it unfit for varnish.
To judge, then, from the results alone, varnishes,
such as they are exhibited by our five genera, are no-
thing but solutions of pure resins, or resinous gums, in an
appropriate spirituous or oily liquid. Acid liquors,
therefore, and alkaline liquors, though the latter have
the property of combining with oils and with resins,
and of reducing them to the saponaceous state, are in
no case endowed with the essential qualities requisite for
the composition of varnishes.
The eSect of chemical dissolution ought to be distin-
guished from that of simple solution. The views of the
chemist are very different from those of the composer of
varnish. The former employs every mean to facilitate
the separation of the principles of bodies, that he may
examine their ultimate and peculiar nature, and reduce
them ' to their greatest state of simplicity, for the pur-
pose of afterv/ards assigning to them that place which
they ought to occupy in the order of created substances.
The varnisher, on the other hand, endeavours to pre-
OBSERVATIONS AND PRECEPTS. 217
serve the integrity of the substance on which he ope-
rates. His means are simple ; they act only superfi-
cially, by analogy of composition : in a word, they
effect merely solutions, the ultimate result of which is
confined to extension of the integrant resinous parti-
cles. By uniting all the advantages of a mechanical
division, as extensive as the object requires, the resi-
nous substances subjected to the action of the agents
■w^hich the varnisher employs, lose none of the princi-
pal characters which render them proper for the com-
position of varnish ; namely, transparency, durability,
inflammability, and lustre.
If saline, acid, and alkaline liquors, considered as
solvents, are incapable of answering the views of the
varnisher ; water, a simple substance, without odour
and almost without savour, is no less contrary to them.
It is the nature of resins to resist its action. Water also
has the property of seizing on the alcohol which holds
a resin in solution, and of precipitating the latter under
the form of a white powder. These effects, which are
the more certain as they depend on the particular na-
ture of resins, as well as on invariable chemical proper-
ties, require the most scrupulous attention on the part
of the artist, in regard to the choice of the alcohol he
intends to employ in his compositions. The bcst brandy,
and even alcohol superior to brandy, if inferior to the
•degree of purity indicated in page 60, are unfit for
•maldng varnish. The foreign v/ater which these hquors
contain forms an obstacle to the solution of resins ; and
it precipitates the resinous portion which the spirituous
part has been able to dissolve by tlie aid of caloric
218 TREATISE ON VARNISHES.
(heat). The solution is at any rate turbid, and very
little susceptible sf claniîcation. Even if we should
suppose that the spirituous part is still powerful enough,
considering the quantity, to effect a sufficient though
incomplete solution of the rerin, the varnish resulting
from it would be liable to become mealy, and to crack.
Tliis infallible result may serve, no doubt, to ex-
plain the seventy with which Wadn exclaims against
the wasliing of certain resins in water, — a process re-
commended by the author of the Parfait Vernkseiir,
But however specious the reasons with which he en»
deavours to justify his opinion may be, it is no less
certain that some resins require to be washed before
they can be employed in the composition of varnish.
Masdc, sandarac, and even copal itself, which is di-
vided into small portions, &c. require previous wash»
ing, which is attended witi: no kind of inconvenience.
The case would be the same with amber, were not this
precaution rendered useless by the proce3S to which it
is subjected.
These resins are immersed in water after the fine
pov/der has been separated from them by a hair sieve.
The fragments and resinous tears are then rubbed be?
tween the hands to detach the dust, the lighter parts,
and the fragments of bark. These separated parts float
on the surface ; and, in consequence of their lightness,
afford the means of removing them with facility. The
washed resin is then spread out on a piece of dry linen
cloth, or a hair sieve, which is covered with a sheet of
paper ; and the whole is exposed to a current of iiir to
dissipate the moisture, Resins washed in this manner.
OBSERVATIONS AND PRECEPTS, 219
and well dried, are much fitter for the composition of
varnishes than those which have not been subjected to
the same operation.
. A few more precautions are still necessary in com-
posing delicate varnishes, such as those destined fo?
valuable paintings and other objects of luxury. It will
be proper to separate the pure resinous tears from those
"which are stained, and which even are accompanied
with portions of the bark of the tree that produced
them.
On the neccssitij of a reduci'ion in ilic formuuc.
Watin seems to be the first author who was fully sen-
sible of the necessity of reducing the formulae to a small
number of substances. But, notwithstanding the ad-
vantage attending this step towards improvement, many
things of importance still remain to be done. By pro-
secuting, for example, a series of experiments on ths
different resinous substances with alcohol of a known
(degree of purity, one might form a table of solution,
which would be exceedingly useful to the operations of
the variiisher ; because by knov/ing the kind of resin
about to be treated, and the degree of the purity of
his alcohol, he could immediately determine the doses
of the substances proper for the intended composition.
There are, indeed, some resins more soluble in al-
cohol than others. This labour, which would save
expense, and perhaps time, is worthy of further re-
searches.
The most experienced artists will long be reduced to
tlje necessity of judging by simple approximation, and
220 TREATISE ON VARNISHES.
according to the old formulae, of the relative quantities
of the resinous substances destined for the preparation
of varnishes ; and, for fear of sacrificing utihty to ceco-
nomy, they will continue to employ more matter than
the object requires.
Of the choice of the matters.
The goodness of varnish depends not only on the
choice of the soluble matters, but also on the state of
the liquors which are to become charged with them.
That oily consistence, which is the first character of a »
varnish, before it be emploved, deoends on the na-
ture and purity of the liquid, and on the extent of its
power over the resinous substance. A varnish may be of
an inferior quality, though the vehicle is charged with >
as much resin as it can take up. The excellence of alco-
■ hoi cannot be determined merely by the sight ; and for
this reason I have enlarged on the means best calculated
to serve- as a guide to the artist and am.ateur on tiiis
point, which is of the utmost importance.
A knowledge of the nature of essential volatile and
fixed oils is much less difficult to be acquired. A skil-
ful eye can easily distinguish the external characters
which belong to each of them. Their smell, colour,
and a certain degree of connection between the mole-
culœ, which communicate to them the oily consistence,
are unequivocal signs to determine the artist's choice.
To these may be added, in cases of uncertainty, the
indications we have given in treating of each of them
^separately.
.Such are the guides in which the artist ought to
OBSERVATIONS AND PRECEPTS. 221
place confidence in regard to the composition of var-
nish : by these alone he can hope to obtain success.
But whatever efforts may be made to produce a max-
ijiium of solution in the mixture of the matters, he can
attain only to a point of saturation proportioned to the
nature of the resins, and to the present state df the
liquors employed. When people are nice in the choice
which they have to make, the principal object is ac-
complished.
Of the respective doses of the dry and liquid suhiance,f
employed in the composition of varnish.
The art, however, is still imperfect, if the practical
part be confined merely to the choice of the substances.
Too great a number of them, as well as too great
doses, embarrass the artist in the account which he
ought to give to himself of the expected results. Every
art founded on a collection of formula; attains to suc-
cess only by a very slow progress. To simplify the
formulas, great knowledge and long experience are ne-
cessary. One m.ust be able to rise above difficultés,
and even criticism, in circumstances when the formula;
compel him to follow habit, or when habit gives weight
to formulae. * -
By simplifying the compositions, and reducing them
to a small number of substances, it was easier to follow
the effects, and to discover the causes of them : re-
searches then became less painful and less expensive.
A great deal has been done in this respect, and for the
most part in a wrong direction ; but as long as artists
were the only guides and regulators, the success was
222 TREATISE ON VÀRNI5KES* -
very doubtful. If the celebrated aitist whom I have often
quoted was able, by his judicious obseiTations, to make
people sensible of the utility and even the necessity of
reformation, and of reducing the formulae to a small
number of substances, he did not place the art beyond
the need of further ad\ice : more was necessary to be
done, by reducing the number of matters, and redu*
eino; also the doses*
It is well ascertained, that the best alcohol cannot
become charged with more than a third of its weight
of the resinous substance, even when the most soluble
is chosen. A temperature capable of bringing it to a
state of ebullition may give more extent to the solu-
tion ; but cooling soon restores the equilibrium of sa-
turation. The varnish soon becomes turbid, and the
resinous matter which rem?iins in excess at that point
of saturation is precipitated, and, under the form of a
crystallization, lines the interior sides of the vessel.
Some of the fbrmulse given in the best works still
prescribe, in dry matters, a weight equal to tv/o-thirds
of that of the excipient. The doses indicated in th&
diftei'ent genera of my varnishes are more than sufficient
for the prescribed quantides of liquid ; since there still
remains a considerable part whichr^scapes its action. In
all cases, the process is less enibarrassing, and m.ore
secure from those accidents which are the consequence
of a mixture too much charged, and which forms 3
mass ; and is certainly less expensive.
OBSERVATIONS AND PRECEPTS. 22S
Of the effects of mechcinical division on rcsi}is ivJdck
oppose the greatest resistance to solution.
We are acquainted with some resins, , such as gum
sandarac, copal, &c. which seem to resist more than
others the action of the dissolving liquors. Copal, in
particular, exhibits this character, when the artist en-
deavours to dissolve it in alcohol or essence of turpen-
tine. This difficulty, however, may be overcome, with
greater or less ease, by diminishing the doses of these
substances. Simple mechanical division, carried as far
as possible, and the mixture of a substance which rea-
dily suffers iiself to be attacked, such as mastic and
white incense, facilitate solution in a degree which
could not be expected, if the two substances were
treated separately, and in the usual manner. Experi-
ence alone can determine in regard to this point. We
have already seen that camphor produces a great effect
as an intermediate substance, but the doses must not
be carried to excess.
Of the use of pounded glass.
When one is obliged to operate on a certain mass of
matters, the form of the vessel employed is a m.atter of
some importance. It is often different from what it
ought to be. Its capacity is not always suited to the
quantity it is destined to contain. In this case, the first
impression of the calonc (heat) tends to agglomerate
into one or more masses the whole resinous part àe^
stined to form the varnish, and by these means thwarts
224 Treatise on varnishes.
the intention of the artist, who employs his utmost
care to favour and maintain that state of division v/hich
is so well calculated to promote speedy solution. When
one is contented with simple stirring, which may op-
pose the union of the resinous parts, and even when
broad-bottomed vessels are employed, this object can-
not be accomplished. But the consequences of this
inconvenience may be greatly diminished by employing
a determinate quantity of pounded white glass Vv'hich
has been sifted through a hair sieve. It is mixed with
the pulverized matter before it is united cold with the
alcohol and the essence ; and the division of the parts
may still be assisted by stirring it \^ ith a rod of vvhite
wood, rounded at the extremity. By this simple me-
chanism the matter is kept in that state of divison ne-
cessary for the promptitude and perfection of the solu-
tion ; and the tumefaction of the liquid, a circumstance -,;
much to be dreaded in the process of making varnishes, T
is prevented. Besides, the weight of the glass, wliich
is greater than that of resins, makes it fall to the bot-
tom of the vessel, where it presents an obstacle to the '
adhesion of the softened matters.
The use of a balneum miaricC is preferable to that of'
a sand bath in operations of this kind, because the ^
temperature of the former has a certain fixed point of
elevation, v» hich it is impossible not to exceed with a
sand bath ; and in this case there will be great danger
of communicating to the varnish a foreign colour, ari-
'sing from the alteration which the resins experience
from too great heat. After the operation, mere or lest
ÔBSËRVAtlOKS AND PRECEPTS. 225
tàf the resinous substance remains mixed \\'ith the glass.
This residuum is reserved for the composition of com*
mon varnishes, which may be treated over an open firç.
Of clarification.
When the water of the balneum marise has been
kept in a state of ebullition for a full hour and a half,
if the matter of the composition amounts to no more
than forty-eight or fifty ounces, there is reason to be-
lieve that the solution of the resins is complete. The
circular motion with the stick must, however, be still
maintained for half an hour after the vessel has been
removed from the balneum maris. The whole is then
left at rest, to give the undissolved matter time to be
precipitated. Next day the clear liquor is decanted^
and then put into proper vessels. Some artists strain,
the varnish, still V\^arm, through a piece of linen cloth,
and then leave it at rest for a few days to clarify.
In both cases, when it is supposed that the excipient
is completely saturated with resin, it must be left for
some days at rest. The effect of a high temperature
is to dispose the vehicle to become charged with a
greater quantity of the substances than it can retain
when cold. I'his portion in excess is then precipitate-d,
either in whole or in part, according to the season =
When tlie precipitation is pretty extensive^ small lum.ps
of resin are formed around the Vvj^-sel. This abandoned
resin often affects a very distinct order of crystallization.
Somefimes the precipitation is not so sensible: the var-
nish remains a long time turbid, in consequence of the
separation of a portion of resin, which continues in, a
Q
226 TREATISE ON VARNISHES.
State of suspension. When this happens to be the case,
there are two methods of giving to varnish all that Hm-
pidity which it is deprived of by the portion of sus-
pended resin: add to it a warm excipient; this addition
dilutes the varnish a little : or it may be filtered through
cotton.
OfJUtration througli cotton.
This operation is simple. Arrange several funnels
in as many appropriate receivers (çec Plate V.Jig. 4.),
and place in the pipe of each funnel a small ball of
carded cotton, about an inch in thickness; press this
ball towards the point of the cone, to squeeze the cot-
ton together, and place over it a small plate of lead
pierced with several holes. Fill the funnels with var-
nish, and lay over the vessel a glass cover, or a few
sheets of paper. The varnish which passes through
the cotton is at first not very limpid; but when the
cotton has imbibed a sufficient quantity the liquor
passes very clear. The first portion of filtered varnish
is then poured again into the funnels; and the filtra-
tion being continued, the result will be a very bright
varnish, which is put into clean bottles. This filtra-
tion, which is soon performed, is indispensably neces-
sary for every kind of varnish destined to be applied
to delicate articles, such .is cut-paper works, valuable
furniture, paintings^ phlloso^; hical ins-;umen*:s, he. Care
must be taken to keep the funnels full, and particularly
not to leave the cotton uncovered; tise it would be-
come incrusteJ with a stratum of dry varnish, which
iTvight impede any further filtration.
OBSERVATIONS AND PRECEPTS. 22?
When the whole is filtered, it will be proper to wash
all the vessels with alcohol or warm essence of turpen-
tine, according to the nature of the excipient. The
product of the washing is kept in reserve till a new
-quantity of varnish is made.
On the preparation of varnishes in open vessels, and
the precautions they require.
The varnishes, of which we have here given the dif-
ferent formulas, are reserved only for articles of a cer-
tain value, and require particular care in the prepara-
tion. Those who prepare varnishes make other com-
positions which they destine, in general, for wain-
scoting, ceilings, common furniture, &c. Some pre-
pare them in open vessels, and in the open air, in con-
sequence of the accidents which sometimes take place
when alembics are employed. It is indeed much easier
to save from inflammation a matter which is seen to
rise, than one inclosed in metallic vessels, where its
tumefaction is not observed.
This labour on the first view appears to be easy. It
however requires practice and perseverance to obtain
the required result without any accident, and to quiet
the well-grounded fears which those in the neighbour-
hood may conceive of the danger likely to arise from
this process. It will be proper to perform this opera-
tion in the day-time, and in the middle of a spacious
court or garden. The vessel ought to be furnished
with high edges, that the ton-ent of vapours which
escapes may not communicate with the undulating
flame which often extends beyond the fire-place. Gare
Q 2
228 TREATISE ON VARNISHES,
also must be taken to dispose the vessel in the furnace
in such a manner as to cover the fire entirely, and to
prevent any portions of the varnish which may be
thrown up by a false movement of the spatula fromfall-
ing into it.
The precautions to be observed, however, are not
confined to the manipulations usual on such occasions.
When the solution is completed, it is customary to de-
posit the varnish in an apartment or workshop to cool,
and also to give it time to clarify. This apartment
then becomes filled with vaporific emanations, to which
fire may be communicated by an inflamed body. These
vapours are the more dangerous as they extend them.-
selves to a great distance, even beyond the apartment,
so that the contact of a hghted taper m.ay occasion an
explosion which will carry the flame to the reservoir
of the evaporating substance. I have witnessed, along
with a great number of auditors, a similar efi'ect, w hich
is often accompanied with very alarming circumstances.
Great care then must be taken not to enter with a
candle into an apartment which may contain such an
inexhaustible source of vapours, so highly inflam-
mable.
If the method of making varnish in open vessels
seems to hold forth some advantages, it is not free from
inconveniences. The artist, indeed, may carr)'^ on his
operation in more security. He can easily prevent the
iumefaction of the matter, and consequently ihose acci-.
dents which result from it. By means of continued mo-
tion he ma}' easily afford means of escape to the vapours^
in a state of expansion; and may rcnevv- the surfaces of
OBSERVATIONS AND PRECEPTS. 229
the resin which touch the bottom of the vessel, and
wliich, by being altered, might colour the varnish.
This is the favourable side of the method j but I shall
exhibit also the reverse.
This process occasions a very great loss of alcohol or
of essence, in consequence of the vapours which rise
from the mass. These vapours are furnished only by
the more subtile part, or th-it fittest for the solution of
resins, and which contributes most to the excellence of
the varnish, to its pliableness and lustre. The physical
effect which the constant vapour of the essence may
produce on the nerves of the artist exposed to it, if
he is of a weak constitution, is not a matter of indiffe-
rence; since it sometimes occasions a slate of asphyxia.
However great may be the precautions taken in pro-
cesses of this kind, if they have not always been suffi-
cient to prevent serious accidents, this is sufficient to
justify the fears of individuals who reside in the neigh-
bourhood of the varnisher, and to excite the vigilance
of the police to confine to the outskirts of cities all
establishments of this kind. Geneva never reflects
without terror on the fires which have taken place on
different occasions, and on the misfortunes which have
thence resulted to individuals. I consider it therefore
as my duty, since I am treating on varnishes, to en-
deavour to find in the form of the vessels and appa-
ratus means proper for obliterating the painful remem-
brance of these public calamities, or at least of render-
ing them less frequent.
Q 3
230 TREATISE ON VARNISHES.
Descriptioii of an alembic proper Jor the preparation
ofvarnish.
The common form of an alembic will not admit us
to hope that the solution of resins can be rendered
complete, and that those accidents which arise from
agglomeration of the resins, and particularly from an
accumulation of the vapour which in that agglomera-
tion finds a resistance which it endeavours to overcome,
can at the same time be prevented. The matters then
become tumefied, raise up the capital, spread with an
explosion to the fire, often even to the artist, and in
this manner occasion conflagrations. The smallest ac-
cident which results from the use of a common alembic
is the coloration of the varnish, in consequence of an
alteration which the resins experience, by adhering to
the bottom of the vessel. These effects v.'ould not take
place if the form and construction of the alembic af-
forded the artist the means of maintaining a circular
motion, which would cîiange the points of contact of
the inclosed matters; and if, instead of fire being ap-
plied to these matters in an immediate manner, it were
applied mediately, as is the case when a balneum
mariae is employed. These two conditions appear to
me to be answered by the construction of the apparatus
here described (jsee Plate V.Ji^. 1.).
It is an alembic and a balneum marias with a re-
frigerator. It consists, 1st, of a common alembic;
2d, a balneum marias ; 3d, a capital ; 4th, another
separate piece which performs the office of a refrige-
OBSERVATIONS AND PRECEPTS. -J^yl
"ïator, and which is adapted to the alembic at the mo-
ment of the operation.
The alembic «, fig. 1 , is of copper, and made in the
usual form ; the aperture h terminates in a tube, de-
stined to receive the pipe of a funnel, for the purpose
of affording an escape to the incoercible vapours which
arise from the water in a state of ebullition. This
piece then serves as a receptacle for the water of the bal-
neum mariae.
To this alembic is adapted the balneum maiise c, made
either of tin or of copper; it has the same form as that
of the common alembics, and serves to contain the
substances which are to compose the varnish. The
bottom of it is horizontal, perfectly jflat, and about an
•inch less in diameter than the mouth. The upper part
of this piece is strengthened by a circular band, which
serves to cover the joining where the capital is fitted to
'the alembic. To save expense, this circular band may
• be made of lead.
The diameter of the capital d, at the base, is propor-
tioned to that of the balneum mariae, in such a manner
"as to join with the circular band. This piece terminates
in a dome, which at the summit has a pipe or aper-
ture e, half an inch in diameter. A metallic bar f,
fig. 2, soldered at the two extremities, and pierced
with a hole corresponding in a vertical direction with
the aperture e, and having the same diameter, passes?
through the middle of the lower end of the capital.
These two apertures are destined to maintain, in an
exact vertical position, a small rod of iron ^, connected
■ on the outside with the handle A, which is of wood,
Q 4
232 TREATISE ON VARNISHES.
and moveable. The lower part of this rod, which
is continued to the bottom of the balneum maricC, is
furnished with an iron cross /, cut into teeth, while
its two extremities are raised up, as seen at k : the lower
part represents an inverted x« See Jig. 2 a)id 3.
In the upper part of the capital d, is formed a second
aperture /, which terminates also in a tube, capable of
containing a cork stopper. This aperture facilitates the
re-introduction of the parts of the liquid obtained by
distillation.
A conducting tube 7??, the diameter of which is twice
as large as that of the beak of common alembics, tak-
ing into account their capacity, proceeds from one of
the sides of the alembic. It is by this canal, which is
made of a sufficient length, and which is of an equal
diameter throughout, that the refrigerator n is con-
nected with the alembic.
The refrigerator h is constructed in such a manner as
to afford a free passage to those matters which might
become tumefied, or to condense the vapours which
escape from the interior part of the vessel. Both these
ends may be accomplished by means of a plain wooden
box, well joined together, pf an oblong %ure, through
which a tube o, made of copper, tin, or tin-plate,
passes in an oblique direction. This tube, throughout
its whole length, is of the same diameter as that Vv^hich
proceeds from the capital, and is only a continuation
of it. When ysed^ the box or trough is filled with
cold water.
The extremity of this tube terminates in a bent part,
py of the .san>e djarneter as the rest, Under this pajt
OBSERVATIONS AND PRECEPTS. 233
is placed the vessel q, destined to receive the product
of the condensed vapours, and, in case of need, th,e
matters which may be raised in the interior part of the
apparatus, by the effect of caloric (the he^it), or in
consequence of the consistence which the liquid acquires
in this kind of operation, or by the negligence of the
artist to stir it during the process.
This alembic is placed on a portable furnace of burnt
clay r, or on a fixed furnace constructed of bricks or
other materials: it oucht not to be too hip-h, lest the
artist should be incommoded in managing the handle h.
It has the same form as other furnaces, and is only
modified in the manner of placing the chimneys or
vent holes, which ought to be disposed in such a
m.anner as to be sheltered from the contact of the in-
flammable matters, that may fall on the edge of the
furnace. This end may be obtained by making the
c^Dcrtures of these chimneys issue through the sides of
the furnace, at the distance of two or three inches from
the upper edge, and forming over each of them a
small projection. The same purpose will be answered
by placing on a common furnace a ring, the edge of
which, s, extends about an inch beyond the exterior
- diameter of the furnace. This ring supports the alem-
bic. It may be made of burnt clay, or a kind of soft
Stone which is very common jn the neighbourhood of
Geneva.
Remarks.
Distillation is a process so common that any one
may conduct it. I might, therefore, pass it over in
silence j but when applied to the present object it re-
234 . TREATISE ON VARNISHF.S.
■ , «
quires, on fhe part of the artist, more attention and
more care than in ordinary cases. Nothing must be
neglected, if one is desirous of avoiding all reproach
in case any disagreeable event should take place. The
following then is the conduct I should observée in the
preparation of varnish, according to the method here
proposed : —
When the matters are put into the balneum mariai,
cover that part with its capital, and cause the agitator
to touch the bottom of it. Lute the two parts exactly,
at the place where they are united, with bands of paper
and flour paste. Then make a few turns with the
handle before heat is applied, to divide the matter ;
keep the tube b of the alembic open; and shut closely
the tube /. Adapt the refrigerator to the alembic,
and cement a few slips of paper over the place where
the two vessels are joined ; introduce into the alembic
such a quantity of water that the body of the balneum
marise may be half immersed in it, and then kindle
the fire.
It is of some importance to move the agitator, at the
moment when the fire is kindled. If this precaution
be neglected, the resinous matter forms itself into a
rnass, and in that state opposes more resistance to the
action of the vehicle. Continue the rotary motion
during the whole process, but without too much pre-
cipitation. The solution to be complete requires only
an hour or an hour and a half, reckoning from the
moment when the water begins th boil.
If the level of the water employed be fixed at half
the interior height of the balneuui maria', or a little
Il.T.
234.
.^
{"y/^
To fiontpane 234.
.^.../..
/n> ■ /Ay /> /r/ff./ 'f rf/'c '/' ''/ f e( '/ /fy(->/' ■
OBSERVATIONS AND PRECEPTS. 235
higher, the inconveniences attending too great a quan-
tity of that liquid will be avoided. By the force of
ebullitioxi part of it is thrown up through the tube,
and often incommodes the artist ; but there is still
a greater inconvenience. When the balneum mariae
is thus completely surrounded with a boihng liquid,
the vapour of which has not the means of free escape,
the alcohol, which becomes so much more charged
with caloric as it acquires greater density, in the
ratio of its union with the resinous part, tumefies,
and escapes as it boils up through the apertures which
it meets with ; and if it should unfortunately experience
the least obstacle to its forced emission, it would burst
the vessel, and inundate the artist with matters, which
being soon inflamed by their vapours coming into con-
tact with those that fall into the fire, would expose
him to the danger of losing his life amidst the most
excruciating pain, as has frequently been the case.
If the kind of alembic here described were destined
for various other uses, hke those in chemical laborato-
ries, there might be reason to apprehend the effects of
some negligence in regard to the care that ought to be
taken to keep the tube h open, when the distillation is
carried on with a balneum marise ; and to close it with
a stopper when distilling with an open fire, that is to
say, without a balneum mariœ. For the present pur-
pose there is never need of employing this alembic oa
an open fire : consequently the artist is not undeT the
necessity of shutting the tube, and by these means he
avoids those accidents already mentioned. In the con^
2S6 TREATISE ON \'ARNISHES.
tTdry case, the vapours of the boiling wat^r being accu-
mulated, and finding no way of escape, would soon
burst the apparatus, or would exercise a still greater
action on the matters in the bath than if the alembic
were filled with boiling water.
In proportion as the calonc (heat) acts on the sub-
stances inclosed in the balrjeum marias, it unites itself
to portions of the vehicle, which it reduces to vapours.
A part of these vapours are condensed in the inside of
the capital, and fail back on the mai:ter. Another part,
escaping from the interior of the apparatus, is con-
densed in the lateral tube, which traverses the refrige-
rator, and proceeds in a liquid form into the receiver.
This product is composed of the most volatile and the
most subtile part of the liquid employed for the solution.
This loss, if extended, diminishes in a considerable
degree the energy of the alcohol not volatilized : in a
word, the quality of the varnish would suffer by it, if
the product of the distillation, when a certain quantity
is collected, were not restored to the mass. The aper-
ture / is then opened, and a funnel of tin plate is
adapted to it, through v^rhich the liquor that has escaped
in the form of vapours is restored to the varnish. The
cork stopper is again put in its place ; and the circular
motion of the agitator is continued. I think it need»
le$s to recommend the utmost care that no portion of
the liquid introduced may be suffered to fall into the
furnace : artists must be v/ell aware of the conse-
ijuenccG.
Several compositions require the use of turpentine ;
OBSERVATIONS AND PRECEPTS. 237
but it must not be put into the bath at the same time as
the resins ; because, being more disposed by its liquid
nature than dry^ resins to combine Avith the alcohol, it
would occupy the whole of the latter, which would not
exercise on the other substances the energy requisite. The
mixture of it, therefore, must be deferred till towards
the end. It may be easily added, by melting it over a
«low fire, and introducing it in the same manner as the
product of the distillation. A portion of the disdlled al-
cohol is reserved for washins; the vessel which contained
o
the turpentine, and the funnel which has been em-
ployed.
When it is judged that the solution of the resinous
matters is finished, the whole of the fire is removed
from the furnace, and the circular motion of the agi-
tator is continued for half an hour, leaving some inter-
vals of rest. When the apparatus has in some mea-
sure cooled, a sponge dipped in water is drawn over
the pieces of paper v/hich cover the joints ; and they
are then removed as well as the capital, which has
been separated from the refrigerator. The varnish
I being then decanted into proper vessels, it may be
strained through a piece of dr\ linen, or filtered through
cotton.
This operation ought to be performed in the day
time, lest the inflammable vapours which may escape
should be set on lire by ihe candles. The artist, who
undertakes this labour with the precautions I have
pointed out, v/iil always be secure from those accidents
which, in this process, are attended with so dreadful
effects.
2SS
TREATISE ON VARNISHES.
It ought always to be remembered that alcoholic var-
nishes never should be prepared in larger quantities than
may be required for immediate use ; because they do
not long retain those qualities which render them valu-
able. When too long kept, they become yellow and
greasy. In this respect they are very different from oil
varnishes, which improve by time.
C 239 ]
CHAPTER V.
Olservations 07i the uifluevce wliich the solar light has to ren-
der essence of turpcfitine proper for the solution of copal,
so as to compose a durable and colourless varnish^.
Eve ry art which consists only in the employment of a
certain number of bodies has, no doubt, fixed bounda-
ries, and becomes more susceptible of modifications in
its processes than of hnportant discoveries. This may
be applied in the utmost strictness to the art of the var-
Disher. It consists only in the solution of certain re-
sinous substances in spirituous and oily liquors, which
however require some particular preparations.
It was not till within these few years that this art was
reduced to certain principles capable of serving the
artist as a sure guide in conducting his operations. In
this respect it has undergone ^ sort of revolution, for
which it is indebted only to that part of practical che-
mistry which has been brought to a level with the com-
prehension of artists. The necessity of gratifying the.
general taste in evei*y thing that regarded the decora-
tion and elegance of apartments, furniture, &c. was the,
first cause which tended to produce it ; and simple
compositions were substituted in the room of those re-
fcipes with which works that treated on the secrets of
jthe arts abounded. Each solution has its particular
* This forms the substance of a paper presented in 1788 to the
isociety formed at Geneva for the encouragement of the arts, agri-
buiture, and commerce.
240 TREATISE ON VAïtNISHEâ.
laws, depending on the nature of the bodies, and of the
liquors which seem to be suited to them. By reducing
this art, therefore, to a regular method, the extension of
it has been rendered more certain, or at least more pro-
bable ; and each discovery, supposing that any can be
made, will find a place marked out for it in the series
of formulae, the distinguishing characters of which lead
to a methodical division, rendered necessary by the-
present state of our knowledge* It was under this
point of view that Watin published, in 1772, his Art
of making and applying Varnishes.
Of the matters employed for the composition of var-
nishes, copal and amber are reser\'ed for those which -
require fat oils as their vehicle. At any rate, these two
substances have hitherto been considered as insoluble
m alcohol and in essence of turpentine*. The hard-
ness, purity, and transparence of copal have rendered
this kind of resin an object of many researches. Vari-'
ÔUS methods have been tried to dissolve it, but without
apparent success* The use of turpentine in the room
of alcohol gave only uncertain results. Some chemists
assert that they have made varnish in this manner ;
others say it is impossible. Artists who practise the
art of varnishing declare in favour of the latter opi-
nion.
This state of uncertainly, instead of making me ab-
stain from i*esearches on lliis subject, has, on the con-
trarv, rendered it more interesting to me, and more
worthy of examination. The advantage which might J
result from the discovery of some process capable of
communicating to varnish the intrinsic qualities of this
Kl'I'JiCTS or LIGHT Ols^ ESSENCE OF TURPENTINE. 241
-dry matter, held for.th a stimulus which it was difficult
to resist. I therefore undertook a series of experi-
ments on it, which form the subject of this chapter. An
artist, no doubt, would not have carried it to the same
extent ; but it was necessary for me to exhibit it under
another point of view than a mere formula, since the
iletail of the results necessarily leads to physical re-
searches absolutely foreign to the art of the varnisher.
I announced in the ardcle which treats of copal : 1 st,
that this substance is partly soluble in alcohol ; 2d, that
it may be endrely dissolved in it by means of an inter-
mediate substance ; 3d, that ether generally effects a
solution of it, and in pretty large doses, according to
the state of the ether, and the particulai* nature of the
copal ; 4th, that essence has the same property, but
with certain limitations, which seem to depend on a
particular state of density.
- The solution of copal in alcohol was not sufficiently
complete to affiDrd any hopes of a satisfactory result.
That which takes place by means of an intermediate
substance was attended with an inconvenience, which
• there was reason to think might be obviated in the so-
ludon that seemed possible by essence. The latter
vehicle exhibited in its physical properties characters
-nearly «imilar to those of alcohol. Like that fluid it is
exceedinglv limpid, liquid, and colourless. It possesses
-a mean density between that of alcohol and the density
■ of essential oils : in this even it seemed to have with
- copal an analogy more striking, and which might lead
- to effects of solution that could not be expected from
-alcohol. 1 confided, therefore, with the more reason
R
'242 TREATISE ON VARNISHED.
in the strength of this analogy, as the particular nature
of the essence permitted me to increase or to lessen at
pleasure its common density.
It was on these bases that I founded my researches.
The first did not afford me complete satisfaction. I re-
newed my experiments ; but the results still seemed to
be very imperfect. I sometimes found that the esssence
which had exercised a partial action on the copal pro-
duced no effect at a more elevated temperature. In
other circumstances, the same liquid which refused to
unite with copal laid hold of it with eagerness after an
interval of some weeks. At other times, mixtures of
copal and essence kept in a state of infusion for twenty-
four hours v/ithout exhibiting any apparent solution,
required only a maceration of some m.onths to display
all the characters of a complete solution of this kind,
and at length of a beautiful varnish. I observed also,
that of a certain number of matrasses which contained
mixtures of copal and of essence, in doses perfectly
equal, and which experienced no otlier difference
but that arising from their posidon in different parts
of the labr>ratory, several, some months after, exhi-
bited all the signs of a complete solution, \^'hile others
«howed no indicadons of it. I saw some also in Vvhich
the copal remained under the form of lumps, covere^
with an amber-coloured liquor.
i evidently foresaw, that to clear up so many doubts,
and to discover the truth amidst so much contradiction, a
great many ejqperiment.^ would still be necessary. ' I had, ||
however, reason to think that the solution of the copal \M^
dejenled on a certain stat ." of the constituent principles m^^
ÏFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 243''
of the essence. I was then sensible of the necessity
of mixing it with copal possessed of diiierent degrees
of tenuity or density, which might be communicated
to it by art ; and I expected I should be able to find
that point best suited to the solution of this kind of
resin, without communicating colour to the varnish.
The following experiments were undertaken in con-'
sequence of this new plan of research ; but I must ob-
serve that I always made use of the same copal, in the
state of powder, and of the same essence of turpentine.
1st. Liquors susceptible of volatilization at a certain
temperature always exhibit in their ascent products the
more attenuated, as they have required less caloric"
(heat), and consequently less time to be volatilized.
Such is the case with alcohol, the first product of which
is more subtle than the succeeding, •
Certain light essential oils are subject to the same
law. By applying to the rectification of essential oil
of turpentine the method empl-oyed for the rectifica-
tion of spirituous liquors, dividing the products into'
several portions, I had reason to believe, that those
which passed over the last would be less fluid, as well
as less ethereous, than the first ; and that the difference
observed in their respective densities would follow a
gradual progress, according to the different periods of
fhe distillation. As it was necessary that this labour
should be rendered so easy as to be within the reach of
artists, I was obliged to adopt a less complex process.
I therefore divided into six equal portions, by means
of a tubulated balloon, the product of seventy-two
ounces of essence of turpentine, disdlled in a balneuro.
k2
i?44 TREATISE ON VARNISHES*
marias, according to the method described in Chap. IL
Each of these portions was put into a numbered flask^
and the sixth flask was destined to receive the residuum
of the distillation.
It was necessary that I should first examine the spe-
cific gravity of each of these six portions, and compare
them in regard to their power over the copal ; but I
was prevented by a tedious illness, and other occupa^
tions of a more urgent nature, which left me no time
for chemical researches. I, however, took the precau-
tion to close the flasks exactly, and to shelter them
from the light by shutting them up in a closet, where
they remained nine months.
2d. At the end of that period I found four of the
flasks covered in the inside with beautiful crystalliza-
tioBs, consisting of prisms grouped together in a diver-
gent form.
No. 1. exhibited small needles, which crossed each
other in every direction. They were transparent, and
had a silky appearance. A great part of these crystals
covered the bottom of the vessel ; some also adhered
to the sides, below and above the level of the essence.
The most apparent of these crystals were 5-^ lines in
length.
No. 2. presented two pretty large groups of prisma-
ric ciystals, diverging from a common centre. The
largest were six lines, or half an inch, in length-
No. 3, showed only some rudiments of crystals, scat-
tered over the ^ides of the glass above the level of the
essence.
No. 4., besides small crystals adhering for the mo^
TirECTS OF LIGHT ON ESSEXCE OF TURPENTINE. 245
part to the sides of the glass, above the liquor, con-
tained three J^eautiful groups, in part divergent, and
< rossing each other different ways : most of these prisms
were half an inch in length.
No. 5. presented no crystals but at the botto;m of the
vessel. They were, however, so numerous that they
covered the raised part of the bottom. Maity of these
prisms were insulated ; others were disposed in diver-
gent radii, in such a manner that one prism ser\^ed as
a base to four or five others, which adhered to it only
in one very acute point. The largest did not exceed
three lines.
No. 6., which contained only the reddmim of the
distillation, and which had a strong amber colour, ex-
hibited no appearance of crystallization.
If these crystals really varied in rega'-d to their di-
mensions, the case was not the same in regard to their
form. In aM of them I observed the quadrangular,
flatted prism, with two large and two small faces. They
were prismatic lamin?e truncated horizontally. In some
ciystals the extremities were continued to a point.
Sd. These crystals, when taken from the essence,
and exposed on brown paper to dry, have very little
solidity. They dissolve in alcohol and in water, the
limpidity of which they destroy. There is separated
-from them a little oil, which floats on the surface.
This effect arises, no doubt, in a great measure from
the portion of essence with which they are still en-
veloped.
The solution of this salt exercises an action on blue
vegetable colours^ and makes them become red. It di4
R 3
246 TREATISE ON VARNISHES,
not appear to me to exert much energy on a solution
of carbonate of potash. The vehicle in which the salt
, was dissolved weakened its strength.
This solution, when presented to caustic potash,
becomes saponaceous, and small threads are formed
in it.
This concrete, volatile salt almost always appears in
an oil exposed to the influence of the light, though
. no cr)'stals are produced by cooling, or by its remain-
ing in a cold place. In this case, it is more disposed to
■fix itself above the level of the oil than below it. The
process which accelerates its formation consists in mak-
ing the essence pass over the upper and uncovered
• parts of the vessel. Evaporation has a considerable
share in the production of the phenomenon. But, if
a matrass half filled with essence, and which already
exhibits cr)'Stals in the part not occupied by the oil, as
well as in the bottom, br exposed to the ardent sun,
the former will almost always remain, and often even
increase, while those covered by the liquid dissolve into
a kind of reddish water, which falls to the bottom of
the vessel. This water is exceedingly acid. It effer-
vesces with alkalies, renders blue vegetable colours
suddenly red, and impresses on the tongue a caustic
and burning savour. The salt which produces it ap-
pears to be of a benzoic nature : a kind of crystalHzed
.acid soap.
The concrete, volatile, acid salt of the essence of
turpentine, covered by the fluid which produced it, is
susceptible then, in this pardcular case, of dissolving
jn water, in consequence of the same cause vvhicji
f.n-LCTS or LIGHT ON ESSENCE OF TURPENTINE. 247
makes it appear on the free sides of the vessel. A tem-
perature somewhat higher than that of the atmosphere
would be sumcient to separate the acid from the oil,
which ser\ es as a basis to the crystals. I do not know
whetlier these effects would be constant. I am, how-
ever, inclined to believe they would ; as I consider
them to depend on the reaction which the light favours
between the acid principle and the oily body. They are
those I observed on the six bottles I had exposed to the
sun ; and I have since observed them in a great num-
ber of similar cases. This phgenomenon of liquefaction,
■ however, was observed in crystals which had been
formed in the course of twenty-four hours above the
level of the oil, and under the oil ; and which I had
kept some time in the cellar, in vessels closely shut :
but the crystals which v/ere dry experienced the same
fate as those immersed*.
^- The Pharmacopcria of Charas, p. 107 and lOS, speaks of a vo-
latile salt of tuqjenline ; but, according to the old language of die- ■
mistry, it exhibits only as it were a substance concealed in oil, essen-
tial to its nature, and to which the author ascribes all the effects of
essential oil on tlie bladder. " The volatile salt," says he, " which
is concealed in the acid part of the ethereous spirit, and in the
oils lirst distilled, contributes greatly to the virtues ascribed to
them, the principal of which are, that they open the urinar}' con-
duits, moderate the heat of tliem, prevent tlie formation of cal-
culi, &c. &c."
In this passage we see nothing that indicates the existence of an
essential salt developed and crystallizable.
ï'oultier de la Salle enlarges a good deal on the distillation of '
ethereous oil of turpentine and balsam of turpentine, in the learned
.. obsqn'ations with which he has enriched the Translation of the
Pharmacopoeia b()7idinens}s. lie admits tliere an acid phlegm, as
R 4
248 TREATISE ON VARNISHES.
I did not extend any further my researches on the
nature of this salt, the acid of which appears to me to
approach very near to the nature of the benzoic acid ;
but, in the mean tim.e, it may be defined an oily, acid
salt, analogous to that extracted from balsams. The
volatile salt of amber, perhaps, might be traced back
to a similar origin ; and if its chemical properties seem
to be different, tliis may be ascribed to the influence of
the mineral vapours, which for so many ages have been
exercising an action on the resinous matter which con-
stitutes amber. These vapours must necessarily have
changed its principles, or brought them gradually to
that point of modification which removes amber go far
from the nature of our common resins, and even from
that of copal, which seems to approach it most, as I
have since shown;
I was perfectly sensible that it would be of great im-
portance to canry to a greater extent these researches
on an object so nearly connected with the natural his-
toi'y of fossil resins. I mjght have attempted a greater
number of experiments to discover the peculiar nature
in the distHlation of resins and balsams; but he makes no mention
of a Volatile, acid essential salt. If tliis concrete salt had been
observed, tliat valuable repositoiy of the Stalilean chemistry would
have noticed its existence.
When essence is distilled with a sand bath, if the retort be
revered with a dome of baked clay to facilitate the expulsion of the
vapours which circulate above the boiling liquid, this apparatus
contribates to the speedy appearance of this concrete salt, because
there is less reaction from the fire on the principles of tlie oil
'ï'w'ènty-four hourâ after the distillation of two pounds of esscnco
I was able to extract TJ grains of this concrete salt.
3
EFFECTS OF MGHT OH ESSENCE OF TURPENTINE. 249
of that salt, and to trace it in its different combinations
with difierent bases; but as this part is absolutely
foreign to the arts, I thought proper to confine myself
to a plain account of the phccnomena exhibited in the
course of some experiments, the only obiect of which
was the solution of conal in es:sence of turpentine.
4th. It appeared necessary to examine what might
be the specific gravity of each of the numbered divi-
sions of the oil, before J. applied them, to the copal. I
had only Romberg's hydrometer and common balances
at that time in my possession ; and I confess that these
instruments would not bear a strict comparison with
others since constructed for me by one of our artists,
well known to philosophers by his talents and inge-r
nuity. They were, however, suiTicient to convince me
that the degree of the tenuity of my specimens did not
follow a progression corresponding to the period of their
appearance in the course of the distillation. No. 4.
had a specific gravity less than No. 1., and the latter
was some grains heavier than the common essential oil
of the shops, which had been employed for the distil-
lation. The one last mentioned was to distilled water
nearly as seven to eight. I shall enter hereafter into
more circum.stantial details respecting the specific gra^
vity of similar producdons.
5th. This variety in the specific gravity of these dif-
ferent specimens of the same oil would not have stopped
liie, had these specimens been fit for that kind of solu.
lion which v.as the principal object of my researches^
but none of them could take up such a quantity of copaî
as was sufficient to make a varr.ish. The reacLer may
^50 TREATISE ON VARNISHES.
yddge of their degree of energy by the account of tiie
following comparative experiments which were all made
in small new matrasses.
Ten grains of pw-verized copal were mixed with an
ounce of each of these separate oils. Each matrass,
immei-sed in warm water, was kept for half an hour
in a state of circular motion; but under the present
circumstances, this process, which in other cases was
sufficient to dissolve 72 grains of copal in little more
than an ounce of essence, "was not capable of carrying
the solution, in each of these oils, to more than ten
gi^ains. No. I. approached nearest to the limpid state,
which announces a commencement of solution ; the
precipitate in it was less abundant. The other small
matrasses, distinguished by a number corresponding to
that of the flask from which the oil had been taken,
showed the copal collected at the bottom in the form
of a white glutinous mass, tough and tenacious. This
toughness and tenacity, which are not commonly ob-
served in the parts of copal treated with a lighter
and mare cthereous essence, indicated however that
these oils were disposed to operate the required so-,
lution,
Under this supposition, and in consequence of ob-
servations made in former trials, I closed exactly the
matrasses, as well as the bottles containing the speci-
mens, and left them for a year on one of the shelves
in my hiboratoi-y. Their siruation \a"-is such, in regard
to the solar light, that they received it only by reflec-
tion during four or five months of the year. I waited
a lonj]j time, and my expectations wwe not deceived.
4
EFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 251
6th. At the end of the year I examined the smail
matrasses, and the oils corresponding to them. The
results exhibited by the former were as follow :
No. 1. was limpid, and showed neither residuum
nor colour. A drop of water occupied the bottom. I
mixed with it ten grains of copal, after having exposed
the matrass to a temperature of from 122*^ to l^é'' of
Fahrenheit. The copal disappeared in a few moments :
forty grains introduced at intervals, in doses of ten
grains, disappeared in like manner. The varnish thence
resulting had a beautiful consistence, and showed, by
its nebulous tint, that the point of saturation had been
observed. IMotion alone, without the aid of heat,
was sufficient to complete the solution in a qviarter of
an hour. Here then, by adding more copal to the
first ten grains, I had fifty grains of that ir.atter held
in perfect solution in an ounce of essence.
No. 2. was of a slight amber colour ; the copal had
disappeared, and there were separated from it tvv^o drops
of acid, which, by reacting on the principles of the
oil, might serve to explain the origin of the tint as-
sumed by the essence. This specimen had also become
charged with forty grains of 'pulverized . copal, intro-
duced at four different times.
No. 3. exhibited a tint somevvhat more apparent
than the preceding. Two drops of acid water had
separated from it; but the liquid was nevertheless
transparent. It had become charged with - the same
quantity of copal as the preceding.
No. 4. had still more of an ambery colour than
InI^os. 2. and .'>.. Jt contLiined also acid v.ater. The
252 TREATISE ON VARNISHES.
same quantities of copal 'w-cre attended with the s^iiie
success as in the former cases.
No. 5. v;as nebulous ; which I ascribed to som^
motion accidentally given to the matrass : the water
was then confounded ^vith the oil. It had the same
tint as the preceding, and presented the same extent
of solution as the former specimens.
No. 6. had a reddish colour, and I extracted from
it some drops of very acid water. ït appeared to be
the least proper for making varnish, as it had beei
capable of admitting only thirty-five grains of new
copal, instead of forty.
All these -specimens of varnish l^ad the required con-
sistence. They were exceedingly oily ; extended them-
selves freely Vv'hen applied under the influence of the
sun ; and, in summer, required only two days to fornj
on ivor^' or on wood a solid and brilliant glazing.
It may be seen^ in this account of my researches,
that these oils, which were incapable of becoming
charged with copal during the first trial, experienced
in the conrse of time a particular modification, but
necessary to establish a kind cf analogy which ought
to exist between the principles of the two substances in
contact. Was the escient cause of this modification
the contact of the essence with a certain quantity of
copal ? Ir may* be reeollectetl that each of the small
matrîisses, subjected to experiment, contained ten grains
©f pulverized copal. This question, therefore, may
be answered by an examination of the oils contained
in the corresponding flasks.
7th. At this period 1 had received my instrunientjx
EFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 25S
and balances, the correctness of which enabled me to
ascertain the smallest differences. The specific gravity
of the oil in each of the six numbered vessels was ex-
amined by a flask capable of containing an ounce of
distilled v/ater, Fahrenheit's thermometer being at 59*^.
The follov/ing table exhibits the results, in the order
of their numbers :
Table ca/iii':ii2}ig the speci/ic grav'tty of the
rmmbered oils.
Specitic gravity com-
Reh'.livedecrensein
Order of the
pared with that of au
the ab.solute weight
numbers.
ounce of distilled w a-
of the ounce of di-
ter.
stilled water.
Gros, Grains.
Grains.
No. 1. , 7 . 60
12
No. 2. .
7 . 37
t35
[No. .'3. .
7 . 5S
14
No. 4. .
G . 70.'-
'JO, 1
No. o. .
7 . .57
15
In establishing the scale of these numbers, accord-
ing to their greater lightness, I sh^ll place them in this
manner: No. 4, 2, 5, 3, 1. No. G. was not compre-
hended in this examination, because, being only the
residuum of the distillation, it was loo thick and too
highly coloured to enter iiUo the composition of varnisji.
8th. When the specific gravity of these oils vas
known, it remained to ascertain, v/hether the solution
of the copal in the t:i,seiice, contained in each of the
small matrasses, w hich was very much exten4ed, ought
to be ascribed to a modification effected in the essence
itself bs (he contact of the copal, which had incor-
porated with il only fiowlyj and whether this copal.
t254f TREATISE ON VARNISHES.
Ts-hen once united to the essence, would not communi-
cate to the latter the property of seizing upon new por-
tions of the resin. It was necessary, therefore, to apply
to an ounce of oil taken from each of the numbered
specimens, the same quantity of pulverized copal, that
is to say, fifty grains, using only ten grains at a time,
as before. The following were the results :
The essence No. 1. could dissolve only forty-eight
grains of copal, and the solution was turbid. No sedi-
ment was produced by two hours rest ; and the addi-
tion of -J ounce of tlie same essence formed a varnish
of a good consistence, and very clear. Some clouds
only were observed at the bottom of the vessel.
No. 2. was treated in the same manner for the solu-
tion of the first forty grains of copal ; but the last
quantity introduced remained untouched. The var-
nish, which floated over this sediment, was turbid ;
and half an ounce of essence was required to make a
varnish of it similar to the preceding.
No. 3. was like No. 1. ; but, after tv;elve hours re-
pose, there was separated from it a small portion, which
might be estimated at tvvo grains : the addition of a
quarter of an ounce of the same essence, however,
made it disappear.
No. 4. refused to unite with copal : the whole mat-
ter was precipitated, a few grains excepted. The oil
had experienced no change in its colour or consistence.
The copal formed a mass in it.
No. 5. gave, with fifty grains of copal, the same re-
sult almost as No. 2. ; but no precipitate was formed
at t-lie time. The state of the soludon, however, an-
EFFECTS C¥ LIGHT ON ESSENCE OF TURPENTINE. 25.5
nounced that it would soon appear. It was less volu-
ininous than in No. 2. ; and only three-eighths of an
ounce of new essence was necessary to make it dis-
appear.
If the specific gravity observed in the numbered oils
be compared with their difterent degrees of power over
the copal, we shall find that this power acts in the in-
verse ratio of their tenuity and liglitness. The more
distant, then, that essence is from the state of ethereous
oil, the more energy it exerts on copal. This simple
theory -is sufficiently proved, first by the inactivity of
the essence of the shops, which I tried before I subjected
it to distillation (l) ; and then by that of the oil num-
bered 4., which we have examined (8),
9th. To these examples might be added others taken
from different experiir.ents, the details of which are
suppressed, to avoid extendiiig this chapter to too great
a kngth. The following result, however, deserves to
be knov/n : an oil which had no action on ccpal two
months after rectification, took up forty grains per
ounce eleven months after ; and fifty-two grains at the
end of eighteen months. The varnish was not more
coloured than alcoholic varnish prepared v/ith the great-
est care*.
Was this owing to the effects of the light? or was it
owing only to time, which, without any intermediate
* The specific gravity of this oil, examined by the test contain-
ing an ounce of distilled water, the thermometer being at 5'2'\
was :
At the first period 6 gros (54 grains.
At the second - - 7 gi'o^ GS grains.
At the third - - - 1 ounce 7 ^vains.
2,70 TREATISE OK VARKiSHÊ^.
substance, disposes the parts of the oil to assume pe-
culiar 'chamcters, which add to their specific gravity,
aiid which render them more proper to become charged
V\ith that resin ?
This is a question of so much importance that it de-
serves to be carefully examined*. But, before I enter
on this subject, I shall present the reader with a few "
considjerations on the mutability observed in the proper-
ties of essence of turpentine.
10th. What takes place in a varnish in which a se-
diment of copal is formed may be considered as a new
fact, the real cause of which can at present be only
conjectured. Whatever care may be taken to favour
the solution of the part precipitated, either by the addi-
tion of an oil, or by the use of caloric and motion, it
remains entire, or the part made to enter into solution
is so small as scarcely to be worth notice.
The same phenomenon is exhibited by varnishes
wliich are only turbid. It would appear that copal
contains two substances, the principles of which, dif-
ferently modified, are however susceptible of an inti-
mate combinadon, as seen in some bodies distinguish-
ed by the name of resinous gio/is or gummy resins. A
* Some particular facts had familiai-ized me iti so:ne measure
witli the idea that the light had had some influence on the present
results. It was therefore necessary to ascertain it in a direct man-
ner. I con.-equently made researches on the subject, and I gave a
detailed account of the results in a memoir inserted in die Journal
de Physique for March J/QS. These results confirm that light
alone was the cause of the phrenomenon, and it is greater and
speedier when the ox}gen gas of the atmosphere has free access
to it.
EFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 257
liquor, then, the pnnciples of the composition of which
have a more striking analogy to one of the two compo-
nent parts than to the other, will be able to separate
them. By this separation the insoluble part would be-
come only more refractory to the action of the vehicle,
and the quantity of it would even be increased, because
it would be deprived of its means of union. Several
substances exhibit these phssnomena when brought into
chemical contact.
Notwithstanding the instances which might be ad-
duced to jusdfy this opinion, or to give it every character
of probability, it is here offered merely as a conjecture.
It may not, however, be improper to call the reader's
attention to what takes place in a mixture of copal or
, of amber with alcohol, and with ethereous essence of
turpentine. These liquors seize on a slight portion of
■ these two kinds of resin ; but their energy is confined
in such a manner, that if the vehicle of the first infu-
sions be decanted, and its place supplied by a new
quantity of liquor, the latter will exercise a still weaker
action than the former, and so on in succession ; be-
cause the part of these resins which is soluble by this
kind of process has been extracted, or because what
remains is so envefoped by the insoluble part that it is
secure from eveiy attack.
This may have some relation in theory with our sedi-
ments of copal, the sokirion of which cannot be com-
pleted till the vehicle in contact has undergone, in it§
principles, new modifications, which develop in it new
I affinities with the resinous substance. It is thus that
we may judge of it from -what has been observed in
^58 TREATISE OÎ-; VARNISHES.
sections 5, 6, and 8. The same chemical effect may
take place also when colourless essence, but of a
density which may be compared to that indicated in
section 9, is employed.
1 1th. Anotlier phsenomenon, which deserves no less
'to be examined, is the ambery colour which the var-
nish assumes when made with essence easily decom-
posed, and which readily yields water. The varnish
speedily assumes colour, if by means of a few shakes
the small drops of water adhering to the dome are pre-
cipitated to the bottom of the matrass. This water,
which is acid, reacts on the oily principle^ and alters it.
Every essence of turpentine does not equally pro-
duce tliis effect ; which seems to depend on its nature,
and the strength of the acid it contains. Of seven
matrasses containing this oil, of different degrees of
density, and exposed on sand at a temperature of 200
degrees, there was only one which could serve to sup-
port the present observation. The experiments men-
tioned in the 6th section prove the truth of it. Whea
similar oils are used, it will be proper to substitute a
balneum marias for a sand bath, if a colourless varnish^
be required.
12th. The facts observed in mixtures of essence with
a small quantity of copal (5) render it ne<:essary tQ
offer some observations on that subject. What, then,
is the cause of this solution, which I have seen carried
further on a small quantity of copal (0), with oils pre-
served in small matrasses, than with the same oils with*
out mixture (S) ? The former were able to dissolve
fifty grains of copal per ounce ^ wIhIc Uàc hitter re»
1
EFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 25^
quired the addition of a new quantity of essence to take
up from forty-eight to fifty grains. It will be recollect-
ed also, that this addition of essence was made in the
relative and inverse ratio of the density of the oil,
which served as a basis to the experiment (8).
Two causes may concur to produce the effects ob-
served in the matrasses charged with ten grains of
copal. The first arises from the density of the essence.
This density, acquired by the solution of a portion of
the copal, extends to the oily body its quality of re-
fracting the sun's rays. It disposes it to collect a greater
quantity, to yield to their influence, and to acquire
from them modifications capable of developing a cer-
tain analogy between the principles of its composition
and those which constitute copal.
The second cause may arise from the precipitation
of their acid, which has followed the solution of tlie
first grains of copal. This separation of a part of the
water contained in the essence itself does not take
place in specimens of the same oil without mixture. It
appears that the essence in the . matrasses has under-
gone a kind of analysis. By this subtraction of a por-
tion of the aqueous principle, essential or foreign to
the composition of the oil, but so contrary to its resi<-
nous combinations, the essence must have assumed a
more oily consistence, and have formed a whole of a
greater density. This agrees very well with the anterior
observations, which indicate (9) thaï the density of
the essence, carried to a certain determinate point, be-
eomgs a character essential to the solution of copal.
V,. These two conjectures seemed likely to open anew
s 2 '
260 TREATISE ON VAR^TISHES.-
field for experiments, and the results of them might
become as- iiiterestir.''^ to philosophy as the first object
of this chapter appealed to be to that part of the arts
to which it relates. The matrasses and bottles which
contained the proof oils were closely shut with cork
stoppers. The varnish, which had dried around the
■«toppers of the matrasses, so as to form a kind of mas-
tic, left no doubt in regard to their perfect obturation.
To explain the iiKrease observed in the density of the
oil, k was impossible to suppose a loss occasioned by
the evaporation of the most ethereous part of the es-
sence, since there was no apparent decrease in its vo-
lume, the level of which had been marked by small
bands of paper pasted on the outside. The same cause
which opposed the volatilization of the oil appeared
to me still sufficient to present an obstacle to the intro-
duction of the oxygen gas of the atmosphere, which is
considered as the cause of the inspissation of oils. In
this phîenomenon, therefore, I could observe only an
effect of light.
But in what manner did it act ? Was it by combining
with the oil the pure air contained in the empty part of
the vessels? or was it by combining itself with the oil,
in a manner never before observed or suspected ?
Light, such as it appears to our senses, possesses,
no doubt, in consequence of its great velocity, the
same properties as caloric (fire), which has not yet been
found to possess gravity ; but, in combining with the
matter, would it not add to the gravity of the latter ?
It was necessary to make new experiments on this sub-
ject. I did so ; and though the results of them were |
S
ETFECTS QF LIGHT ON EaSENCE OF TURPENTINE. 261
foreign to tlie arts, they are so connected with the
theory of the object which I undertook, that I do not
l3iink them susceptible of separation*.
1 3th. The experiments which I projecte-d, with .a i-iew
to fix my opinioaiin regard to results so singular., seemed
likely to give m^ information at the same time respecting
the cause of the ditference observed in the density of
the products of the first distillation of the essence, and
which may be seen in the table (7). This table gives
to No. 1, which contains the tirst product of the di-
stillation, and which consequently ought to exhibit the
lightest essence, a specific gravity greater than is found
in the other numberst. This observation rendered it
necessary for me to be more circumrpect in the manner
of extracting the products of the disdllation which I
intended to m^ike. Besides, I considered it as a point
of importance to ascertain the specific gravity of the
products twenty-four hours after the operation.
I th<erefore distilled forty ounces of common essence
of turpentine, the product of which I divided into eight
equal parts ; the first six, of four ounces, and the last
two, of six ounces each. I took care to regulate the heat
in such a manner as not to render it necessary to remove
* See the Juurnal dc Phvsiqiie for ]Mar-ch 1^98 ; where the sub-
ject is treated in new points oi view, and in a more extensive
/nanner,
f It is ])ossible thnt this .difference might depend merely on the
fceat employed for the distillation : but I enter tdincd an idea that it
fnight more particulai ly arise from my occasionally removing tlie
■> 4ome of ii'drnt clay, which I took from the retort when the vapours
appeared to be too violent. _^
S 5
262
TREATISE ON VARNISHES.
the dome, the use of which accelerates the escape of
the vapours.
These ethereous products were afterwards exposed
to the influence of the solar light, their specific gravity-
being first ascertained by a test bottle capable of con-
taining an ounce of distilled water, the thermometer
being at 55 degrees of Fahrenheit. The details are ex-
hibited in the follo\^ino- table :
o
Table of the specific gravity of the products tiveniy-
four hours after distillation.
Order
of the
Particular characters of the
j Their specitic gf avity
as rom.parcdwitli that
of distilled water.
numbers.
products.
No.
. . 1
Colourless, but nebulous
in consequence of a little
water interposed between
gi-os. grains.
tlie parts of thu oil .
6 . . ÔO{r
3
Colourless, I'glitj ai^d
very limpid ....
6 . . 66
3
The same . . • .
6 . . 66
4
The same . .
6 . . 6'ô,V
5
The same i . , .
6 . . 66^
6
The same
6 . .67
7
The same ....
Nebulous, w'tli a stick-
ing odour of bitumen not
four.d in tlie preceding, &:
of an ambciy colour. This
6 . . 67 full
;
product was accompanied
8
w'xxh. 6 cU'ops of acid water.
6 . . (5-\V
wh ich had coloured the part
of the oil in contact.
The residuum of the di-
stillation was thick, and
weighed about 3 ounces.
N. B. The common oil
of tlie shops had a greenish
tint before distillation, its
speciiic gravity was . .
6 . . CS
1
None of liiese oils at-
1
tacked cop..' I.
ETFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 263
14th. April 1st 1787, three days after this examina-
tion, I closed exactly with pieces of fine cork the bottles
which contained the different portions of oil, numbered
in the order in which they had appeared in the course of
the distillation. I exposed them in the seat of a win-
dow which for six months of the year received the
solar rays three or four hours daily, and during the same
time a strong^ reflected light. The oil in these bottles
was exposed, therefore, to the influence of the direct
and reflected solar rays ; but it received them only
through a window, which preserved it from all external
accident.
The paper inscribed with the number of each flask
was pasted to it in such a manner that its upper edge
corresponded exactly with the level of the essence con-
tained in the vessel, and only one-sixth part of each of
these vessels was empty.
15th. On the 30th of March 1788, after a year's
exposure, I again examined on the spot these separate
portions of essence, and put them into a balance, that
I might compare their present specific gravity with that
Vhich they had indicated the preceding year.
Nos. 1, 2, 5, 6, and 7 had experienced no decrease
jn their volume ; because they had been completely
closed. No. 3 had decreased half a line in a surface
c^n inch in diameter ; and No. 4 three quarters of a
line.
The vessels marked ÎSÎos. 1 and 2 were lined above
the level of the essence, v/ith a beautiful vegetation of
crystals nearly an inch in length, which crossed each
flftlier ip every direcdon. They adhered to the an-
s4
264 TREx\TISE ON VARNISHES.
terior part of the neck of the flask, opposite to that
which received the direct solar rays. I thought there
was reason to conclude that these crystallizations might
have been formed under the protection afforded to
them by a plain square of paper, which preserved the
em.pty part of the flasks from the direct action of the
light and of caloric.
No. 8, which was in part sheltered by the angle
formed by the frame of the window, exhibited also very
beautiful crystals, which adhered only to that part of
the glass the least exposed to the direct rays. This se-
cond observation gave weight to my first conjecture.
The flasks having been inverted and kept in that
position for some hours. Nos. â, 4, and 8 sufi'ered a
little oil to ooze from them, in consequence of their
being badly stopped.
The stoppers were tinged internally of a pale-yellow
colour, as they would have been by weak nitric acid.
Their texture, however, vv^as very little altered. This
colour, which arose from the impression of an acid
vapour, was observed only in the part which had been
in contact with that vapour, and did not extend to the
interior part of the cork.
The therm.ometer was exactly at the same point at
which it had been the- preceding year, that is to say, at
544- degrees j but the consistence of the oil was no
longer the same. The two last numbers exhibited even
a slight shade of colour, which they did not possess
before the distillation. I shall here present a table of
the differences observed in the specific gravity of these
afferent portions of the same oil, after the interval of
EFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 265
a year, in order that they may be more easily com-
pared ; and I shall add a column pointing out the addi-
tional weight which each measured ounce of oil ac-
quired by the effect of the solar light. The test bottle
was always the same ; that is to say. it contained the vo-
lume of an ounce of distilled water at the temperature
already mentioned.
A comparative tahle of specific graviti/.
'order of
Speci
fie gra- Specific gr.;-
Inc.easc ot'
'the mat- Characters of the oils.
vity
observ-jvity
observ-
specific gra-
ters.
ed in
1787. led ir
1788,
vity.
No. 1
Limpid and co-
gros
grains.
gros.
grains
lourless oil .
6
66±
7
37i
43i
2
The same . ,
6
66"
7
39i
454-
3
ISIore fluid than
the preceding, &
colourless . . .
6
66
7
33
39
4
Very fluid and
colourless . . .
6
66\
7
24^
30
5
Oily, limpid, &
colourless . . .
6
66A
7
38|
43i
6
Exceedingly oily,
limpid and colour-
less ....
6
67
7
50-];
55i
7
Exceedingly
oily ana limpid,
colour somewhat
ambery . .
6
67
7
4/^
52^
8 Oily and limpid.
but aziibery . ,
6
- 1
7
38
4U
N. B. All these oils applied
to copal in
relatif
-e propor-
tions, according to their density
, effected
a sohit
ion of it.
and formed beautiful varnish, except Nos. 3 and 4
in which
the copal was precipitated.
It may readily be perceived, that the addition to the
specific gravity is here in the direct ratio of that of the
density acquired during the exposure of the oil to the
266 TREATISE ON VARNISHES.
solar light.. Nos. 6 and 7 serve to confirm the follow-
ing physical truth ; namely, that among homogeneous
liquors, and oils in particular, of a different specific
gra.vity, those which are densest possess also the great-
est refractive power ; and, consequently, are the most
Gapa.ble of accumulating the luminous rays.
This principle being laid dov/n, if a greater accumu-
lation of light be admitted in the latter, there is reason
to believe that the result ought to be a new combina-
tion ; and it is in this combination that we ought to
look for the cause of the increase observed in the spe-
cific "Tavitv, and in the densitv of our oils.
No. 8 would have exhibited the same phenomena as
Nos. 6 and 7, had it not experienced from the stopper
the same inconvenience as Nos. 3 and 4, which showed
a sensible diminution of their volume. I have already
said ( 1 4), that by inverting the- bottle it lost its oil,
through a fault in the cork. This observation, for
which I was indebted to chance, led me to the disco-
very of a phasnomenon too striking to escape the at-
tention of those who cast their eye over the compara-
tive table of the specific gravities : it is seen that the
increase of it took place also in the direct ratio of their
less evaporation. No. 3, v/hich had lost only half a
line of its volume, showed also, in the increase of its
density by the influence of the light, nine grains more
than No. 4, which exhibited a diminution in its volume
of tlirec'-fourths of a Hne'\ The numbers which g^ve
* The paper ir-dox of tlie bottle No, 8 %vonlcl, no dniiht:_, have
shown a sensible dimin-dtion. Butpreaufnuig on too liglit grounds,
piiliaps, that tills poriiou of essence çovdd not be eraplo-yed lor
EFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 2G7
access to the external air are exactly those which
iliowed the least specific gravity.
]6th. It is impossible to admit as the cause of this
increase the evaporation of the most ethereous and most
volatile parts of the oil. There was no sensible de-
crease in the vessels 1, 2, 5, 6, and 7j and these nmn-
bers showed the greatest increase in the density of the
oil which thev contained. A simple comparison of facts
will be sufficient to show the falsity of this supposition.
If we admit, according to the result, an addition to the
real specific gra\ity of No. 7, which contained six
ounces of essence, we shall find 325 grains added to
the specific gravity of the preceding year. These 325
grains make. IS deniers and S grains, the deduction of
which from the whole mass of essence would have
made a deficit in its first volume of three lines, as I as-
certained by experiment.
This increase, then, can be explained only by an
addition produced under the influence of the light j but
whether this fluid, notwithstanding its extreme rarity
and great velocity, undergoes any particular modifica-
tions, or causes the oily bodies exposed to its direct in-
fluence to undergo them, is what I will not pretend to
determine. These experiments have discovered to me
one fact, which I believe to be new. The influence
of light is observed here in a very sensible manner ; but
what is the nature of this influence ? Does it enable
Ae oxygen gas contained in the atmospheric air to
overcome the obstacle opposed to it by the best cork.
varnish^ on ?.ccQ\\xit of its colour, I took out two ounces of it fur
-another purpose. The index then was of no use.
268 TRP.ATISE. ON VAÎlîrîSHES.
Stoppers, in order tiiat it may combine with the oil ? or
does it materially coiLcar itself to produce this phazno-
Kienon? These questions desen^e further research.
In regard to the supposed combination of the oxygen
gas extracted from the atmosplieric air, it wiil P'-jear
in this case contrary to the evidence oi the results.
Nop. 3, 4, and 8, which really lost part of their sub-
stance, in consequence of their being incompi' • 'y
chut, and which for the. r:nme reason aflbrded accc .; to
the external air, ou^'iit to have presented icSuUs r.^ree-
able to this supposed combination. We however know
them to be contrary ; since the essence they contain is
specifically lighter than that of the other numbers.
This observation will hold good also in regard to No. 8,
xvhich containing an oil more réfringent than Nos. ] ,
2, and 5, ought on that account to acquire a greater
density than Nos. 3 imd 4, which were iindçr the
same circumstancej.
I am inclined to believe that the results observed in
Nos. 3, 4, and 8, are not to be ascribed so much to the
introduction of the external air as to the dil^cidty ex-
J>erienced by the light, in commencing and bringing to
perfectign its particular mode of combination in the
oily vapour which occupied the empty part of the ves-
sels,— a vaporous combination which the elevated tem*-
perature of the solar rays, or that of the atmosphere,
expelled before their union with the mass of the oil.
I, however, ofier this idea as mere conjecture : to
ascertain the truth of it would require a great many
comparative experiments, made with vessels, some
full_, and others half fail j but all hermetically sealed.
EFFECTS OF IJGHT ON ESSENCJZ OF TURPENTINE. 2G3'
To determine the effects of the oxvgen gus or es-
sence of turpentine, I arranged, in the month of August
] 787, an apparatus, the results of which I shall exa-
mine at the end of a year. î can, however, assert that
I have had sufficient time to observe phgenomena which
justify the opinion I have advanced in regard to the
combination of light with the vapour, and in the
vapour of the essence *. Nothing now remains but
to deduce the consequences which arise from this series
of researches.
.General consequences and conclusion.
17th. The object of these researches, as already
seen, was to verify a fact, known no doubt to some
chemists, but which artists cont'^st, — namely, the solu-
bility of copal in an oil lighter and less coloured than
fat oils, — in a word, in essence of turpentine.
The result of the experiments here detailed shows
that this essence is the fittest liquor for maldng copal
varnish ; that an elevated teni^perature is not required
to favour the process, since it is below that of boiling
water. INIere stirring is even sufficient in summer. If
the simplicity of this method be compared with that
employed in the operation of uniting copal with fat
oils, which cannot unite with it but when it is in a
5tate of liquefaction, by the effeci: of a very high tem-
perature, much superior to that of boiling water, it
* The experiments detailed in the memoir already mentioned
[Journal de Physique, Mars l^QS) leave no doubt in regard to the
combination effected in the vapour itself, vben the vessel is ex-
posed to the direct influence of the sup. '
270 TREATISE ON VAP.NL^HE::,
will be allowed that the liquor which c-an dispense vith
this forced liquefaction, which is even satisfied with a
temperature of from 88 to ]00 degrees, aided by
simple mechanical motion to effect that union, is the
best of all for the intended purpose.
But these experiments show also in their results,
that essence of turpentine does riot always exhibit the
qualities requisite for effecting this union. We have
seen (9 and IJ) that ethereous oil had absolutely no
action on copal ; that its dissolving property was mani-
fested in the ratio of its density (5, 6, and 8); that
this density is altof^cther independent of the rectification
of the oil by a second distillation, which in general
gives only a light^ ethereous oil, if the operation is
managed with care ; or an oil, the specific gravit)'' of
which does not exactly follow the order of the division
of the product (4 and 7); that the light alone, bv the
effect of a particular combination, the mode of which
can only be presumed, becomes the principle of this
density, so essential to the solution of the copal (7, 8,
IS, 14, 1,5 and IG), that this essence of turpentine,
which at the moment of its rectification has exercised
no power over the copal, may by the mere effect of
the influence of the light dissolve, after a certain time,
the pulverized copal which has been precipitated from
it untouched j that the copal even increases its energy,
ance the essence can dissolve a larger quantity of it than
when it is exposed alone, and v.'ithout any mixture of
copal, to the same infitjence of the ligiit (5, 6 and 8).
These results prove also, that the more the essence
of turpentine is disposed to be deccmpcscd, and to fur-
EFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 271
nish acid water, in the course of the distillation, or
during the time of the process for making the varnivsh,
the less proper it is for the solution of copal ; becausa
this free acid does not fail to react on the oil, and to
communicate to the whole mass a tint, which it ought
not to possess (1 1) ; in a word, that this oil is suscep-
■ tible of giving a concrete volatile acid salt, contained
'in certain balsamic substances (1, 2, and 1.3). The
.' existence of that salt, which places turpentine among
the balsams, according to the new defniition of Four-
croy, was at this time unknown.
Some authors assert that they have been able to dis-
'. solve copal in essence of turpentine : this chemical pro-
, perty of essence, however, was considered as very pro-
l;)lematical. The remembrance of it even seemed to
be preserved only in consequence of the merit of the
authors who admitted the possibility of it. Two per-
sons of great celebrity have entertained opposite opi-
nions on this subject. Lehmann, whose name is well
known in chemistry, asserts that, copal is soluble iu
essence*. Wadn, an ingenious artist, refutes this
* *■' Copal^ with oil of turpentine, gives a vaniish whidi in »
great measure is similar to amber vaniisiî. The first doses are ms^
part of copal and four parts of the oil of turpentine> which is then
added in greater quantity, without detenninJng the weight, ia
' wder to dilute the varnish and render it fluid." See'Rechercht'S
Historiques et Chimiques du Copal, Mem. de. V Academic de Berlin^
tome it. See also L'Art défaire l'es Vernis, l5'c. par JFaiin, edit.
de 1772, p. 162.
This is the first author who menlions the solution of ccprJ ia
essence of turpentine. As Watln did not succeed, he expresses
doubts which, though not accompanied witiî any explaioation, suf-
272 Treatise on varnighEo.
opinion, and maintains that it is not soluble * : both,
however, are in the right, since this solution depends
on a degree of density which the essence sometimes
exhibits, and which it may have accidentally exhibited
to Lehmann.
18th. The solubility of copal in oil of turpentine
being once established, nothing remained but to make
use of the observations scattered throughout this essay,
in order to discover the speediest, and at the same time
the most proper, method for making varnish with
essence.
There was reason to think, that by dividing the
products of one distillation of this essence into seven
or eight parts, it might be possible to discover in these
divided parts those which would exhibit the qualities
requisite for completing the solution; but it was ob-
ficiently show that he had strong reasons for not considering tlie
results announced as bearing tlie stamp of rigorous exactness. See
his Reflections, p. 10(3,
The author of Traité sur la CofiJpositïon des Vernis en général,
edit, de Paris 1780, mentions also, on the authority of mere tra-
dition, the solubility of copal in essence^ but he says nothing of
tlie state of the oil. See page 4 ct seq.
* " It appears proved in practice, I mean the practice of sucl>
persons as myself, that neither alcohol (spirit of wine) nor es-
sence can dissolve copal nor amber." See Art défaire les Ferfiis,
i^c. edit, de 1/72, p. 111. The last edition of 1782, which I
have just received, couiirms the same opinion in tlie article of Re-
flections, p. 279. " Copal dissolves neither in spirit of wiiie nor hi
any essence, whether in a mass or in powder, but it dissolves in,
fat oils." See the same it'ork, p. 37. " Copal will never dissolve
in essence of turpentine." Page 8, in the notes which allude lq
the fliults of the Parfait Fernisscur. ^
tFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 273
served that this process at length gave a contrary re-
sult (is) j since it often deprived the essence of the
shops of that property which it might liave acquired
from time, or from any other circumstances. This
distillation, however, is indispensably necessary^ when
colourless vaniish is required ; because the essence of
the shops is always more or less coloured. Besides,
this operation, which may be performed on a large
scale in manufactoiies, furnishes a very simple method
of obtaining the most ethereous essence, the use of
which I have recommended in the composition of var-
nish destined for valuable paintings *.
If the distillation of essence be undertaken with a
view of accomplishing both these objects at the same
time, it must be performed by means of a sand bath,
taking care to cover the retort with a dome of burnt
clay f. From a hundred ounces of this oil ninety are ex-
tracted ; the first forty of v/hjch, forming ethereous
oil of turpentine, must be reserved for the composition
of varnish destined for picturesp The last fifty ounces
of essence are applied to the composidon of copal var-
jnish. The residuum even is not lost; it serves for
grinding and mixing up oil colours. If too thick, it is
idiluted with new essence.
. From ten to twelve grains of pulverized copal are
mixed with an ounce of the essence destined for varnish,
^d the mixture is shaken, immersing the matrass in
^ bath of boiling water.^ If the copal readily dissolves
in the essence, new dose's are added; and this is con^
* See the Third Genus, No. XII. p. 133.
j- See the description of this process, 2d method, p. 70.
T
^74. TREATISE ON VARNISHES.
tinued till the essence refuses to take up any more. Ic
sometimes happens that this essence gives immediately
a very beautiful varnish and of a good consistence ; at
other times it refuses every kind of union. In the first
. case the varnish is filtered through cotton, after it has
been allowed to deposit the untouched portions of the
copal: in the second, that is to say, when the copal
resists the essence, the matrass is closed \^dth a cork
stopper, and exposed to the solar light until the essence
has acquired an oily consistence. It will assume this
state the more easily, the greater the quantity of copal
it holds in solution. The influence of the light gra-
dually manifests itself on the essence, and the preci-
pitated portion of the copal decreases, and at length dis-
' appears entirely. The consequence is, that the essence
' acquires from this matter, "which ' is mixed with it, a
new consistence and character, which dispose it to be-
come charged Avith a greater dose of the resin; and in
this manner to constitute a real varnish. This has been
observed in the sixth section.
Essence prepared in this manner ought to be pre-
ferred to the other vegetable oils, which ' approach
nearest to the same state of density or of specific gra-
vity. The varnishes, indeed, which result from the
union of it, with resins are less fat and of a more drying
quality than those made with oil of lavender, oil of I
' thyme, oil of rosemary, &c. employed directly or with
some intermediate substance. They are also exceed-
ingly durable when copal forms the basis of them;j
and they produce the most beautiful effect on metals
and polished wood. Copal varnish made with eM
EFFECTS OF LIGHT ON ESSENCE OF TURPENTINE. 275
sence has a slight amber colour, which disappears
after it has been applied. The oily character, which
contributes to its solidity, disposes it to become much
better charged than alcoholic varnishes with those
vegetable, resinous and metallic colouring parts with
v/hich the variety of colours that enrich transparent
enamels can^e imitated. It may be readily conceived,
that to preserve the transparency of varnish, and to
give it that lustre which completes the illusion, none
but colouring matters entirely soluble in essence must
be employed.
It was proper to detach from these particular obser-
vations, and even from this part of the work, every
thing relating to the use of colouring substances, and
the different purposes to which copal varnish made
with essence may be applied: a treatise therefore on
this subject will be found in the second part of the
work vv'hich follows.
T 2
i
\
PART THE SECOND.
ON THE
PREPARATION OF COLOURS,
AND THB
METHOt)S OF APPLYING THEM.
lîî THE
DIFFERENT KINDS OF PAINTING, &c.
TREATISE ON VARNISHES.
PART THE SECOND,
CHAPTER L
Tlisforical account of the mdiire of the colouring snhstafices
7/sed in pahituigy with a description of the processes em-
■ployecl to extract 'them, and of the methods of preparing
or modifying them,.
1. HE account given in the first part of this treatise, of
the substances which concur towards the composition
of varnish, must tend to regulate the appHcation of
them in a more certain manner. I'o this advantao-e
o
may be added that of rendering artists familiar with the
different processes which art employs to extract or to
modify productions which nature exhibits to us only
under fixed and determinate characters. Our know-
ledge of an art ought not to be confined to what re-
lates merely to. manipulations, which are more or less
varied by long practice : it ought to be extended also
to every object subservient to it.
The composition of the colouring substances, which
forms the subject of this second part, requires more ex-
tensive and more varied processes, the theory of v/hich
cannot be understood without some preliminary know-
ledge. In regard to these substances, we shall follow
the same course as that adopted in treating of the mat-
T 4
280 TREATISE ON VARNISHES.
ters employed in the composition of varnishes. It is,
therefore, of importance that our observ-ations on the
principles of colom*s, and the effects of their mixtures,,
should be preceded by an historical account of the sub-
stances charged with colouring parts, arfd by a view of
the means which art employs to transfer, under some
particular circumstances, the colouring principle of
one body into another ; or to communicate to it new
qualities, which render it capable of extending the won-
derful power of combinations. Nothing seems better
calculated to make the artist and the amateur sensible
that no 'art is independent, and that all lend to each
other reciprocal assistance, which concurs to\vard5 their
improvement, and often even to the celebrity of the
individuals who have sufficient strength of genius to
soar be}^ond' the usual beaten trask»
Bougival white.
Painters often employ white matters for grounds.
Ceruse is distinguished by great durability. It forms
an excellent priming, proper for receiving other co-
lours ; but there are a great many cases, particularly
in painting in distemper, which admit the .use of a
more common and less expensive white, such as that
of Bougival, Spanish white, white of Troye, &:c.
Bougival white takes its name from the place where
it is extracted, which is near P/Iarly, at the distance of
a few leagues from Paris. It is a sort of very fine marly
earth. Normandy, Auvergne, and many other di-
stricts, contain beds or strata of a white earthy matter,
commonly known under the name of tobacco-pipe clay,
5
BOUGIVAL AND CREMNITZ WHITES. 281
This earth, when very white, is much better for house
painting than any other white earth of a calcareous na-
ture, such as chalk. The celebrated Wedgewood,
who has established a very large manufactory of
earthen ware, which in elegance and beauty is equal
to the finest porcelain, was exceedingly nice in his
choice of this clay, some of which he obtained from
Normandy. If similar establishments require that purity
should be united to whiteness in the clay employed, the
same rigour is not necessary in painting. Body and
whiteness are the principal characters required. If
Bougival white is not a pure clay, it possesses that
whiteness which assigns it a conspicuous place in the
. order of colouring bodies.
It is sold in the shops under the form of oblong
cakes, into which it is cut, after the small stones and
sand mixed with it have been separated by washing.
Washed chalk is often substituted in its stead ; but
connoisseurs have no need of analysis to detect this
fraud. "Washed chalk gives less body to painting than
clay, and does not unite so well with oil when applied
to that kind of painting.
According to some experiments which I made with
Bougival white, sent to me from Marly, this marl con-
tains nearly a third of carbonate of lime (chalk). This
' mixture renders it inferior in oil painting to real Spa-
nish white, and to white of Moudon.
Cremnitz ivhite.
The composition of Cremnitz white, in regard to the
nature of its base, seems still to be very uncertain.
282 Treatise on varnishes.
Three sub^t-v^-^-^^s, which have nothing in common but
the name i; ihem, are sold under diis denomina-
tion. i>)rec!: -experiments, which I made on specimens
obtained from different colourmen, did not justify the
idea entertained by some celebrated painters, that this
white is merely an oxide of tin * (calx of tin). In seve-
*■ I shall embrace the opportunity afforded by the occurrence of
tlie term metallic oxide, to give a short view of the theory v/hich
establishes this expression in the room of the word calx, employed
formerly to denote certain metallic preparations.
According to the principles of the Stahlean chemistry, the name
of calx was given to every metallic substance which, in conse-
quence of being subjected to the action of fire, excl^anged its con-
sistence and metallic brilliancy for a new pulverulent form, co-
loured or not coloured, according to the nature of the substance,-
and according to the degree of heat experienced. The name calx
was given also to the same substances, when reduced to powder
by acids, or when precipitated from their solvent by another sub-
stance which seized on the solvent. It was in consequence of tliis
convention that the general denomination of calces was given to
litharge, minium, ceruse, white lead, calcined lead, calcined tin^
and all metallic substances precipitated from acids by the means of
alkalies, &c.
Direct experiments, conducted with great. sagacity by Lavoisier,
and repeated by a great number of chemists, have freed chemistry
from the shackles of the old school. Combustion, and the iaflam-
mation of substances which are susceptible of these two states,
have no longer been cpnsidered as the tertn of destruction : on tlie
contraiy,. in the hands of the chemist tiiey have produced all the
signs and real characters of new chemical combinations. The evi-
dence of these com-binations is so striking, that it will no longer
admit the vise of the old theoiy, nor allow us to confound meta-
morphoses, which metallic substances undergo by tlie action of heat
and t-he concurrence of oxygen, with that whicli cfdcareous earth
and stones*.of >tlic same kind experience from accumulated caloric
BOUGIVAL AND. CREMNITZ WHITES. 283,
ral specimens purchased in . diflerent shops, I found
oxide of bismuth (calx or magistery of bismuth) j and
(ardent heat) . It is well known tliat the latter substances are re-
duced to a real calx (lime) by the loss of a little water ; and of a
particular acid which was long distinguished by the name of fixed
air, because it gave them their state of consistence ; but which is
now called carbonic acid, since the decomposition of it has shown
that its base consists of carbon or charcoal.
Becker, and Stahl his disciple, as well as the old school, placed
metallic substances in ihe class of compounds. They considered
them as so many bases united to a particular subtile principle,
which produced metallic brill ianc)-^, and which they denoted by the
name of phlogiston. The action of fire was exercised only on this
principle, which it separated from its base, and the latter tlien
assumed tlie earthy and pulverulent form. This principle being
adniitted, every metallic calx was merely the result of the mediate
or immediate application of fire ; it was the metal destitute of
phlogiston, which communicated to it the brilliancy and consist-
ence it possessed before tlie operation.
This first hypothesis ought to have given birth to another, serv-
ing to expl iin how a substance, which lost one of its essential
principles by the action of caloric (fire), should nevertheless ac-
quire an addition of -\fth to its real weight.
But this is not the place tor enlarging on the subject in question,
I shall, tlierefore, content myself with obseiTing that this theoiy,
irreconcilable in regard to tlie most essential points, has given
place to a doctrine which, neglecting hypothesis, establishes its
foundation only on facts. It ac'mits that metals belong to tlie cla§s
of simple substances j that they are combustible j and that in every
case of their exposure to fire, instead of losing, they acquire a
new element;, Mdiich from simple converts tliem into compound
substances. This aaditlonal principle or element is the base of
pvu-e ail- or oxygen, and the union of oxygen with caloric (fire)
constimtes oxygen gas, which composes, at the least, tlie fourth
part of the atmospheric air.
HSif TREATISE ON VARNISHES,
in two particular cases oxide of lead (ceruse). It did
not appear that any of them contained oxide of tin.
Other experiments, undertaken with a view to ascertain the
composition of acids, have proved by their results that the same
oxygen, the union of which with caloric constitutes oxygen gas,
known formerly by the denomination of pure air (vital air), is also
the acidifying principle, and consequently the generator of acids.
On account of this property tlie new chemists agreed to give it the
name of oxygen, of which the word oxide is a derivative. Every
metallic substance, therefore, which when exposed to a high tem-
perature abandons its consistence, its tenacit)', and its brilliancy,
to assume tlie characters of a substance pulverulent by the addition
of oxygen, the base of vital air, which has served for the combus-
tion, ought to exchange its old name calx for that of oxide. Hence
the expression oxide of lead, oxide of tin, oxide of copper, iron,
bismuth, &:c. j because in this case these meLils are oxidated by
oxvgen, which exists in tliera in tlie pure state, and not in that
of gas.
The heat being increased, it at length favours the combination
of the oxygen contained in the air witli the metal, and reduces it
to a metallic oxide : but acids furnish, from tlieir own substance^
tlie oxygen necessary for oxidation J audit is tlie speedier as the
acid is more disposed towards the combination.
All these particular effects are connected with the general
theory of combustion, the principal result of which is the combi-
nation of oxygen, the base of pure air, with the combustible body.
From these observations the reader will be enabled to compre-
hend easily the tlieoiy of the reduction of metallic oxides. Thiy
reduction cannot take place but when a combustible body such as
charcoal is applied to them, under the influence of a very higb
temperatiue. The oxygen contained in the metallic substance,
which it converted into an oxide, joins the combustible body, by
the effect of elective ailînity, and forms with it carbonic acid
(fixed air), which escapes : the m.etal being then abandoned re-
appears witli its former properties.
CREMNITZ WHITE. 286
Two of these specimens seemed to be mixed -with a'
great deal of chalk. The Cremnitz white, ■)0ndi coî]-_
tained this mixture, was in cakes of about tv/o or thrc\^
inches square, and different in thickness ; but ic never
exceeded an inch.
Cremnitz white, made with bismuth oxidated by
means of nitrous acid, or in any other mamier, ought
to possess no advantage over that which has lead for
its basis. It is more liable to be altered by the impres-
sion of the light, and of the vapours which arise from
stagnant water, privies, &c.
Composition of a white colour, to ivldch I give the
name of Cremnitz white.
I found means to make a beautiful pearl white,
which I call Cremnitz white, with the oxide resulting
from the rapid solution of tin in nitric acid (pure aqua-
fortis), to which was added a fourth part of the subli-
mated oxide of zinc (flowers of zinc), and an eighth
of white clay, extracted from Briançon chalk washed
in distilled vinegar *. This mixture, when thoroughly
When the term metallic oxide, therefore, occurs in the chapter
on colouring substances, or elsewiiere^ it is always to be nnder-
ptood as substituted for the word calx, which has no relation with
fhe present theory of chemistry,
* To prepare Briançon white, select the whitest specimens, and
Tasp tliem with a piece of the skin of the sea-dog. Put the powder
into a jar, with a quart of good vinegar for every pound of the
powder : stir the mixture daily for two weeks, and decant the
.vinegar without agitating tlie deposit : then pour clean water over
the deposit, and, having stirred it, threw the whole upon a filter,
t>y which means the water of the first washing will be separated.
286 TREATISE ON VARNISHES.
washed, dried, and sifted through a silk sieve, gave a
very v/hite powder of a mean gravity; and so secure
from all changes effected by the impression of the light
'arid of vapours, that no composition of this kind can
be compared to it. It is certainly too expensive for
house painting ; but it may be useful for objects which
require other processes than those employed in com-
mon. It would, no doubt, be attended with great
advantage in painting pictures.
Were it necessai-y to substitute any other metallic
substance, lead ought to be preferred to bismuth. Lead
rapidly dissolved in nitrid acid (aquafortis) is preci-
pitated in a white oxide, which resists in a ' sufficient
degree the impression of the light, but less so than
tin. Those who wish to avoid the trouble of purify-
ing Briançon chalk may substitute in its stead very
pure Morat or Moudon white.
Spanish ivhite.
Spanish white is a pure clay, which may be washed
in vinegar to separate such calcareous parts as are mixed
with it. But this process ought to be employed only
Continue to pour more water over the sediment on the iilter, till
the water which passes is found to be insipid. Then spread out
the filter with the sediment on a hair sieve, sheltered from dust,
and dry it till it appears under the form of a white powder. ïlie
vinegar here separates from this argillaceous matter all the soluble
parts, which might alter its vmctuosity3 and particularly the ferru-
ginous particles which are often mixed with it.
The division of Briançon chalk may be eifected by pounding it
jjin water, which must be frequently decauted when it contains only
tlie fine parts.
SPANISH V/HITE. GYPSUM. 28t
'in particular cases, when it is necessary to have it ex-
ceedingly pure. Its afc;illaceous nature contributes to
the solidity of the ground, when it is employed in cil
painting or for varnish. It acquires body ; but in these
cases it must be used very dry, like all other earths.
^ When moist, their union with oil and varnish is imper-
fect: they granulate under the brush.
Rolls of washed chalk, which possess none of the
qualities required in Spanish white, are often sold in
the shops under the same denomination.
The diiference, however, between real Spanish white
and the chalk attempted to be sold in its stead, may
■ be easily ascertained. Nothing is necessary but to
pour upon the specimen a few drops of nitric acid
(aquafortis), or of strong vinegar. If the Spanish white
' be pure, there will be no effervescence ; if an effer-
' vescence takes place, it is owing to a mixture of chalk.
In this case, take some small fragments of the white
and immerse them in half à glass of vinegar : if they
disappear entirely with effervescence, the whole is cal-
careous ; if any part remains, it will be argillaceous.
The quantities of each of these earths may then be
' estimated merely by the eye.
' ' Gypsum.
Gypsum is a natural combination resulting fi'om the
iUnion of the sulphuric acid (oil of vitriol) and lime
(the base of calcareous earth). It is a sulphate of
lime. When subjected to calcination it is exceedingly
^seful in the arts. In this state it is employed in build-
28S TREATISE ON VARNISHES.
ing, and in decorations for apartments. It is used also
with constant success in agriculture.
Plaster when mixed with water, in order to be cast
in moulds, is subject to certain rules. To give it
proper consistence the water it has lost by calcination ^
is sufficient, If too large a r 'iintit)^ be addtd it weakens
its force, prevents it from .inquiring body, and renders
it wl;at is called drowned -olaster.
In preparing it to be r.nployed as a white colour in
house painting, it ouguc to be drowned with a great deal
of water. This sup.-iabundance of liquid keeps all its
parts separated, and favours the required division.
When divided in this manner it forms a very valuable
article for whitewashing apartments, and for painting
in distemper.
The last operation is very simple. When diluted
with a great deal of water, stir the mass with a broom,
and suffer the powder to be precipitated. Decant the
supernatant water as soon as it is clear; then wash the
matter a second time, and dry the sediment after the
ïquor has been poured off.
This white is exceedingly fine, and inore delicate
than that of chalk when the calcined gypsum is pure;
that is to say, without any mixture of clay.
Plasterers do not hesitate to substitute this whitening
in the room of ceruse, which is not superior in beauty,,
but which is more durable and dearer. When toqi
thick a coating is applied, it rises in scales j which is,
not the case when ceruse is employed.
MOUDON WHITE. WHITE LEAD. 289
White of Moudon or of Marat.
For some years past we have obtained from the
Pays-de-Vaud, in Switzerland, an argentine, silky white,
of an exceedingly fine grain, to which we give the
name of Moudon or Morat white ; because both these
towns are in the neighbourhood of the place where it
is extracted. It is a real Spanish white, a pure clay,
which is employed with success in our manufactories
of paper-hangings. Our druggists often sell it as an
absorbing earth, under the name of nitrous panacea,
and even under that of magnesia ; though it stands the
action of acids without giving the least signs of effer-
vescence; This earth would afford a great resource to
a manufactoiy of ceruse: when united to that oxide it
forms, in oil painting, pearl or dark grays, which are
durable and possess great lustre.
■White lead.
White oxide of lead by vinegar >
White lead is an oxide (calx) produced by the means
of vinegar.
The process employed for the preparation of it is
the same as that used in preparing oxide of lead, com-
monly known under the name of ceruse. Lead readily
suffers itself to be attacked. Common air exercises
an action on it, and covers it with a v/hitish dust, which
is nothing else than an imperfect oxide of lead. This
substance may be observed on large edifices covered
tidth lead j but the oxidation when left to nature is too
u
290 TREATISE ON VARNISHES.
slow to supply the wants of the arts; ancj for this
reason a more expeditious process is substituted in its
stead. It consists in exposing plates of lead to the
fumes of vinegar.
The jars are half filled with vinegar, and the plates
of lead, either rolled up or flat, are suspended over
the surface of the acid. The jars are then covered,
and being placed on a sand bath, a heat is maintained
Sufficient to cause the vinegar to throw up ftimes,
which circulate around the metallic plates. These va-
pours, being of an acid nature, exercise an action on the
lead, penetrate into it, and convert it into a white sub-
stance called white lead. These plates are removed
when it is observed, on breaking them, that the whole
lead is converted into oxide, and that no more traces
of the metal remain. When these plates are dried
they become very solid.
Various other processes are employed for the same
pui*pose, but they all conduct to similar results. Some
manufacturers place these jars in warm dung, and leave
them there twenty or thirty days without examining
the state of the lead. They then take them out, or
scrape them, to remove the oxidated part of the metal;
after which they expose the remaining part to new
fumes of vinegar, and continue this operation until
the whole of it is converted into oxide. This opera-
tion, however, is applied in a more particular manner
to the fabrication of ceruse ; for when it is necessary
to prepare that white lead sold in cakes, and not in the :
form of conical pieces, the plates are exposed to the j
fumes of vinegar till they are entirely oxidated. '
I
WHITE LEAD. 291
Other manufacturers dispose their vessels in such a
manner as to favour a distillation. They cover their
jars with capitals, in the form of an alembic, and apply
a sufficient heat to distil the vinegar. The distilled
vinegar is then kept in reserve for the preparation of
acetite of lead (sal saturni). In this process the vinegar
acts with more energy, and the lead is completely oxi-
dated and in much less time.
When the vinegar distilled in this operation is em-
ployed for the purification of acetite of lead (salt of
lead or sal saturni), the same quantity of common
vinegar is put into the jars, to supply the place of that
which passes over in distillation. But if the distilled
vinegar is not destined for any other purpose, it is put
again into the jars as soon as a certain quantity of it
is found in the receivers.
White oxide of lead, vvhen purchased in cakes and
not in the form of powder, is free from any alteration;
but it is not uncommon to find in the int-erior part of
these cakes small plates of lead in the metallic state.
Painters, who do not grind their own colours, are
often discouraged by the gray tint which white lead as-
;l sûmes under the muller. This effect, v/hich is merely
accidental, lessens their confidence in it, and renders
them uncertain in the choice of their white. If the
vfhite oxide of lead still contains particles of lead not
oxidated, this metallic part becomes divided by the
iftotion of the muller, and renders the colour grav.
Artists, therefore, ought first to ascertain whether the
■*hite lead is pure, and to select those cakes which are
thinnest. Besides, the porphyiy and the muller ought
u 2
2^2* TREATISE ON VARNISHES.
to be perfectly clean ; because this oxide, which offëlî
contains a little acid moisture, is more disposed than
afiy other matter to attract parts resulting from prece-
ding operations of grinding. To obtain it of a fine
quality, it ought to be ground several times. It is often
preserved under water in earthen-ware or glass vessels ;
but, for the m.ost part, it is kept in the form of small
pieces of a conical shape.
If form be considered as a matter of indifference, the
white, newly ground, is spread out on strong paper,,
in a thin stratum : when dry it is removed in scales,
a!id preserved in that state in vessels well closed, to
defend it from the contact of every kind of vapour.
This oxide is lead penetrated by oxygen, which
abounds in the acid of vinegar ; but it does not contain
enough of developed acid to be considered as a salt.
It is reserved, in general, for delicate painting. This
' substance, which I shall call white oxide of lead, stands
better than that obtained by the following preparation.
Ceruse. Oxide of had hy vinegar.-
When a manufactory is established for the prepara-
tion of ceruse, less precaution is employed in the ex-
prosure of the plates of lead than in the preparation of
white lead in cakes. The plates are also thicker ; be-
cause the oxide is scraped oft as it is formed. When
a certain quantity of it has been collected, it is laid on
a flat stone placed in a horizontal direction, and is
ground by means of a muller fixed in a vertical posi-
tion, which is made to turn round. The oxide is mixed
with a little tobacco-pipe clay, or with Spanish white j
■CERUSE. ^ 293
•and when the mixture is well kneaded under the muller,
the whole paste is divided into small conical cake's,
•which are dried in a stove, or in the open air, accord-
ing to the season or the situation of the manufactory.
Each cake is WTapped up in paper, and tied with a
piece of packthread. It is under this farm that it is
sold in the shops.
If any doubts are entertained of such mixture being
genuine, a comparison which may easily be made be-
tween the very high price of white lead, which requires
iio subsequent preparation, and the very inferior price
of ceruse, which must undergo a more tedious process
immediately after it is removed from the influence of
the acid fumes, will be sufficient to show the effect of
adulteration. White lead, indeed, costs three times
the money that cei'use does.
Manufacturers are not always scrupulous in regard
to the choice, nor even the quantity, of the earthy sub-
stance which they mix with the oxide. Some employ
Spanish white, or exceedingly white tobacco-pipe clay,
and adhere to certain doses, which they never exceed ;
but others employ white of Troy es, or washed chalk,
which they add even to excess. These diflerences, re^
suiting from operations on a large scale, which are sub-
ject to no inspection for the security of commerce, render
it necessary to be careful jn the purchase of ceruse.
The heaviest, under a given volume, as well as that
which does not effervesce when an acid is poured over
it, ought to be preferred. Chalk does not give to paint-
ing the same whiteness and the same body as white
day.
U3
294 TREATISE ON \V\RNISHE3.
Besides these adulterations, practised in large manti-
làctories, others are practised in the retail shops, w hich
however may be detected. A second mixture of chalk
is added ; but in this case the ceruse is sold in powder,
and not under the form of cakes. This fraud, there-
fore, may be avoided by purchasing no ceruse except
that WTapped up in the manner in which it comes from
the manufactory. The most certain indication of an-
other mixture of chalk is the higher price asked for
ceruse in calves than for that in powder, notwithstand-
ing the additional labour, and the loss occasioned by
pulverization.
Of these two preparations of lead, ceruse only is
enaployed in the application of varnishes used for va-
luable furniture and for pictuies ; but painters are ac-
quainted with other substances Y.iiicli may be substi-
tuted in its stead.
The Dutch once engrossed this kind of manufacture
entirely ; but .within these few years new manufactories
have been established in England, France, and Italy.
Some Marseillese have established one at Leghorn since
the revolution ; and two or three years previous to the
conquest of Tuscany were sufficient to confirm its suc-
cess.
This oxide, dissolved agam in vinegar, and made to
crystallize, gives acetite of lead (salt or sugar of lead).
Roiien 7vhite.
Rouen white is a kind of marl (clay and carbonate
of lime or calcareous earth), which is mixed with water
to separate from it the sandy or coarse particles. The
1
ROUEN WHITE. TROYES WHITE. 295
water is decanted, while still chai'ged with the lightest
matter, which forms a sediment by rest. When this
deposit has acquired the consistence of a paste, it is
taken out, and divided into small masses of about a
pound weight each.
The mixture of chalk (carbonic acid united to lime)
with clay renders the latter less fit than if pure for
painting in oil, or for varnish. This white, however,
ÎS better for that purpose than the white of Troyes*
JVhite of Troyes, white chalk.
White of Troyes is a carbonate of lime (carbonic acid
united to lime), known commonly under the denomi-
nation of chalk. It takes its name from the tovm near
which it is found, and where it forms beds of consider»
able extent.
This white is often mixed with portions of sand,
silex (common flint), and other impurities, from which
it must be freed. This is accomplished by washing, as
already described in the article on Rouen white. This
white is sold under the form of large square cakes,
weighing ten or twelve pounds each, and of rolls and
cylinders of from sixteen to twenty ounces. It is cut
also into long square sticks, to give it the appearance
of tobacco-pipe clay, -none of the qualities of which It
possesses. This is a fraud which may be easily de-
fected by means of strong vinegar, which, with chalk,
produces an effervescence ; but which has no acdon on
- tobacco-pipe clay, nor on real Spanish white.
The use of chalk for the common white-washing of
apartments is generally prevalent j but gypsum is far
U.4
296 TREATISE ON VARNISHES.
superior. It serves also for different grounds, either
coloured or not, which are applied in distemper. It is
rendered more durable by being mixed up with size.
But if it be employed as priming, destined to receive
colouring parts, the washing it is subjected to in the ma-
nufactories is not sufficient : it must be made to undergo
the same operation a second time, when not sepa-
rated from those parts which escape washing on too
large a scale. The application of it in the preparation
of paper hangings is prejudicial to certain colours, and
particularly to Prussian blue. Chalk carefully washed is
not attended with the inconvenience of altering and
destroying the colours.
The first advantage arising from large manufactories
is the œconomy which may be introduced into every
branch of them ; and particularly in regard to the
number of workmen. When a common matter is em-
ployed, pulverization by the hand becomes ve^y ex-
pensive. A mill or a turning muller will perform, in
a few hours, what could not be accomplished by seve-
ral workmen in the course of as many days.
In the operation here alluded to, the matter is placed
on a flat stone, in order to be pulverized by a vertical
rauller, which revolves in that position. Washing com-
pletes the separation of the parts most attenuated from
those which stiil require some more revolutions of the
muller, if the matter be received in a close hair sieve.
It is treated with a large quantity of water, and the
mixture is stirred with a clean broom. A sediment is
speedily formed by a little rest. The supernatant water
is reddish : when the water has been decanted, the de.-
WHITE OF ZINC. 297
posit, for the greater security, is mixed up with a new
quantity of the same liquid, and as soon as a sediment
is formed it is separated in the same manner. The
precipitate acquires the consistence of a paste, which is
divided into small portions to facilitate its desiccation.
This matter when washed, as here described, exercises
no action on compound colours ; and Prussian blue
(prussiate of iron), according to the account of an in^
genious manufacturer of paper hangings, experiences
no more change from it. Carbonate of lime (chalk),
which has not been washed, produces the same effect
on prussiate of iron as an alkali or lime would do. This
affords a new subject of research in regard to this kind
of manufacture.
White of Troyes, or chalk, is proper only for paint-
ing in distemper. With oil and varnishes it becomes
brown ; and with the latter it has the inconvenience of
splitting. Besides, it is not fit for priming, like clay
mixed with a little ceruse. Colours which admit chalk
have no lustre, for want, perhaps, of the second wash-
ing ; and they are not durable, even though the chalk
may be mixed with a little ceruse,
JVhiie of zinc. Sublimated oxide of zinc. Calx of
zinc. Fhivers of zinc.
The discovery of a white colour, unalterable by the
impression of oil, light, and vapour, has long been a
desideratum to painters. All the known compositions
of this kind were attended with the inconvenience of
assuniing, after a certain period, tints different from
i^hose which the artist was desirous of fixing. A brown-.
29S TREATISE ON VARNISHES.
ish or yellowish appearance destroyed the effect, and
left the painter very far short of what he intended.
Works of genius ought to survive in their full glory
the perishable hand of the artist, by whom they have
been successfully executed. It was, therefore, doing
a real service to painting, to ensure the hopes of the
great masters repecting one of those colours which are
chiefly employed by them in their compositions.
Guyton de Morveau thought he should be able to
discharge this task reserved to chemistry, by substituting
sublimated oxide of zinc (flowers of zinc) for the oxides
of lead and bismuth (white lead and calx of bismuth),
the use of which was attended with discouraging incon-
veniences. For this purpose he employed the utmost
care in the establishment of a manufactory of the sub-
limated oxide of zinc, in order that he might give
effectual assistance to the art of painting.
JMetallic colouring substances have at all times been
considered by painters superior in one point to earthy
matters, and to those extracted from the vegetable
kmgdom. They unite much better with the oil used in
mixing them up, and they produce, under the influ-
ence of the light, more extensive effects, as well as
mellower and better maintained tones, in consequence,
no doubt, of their solidity and particular texture. In
this respect the application of the oxide of zinc to the
sublime kind of painting, formed an acquisition the
more valuable as it completely superseded the necessity
Cîf using other oxides ; which, for very good reasons,
ought long ago to have been confined to common paint'
ing and house-painting.
\1'HITE OF ZINC, 299
In arts which require long experience, before it is
possible to form a correct judgment in regard to new
processes, the desired end can be attained only by de-
grees. Some painters find this oxide of ^inc too dry ;
and, in consequence of this prejudice, they choose ra«
ther to expose themselves to inconveniences which they
have always dreaded, but with the limits of which they
are acquainted, than undertake trials which they fear
still more, because they are ignorant of the bounds of
their results. Routine very often multiplies difficultly :
at any rate it does not seem calculated to remove, nor
even to lessen them. We are inclined to believe that
in the present case it is more powerful than reasoa.
Time alone can determine what advantages will be de-
rived from the use of this oxide. In similar cases com-
parative trials overcome all difficulties, and exhibit every
thing in its proper light. The trials, therefore, may
be varied, by comparing the effects of this oxide with
■those of the two oxides in som.e measure proscribed,
and those exhibited by that kind of Cremnitz white the
composition of which I have already described. The pro-
cess is easy, and may be performed by any one. It may
even be varied in regard to the addition of white clay.
Sublimated oxide of zinc is obtained by fusing that
metal in an earthen tube, which performs the office of
a crucible, and which is placed obliquely in a reverbe-
rating furnace, or in any other capable of producing a
heat sufficient to make it enter into fusion. The metal
then soon inflames, and emits thick white fumes, which,
if the zinc be pure, are converted into very white
woolly /lakes. These flakes, which adhere to the sides
SCO TREATISE ON VARNISHES.
of the tube, are called sublimated oxide of zinc
(flowers of zinc).
If the zinc contains iron, the oxide is of an orange-
yeliow colour : the metal is purified by throwing into
it, while in fusion, some pinches of the flowers of sul-
phur.
Azure, Enamel blue. Sqffer blue. Saxon blue.
Vitreous oxide of cobalt.
Painters make use of a vitreous matter, which derives
its blue colour from the oxide (calx) of a metallic sub-
stance called cobalt.
It is manufactured on a large scale in Saxony, where
mines of cobalt are abundant. From this circumstance
only it has acquired the denomination of Saxon blue.
Cobalt is not produced by nature in a state of purity.
It presents itself to the miner mixed with earths and
stones, united to sulphur or arsenic, and often to both.
These, however, are not the only matters from which
it ought to be separated ; its ore contains, for the most
part, bismuth, nickel, and silver. The working of it is
attended with many difficulties, which render it neces-
sary to multiply the processes. The first operation is
that of roasting. The ore is broken, to separate it from
|the stones ; and the fragments abundant in ore are
placed apart, in order to be subjected to calcination.
Those which contain a great deal of stony matter are
carried to the stamping mill. As this pulverization is
effected in running water, the water carries with it the
stony parts, which are hghter than the ore, while the
latter reniains partly in the trough, and partly in the
AZURE. SAXON BLUE.- i?Ot
first reservoir. The pounded ore is then dried, and
afterwards roasted^
Roasting is performed by causing flame to be rever*
berated on the matter. The part which supports the
ore has the form of a very fiat spheroidal segment, in
the middle of which is a cavity shaped like a crucible,
to receive the bismuth, which proceeds thither on the
fii*st impression of the caloric (tire). During the ox-
idation (calcination) of the cobalt, the sulphar and
arsenic are volatilized ; the first under the form of sul=»
phuric and sulphurous acid gas, and the second under
that of oxide of arsenic. The latter, in becoming sub- •
limed, covers with white and black flakes the whole
interior part of a long gaUery.
When the cobalt ore has been roasted to the proper
degree, it assumes the colour of wine lees. It is then
mixed with four or five parts of silex (common flint)
pounded in a mill, after it has been brought to a white
heat, and quenched in cold water, that its parts may
more easily be divided. This mixture, known under
the name of safter, is employed by potters mixed with
a portion of an alkaline salt, as a blue colour for their
earthen-ware.
Azure, enamel blue, Saxon blue, smalt, or vitreous
oxide of cohall, is saffer reduced to blue glass by the
action of a violent fire. The more the glass is charged
with oxide of cobalt, the intenser the blue colour be-
comes. This vitrification is facilitated by the addition
of a certain quantity of carbonate of potash (alkali of
potash), or carbonate of soda (effervescent alkali of
soda).
S02 TREATISE ON VARNISHES,
Smalt, or the vitreous oxide of sailer, reduced to
coarse powder, is distinguished by the name of coarse
Saxon blue, or enamel blue. Some pretend that it is
four times fused and pulverized, after it has been pour-
ed in a liquid state into a certain quantity of water.
This blue is employed in oil painting, and in some
kinds of distemper.
This vitreous ozàde of saffer requires great care be-
fore it can be applied to delicate kinds of painting. It
must be ground for a very long time ; and as the glass
is exceedingly hard, this mechanical labour, to many
painters, is highly disagreeable. It is destined for dra-
pery of a soft blue colour ; but it is attended with the
fault of being somewhat dry, and this is owing to the
vitreous nature of its composition, which prevents it
from adhering to the canvas, and irom forming a body
with other colours. Were it not for the tenacity of the
oil, which serves it as cement or varnish, it would fall
into dust.
The great consumption which the Genevese artists
make of blue extracted from cobalt, and the difficulty
they have often experienced to obtain it of a degree of
fusibility suited to the delicacy of enamelled articles,
have sometimes obliged them to prepare the oxide
themselves from the ore. It was for their use, in par-
ticular, that 1 have detailed the processes employed for
that purpose.
Ultramarine.
Ultramarine is extracted from Iripif; lazuli, or azure
stone, a kind of hea^y zeolite, which is so hard as to
strike fire with steel, to cut glass, and tp be susceptible
ULTRAMARINE. $0^
of a fine polish. It is of a bright blue colour, varie-
gated with white or yellow veins, enriched vidth small
metallic glands, and even veins of a gold colour, which
are only sulphurets of iron (martial pyrites). It breaks
irregularly. The specimens most esteemed are thos^
charged with the greatest quantity of blue.
It is found in Asia, particularly in Persia, and in
the kingdom of Golconda. A beautiful kind of it is
brought also from Siberia, Prussia, and Spain ; but it
is not so hard as that of Asia. The Romans, who set
a great value on this stone, rendered it so common m
Italy that it has been employed for mosaic painting : in
a word, they extended the use of it so much, that tliey
introduced it by way of decoration in their buildings
\dth the same profusion as common marble. The
Jesuits, who earned on a great trade with it, contri-
buted not a little to make it subservient to the luxury
of the arts.
The operation of extracting ultramarine from lapi^
lazuli having been much encouraged by the excessive
price given for this truly valuable colour, the abun-
dance of it has occasioned a considerable diminution of
the stone which produces it. This inconvenience has
been followed by another. The present price of ultra>
marine is superior to that of gold. It is even probable
that it will still increase in proportion to the scarcity of
thç stone, which has become greater since the sup-
pression of the order of Jesuits, and by the dispersion
of it in consequence of the general revolution \i'hich has
token place in the political state of the ecclesiastical do-
minions»
804f Treatise on varnishes.'
Several artists have employed their ingenuity on pro-
cesses capable of extracting ultramarine in the greatest
purity. Some, however, are contented with separat-
ing the uncoloured portions of the stone, reducing the
coloured part to an impalpable powder, and then grind-
ing it for a long time with oil of pinks. But it is cer-
tain that, in consequence of this ineffectual nrethod, the
beauty of the colour is injured by parts which are fo-
reign to it ; and that it does not produce the whole
effect which ought to be expected from pure ultra-
marine.
The most beautiful ultramarine and the richest in
colour has, over the best prepared Prussian blue, the in-
valuable advantage of uniting in a natural manner with
the fins carnation of beauty. It is superior to Saxon
or enamel blue in the richness and mellowness of its
tone. It is not sandy like Saxon blue ; it never de-
ceives by the effect of time the hope of the artist who
has applied it. In this point of view alone it is worth
a greater price than has been fixed on it.
When considered, therefore, in its full splendour,
and with all its attributes, it is rather a production of
art than of nature. At any rate, if nature performs
the first part, art disengages it from all substances fo- ,
reign to its composition, and makes it appear with its
înost valuable characters. ;/
It maybe readily conceived, that these eminent qua-*,
lities must have induced those first acquainted with ths
processes proper for increasing the merit and value of
it to keep them a profound secret. This was indeed' the
case. Ultramarine was prepared long before any account.
ULTRAMARINE. 305
of the method of extracting and purifying it was known.
'The first writer who speaks of it is Ansehn de Boot, who
describes the preparadon of it in his Treatise on Pre-
cious Stones. After him, Kunckel and Neumann, who
employed themselves on the same processes, speak of
them also, but without entering into minute details.
They were satisfied with giving the most essential obser-
vations necessary to facilitate the complete extraction
of the colouring part.
Kunckel separates from the stone the most apparent
parts of the ultramarine ; reduces them to the size of
â pea, and, having brought them to a red heat in a cru-
cible, throws them, in that state, into die strongest
distilled vinegar. He then grinds them with the vine-
' gar, and reduces them to an impalpable powder. He
next takes a quantity of wax and colophonium, equal
to that of the lapis lazuli, that is to say, an ounce or
half an ounce of each of these three substances ; melts
Ûie wax and the colophonium in a proper vessel, and
adds the powder to the melted matter ; then pours the
mass inip cold water, and leaves it eight days at rest.
He next takes two glass vessels filled with water so hot
that the hand can scarcely bear it ; kneads the mass in
the water ; and when he concludes that the purest part
of the ultramarine has been extracted, he removes the
resinous mass into the other vessel, where he finishes
the kneading to separate the remainder. The latter por-
tion appeared to him to be much inferior, as it was
paler than the former. He then leaves it at rest for
four day6, to facilitate the precipitation of the ultra-
5d^ T^REATI^E O^ VARNISHES.
marine, which he extracts by décantation, and wasfies,
no doubt, in pure water.
According to the remark of this author, ultramarine
of four quaHties may be separated by this process. The
first separation gives the finest : as the operatic^s are
repeated the beauty of the powder decreases.
Kunckel considers immersion in vinegja? as the essen-
tial part of the. operation. It facilitates, no doubt, the
division and even the solution of the zeolitic and earthy
particles soluble in that acid.
Neumann*s process is much shorter. He first sepa-
rates the blue parts, and reduces them, on a piece of
porphyiy, to an impalpable powder, which he besprin-
kles v.-ith linseed oil. He then makes a paste with equal
parts of yellow wax, pine resin, and colophonium, that
is to say, eight ounces of each ; and adds to this paste
half an ounce of linseed oil, two ounces of oil of tur-
pentine, and as much pure mastic.
He then takes four parts of this mixture, and one of
lapis lazuli, ground with oil on a piece of porphyry^
mixes the v/hole warm, and suffers it to digest for a
month. At the end of that period he kneads the mix-
ture thoroughly in warm water, till the blue part sepa-
rates from it, and at the end of some days decants thé
Hquor. This ultramarine, he says, is exceedingly
beîwtiful.
These two processes are nearly similar, if we except'
the preliminary preparation of Kunckel, which consists
rn bringing the lapis lazuli to a red heat, and immer-
stjig it in vinegar. Jt may be readily seen, by the ]«.-'
ULTRAMARINE. S07
cKcious observations of MargrâfF on the nature of this^
colouring part, that this calcination may be hurtful i6
certain kinds of azitre stone. This preliminary opera-
tion, however, is a test which ascertains the purity of
the ultramarine.
As this matter is valuable, some portions of ultra-
marine may be extracted from the paste which has been,
kneaded in water. Nothing is necessary but to mix it
with four times its weight of linseed oil ; to pour the
matter into a glass of a conical figure, and to expose
the vessel in the balneum marias of an alembic, the
water of which must be kept in a state of ebullition
for several hours. The liquidity of the mixture allows
the ultramarine to separate itself, and the supernatant
oil is decanted. The same immersion of the colouring
matter in oil is repeated, to separate the resinous parts
which still adhere to it ; and the opei'ation is finished
, by boiling it in water to separate the oil. The deposit is
ultramarine j but it is inferior to that separated by the
first washing.
JMelhod of ascertaining ichether ultramarine bs
adulterated.
As the price of ultramarine, which is already very.
high, may become more so on account of the difficul-
ties of obtaining lapis lazuli, the sources of which seem
to have been nearly exhausted,- it is of great import-
ance that painters should be able to detect adultera-
jtions, which the spirit of avarice introduces into all
j articles of value. Ultramarine is pure if, when brought
I to a red heat in a crucible, it stands that trial without
X 2 "
308 TREATISE ON VARNISHES.
changing its colour. As small quantities only are sub-
jected to this test, a comparison may be made, at very
little expense, with the part wliich has not been ex-
posed to the fire. If adulterated, it becomes blacldsh
or paler.
This proof, however, may not always be conclusive
when ultramarine of the lowest quality is mixed with
azure or Saxon blue; but if it be mixed with oil, it is
found to have very little body compared with its bright-
ness. It is well known that vitreous matters, such as
azure, exhibit no more body than sand ground on por-
phyry would do : ultramarine treated with oil assumes
a brown tint.
If the painter is satisfied with enjoying in its full
plenitude a present of nature exceedingly valuable to
his art, without any desire of knowing the principles
of its composition, the case is not the same with the
naturalist and the chemist. The more valuable an
article appears to be, by the service which it renders
to the arts, the more worthy they consider it of re-
search.
This colouring matter, therefore, did not fail to
excite the curiosity of chemists. Some, guided by
particular results, ascribed it to copper. Others, by
extrrxting a few grains of silver from certain kinds of
lapis lazuli, thought themselves authorised to ascribe
the colour of it to that metal. Margraff, a celebrated
chemist of Berlin, asserted that it was indebted for it
to iron in a particular state. The sulphates of iron
(majtial pyrites), which oftçn heighten the splendour
of this substance, afford some reason for admitting in i
I
PRUSSIAN BLUE. ^9
It this metal : Klaproth is of the same opinion. Does
it exist in it under the form of prussiate of iron (Prus-
sian blue) modified by a mixture of earthy principle ?
The truth of this conjecture can be ascertained only by
direct experiments. C. Guyton read in the National
Institute, in the year 1 SOO, some observations on the
colouring principle of lapis laxuli, which seem to
show that it arises from a particular combination of
iron and sulphur. He was led to this conclusion
by the result of an experiment made, in a strong
heat, with a mixture of charcoal-powder and gypsum,
coloured red by iron. Though the artificial ultrama>
rine which this chemist extracted from it did not answer
the expectation of eminent painters, it is still a dis-
covery highly interesting to theory. Perhaps it might
be substituted for prussiate of iron, which many pain-
ters employ, but without placing much confidence
in it.
Prussian blue, Prussiate of iron.
Prussiate of iron (Prussian blue) is the result of a
combination of iron with an acid of a peculiar nature,
distinguished by the name of the Prussic acid.
The discovery of this blue, like many other things,
was the mere effect of chance. Dippel, a chemist of Ber*
lin, having thrown into his court-yard several liquors
which he considered as of no further use, or in order to
free his laboratory from them, observed with surprise that
some of the stones were covered with a very bright blue
colour. He then recollected that he had before thrown
out, in the same place, the remains of a solution of sul^
phaté of iron (martial vitriol, green vitriol) j and as these
X 3
SIO TREATISE ON VARNISHES.
liquors were of an alkaline nature, and had been re-
peatedly employed for the rectification of oil of harts-
horn, he thought he had now found the key of a dis-
covery which appeared to be of great importance. He
therefore directed his researches towards this" object,
p,nd, after some successful experiments, found means
to compose Prussian blue by a sui^e process.
At the commencement of the eighteenth century
chemistry v/as merely a science of results. The theories
applied to a certain aggregate of these results were
often the mere offsprings of the imagination. Macquer,
the celebrated author of the Dictionary of Chemistry,
seems to have fixed for ever the ideas of chemists in
regard to the prussiate of iron, by supposing the alkali
completely saturated with a particular matter, which
Jie calls the colouring matter of Prussian blue, and
•which, from the characters of its union with the alkali,
he supposed to be of an acid nature.
Animal analysis, which has been so much extended
under the reign of the pneumatic chemistry, was at
that time covered by an impenetrable veil. The part,
at least seen by chemists, was confined merely to de-
tached and unconnected fragments. As this colour-
ing matter exercised its action only under the cover of
combination ; and as it eluded ail direct researches, and
every method employed to effect a separation of it;
the public opinion was divided respecting it till its
nature was ascertained by the ingenious experiments oj
Macquer.
By uniting prussiate of potash (alkali saturated with |
the colouring part, of- Prussian blue) and a solution oi
5 ■ ■
PRUSSÎATE OF IRON, 311
sulphate of iron (martial vitriol), he observed the ef-
fects of a double decomposition and a double combi-
nation. The Prussic acid (the colouring part of Prus-
sian blue) abandoned the alkaline base to join the iron,
which it converted into Prussian blue; while the sul-
phuric acid, which existed in the sulpliate of iron,
joined the alkali, to form sulphate of potash.
This particular substance, before distinguished by
the name of the colouring part of Prussian blue, is
therefore an acid; and in the new Nomenclature Ls
called the Prussic acid. Its union with iron forms
prussiate of iron (Prussian blue), and its affinity for
that metal is so great that the strongest mineral acids
cannot separate them.
Alkalies and lime take it from iron. These sub-
stances become saturated with it ; and in this state of
saturation they can regenerate the prussiate of iron,
when its favourite metal, combined with an acid, is
presented to it. This circumstance is indispensably
necessary to effect the double decomposition and double
combination observed by Macquer.
It was reserved for one of the first chemists of mo-
dern times to penetrate further into the mystery in
which this singular combination was still involved.
Berthollet employed himself in researches on Prussian
blue ; and it results from his experiments that the prus^
sic acid is a combination of azote, hydrogen, and car-
bon, the proportions of which are not yet known*;, •
* According to the new nomenclature, that part" of atmo-
spheric air which is neither tit for respiration nor combustioii
iç named azote. It forms three-fourths of atmospheric air^, an4
X 4
S12 TREATISE ON VARNISHE5.
When prussiate of iron is pure, its volume does not
decrease in acids, nor does it acquire a more intense
colom'. When it loses part of its volume, and acquires
greater strength of colour, this indicates a mixture
of alumine (the base of alum), which is often intro-
duced into its composition. In this case, to obtain it
pure, it must be treated v/ith muriatic acid (marine
acid), and washed with clean water: it is then thrown
on a filter to separate the water from itj after which it
Is dried.
This colouring substance participates with many other
productions of art in the inconveniences resulting from
operations on an extended scale. Its colour is not uni-
form and constant. Common prussiate is of a pale
blue colour, and sometimes exhibits even a greenish
tint. The mixture of alumine (alum earth) will serve ■ i\
exists in it in the state of gas, by its union \\ith caloric. Oxygen
gas, kno\\'îi formerly by tlie name of pure air, constitutes about
one-fourtli part of atmospheric air, \\ithout including the acciden-
tal mixture of other gaseous fluids.
The base of the fluid distinguished formerly by the rnme of *
înftammable gas is now called Jnidroiyai. When united to caloric
. jt becomes Iii/a'rogcn gas. This expression has been substituted lor
the former, since tlie discovciy^ of the decomposition of \\ater, of ^.
wiiich it is a component part. -"
Carbon, according to Berthollet, is common charcoal freed
from the hydrogen and oxygen which were united with it.
These different elements abound in the animal organization. It
needs therefore excite no astonishment, if alkali exposed to heat
^^ ith animal substances sh.ould become saturated with these prin-
cii>les, which the fire mcdlties in such a mantier as to form of Zj
lliem a new acid, without the concurrence of oxygen, which ^
seems to reserve to itself the privilege of acidification.
ARTIFICIAL SAXON BLUE. SIS
to explain the first effect; but the shade of green de-
pends on the state of the prussiate of potash, which is
not completely saturated with prussic acid. In this
case the free alkaline part, that is to say, the portion
not occupied by the acid, precipitates a relative quan-
tity of the sulphate of iron, in the state of yellow oxide,
the mixture of which with the true blue of the prussiate
gives rise to a compound colour, which is green. Tliis
oxide of iron is easily separated by immersing the prus-
siate in muriatic acid (marine acid).
Prussiate of iron acts a distinguished part in house-
painting, and even in other kinds. It is, however,
often attended with one inconvenience. When ground
-with oil it assumes a yellow tint, which some ^eat
masters correct by a little violet Jake. This yellotv^
tint seems to arise from the action of the oil. An-
other fault which seems to confine the use of this
colour is, that the blue it produces is hard, and does
not seem to harmonize with that fine carnation which
gives chamis to the physiognomy when artfully inter-
sected by beautiful veins. Ultramarine alone answers
this purpose when employed by the hand of an artist.
uArtiJicial Saxon blue made luith prussiate of iron,
Saxon blue may be successfully imitated, by mixing
'with a divided earth prussiate of iron at the moment of
fe formation and precipitation.
Into a solution of 144 grains of suphate of iron
(martial vitriol) pour a solution of prussiate of potash
(alkah of potash saturated with prussic acid). At the
time of the formation of the prussiate of iron add^ in
,3.14? TREATISE ON VARNISHED,
the same vessel, a solution of two ounces of sulpha!^ .
,o{ alumine (alum) ; and pour in, at the same time, the
solution of potash, — ^but only in such a quantity as may
be supposed necessary to decompose the sulphate of alu-
mine; for a dose of alkali superabundant to the decom-
position of that salt might alter the prussiate of iron.
It will, therefore, be much better to leave a little alum,
which may afterwards be carried off by washing.
As soon as the alkaline liquor is added, the alumine
precipitated becomes exactly mixed with the prussiate
of iron, tlic intensity of which it lessens by bringing
it to the tone of common Saxon blue. The matter is
then thrown on a filter, and after being washed in,
clean water is dried. This substance is a kind of blue
verditer, the intensity of which may vary, according
to the greater or less quantity of the sulphate of alu-
mine decomposed. It may be used for painting m
distemper.
Blue verdiier.
Nature presents, in certain parts of copper mineSj^.
a blue colouring matter which is known by the name
of malachite. For the most part it is found in solid'
masses, but sometimes in crystals. By pulverization
it acquires nearly the appearance of that powder which .
painters call blue verditer. It is a natural oxide of,
copper: but, however fertile nature may be in pror
ducing it, the great consumption made of blue ver-
diter leaves no doubt that this matter, which was forr
merly procured from Germany, and which is no\y
obtained from England, is a result of art, in ^vhich thp
ELUE VERDITER.. 51$
copper is brought to a degree of oxidation not always
easy to be imitated.
It was long imagined that blue verditer was the pro-
duct of a preparation, in which lime, muriate of am-
monia (sal ammoniac), and copper, dissolved by a mi-
neral acid, were acting and constituent parts. This,
at least, was the opinion of Rouelle junior, a man
justly celebrated in .chemistry.
It was reserved, however, for his learned colleague
Pelletier to unite the synthesis and analysis he had given
of it, and to discover the circumstances which promote
or oppose, during the time of the operation, the de-
velopment of the blue colour. An interesting detail
of the various processes he employed, to procure to
his country the fruits of a new manufacture, may be
seen in the Annales de Chimie*.
Most of the metallic oxides obtained by precipita-
tion contain, besides a portion of oxygen, a consi-
derable quantity of carbonic acid, (formerly called
fixed air, an union of oxygen and carbon). From th.e
results of Pelletier's experiments, it appears to be
proved, that the colour of the crystals of mountain
blue or malachite, and that of blue verditer, cannot
be ascribed to a combination of the oxide of copper,
lime, and carbonic acid, but rather to a certain degree
of the oxidation of the copper. Tliis theory, if I re-
collect, corresponds exactly with that given by Mor-
yeau, some years before, to explain the cause of the
jîifference of the colour of mountain blue arid green»
* Yoi. xiii. p. 47.
SIS TREATISE ON VARNISHED,
"Every precipitation, therefore, of copper, or every
hyper-oxygenated natural oxide of copper, such as
mountain green or malachite, will not give blue when
treated with lime, but will always remain green. în
the process employed to make" blue verditer, the lime,
according to the remark of the author, seems to act
Oft the oxygen contained in the precipitate, and to
diminish the proportions. It is to this particular cir-
cumstance that we are indebted for the conversion of
the blue colour into a green colour, which is constant
m precipitates of copper.
The process for the composition of blue verditer
seems, on the first view, to be simple ; the success of
it, however, is often the fruit of long practice. As
too circumstantial details are not suited to a work of
this kind, I shall confine myself to the most essential
points of the operation. An expert chemist may easily
supply the rest.
Dissolve the copper, cold, in nitric acid (aquafortis),
and produce a precipitation of it by means of quicklime,
employed in such doses that it shall all be absorbed by
the acid, in order that the precipitate may be pure
copper; that is to say, without any mixture. When
the liquor has been decanted, the precipitate is washed,
and spread out on a piece of linen cloth to drain. If
"a portion of this precipitate, w^hich is green, be placed
on a grinding stone, and if a little quick-lime, in
powder, be added, the green colour will be imme-
diately changed into a beautiful blue. The proportion
of the lizne added is frcm seven to ten parts in a him-
GREEN VERDITER. 317
ilred. As the whoie matter has already acquired the
consistence (^jLpaste, desiccation soon takes place.
A quintal of blue verditer, prepared in this manner,
gives the same proportions as those discovered by Pel-
letier in the component principles of the best English
blue verditer, which are :
Carbonic acid - - - - SO parts.
Water -34
Pure lime ----- 7
Oxygen ------ 9-^
Pure copper ----- 50
100
Blue verditer is proper for distemper and for ^'^r-
nish ; but it is not fit for oil painting, as the oil renders
it very dark. If used, it ought to be brightened with a
great deal of white.
-Green verditer. ,
Green verditer does not require the same care in the
preparation. It is the general result of the precipitation.'
of copper, dissolved in the nitric acid (aquafortis),
effected by means of chalk or a white marl. In the
latter case, the divided clay, which forms part of it^,,.
gives pliability to the verditer, when employed as a co-
iour. If too much charged with copper it would not
be ht for oil painting, as the oil would produce too
4ark a green. In this case it must be corrected by the
addition of a httle ceruse or Spanish white.
This colour, however, is much better calculated for
distemper j and the painter may supply its place in oil
S18 TREATISE ON VARNII^HES.
painting with verdegris mixed with two or three part§
to one of ceruse. With^very slight do^ of verditer
the lightest shades of sea-green may be represented.
Cinnabar. I'ermiUon. Red sulpJiurated oxide of
vierciiry:
The metallic combinations which constitute the
greater part of ores depend on a kind of operations
which nature performs in silence ; which she varies,
and wliich it was reserved for the modern chemistry to
discover. Cinnabar, that natural combination of sul-
phur and mercury, affords a specimen of these results.
Seven parts of mercury and one of sulphur form that
brilliant needly m.as?,- of a beautiful red colour, the
brightness of which depends on proper proportions of
tlie two component principles, as well as on the greatest-
possible division of them. Cinnabar, indeed, assumes
a very high colour oPxly under the muller. When di-
vided in this mechanical manner, it exchanges the name
of cinnabar for that of vermilion.
Nature rarely exhibits this substance in large masses .
and crystallized. In this respect art is superior, since
rt prepares it in large masses, and endowed with all
the required qualities. It is manufactured chiefly in'
Holland.
The sulphur is liquefied in large earthen jars, or in
iron pots, and the mercury is mixed in the proper'
doses. These two matters become heated to such a'
degree, by the mere effect of the combinadon, as to'
inflame ; and when this result takes place the cinna-
bar is more easily sublimated, because the excess of
IS
Or:
CINNABAR. VERMILION. NAPLES YELLOW. 319
siirphur is destroyed. The matter when cold is pul-
Srèrized, and made to sublimate in" flat earthen vessels,
which are covered by other vessels of the same sub-
stance. These sublimating vessels are arranged in long
sand furnaces called galleries, where the sublimation
is effected only by a very strong heat.
■ If the first sublimation does not produce cinnabar
capable of displaying, when ground, a beautiful colour,
the matter is subjected to a second sublimation, the
eiFect of which is to destroy the quantity of sulphur
greater than that essential to the most perfect combina-
tion in regard to the tone of coloiu* required in ver-
itlinilion.
The splendid colour of the vermilion employed for
carriages is owing to this composition. It is employed
also for painting other articles ; for colouring sealing
wax, and, in general, for all ornaments which require
a high strong colour agreeable to the eye : of course,
it is proper for painting of every kind.
Vermihon has no rival but carmine, which, though
it produces a mellower and duller colour, is no less
pleasing to the eye.
s to'
Naples yellow. Iclloiu oxide of lead mioced with 2vhite -
oxide of antimony hy nitre.
It is not long since the nature of Naples yellow was
nown. It was formerly believed to be of volcanic
)rigin ; and arsenical qualities were ascribed to it, in
onsequence of its yellow colour, which gave it some
esemblance to orpiment ; and on account of the green,
olour communicated to it by iron and steel. This
320 TREATISE ON VARNISHES,
effect, generally known to painters, renders it necessary
in grinding this colour to employ porphyry and an ivory
spatula.
All these uncertainties, however, were at length
cleared up by the chemical discovery of this composi-
tion, the secret of preparing which v/as in the posses-
sion of a Neapolitan far advanced in life. Without
dwelling on the circumstance of the age of the person
"who possessed this secret, and the extensive use made
of this preparation, which is fit for painting of everj
kind, without excepting enamel and porcelain painting,
great merit is to be allowed to the researches of Fou-
geroux, who found means to give to this compositioi|
a certain effect.
The possessor of the secret mixed calcined lead wit
a third of its weight of antimony, pounded and sifted,
and exposed the mixture to a potter's furnace. Fo
geroux de Bondaroy obtained the result by modifyinj
the formula in the following manner* :
i
Composition.
Take twelve ounces of ceruse, two ounces of thd
sulphuret of antimony (common antimony), half
ounce of calcined sulphate of alumine (calcined alum
and an ounce of muriate of ammonia (sal ammoniac)J
Pulverize these ingredients, and having mixed th
thoroughly, put them into a capsule or dish of crucib^'j^'^
earth, and place over it a covering of the same sul
stance. Then expose it at first to a gentle heat, whi
must be gradually increased till the capsule is mo
* MefliQÎ.res deJ['.Aca4iï»le (Jes-Scie^^ee ilf /^2.
I
ÏTAPLES YELLOW. 321
rately red. The oxidation arising from this process
requires at least three hours' exposure to heat be-
fore it is completed. The result of this calcination is
Naples yellow, which is ground with water on a por-
phyry slab by means of an ivory spatula, as iron would
alter the colour. The paste is then dried, and preserved
fbr use. It is a yellow oxide of lead and antimony.
^ The author observes, that there is no necessity of
adhering so strictly to the doses as to prevent their being
varied. If a golden colour be required in the yellow,
the proportions of the sulphuret of antimony and mu-
riate of ammonia must be increased. In like manner,
if you wish it to be more fusible, increase the quanti-
ties of sulphuret of antimony and calcined sulphate of
alumine.
I have remarked that sulphuret of antimony, which
contains a little iron, like that of Savoy, and sometimes
' that of Auvergne, and which for this reason assumes
(after its oxidation a yellow colour, is the most proper for
this kind of composition. I have several times supplied
this natural want by stirring with a spatula of soft iron
white oxide of antimony by nitre (diaphoretic' anti-
mony), when in a state of fusion.
A kind of yellow from lead, in cakes half an inch
m thickness, the edge of which exhibited a needly
crystallization, was formerly brought to us from Eng-
land. Painters who made use of il knew that muriate
of soda (common salt) entered into this composition;,
the process foi' preparing which is a*^ follows :
I.,
322 -Treatise on varnishes*
Montpellier y elloiv. Yellow oxide of lead ly tliC
muriatic acid.
C. Chaptal, formerly professor of chemistiy at Mont-
pellier, naturalized in France this preparation, by esta-
blishing a manufactory of it in his native town. The same
process furnished matter for making metallic yellow,
and separated at the same time the alkali from the soda,
which serves as a base to sea salt. At that period the
French government encouraged chemists to make re-
searches respecting the means of obtaining this alkaline
salt, at such a price as might enable it to stand in com-
petition ^^ith the potash obtained from foreign coun-
tries, and to supply its place in the time of war. The
proportions, in case of necessity, may be reduced.
Take four quintals of vitreous oxide of lead (litharge),
well sifted, which must be divided into four equal por-
tions, and put into as many glazed earthen vessels.
Dissolve also one quintal of muriate of soda (sea salt)
in about four quintals of water. ?|
Pour a fourth part of this solution into each of the
four earthen vessels, to form a paste of a light consist-
ence. Leave the whole at rest for some hours, and
when the surface begins to grow white, stir the mass
with a strong wooden spatula. "Without this motion it
would acquire too great hardness, and a part of the salt
would escape decomposition.
As the consistence increases, the matter is diluted
with a new quantity of the solution ; and if tliis is not
sufficient, recourse must be had to simple w-ater to main-
tain the same state of consistence. The paste is then
MONTPELLIER YELLOW. 323
very white, and in the course of twenty-four hours be-
comes uniform and free from lumps. It is then suffer-
ed to remain for the same space of time, stirring it at
intervals to complete the decomposition of the salt.
The paste is then well washed to cairy off the caus-
tic soda (soda deprived of carbonic acid) which adheres
to it ; and to extract the whole of it, the mass is put into
strong linen cloth and subjected to a press.
The remaining paste is distributed in flat vessels ;
attd these vessels are exposed to heat, in order to effect
a proper oxidation (calcination), which converts it into
a solid, yellow, brilliant matter, sometimes crystalHzed
in transverse strias. This is Montpellier yellow, which
may be applied to the same purposes as Naples yellow.
In this mixture of vitreous oxide of lead with mu-
riate of soda, dissolved in a sufficient quantity of water,
the latter salt is decomposed. The muriatic acid aban-
dons the alkali of the soda, which served it as a base,
and joins the vitreous oxide of lead, which is converted
into muriate of lead ; and at length, by the aid of
caloric (of fire), into yellow oxide of lead. The soda
separated by the washings is caustic, that is to say,
pure, and without any mixture of carbonic acid. By
leaving it exposed to the air it becomes charged with
carbonic acid (formerly fixed air), diffused throughout
the atmosphere, and is rendered crystallizable. It is
then carbonate of soda (salt of soda). Seventy-five
pounds of soda, purer than that of the shops, is ex-
tracted from this mixture*.
•^ See Jourrifll de Physique, August 1794.
524 T*EATISÇ ON VARÏx'ISîris,
Indigo.
The East and West lîidiec, as \-'eîI as some coun-î
tries of the American continent, such as Brasil, Peru,
&c. produce a plant called by the Spaniards anillo, the
juice of which, when subjected to spirituous fermenta-
tion, gives a fecula of a blue or dark azure colour,
imported to us under the form of square flat pieces,
not very haîrd, which float on water : they are inflam-
mable, and when put into the fire are almost entirely
consumed.
The best and most esteemed is called Guatimala in-
digo, from the name of a town in Spanish America,
where it is prepared on a large scale, and with the great-
est care.
When rubbed on the nail it leaves a trace similar in
colour to the antient bronze. This character is always
much sought after ; and indigo of this kind is called
cupreous indigo.
A fecula of a blue or dark violet colour, called also
indigo, is brought to us from Brasil. It differs from
real indigo by being produced from the leaves of the
anUlo, while common indigo is formed from all the ex-
ternal parts of the plant.
The pulverization of indigo is attended with the same
iiiconveniences as that of certain colouring substances
of which clay forir-s the basis : but the operation may
be very much shortened by putting three or four eight-
pound shot into a large copper bason with the quantity
of indigo intended to be pulverized. A slight circular
motion communicated to the bason, held in the two
INDIGO* SUS
hands over a tablej Vîàll be sufficient to make the bullets
roll over the matter, and to pulverize it much betteç-
than if pounded and sifted, as in this case it often
forms itself into balls, and does not pass through the
sieve.
These two kinds of indigo can be applied only to
painting in distemper, with or without varnish. They
are not proper for oil painting, because the oil renders
them black or green, and they lose in drying a part of
the vigour of their tone. In general, indigo is not em-
ployed pure : jt is always mixed ^^ith v/hite ; if piire, i:
would become black. Ceruse, indigo, a^d a particle of
black, if the proper proportions be obser/ed, give 3
beautiful pearl gray colour. l!> distemper, indigo i^
employed for paintmg th^e sky, sea, and ^U the distant
parts of a landskip.
The use of indigo is not confined to painting in dis-
temper. When subjected to certain chemical processes,
it may be extended to miniature painting. Indigo
united to sulphuric acid (oil of vitriol) in the state of ^
solution, diluted with v^ater, gives to woollen and silk
the beaudful and solid colour of Saxon blue. This bluç
of indjgOj and the yellow of indigo produced by nitric
acid (aquafortis), when mixed in certain proportions}
give a beautifnl and soHd green, which may be em«
ployed in that kind of miniature painting which serves
to ornament silk, fans, &c.
These three colours, when intended for paper groundsj,
must be weakened with water. The mucilage proper
:^r the latter kind of painting ought to be exttact,^ noi
Y 3
S^è TREATISE ON VARNISHES.
of gum arabic, but of gum tragacanth, which has mora
body.
The works which may be consulted in regard to in-
digo are Mémoires de Qiiatremere d* lyonval, crowned
in 1777 by the Academy of Sciences at Paris, and the
Journal de Physique for July 1777? which giyes an
abridgment of them.
Of lakes.
Lakes, in general, are produced by the decomposi^
tion of sulphate of akmiine (alum), by a substance
which seizes on the sulphuric acid, and liberates the alu-
mine which served it as a basis. This earth, in pre-
cipitating itself, unites to the vegetable or animal co-
louring fecula, which passes into the bath. It is this
colouring fecula, united to alumine, which constitutes
the different carminated lakes and crayons. It appears
that the v/ord lac or lahe is of Indian extraction, and
that it is employed in that country to express a colour,
or a solid colouring part : it has therefore a particular
acceptation, which has been somewhat generalized in
our language.
The preparation of crayons, which has given birth
to a particular kind of painting, is not confined to the
chemical process above mentioned : there is one sim.pler
and less tedious ; it is that which serves as a basis to
the preparation of Dutch pinks. It consists in mixing
up with the coloured bath an argillaceous matter of the
first quality, and subjecting the whole to careful evapo-
ration, or in exposing the hquid paste on driers of | fpiti
LAKES, 327
plaster covered with a clean cloth, to prevent the
crayon from adhering to the drier.
This method is more ceconomical than the chemical
process ; but it requires a very nice choice in the qua-
lity of the white destined for the operation, and in par-
ticular the precaution of previous washing, to remove
the fine sandy parts with which the finest white clays
are mixed.
The variety observed in the tone of lakes extends
also to their qualities. They are more or less capable
of resisting the impression of the air and the light, ac-
cording to the nature of the substances from which they
are extracted. The lakes most in request are those
called carminated lakes, whatever may be the intensity
of their colour, because experience has shown that
they oppose the strongest resistance to the destructive
influence of the light. Their colouring part is extracted
from cochineal, the price of which has increased in
consequence of its intrinsic qualities in various prepa-
rations employed in the arts of painting, dyeing, and
calico printing. They are imitated with colouring parts
extracted from certain vegetable substances ; but the
latter produce only false carminated lakes, as their co-
louring part is easily altered by the combined action of
the air and the light. These colouring parts, however,
are still of some use when reserved for temporary ob-
jects, as printed calicoes, paper hangings, &c. ; but they
tnust be entirely banished from the pallet of the painter
who sets any value on the opinion of posterity. The
epithet of carminated, applied to the valuable lakes, is
Y 4<
S2S Treatise on varnishes.
derived from a series of operations on the compositîoîî
of carmine, which is prepared from cochineal.
ît is not so easy as some have imagined to distinguish
whether a hike has really been extracted from cochi-
neal, or from some vegetable colouring substance.
Means have been found, by certain re-agents and va- |
rious mixtures, to give such splendour to inferior lakes
that the most skilful painters are often embarrassed in
their choice. The dread of employing uncertain colours
renders them timid, and often makes them neglect co-
lours the duration of which they cannot foresee.
Among this number are lakes. The inefficacy of the
means said to be proper for determining their choice in
this respect, has served only to increase their uncer
tainty. If vinegar, we are told, be poured over lakes,
the colouring part of which has been derived from
Brasil wood or madder, &c. they will instantly turn
yellow. We shall soon see how little confidence ought
to be placed in processes the results of which require ^
more dme than an artist in full employment can devote
to them. I have, therefore, thought that this object
is of sufficient importance to deserve particular re-
searches : with this view I prepared some real as well
as false carminated lakes, that I might subject them to
the action of some re-agents, and for this reason I have
distinguished each preparation by a number, that they
may be more easily indicated in the annexed table,]
which exhibits the results of comparative experiments
ît will be found at the end of this article.
CARMINE. CARMINATED LAKE. S29
Carmine.
This kind of fecula, so fertile in gradations of tone
by the effect of mixtures, and so grateful to the eye in
all its shades ; so useful to the painter, and so agreeable
to the delicate beauty, is only the colouring part of a
kind of dïûed insect, known under the name of co-
chineal.
A mixture of 36 grains of chouan seed, 1 8 grains of
autour bark, and as much sulphate of alumine (alum),
thrown into a decoction of 6 gros of pulverized cochi-
neal and 5 pounds of water, gives at the end of froin
five to ten days, a red fecula, which when dried weighs
from 40 to 48 grams. This fecula is carmine. The
remaining decoction, which is still highly coloured, is
reseiTed for the preparation of carminated lakes.
CARMINATED LAKE.
No. L
The decoction which floats over the coloured preci-
pitate, known by the name of carmine, being still highly
coloured, the addition of sulphate of alumine, which is
afterwards decomposed by a solution of carbonate of
soda (salt of soda), disengages the alumine, and the
alumine in precipitating itself carries with it the colouring
part of the bath. According to the dose prescribed for
the composition two or three ounces of alum may be
employed. The greater or less quantity of this sub-
stance, the base of which seizes on the colouring fe-
cula, determines the greater or less intensity obsei"vei
in the colour of the lake resulting from it. When tlie
S50 TREATISE ON VARNISHES.
process is conducted on a small scale, and by way of
trial, the precipitate is received on a filter : it is then
washed with warm water ; and when it has acquired the
consistence of soft paste, it is formed into small cakes or
sticks. It is this substance which constitutes the beau-
tiful cai'minated lakes used for crayon painting.
In operating on a large scale, the whole of the alka-
line liquor judged necessary after a few trials to decom-
pose the quantity of alum intended to be employed, may :
be divided into three or four separate portions. As
many clotf^ filters as there are alkaline portions being
then prepared, the first portion of alkaline liquor is ^.
poured out, and the coloured precipitate resulting from
it is received on one of the filters : the coloured liquor
which passes through the filter receives thç second por-
tion of alkaline liquor, and the latter produces a se-
cond precipitate, which is received on a new filter. I'his
operation is then continued till the last portion of alka-
line liquor has been employed. The lakes deposited
on the filters are washed in warm water; and when they •
hâve drained, they are carried along with their cloth to
^ {he plaster driers, or to beds of new bricks. These
driers, which are made of wrought plaster, in the form
cf thick basons, or these bricks, attract the moisture
of the paste, and shorten the process. The first pre-
cipitation gives a carminated lake of a very high co-
ioui" ; the second is somewhat lighter ; and the rest go
en decreasing in the same manner. By thèse -means
the artist obtains from the same bath shades of colour
varied without end, much mellower, and more delicate "
than those resulting from a mechanical mixture of
CARMINATF.D LAKE. S3l
white clay in different doses, and lake saturated "with
'colour by one operation.
If the composer of crayons prefer in these opera-
tions to mix the bath of cochineal with white clay. Well
washed and of the first quality, he may obtain the same
shades by diluting with one measure of the decoction
of cochineal different quantities of clay. For example,
a pound of decoction saturated with colour, and a
quarter of a pound of clay ; the same quantity of decoc-
tion, and half a pound of clay ; a pound, and so on. This
operation, which is conducted in the same manner as
th?t ^OY Dutch pinks, is speedier than that performed by
a chemical decomposition with alum and an alkali. The
lakes obtained are exceedingly beautiful ; but unless
the clay be of the first quality they never have the
brightness, softness, and mellowness of the former ; as
the valine matters employed form a mordant which is
not furnished by the second method. In the latter, the
^vashings, which are indispensably necessary to carry off"
the salt resulting from the new combination, are sup-
pressed.
A beautiful tone of violet, red, and even of purple
red, may be communicated to the colouring part of
cochineal by adding to the coloured bath a solution of
■tin in nitro-muriatic acid (aquaregia). The effect will
be greater, if, instead of this solution, a solution of
oxygenated muriate of tin (fuming liquor of Libavius)
be employed.
The addition of arseniate of potash (neutral arsenical
salt) gave me shades which would be sought for in
vain with sulphate of alumine (alum).
S3a TREATISE ON VARNλHE5»
JÎnother method ofpreparhig çarminated lake, ly eX'*
ir acting the colouiijig part from scarlet clotL
Carminated lake may be composed also, without em-
ploying cochineal in a direct manner, by extracting the
colouring matter from any substance impregnated with
It, such as the shearings of scarlet cloth.
Put into a kettle one pound of fine wood-ashes with
forty pounds of water, and subject the water to ebulli.
tion for a quarter of an hour ; then filter the solution
^irough a piece of linen cloth till the liquor passes
through clear.
Put the liquor on the fire ; and having brought it to
a state of ebullition, add two pounds of the sheaiings^
or shreds of scarlet cloth dyed with cochineal, "which
must be boiled till they become white ; then filter the
liquor again, and press the shreds, to sqyeeze put all
the colouring part.
Put the filtered liquor into a clean kettle, and place
It over the fire. When it boils, pour in a solution
of ten or twelve ounces of alum in two pounds of
spring water which has been filtered. Stir the whole
with a wooden spatula till the froth that is formed be
dissipated ; and having mixed with it two pounds of
a strong decoction of Brasil wood, pour it upon a
filter. After filtration, wash the sediment with spring
water, and remove the cloth filter charged with it to
plaster driers, or to a bed of dry bricks. The resulf
df this operation will be a beautiful lake ; but it has
not the soft velvety appearance of that obtained by the
first method. Besides, the colouring part of the Brasil
ROUGE. S53
wood which unites to that of the cochineal in the shear-
ings or shreds of scarlet cloth, lessens in a relative pro-
portion the unalterabiiity of the colouring part of the
cochineal. For this reason purified potash ought to
be substituted for the wood ashes.
In this process the sulphate of alumine (alum) un-
dergoes decomposition by the presence of the alkaline
liquor or solution of wood ashes, which is a carbc»
nate of potash. The alumine, in precipitating itself,
seiies on the colouring fecula of the cochineal, which
rhe scarlet rags have abandoned to the alkali.
After the operation, the driers of plaster, or the
bricks, v/hich have extracted the moisture from the
precipitate, are e2;:posed to the sun, that they may be
f.tted for another operation.
This method is more complex than the preceding.
Besides, it is not ceconomical for colour-makers who
may be at a distance, from cloth-dressers. The shear-
ings of cloth are in great request among the manufac-
turers of paper-hangings, which renders the price of
ihem too high to admit of their being employed in the
reparation of carminated lakes. This, therefore, h
he only process I never repeated.
Rouge.
Carmine united to talc, in different proportions, forms
rouge employed for the toilette. Talc is distinguished-,
^also by the name of Briancon chalk. It is a substance
composed, in a great measure, of clay combined natu-
pUy with silex.
Carmine, as well as carininat':^d lakes, that is to say^
33"* TREATISE ON VARNISHES.
those the colouring part of which is borrowed from
cochineal, are the most esteemed of all the composi-
tions of this kind, because their colouring part main-
tains itself without degradation. There are even cases
where the addition of caustic ammonia, which alters
so many colouring matters, is employed to heighten its
colour. It is for this purpose that those who colour ^
prints employ it. |
FALSE CARMINATED LAKES, IN WHICH THE CO-
LOURING PART IS DIFFERENT FROIVI THAT
OF COCHINEAL.
Carminated fake extracted from madder.
No. 11.
Notwitlistanding the unfavourable opinion entertained
in regard to lakes extracted from vegetable substances,
C. Merlnet, an ingenious painter, found in the root of
madder a colouring substance to which the addition of
sulphate of alumine (alum) gives a veiy warm tone of
purple red, exceedingly bright, and of such durability
as places this lake far above that obtained from a de-
coction of Brasil wood. Such, at least, is the account
Ï have seen of it*.
«
ioc
fi
ill
* Certain saline substances^ which chemists and the inanufacturers
of colours employ as re-ageuts and mordants, have a very striking
influence on several vegetable colouring matters, which tliey mo-
dify in a particular manner that depends on their state of composi-
tion. Though experience seems to have limited the number of
these re-agents, there is reason to presume that new researches in
If gard to the numerous saline combinations known in chemistry.
i^k
CARMINATED LAKE FROM MADDER. 3S.>
,, The following process, which I employed to make
lake of madder, was attended with complete success.
Experience will soon show what are the proper doses of
the principal substance and of the re-agents. Boil one
part of madder in from twelve to fifteen parts or pounds
of water, and continue the ebullition till it be reduced
to about two pounds. Then strain the decoction through
a piece of strong linen cloth, which must be well
squeezed ; and add to the decoction four ounces of
alum. The tint is then a beautiful bright red, whicti
the matter will retain if it be mixed with proper clay.
In this case, expose the thick liquid which is thus pro-
duced on a linen filter, and subject it to one washing
and those especially, the base of which is metallic, would still pro-
cure new resoui'ces to the art of colour-making, cotton-printing,
dyeing, &c.
The animal organization, aiid the motion which constitutes life,
give, under certain circumstances, results similar to those obsers'ed
in certain vegetable or animal colouring matters subjected to the
influence of chemical agents. The colouring part of the cactus
opuntia, on which the cochineal is produced, and on which it feeds,
receives, according to every probability, from tlie insect all those
qualities v/hich raise it so far above all tlie colouring feeulse of the
ame tone. The case is certainly tlie same with that of madder,
rt'hich escapes the operation of digestion when the root is mixed
A'ith the food, and which gives to bones as bright a tint as it pro-
luces when treated with alum. There is equal reason to presume
hat the solid colouring matter which fills the alreoli of gum lac,
Ind which the Indians take great care to separate before they sell
Iiat resin, is an extract of the substance used as nouri^ihment by
he kind of ant which deposits it on the branches of the jujube. All
hese particular colouring matters receive, no doubt, from the ani-
Dal humours that solidity of tint which is peculiar to them.
536 •treatise on var^jishes,
to remove the alum. The lake, when taken from the
driers, will retain this bright primitive colour given by
the alum.
But if in the process for making this lake decomposi-
tion be employed, by mixing v/ith the bath an alkaline
liquor, the alum which is decomposed deprives the
fcath of its mordant, and the lake obtained after the
subsequent washings appears of the colour of the
madder bath viithout any addition : it is of a reddish
brown. In this second operation seven or eight ounces
of alum ought to be employed for each pound of
madde».
This kind of lake, obtained by decomposition, is
exceedingly fine ; but it does not possess that bright
red colour so much sought after : it may, however, be
communicated to it, if the washed precipitate be mixed ■
before it be dry with alum water.
If the aluminated madder bath be sharpened with ace-
tîte of lead (sal saturni), or with arseniate of potash
(neutral arsenical salt), you will obtain, by the addition
of carbonate of soda, a rose-coloured lake of greater
or less strength. It is that marked No. 3. in the com-,
parative table.
Lake from BrasU wood.
No. IV.
Brasil wood affords, for the preparation of those
lakes called carminated lakes, two different and very
rich colours, if the process which facilitates the remo-
val of its colouring part to the alumine disengaged
LAÎCE FROM BRASIL WOOD. ■ 3Ô7
from the alum, or to proper clay, be varied. These two
shades are obtained by employing chemical decompo-
sition, or by plain mixture without decomposition. The
two processes I used are as follow :
I boiled four ounces of the raspings of Brasil wood in
fifteen pounds of pure water, till the liquor was re-
duced to a pound and half or two pounds. The liquor
had then a dark red colour, inclining to violet ; but the
addition of four or five ounces of alum gave it a bright
red, inclining to rose-colour. When the liquor has
been strained through a piece of linen cloth, if four
ounces of the carbonate of soda (alkali of soda) be
added with caution, on account of the effervescence
which takes place, the colour, which by this addition is
deprived of its mordant, will resume its former tint, and
deposit a lake, which when washed and properly dried
has an exceedingly rich and mellow violet-red colour.
If only one half of the dose of mineral alkali be em-
ployed for this precipitation, the tint of the lake be-
comes clearer ; because the bath still retains the unde-
composed aluminous mordant.
In the last place, if the method employed for Î3utch
pinks be followed, by mixing the aluminous decoction
of Brasil wood with pure clay, such as Spanish white
and white of Morat, and if the mixture be deposited
on a filter to receive the necessary washing, you will
obtain from the driers a lake of a very bright dark
ïose-colour. The lake which I prepared in this man-
ner, making use of pure clay from Morat, is marked
No. 5. in the comparative table.
The first lake is harder than the second, because not^
z
33S TP.ËATISE ON VARNISHES*
withstanding the washing it retains salts which adhere
strongly to the clay ; but the second is too soft. Its
colour, heightened by the mixture of alum, seems to
have a superiority over the aluininous lake of madder,
which brings it near to the lakes made from cochineal ;
since, according to experiments of which I shall here,
give a short viev/, it opposes nearly the same resistance
to the effect of certain re-agents.
By the same processes a very beautiful lalte may be
extracted from a decoction of logv/ood. In general,
lakes of all colours, and of ail the shades of these co-
lours, may be extracted from substances whicli give up
their colouring part to boiling water ; because it is
;ifterwards communicated by decomposition to the alu-
mine precipitated from sulphate of alumine, by means
of an alkali ; or the tincture may be mixed with a pure
and exceedingly white argillaceous substance, such as
real Spanish white, or white of Morat. It is the pro-
perty of alumine, and of all clays, to form a kind of
combination with the divided oily or resinous substances:
with which they are in contact, and to retain them r
this property constitutes them stones or earths. Some
of them, under the name of fuller's earth, are employed
for scouring cloth.
When lakes are prepared by the medium of alum, |'
which is decomposed by the application of an alkaline
liquor, carbonate of soda (salt of soda) is to be pre-^
ferred to carbonate of .potash (alkali of potash), because
the new salt, which results from the decomposition of:
the sulphate of alumine by means of the former, is-
far more soluble tlian that which might be formed by-
LAKE FROM BRASIL WOOD, S39
potash. The washing of the lake then succeeds better,
and no foreign salt remains to make it hard, and some-
times efflorescent. Besides, this labour for the greater
exactness would require the us.e of pure carbonate of
potash, and it is easier to answer this condition with
soda than with potash, though soda is never pure.
Lakes enter into the composition of solid colours.
They may be employed to colour changing alcoholic
varnishes ; but in this particular case it would be sim-
pler to extract the tincture from cochineal itself, since
nothing is required but the colouring part.
I have already mentioned, that it has been commonly
believed that real carminated lakes, the colouring part
of which is obtained from cochineal, C3n easily be di-
stinguished, by means of vegetable acids, from those in
which the colouring part is a vegetable product. The
latter, as asserted, do not stand the test of immersion
in these acids without becoming yellow. The trials
which have been made do not seem to correspond to
the confidence placed by some in this kind of process,
since artists are still afraid to employ lakes in the
composition of works which they are desirous should
be handed do\Ta to posterity. It is rather the latter
consideration, than the fear of a pecuniary sacrifice
for an article of inferior value, that ought to excite- a
wish that means of avoiding this fraud mJght be disco-
vered. Both these motives, however, induced m.e to
make researches on this subject, by exposing to the
efforts of different re-agents the five kinds of lake, the
composition of which has been here so minutely de-
t^led, that the processes may be applied to eveiy sub-
z2
MO' TREATISE ON VARNlSHÊà^
Stance the colouring part of which is soluble in tv^ater.
'Ï shall here exhibit a comparative table of, the effects
resulting from the different processes employed. The
experiments were made in large watch glasses exposed
to the open air ; and as the impression of the light has
a more sensible influence on soma colouring parts than
on others, I thought it my duty to subject the mixtures
toit.
Re-agents act in a different manner on the same sub-
stance. Some, to produce their effect, require only a.
momentary contact ; while others require more timcy
and do not manifes? their influence till they have pro-
duced a kind of solution. This circumstance, which
I could not properly observe in simple mixtures exposed
• to evaporation favoured by the sun, induced me to
vary the experiments : I put the same mixtures into
bottles closely shut, and kept an account of the results
observed at the moment of contact, twenty-four hours
after, and at the end of three weeks. They are exhi-
bited, such as I observed them, in the annexed table.
This short view of these results will, no doubt, be
sufficient to establish the essential difterences between
the various colouring parts applied to the composition
of carminated lakes or crayons ; and to prove the in-
sufficiency of the means hitherto considered as the most
certain, for distinguishing real carminated lakes from
those which are only an imperfect imitation of them.
Lemon juice, or any other vegetable acid, and in parti-
cular vinegar, to which was ascribed, but without any
reason, the property of changing to yellow the bright
or purple red given to these counterfeited lakes, and
Comparative Table of ti^
Re-agenTs.
Caustic ammonia.
Acetous acid, or
strong distilled
vinegar.
Diluted sulphuric
acid.
Muriatic acid.
Carbonate of
potash.
No. 1. ,^ -:
Lake from cochineal tii ^14in
alum and the alkali orab-,;
At the time
of viixture.
Brightened
Not dissolved
The same tint
Not dissolved
Bright red.
Dissolved,
Dark rose co-
lour. Dis-
solved.
Dark violet
colour. Not
dissolved.
Twenty -four '"«^ ^^^^s
hoiLrs after, ojtcr.
va. colour,
The same, jiroyed.
dissolved
eddish
Purple. 3wn. In
dissolved.
eddish
The same. '^^"- ^"
dissolved.
Rose.
ilnut-tree
lour. In
dissolved
îstroyed.
Purplish red.t dissolved
Re-agents.
Caustic ammonia.
Acetous acid, or
strong vinegar.
Diluted sulphur-
Comparative ?"•
No. 1.
Dry lake. Colour pre.s^i^h some
and a little less bright abo\
Dry) and of a rose color. ^^ brown
Aluminous crystals of a^ °* thick
lour. The lake was cryst;
ous acid.
Muriatic acid.
N. B. Carbonate of potash was nc t emp
A kind of transparent s:"" ^^^ ^o-
beautiful purple colc'ur.
1
To front page 340:
1
Comparative Table of the results of the mixture of some re-agents with different carminated lakes, observed at different periods in close vessels
Re-agents.
Caustic ammonia.
Acetous acid, or
strong distilled
vinegar.
Diluted sulphuric
acid.
Muriatic acid.
Carbonate of
potash.
Re-agents.
Caustic ammonia.
Acetous acid, or
strong vinegar.
Diluted sulphur-
ous acid.
Muriatic acid.
No. 1.
Lake from coch ineal treated with
alum and the alkali of soda.
Jt the time Twenty-fnur Three weeki
of mixture, hours after. after.
Brightened.
Not dissolve!
The same tint.
Not dissolved
Bright red.
Dissolved.
Dark rose co-
lour. Dis-
solved.
Dark violet
colour. Not
dissolved.
Purple.
Purplish red.
Beautiful red.
Dissolved.
Pale red. In a
kind of jelly.
Piu'ple red.
Red of wine
lees. Altered,
No. 2.
Lake from madder with alum de
composed by soda.
yit the time Twenty-four Three weeks
of mixture, hours after. after.
Blood red In B,igh,er red.
tdissolved. ^
Chesnut. In
partdissolved
Dark cinna-
mon colour.
In part dis-
solved.
Brick colour
inclining to
brown. In part
dissolved.
Dark reddish Brick red co-
brown. Inpartj lour, or light
dissolved. brown.
A little alter-
ed. In part
dissolved.
Dark cinna-
mon colour.
In part dis-
solved.
Dark walnut
tree colour. In
partdissolved
Dark walnut
tree colour. In
partdissolved
The same. In
partdissolved
No. 3.
Lake from madder with arseniate
of potash and salt of lead.
Jt the time Twenty-four Three weeks
of mijiture. liours after. after.
Brickred.Not
dissolved.
Brick red.
Dissolved in
part.
Yellowish
brown. Not
dissolved.
Dark orange
In part dis-
solved.
Brick red, as
by ammonia.
Light yellow
Red chefîmU
colour. Not
dissolved.
Altered. Not
dissolved
Pale red. Dis-
solved in a
great part.
Green colour,
&: destroyed.
Not dissolved
Brown. In
partdissolved
The same.
Dissolved.
No. 4.
Lake from Brasil wood with alum
decomposed by soda.
At the time Twenty-four Three weeks
of mixture, hours after. after.
Violet purple
Not dissolved
Dark red. Dis-
solved in part,
Bright scarlet
Not dissolved
Red inclining
topurple. Not
dissolved
Reddish
brown. Not
dissolved
Coffee brown.
In part dis-
solved.
The;
Bright rose
colour.
Reddish
brown.
Dark violet
red.
Darker. In
partdissolved,
Purple red. In
partdissolved
Bright rose
colour. Dis-
solved.
Dark brown
In part dis-
solved.
Dark reddish
brown. Not
dissolved.
No. 5.
Red from Brasil wood and dlôm
mixed with earth of Morat.-,;_
M the time Twenty-foh
of mixture, hours after
Violet purple
Not dissolve
Violet inclin- Green colour,
to brown, desiroyed.
Not dissolved
Purple red.
Not dissolved
Scarlet red, a
litUe du
Dissolved in
part.
Red inclii
to rose colour
Not dissolv
Dark violet.
Not dissolved,
Three weeks
after.
Poppy colour.
Purple.
Rose inclin-
ing to poppy
Common
violet.
Reddish
brovvir. In
partdissolved
Reddish
brown. In
partdissolved
Walnut-troe
colour. In
partdissolved
Destroyed,
Not dissolved
Comuaralive results of the mixture of the same re-agents with the same takes e.rposed to the air and the sun, observed at the end of a month.
No. 1.
Dry lake. Colour preserved below^
and a little less bright above.
Dry) and of a rose colour.
Aluminous crystals of a pale rose co-
lour. Tlie lake wa.s cr) stallizcd.
A kind of ti'anspnrent saline jelly ofa
beautiful purple coU jur.
No. 2.
Dry. Brick colour below, and a little
pale above.
Dry. Of a reddish brown colour.
Kind of soup ofa light rust colour.
Kind of jelly of a capuchin colour.
No. 3.
Dry lake of a dark brick red colour, a
little pale at tlie surface.
Dry. Of a pale brick colour.
Dry lake, and of a brown colour.
Pulverulent lake of a dark mordoré
colour.
No. 4.
Dry lake, witli a surface like talc : a
little pale above; colour preserved below.
Dry. Purple red colour.
Thick soup of a bright brick red co-
lour.
Dry lake of a flesh colour.
No.
Dry lake colour prescr\ed, with some
white specks iibove.
Dry. Purple colour inclining to brown
Dark red, of tlie consistence of thick
soup.
Kind of thick soup of a dark red co-
lour.
N. B. Carbonate of potash was nc t emplri\e(l in these first experiments.
J
LAKE FROM BRASIL WOOD. S4l
even the mineral acids which I employed, exhibit cha-
racters entirely opposite in these colouring parts, which
are foreign to that of cochineal. We every where see
that the development of the red colour, under diffe-
rent tones of shade, is the certain result of the first
contact, except in madder red, which acids speedily
destroy. They change this colour to that of rust, more
or less dark, according to the time it has been exposed
to the acid and to the influence of the light.
These results, when compared, seem to confirm the
great similarity between the colouring part extracted
irom Brasil wood and that of cochineal; since acids
contribute to their development in the same tone of co-
lour, though \îàth modifications which may readily be
observed. Were one contented, therefore, with the
first view in this respect, the progress of our re-agents
would appear to be pretty uniform ; but it would not
be sufficient to establish the necessary distinction be-
tween lakes extracted from cochineal and those made
with Brasil wood ; since with one re-agent, such as
sulphuric acid, they exhibit chemical properties which
seem to confound them when the effects of the first
contact only are considered. This kind of resemblance,
however, is limited : it soon becomes weakened by
time and the impression of the light ; and it is then
easy to distinguish them by the subsequent results, on
leaving an interval of three or four days to facilitate
and complete the action of the re-agents.
Every one of these substances here mentioned be-
comes then, in the hand of an intelligent painter or
-amateur, the certain means of enabling him to ascer-
Z3
342 Treatise on varnishes.
tain the nature of lakes. The effects arising from the
application of acids are not sufficiently distinct at the
moment of their mixture, though they present shades
which do not escape the notice of an expert eye ; but
an interval of forty-eight hours will be sufficient to ren-
der their difference very sensible to persons in the least
accustomed to the effect of such mixtures. "The sul-
phuric acid employed in the trials to which I here al-
lude, resulted from a mixture of the sulphuric acid of
the shops (oil of vitriol) and water, in the proportion
of one to four. The muriatic acid was applied in the
state in which it is sold.
If the results be accurately compared, it will be ob-
served that they vary in the mixtures according as they
are exposed in open vessels, or in vessels closely shut.
In the first case, the evaporation of the liquid may
serve to account for the Httle influence of the re-agent.
Caustic ammonia on such occasions produces no effect,
in consequence of its great volatility. The muriatic
acid participates in the same inconvenience. Besides,
the mixture of light bodies transported by the air, or
detached from the ceiling of the apartment, may mo-
dify the results. A view of the two comparative tables
Vv'ill be sufficient to give v/eight to the present observ^a-?
tion, and to determune in regard to the preference which
ought to be given in the employment of these mixtures
to vessels v/hich can be closed with cork stoppers. The
effects may then be observed with more certainty, and
to a greater extent.
Some of the re-agents seize on the base of the lake,
and dissolve it. This effect may furnish a new subject
OXIDES OF LEAD. " S43
-of observation, when it is required to discover the n-d"
ture of that base which may be composed of alumine,
resulting from the decomposition of the sulphate of alu-
mine (alum), or pure clay; or, in the last place, of
chalk. This solution, then, is better perceived in ves-
sels which oppose the evaporation of the liquid than in
those which afford a free access to the exterior air. I
have exhibited these particular cases in. the comparisons
which constitute the first comparative table by the ex-
pressions dissolved, dissolved in part, or not dissolved.
In all cases the influence of the light is not to be over-
looked.
These observations conclude my researches in regard
to real or false carminated lakes. They may, perhaps,
appear prolix to those who in works of this kind look
only for the formulae of compositions ; but it ought al-
ways to be remembered that I v/rite for the information
of the amateur as well as of the artist.
OXIDES OF LEAD.
GRAY OXIDE OF LEAD. GRAY CALX OF LEAD,
First degree of oxidation.
The oxides of lead obtained by the means of caloiic
(fire) exhibit themselves in the arts under various cha-
racters of difference, which may serve to denote v\ ith
considerable accuracy the gradation they experience in
the process of oxidation, under the continued action of
a pretty high temperature. The same gradation ought
to be followed in the order of their descripdon.
344
TREATISE ON VARNISHES,
When lead is exposed to heat, it readily enters into
fusion. Its surface then becomes covered with a pelli-
cle of a gray, and as it were an earthy colour : this is
the first step towards oxidation (calcination). If this
pellicle be removed, it is immediately succeeded by an-
other ; and so on till the whole mass is, at length, re-
duced to the form of a gray powder. This is gray
oxide of lead.
MASSICOT. YELLOW OXIDE OF LEAD.
Second degree of oxidation. *
After the first operation of the temperature is in-
creased, the gray oxide assumes a yellow colour ; ançi
when this colour is sufficiently developed it is distin-
guished by the name of massicot, or more correctly of
yellow oxide of lead.
I
MINIUM. RED OXIDE OF LEAD.
Third degree of oxidation.
If a greater division in the parts of the yellow oxide
of lead be facilitated, which may be done by stirring
the matter, and exposing the surfaces to the renewed
contact of a reverberated flame, it assumes a red colour,
more or less intense, and constitutes what is called red
oxide of lead, or minium. A part of this oxide is al-
ready very near to reduction ; and when treated over
the fire without any medium, in a very close crucible^
gives a little reduced lead.
OXIDES OF LEAD. S^-^
Ï.ITHARGE OF GOLD OR OF" SILVER. VITREOUS OXIDE
OF LEAD,
Foiu'th degree of oxidation.
In the last place, if massicot or minium be exposed
to an accumulation of caloric, the oxide becomes in.
part vitrified, and forms vitreous oxide of lead, knowji
under the name of litharge.
All these transitions take place accidentally in the
process of cupelling, on a large scale, the principal
object of which is to oxidate all the lead, in order to
extract the silver it contains. The bellows, the wind
of which forces the flame to reverberate on the matter
in fusion, becomes the cause of the fusion and oxida-
tion, which are the consequences of it. Yellow oxide
of lead is soon formed : the current of air, which ac-
celerates oxidation, next produces red oxide ; and the
latter, being in part volatilized, lines the apertures of the
furnace. Vitreous oxide of lead then soon makes its
appearance, under the form of scum driven forward by
the current of air, which the bellow^s maintain on the
matter. This vitreous oxide is collected through an
aperture made for extracting it, and through which it
is made to run under the form of stalactites.
The colour of this oxide varies. When red, it is
known in commerce by the name of litharge of gold :
when in this state it has suffered least from the fire.
Oxide of a greenish-yellow colour is called improperly
Jitharge of silver : it is in a state nearer to vitrification
than the former. The colour, therefore, of the vitre-
SéS Treatise on varnishes.
ous oxide depends on the action of the caloric, which
may be stronger or weaker in the course of the ope-
ration.
Gray oxide of lead is not used in painting : it is em-
ployed only for varnishing earthen ware and common
pottery.
Yellow oxide, or massicot, was employed in paint-
ing before painters were acquainted with Naples yellow
and that of Montpellier, which have been substituted in
its stead.
The use of red oxide, or minium, is more extensive.
It is employed in house-painting, coach-painting, &c,
to compose beautiful reds, and to serve as a ground to
vermilion, which is applied to the painting of decora^
tions which require durabilit)^
Vitreous oxide of lead (litharge) is of no other use
in paii.ting than to free oils from their greasy particles,
for the purpose of communicating to them a drying
quality. Red litharge, however, ought to be preferred
to the greenish-yellow : it is not so hard, and answers
better for the purpose to which it is destined.
When painters wdsh to obtain a common colour of
the ochrcy kind, and have no boiled oil by them, they
may paint with linseed oil, not freed from its greasy
particles, by mixing with the colour about two or three
parts of litharge, ground on a piece of porphyry with
water, dried and reduced to fine powder, for sixteen
parts of oil. The colour has a great deal of body, and
dries as speedily as if di7ing oil had been used.
DIFFEÏ^ENT KINDS OF BLACK. 34*7
Jjamp hlach. Fat soot resulting from the decomposU
tion of resins and oils bijfire.
Lamp black, as already seen in the first part of this»
work, is produced from the thick smoke exhaled by
fat resinous bodies in a state of combustion. It is grease
mixed with undecomposed resin, and is attended with,
the inconvenience of becoming red. It is not, there-
fore, employed in delicate colours. It is destined for
the oil colours applied to railing, balustrades, &c.
It might be employed, however, in the more deli-
cate kinds of painting, if washed to separate from it
the foreign niatters, and then reduced to the state of
pure charcoal. The last quality may be communicated
to it by exposing it in a close crucible to a heat capable
of decomposing entirely the resinous or oily parts,
which still remain united to the charred part. In this
case it emits a thick smoke, which is suffered to escape
through a small aperture in the cover.
It might appear, on the first view, that the same
biack substance might answer in all cases which require
jthe use of this colour, Vv'hether destined for an uniform
ground, or intended by its mixture with other colour-
ing parts to form various shades. Long experience,
Jiowever, has established other principles. It is known
that a black substance, which produces an admirable
effect in a fine composition, woiild produce an inferior
effect in a composition of another kind. Hence the di-
stinction established between several black colouring
substances which borrow their name from the producing
substance j as smoke black, black from beech wood.
S^S TREATISE ON VARNISHES»
black of peach stones, ivory black, or black froj^ri
caiciiied bones. ,^
Particular hind of lamp hlach.
I have long «nployed a beautiful black, which may
be easily procured. Nothing is necessary, for this
purpose, but to suspend over a lamp a funnel of tin-
plate, having above it a pipe to convey from the apart-
ment the smoke which escapes from the lamp. Large
mushrooms of a veiy black carbonaceous matter, and
exceedingly light, will be formed at the summit of the
cone. This carbonaceous part is carried to such a
state of division as cannot be given to any other matter
by grinding it on a piece of porphvry. This black
goes a great way in every kind of painting. It may
be rendered drier by calcination in close vessels.
I must here observe that the funnel ought to be
lUiited to the pipe, which conveys off the smoke, by
means of wire, because solder would be melted by
the flanie of the lamp.
Beech black. Beech charcoal.
Beech, like every other kind of wood, furnishes
by combustion a charcoal, which, when well ground
on porphyry and mixed with white oxide of lead,
gives a blueish gray colour. When applied in dis-
temper or in oil painting it will be proper to reduce
it to an impalpable powder, free from those small
brilliant facets observ^ed in charcoal badly ground.
This may be easily accomplished by grinding it with
water, and rc-grinding it after the desiccation of th^ j
blfFERENT KINDS 01" BLACK. Zi3
{)aste. This black, if the paste, after its extreme di-
vision, be besprinkled on a filter with warm water, to
carry off the saline parts adhering to it, will be iess
. apt to effloresce.
Black from, ivine lees.
This black results from the calcina:tion of wine îees
and tartar ; and is manufactured on a large scale iii
some districts of Germany, in the environs of Mentz^
\ and even in Fran(îe. This operation is perforaied in
large cylindric vessels, or in pots, having an aperture
in the cover to afford a passage to the smoke, and to
the acid and alkaline vapours which escape during the
process. When no more smoke is observed the ope-
ration is finished. The remaining matter, which is
merely a mixture of srJts and a carbonaceous part very
.much attenuated, is then washed several times in boil^
îng water; and it is reduced to the proper degree of
fineness by grinding it on porphyry.
If this black be extracted from dry lees, it is coarser
than that obtained from tartar ; because the lees con-
tain earthy matters which are confounded with the
carbonaceous part.
This black goes a great way, and has a velvety ap-
pearance. It is used chiefly by copper-plate printers. -
Black from hurnt peach stones.
Peach stones, burnt in a close vessel, produce a
charcoal, which, when ground on porphyry, is em-s
jployed in painting to give an old gray.
TREATISE ON VARNISHESi
Black from burnt vine twigs.
Vine twigs reduced to charcoal give a blueish blacky
which goes a great way. AVhen mixed with white it
produces a silver white, w^hich is not produced by
ether blacks : it has a pretty near resemblance to the
black of peach stones; but to bring this colour to
the utmost degree of perfection, it must be carefully
ground on porphyry.
Ivory I'lacL Bone black.
Put into a crucible, sun'ounded by biinutig coals,
fragments or turnings of ivory, or of the osteous parts
of animals, and cover it closely. The ivory or bones
by exposure to the heat will be reduced to charcoal.
When no more smoke is seen to pass through thé
joining of the cover, leave the crucible over the fire,
for half an hour longer, or until it has completely
cooled. There will then be found in it a hard carbo-
naceous matter, which, when pounded and ground
on porphyry with water, is washed on a filter with
w2.riTL water, and then dried. Before it is used it must
be again subjected to the muller.
Black furnished by bones is reddish. That pro»
duced by ivory is more beautiful. It is , brighter than
black obtained from peach stones. When mixed in a
proper dose wdth white oxide of lead, it forms a beauti-
ful pearl gray. Ivor}'' black is richer. The Cologh«
and Cassel black are formed from ivory,
f,
ibiFEERENT KINDS OF OCHRE/ S5ï
OF OCHRES.
Of all the metals, iron is that which opposes the least
resistance to the chemical action resulting from its
contact with different substances, while exposed to the
influence of humidity and of the air. Earths, salts,
acids, sulphur, arsenic, and even water, become, under
certain circumstances, the origin of modifications which
transfer it from the order of simple bodies to that of
compound substances. Volcanic fires and caloric, dis-
engaged by the effect of subterranean com.binations,
of which itself appears to be one of the chief prin-
Tciples, act upon it in a manner more or less energetic,
and communicate to it relative forms and properties.
Brown, yellow, and red ochres evidently exhibit
the effects of a sort of combustion, or rather oxida-
tion, more or less extensive and more or less accele-
rated. Water seems to be the principal promoter of
this oxidation; but the latter finds there also the agent
of its decomposition. The hydrogen, which is one of
its constituent principles, escapes under the form of
inflammable gas ; while the oxygen, another principle
of water, unites to the metal, and converts into an
oxide.
This oxide is more or less charged with oxygen,
and more or less mixed with argillaceous earth and
carbonate of lime (calcareous earth).
Brown odhre, *
When the oxidation of the iron is not very exten»*
sive, the result is a brown ochre. Carbonic acid oftejff
forms a Dart of it,-
ÉS2 Treatise on varnïshesô
Ochre de rue.
A degree more in the progress of the natural oxi-
dation of iron, that is to say, a quantity of oxygen
somewhat greater than in brown ochre, and a mixture
cf clay, give ochre of a dark yellow colour. This
mass constitutes ochre de rue, which is extracted by
washing it in a large quantity of water.
Calcined ochre de rue.
This ochre de rue subjected to the action of accu-
mulated caloric (a very active fire) acquires a yellow
colour, more or less developed according to the degree
of oxidation acquired by the influence of the process.
Natural yellow ochres.
In many cases nature frees the artist from the trouble
of this artificial oxidation. It prepares ochres on a
ïarge scale, and very much varied in their colour.
They are produced in the ci-devant Auvergne, and in
all countries in the neighbourhood of volcanoes, and
form articles of commerce under the names of dark
yellow ochre and bright yellow ochre. These ochres
are more or less argillaceous ; they are often marly,
that is to say, mixed with clay, carbonate of lime
(calcareous earth), and coloured by iron. They are ■
separated from the sand and stones they may contaia,
by careful washing.
Red ochre.
When this oxidation is effected in the neighbour-
hood of volcanic fires, or by the effect of subterranean
DIFFERENT KINDS OF OCKRES. 3S3
Combinations of great extent, or under the influence
of chemical processes, as in the operation for making
artificial sulphates of iron (martial vitriol), in which a
great deal of caloric is developed, the colour assumed
by the oxide of iron is more exalted. It is a red more
or less bright. This red ochre, or red oxide of iron,
mixed in various proportions with clay or marl, if a
natural production, will be pure red oxide of iron j
and if a production of art will be English red.
Natural red ochre is very abundant in volcanic
countries, as is the case in Auvergne ; the different
departments of which produce very beautiful kinds.
Clay forms the greater part of it ; and it is this sub-
stance which renders it so soft to the touch.
The method of purifying ochres is simple. Though
drier than pure clays, they are lighter than sand, and
the fragments of stones which may be mixed v/ith
them. They dilute readily in water, and during this
washing suffer to be precipitated those bodies which
are heavier than themselves. The water charged with
them is decanted, by making it pass into a trough
lower than the vessel in v/hich they were washed; and
tvhen the sediment is formed, the clear v/ater is drav/n
off. The coloured paste is then taken out, and being
dried is divided into small masses.
When an ochre is composed of oxide of iron and
clay, it resists the action of acids» If an effervescence
is produced, the composition is of a marly nature. Car-
<bonate of lime (calcareous earth) is found in these
Gchres in different proportions. In this case the ochre
2a
S54 ' TREATISE ON VARNISHES.
is drier. It exhibits less body than an ochre en-
tirely argillaceous, when employed in oil or varnish
pa^nting.
It is seen by this short view of these ochres that
iron, by its different degrees of oxidation, natural or
artificial, becomes the base of several kinds of colour;
and that it renders a very extensive service to painting.
In this respect no metallic substance is equal to it.
English-red. Reddish brown and dark red oxide of
iron without mixture.
Art, which operates in a direct manner on iron,
and which cannot admit in its processes the slow pro-
gress of nature, communicates to it only red tints,
more or less obscure, and more or less approaching to
a beautiful red. Ochres are earthy oxides of iron :
those made by art are pure oxides. Under the latter
state they have often need of being mixed with other
substances capable of modifying the hardness which
these pure oxides would give to the tint, and of ren-
dering" them more atrreeable to the eye.
I shall class among this last kind of oxides of iron
the reddish brown, the dark red of England, and even
the Prussian red, which results from the decompo-
sition of the sulphates of iron (martial vitriol), or which
are extracted from the residua of the operation by
which nitrate of potash (nitre) is decomposed to con--^
vert it into nitrous acid (aquafortis). These residua
are darker in colour, according as the temperature has
been higher during the time of the operarion.
^ ENGLISH RED, 355
These residua are pulverized and washed, to carry-
off the saline parts which are mixed with them. The
paste is then, carefully ground, and afterwards washed.
When a sufficient interval has been left to give the
coarser parts time to be precipitated, the water, which
is charged v/ith the most attenuated parts, is decanted.
A sediment is then formed by rest, which after desic-
cation acquires a beautiful bright red colour.
The sediment deposited, during the first interval,
gives an obscure red ; but if the artist is desirous to
lessen the quantity, in order to increase that of the
bright red, it is dried, calcined a second time, and
then ground. The washing is then repeated as before ;
and the result is a new dose of bright red and of
obscure red. These different reds, prepared in this man-
ner, are much sought after by porcelain painters, &c.
But when destined for house-painting, &c. the same
care is not necessary. The oxidation of the sulphates
of iron is effected on a very large scale, and the colours
produced are the common reds applied to the painting
of various articles.
The English, who have extensive vitriol manufac-
tories, in which they employ various processes, use
for pulverizing red oxide of iron the same mechanism
.9S for the glazing of gunpowder. It consists of a
barrel suspended on two axles, and moved by a handle
^r by water. The dried masses of colcothar or washed
ied are put into this barrel, together with several bul-
lets. By turning the barrel the bullets are made to
revolve, and in a little time the dry matter is reduced
to the state of powder.
2a 2 I
^59 TREATISE ON VARNISHES.
The method mentioned under the article indigo
may also be employed. In this case the pulverization
is effected in the bason.
Prussian red.
■ The Prussians prepare, on a pretty extensive scale,
and by means of an open fire, a kind of colcothar (red
oxide of iron) which is calcined several times, and the
washing of which is conducted in such a manner as to
extract, by one operation, several sediments, differing
in beauty according to the time employed in the pre-
cipitation. The first sediment formed in a determinate
time is coarser than the second, and so on in succes-
sion. It results from this division of the time neces-
sary for the total precipitation of the suspended parts,
that the last sediment exhibits parts more attenuated .-
The red colour which thence results is indeed suffi-
ciently dehcate to be admitted to a place on the palette
of the painter.
Litmus,
The Canary and Cape de Verd islands produce a
■kind of lichen or moss which yields a violet colouring
part, when exposed to the contiict of ammonia dis»
engaged from urme, in a state of puti'efaction, by a
mixture of lime. When the usual processes are finished
it is known by the name of litmus.
This aiticle is prepared, .on a large scale, at Lon-
•don, Paris, and Lyons. In the last-mentioned city j|f
another kind of lichen, which grows on the rocks like
mossj is employed. This lichen is very abundant itt
4
ORPIMENT. YELLOW OXIDE OF ARSENIC. 35?
the ci-devant Auvergne. The litmus resulting from it is
inferior to that of the Canaries.
The ammonia (volatile alkali) disengaged by means
of hme from urine in a state, of putrefaction, joins the
resinous part of the plant, develops its colouring part,
and combines with it. In this state the lichen forms a
paste of a violet-red colour, interspersed with whitish
spots, which give it a marbled appearance.
Litmus is employed in dyeing, to communicate a vio-
let, colour to silk and woollen. It is used also for co-
louring the liquor of thermometers. The varnisher
composes with it his violet and HIac varnishes j but the
colour is not durable.
Orpiment. Yellow sulphurated oxide of arsenic.
. Orpiment is the result of the combination of nine
parts of arsenic and one of sulphur; and hence the
name given to it in the New Nomenclature : Yelloiu
sulphurated oxide of arsenic.
Two kinds of it are known in commerce : one com-
posed of large brilliant laminas of a beautiful yellow co-
lour ; the other in small facets, the yellow colour of
■which has a greenish tint.
Watin forbids the use of this substance, on account
of its dangerous effects, and the consequences that
piay result to artists who are ignorant of its composi^
tion. I shall here add another consideration, which is '■
of importance to the art of painting ; namely, that
every arsenical substance makes itself known by the
pernicious influence it exercises on all metallic bodies
near it. This remark alone is sufficient to cause it
2 A 3
558 TREATISE ON VARNISHES.
to be banished from valuable pictures, and from all
painting of a delicate nature. The reader may see
under the article lem.on yellow, golden yellow, other
reasons for proscribing the use of orpiment, and of
white metallic oxides. When orpiment is slightly cal-
cined, it forms souci yellow.
Realgar. Red sulphurated oxide of arsenic.
Realgar differs from orpiment only by the quantity
of sulphur it admits into its composition, which re-
quires four-fifths of arsenic and one-fifth of sulphur.
This proportion gives to the whole a ruby colour ; and
hence the new name by which it has been distinguished.
This colour would entitle it to a distinguished place
among the substances employed in painting, were it
hot excluded by the same reasons as those mentioned
in the article on yellow oxide of sulphurated arsenic.
Realgar, as well as the preceding, is a volcanic pro-
duction which art can imitate, and which is then known
in commerce by the name ruby of arsenic, artificial
realgar.
Anatio. Charged extract of a colouring fecula*
Anatto is a colouring fecula of a resinous nature, ex-
tracted from the seeds of a tree very common in the
West Indies, and which in height never exceeds fifteen
feet. It is reduced by evaporation to a sort of extract,
which is spread out on boards to dry slowly. The
anatto dried in this manner has a more exalted colour
than that dried in the sun.
The Indians employ two processes to obtain the red
REALGAR. ANATTO, 359
fecula of these seeds. Thcry first pound them, and mix
them with a certain quantity of water, which in the
course of five or six days favours the progress of their
fermentation. The liquid then becomes charged with
the colouring part ; and the superfluous moisture is
afterwards separated by slow evaporaricn over the fire.
Tlie other method consists in rubbing the seeds be-
tween the hands in a vessel filled with^-ater. The co-
louring part is precipitated, and forms itself into a mass
like a cake of wax ; but if the red fecula, thus detach-
ed, is much more beautiful than in the first process, it
is less in quantity. Besides, as the splendour of it is
too bright, the Indians are accustomed to weaken it by
a mixture of red sandal wood.
Anatto, v.iiich is known to us only in commerce, is
sold under the form of calces, wrapped up in the leaves
.of the canna Indica. When in the state of paste, how-
ever, any form may be given to it at pleasure.
The natives of the West Indian islands used formerly
to employ anatto for paindng their bodies, &c. : at pre-
sent it is applied, in Europe, to the purposes of dyeing.
It, is employed to give the first tint to woollen stufts in-
tended to be dyed red, blue, yellow, and green, &c.
In the art of the varnisher it forms part of the com-
position of changing varnishes, to give a gold colour' to
the metals to which these varnishes are applied.
It ought to be chosen of a fiame colour, brighter in
the interior part than on the outside, soft to the touch,
and of a good consistence. The paste of anatto be-
comes hard in Europe ; and it loses some of its odour,
which approaches near to that of violets.
2 A 4
S60 TREATISE ON VARNISHES.
Bastard saffron. Flowers of the carthanms.
Bastard saffron is the flower of a plant known under
the name of carthamus. This plant, brought origi-
nally fî-om Egypt, has been naturahzed in France, and
is of great use in dyeing. It produces flowers with
fibrous fleurets, above an inch in length, cut into five
parts, and of a dark red safîron colour.
These flowers contain two colouring parts : one so-
luble in water, and which is thrown away ; the other
soluble in alkahne liquors. The latter colouring part
becomes the basis of various beautiful shades of cherry
colour, ponceau, rose colour, &c. It is employed for
dyeing feathers ; and it constitutes the vegetable red,
or Spanish vermilion, em.ployed by the ladies to
heighten their complexion. It is used by vaniishers
in some of their compositions ; but the colour is not
durable.
Bastard safîron cannot furnish its resinous colouring
part, provided with all its qualities, until it has been
deprived of that v/hich is soluble in water. For this
purpose, the dried fiovv^ers of the carthamus are inclosed
in a linen bag, and the bag is placed in a stream of
running water. A man with wooden shoes gets upon
th: bag every eight or ten hours, and treads it on the
bank until the water expressed from it is colourless.
These m.oist flowers, after they have been strongly
squeezed in the bag, are spread out on a piece of can-
vas extended on a frame, and placed over a wooden
box ; and they are covered with five or six per cent, of
their weight of carbonate of soda (salt gf soda). Pure
BASTARD SAFFRON. SPANISH VERMILION. 361
•Wafer is then poured over them; and this process is re-
peated several times, in order that the alkaU may have
leisure to become charged v^ith the colouring part,
which it dissolves. The liquor, when filtered, is of a dirty
red, and almost brown colour. The colouring part,
thus held in solution by an alkaline liquor, cannot be
employed for colouring bodies until it is free ; and to
set it at liberty^ the soda must be brought into contact
with a body which has more affinity for it than it has
for the colouring part. It is on this precipitation, by
an intermediate substance, that the process for making
Spanish vermilion is founded, as well as all the results
arising from the direct application of this colouring part
in the art of dyeing.
When carthamus is employed for a saffron colour,
it does not appear that any use is made of the colour-
ing part which is insoluble in water : painters seek after
that only which the dyers reject. It is not improbable
that a much better effect would be produced by em-
ploying the washed carthamus alone, and forming it
into a soft paste, by mixing it with the liquor containing
the colouring part, which might be afterwards preci-
pitated with a diluted acid.
Spanish vermilion.
To make this vermilion, pour into the alkaline li-
quor which holds in solution the colouring part of bas'
tard saffron, such a quantity of lemon juice as may be
necessary to saturate the whole alkaline salt. At the
time of the precipitation, the latter appears under the
form of a fecula full of threads, which soon falls to the
bottom of the vessel. Mix this feculent part with white
.362 TREATISE ON VARNISHES.
• talc (chalk of Briançon) reduced to fine pov.der, and
moistened with a little lemon juice and water. Then
form the whole into a paste ; and having put it in small
pots, expose it to dry. This colour, called Spanish ver-
milion, is reserved for the use of the toii^. ; but it
has not the durabiiity of that prepared froiiytochineal.
When this colourino: matter is destiiled for house-
IP
painting, &:c. as for the red inclining JiryeUow applied
to different articles, the liquor chafed v/ith the co-
louring part, precipitated by acid o|ilémon juice, is form-
ed into a paste v/ith white ar^i^xeous or marly earth,
which is divided into sniali^caKes, and then dried.
Red sandal wood.
Red sandal wood is a solid, compact, heavy wood,
with fibres sometimes straight and sometimes twisted,
and of an astringent savour. Its colour is a brownish
red. This wood is obtained from a large tree which i?
very abundant on the coast of Coromandel in the East
Indies.
It produces a dark red colour, which is employed in
dyeing, and communicates its colouring part to v»^ater
and to alcohol (spirit of wine), but not to oils. In
consequence of this property it may be employed in
the cofovation of changing varnishes.
I1ie voluminous work entitled Secrets des Arts et
Metiers says, that an extract of it obtained by a de»
coction in water is capable of colouring essential oils.
The author of that work never certainly tried the expe-
riment : but it communicates to alcohol ^ very bright
colour.
REDSA^NDAL WOOD. DUTCH PINKS. S63f
Dutch phihs.
Dutch pinks are much used in house-painting, &c,
iind in painting in distemper and in oil. They are sel-
dom employed by artists who paint pictures, because
they prefer yellov/s obtained from metallic substances,
as being more durable.
The Dutch pinks are composed of earthy parts
charged with the colouring matter or colouring recula
of certain plants. The basis of that of the first quality
is clay. Somedmes this base is marly (a mixture of
clay and chalk), and in certain cases it is carbonate of
lime (chalk). The last-mentioned composition of Dutch
pinks is iîiferior to the other two. It is much better
suited to painting in distemper than to oil painting.
; jyutcli pink from ivoad.
Woad is a plant common in France and in Spain.
"When cultivated it is superior for dyeing to the uncul-
tivated kind. The use of its colouring part is not con-
fined to dyeing ; it is extended also to painting, under
the denomination of Dutch pink.
To make Dutch pink, boil the stems of woad in alum
water, and then mix the liquor with clay, marl, or
chalk, which will become charged with the colour of
the decoction. When the earthy matter has acquired
consistence by evaporation, form it into small cakes,
and expose them to dry. It is under this form that the
Dutch pinks are sold in the colour shops.
56^ Treatise ox varnishes.
Another kind of Dutch pink.
This kind of Dutch pink is made with an aluminous
decoction of woad mixed with chalk, which becomes
charged with the colouring part of the plant. The use
of chalk renders this kind of pink inferior to all those
the base of which is of an argillaceous earth, or a very-
argillaceous marl. These compositions would, perhaps,
acquire some additional qualities were the clay, marl,
cr chalk mixed with a second, and even a third decoc«
tion of the plant.
Dutch pink from yellow berries»
Tîie small buckthorn produces a fruit, which whert
collected green are called graine (C Avignon, or yellow
berries. They have been distinguished by the name of
graine d'Avignon, because the plant which furnishes
them grows in great ^.bundance in the neighbourhood
of that city.
These seeds, v/hen boiled in alum water, form a
Dutch pink superior to the former. A certain quantity
of clay or marl is mixed ^vith the decoction, by which
means the colouring part of the berries unites with the
earthy matter, and communicates to it a beautiful yel-
low colour.
These yellow berries are much used in dyeing, and
even in cotton printing, which occasions a great con-.
sumption of yellows. •
The colouring part of P-utch pinks is darker accorj^
ing as the earthy substance employed is less mixed with
carbonate of lime (calcareous earth or chalk). Clay
-DUTCH PINKS, 56^
contributes to the durability of the colour. In conse-
quence of this principle, a Dutch pink resulting fj-onx
the decomposition of sulphate of alumine might be
substituted for the mixtures here described.
Brownish yellow Dutch pink hy the decomposition of
sulphate of alumine (aliim^.
Boil for about an hour in twelve pounds of water a
pound of yellow berries, half a pound of the shavings
of the wood of the barberry shrub, and a pound of
wood ashes. Then strain the decoction through a piece
•of linen cloth.
Pour into this mixture warm, and at différent times,
?. solution of two pounds of the sulphate of alum.ine
(alum) in five pounds of v/ater : a slight effervescence
will take place j and the sulphate being decomposed,
the alumine, which is precipitated, Vv'ill seize on the
colouring part. The liquor must then be filtered
through a piece of close linen, and the paste wliich re-
mains on the cloth, when divided into square pieces, is
exposed on boards to dry. This is brown Dutch pink,
because the clay in it is pure. The intensity of the co-
lour shows the quality of this pink, which is superior
to that of the other compositions.
Dutch pink with Spanish ivhite, or with ceruse, pre-
ferable for oil painting.
By substituting for clay a substance v/hich presents a
mixture of that earth and metallic oxide, the result will
"be Dutch pink, superior, no doubt, to any of those
the composition of which has been already given.
566 TREATISE ON VARNISHES.
The ceruse is ground on porphyry with water, and is
then separated from the porphyry with a wooden spa-
tula. In this state it is fit for use j but- it will be pro-
per to let it lose its humidity.
Boil separately a pound of yellow berries and three
ounces of the sulphate of alumine (alum) in twelve
pounds of water, which must be reduced to four pounds.
Strain the decoction through a piece of linen, and
squeeze it strongly. Then mix up with it two pounds
of ceruse and a pound of pulverized Spanish white.
Evaporate the mixture till the mass acquire the consist-
ence of a paste ; and having formed it it into small
cakes, dry them in the shade.
When these cakes are dry, reduce them to powder,
and mix them with a new decoction of yellow berries.
By repeating this process a third time, you will obtain
a Dutch pink so much charged with colouring matter
that it vwll be brown.
In general, the décoctions must be warm when they
are mixed with the earth. They ought not to be long
kept, as their colour is speedily altered by the fermen-
tation. Care must be taken also tc use a wooden spa-
tula for stirring the mixture.
Dutch pinks are employed in distemper and in oil./
They are however said, and with some foundation, not
to be durable. The colouring part in them is the less
fixed as the earthy substance combined with it contains
less chalk. Those, therefore, who wish to select the
best, must prefer those which produce the least effer*-
vescence with acids. In this point of view I have ex»
UMBER EARTH. S67
amined several of the English pinks, which occasioned
very little effervescence.
When only one decoction of woad or of yellow ber-
ries is employed to colour a given quantity of earth,
the Dutch pink resulting from it is of a bright-yellow
colour, and is easily mixed for use. When the colour-
ing part of several decoctions is absorbed, the compo-
. sition becomes brown, and is mixed with more diffi-
culty, especially if the paste be argillaceous ; for it is
the property of this earth to unite with oily and resi-
nous parts, to adhere strongly to them, and to incor-
porate with them. In the latter case, the ardst must
not be satistled with mixing the colour : it ought to be
ground; an operation which is equally proper for every
kind of Dutch pink, and even the softest, when de-
sdned for oil paindng.
Unicer earth.
Umber earth is a kind of clay mixed with a little
oxide of iron, which renders it dry, and is rather a bi-
tuminous earth slightly ferruginous than a brown ochre.
It is brought from Nocera in Umbria, a district cf
Italy, whence it derives its name. Somedmes it is
called brown ochre.
Umber earth is very much employed in painting fc«:
;i5rowns. When slightly calcined it acquires a brovaicr
' tone, and produces the colours of woad. If it be in-
closed in an iron box before it is subjected to the fire,
the colour will be mellower.
The bishopric of Cologne produces a kind of umber
earth which is heavier, as well as browner, and which
3GS "TREATISE ON VAKNISHZS.
has a stronger and more disagreeable smell than that or
Nocera. It is also more bituminous and more charged
with iron: in a word, it is inferior to it in quality.
In general, deposits formed by marshy plants, those
of morasses, which contain vegetables in part destroyed
and in part impregnated with bitumen, almost always
present a variety of limber earth, which might be em-
ployed, with success, for dark grounds. For delicate
works, however, such matters ought to be selected as
are least susceptible of alteration from time, and from
the contact of the oily bodies employed in paintings
The earth of Nocera is light, subtle, argillaceous, and
inflammable ; and it emits a fetid odour of coals when
exposed to a strong heat. Its qualities, established by
long experience, have insured it a preference from
painters.
Gree?! earth cf Saxony.
Nature often prepares colours to which art can make
no addition, when artists know how to limit the use
of them. Of this kind is the green earth of Saxony.
Hungary, Saxony, and Italy, wdiich contain abundance
of copper mines, furnish green earths, which are ap-
plied to particular objects, because the colouring prin"
ciple, Vv'hich is the same in them all, is not contained
in them all in the same proportions.
These coloured earths are of an argillaceous nature*
They arise from the oxidation of copper by water, or
rather from the decomposition of the sulphates of
copper (cupreous pyrites) v/hich are there abundant,
and which are conveyed by the water into banks of
marl, where the acid exchanges its metallic base. The
GREEN EARTH OF VERONA. TERRA MERITA. 369
intensity of the colour depends on the quantity of the
metallic oxide it contains. The earth of Kernhausen,
in Hungary, is of this kind. When earths are thus
charged with colouring matter they may be employed
m distemper, without any modification; but they are
not fit for oil painting until they have been corrected».
The colour would otherwise become a dark and obscure
green : in this case the colour requires to be mixed
with one part or a part and a half of ceruse. • Green
earth of Saxony requires also, for this Itind of paint-
ing, a correction nearly similar.
Green earth of Verona,
Green earth of Verona is dry, of à light green
colour, and when mixed with oil has not the same
fault as the green earth of Kernhausenj in Hungary^
and that of Saxony. It is equally proper for distemper
and for oil painting.
These two kinds of earth are real cupreous oxides.
Which contain a little carbonic acid (fixed air).
Terra mérita»
Terra mérita is the root of a plant of the family of
the canna Indica, which grows in great abundance in
every part of India, and which is carefully cultivated
by the Indians.
This slightly aromatic root is oblong and bent, with
knots at certain distances. It is heavy and compact ;
of the size of the little finger ; pale on the outside, and
yellow and even red in the inside when it is old. The
roots of the small species aro round ; and v/hen broken
exhibit concentric circles of a red colour.
2 b • .
370 Treatise on varnishes.
This red is very much used in dyeing. It is, hoW'
ever, found in general that it is inferior to woad, both
in regard to duration and to colour ; but dyers prefer
it in the use which they make of vellow, in dveing
scarlet, to heighten the colour of the cochineal or
kermcs, of which they compose the dyeing liquor.
Terra mérita is employed in varnishing only under
the form of a tincture. It enters into the mixture of
those colouiing parts which contribute the most to give
to metals the colour of gold. It ought to be chosen
sound and compact.
r^crdigris. Green oxide of copper bij vinegar.
Copper, when exposed to the air, becomes covered
with a kind of green rust, known under the name of
green oxide of copper. Verdigris is an artificial pro-
duction, arising from copper converted into oxide by
means of vinegar. This substance, the consumption
of which is very extensive, forms a valuable branch of
commerce. The whole almost of what is consumed
in Europe is manufactured at Montpellier, and in the
environs of that city. An attempt has been made to
establish a manufactory of the same kind at Grenoble;
but whether less care be taken there than at Montpel-
lier, to guard against adulteration, or whether the nature
of the wines of that country is not so proper for that
use as the wines of Languedoc, the verdigris of Mont-
pellier has always retained a superiority in the market.
Most families in the latter city are employed in ma-
nufacturing verdigris. The wines in that part of the
country being high coloured, spirituous, and charged
VJERDIGRIS. S71
with acid, facilitate the process for preparing it. Montet,
a chemist of Montpellier, gave a very correct detail of
the operation in the Memoirs of the Academy of Sci-
ences for 1750 and 1753, of which the following is
an extract :
" Large earthen jars are filled with grapes, from
which the stones have been extracted, and which have
been previously dried in the sun. They are then left
immersed for eight or ten days in wine, which has
already been employed for the preparation of verdigris,
and which has passed to the state of acid fermentation.
This wine is drawn off, and the grapes being slightly
squeezed, alternate strata of grapes and thin plates of
copper are placed in the same jar, beginning and end-
ing with a stratum of grapes. The vessels are then
covered, and left in that state for five or six days.
" When it is observed that the first plates have ac-
quired a green colour, with white spots, they are taken
out; and a certain number of them are arranged, one
above the other, in a cellar, which ought neither to
be too dry nor too damp, where they are left to dry.
" They are then moistened on the sides with the
same kind of wine, or with water; and this operation
is repeated two or three times. In the mean while
the metallic matter, penetrated by the wine, swells and
forms a sort of green crust, which is carefully scraped
off. In this manner the whole plate of copper is con-
verted into a kind of rust, which is afterwards put into
bags of sheeps* leather, and exposed to the air to dry.
It is under this form that it is sold in the shops. The
"\)xide, which after this operation may be considered
2 B 2
S72 . TREATISE ON VARNISHES,
as copper penetrated by the acid of the vinegsr, doeç
not however possess any saline properties. It is an
oxide of copper, which contains more carbonic acid
(oxygen united to carbon) than vinegar : it holds a
mean rank between the oxide and the saline state.
" It ought to be chosen dry; of a beautiful colour,
and as free from spots as possible.
" Verdigris is much employed in oil painting and
in distemper, as well as for colouring prints and draw-
ings; but it requires more care in the application than
any other colour, whether used alone, which is rare,
or employed in compositions. It may be considered
as one of the first ingredients in mixtures ; but de-
licate painting would not find in verdigris all the purity
it requires ; and therefore, when used for that purpose.
It is subjected to a kind of purification which gives it
a saline character, and at the same time deprives it of
all those iinpurities which are found in common vei%.
«ligris."'
PURIFICATION OF VERDIGRIS.'
Calcined verdigris. Distilled verdigris. Crystallized-
verdigris. Acetite of copper.
Purification disengages from the oxide of copper
those matters which are foreign to it. There ars
indeed observed in it fragments of the grapes, and small
laminae of corroded copper, which have escaped oxida-
tion. All these impurities are separated from it by
uniting it v/ith a new quantity of the acid of vinegar j
and by this addition the cupreous oxide acquires ther-i.
PURIFICATION OF VERDIGRIS. SYÇ
saline properties: namely, those of dissolving in water
and of crystallizing.
The industry of the Dutch has engrossed this branch'
of manufacture, the crude materials of which are in
the hands of the French.
One part of pounded verdigris, and from six to
eight or more parts of vinegar, according to its
strength, are boiled in large copper kettles. The ebul-
lition is continued an hour, during which time the
matter is stirred with a rake. When the oxide is com-
pletely dissolved, the kettles are taken from the fire, and
the liquor is suffered to remain at rest till it becomes
clear. Osier twigs about a foot long, and split into
four parts throughout almost their whole length, are
immersed in the liquor, the four parts being sepa-
rated by wooden wedges, which leave an interval of
about two inches between them at the extremity : these
pyramids are suspended by packthread, and left in the
liquor till they become covered with crystals.
They are then taken out, and the saline liquor is
evaporated till it form a pellicle. It is then left to
cool, and the pyramidal sticks are again immersed ii>
it, till they become charged with a new quantity of
crystals. This operation is continued until the inter-
vals between the parts of each stick are entirely filled
with cr)'stals, so as to represent a solid pyramid, the
weight of which is about three or four pounds. The
crystals are of a rhomboidal form; and when new are
transparent, and have a beautiful green colour. At the
end of some time they effloresce, that is to say, become
^hite, and lose their transparency by the effect- of jiir
2b 3
574 TRÎATISE ON VARNISHES.
sensible evaporation. These crystals form acetite of
copper^ and are known to artists by the name of
distilled verdigris, crystallized verdigris, calcined ver-
digris*.
Acetite of copper, when new, is of a beautiful trans-
parent green colour : when old and pulverulent it ex-
hibits a dull green. In the latier state it is more proper
for being ground v^dth boiled oil. In general all colours
of a saline nature, destined to be ground with oil,
must be deprived of their water of crystallization ; and
this can be accomplished only by reducing them to
powder, and exposing them to the sun, or in a stove,
before they are mixed with the oil.
Colours prepared with acetite of copper (crystallized
verdigris) are much brighter than those composed with
verdigris. But the high price of this colour prevents
it from being employed in all cases. It is therefore
reserved for painting of the noblest kind, and for that
* Artists have given to certain matters employed in the arts,
denominations which are more calculated to embarrass tlian td
encourage amateurs. I myself have often been confounded by
tlie word calcined, which is applied to several substances as an
epithet. This expression is often employed in regard to orpi-,
ments (yellow sulphurated oxide of arsenic). If this substance
were treated over an open fire, it would be dissipated 3 and in close
vessels it would assume a rose or red colour, and form ruby of
arsenic.
The case is the same with acetite of copper, which is sometimes
called calcined verdigris. Calcination would revive the copper: tlie
same denomination has been applied to sulphate of zinc.
This is a real abuse of words, which habit preserves among our
workmen, and which ought to be banished if we are desirous of
rendering the language of tlie arts intelligible.
SAP GREEN. 375
•applied by the varnisher to certain delicate articles,
such as works of papier mache, metals, &c.
Those who paint pictures are accustomed to grind
this colour with oil of pinks, and to put it into small
bladders, which they prick in order to extract by
pressure the quantity they are desirous of using. This
colour extends exceedingly well. It possesses trans-
parency, and is employed with success for glazing
certain argentine parts to represent sheets of water.
When applied to metal, the reflection of the Hght
produces a very fine effect, which is still heightened
by the colour. This colour, when mixed with copal
varnish and applied to foil, produces a very rich effect.
LiqJtid vd'digrisjor colouring maps, ^c.
Put an ounce of pulverized verdigris into the bot-
tom of a matrass, with eight or ten ounces of good
distilled vinegar. Place the matrass on a warm sand
bath, and shake it from time to time, till the liquid
has acquired a beautiful dark green colour inclining to
blue. Leave the mixture at rest, that it may become
clear, and pour it into a clean vessel, which must be
closely shut. This preparation is used for colouring
maps and prints. The colour may be lowered, if ne-
cessary, by adding a little w^ater or distilled vinegar in
the shell into which the brush is dipped.
Sap green.
Sap green is the feculent part of the fruit of the
buckthorn. The berries, when black and very ripe,
are bruised, and subjected to a press, in order to ex-
2 s 4
S76 TREATISE ON VARNISHES,
tract the juice. This juice is mixed with a little sul-
phate of alumine (alum), dissolved in a sufficient quan-
tity of water, and the whole is evaporated over a slow
fire till it is brought to the consistence of honey. The
extract is then put into a swine's bladder, and hung
up in the chimney to dry.
When this extract is to be \ised, dilute it with a
little water, to which it will communicate a very beau-
tiful green colour. This colour is used only by fan-
painters, draftsmen who dra\y plans, and for other
works of the same kind.
It ought to be chosen compact, heavy, and of a
beautiful green colour.
C 377 ]
CHAPTER II.
'Philosophical account of the origin of colours, applied ta
'mater kd colours, simple and componnd; with a description
of the processes which art employs to vary the inanler and
richness of the tints resulting from the mixture <f them.
One of the most interesting phenomena in nature
ever subjected to philosophical research, is that which
accompanies the emission of the solar light. Mankind
were far from imagining that this subtile fluid, this
agent of the numerous phsenomena which constitute
the life of nature, this generator of the varied colours
which ornament the organized bodies that cover the
earth and people the seas, belonged to the order of
compound substances. The decomposition of it, dis-
covered by the immortal Newton, and traced out in
^1 its details by those astonishing experiments which
compose his optics, soon became the basis of the
theory which that learned author has established in
regard to the nature of light, and to the origin of the
colours that strike our organs of vision.
Isaac Vossius, who lived before Newton, had en-
tertained an idea, and even asserted, that the colours
which tinge those objects that present themselves to
our eyes existed in the solar rays. But this theor)--,
supported by no kind of experiment capable of serving
as an authority, was classed among the number of
those ingenious hypotheses which occupied the philo-
sophers of his time. The idea of Vossius was however
5
378 TREATISE ON VARKISHE3,
realized by the experiments which the immortal NewtoR
made with the prism.
This philosopher indeed proved that the rays of
light, which he subjected to experiments both by
analysis and synthesis, were composed of seven pri-
mitive rays, each ditFerent from the other, not only
by the vaiiety of their colour but also by their different
refrangibility.
From this decomposition of light he proved that
these coloured rays, when separated from each other,
and in some m.easure insulated, excite in us the sen-
sation of a fixed and primitive colour. The following
is the order observed in the decomposition of a ray of
light received on the refracting surface of a prism coni-
mencing at the lowest: red, orange, yellow, green,
blue, purple, and violet.
The facility of separating colours, in analysing a
bundle of rays, is the eflect of the different refrangi-
bility of each of these rays. Newton has proved also
that the degree of the reflection of each coloured ray
is proportioned to that of its refraction.
The theory of colours was the necessaiy conse-
quence of these experiments; the aggregate of which
composes the system of optics, that master piece of
the human genius. It indeed follows from it,
1st. That a ray of light is composed of all the pri-
mitive colours, pure and unalterable, and therefore
free from every secondary mixture that might weaken
its essence.
2d. That every colour is produced merely by the
decomposition of a ray of light.
4
ORIGIN OF COLOURS. 5*79
This phaenomenon depends on the essential com-
position of the bodies which concur to produce itj on
the pecuHar configuration of their suriiices, on their
degree of density, and on their interior disposition,
which renders them capable of absorbing a certain
portion of the ray of light, and of transmitting another
to our senses. The coloured body appears then under
the simple colour of the ray which is reflected.
In some bodies the difference in the texture of their
surface, in the nature of the laminae of which they
are composed, as well as in their thickness, produces
phsenomena of refraction and reflection more varied,
which concur to promote the union of several primidve
coloured rays, and consequently to produce the ap-
pearance of secondary or compound colours : changing
material colours arise from this cause*
Intermediate colours might easily be made in the
series of those given by the prism ; but one remarkable
effect is, that the less compound a colour is, it is so
much the brighter and more perfect. By rendering it
gradually more complex, it is at length destroyed, the
ray of light being restored, such as it was before its
decomposition.
According to the theory of optics, white, which
results from the union of all the primitive coloured
rays, and which constitutes a ray of light; black,
which absorbs them entirely, and which is only the
effect uf that absorption, are not colours. The theory
of material colours seems to contradict these ingenious
results, which arise from a philosophical examination
of the nature of light. White and black exist in sub-
SSO TREATISE ON VARNISHES,
Stance. They seem even to concur towards increasing
the number of the primitive colours, in thé order of
material bodies. They become, at least in the hands
of the artist, new means and new agents to modify the
tones of the positive colours of an earthy or metalh'c
nature.
The philosophy of the heavens seems to be richer
in colours than that of the earth. The former admits
of seven primitive colours j and four only are found in
the latter, if we suppress white and black. Of this
kind are yellows, reds, and greens, to which I shall add
the blue of ultramarine. Indigo blue, violet, and of ange,
are the secondary results of certain mixtures, by which
art, the imitator of nature, has found' means to ap-
proach those tones that belong to the seven primitive
colours.
By admitting white and black, which are employed
on the palette of the painter, we shall have six colour-
ing substances, with which all the different tints of
nature may be imitated. It is by the help of simple
or com.pound mixtures, that art is able to display the
magic of illusion in fine paintings.
A knowledge of mixtures is not the least part of tlie
art of painting. It is by means of these mixtures that
the art has been enriched by establishing another order
of colours; that is to say, the facdtious, secondary,
or intermediate colours. It will be here proper to give
a general view of the effect of these mixtures, and of
the peculiar attributes of the primitive material colours.
It will consist of a certain number of precepts, which
are generally considered as inseparable from the art.
..MIXTURE OF COLOURS,., 581
- Black increases the obscurity of all colours, and
even effaces them, if the quantity be considerable and
predominant.
White renders yellows, reds, and blues, lighter. The
strength of the tints depends on the respective quan-
tities of the two substances mixed. When mixed with
blue, the result is a tint more or less light, which
represents the azure colour of a beauLiful fky.
White, judiciously mixed with yellows and reds,
produces a tint which approaches to flesh colour. If
a little ceruse be ground with very clear gum water,
by adding a small quantity of liquid red, and a little
lemon yellow, you will . obtain tints of flesh coloui'
which may be. varied ad infinitum. With reddish brown,
the result will be beautiful crimson j with red, a beau-
tiful carmine colour..
White, mixed with a little black, produces a gray
more or less (^rk : with blue and a small quantity of
black it gives a. beautiful pearl gray.
Yellow and blue give rise to several kinds of green,
the brightnegs and splendour of which depend on the
manner in which they are combined : with thin liquid
blue, you will obtain an exceedingly rich colour for
.miniature, painting.
Golden yellow and violet compose admirable liquid
earth colours for miniature painting.
. A yellow colour may, in like manner, be obtained
with an orange colour and yellowish green.
-■rRed or vermilion loses some of its splendour and
hardness when the lights are brightened. wAxh white or
with Naples' yellow.'-
3S2 TREATISE- ON VARNISHES.
Reddish brown and lemon yellow, mixed with gum
water, give an am-ora colour. By adding thin liquid
blue you will obtain a brown wood colour, which is a
valuable discovery for miniature painting.
Liquid red, mixed with violet, exhibits a rich purple :
a greater or less quantity of either of these substances
gives a crimson, more or less red.
Liquid red, with meadow green, gives a wood
colour, which is employed in miniature painting to
represent terraces and the trunks of trees ^.
Painters mix carminated lakes with cinnabar or ver-
milion to produce the beautiful effect of bright red,
destined to represent certain red parts, such as the
mouth, the apertures of the nostrils, &c.
All arts admit of general principles, which have
been established by long experience. If those, a sketch
of which has here been given, are acknowledged by
the great painters ; if they follow them in the execu-
tion of their master-pieces, they ought not to remain
unknown to artists, who devote themselves to house-
painting, Scc. nor to amateurs who are desirous of
being^ initiated in everv branch of this art.
in gen.-ral, great colorists devote their whole atten-
tion to manage the white in shades, in order that they
may avoid mealy and opake tones. A mixture of oxide
of lead and antimony, known undef the name of
Naples yellow, is a great assistance to them. It sup-
* W'hen mention is made of a liquid colour, or of its mixture
with gnm water, the case is applicable to miniature painting. The
other combinations of colours relate to die other kind* of paintings
and pjrticuhirly oil painting.
Mixture of colours. 38S
plies the place of white in all cases when it is necessary
to brighten the half tints, or to give reflection without
experiencing all its inconveniences. With yellow also
bright grays may be produced in the shades, by mix-
ing it with different blacks, and even with ultramarine,
when the composition is required to be ]-ich and highly
finished.
■ Artists often agree in admitting denominations which
express the state or extent of the composition of a sub-
stance. Thus painters have given the name of i:irgi}i
tints to those which are composed of only two sub-
stances, such as white and blue, white and red, white
and yellow, white and lake, and so of the other simple
combinations which would result from tîie mixture of
other colours witliout the white: such, for example,
as the green produced by Naples yellow and prussiate
of iron (Prussian blue); the orange colour which re-
sults from a mixture of Naples yellow and red oxide
of lead (minium); the violet produced by a mixture of
red sulphurated oxide of mercury (cinnabar) and prus-
siate of iron. These virgin tints form second local
colours, which some painters introduce on their palette,
like secondary colours, which are not simple shades of
a coloured body, but the mixture of two or more
primitive colours.
All simple or compound colours, and all the shades
of colour which nature or art can produce, and wliich
might be thought proper for the different kinds of paint-
ing, would form a very extensive catalogue, were we to
take into consideration onlv certain external characters
S84 TREATISE ON VARNISHES.
or^the intensity of their tint. But art, founded on the
experience of several centuries, has prescribed bounds
to the consumption of colouring substances, and to the
application of them to particular purposes. To cause a
substance to be admitted into the class of colouring
bodies employed by painters, it is not sufficient for it
to contain a colour: to brightness and splendour it
must unite also durability in the tint or colour \Vhich it
commmiicates. Thus every earthy, vegetable, or animal
matter, of a tint more or less developed, cannot always
be considered as a colouring matter necessary to paint»
ing. It cannot assume a place on the painter's palette^
or in the pot of the varnisher, until experience has de-
termined in regai'd to its essential qualities.
But though a coloured substance may seem impro-
per for the usual purposes of the different kinds of
painting, it does not thence follow that it ought to be
rejected entirely. Colours, the employment of which
cannot be generalized without inconvenience, are appli-
ed every day to particular uses in distemper and in the
art varnishing. Such", for example, are certain colours
extracted from vegetables, which compose the light
and dark Dutch pinks ; and which painters, jealous or
the duration of the tints they employ, banish, and very
justly, from their grand compositions. Such, also, are
other substances furnished by the mineral kingdom, ♦
yellow and red sulphurated oxides of arsenic (orpimeni:
and realgar), which refuse to harmonize with the co-
lours most in use, and which at length develop quali-
ties the more destructive, as they extend even to all me-» .
MIXTUP.E OF COLOURS. 385
tallic colours in contact with them, or which arc near
them. This destructive effect arises from the arsenic
which forms a part of them*.
* That piece of board disting\;ished by the name of the painter's
palette is a real repository of the primitive colours, arranged in a
line. Another line, parallel (o the former, is destined for the com-
pound or secondary colours. The simple colours are white, Naples
yellow, ochre de rue, Sienna earth, still more beautiful tlian ochre
Je me, red or burnt ochre, red earth or burnt ochre de rue, ver-
milion, lake, prassiate of iron (Prussian blue), Saxon blue, ul-
tramarine, black from burnt vine twigs, ivory black, kc. All these
colours arc ground in oil of pinks, and have the necessary con-
sistence.
Sometimes, wlien colours arc applied to strata of paint, or to
sketches too recent, the paint sinks, and assumes a gray appearance.
■v\ hich conceals the real colour of the tints. White of egg, beat
up with some drops of alcohol (spirit of wine), and then applied
with a clean dry sponge, will restore their former lustre ,• but in
all cases, without excepting those even which require celerity of
execution, the painter who is desirous to ensure the durability of
his work will take care not to apply varnish until the colours have
become thoroughly dry, under the white of tggj which will not be
the case till the end of a year. After this interval, the same sponge
which served to apply the white of egg, if dipped in a little water,
uiil remove it, under the form of a yellowish frotli. As long as
gentle friction with the sponge produces froth there i» reason to
conclude that the white of egg is not entirely removed.
This intermediate application of white of egg, between the pe-
riod when valuable paintings are finished and that when they 'are
varnished^ is attended with two advantages, as it defends the co-
lours from the prejudicial impression of the air, and frees tlieni
from a yellowish tint which arises from the oil, or perhaps from
the colours themselves. If these conditions be strictly observed,
the colours will appear under the varnish in all tlie beauty and rich-
ness ot their tiiits. Some of the English painters, too anxious to
receive ihe frui's of their com.poshion, neglect these precautions.
2 c
^86 TREATISE ON VARNISHEû.
But the coloured bodies which artists who paint pic-
tures proscribe, find a very extensive employment in the
hands of the house-painter. The changes which may
take place in the tone of uniform colours do not pro-
duce so important effects as in a painting, where the least
change in the tints destroys the harmony, contradicts
the rules of perspective, and substitutes for the real
tones of nature degraded tones which are absolutely
foreign to it.
In the application of the colours which house-painters,
kc. destine for varnish, the transition of one tint into
another, more or less dark, is insensible, because it is
general. Nothing offends the eye, which becomes ac-
customed to that transition, which may even de\'iate
from the first tone ; and if the efl'ect no longer appears
to be the same, when remembrance recalls the fust mo-
ment when the painting possessed all its freshness, it
however exhibits nothing disgusting.
Several artists even paint in varnish^ and apply it with the colours.
This precipitate method gives brilliancy to their compositions at
the very moment of their being finished j but their lustre is tem-
porary, and of short duration. It renders it impossible for them
to clean their paintings ; which are besides liable to crack and to
lose their colour. In a word, it is not uncommon to see an artist
survive his works, and to have nothing to expect from posterity.
Notliing that relates te the house-painter is foreign to the artist
of a higher order, who paints compositions : in like manner, the
precepts admitted by the celebrated painters deserve tlie attention
of the varnisher, to whom the painter entrusts his greatest in-
terests.
The observations contained in this note are the brief result of
some instructive conversations I had -with Saintours, a celebrated
painter, my friend and relation.
COMPOSITION OF COLOURS. 387
This consideration is sufficient to authorize the use
of colouring substances, more common, and conse-
quently less expensive, in cases when the artist has to
supply an extensive consumption.
Having said enough in these preliminary observations
respecting the nature of colouring parts, and the theory
of the effects of their mixture, U'e shall proceed to the
different compositions which the varnisher employs.
COMPOSITION OF COLOURS.
BîacL
Usage requires attention in the choice of the matters
-tlestined for black. The bodies which produce it do
not all give the same tone. According to the catalogue
of colouring bodies, several of them furnish black.
The carbonaceous parts of peach stones, of the beech
tree, of ivory, of vine twigs, lamp black, &c. all con-
cur towards this object, but in a different manner. The
" following are their properties :
Black from peach stones is dull.
Ivory black is strong and beautiful, when it has beeu
well attenuated under the muUer.
Black from the charcoal of beech wood, ground on.
porphyry, has a blueish tone.
Black composed of lamp black is of a minime co-
lour. It may be rendered mellower by making it witli
black which has been kept for an hour in a state of
redness in a close crucible. It then loses the fat matter
which accompanies this kind of soot.
Black furnished by the charcoal of vine twigs, ground
2 c '2
-fSë TREATISE ON VARNISHES.
on porphyry, is weaker, and of a dirty gray colour,
when coarse and alone ; but it becomes blacker the
more the charcoal has been divided. It then forms a
black very much sought after, and wliich goes a great
way.
Painters, for the most part, confine the use of blacks
to that made from burnt vine twigs or peach stones, to
black of Cassel or Cologne, and even to that of asphal-
tum, the vigorous and transparent tones of which ex-
hibit qualities not possessed by the rest.
The consumption of lamp black is more extensive in
common painting. It serves to modify the brightness of
the tones of the other colours, or to facilitate the com-
position of secondary colours. The oil paint applied
to iron grates and railing, and the paint applied to
paper snufF boxes, to those made of tin plate, and to
other articles with dark grounds, consume a very large
quantity of this black. Great solidity may be given to
works' of this kind by covering them with several coat-
ings of the golden ^/arnish of the fifth genus, No. 98.,
which has been mixed with lamp black washed in
v;ater, to separate the foreign bodies introduced into it
by the negligence of the workmen w^ho prepare it.
After the varnish is applied the articles are dried in a
stove, by exposing them to a heat somewhat greater
than that employed for articles of paper. Naples yel-
low, which enters into the composition of black var-
nish, is the basis of the dark brown cbser\^ed on tobacco
boxes of plate iron, because this colour changes to
brown when dried with the varnish.
COMPOSITION OF COLOURS. 389
JTldte,
White, v/hen employed without any mixture, is in
general very dull. Those who paint decorations are
accustomed to heighten it with a small quantity of blue,
which renders it brighter. All whites, or all white
matters, are not equally proper for painting in varnish
or in oil. Chalk is fit only for distemper, because the
two other kinds of painting give it a brown tint.
For a distemper white, then, take Bougival white, a
kind of marl or chalky clay, and having ground it with
water, mix it with size. It may be brightened by a
small quantity of indigo or charcoal black, ground ex-
ceedingly fine.
The v,4iite destined for varnish or for oil requires a
metallic oxide, which gives more body to the colour.
Take ceruse, therefore, reduced to powder*, and grind
it with oil of pinks and a quarter of an ounce of suU
* The amateur is not always flimished with instruments like the
professed painter. Ceruse may be pulverized by the coiourman ;
but it is not always free from mixture. There is one simple me-
thod, however, by which this substance may be reduced to pow-
der, without a mortar, and without much trouble.
Place on a large sheet of paper a hair sieve, and move a cake of
ceruse over it in a circular direction, pressing it a little against the
haii'-cloth. The friction of die latter will detach from it a fine pow-
der, which may be collected on the sheet of paper. Should tlie
dust fly upwards and prove incommodious, which is the case when
the ceruse is veiy dry, tlie operation may be performed in a cur-
rent of air. The ceruse, when thus divided, may be easily ground
on a piece of porphyry.
A sieve made Mith metallic cloth of fine brass wire will answer
better for this purpose tlian a hair sieve : it is much more durable.
2c 3
390 TREATISE ON VARNISHES.
phate of zinc (white vitriol) for each pound of oiL
Apply the second coating without the addition of the
sulphate of zinc, and suffer it to dry. Cover the
whole with a stratum of the varnish No. 3. This co-
lour is durable, brilliant, and agreeable to the eye.
Boiled linseed oil might be employed in the room of
oil of pinks ; but the colour of it would in some degree
injure the purity of the white. Painters are accustom-r
ed to place on the porphyry slab, along with the co-
lour, a spoonful of unprepared oil of pinks or nut oil,
to facilitate the extension of the matter, and to retard
the evaporation and desiccation of the boiled oil. The
dose of this oil cannot be determined ; because it ought
to be proportioned to the quantity of colour employed.
My method allots a common spoonful for eight or nine
ounces of matter, to be ground.
White is prepared also with pure white oxide of lead,
ground with a httle essence, added to oil of pinks, and
mixed with the varnish No. 14. The colour may be
mixed also with essence diluted with oil, and without
varnish, which is reserved for the two last coatings.
If a dull white be not required, the colour is height-
ened with a little prussiats of iron (Prussian blue), or
with a little indigo, which is here preferable, or v/ith.
a little prepared black. The latter gives it a gray cast.
But pure white lead, the price of which is much higher
than ceruse, is reserved for valuable articles. In this
particular case, if a very fine durable white be required,
grind it with a little essence, and mix it with the Aar-
nighNo. 3,
COMPOSITION OF COLOURS, "\39Z'
OF COMPOUND COLOURS IN WHICH CERUSE
PREDOMINATES.
Light gray.
Ceruse ground with a little nut oil or oil of pinks, and
mixed with a small quantity of lamp black, composes
a gray more or less charged, according to the quantity of
black. With this matter, therefore, mixed with black
in different doses, a great variety of shades may be
formed, from the lightest to the darkest gray.
If this colour be destined for distemper, it is mixed
with water. If intended for oil painting, it is ground
with nut oil or oil of pinks ; and with essence added
to oil if designed for varnish. This colour is durable
and vejy pure if mixed with the varnish No, 12. : the
varnish No. 14. renders it so solid that it can bear to
be struck with a hammer, if after the first stratum it
has been appUed with varnish, and without size.
These light gray grounds are much sought after for
apartments, especially when exposed by their situation
to the strong light of the sun. The varnishes which I
have here pointed out for this purpose are stronger than
those made with alcohol. They are attended with the
inconvenience of emitting some smell for a few rhonths ;
but this may be easily prevented by glaring with an al-
coholic or colourless varnish. When appHed alone, and
without colour, the glazing is brighter, and the colour
of the ground appears with more lustre, but it is easily
Scratched. For the last coating the varnishes Nos. S,
ïind -i, are proper j and for the darkest gray No. 6.
2 c 4
392 TREATISE ON VARNISHEÎ.
Pearl gray.
If a particle of blue be substituted for the black in
the preceding composition, or if this blue be combined
with a slight portion of black, you will obtain silver or
pearl gray ; but that the ground may not be altered by
a foreign tint, tlie colour for the first coating must be
ground with essence mixed with a little oil of pinks: for.
the succeeding strata, grind with the varnish No. 12.
softened with a little oil of pinks, and mix the colour
with the same varnish. The pearl gray will be sdll
brighter, if the last stratum be glazed with the alcoholic
varnish No. 3. mixed with a little colour.
Flaxen gray.
Ceruse still predominates in this colour, which is
treated as the other grays, but v.-ith this difference, that
it admits a mixture of lake instead of black. Take the
quantity, therefore, of ceruse which ^^ou may think
necessary to employ, and grind it separately. Then
mix it up, and add the lake and prussiate of iron (Prus-
sian blue) also ground separately. The quantities of the
last t^vo colours ought to be proportioned to the tone of
colour required to be given to the ardcle painted.
This colour is proper for distemper, for varnish and
oil painting. For varnish, grind it with the vaniish
No. 13., to which a little oil of pinks has been added,
and then mix it up with the varnish No. ] 4. For oil
painting, grind with unprepared oil of pinks, and mix
up with resinous drying nut oil*. The painting is
brilliant and solid.
* Sc-. Parti, p. 101.
COMPOSITION OF COLOURS. S93
When the artist piques himself on care in the prepa-
i ation of those colours which have splendour, it will be
proper, before he commences his labour, to stop up
the holes formed by the heads of the nails in wainscot-
ing with a cement made of ceruse or with putty.
The first stratum of colour, taking flaxen gray for
an example, is ceruse without any mixture, ground
with essence added to a little oil of pinks, and mixed'
up with essence. If any of the traces of this first
stratum are uneven, it will be proper to rub it lightly-
•.vhen dry with pumice stone. This operation, which
seems so remote from finishing, contributes greatly to
the beauty and elegance of the polish when the varnish
is applied.
The second stratum is composed of ceruse, changed
to flaxen gray by the mixture of a little Cologne earth,
as much English red or lake, and a particle of Prus-
sian blue. First make the mixture with a small quan-
tity of ceruse, in such a manner that the result shall be
a smoky gray, by the addition of the Cologne earth.
The red which is added makes it incline to flesh co-
lour, and the Prussian blue destroys the latter to form
a dark flaxen gray. The addition of ceruse brightens
the tone. This stratum and the next are ground, and
. mixed up with varnish as before. "
This mixture of colours, which produces flaxen gray,
has the advantage over pearl gray, as it defends the
ceruse from the impression of the Liir and of the light,
which makes it assume a yellowish tint. Flaxen gray
composed in this manner is unalterable. Besides, the
■essence which forms the vehicle of the first stratum
S^é tri:atise on varnishes,
contributes to call forth a colour, the tone of which
decreases a little by the effect of drying. This observ^a-
tion ought to serve as a guide to the artist, in regard to
the tint, which is always stronger in a liquid mixture
than when the matter composing it is extended in a thin
stratum, or when it is dry.
I must here obsen^e, that every kind of sizing, which
according to usual custom precedes the application
of varnish, ought to be proscribed as highly prejudi-
cial when the wainscoting consists of fir wood. Sizing
may be admitted for plaster, but without any mixture.
A plain stratum of strong glue and water spread over it
is sufficient to fill up the pores in such a manner to pre^
vent any unnecessary consumption of the varnish.
Colour of oak wood.
The basis of this colour is still formed of cçruse.
Three-fourths of this oxide and a fourth of ochre de^
rue, umber earth, and yellow de Berri ; the last three
ingredients being employed in proportions which con-
duct to the required tint, give a matter equally proper
ibr distemper, for varnish, and for oil.
Colour of 2ial nut-tree 2iood-
A given quantity of ceruse, half that quantity of.
ochre de rue, a little umber earth, red ochre, and yel-
low ochre de Berri, compose a colour proper for dis-
temper, for varnish, and for oil.
For varnish, grind v/ith a httle drying nut oil, and
mix up with the varnish No. 1 4.
For oil paindng, grind with fat oil of pinks added
COMPOSITION OF COLOURS. S95 '
fo drying oil or essence, and mix up with plain dr^^ing
oil or with resinous drying oil*,
YELLOW.
Pure and modified yellows»
Yellow, and all its transitions to the varied tones to
^hich it is brought by art, are often employed in paint-
ing. The different bases of this colour, as well as reds,
mixed with white by an expert hand, soon give the
tones which approach the lights of flesh colour.
Naples and Montpellier yellow.
^Tapies yellow, or that of Montpellier, the compo-
■èition of which is simpler, yellow ochre of Bern, or of
any other place, mixed with ceruse ground with water,
if destined for distemper; or drying nut oil and essence,
. in equal parts, if intended for varnish ; and mixed up
with the varnish No. 12. if for delicate objects, or with
the varnish No. 14., give a very beautiful colour, the
splendour of which depends, however, on the doses of
the ceruse ; and these must be varied according to the
particular nature of the colouring matter employed. If
the ground of the colour is furnished by ochre, and if
oil painting be intended, the grinding with oil added
to essence may be omitted, as essence alone will be
suflicient. Oil, however, giyes more pliabihty and
more body.
Jonquil.
Jonquil is employed only in distemper. It may,
h-.)v ever, be used with varnish. A vegetable colour
* See Part I. pa^c 101.
396 TREATISE ON VARNISHES.
serves it as base. It is made with Dutch pink and
ceruse.
It is ground with the varnish No. 1 3. and mixed up
with the varnish No. 14.
Lemon yellow,
A beautiful lemon yellow may be formed by follow*
ing the prescription of the old painters, who mixed to-
gether red sulphurated oxide and yellow sulphurated
oxide of arsenic (realgar and orpiment). But these co-
lours, which may be imitated in another manner, have
against them the unfavourable opinion occasioned by
their poisonous quality. It will, therefore, be better
to substitute in their room Dutch pink of Troyes and
Naples yellow. This composition is proper for distem-
per and for varnish. When ground, and mixed with
the varnishes indicated for the preceding colour, the
result is a bright solid colour without smell, if an alco-
holic varnish be applied for the last stratum.
Artists recorJ^mend for a straw colour a mixture of
ceruse and orpiment, in doses proportioned to the re-
quired tone of colour. The case is the same in regard
to the composition of the golden yellow colour about to
be mentioned. The success of these mixtures is not
always certain; and there seems to be reason to sup.
pose that it arises from some deception on the part of
the colourman, who substitutes for ceruse another
white of an argillaceous nature. A painter one day
shovyed me a mixture of ceruse and orpiment made in
large doses for a very considerable work of a straw co-
lour. The mixture in the course of some hours had .
COMPOSITION OF COLOURS. 39*7
acquired a brown olive colour. This eliect could be
ascribed only to the presence of orpiment, the sulphu-
reous parts of which had exercised an action on the
metallic oxide. A slight odour of sulphurated hydrogen
rendered this circumstance very evident. But as the
orpiment sold m the shops is sometimes the result of an
artificial combination, in which the sulphur is not al-
ways united, I thought it proper to ascertain whether
natural orpiment crystallized in large lamina would
produce the same change on ceruse. 1 tried mixtures
in different proportions,, all of which manifested in
their tones a transition towai;ds brown, and this transi-
tion was the more abrupt according as the orpiment
predominated. These results, which accident enabled
me to ascertain, have induced me to employ another
basis than oxide of lead as the principal ground of the
golden yellow colour, for which painters recommend
ceruse.
Golden yellojv colour.
Cases often occur when it is necessary to produce a
gold colour without employing a metallic substance. A
colour capable of forming an illusion is then given to
the composition, the greater part of which consists of
yellow. This is accomplished by Naples or Montpel-
lier yellow, brightened by Spanish white, or by w^hite
of JNIorat mixed with ochre de Berri and red sulphu-
rated oxide of arsenic (realgar). The last substance
even in small quantity, gives to the mixture a colour
which imitates gold, and which m.ay be employed in
-distemper, in varnish, or in oil. Vvhen destined for
39S TREATISE ON VARNISHES.
oil, ft is ground with drying or pure nut oil added to
essence, and mixed up with drying oil*
Chamois colour. Biiff" colour.
Yellow is the foundation of chamois colour, which is-
modified by a particle of red oxide of lead (minium),
or what is still better, red sulphurated oxide of mercury
(cinnabar) and ceruse in small quantity. This colour
may be employed in distemper, in varnish, and in oil.
For varnish, it is ground with one half common oil of
pinks, and one half of the varnish No. 1 3. It is mixed '
up with the varnish No. 14. For oil painting, it is
ground, and mixed up with the drying oil destined
for it.
Olive colouré
Olive colour is a compovsition, the shades of which
may also be diversified. If black and a little blue be
mixed with yellow, you will have olive-colour. Yellow
de Berri, or of Auvergne, with a little verdigris and char-
coal form this colour. It is proper for oil and for varnish.
When destined for distemper, it will be necessary to
make a change in the composition. The yellow above
mentioned, indigo and ceruse, or Spanish white, are
the new ingredients which must be employed.
It is ground, and mixed up with the varnishes Nos. 1 3.
and 14. For oil painting, it is ground wiih oil added
to essence, and mixed up with drying oil,
BLUE.
Blue belongs to the order of vegetable substr^nces,
like indigo; or to that of-mctaiUc substance.-?, like
COMPOSITION OF COLOURS. 399
prussiate of iron (Prussian blue) ; or to that of stony
mineral substances, as ultramarine ; or to that of vitre-
ous substances coloured by a metallic oxide, as Saxon
blue. Ultramarine, in consequence of its high price,
is more particularly reserved for pictures. Saxon blue
even participates in some degree in this prerogative.
When prussiate of iron or indigo has been employ-
:'d without mixture, the colour produced is too dark.
It has no splendour, and very often the light even makes
it appear black : it is, therefore, usual to soften it with
white.
As much ceruse as may be thought necessary for
the whole of the intended work is ground with water,
if for distemper ; and w^ith oil, if for \'arnish made
with essence, or merely \vith essence, which is equally
proper for oil painting ; and a quantity of either of these
blues sufficient to produce the required tone is added.
For varnish, the ceruse is generally ground with oil
of pinks added to a little essence, and is mixed up with
the varnish No. 1 2. if the colour is destined for delicate
objects, or with the varnish No. 14. if for wainscoting.
This colour, when ground, and mixed up with drying
oil, produces a fine effect, if covered by a solid varnish
made with alcohol or essence.
In the last place, if this oil colour be destined for ex-
pensive articles, such as valuable furniture subject to
friction, it may be glazed w-ith the copai essence var-
nish No. 18. or that of No. 22.
This colour produces very little effect in distemper,
because it is not very favourable to the play of the
light : but it soon acquires brilliancy and splendour be-
400 TREATISE ON VARNISHES.
neath the vitreous lamina of the varnish. Painting m
distemper, when carefully varnished, produces a line
effect.
All painters do not place the same degree of confi-
dence in prussiate of iron, because they are well ac-»
quainted with the instability in the tone of that colour,
which passes to green more or less speedily. It is pro-
bable that the colouring parts sought for in lead and in
bismuth, and which are frequently employed to lessen
the intensity of the blue, contribute to produce thijj
change. These colours acquire from the light a yel-
low tint, which reacts on the blue of the prussiate, and
forms with it a compound colours the result of which
•must be a green, more or less decided. The oil may
cooperate towards this effect.
According to this principle, therefore, which I think
wdl founded, every intermediate colouring part capa •
ble of obviating this change of tint, in a manner more
or less complete, must concur towards the preservation
of the original colour of the prussiate of iron. Some
painters employ with success umber earth and a particle
of red oxide of mercury (vermilion) to fix the white of
the white oxide of lead, and to prevent it from passing
so easily to yellow. Blacks produce the same efi'cct,
and especially the black from vine twigs, which com-
bines perfectly with the colour of Prussian blue. AVe
are even assured that this mixture, m-ade in proj)or-
tlons regulated by experience, exhibits under the liand
of the p:iinter a brighter and more brilliant tone, whiclij
after the lapse of several years rivals^ in sonic measureJ
the blue of ultramarine.
i
COMPOSITION OF COLOURS. 401
It IS well known that a mixture of prussiate of iron
and the black of vine twigs exhibits, under the muUer,
a colour inclining to violet. It then assumes a yellow*
ish tint, which gradually decreases, and which disap-
pears at the end of three or four years to assume a
very rich and very durable blue tone.
This mixture answers the same end in house-paint-
ing. The pearl gray assumes an azury tint, which
maintains itself, and which prevents the ceruse from
inclining to yellow.
Another blue made with Saxon blue,
Saxon blue, a vitreous matter coloured by oxide of
Cobalt, gives a tone of colour different from that of the
prussiate of iron and of indigo. It is employed for sky
blues. The case is the same with blue verditer, a pre-
paration made from oxide of copper and lime. Both
these blues stand well in distemper, in varnish, and in
oil.
The first requires to be ground with drying oil, and
to be mixed with the varnish No. 14. If intended for
oil painting, it is mixed up v*'ith the resinous drying
oil p. 101, which gives body to this vitreous matter.
The blue verditer may be ground with the varnish.
No. 1 . added to a little essence j and may be mixed up
.with the varnish No. 3. if the colour is to be applied to
delicate articles. Or the varnish No. 1 3. added to a little
drying oil may be used for grinding ; and the varnish
No. 14. for mixing up, if the paint is destined for
•ceilings, wainscoting, or other objects of the like kind,
-This colour is sok and dull, and requires a varnish
2d
402 TREATISE ON VARNISHES.
that may heighten the tone of it, and give it pJay.
No. 18. is proper for this purpose, if the article has
need of a durable varnish.
GREEN COLOUR AND ITS COMPOUNDS.
Sea green.
Every green colour, simple or compounded, whe»
mixed up with a white ground, becomes soft, and
gives a sea green, of greater or less strength, and more
or less delicate, in the ratio of the respective quantises
of the principal colours. Thus, green oxides of copper,
such as mountain green, verdigris, dry crystallized
acetite of copper, green composed with blue verditer,
and the Dutch pink of Troves, or any other yellow,
will form, with a base of a white colour, a sea green,
the intensity of which may be easily changed or modi-
fied. The white ground for painting in distemper is
generally composed of Bougival white (white marl),
or white of Troyes (chalk), or Spanish white (pure
clay) ; but for varnish or oil painting it is sought for
in a metallic oxide. In tliis case, ceruse or pure white
oxide of lead is employed.
Sea- green for distemper^
Grind separately with water mountain' green and
ceriise ; and mix up with parchment size and water,
adding ceruse in sufficient quantity to produce ihQ
degree of intensity required in the colour. Watiiii, an
excellent judge in every -thing that relates' to sure and
(udicious practice, r'econimends the use of Dutch pink
.COMPOSITION OF COLOURS. 403
of Troyes and white oxide of lead, in proportions
pointed out by experience ; because the colour thence
resulting is more durable.
In the case of a triple composition, you must begin
tso make the green by mixing Dutch pink with blue
verditer, and then lower the colour to sea green by the
addition of ceruse ground with water.
«Sea green for varnish.
Varnish requires that this colour should possess more
body than it has iii distemper ; and this it acquires from
the oil which is mixed with it. This addition even
gives it more splendour. Besides, a green of a metallic
nature is substituted for the green of the Dutch pink,
which is of a vegetable nature.
A certain quantity of verdigris, pounded and sifted
through a silk sieve, is ground separately with nut oil,
half drying and half fat ; and if the colour is destined
for metallic surfaces, it must be diluted with the var-
nish No. 12. or with No. 14.
On the other hand, the ceruse is ground with essence,
or with oil to which ons half of essence has been
added ; "and the two colours are mixed in proportions
relative to the degree of intensity intended to be given
to the mixture. It may readily be conceived that the
principal part of this composition consists of ceruse.
' If this colour be destined for articles of a certain value,
■ acetite of copper (crystallized vardigris), dried and
pulverized, ought to be substituted for verdigris, and
the painting must be covered with a stratum of the
transparent copal varnish No. 18., or that of No.' 22,
2 D 2
404» TREATISE ON VARNISHES.
The sea greens which admit into their composition
metallic colouring parts are durable, and do not
change.
The last compositions may be employed for sea
green in oil painting : but it will be proper to brighten
the tone a little more than when varnish is used ; be-
cause this colour becomes darker by the addition of
yellow, which the oil develops in the course of time.
Green colour for doors, shutters, iron or ivooden rail'
ing, palisades, balustrades, and for all articles ex-
posed to the air.
A green colour is, in general, agreeable to the eye; for
nature seems to have adapted the particular organiza-
tion of that organ to the daily impression of this co-
lour, which is in greater ^quest than any other. Green
and blue form separate tones, the harmony of which
sympathizes best with the sensations excited through
the eye. Green is the colour destined for the fields ;
and hence the preference given to it to harmonize with
ntiture in the decoration of gardens and walks.
Ceruse is stili the principal base of this colour. When
it is required to bring it to the tone most agreeable,
grind \v'ith nut oil two parts of ceruse, and with es-
sence of turpentine one part of verdigris. Then mix
up the trvvo colours with one half common drying nut 1
oil and one half revsinous drying nut oi! (p. 101). This
xroîour appears at first, to be a pale blue ; but the im-
pression of the light soon makes it pass to green, and
m this state it is very durable.
Watin deserves, Ûut the doses of the ceruse ought
COMPOSITION OF COLOURS, 405
to be carried to a third more, when the colour is de-
stined to be employed in the centre of large cities, such
as Paris : without this precaution it acquires a gloomy
tone, which leads to a blackish green. There can be
no doubt that this effect arises from the thick atmo-
sphere, and the exhalations which vitiate the air in large
cities. Ceruse in such places soon acquires a yellow
tint, which contributes to give to the cupreous oxide a
darker and more gloomy light. In these particular
cases, white ought to be preferred to yellow, as the
ground to a green colour. The custom among painters
is to make the first coating yellow.
Compound colours fo?' rooins.
Compound colours may be employed in distemper,
or with varnish, and they wi^be more durable the less
œconomy has been consulted in making choice of the
materials, and if ceruse has been preferred to Spanish
wjiite or to chalk. In general, colours destined for
varnish or for oil require a metallic white,
Comhound s:reen,
t o
For this colour, take two pounds of ceruse, four
ounces of Dutch pink of Troyes, and an ounce of the
prussiate of iron (Prussian blue) or indigo. This mix-
ture produces a green, the intensity of which may be
increased or diminished by the addition of yellow or
blue, You must grind with oil to which a fourth part
of essence has been added, and mix up with the varnish
No. 1 2. or that of No. 1 4. Both these contribute to
the durability of the colour. If you are desirous of de^
2d 3
406 ;. . TREATISE ON VARNISHES^
sft^oyingi'tiie smell of the essence^ forni a glazing with
■Ûie .vîîrnîsh Nos. 1 . or 3. or with that of No. 6.
Crhen colour for articles exposed to friction and hloivsy
such as the tvheels of carriages, &c.
The great wear to which carriages are exposed by
friction and continual washing, requires that a durable
varnish should be employed when they are painted.
Whatever care may be taken by coachmen, it is im-,
possible that continual rubbing with a sponge, which
becomes filled with earthy parts, should not produce
an alteration in the best varnish. To render the work
^oiid, you must first apply a ground composed of boil-
ed linseed oil, ceruse previously dried over a pretty
strong fire, to make it lose the white, and a little sul-
phate of zinc (white vitriol), in a dose of a quarter of
an ounce to each pound of matter. The second stra-
tum must be composed of the preceding green colour,
that is to say, two parts of ceruse and one part of verr
digris pulverized and ground with boiled nut oil, added
to a fourth part of fat oil of pinks, and mixed up with
drying oil. The third stratum consists of the same co-
lour, mixed up with the fat copal varnish No. 21. o^
that of No. 22.
Red colour for the bodies of carriages, coach wheels.
Artists differ in regard to the composition of the first
strata. Watin recommends red de Berri (a kind of
argillaceous ochre) mixed with vitreous oxide of lead
(litharge). Others prefer red o^ide of lead (minium).
COMPOSITION OF COLOURS. . ^407
Colours which have for basis a metallic wSéîde -^e '^- .
always pretty durable. You may even grind \V4% pu^ J \
linseed oil or nut oil, which have not been freedjfemx^
their greasy particles. Oxygen (the base of pure air);"
the union of which with a metallic base constitutes an
oxide, does not fail, in this case, to exercise an action
on the state of the oil, which soon acquires the quali-
ties of drying oil. This effect may also be hastened by
the mixture of a little sulphate of zmc (white vitriol)
ground with the colour.
As this condition of the presence of oxygen is found
in the red de Berri, and in red lead, either of these two
substances may be employed, as the artist or amateur
fmds most convenient. The cheapest, however, will
always be preferred. I should, therefore, take one of
these two bases for the first stratum, adding a little li-
tharge ground on porphyry, if red de Berri be used ;
I should grind with oil half fat and half drying, and
mix up with drying oil. The second stratum should
be red oxide of lead ground with drying oil, added to
one half of essence. The third ought to be composed
in the same manner, but with red sulphurated oxide of
mercury (vermilion, cinnabar). In the last place, I would
glaze the whole with the fat copal varnish No, 23., or
that of Noi 22., heightened with a little vermilion, and
would hasten, the desiccation of the varnish by exposure
to the sun or to a strong current of air.
The red is often prepared, from motives of cecoao-
\Xi\\ with red oxide of lead, without vennilion.
2d4
408 TREATISE ON VARNISHES.
Red for buffets.
Varnish with vermilion is not confined merely to
the wheels and bodies of carriages ; it often forms the
ground ; and in this case it ought to be treated in the
same manner. It requires, however, a little more la-
bour. After the first stratum is applied it is rubbed
with pumice stone ; the varnish is then laid on at se-
veral times and polished. This operation will be no-
ticed hereafter. The same colour is employed also for
internal articles of luxury. It contributes likewise to
the decoration of buffets. Grind with boiled oil, added
to essence, red oxide of lead, and mix up with the
varnish No. 14. The second stratum is formed of
vermilion, heightened with a particle of Naples yellow.
Then apply a third stratum of the varnish of the second,
little charged ^vith vermilion. This varnish is very
durable. It belongs to the genus of those which are
susceptible of a fine polish. If you are desirous that
the odour should be speedily dissipated, glaze with ^
varnish of the second genus ; but it is less dm-able,
MIXED REDS.
Bris: lit red.
A mixture of lake with vermilion gives that beauti-
ful bright red which painters employ for the sanguine
parts. This red is sornetimes imitated for varnishing
small appendages of the toilette. It ought to be ground
with varnish and mixed up with the same, after which
it is glazed and polished. The varnish No. 13. is used
COMPOSITION OF COLOURS. 403
for grinding ; No. 14. for mixing up, and No. 12. or
22, for glazing.
Crimson, Rose colour.
Garminated lake, that which is composed of alurmne
(the base of alum), charged with the colouring part of
cochineal, ceruse, and carmine, forms a beautiful crim-
ison. It requires a particle of vermilion and of white
oxide of lead (white lead). The dearness of these two
.colours confines the use of this varnish to valuable
articles.
Piolet colour,
Violet is made indifferently with red and black, or
red and blue; and to render it more splendid, with red,
white and blue. To compose violet, therefore, appli^
cable to varnish, take minium, or, what is still better,
vermilion, and grind it with the varnish No. 12., to
which a fourth part of boiled oil and a little ceruse have
been added : then add a little prussiate of iron (Prus-
sian blue) ground in oil. The proportions requisite
for the degree of intensity to be given to the colour
will soon be found by experience. The white brightens
the tint. The vermilion and Prussian blue, separate or
mixed, give hard tones, which must be softened by an
intermediate substance, that modifies to their advantage
the reflections of the light,
Chçsnut colour.
This colour is composed of red, yellow, and black.
The English red, or red ochre of Auvergne, ochre de
yue, and a little black, form a dark chesnut colour. This
composition is proper for painting of every kind. If
4I6r TRUATISS ON VARNISHED.
English fedj whreh is drier than that of Aurergne, b'ë
employed, it will be proper, when the colour- is de-^
stined for -varnish, to- grind it with dicing nut oil. The
©dire cf Auvergne may be ground with the varnish
Ko. IS., zné mixed up wkh that of No. 14.
The most experienced artists grind dark cipiours with
KBseed oil whea the situation will- adniit of its being
/Ssed j because it is more dr)àng. For articles without
4oaré, nut oil is preferable. The colours of oak wood,
wahiut tree, chesnut, olive, and yellow, require the
application of a method recommended by its success,
k h c^én custcMTiaiy to add. to the above ingredients a
EttSe litharge, ground on porphyry : it hastenj. the de»
siocation of the Goloin*, and gives it "body."
But if it is intended to cover thesse colours with \^r-
msh, as is generally practised in regard to wainscotmg,
thev must bemixed up with essence to v/hich a little oil
iïâ&been added. The colotn- is then much better disposed
to- receive the varnish ; imder which i* exhibits ail the
spfendo.ur it can derive from the refection of the light.
This method has, no doubt, a manifest advantage in
the hand" of an artist who knows how to manage the
application of the colour, and to give it a proper and
■ssîiform thickness, especially in the nrst stratum. This
process, hov/ever, in regard to its complete success,
depends so much on the hand and conception of the
"irtist, that Î v\-ill venture to. assert, that the method I
lïave frequently recommended of mixing up the co-
lours Vvith \"cirDi;>h, has often equalled in its effects, aft^"
application," those of the forinei\ It appears even to h^^
$i>msydba-t tpefter suited to the inexperience of ~a youns;
COMPOSITION OF COLOURS. 411
artist. Mixing up with essence, indeed, is not free
from ineonveniences, when the pîdnt is applied to white
wood. I have seen several of these compositions fall
off in scales, in consequence either of the iirst stratum
having been applied too thick, or without care, or of
simple earths having been substituted for metallic ox-
ides. The inconvenience, however, apprehended in
the application of colours mixed up with varnish may
be obviated by putting only a small quantity of colour
into the last coating of varnish, to facilitate the beauti-
ful reflection of the light from the coloured ground, or
by suppressing it entirely. The varnishes which I have.
appHed in this manner all stand the strongest blows,
even with a hammer, without scaling off.: they are
both brilliant and durable.
By confining ourselves to the number of colours
here mentioned, it may readily be conceived that we
are far from the hmits fixed by the different gradations
or degradations of the distinct tones, modified tints, or
simple shades, which would result from. the variety
that might be admitted in the distribution of the same
colouring substances. The artist and amateur will, in
this respect, foresee all the resources of the art. An
examination of the determinate colours was sufficient to
give a view of the means which nature puts into the
hands of the colourist and painter to gratify the taste
or the caprices of the opulent. .
C ^12 3
CHAPTER m,
i/f the exie?ti which may le given to the use of the iurpeyitnie
€opal varnishes Nos. 18. and 22. by impregnating them
. 7iit h various solid colouring parts, transparent afid proper
Jor answering the purpose of glazing on metallic laminœ,
smooth or ornamented; Jhr Imitating transparent enamel y
ùndfor repairing those accidents which frequently happen
to enamelled articles.
Residing in a manufacturing city, where the arts of
enamelling and of painting in enamel have been carried
to a degree of perfection hardly to be met with but in
Geneva, I have often witnessed the trouble, expense,
©fetacles, success, and uncommon activity which al-
ways accompany the first enterprises among a people
who, in point of skill and industry, approach nearer
than any other to the most industrious nations.
The case with painting in enamel is not the same as
with that which adds to the value of porcelain. The
yariety of the toys to which it is applied, their delicate
forms,, and the différence in the metallic alloys, require
modifications in the composition of the colours, and in
that of the fluxes. These modifications, the necessity
çf which vis sufficiently shown by the accidents that
happen, both m manufacturing and when out of the
hands of the workman, to enamelled articles, cannot
be ascertained at the moment ; and there is no certain
guide to direct the artist in his researches. No work
but that of Montami, which is destitute of method, in-»
, 1REPAIRING ENAMEL. ' 413
complete, and actually useless in the present state of
the art, was v/orthy of the confidence of the enamel
painter in his operations. Unacquainted, therefore,
with the theory in regard to the nature of colours ex-
tracted from mineral substances, and to their degree of
vitrescibility, a.nd being under the necessity of rivaling,
with success, discoveries which some adventurers, m
consequence of a little more applicadon or industry, or
perhaps çf a little more good fortune, were enabled to
make, his attempts were always hazardous. An an.
thus created, in the course of two years, notwithstand-
ing the impediments which must have resulted from
the secrecy observed by workmen in the same branch
of business, is one of the most singular phsenomena
which characterize the industry of Geneva, and the
particular genius of the artists of that city.
Were the manufactory of Geneva removed to a city
of the first class, such as Paris, and placed in some
measure under the eye of a powerful government,
where all the means of encouragement seem to be con-
centrated, and where the secrets of the workshop iniist:
bow under the influence of learned sociedes and artists^-
the destitute state in wliich the art of the enaraeller of
toys is at present, in regard to a general theory appli-
cable to all the valuable materials employed, would
be soon observed ; and this interesdng part of a new
branch of industry would, no doubt, find the same
protection as the manufactory of porcelain has done*
It needs excite no astonish ment that the art of ena^
melling, such as it is practised among us^ where the
artists live insulated, v/ithout any communicalion
414- TIUÎATISE ON VARNISHES»
which might be of advantage to them, should, notwith*
standing its success, be still deprived of those principles
which could alone ensure its progress, and preserve to
posterity those discoveries which by the instability of
fashion may be lost. Nor can it appear wonderful that
the finest master-pieces in enamel-painting, as they are
so frequently subject to serious accidents, should be en-
tirely deprived of their value, if no means can be found
to repair such of these accidents as can be repaired
without fire.
Toys, when once they have gone from the hands of
the artist, are no longer susceptible of being renewed ;
but means have been found to repair with cements,
which assume the solidity of a "vâtreous body, and
which are afterwards painted and covered by a colour-
ed varnish, the defects occasioned by small fragTuents
being detached from certain opake compositions. In
transparent enamel this reparation is more difficult. The
tint of the varnish must correspond with that of the
vitrified coating ; it must possess the same splendour,
and its solidity should be equal to that of the enamel
itself. This may be accompHshed by the ethereous
copal varnish No* 17., and by tli ose of Nos. 18. and
22. By introducing into the ialter varnishes colours
iwhich by their tints imitate those extracted by vitrifi-
cation from -metallic substances, all the conditions re-
quired in the reparation of the dilierent accidents that
happen to enariiel are answered j and at the same time
anevv' art is ci'êated, which I have had the happiness to
see realised.
. Sim^e copal var^ilsli, or that iaade with turpentine,
I
. -REPAIRING ENAM£L, 415
has an ambery colour, which disappears when it has
been applied. The oily substance, by contributing ta
: ts solidity, renders it at the same time very proper for
becoming charged, much better dian alcoholic T-^ar-
nishes, with certain vegetable resinous colounng bodies,
by means of which the artist can, in a certain degreej,
imitate those colours which produce so beautiful am
«ffect in transparent enamels. It may be readily con-
ceived, that to preserve to these varnishes this (trans-
parency, which gives them a resemblance to enamd,,
nothing must be employed but resinous or saline mat-
ters, entirely soluble in essence. It was in this manner
I prepared the colours applied to the lid of the ivory
box I presented to the Society of Geneva as a specimea
of the new manufacture in coloured varnislies imitating
enamel ; and for which I was indebted to the gratitude
of a countrvinan, for whom I had prepared the ym-
mstL
The varnish which serves as a glazing*, and whic%
is susceptible of a fine polish, resists better th^m the
vitreous flux of enamels, the friction of keys, boxes,
and other articles very often carried in the pockets-
The daily use made of this box for twelve years, has
destrc^'-ed the metallic ring which served it as an oin^^
?nent, but without injuring; the varnish,
* To glaze, in the language of painting, expresses tlie appHica-"
iîon of a stratum of transparent matters on a coloured groimd in
siich a manner tliat-the colour of t4iis ground becomes more appac
rent, more brilliant, pr ligliter. To glaze, therefore, is to applj'. a
•colour %vliich has little body, or a transparent tint ivhicii suiFexs tbe
grcuiid" on which it k placed to be seen.
4T& TREATISE ON VARNISHES,
Mr. Chaporiier, the artist who found means to make
SCT successful an application of copal varnish, according
to my process, quitted Geneva, his native country,
some time after he had been employed on this nev/ art.
His success has induced me to devote this chapter to
the coloration of this varnish,
Traiisparent green colour.
Artists are often embarrassed m regard to the choice
ef colouring matters, when they are desirous of com-
municating a colour to a liquid without injuring its
transparency. Some colouring parts are susceptible of
being transmittted to alcohol, or even to \A'ater, but
refuse to unite with oily substances. Cupreous prepa-
rations, in the saline state, are of this nature ; while
cupreous oxides (calces of copper) resist the action of
water, and pass into oily liquors. Other colours re-
quire mordants of an acid or alkaline nature before they
5ecome disposed to pass into water, and refuse every
kind of union with oils. Indigo, litmus, cochineal,
saffron, bastard saffron, and red sandal wood, prove
the truth of this principle, which experience has in'
duced me to admit.
This" variety in the chemical properties of colouring
substances seems to confine the application of some of
them to certain vehicles and to certain circumstances, in
order to render them useful in the arts. I have often
experienced difficulties when, on the faith of authors
Vi-ho have written on this subject, I endeavoured to give
to copal varnish made with turpentine all the colours-
susceptible of producing a rich effect in painting, with*
REPAIRING ENAMEL. 41?
out altering the transparency of the coloured Vehicle.
It must, however, be allowed that the state of the body-
employed in these trials is not always what it might
and ought to be, if taken from the order of saline sub-
stances. One example will be sufficient to show the
truth of this observation.
I mixed acetite of copper (crystallized vetdigris) f e^
duced to powder, with copal varnish, to communicate
to it a transparent green colour. The union t<rhich I
attempted was favoufed by the heat of a balneum
marine. At the moment of the mixture a part of thé
copal assumed the form of grains ; but by the addition
of a little turpentine, the temperature of the bath, and
motion, the varnish was at length restored.
In my opinion, this separation of a part of the copal
was owing to the presence of the moisture contained in
the pulverized crystals ; for, having repeated the same
experiment with pulverized acetite of copper, perfectly
dry, projecting the powder in small portions into the
hot varnish, it tvas attended with complete Success. Thé
colour resulting from this mixture was - a beautiful
greefi. It was mellow, and abundant in colouring mat-
ter, since one coating of it, extended over a metallic
plate, produced undeï* this colour a reflection of light
of a veïy rich and agreeable tone.
^Another green colour.
The green oxide of coppel', obtained by precipitating
with Hquid carbonate of potash (potash) a solution of
copper in any acid, if washed and dried, and then
mixed with copal vamislt, gi\tss a beautifiil green co--
418
TREATISE ON VARNISHES.
lour. It is inferior, however, to the preceding com-
position.
Another green colour luj composition.
This green may serve as an illustration of the theory
of compound colours. The mixture of two simple co»
lours produces a compound colour, the more or less
decisive tint of which depends on the respective quan-
tities employed. The varnish coloured by terra mérita
or gum guttœ. Nos. 15. and 16., mixed with the fol-
lowing varnish coloured by pure prussiate of iron, is.
more beautiful, smoother, and more extensible than
the green formed by acetite and by precipitated green
oxide of copper.
Blue colour.
If indigo could incorporate with copal varnish, and
communicate to it its colour, we should not be obliged
to search for this colour in a substance which alters its
limpidity, and which renders it coloured only in con-
sequence of the great division of its parts. Prussiats
of iron (Prussian blue) serves as the basis of this co-
lour.
The Prussian blue of the shops, when of the first .
quality, communicates to our varnish a very transpa-
rent blue colour ; but it has not that richness of reflec-
tion and velvety appearance which renders it agreeable
to the eye when that extension which it can bear with-
out being weakened has been given to it. When ex- .
tended over a metallic plate, there are even observed
in it grains, which one is tempted to ascribe to the .
REPAIRING ENAMEL. 419
effect of incomplete division, or to the separation of
some earthy matter, which almost always accompanies
the best prussiate of the shops.
At the time of my researches in regard to this colour,
I had in my possession a prussiate, which I had made in
the experiments repeated during the course of my lec-
tures, and which was absolutely free from any mixture
of alumine (the basis of alum). I employed it for the
coloration of varnish, and the trial was attended with
complete success. In a word, this blue, when in a
state of purity, unites so completely with copal varnish
that its transparency does not seem to be in the least
affected by it*.
* It is not necessary that artists should make prussiate of iron
in order to obtain it pure 3 any one possessed of common intelli-
gence may easily separate from that of tl e shops the alumine or
argillaceous base arising frorn the decomposition of the alum em-
ployed in the preparation of it. Pulverize the blue^ and put it into
a glass or porcelain vessel with a mixtui-e of water and muriatic
acid (marine acid) ; a very strong effervescence will take place.
When the effervescence has subsided, pour in a new quantity of
acid: if no effervescence ensues, it will be sufficient to add to the
liquor of the prussiate a very small portion of acid. Then leave
the mixture for twenty-four hours, and at tlie end of that period
decant the clear liquid. "Wash the sediment with boiling water ;
and having poured the whole on a paper filter, tlirow water on the
filter till it becomes insipid. Then dry the blue remaining on the
filter, and divide it under the muller. The quantit)' will be les-
sened 5 but the intensity of the colour will be much greater. After
tliis process the prussiate may be considered as free from mixture j
and this is the state in which it ought to be for the present pur-
pose.
- 2 E 2
420 TREATISE ON VAPn.NISHÉS.
Superb liquid bhie.
Circumstances sometimes occur to authorize the ap-
plication of copal varnish to a colour vv'hich may havj
been mixed up with a gummy or mucilaginous liquid.
These circumstances are favoured by the accidents
which happen to enamel. Opake enamels are able to
support the impression resulting from the direct appli-
cation of a mineral acid to a metallic plate ; and in
lilce manner, transparent enamels, applied to gold and
silver, can admit for their reparation coloui-s, the mor-
dant of which may be taken from the order of mineral
acids, attention being however paid to their particular
affinities. In regard to metals, the texture of which
is inferior to that of gold or silver, colours with a mor-
dant can be applied only by means of a gummy juice
capable of defending the metallic plate from the contact
of the mordant. The colour, the composition of which
I am about to describe, as well as that from indigo,
which I shall speak of hereafter, belongs to those which
require this preliminary precaution. I made a trial of
it about thirty years ago with a celebrated draftsman^
known by his zeal and superior talents, which he de-
voted to the honour of his country, Geneva ; for it
was to the advice of Soubcyran, and the confidence
placed in him by government, that we are indebted for
the establishment of the drawing-school entrusted at
present to the particular direction of the Society of
Arts, which has added to it a school for modelling an^
an academy. The above ardst applied this blue- to fan-
REPAIRING ENAM£L. 421
•painting, &c., and set the highest value on it. The
composition of it is as follows :
Put into a small matrass or common phial an ounce
of fine prussiate of iron (Prussian blue) reduced to
powder, and pour over it from an ounce and a half to
two ounces of concentrated muriatic acid (fuming ma-
rine acid). The mixture produces an effervescence,
and the prussiate soon assumes the consistence of thin
paste. Leave it in this state for twenty-four hours ;
then dilute it with eight or nine ounces of water, and
preserve the colour, thus diluted, in a bottle well
stopped.
The intensity of this colour, which is very dark, may
be lessened, if necessary, by new doses of water. If
the whole of this mixture be poured into a pint of
'Iwrater*, it will still exhibit a colour sufficiently dark for
washing prints.
This colour charged with its mordant requires thé
use of gum water made with gum tragacanth. Muci-
lage of gum arabic does not possess sufficient consist-
ence.
This colour applied with gum water, and covered,
when dry, with copal varnish, would form very beau-
tiful foil
Yelloiv. •
Gum gutta: and terra mérita give very beautiful yel-
lows, and readily communicate their colour to copal
varnish made with turpentine. Aloes give a varied and
orange tint.
* The French piut is about an English qwt&t..
2 E 3
422 TREATISE ON VARNISHES.
Dark red.
Dragon's blood infused warm in varnish gives reds,
more or less dark, according to the quantity of the
colouring resin which combines with, the varnish. The
artist, therefore, has it in his power to vary the tones
at pleasure.
Though cochineal, in a state of division, gives to
essence very little colour in comparison of that which
it communicates to water, carmine may be introduced
into the composition of varnish coloured by dragon's
blood. The result will be a purple red, from which
various shades may be easily formed.
Violet.
A mixture of carminated varnish and dragon's blood,
added to that coloured by prussiate of iron, produces
violet.
I shall not give more examples of the communi-
cation of colours to copal varnish, as every person
habituated to the operations of this art, and every ama-
teur possessed of a certain share of dexterity, may rea-
dily find any tone of colour he desires. But, what is
of most importance to be considered in the reparation
of enamel, is the necessity of embracing the whole of
the subject exhibited by the painting, the injuries of
which are to be repaired, and of entering into the idea
of the artist by whom it was executed. This condi-
tion, which relates in an essendal manner to the sub-
ject, seems to require, for the reparation of it, the
hand by whom it was first painted.
REPAIRING ENAMEL. 42$
Observations.
The use of copal varnish cannot be confined to the
purposes already enumerated. Hitherto I have con-
sidered it as forming part of the province of the painter,
rather than that of the varnisher. This varnish is
called to another destination, which displays better its
properties and the extent of its utility. The reader,
from vi^hat has been already said, must be convinced
that, if carefully applied, it is capable of producing
great richness, splendour, and solidity, when extended
over surfaces which are themselves possessed of splen-
dour, as is the case with metallic substances. This
physical quality, observed in the latter, and the soli-
dity of their texture, render them proper for articles
subject to blows or to continual friction, and exposed
to the alterations occasioned by humidity. The appli-
cation of a varnish sufficiently solid to resist these dif-
ferent causes of alteration, and sufficiently transparent
to preserve and even to increase the original metallic
splendour, must add, in a considerable degree, to the
value of these articles. Mathematical, astronomical,
and philosophical instruments show, in an evident
manner, the advantages which they derive from similar
com,positions.
When the copal varnish is destined for small arti-
cles, as a particuiar distribution of the colours is not
required, it may be applied as well by an amateur
as by a professed varnisher. But if large articles
are to be varnished, the application of it requires
practice and great care.
2 E 4
424 TREATISE ON VARNISHES.
One of the essential conditions relates to the state of
the metallic surface. It must be well polished, that is
to say, better than in common. It must then be
heated on an iron plate placed over a chaffing-dish till
the hand can scarcely bear to touch it; and the heat
must be equally distributed to every part of it.
When this is done, dip in the varnish a large flat
brush, made of very soft hair, and draw it gently over
the whole article. This operation requires dexterity,
that the different strokes of the brush may not be ob-
served. It will, therefore, be proper not to load the
brush with too much varnish at once: if these precau-»
tions are neglected, the surface of the metal will ex-
hibit undulations, and very often it will be spotted.
Turned articles, if varnished while in the lathe by
means of heat, will always be attended with the greatest
success, because the extension of the varnish is more
uniform, and the operation facilitates the polishing.
When undulations are obser\Td, this defect may be, in
part, remedied by maldng the article approach the iron
plate without bringing it into actual contact. The distant
impression of the heat renders the varnish more uni-
form.
If a gold colour be required, two or three successive
strata of coloured and changing varnish may be ap-
plied; and these must be covered by a last stratum of
the uncoloured copal varnish. No. 18, The colour-
ing parts of the changing varnish of the third genus,^
No. 1. 5., may also be communicated to the copal var-
nish; or you may employ the new varnish, No. 22.,
Kiade with copal of one fusion.
REPAIRING ENAMEL. 425
Tf j^artlcular circumstances, determined by the nature
of the article intended to be varnished, prevent its
bdng heated, the varnish jnust be appHed cold ; but
the article may be brought near to the fire, or exposed
in ci stove, the heat of which disposes the varnish to
extend itself in a more uniform manner, and to appear
with its whole lustre. A bright sun and pure air pro-
duce the same eiFeçt.
If these kinds of varnigh becom? stained by use, the
article must be washed with tepid water, and wiped
with a piece of fine linen rag. The contact of hard
bodies is hurtful to them. If the case require it, 9.
little soap may be added to the warm water,
application of copal varnish to the reparation of
opahe euameL
The properties manifested by these varnishes, and
which render them proper for supplying the vitreous
and transparent coating of enamel, by a covering
equally brilHant, but more solid, and which adheres
to vitreous compositioas and to metaUic surfaces, ad-
mits of their being applied to other purposes besides
those here enumerated. By slight modifications they
may be used also for the reparation of opajve enamel
which has been fractured. These kinds of enamel
admit the use of cements colovnred throughout, or only
superficially, by copal varfiish charged with colouring
parts. On this account they must be attended with
less difficulty in the reparation than transparent enamel,
because they do not require the same reflection of the
light. Compositions of paste, therefore, the different
426 TREATISE ON VARNISHES.
grounds of which may always harmonize with the co-
lours or ground of the pieces to be repaired, and which
may be still strengthened by the same tint introduced
into the solid varnish, with which the articles are
f^lazed, will answer the views cf the artist in a won-
dcrful manner.
The base of the cement ought to be pure clay,
without colour, and exceedingly dry. If solidity he
required, ceruse is the only substance that can be sub-
stituted in its place. Drying oil of pinks will form an
excellent excipient, and the consistence of the cement
ought to be such that it can be easily extended by a
knife or spatula possessed of a moderate degree of
flexibility. This sort of paste soon dries. It has the
advantage also of presenting to the colours, applied to
it v/ith a brush, a kind of ground which contributes
to their solidity. The varnish No. 1,, of the first
genus, is exceedingly drying. The application of ir
will be proper in cases when speedy reparation of the
damaged articles is required.
In more urgent cases the paste may be composed
with ceruse and the copal varnish No. 18. or 22., which
dries more speedily than oil of pinks ; and the colours
may then be glazed with the ethereous copal varnish,
of the fourth genus. No. 17.
The implication of the paste will be necessary only
in cases when the accident, vv^hich has happened to
the" enamel, leaves too great a vacuity to be filled up
by several strata of coloured varnish. But in all cases
the varnish ought to be vvell dried, that it may acquire
its full lustre by polishing.
REPAIRmG.ENAr.îEL. 427
Though" it may be more convenient to apply the
paste, and then to colour it superficially by strata of
colours analogous to the subject, cases may occur in
■which a preference ought to be given to cements co-
loured throughout their whole substance; and though
any artist may easily determine the kind of matter
proper for the purpose, it will no doubt be of some
utility to give a short view of the colouring substances
recommended by experience.
rVhlie.
White oxide of lead, ceruse, Spanish white, white
clay. Such of these substances as are preferred ought
to be carefully dried. Ceruse and clays obstinately
retain a great deal of humidity, which would oppose
their adhesion to drying oil or to varnish. The cement
then crumbles under the fingers, and does not assume
a body.
Blach.
Lamp black, black made of burnt vine twigs, black
of peach stones. The lamp black must be carefully
.washed, and afterwards dried. Washing carries off a
great many of its impurities.
Yelloiu.
Yellow oxide of lead of Naples and Montpellier,
both of them reduced to impalpable powder. These
yellows are hurt by the contact of iron and steel: in
mixing them up, therefore, a horn spatula with a
-glass mortar and pestle must be employed.
Gum guttaj, yello^v ochre, or Dutch pink, accord-
428 TREATISE ON VARNISHES.
jng to the nature and tone of the colour to be imi-
tated.
Blue,
Indigo, prussiate of iron (Prussian blue), blue ver-
diter, and ulti-amarine. AU these substances must be
very much divided.
Green.
Verdigris, acetiie of copper (crystallized verdigris).
Compound green (a mixture of yellow and blue).
The first tv^^o require s. mixture of white in proper
proportions, from a iourth to two-thirds, according to
the tint intended to be given. The white used for this;
purpose is ceruse, or the white oxide of lead, or Spanish
white, which is less solid, or white of Moudon,
Red.
.Red sulphurated oxide of mercury (cinnabar ver-
milion). Red oxide of lead (minium). Different red
ochres, or Prussian reds, &c,
Purple,
Cochineal, carmine, and çarniinated lakes, with ce-
ruse and boiled oil.
Brick red,
Pragon*s blood. -
Chamois colour.
Dragon- s blood, with a paste composed of subli-
mated oxide of ïinc (flowers of jiinc), or, what is still
better, a little red sulphurated oxide of mercury (ver-
milion), .
REPAIRING ENAMEL. 429
Jlolet,
Red sulphurated cxide of mercury mixed with lamp
black, washed and very dry, or with the black of burnt
vine twigs ; and to render it mellower a proper mix-
ture of red, blue, and white.
Pearl gray.
White and. black; white and blue; for example,
ceruse and lamp black; ceruse and indigo.
Flaxen gray.
Ceruse, which forms the ground of the paste, mixed
with a small quantity of Cologne earth, as much Eng-
, lish red, or carminated lake, which is not so durable,
and a particle of prussiate of iron (Prussian blue).
Remarks.
It is well known that these mixtures \vill not admit
of any fixed rules, in regard to the quantity of the
matters which enter into their composition. They must
depend on the taste of the artist, and the tone he is
desirous of giving to the colour.
All these different methods seem to approach, more
I or less, to a kind of painting which maintains a very
lucrative braiich of manufacture, and gives employ-
ment to a number of hands. I here allude to the pre-
paration of foils, or coloured laminje, used with so
much success in the m^anufacturing of buttons, in em-
broidery, and for ornamenting a variety of toys, of
which there is a very extensive and daily consumption.
These ven- thin laminse of silver, copper, brass, or tin,
430. Treatise on varnishes*
perform the same office, under the name of foil, as
enamel covered with copal varnish, coloured or not
coloured, and which may be distinguished by the name
of false enamel. If the latter seems to differ from foil,
by the consistence, which depends on the thickness
given to the metallic laminae, and the successive appli-
cation of several strata of solid varnish ; if they differ
also by the body itself of the varnish, which does not
admit of those sauces which constitute the colouring,
part of foil, they seem to have some resemblance to
them by the nature of their composition, though it still
appears to be involved in myster}\ I, however, think
it my duty to lay before the reader the only infonna-
tion I have been able to procure in regard to the pre-
paration of foil, with a view of gratifj'ing those who
may be desirous to carry their researches further, and
to unite this branch to the art of varnishing, to which
it really belongs.
Foil.
The reader must here recollect, that certain colour-
ing parts of an extracto-gummy nature are more dis-
posed, by this circumstance alone, to pass into water
than into alcohol or into essential oils ; that other
colouring parts, such as those extracted from mineral
substances, experience only a great division, as is the
case with prussiate of iron, green oxides of copper, kc.
When the nature of the colouring parts which orna-
ment different kinds of foil is examined, it does not
always occur that they may be owing only to coloured
varnishes. In the course of my researches I think I
have observed, that some of these colouring parts
REPAIRING ENAMEL. . 431
belong to that kind of compositions distinguished by
the technical appellation of sauce, covered afterwards
with a transparent varnish, which preserves them from
the influence of moisture, and which concurs with the
metallic splendour to produce that beautiful effect with
which, in general, they are attended. The processes
can be varied, in regard to the tone and shades of the
colours, which may be easily rendered stronger or
weaker. Those which I here offer produced, in part,
the desired effect.
First preparation.
Immerse fish glue in pure spring water for twent)^-
four hours, and then expose it to the action of boiling,
water, to complete the solution of the gelatin (the base
of strong glue extracted from animal substances). Strain
the whole through a double piece of linen, or a piece
of flannel, and evaporate it in such a manner that the
solution of the gelatin shall form itself into a trembling
jelly; that is to say, not too thick when exposed in a
cellar for tv^o or three hours.
Second preparation.
Dip the polished metallic leaves of copper, brass,
or tin (the latter are employed only for gilt leather,
and for decorating papier mâché), which you wish to
colour, in water impregnated with a little nitric acid
(aquafortis), for example an eighth, a tenth, or a
twelfth of acid. This immersion renders the surface
of the metal rough. Then wipe it carefully at the
^
432 TREAtlSE ON VARNlsMfes.
moment, and having applied the glue suffer it to dry,
tliat it may then receive tlie colour.
Blue colour.
The beautiftd liquid blue, the composition of which
bas been given p. 420, may be employed for this
purpose. Leaves of silver or copper ought to be pre-
ferred to those of brass, when colours with a mordant
are applied. Any degree of intensity may be given to
this blue by the addition of common water.
Another blue,.
Take one part of Guatimala indigo, and put it into
a phial placed in hot sand, with two parts of common
sulphuric acid (oil of vitriol). When the effervescence
which takes place has subsided, add ten or twelve parts
of pure water. This kind of solution renders the blue
very beautiful. It is the composition of the Saxon
blue. The observations made in treating of the pre-
ceding blue, in regard to the nature of metallic laminse,
may be applied to this kind of colour. They ought to
be copper or silver»
Green.
A compound green may be made by mixing a de-
coction of yellow berries with a little blue liquor. It
may be prepared also by the immediate employment
of a solution of acetite of copper (crystallized verdi-
gris), such as that described under the head acetite of
copper. The sea green also may be imitated.
ï»REPARATION OF FOIL. 433
Red,
A dark red may be extracted from a decoction of
cochineal, the tint of which can be varied by means
of a large dose of water. This red inclines to purple.
The red of sandal wood may be extracted by alco-
hol, the evaporation of which will furnish' the means
of concentrating this colouring part. The colouring
part may be extracted also by water, which must after-
wards be evaporated, and the extract is then mixed
with alcohol.
A process nearly similar may be employed to apply
to foil the rose colour of bastard saffron. This colour-
ing part is soluble in carbonate of soda (crystals of
soda), as already seen, p. S60. It is precipitated from
the soda by means of the acid of lemon juice, which
seizes on the alkali. For the present operation this
colouring part is separated from the supernatant water
by means of some slips of cotton cloth, or cotton v/icks,
one end of which is immersed in the liquid, while the
other hangs over the edge of the vessel. All the water
is thus drawn off as if through a filter. The colouring
part is then mixed with alcohol, and spread over the
metallic surfaces in successive strata.
Violet,
Tincture of litmus, the colouring part of which
passes readily into water, produces a coarse violet. It
may be brightened by using alcohol, which acts on it
as well as v/ater. In the latter case, therefore, alcohol
is taken as the principle of solution.
2f
43é TREATISE ON VARNISH£S.
The colouring part of litmus is held in solution by
ammonia (volatile alkali) disengaged from urine by Éj
putrefaction. The colouring part which has passed '^'
into the water, in the case of an aqueous decoction, is i''.'
precipitated by the addition of a little acid of lemon :
it then collects itself at the bottom of the vessel. To
separate the supernatant water, the same kind of filtra- *
tion as that used for the decoction of bastard saffron
may be employed; or it may be removed by alcohol,
in which some drops of liquid carbonate of potash
(oil or solution of the salt of tartar) have been poured,
to brighten the colour and to change it to a beautiful
violet. Concentrated decoction of litmus, applied to
metallic laminEe, furnishes a speedier method of çolo^i
ration.
Lilac.
Tie up the litmus in a knot, and immerse it in water
till it give only a rose colour. Then boil it in a new
quantity of water, in which the remaining colour will
be concentrated, and apply this decoction cold to the
metallic laminse, prepared v/ith a solution of fish glue,
Ruhij colour.
Boil carmine or carminated lake in water ; and when
the decoction rises add some drops of ammonia (vola-
tile alkali). Suffer the liquor to form a deposit cold,
and employ it without filtration. A decoction of
cochineal, in my opinion, might be substituted for the
carmine or the lake.
Rose colour.
To make rose colour, add to the preceding a new
PREPARATION OF FOIL. 435
quantity of water, until it is brought to the tone re-
quired. Bastard saffron gives, in the gradation of its
colour, different shades of rose colour. A decoction of
Brasil wood, mixed with a solution of tin in nitric acid,
gives also tones of rose colour.
Ponceau. Poppy red.
Extend a stratum of the ruby colour, and over it
another of the tincture of oriental saffron, extracted
by maceration in cold water for forty-eight hours.
Capuchin colour, yellow and jonquil, might be
made in this manner, by gi^^ng stronger or w^eaker
doses of colour.
Prune colour^ and other browns.
A stratum of lilac colour, and over it a stratum of
green or blue.
Observations.
The second and third strata of colours ought not to
be applied till the preceding is perfectly dry. Care
must be taken also not to pass several times over the
same place, because the new' colour, though cold,
loosens the former. It is, therefore, always advan-
tageous to give to the colour a very dark tint; because
it saves the trouble of going too -oft over the same
surface.
These different tints of colours would not have the
durability obsei^ved in foil, and would be easily effaced
by the effects of rain or of fogs, were they not pre-
served by being covered with varnish. The varnishes
generally appropriated to articles of this kind are those
2f 2
èâét" 5-, TRÊAtrSê ON VARNISHES.
vyhichvjûômpose my first genus ; that is to sar, dn'îng
.xr'âmish'és made with alcohol. No. 1., 2., and 3., there-
fore, may be employed in such cases; and, for the
better preservation of the tints, the copal varnish
No. 1 8. or No. ?2., of the fourth genus, may be used.
At first It will emit some smell, but this may be re-
medied by a stratum of alcoholic varnish. Articles
of this îdnd do not require m,uch durability in the
varnish.
_>
C 437 2 ,0 ^ Ç.\
CHAPTER IV
N^ ^y
Precepts respecting tlw application of varnishes, coloured or
not coloured, which the artist or amateur ought always to
keep in rememhrance. Of the diff^erent kinds of painting.
Of varnished linen and silk.
The best composition of varnish, and the most exact
combinations in the colours, are not sufficient to call
them forth with all that splendour which it is possible
to give to them. An expert hand is required also for
the application of them ; and the amateur who has not
been accustomed to the labour must possess a correct
tast«.
The instruments which painters employ are simple,
and few in number. A smocth stone, a muller, a
spatula, a flexible knife to bring under the muller the
colours scattered over the grinding stone, or to remove
them; brushes large and small, and a few pots for
mixing up the colours, form the whole apparatus ne-
cessary for the amateur in the employment of varnishes
and colours.
The colours cannot be used in that state in which
they are purchased in the shops. They require to be
purified, ground, and mixed with the different liquors
which art employs to facilitate the extension of them
over the articles intended to be painted; and these
liquors must be different, according to the nature of
the colouring parts, and to the uses for which the
articles are destined: they are determined also by the
consistence which must be given to the composition/
2f 3
438 TREATISE ON VARNISHES.
It will therefore be necessary to offer a few obser\^ations
on this subject :
1st. The hard bodies are pulverizc4, and sifted
through ' a hair or silk sieve. This preliminary pre-
paration is applied to the different kinds of ochre,
chalk, clays, or boles; and to soHd substances, such
as white lead, litharge, verdigris, and cinnabar. This
operation prepares them for being more completely
divided under the muller, and facilitates the separation
of bits of straws, fragments of wood, or other foreign
bodies, which are often met with in some of the com-
mon colouring substances.
2d. When the colours are to be applied to painting
in distemper they are ground in water, that the lightest
particles may not escape, in consequence of the motion
excited by the muller. The ground matter is reduced
to the consistence of thin paste ; and when the muller
glides over the stone, without making any noise, and
when the trace it leaves on the colour is smooth and
without grains, it is judged that the operation has
brought it to the required state of division. ^
3d. Certain genera and species of varnish destined
for delicate articles, which are frequently expoâed to
carriage, as boxes, &c. and certain toys, such as fans,
boxes for holding counters, &c. do not admit in their
composition any matter capable of communicating to
them a strong smell, or which would render the de-
siccation of them slow. . In these pardcular cases the
varnishes of the iirst and second genera are to be pre-
ferred. The colours are then ground with the varnish
No. I., to which is added a spoonful or two of oil of
PRECEPTS RESPECTING VARNISH. 439
pinks to render it pliant; and the colours are mixed
lip with the same varnish. But, as it evaporates very
speedily, it requires to be employed immediately.
4th. Under some circumstances a more solid var-
nish than those of the first two genera is required for
mixing up certain colouring parts ; such, in particular,
as those extracted from the mineral kingdom, which
have a character of dryness that must be counteracted
or modified. The colours, in this case, are ground
with drying oil, to which a little fat oil has been added.
At other times the colours are mixed up with a var-
nish of the third genus, such as that of No. 14. ; or
of the fourth genus, as the copal varnish No. 18.
"When the dryness of the colour or drying quality is
not very great, it may be ground with the varnish
No. 13., and mixed up with that of No. 14., which
belongs to the fourth genus.
5th. There are other circumstances which require
greater solidity in the varnish, and which proscribe
every liquor or excipient not capable of concurring to
pronrote this essential quality. In this case the colours
are ground with drying oil, to which a little fat oil has
been added, if the colour contains a considerable quan-
tity of metallic oxide. If this oil renders the matter
too thick, a little essence is mixed with it j and it 'is
then diluted with the resinous di7ing oil, p. 120, or
with one of the fat varnishes of the fifth genus.
6th. One of the most essential points to be observed
in the preparation of the colour is, as already said, the
extreme division of its parts. Grinding in water is
speedily performed. This liquid, by its nature, easily
2f 4
440 TREATIGE ON VARNISHES.
loosens the aggregate moleculse of earthy substances.
The case is not the same when varnish^ essence, or
oil is employed. The experienced artist, who attends >'
to the gain arising from his labour, will readilv be sen- \
sible of the utility of this precept. Habit will soon
teach him, that a colour becomes truly profitable only
when it has been reduced to the utmost state of divi-
sion. He will not, therefore, consider the time which
he employs in the operation. But the amateur, who
lias not the advantage of experience, soon becomes
tired of the labour, which appears to him fatiguing :
he consequently gives way to impatience, or to the
ardent desire he has of realizing the effect of the in-
tended decoration. It will, therefore, be proper that
he should coolly consider the inconveniences which
result from precipitation, and frequently call to mind
.those precepts, founded on experience, which can alone
ensure success.
The great division of colours is one of the principal
causes of their beauty, and of the mellowness of their
tones. . The play of the light is then freer; it is pUrer,
and more disengaged from those pardal reflecdons
which in a granulated colour compose the coloured
reflected ray, the brightness and splendour of which
are then much altered.
7th. Three of our senses concur to determine the
essential point of this division, namely, the touch,
sight, and hearing. One may readily perceive that a
colour grinds more easily at the commejicement than
at tile end of the operation. The granulated paits roll
with greater fieedom under the inuUer than when they
PRECEPTS RESPECTING VARNÎSH. 44Ï
are more attenuated ; and the muller rises more easily
at the begiiining of the opei-ation than when it is nearly
finished. The air disseminated in the interstices of the
still coarse matter lessens and counteracts the force of
adhesion, which the weight of the atmosphere esta-
blishes between the muller and the grinding stone.
The liand which maintains -the circular motion may,
therefore, easily distinguish when the division of the
parts has attained to its utmost term.
The fineness of the parts may be soon observed by
the sight. The tr?xe of the muller shows the matter
smoother, and the colour is more and more developed ;
but if the eye is sufficient to perceive this physical
change, it is soon distinguished also by the ear.
At the commencement of the operation of grinding,
the rolling and friction of the parts of the matter and
of the instrument excite under it a kind of noise,
which gradually decreases, and v/hich is scarcely heard
towards the end. The absorption of the oily fluid,
which becomes greater as the division of the parts is
completed, requires the addition of more colour to
bring the mi^iture to a proper consistence. Care,
however, must be taken not to render it too liquid ;
because it would run on tlie stone and retai-d the tenn
of di\'ision, in consequence of the addition of a little
sohd matter vvhich would become necessary. A pretty
liquid consistence is less fatiguing, but the act of divi-
sion is somewhat retarded. - On the other hand it is
the more rapid as the consistence of the matter is
thicker: hence time is gained at the expense of a little
more fatigue, Tv/o or three trials v/iil soon indicate.
4
442 tREATISE ON VARNISHES.
the true consistence proper to be given to the mattef
to render the operation easy and expeditious.
8th. The perfection of this operation, and the spee-
diness of its execution, depend on the quantity of the
substance subjected, each time, to the action of the
muller. Those who might believe that the process
would be hastened by employing a great deal would
be much mistaken : -there is no fixed rule in regard to
this point. It depends on the extent of the stone, the
length and strength of the workman's arms, and con-
sequently on the greater or less restraint he may ex-
perience in keeping the muller in continual motion.
When heavy matters, such as those obtained from me-
tallic bodies, are ground, eight ounces at once will be
sufficient.
Gth. When the grinding is finished the matter is re-
moved with a flexible knife or spatula, and put into a
colour-pot. The same operation is repeated with new
doses of matter, till the whole quantity judged to be
necessary for the work is ground i^'ith the same care.
The colour is then diluted with the varnish or pre-
pared oil intended to be employed, giving' it the proper
consistence. This is what is called, according to the
technical tenri, vii.rhig up the colour. In this respect
extremes must be avoided ; a colour when too liquid
runs, and does not cover with sufficient exactness the
article which has been painted : if too thick it forms
lumps, can with difficulty be extended, occasions more
expense, disfigures the work, and fatigues the hand
which applies it. The colour on being taken from the
pet ouglit not to drop from the brush when tiu-ned'
PRECEPTS RESPECTING VARN'isH. 443
round two or three times in the hand, raising it obliquely
to check the thread which is formed.
Should the colour, during the operation of applying
it, assume too much consistence, a little more varnish
must be added, if it has been mixed up with varnish j
and essence of turpentine, if it has been made with the
latter or with oil. But if this consistence of the colour
arises from that of the varnish, it will be proper to
heat the alcohol or essence, before it is added to the
mixed up matter, in order to prevent the precipitation
of a part of the resin of which the varnish is composed.
10th. All matters destined for priming are ground
with water*, or with alcohol (spirit of wine), or with
essential oils, such as that of turpentine, or with fat
drying oils.
Colours ground with alcohol, and which are mixed
with varnish, must be employed immediately ; but the
great volatility of alcohol, and the rapidity with which
it evaporates, render this kind of process inconvenient.
On this account the varnish with which the colour is
to be mixed up is substituted in its stead ; and each
time that a new quantity of colour is put on the stone
a spoonful of drying nut oil is added, if the colour can
bear the slight change in the tint which results from
it ; or with the same quantity of oil of pinks, if the"
nature of the ground proscribes the use of every thing,
that might communicate a foreign tint.
11th. When colours are ground in essence, the.
artist ought to stand where there is a current of air, to
* This is the case in regard to distemper-^
t
44>4f TREATISE ON VARNlEjiES»
avoid the émanation of the essence, which sometime^
exercises^ an action on the nerves, when one is toQ
long exposed to it.
In other cases the colours must be ground with dry-
ing oils or with varnishes of the fifth genus, the con-
i^istence of which requires that they should be mixed
with a half or a third oi essence of tui'pentine. This
is the practice followed in regar4 to copal aiid amber
varnish, and in regard to ail colours destined for <M
painting.
12th. Each kind of varnish is reserved for uses
which, in some measure, limit or distinguish the cases
of its application. The clear, brilliant, delicate var-
nishes, which constitute the first genus, are not proper
for coloured grounds : they are too tender. Blows and
friction render them mealy. They may be applied with
more success to ardcles ornamented with cut paper,
and to furniture belonging to the toilette. Varnishes
which ihave somewhat more body, such as those of the
secoijd, third, and even the fourth genus, are much
better suited to the coloured grounds which cover wain-
scoting, ceilings, cornices, and all vv^orks sheltered from
tile influence of moisture and of rain. In the last
place, articles exposed to the open air and to the in-
clemency of the weather, or which are liable to shocks
or to friction, do not admit of secondly varnish. They
Tequire a consistence ajid solidity which is found only
131 fat varnishes and in oil colours.
13th. In all cases which -require the use of compound
Cclours, it will be proper to treat each of them sepa«
9
PRECEPTS RESFECTING VARNISH. 445
rately. When this labour is finished, the mixture can
be made with more precision,
14th. Painters employ two methods for famishing
apartments. Some apply the colouring substance in
distemper,— a process which will form the subject of the
following chapter, — and then cover it with as many
strata of varnish as the object may seem to require, with
or without colour. Others grind and mix up the
colour with varnish, w"hich in this case serves as a
vehicle.
To both these methods objections have been made.
The second appears to me to be accompanied with
some advantages not to be found in the first.
Distemper causes the wood to swell, and deposits
on it a kind of plaster, which the least percussion often
detaches in large scales. When this method is fol-
lowed, it will be necessary to leave such an interval
between the application of the distemper and that of
the varnish as may give the wood time to dry. If this
j precaution be neglected, which is almost always the
case, the varnish applied to this size penetrates into it,
if it has not been very strong : but it is prevented from
reaching the wood by the effect of the moisture con-
centrated in it, and which opposes every kind of union
with the resins that form the base of the varnishes.
The varnish then gives to the coloured stratum the
hardness of cement, which does not yield to the shrink-
ing experienced by the wood as it dries, and which
falls oflF in laminas, merely by the effect of desiccation.
These results, which are frequently ascribed to fraud,
attest only the ignorance of the painter, or the impâ?.
446 TREATISE ON VARNISHES.
tience of the amateur, who has beai too precipitate In
the application of his colours.
The c^sc is not the same with the second method,
especially if the varnish be applied when the wainscot-
ing is dry, and if the first stratum be employed very
clear, to dispose the wood to imbibe the varnish. The
successive strata of colour incorporate then with the
first, which adheres to the wood, and which, by these
means, secures it from the impression of the moisture
of the atmosphere. The last consideration ought not
to be neglected, in a country hke curs (Geneva), in-
tersected by a large lake and by rivers, exposed for
five months of the year to the influence of fogs, and
where fir wood only is employed for wainscoting. la
regard to the v^^ainscoting destined for lower halls ex-
posed to moisture, this precaution is carried still further,
by covering the back of it with oil painting made with
bole. The same practice is adopted with advantage for
the inside of the boxes of an orangery.
The mixture of colours with vrjiiish requires that
^ little colour only should be added to the varnish ap-
plied as the last stratum. There are even some cases
which require it to be absolutely colourless. It then
forms glazing, and its brilliancy is greater : the colour
also is more nervous.
All the reasons here given for preferring the second
method must be felt and appreciated by the amateur
desirous of giving to his compositions that soHdity of
which they are susceptible; but they have not the same
value in the eyes of the artist, who attends only to the
profit arising from his labour. The use of size pro-
PRECEPTS RESPECTING VARNISH. 447 —
duces a considerable saving of varnish, whicK is far
more expensive. Besides, the splendour which he is
able to give to this last stratum conceals the imperfec-
tion of an unequal coating of the colour, which how-
ever may possess some solidity, if it be applied in sum-
mer, and if care has been taken to allow the size suf-
ficient time to dry, so as to prevent the shrinking of
the wood. But this last condition does not accord with
the haste and dispatch which the painter employs in the
execution of such works.
One particular circumstance, however, seems to pro*
scribe the use of size : that is, when it is required to
spply varnish to new plaster. A solution of Flanders
glue in water, which ought not to be too strong, and
■which is applied warm, that it may penetrate the plas-
ter, is then used. But it v^ll be proper to leave the
plaster time to exhale all its moisture before it be
covered with the glue.
Another method, very favourable to the preserva-
tion of wood, and proved to be useful in checking the
eft'ects of moisture, is sometimes employed. It is to
prime the wood with ceruse, to which a sixteenth part
of the vitreous oxide of lead (litharge) has been added.
These oxides are ground with oil and one third of
essence. Colours in varnish, applied to this first stra-
tum, penetrate into the wood, and acquire splendour
and a mellow tone, together with consistence, when
the varnish is well chosen. I found this method to
answer exceedingly well.
15th. A careful artist, who wishes to give to his
4i^ TRKATISÉ ON VARNISHES. '
colours on^'ainscodng all the splendour they are capable
of acquiring from a free reflection of the light, does not
fail to remove, after the application of the first stratum,
all the small inequalities which may occur on the sur-
fiice, and particularly those rendered more apparent by
the knots and fibres which rise from the wood. He
rubs pumice stone gently over these inequalities. This
operation can be performed in a perfect manner on
every kind of painting, but in particular on that vnîh
essence : it adds greatly to the uniformity of the tone
and splendour of the varnish. It is always understood
that ceilings, if they are old, m.ust be carefully cleaned
and brushed, to remove the dust which becomes in-
crusted in the mouldings.
.16th. The reader, in perusing the detached obser-
vations which accompany the different formulss for the
preparation of varnishes, must have been struck with
the preference which 1 establish in favour of the com-
positions of the tliird, and even of the fourth genus, in
all cases of house-painting, to the detriment of those
which constitute the first two genera. There are some
varnishes, however, of the first and second genera
which may answer the proposed views: but, in general,
the consistence and tenacity of varnish made v/ith es-
sence are not to be expected from alcoholic varnishes.
Persons of delicacy may be hurt by its strong odour,
and may even consider this as a motive for excluding
it. But this motive vanishes in summer, and when the
apartments are not occupied too soon after. Besides,
this strong odour may be modified, and even entirely
PP.ECEPTS RESPECTING VARNISH. 449
dissipated. Nothing is necessary but to glaze over the
strata of varnish with a stratum of alcoholic varnish,
as soon as the former is dry.
17th. Art not only prescribes a good choice in the
kind of colours and in the nature of the varnish, but it
authorizes, and even requires, in some particular cases,
a certain œconomy in the use of the colours. Some
kinds of colours are exceedingly dear, such as vermi-
Hon and oxides of copper, which lose none of their
splendour, and which even experience advantageous
modifications when a ground has been applied of some
colour much cheaper. On such occasions, red oxide
of lead (minium) is united with English red, and red
sulphurated oxide of mercury, which is reserved for the
last stratum. The same reason of œconomy induces
painters to apply, under the green colour composed of
cupreous oxides mixed with white, a first stratum of
another substance destined to cover the wood or body
intended to be painted. In general, the priming for a
green .colour is composed of yellow ochre ground in
boiled oil, to which some essence has been added, and
mixed up with varnish or oil. But this base, which
harmonizes with the covering colour, opposes some re-
sistance to, desiccation, in consequence of its argilla-
ceous nature. It cannot, therefore, be employed in all
cases in which a green colour is required. Green with
oil answers exceedingly well on yellow ochre, when de-
sdned for external objects, such as gates, shutters, pa-
lisades, railing, Exc. ; but for apartments the place of
ochre ought to be supplied by an oxide of lead, such as
ceruse, which is more drying, and which gives jnorc
2g
450 TREATISE ON VARNISHES.
body to the green colour than argillaceous matters.
Besides, it is less apt to change to the tint of dark green
when exposed to the light.
1 8th. When varnishes are very little charged with
colour, as is the case when they form glazing, it is more
difficult to make a regular application of them than when
they are mixed with the ground. The essential point in
this application, and which discovers the real artist, is to
leave no marks of the brush. It must be drawn over
the surface in large strokes, and with celerity; forwards
and backv/ards are sufficient : if drawn several times
over the same place, the varnish rolls under the brush.
To produce uniformity in the glazing, too much var-
nish must not be employed at once ; because it forms
undulations and ridges, which break the reflection of
the light, and are very disagreeable to the eye of a
connoisseur. The strokes of the brush, also, must not
be made to cross each other, because in this manner
they cross the stratum, and the effect becomes as dis-
agreeable as in the preceding case. For the application
of glazing varnishes large flat brushes are employed ;
they perform the w^ork very quickly.
1 9th. The mixture of essence of turpentine with all
the varnishes employed for the decoration of apart-
ments, is attended with a very strong smell, which
continues several months. This odour, which is dis-
agreeable to every body, is prejudicial to delicate per-
sons subject to nervous affections : its effects, however,
may be checked or modified in a certain degree. Painters
recommend diiierent means for this purpose ; but they
attach little importance to them, as they are accustomed
CHINESE VARNISH. 45t
to such emanations. In this respect every artist has a
favourite process of his own.
20th. The details into which I entered in the se-
cond and third chapters on the composition of colom's,
and those in the present one, might be carried to a
much greater length ; but they are sufficient to prove
that the art of varnishing has been brought to greater
perfection in Europe than in China and Japan, where
it originated ; since the processes employed among us
require a much greater share of talents and know-
ledge.
These people are indebted to nature alone, and not
to industrious combinations, for the solidity of their
compositions; and they employ only a few processes,
from which they never deviate. The solid red, black, yel-
low, &;c. lacker which comes from their manufactories
is composed of no more than two substances. The na-
ture, therefore, as well as limited number of the co-
louring parts they employ, proves how little extent their
national industry has given to resources of this kind.
Vermilion and red bole for the red colour, orpiment
for yellow, and burnt bones or ivory for black, form
the whole magic of the palette of the Chinese varnish-
er; if we add the use of gold and silver, which he dis-
tributes with much profusion and little taste, though
his method of heightening the splendour of the gold
announces a good deal of dexterity and long practice.
If we consider the nature of the two substances which
serve as a base to their varnishes, and of which they
are formed, they may be compared to our copal varnish
of the fifth genus. One of these two substances is a
2g 2
452 Treatise on varnishes,
fluid, resinous matter, which thickens in the air, and
to which more body is given by a kind of oil that, in
the Chinese varnishes, acts the same part as linseed
oil in ours.
This first substance, or that which forms the var-
nish, is extracted from a ti'ee called by the Chinese
tsi-chou. It is a liquid resin, of a reddish colour, ob-
tained from incisions made in these trees, which are
cultivated in some of the provinces of the empire, and
particularly in those of Kiang--si and Se-tchuen. There
are three kinds of them ; the resinous juice of which
is distinguished by peculiar qualities, and v/hich the
Chinese apply to particular purposes.
The varnish, used as such, is called in China hoa^
hin-tsi. Tv>fo mordants made with the same varnish
are employed : one of them admits a mixture of orpi-
ment for certain gold colours ; and the second that of
cinnabar. The latter favours the application of gold
under its natural colour.
The extraction of this varnish requires precautions
on the part of those employed in that labour, as they
are exposed to noxious exhalations, the least effect of
which is to produce a dangerous kind of erysipelas.
To secure themselves from these vapours, they cover
the naked parts of their bodies with a kind of glue,
which prevents them from coming into contact with
the exhalation.
The second substance, which may be compared to
our linseed oil, is called girgili : it is known also under
the name of tong-yeon. With this oily matter, added
to tlie varnish, they mix up their colours, which they
CHINESE VARNISH. 453
extend over the polished wood. When the first strata
ars dry, they ornament them with various designs in
different colours, which they -decorate with gold or
silver. They then finish their works, which exhibit
more splendour and solidity than taste, and which the
worst of our artists would be ashamed to imitate in
regard to the design.
They employ two methods in the application of
their varnish. The first, which has been described,
consists in extending the colour, mixed up with varnish,
over the polished wood when perfectly dry. The
second requires more care. The furniture or articles
to be varnished are covered with a very hard coating,
formed of a sort of paste made with hemp, paper, lime,
fine sand, and some other matter, which, when pro-
perly prepared, is applied to the wood. Over this paste,
when very dry, and of which they compose also their
figures in relief, they extend the kind of oil destined
to receive the colours. This oil forms a very solid
ground, on which they trace out different designs.
They then spread over it two strata of varnish, and on
this varnish they apply the gold, which forms the basis
of their decorations. Having finished their subjects,
they are glazed with a third stratum of varnish, which
is polished with some soft body.
Our varnishes lose a little of their lustre when ex-
posed to the influence of humidity; and the alteration
would be still greater were they subjected to it when
they come from the hands of the artist. Those of the
Chinese are not affected by moisture; it even appears
that a damp atmosphere is of use to them, when in the
2 G 3
454 TREATISE ON VARNISHES.
artist's hands, or when newly finished. This effect
depends merely on the nature of the substances em-
ployed in these different kinds of composition.
The viscosity of the hoa-kin-tsi requires a method of
application which must be different from ours. In
China all operations of art are carried on slowly :
among us the contrary is the case; and there is reason
to believe that this arises from necessity. In some pro-
vinces of China, as at Pekin, where the air is very
dry, the varnishers are accustomed to expose their
works in their manufactories, which are more subject
to humidity than to dryness. Very often this condi-
tion even is not sufficient, since, according to the re-
port of Father D'Incarville, who has given us excel-
lent details on this subject, they spread over certain
compositions wet or very damp cloths.
Our European varnishes would certainly not admit
of this method. It has, however, been established in
China by experience; and it will not appear extra-
ordinary, if we only attend for a moment to the natural
effect of dry air on certain gummy or viscid mixtures.
The surface of an exceedingly viscous liquid, when
exposed to the influence of dry air, begins to be hard-
ened, and the first effect of this new consistence is to
check the desiccation of the part of the substance which
is not subjected to the same influence : the uniformity
of the texture is then interrupted. The permanent
viscidity of the interior part of the varnish, and the
dryness of its surface, soon occasion a shrinking in the
latter, which splits or cracks. This is the effect always
observed after a similar disposition. The Chinese then
CHINESE VARNISH. 455
are obliged to maintain the surface in such a state of
pliableness as may preserve harmony of consistence in
the whole stratum, in order that the moisture in the
interior part may have time to escape. The application
of wet cloths, or establishing manufactories in situa-
tions where the air can perform the same office, appears
to me to accord perfectly with the opinion which ought
to be entertained respecting the particular nature of
their varnish.
But, when the simplicity of the mechanical means
employed by the Chinese is compared with all those
processes, the aggregate of which constitutes what is
here called the art of varnishing considered in all the
parts which connect it with the art of making paper
boxes, coach-making, painting and gilding, one will
be convinced that the imitators have, in the course of
a few years, far surpassed the inventors, who in a series
of ages have not been able to deviate from the servile
routine, which among them confines the mechanical
part of the arts to uniform and invariable processes.
2 1st. The strongest smell, that is to say, the odour
which immediately follows the application of varnish,
arises from the evaporation of the essence. This ema-
nation is charged with other vaporous principles, fur-
nished by the different resins that enter into the cpm-
Dosition of varnishes, or which belong to the colouring-
parts mixed with them. Such, in particular, is the
nauseous odour of acetite of copper (verdigris). No-
thing but speedy evaporation, favoured by a current of
ail", or a condensation of these vapours, can answer
the purpose of those who wish to get rid of them.
2 G 4
ééë ■:./■ Treatise on varîtishes.
k„.V î"*!,
Ï^^a^oration is speedier in summer than in autumn,
'"Sélàsons during whicli most work of this kind is per-
formed. In summer, opening the doors and windows
will produce currents of air, and soon disperse these
noxious emanations. In autumn, a good fire made in
the chimney will accomplish the same end, but in
a slower mamier.
The disagreeable and even deleterious odour may
be weakened by the mixture of some balsamic sub-
stance, the odour of which is more agreeable to the
organs of smelling. It may readily be conceived that
this mixture will produce only a modification, whicU-^
will not admit of the apartments being sooner occu-
pied; but the odour will then exercise a different ac-
tion on the organs, and be less incommodious. Musk,
to persons accustomed to the smell of it, essence of
cinnamon,, of leriion juice, of thyme, of lavender, &c»
will effect this modification. New hay will answer the
purpose still better, if it be very dry; in this ctate it
changes the odour, and at the same time it absorbs, a&
a mechanical mean, the vaporous em^anation.
I have used for the same purpose a kind of con-
denser, which niav be easily obtained: I here mean
v.ater, several tubs filled with which ought to be placed
in the varnished apartment. The greater the surfaces
presented by t^ese tubs, the speedier will be the effect.
The water by its coldness condenses the odorous va-
pour, which is of an oily nature; and one may some-
times observe on the surface of it a pellicle, which
exhibits the prismatic colours, and which is formed
by the condensed vapour of the essence. The water.
PRECEPTS RESPECTING VARNISH. \^ 43^
m this case, performs the same office as a refn^f$,to^;.«
in the common process of distillation. I have em-*
ployed this method with complete success for apart-
ments varnished with verdigris, and varnish made v^ith
essence. Some workmen, who call themselves painters,
exclaim against the use of this condenser, under the
specious pretext that it destroys the splendour of the
varnish; but this fear is justified neither by reason nor
by theory.
When the varnish is dry, which may be knowTi by
the hand not adhering when applied to it for a minute,
and when nothing remains but the last vapours, which
are ahvavs long in escaping, nitrous fumigation, so
effectual in purifying foul air, may also be employed.
For this pv.rpose pour into a cup half an ounce of con-
centrated sulohuric acid foil of vitrioH ; and having;
added to it half an ounce of pulverized salt of nitre,
mix the whole v;ith the shank of a tobacco-pipe, or
with a glass tube. The extension of the fumes may
be facilitated by carrying the cup about through the
apartment. This preventive, however, may alter the
beautiful reflection of the varnish, if it be delicate and
not completely dry.
22d. Colours applied under varnish, as well as those
destined for oil painting, require great attention to
cleanliness on the part of those who employ them.
The surfaces to v/hich they are applied should be rub-
bed or swept, and even washed if necessary : they must,
however, be well dried afterwards.
The same care' must be extended to all apartments,
painted or varnished. Varnish is much more disposed
45S TREATISE ON VARNISHES.
to be altered by dirt than oil painting ; and the mean?
employed to bring it back to its first state cannot
always be the same, because the dust adheres more
strongly to the resinous parts which constitute varnish,
than to the surface of prepared oil.
A few strokes of a brush, with simple washing, will
be sufficient for varnishes which are usually kept clean,
if the dust be incrusted, soap and water must be em-
ployed by means of a sponge, taking care every time
that it has been rubbed over the varnish to rinse it in
clean water, and to squeeze it before it be again dip-
ped in the soapy water.
Some employ an alkaline Icy, to which they give
tlie name of second water. It is called weak second
water when it contains only a sixteenth or a twentieth
of the carbonate of potash (alkali of potash) ; when it
contains a tenth, it is strong second ivater. They even
leave it an hour or two on the varnish before they rub
it oft with a sponge, dipped in common water. This
method is attended with some inconvenience. The
alkiili exercises a strong action on delicate varnishes,
and deprives them of their brilliancy ; and if they con-
tain red from vermilion, or blue from prussiate of
iron, it alters or detaches them. But if this process
be improper for cleaning varnishes, the case is not the
same in regard to oil painting, and particularly gray
grounds, for which it seems to be exceedingly proper.
The quantity of the alkali may even be extended to an
eighth of the water employed.
Some employ for the same purpose water impreg-
nated with sulphuric acid (oil of vitriol), in such a
s.
METHOD OF CLEANING VART^ISH. 4S0
. manner that the acidity may be equal to that of stronpj
vinegar. This water is very detergent ; but it tarnishes
the varnish, and the application of it must be followed
by a thorough washing with pure water. This acid
has the fault of forming sulphate of lime (an earthy
saline matter, distinguished by the name of selenite),
which incrusts the surface of the varnish, so that no
washing can remove it. The friction which this ope-
ration requires necessarily alters the varnish. It is
much fitter for oil painting, which is more solid and
less injured by the effects of washing than delicate
resinous painting. But it will be necessary to diy the
surface well with soft and very warm cloths. If the
muriatic acid (the marine acid) were not dearer than
the sulphuric, it would answer much better for this
purpose ; because it forms with the dust a deliquescent
salt, which washing easily removes, and which, when
thus diluted with water, exercises no action on resins,
nor on the most delicate colours.
But whatever may be the means employed to clean
varnish or paintings by washing, they must not be left
till they have been completely dried with clean and
very warm cloths. Moisture is exceedingly hurtful to
them ; for this reason they ought to be protected from
the impression of fogs. These vapours, indeed, do
not possess any quality different from that of aqueous
humidity; but as fogs, in consequence of their perma-
nence, insinuate themselves more easily into all the
mouldings of wainscoting, they fix there, under the
form of an incrustation, all the fine dust conveyed by
the air ijito the closest apartments, and even into those
460 f R£ATISE ON VARNISI^ES.
which are inhabited; and this incrustation incorporates
in such a manner with the varnish that brushing is not
able to remove it. If the incrustation, however, has
not been suiFered to remain too long, washing with
water will be sufficient to detach it.
23d. During the process of applying oil colours,
if any of them fall on the clothes, it may be instantly
made to disappear by rubbing the cloth strongly with
a bit of bread. The same effect may be produced by
essence, which can be removed aftenvards by pure
alcohol, if the stained part be held before the fire.
24th. If any colour be left which you are desirous of
preserving, nothing will be necessary but to cover it
with water, and to deposit the vessel in a cool place.
The brushes may be kept in the same manner, after
care has been taken to free them by essence from the
colour adhering to them, and to wipe them.
Alcoholic varnishes are exceedingly drying, and they
possess great splendour: both these are reasons for
giving them the preference. Varnishes made with es-
sence are also brilliant; but they are less drying, and
they emit a strong odour, which they retain a long
time, when not covered by a stratum of alcoholic var-
nish. Oil painting is very durable ; it is even suscep-
tible of the brilliancy of varnish, if the colours have
been mixed up with the resinous drying oil, page 120,
Part I., or if it has been covered by a varnish made
with essence or with alcohol ; but it is slow in drying.
This character, which is a sign of its solidity, is a cause
of its being rejected by persons who sacrifice every
thing to expedition. The time of its desiccation, how-
4
. PRECEPTS FOR OIL PAINTING, 461
ever, may be very much shortened by adding to it
some matter of a very drying quality; but the labour
is more tedious, and painting of this kind never has
the brightness and lustre of varnish. This may ba
sufficient to justify the preference given to varnishing ;
but as many persons still retain a favourable opinion of
the old method of oil painting, and as it has its par-^
ticular rules, it is necessary that some account of it
should be given.
Oil painting.
Oil painting has a character of solidity which makes
it often be preferred to that executed with varnish or
in distemper. Besides, there are some circumstances,
independent of taste, which imperiously require the
use of it ; as when it is necessary to apply a colour to
external objects exposed to the influence of the weather.
This kind of painting is used also for internal articles.
All kinds of oil cannot be indiscriminately used for
this kind of painting, even when they form part of
those which reasons, founded on experience, have in-
dicated as alone proper for this use; such as oil of
pinks, nut and linseed oil, rendered drying by parti-
cular processes.
Painting destined for external objects, exposed to
the influence of the rain, solar light, &c.' requires nut
oil to the exclusion of every other Idnd, because it
nourishes and develops the colour. Linseed oil, in
this case, is dissipated, and destroys the colour; so that
at the end of a very little time the work must be re-
newed.
462 TREATISE ON VARNISHES. •
In the case of external painting, the colours must not >
be ground or mixed up with nut oil to which essence
of turpentine has been added; because the latter whitens
the colour under the impression of the sun, in the
same manner as pure linseed oil would do.
Linseed oil may be recommended in painting de-
stined for internal articles, which are sheltered from
the inclemency of the weather.
This kind of painting has its particular precepts,
from which it will be proper never to deviate.
1st. When it is necessary to grind and mix up
bright colours, such as whites, grays, &c. nut oil or
oil of pinks is used. For dark colours, such as ches-
nut, brown, and olive, pure linseed oil is preferable,
if the painting be destined for internal objects.
2d. Each stratum is applied cold. It is never em-
ployed in a state of ebullition, except when it may be '
necessai^ to prepare a nevv wall, or new and damp
plaster, in order to make the paint adhere. Without
this precaution, the paint rises, and falls off in scales.
The first stratum on soft wood requires also a little •
heat, that it may penetrate better.
Sd. No colour mixed up with pure oil, or oil to
which a little essence has been added, ought ever to
form a thread at the end of the brush.
4th. The colour must be stirred in the pot from
time to time, before any of it is taken up with the
brusli, in order that it may preserve the same con-
sistence and the same tone. If the ground, in conse-'
quence of metallic colours being used, does not retain
:precepts for oil painting. 46S
the same tint, it may be brightened by pom-ing in a
little of the same oil as that with which the colour has
been mixed up.
Some painters, who are negligent in regard to the
consistence proper to be given to the colour, before it
is employed, think they can accomplish the required
end by adding essence to the colour from time to time,
when they think it too thick.
This method, in ordinary painting, is not attended
with much inconvenience; but it does not answer the
purpose in delicate painting. The addition of cold
essence lessens the splendour of the colour ; and this
effect arises from the resin of the varnish beginning to
be precipitated, if a varnish form the basis of the paint-
ing ; and from a commencement of separation in the
colouring part united to the oil, if the painting be in oil
colours. In the latter case, it will be of great advantage
to give the real consistence at first; and if it be found
necessary to add a little more of the excipient, it ought to
be warm: it requires to be well mixed before it is used.
5th. When the paindng is destined for apartments,
the first stratum ought to be ground in oil, and mixed
up with essence. 1 st. Because tKe latter carries off the
odour of the oil. 2d. Because the colour applied over
a stratum mixed up with oil, to which essence has been
added, or with pure essence, becomes more brilliant,
whereas it would penetrate into a stratum with pure
oil. 3d. Because essence thoroughly hardens the co-
lours mixed up with it ; but if mixed with oil it makes
it penetrate to the colour. When you are desirous,
therefore, to varnish an oil colourj^^ the first stratum
ought to be mixed up with oil, and the last t^vo with
4G*i TREATISE ON VARNISHES.
pure essence, When you do not intend to varnish, the
first stratum ought to be mixed with pure oil, and the last
two with oil to which essence has been added. Essence
unites to the two advantages before mentioned a practical
utility : it facilitates the extension of the colour.
()th. If the painting be intended for copper, iron, or
any other hard substance, the smoothness of which
opposes the adhesion of the colours by making them
glide, a little essence must be added to the first strata :
the essence will cause the oil to adhere. Besides,
metals intended to receive varnish or colours must be
polished or scoured, that is to say, roughened a little,
in order that the colour may lay hold of them : this
rough polishing is performed with pulverized pumice
stone or tripoli, Vv hich is rubbed over the article with
a piece of rag, on each stratum being applied. The
article must then be exposed to the sun to facilitate
the extension of it, if the varnisli has a considera-
ble degree of consistence ; after which it is carried
to a stove to hasten its desiccation. My turpentine
copal varnish, and that even caHed fat varnish, dry
very speedily. The operation of polishing is not per-
formed till several strata are applied and have become
dry. When such varnishes are used you may begin
the polishing with pumice stone, and afterwards finish
it with tripoli.
7th. If the wood contain resinous knots, which is
the case in particular in fir, the colour runs in these
knots, and does not adhere. If simple oil be employed,
oil charged with drj^ing matter, that is to say, litharge,
mixed with a littio of the ground colour, is prepared
separately, and reserved for these r-j^inous parts. Ii'
Precepts iît regard to oil fronting. 4^5
the painting be in oil, and intended to be covered with
polished varnish, more litharge must be added: it
masks the wood, and hardens the resinous particles
which exude from it. One stratum will be sufficient,
and will give body to the wood : thé labour may be
shortened by rubbing the place with a head of garlic.
8th. Some colours, and in particular those which;
have an argillaceous ground, as the Dutch pinks,
boles, kc, as well as lamp-black, burnt vine twigs,
&;c., are long in drying when employed v?ith oil. It
"tt'ill, therefore^ be proper to add drying matter to them,
according to the colour: litharge to dark Colours, and
sulphate of zinc (white vitriol) to bright colours, mixed
-with drying oil : this method is always attended with
success. I must here observe that drying matter is
unnecessary in all cases, and for all colours which ad-
mit into their composition ceruse, white oxide of lead,;
mid other metallic oxides.
9th. If the addition of drying matter becomes ne-
cessary, it must not be added till the moment when
the colour is applied, because k tends to rerder it
diicker.
10th. One principle, which ought never to be for-
gotten, because it is applicable to ail kinds of painting,
aiid riiore particularly to the one in question, is, -that,
a nevv' stratum of colour ought never to be applied till
the preceding is dry. It will be proper also to brush
off the dust, which sometimes covers the last stratum ;
and which, if mixed with the new one, would not fail
to alter the uniformitv of its tint : this observation is
applicable, above all, to bright colours, such as whites
466 TREATISE 01^ VARNISHES.
and grays. You niay be sure that a stratum is dr}%
when it does not adhere to the hand on being applied
to it.
11th. All kinds of pamting require that each stra-
tum of colour should be of an uniform thickness
throughout ; and as this depends on the consistence, it
tvill be proper to maintain it in the same state. Habit
and experience will be a better guide, in this respect,
than any precepts that might be collected. Too thin
a stratum cracks by desiccation ; one too thick be-
comes wrinkled, acquires undulations, and interrupts
the re££ction of the light. The addition of a little
ground colour, or of some of the vehicle, vill correct
one of these faults.
It v.ill not, however, be attended with any incon-
venience if a little mofe liquidity be given' to the fii"st
stratum than to the succeeding ; because it is destined
rather to adl'iere to the substance which it covers, than
to esîevblish the tone of the required colour. But the
succeeding ones, and pardcularly the last, ought to
have sufficient consistence to prevent the shrinking of
the painr; the addition of a little essence will, if it
be too thick, bring it to the proper point.
Î2th. If a soliditv capable of resisting blows and
fjriction be required in the paint, this end will be
better obtained by applying the first stratum with a me-
tallic oxide, such as Montpellier yellow, ceruse, or
vitreous oxide of lead (litharge), reduced to fine pow-
der, ground in boiled oil, and mixed up with oil to
which a little essence has been added, than by the
same colour mixed up wiîh oil.
PRECEPTS IN REGARD TO OIL PAINTtN(^-'^:
13th. Artists, during the exercise of a profession,
acquire habits, which, among persons who are desirous
of placing themselves on a level with them, are con-
verted into precepts. The amateur, after the first
trial, is merely a eervile imitator of the painter. In
the use of the brush he does not at first show much
dexterity; but being the judge of his own work, he
soon discovers that he wants experience ; and he at
length attains, though slowly, to results which, in a
skilful hand, soon improve. He feels the necessity of
varying the strokes of the brush according to circum-
stances. Sometimes he employs long strokes, to ex-
tend the colour in an uniform manner ; at other times
he daubs it repeatedly over the wainscoting, to incrust
the matter in the places sheltered by the mouldings or
by sculpture. He avoids inequalities ; he is encouraged
by the new aspect which presents itself to his eyes; he
perceives, and at length is convinced, that the perfec-
tion of the application concurs, in a considerable degree,
tovv'ards the richness and tone of the colour, and the
beautiful development it acquires from the reflection
of the light. Every amateur who is fully sensible of
the necessity of obtaining these results may be con-
sidered as an artist. I will even say more; he is su-
perior to a workman without taste, whatever practice
he may have had in work of this kind. The labour soon
vanishes when compared with the enjoyment he pro-
cures.
But this kind of painting is attended with one cir-
cumstance, which requires the concurrence of different
artists,, as the labour is superior to the efforts of tha
2 H 2
i6S TREATISE ON VARNISKES.
amateur, however expert. I allude here to coacfe
painting, which requires the union of the limner, the
common painter, and the gilder. Besides, the appli^
catioli of varnish, in this case, ought to be followed by
an operation which is dispensed with in all cases of
A'arnishing or painting applied to common apartments>
and to external objects: I mean polishing. This ope-
ration, which the amateur has no need to perform^
shows the necessity of admitting into this species of
painting a division respecting the different kinds of
labour which it requires»
Division of oil painting*
Oil painting may be divided into two kinds; namely,
common oil painting, and painting in oil with polished
varnish. The first is simple, the other is more exten-
sive ; it forms grounds, which are polished and after-
wards covered v^^-ith a varnish, which is also polished.
This addition of labour induces artists to admit tjie
above-mentioned division, the necessity of which does
not appear to me to be well fouiided. As painting in
oil constitutes a separate kind, disdnct from painting
in varnish and painting in distemper, we can admit ne-
other divifîioîi than that which form? it into species^
especially -when the same matters are employed in both
cases. All oil painting is susceptible of acquiring gi
fine polish, when the thickness of the strata admits the
application of those processes which polished painting
in varnish requires. It may be both varnished and
glazed, to increase the brightness of the colour, and to
sail it forth in its full splendour. I have even given ^
Polishing. 46#
iTiethod of fulfilling, at one operation, the conditions
which establish plain painting in oil, and that in which
varnish is employed. This method is that which re-
quires the use of the drying resinous oil in page 1 20.
This distinction is deduced rather from that made
between the objects for which this kind of painting is
destined, than from the nature of the materials em-
ployed, or from the variety introduced in the com]>o-
sition of them. All carriages are painted in oil, then
varnished, and afterwards polished. Some kinds of
valuable furniture and toys made with artificial enamel
require also the last-mentioned operation, which gives
them a great deal of splendour, and disposes them to
ï'eflect'the light in a more uniform manner*
Polishing,
The processes used in polishing are different, ac-
cording to the nature of the varnish which requires it.
Hard varnishes, such as those resulting from the solu-
tion of amber and copal in a drying oil, or even in
essence, as well as certain oil colours, can hear the
contact of hard bodies employed for polishing. It is
not, however, attended with complete success but when
the ground is charged with a determinate number of
strata of a colour which, by painters, is called the
priming (^teinte duré) *. This priming gives to the
* The priming {tc'vitc dure) is prepared by grinding ceinise very
fine in pure oiJ^ and raiy.ing it irp with essence of turpentine.
Seven or eight strata of it are applied before it is pohshed. The
ceruse empkîyed for this purpose must have been subjected to a
certain degree of heat, which destroys its whiteness, and prevent»
2li 3
470 TREATISE ON VARNISHES.
whole a certain thickness and a great deal of con-
sistence.
When the priming has received all the strata it re-
quires, and when very dry, pumice stone finely pul-
verized, and sifted through a silk sieve, is mixed up
with a sufficient quantity of water. Some of this
powder is spread over a piece of cloth, rolled up in
the form of a ball, and the ball is moved .over the sur-
face of the colour, to polish it uniformly : to deter-
jnine with precision to what degree this has been ef-
fected, the polished part is frequently washed with
water. When this operation is finished, two or three
strata of the colour which has been chosen are applied,
the motion of the brush being softened to avoid striie;
and it is then glazed with two strata of transparent and
colourless varnish, should this number be thought suf-
ficient : but if the varnish itself is to be polished in the
same manner as the priming ; in a word, if it be re-
quired to imitate that which covers the pannels of car-
riages, seven or eight strata must be applied.
When the last strata of the varnish form undulations,
which cut, derange, or break the reflection of the
light, it will be necessary to polish it. This last polish-
it from weakening the colonrs applied over it. In this state it is
called by painters calcined ceruse: the colour of it inclines a little
to yellow. It will be proper not to give too much heat to the
ceruse destined ior different strata of priming, because it has too
jnuch influence on the coloured grounds -which it ought to sup-
port. The strata of priming are applied over a stratum formed of
tmcalcined ceruse, ground in linseed oilj and mixed up with equal
parts of linseed oil and essence.
3
POLISHING. . 471
ing may be performed with advantage by employing
tripoli, reduced to fine powder, mixed up with a little
y>il, and placed on a ball of serge, or, what is better,
of shamniy leather. The fat part may then be re-
moved with a little bran, or v.iih. farina, rubbed over
it by means of a clean linen cloth. The polishing is
then completed with a bit of serge or cloth, without
tripoli.
It is in this manner that the varnish which supplies
the place of glazing on certain kinds of furniture, and
the coloured or uncoloured varnishes apphed to metal-
lic bodies or plates of metal, are polished. The latter
require only uniform friction with a piece of clotli. It
is very seldom that there is any need of beginning with
tripoli and oil. The finest polishing is that performed
by the lathe.
Those vv'ho renew the colours on the pannels and
bodies of caiTiages, do not amuse themselves by rub-
bing them with a piece of serge and pulverized pumice
stone. They wear down the old colour to the wood,,
with a fragment of pumice stone and water. Some
even employ for this operation a piece of felt and fine
sand. This process is alone suited to work of this
kind.
If you vv'ish to render the colour more drying, add
half an ounce of the vitreous oxide of lead (litharge)
to each pound of colour. If the colour is bright, a
gros of the sulphate of zinc (white vitriol) must be
substituted for the litharge.
2 H 4.
473 TRI^ATISE ON VARNISHEB.
Ofîcax doth. Oil cloth.
It is possible that the term wax cloth, given to some
cloth prepared in a certain manner, origiuated from
the first trials, in which wax perhaps formed a part of
the composition; or it may have arisen from one of
those modes of concealment, so often employed by
inventors, who endeavour to take advantage of their
researches, or of a happy discovery. It is, however,
certain that this denomination is absolutely foreign to
the articles of this manufacture, in which wax is not
used.
The art of preparing these cloths is one of those
which escaped the ingenious and useful undertaking of
the lite Academy of ^Sciences at Paris, entitled De-
scription des Arts et Métiers. I am acquainted with
no author who mentions it even indirectly. What I
shall offer, in this work, will be only a sketch of the
art, the processes of which, in regard to the grounds
and the application of the coloured designs, are so
varied and interesting as to justify and even render
valuable a detailed description of them. The manu-
facture of these cloths, considered under a political
point of viev/, is not unworthy the' attention of the
public. 1 shall, however, confine myself to some par-
ticular experiments, and to the knowledge I have acr
quired in regard to this kind of labour : it will be suf-
ficient to prove that the preparation of oiled silks and
oil-skin is connected with that of varnishes, and de*
cendent on it.
This art originated in Holland, in consec^uençe, nq
OIL CLOTH. 475
doubt, of the wants of commerce, which consumes
such a large quantity of articles proper for packing
^oods. It is probable that the first attempts \ver2
undertaken with a view to this end, which seemed to
insure to them a constant and extensive sale. It is
probable also that the first processes admitted the use
of wax, and that the cloth first manufactured might
have a resemblance to those packing-cloths which come
from India, and which are covered with a waxy sub-
stance.
The name of wax cloth, Vv^hich was then proper for
them, sui"viving the composition, may have served to
ilenote, till the present time, finer compositions, exe-
cuted with greater care, and yet less expensive; as
wax is of more value than the substances now used in
preparing these cloths, which are employed for so many
useful purposes.
If Holland was the birth-place of this kind of manu«
facture on a large scale, it is possible that the first
processes may have been known and folio v/ed in neigh*
bouring countries. This much, at any rate, is cer-
tain, that the extent since given to the manufacture,
by admitting a certain finish in the designs, must con-
tribute to multiply the enterprises. There are indeed
excellent manufactories of this kind in the ci-devant
Austrian Netherlands, in Germany, and particularly at
Franckfort, where the v/orkshops altogether occupy a
very considerable extent.
Every manufacturer and every v/orkman has his own
compositions and methods, which he applies to the
Jdnd of work intrusted to him. The process for com»
474' Tr.EATISE ON VARNISHES.
mon vai'pished cloths is veiy simple; bat, as I havç
already said, their e are others. which require more in,
telligënce on the part of the workman, as the same
care is necessary as for painted cloths. In these varr
nished cloths the art of the colourist is put to tlie test ;
because the hnishing, the happy mixture of the colours,
the richness of their variety, the natural appearance of
the shades, and the delicacy of the strokes, concur to
enhance their value, and conseque;ntly to secure to
them a speedy sale.
But if the diilerence of the labour has so powerful
an influence on this kind of manufacture, it may readily
be conceived tha.t the quality of the cloth must contri-
bute towards the same end; for it is this quality alone
which determines the kind of painting that ought to be
employed. Varnished cloths, therefore, of different de-
grees of fineness are manufactured.
Common ivax cloth or varnished cloth.
The manufacture of this kind of cloth is very sim-
ple, and may be canied on at very little expense. The
cloth and linseed oil are the principal articles required
. for the establishment.
Common canvas, of an open and coarse texture, is
extended on large frames, placed under sheds, the
sides of which are open, so as to afford a free passage
lo the external air. The manner in which the cloth is
fastened to these frames is very simple and convenient ;
for when it becomes slackened, during the application
of the varnish paste, it cTin be again tightened. It is
fexed to each side of the frame by a kind of hooks
LIQUID PASTE FOR OIL CLOTH. 475
which catch the edge of the cloth, and by pieces of
strong packthread passing through holes at the other
extremity of the hooks, which are tied round move-
able pegs placed in the lower edge of the frame. The
mechanism by which the strings of a violin are stretched
or unstretched, will give some idea of the arrangement
of the pegs employed for extending the cloth in this
apparatus. By these means the cloth can be easily
stretched or relaxed, when the oily varnish has exer-
cised an action on its texture in the course of the ope-
ration. The whole being thus arranged, a liquid paste
made with drying oil, which may be varied at plear
sure, is applied to the cloth*
Liquid paste ivith dri/ing oil.
Mix Spanish white or tobacco pipe clay, or any
other argillaceous matter, with water, and leave it at
rest some hours, which v/ill be sufficient to separate
the argillaceous parts and to produce a sediment. Stir
the sediment with a broom, to complete the division
of the earth; and after it has rested some seconds
decant the turbid water into an earthen or wooden ves-
sel. By this process the earth will be separated from
the sand and other foreign bodies, which are preci-
pitated, and which must be thrown away. If the earth
has been washed by the same process, on a large scale,
it is divided by kneading it. The supernatant water
is thrown aside, and the sediment is placed in sieves,
on pieces of cloth, where it is suffered to drain : it is
then mixed up with oil rendered drying by a large
dose of litharge, that is to say, about a fourth of the
weight of the oil The consistence of thin paste being
47G TREATISE ON VARKISHE?.
given to the mixture, it is spread over the cloth by
means of an iron spatula, the length of which is equal
to that of the breadth of the cloth. This spatula per-
' forms the part of a knife, and pushes forwards the ex-
cess of matter above the quantity sufficient to cover the
cloth.
Though the earth mixed m this manner stHI contains
water, it readily unites with the boiled oil. The watei*
passes into the tissue of the cloth, which facilitates its
evaporation ; and the cloth at the same time acquires
the property of not suffering itself to be too much pe-
netrated by the oily vaniish. However hquid the var-
nish may be, it does not transude to the inferior sur-
face of the ck)th.
When the first stratum is dry a second is applied.
The inequalities produced by the coarseness of the cloth,
or by an unequal extension of the paste, are smoothed
down with pumice stone. The pumice stone is reduced
to powder, and rubbed over the cloth with a piece of
soft serge or cork dipped in water. A whole pumice'
stone, one of the faces of which has been ground
smooth, may also be employed. The cloth must then be
well washed in water to clean it ; and, after being suf-
fered to dry, a varnish of gum lac dissolved in linseed
oil boiled with turpentine, and which is liquefied with
essence of turpentine, if necessaiy, is then applied to it.
This preparation produces yellowish varnished cloth.
When you are desirous of rendering it black, nothing
will be necessaiy but to mix lamp black with the Spa-
nish white, or tobacco-pipe clay, which forms the basis
of the liquid paste. Various shades of gray may be ob-
tained, according to the quantity of the lamp black
PRINTED VARNISHED CLOTHS. 477
■V'hlch. is added. Umber, Cologne earth, and different
ochrey argillaceous earllis, the nature of which has
been explained in the chapter on colours, may be used
to vary the tints, wit hout causing any adddition to the
expense.
Fme priiite d varnished cloths.
The process just described for manufacturing com-
mon varnished and polished cloths may serve to give
some idea of that employed for making fine cloths of
the same kind, decorated with a coloured impression.
At first this kind of manufacture was confined to com-
mon cloths^ with a smooth ground of diffei^ent colouts.
Industry, however, has given it greater extent, by find-
ing on the palette of the painter ail those materials ca-
pable^of making this new art rival that of printed cloths.
The firmness of the texture of the cloth, still increased
by that of a pliable covering impermeable to watef,
'opened for this kind of manufacture a very lucrative
sale, in consequence of a more careful application of
the colours, which could be subjected to all the rules
of design. The manufactories of Germany, indeed,
have varnished cloths embellished with large and small
subjects, figures, and landskips, w^ell executed, and
which being destined for covering furniture subjected
to daily use, gave certain support to this branch of in-
<lustry.
This new process, which is only an improvement of
the former, requires a finer paste, and cloth of a more
delicate texture. The stratum of paste is applied in the
jsame manner j and when dry and polishedj the cloth is
478 TREATISE ON VARNISHES.
taken froni the frame and removed to the painter's
table, where the arc of the colourist and designer is
displayed under a thousand forms ; and, as in that of
printed cottons, exhibits a richness of tints, and a dis-
tribution of subjects which discover taste, and ensure
a ready sale for the articles maiuifactured.
The processes, however, employed in these two arts
to extract the colouring; parts are not the same. In the
art of cotton-printing the colours are extracted by the ' |
bath, as hi that of dyeing. In printing varnished cloths,
the colouring parts are the result of the union of dry-
ing oil mixed with varnish, and the different colours
eniploycd in oil painting or painting in varnish.
The varnish applied to common oil cloth is com-
posed of gum- lac and drying linseed oil ; but that de-
stined for printed varnished cloths requires some
dioice, both in regard to the oil and to the resinous
matter which gives it consistence. Prepared oil of pinks
and cop:il form a varnish vei-y little coloured, pliable,
iind solid.
Vafnîshed si IL
There are two kiiids of varnished silk j one employ-
ed for making umbrdhis, capots, coverings for hats.
Sec; and the other known under the name of sticking
plaster, or court plaster. -
The first is prepared in the same maimer as the vr.r-
nished and polished cloths idready described, but with
some variation in the choice of the matters employed to
make the liquid paste or vamish with which the silk is
covered. The basis of the second is a gelatinous stra-
• VARNISHED SILK. 47^
f
tuni, which is afterwards covered wiih a varnish of the
first geiius : thin is say, an alcoholic varnish exceed-
ingly simple in its composition.
For the preparation of the former, if the surface of
the silk be pretty large, it is made fast to a wooden
frame furnished with hooks and moveable pegs, such
as that used in the manufacture of common varnished
cloths. A certain quantity of a soft paste, composed
of linseed oil boiled with a fourth part of litharge,
white of Troycs, Spanish white or tobacco ^ipe clay,
lamp black and litharge, is then prepared in nearly the
following proportions : tobacco pipe clay, dried and
sifted through a silk sieve, 1 6 parts ; litharge ground
on porphyry with water, dried and sifted in the same
manner, 3 parts ; lampblack,] part, 'J1iis paste is
then spread in an uniform nvanner over the surface of
the silk, by moans of a long knife having a handle at
each extremity.
In suamier twenty-four hours are sufiicient for its
desiccation. When dry, the knots {produced by the
inequalitii'S of Ihe silk are smoothed with pumicQ
sione. This operation is performed with water; and
when finished the surface of the silk is washed. If is
tlien suffered to dry, and the copal varnish of the fifth
<»;cnus No. 2'3. is applied.
If ir be inteniled to polish this varnish,'it will be pro-
per to apply a second stratum ; after which it is po-
lished with a ball of cloth and very fine tripoli, or with
a piece of strong cloth only. I'he varnished silk which
results from this process is very black, exceedingly pli-
able, and has a fine polish. It mav be rumpled a
4S0- TREATISE ON VARNISHES.
thousand ways without retaining any fold, or the mark
of a fold. It is Hght ; and this quality renders it proper
for coverings to hats, and for making cloaks and caps,
so useful to tra\Tllers in the dme of rain»
When manufacturers wish to turn to advantage old
o
remnants of silk, whatever may be their colour, which
do not exceed half a yard in length, they think it suffi-
cient to fasten them to frames of the same size with a
piece of packthread, keeping them as much stretched
as possible. The liquid paste is then poured over the
silk in small portions, and spread out by means of a
common knife with a round point, somewhat like that
of a table-knife, to prevent the cloth from being cut.
The handle of the knife stands at right angles to the
blade, so that all the movements required for extend-
ing the paste can be made without the fingers touching
the silk, and without removing the blade from an ex-
act horizontal posidon : a little practice will enable the
workman to render the surface of the silk as smooth in
this case as in that v.'liere a large blade is employed in
the operations on a more extended scale.
In the last place, if the silk consists of long narrow
bands, the mechanism which I employed for making
two or three yards of plaster at Once may be used.
Provide a common smooth table, eighteen or twenty
Juches square, and placed perfectly horizontal. At the
two extremides of this table let there be fixed two iron
screws in a perpendicular direction, which pass through
two rings at the extremides of an iron rule or .blade
which stands in a vertical position, and v/hich can be
moved nearer to or further from the table by means of
VARNISHED SILK. - éSl
tVvo nuts fitted to the screws. But to determine .'tfee
thickness of the stratum of the composition to be spreail
over 'the cloth, there are placed close to the screws,
and between the rule and the table, as many squares
cut from a common card as may be necessaiy to give
the thickness required ; two or three will be sufficient.
When this arrangement has been made, place one
of the ends of the cloth between the rule and the table,
in such a manner that it may pass beyond the former
about an inch, that you may be able to draw it to-
wards you during the operation ; then pour the com-
position on the cloth near the interior side of the rule
in such a manner as to cover the cloth throughout its
whole breadth. " Care must be taken to make the mat-
ter continue running, while another person draws the
cloth towards him till the whole of it has been sub-
jected to the pressure of the rule. By this mechanism
the stratum will have an uniform thickness, and will
be so even as to have no need of being smoothed with
pumice stone. When the stratum is dry, cover it with
the copal varnish No. 23.
It was with a similar composition and by an ana-
logous process that an artist of Geneva, named Lou-
vrier, prepared his pliable varnished silk, specimens of
which he presented to the society of arts : the same
paste also, covered with a varnish, he applied to linen,
felt, leather, &c. ; and the use of it might be rendered
more beneficial and extensive by applying it to boots,
half-boots, and shoes, which might jn this manner be
rendered impermeable to water.
21,
.4S^<^ TREATISE ON VARNISHES.
,J^y Another hind of varnished silh,
A kind of varnished silk, which has only a yellowish
colour, and which suffers the texture of the stuff to ap-
pear, has been some time iii use. l"he matter employed
in the preparation of it is a plain vaniish. The silk is
covered \i^ith a • mixture of three parts boiled oil of
pinks, and one part of fat copal varnish, which is ex-
tended with a coarse brush or with a knife. Two
strata ?.re sufficient when the oil has been freed from
its greasy principles over a slow fire, or when it has
been boiled with a fourtli part of its weight of vitreous
oxide of lead (litharge).
The inequalities are removed by pumice stone and
water; after which the copal varnish is applied. This
sinrple operation gives to white silk a yellow colour,
which arises from the boiled oil and the varnish.
This varnished silk possesses all those qualities ascri.
bed to certain preparations of silk which are reconv
mended to be worn as jackets by persons subject to the
rheumatism. Some physicians have placed great con»
fidence in flannel dyed with indigo : it would-be very
easy to inti'oduce this colom- mto die rarnish destinée!
for this preparation.
Sticking plaster. Court plaster.
Tlie preparation of sticking plaster or court piaster
is still simpler : the basis of the first stratum is glue. £
Bruise a sufficient quantity of fish glue, and let it f
soak for twenty-four hours in a little warm w^ter : ex.» f^
COURT PLAStER. AT^j^S^.
pose it to heat over the fire to dissipate the greatenÇM ^^ vz^ :
of the water, and supply its place by colourless brano^iA^ t^ /
which will seize on the gelatin (glue). Strain the
whole through a piece of open linen, and take care
that the quantity of the excipient be siich that on cool-
ing it shall form a trembling jelly. ^^ ^- -
Extend a piece of black silk on a wooden frame,
and fix it in that position by means of tacks or pack-
thread. Then with a brush made of badger's hair
apply the glue, after it has been exposed to a gentle
heat to render it liquid. When this stratum is dry,
which will soon be the case, apply a second, and then a
third if you are desirous of giving the plaster a certain,
thickness. As soon as the \vhole is dry, cover it with
two or three strata of a strong tincture of balsam of
Peru.
This is the real English court plaster : it is pliable
rind never breaks ; characters which distinguish it
from so many other preparations sold under the same
name.
This article has been adulterated as well as many
others. A kind of plaster, the covering of which is
very thick and brittle, is often sold under the same
name. The fabricators of this article instead of fish
glue, which is dear, employ strong common glue, 'the
strata of which they cover with an alcoholic varnish
like those of the first genus. This plaster cracks, and
never has the balsamic odour by which the real English
court plaster is particularly characterized. To detect
this fraud nothing will be necessary but to rub it a
little.
2 i2
4^ ♦ TB-f ATÏSE QN VARNISHES.
,»
When you \vi$h to use the Englisii plaster, moiste^i
.îe with saliva on the side opposite to that '^\'hich is var-
nished, and it will adhere exceedingly well. The adul-
terated piaster is too hard to adhere by so simple a pre-
paration J it requires to be moistened on the varnished
side.
'i'he use of this plaster ought to be confined to cuts
alone; and should never be extended to scratches or
wounds accompariied with contusion, though this re-
striction seems contrary to the pompous directions for
using it which are pubUshed. In the two latter cases
the application of any gummy plaster, however well
prepared, is always attended with inflammation, which
must afterwards be treated with cataplasms of bread
and milk.
Having said every thing necessary in regard to paint-
ing in oil with or without varnish, comprehending that
branch which relates to varnished cloth and silk called
improperly wax cloth, it now remains that I should
describe th^ last kind of painting, called painting in
distemper :— It forms the subject of the following
chapter. •
[ 4S5 ]
CHAPTER v..
Of painting in distemper. Sizing. Composition of flours
for distemper. General precepts in regard to this hranch
of the art,
XiiE use of distemper is older than that of painting in
oil or in varnish. It is needless to adduce any.-testi-
monies to prove this assertion, for we may assign to
this art the same origin as that of white-washing.
White -washing applied with art is a Idnd of distemper
when the builder, induced by a desire of giving it so-
lidity, introduces into ii glue, which is one of its prin-
ciples, whatever be the matters over which it is ex-
tended. The polishing which is given to this kind qf
work by several washings has an affinity to distemper
which the French call Badigeon.
The first attempts in distemper must have been vei*y
imperfect ; but being susceptible of assistance from the
different colouring parts which contribute so easily
towards the magic effects of painting, this branch of
house-paintmg must have participated in the general
improvement resulting from the continued efforts of
human industry : it must have deviated from its first
rules of simplicity to rise to a degree of perfection. It
soon, indeed, became the basis of the painting with co-
loured grounds on which the first trials were made of
glazed varnishes, and under the names of chipoliu and
ùlanc dç roi was employed as one of the most elegant
2i $
486 'TREATISE ON VARNISHES,
and most esteemed decorations for embellisliing palaces
in all cases where it was ornamented with figures.
In every kind of distemper glue, a gelatinous matter
extracted from diifereijt parts of animals, of whatever
sort it might be, becarne the principle of the solidity
observed in this branch of painting. It serves as a
bond to the divided parts, which are united by a pul-
verulent adhesion of mere contact: in the last place,
it prevents them ii'om being detached when rubbed
with a brush.
The varnisher does not confine the use of glue to
painting in distemper : he destines it also for covering
and preserving the paint with which certain articles in-
tended to be varnished are covered j such as paper or
other substances painted in gum ; boxes, fans, &c.
But the Idnd of articles to which size is applied pre-
scribes a choice in the matters proper for furnishing the
glue. For delicate objects pure glue incapable of com-
municating any foreign tint is required. Fish glue or
that obtained from remnants of parchment will an-
swer these conditions. Glovers' clippings and those
of white leather give a glue sufficiently pure for com-
mon distemper. The glue extracted from the clip-*
pings of sheep's and goats' skins may be used in the
common kind of distemper. In the latter cases the
work may be considerably shortened by dissolving
common strong Flanders glue in a certain quantity of
water-. This glue is the dry extract obtained from the
ligaments, cartilages, tendons, interior membranes, and
clippings of the skins of animals, which have been sub-
jected to strong boiling.
FISH GLUE. 4§7
All these substances give a gelatin (glue) weaker
or stronger, according to the age of the animal and
the part from which it has been extracted. That ob-
tained from the skin is the strongest, Flanders glue,
however, is employed in general for all arûcies to
which distemper is applied on a large scale ; because
in works of this kind transparency i$ required ratiier
than strength.
GLUE OF THE FIRST QUALITY.
Fish glue.
Whatever be the matter from which it is proposed
Î0 extract the gelatin (glue), the process always em-
ployed is strong decoction in water. Fish glue holds
the first rank among the substances of this kind on ac-
count of its being colourless. The preparation of it i§
very simple. The twisted pieces of the membranous
matter which furnishes it is bruised by means of a mal-
let, and then torn to shreds, which are cut into small
portions and boiled in a sufficient quantity of pure
water. The decoction being strained through a clean
eloth which retains the membranous part, it is evapo-
rated over a slow fire until it be observed that some
ilrops of the decoction thrown on paper and deposited
in a cool place assume the consistence of a trembling
jelly. . The decoction is then left to cool. In this
state it will keep five or six days in summer, and
longer* in winter.
Sometimes brandy is employed for diludng this
2i4
4gS TREATISE ON VARNISHES.
glue ; but as the temperature to whicli it is exposed
dissipates all the spirituous matter, it wilt be better to
add brandy to fish glue already prepared and of a con-
sistence somewhat strong. The addition of the brandy
contributes towards its longer preservation, and accele-
rates its desiccation when employed, but it lessens the
limpidity of the liquid.
This consistence would prevent it from being freely
extended over the works which are to be sized, were it
not diluted at the time of its being employed with a little
warm water. It is in the latter state of Hquidity that
It is appHed to articles which can stand the rec[uired
degree of heat, such as wood, fans, &c. But when it is
apprehended that this temperature may produce bad
effects on the colours or on the cut paper figures, for
cementing which it may be employed, it is then di-
luted with cold water and it is kept liquid at the tem-
perature of the atmosphere.
Certain delicate works require only a slight concen-
tration in the solution of glue. For example, if it be
required to fix crayons, by Loriot's process, six or eight
deniers, or from 150 to 200 grains of fish glue, ren-
dered soluble in 16 ounces of pure water, which is still
diluted with two parts of alcohol at the time of its ap-
plication, will be sufiitient to give the proper degree of
strength to such works, and to f -e^ ent the powder
from being detached. The evaporation is very much
favoured by the alcohol (spirit of vvine).
CLUE FROM PARCHMENT. -Ï'S^,
GLUE OF THE SECOND QUALITY.
-ijrhie made froin glovers' clippings or from parchment.
Put to soak in w?.rm water for twelve or fifteen,
hours clippinr^;^ of parchment, and then boil them for
five or six hourc. : strain the whole through a piece of
open linen or throujh • a hair sieve to separate the
membranous portions deprived of their gelatin. Leave
the decoction r.t rest and it will soon condense into a
jelly. If the decoction be made in summer, the tem-
perature which keeps the glue long in a state of liqui-
dity gives it time to clarify. The upper part, indeed,
has the aDpearance of tremblincr jeilv, exceedingly clear
and without colour. When the clippings of parcfi-
ment have been v/ell chosen, the whole of the clear
part of the glue, in- consequence of its consistence, hi»5y
be separated by means of -a skimmer from that at the
bottom of the vesseL, the transparence of which is often,
disturbed by bodies that are foreign to pure gelatin. . '
This glue may be employed in -all' cases where great
cleanness is required ; and therefore may be substi-
tuted for fish glue. It is in this state that it ought to
be used for sizing, and for that beautiful kind of
distemper called ckipolin or hlanc cle roi (royal white),
GLUE OF THE THIRD QUALITY.
Common glue.
Painting in distemper will admit, in many cases, a
kind of glue inferior to those of the first two qualities.
All objects comprehended in the distemper applied to
490 TREATISE ON' VARNISHES.
ceilings, walls^ &c., do not require much nicety in the
choice of the matters proper for furnishing the glue.
Under these circumstances solidity is more attended to
,than neatness. Common Flanders glue dissolved in
■water is yery often used instead of that of a finer qua-
lity.
When this glue is to be prerared, take clipfângs of
sheep's sldn, goats* skin, and of parchment, and boil
them for three or four hours in a sufficient quantity of
.water (seven or eight parts in weight for one of matter)-.
When the decoction is reduced to a-third, strain it
through a hair sieve or piece of Hnen : on cooHng it
assumes the consistence of a strong jelly, which may
be w^eakened according to circumstances. In conse-
quence of the consistqice here mentioned this glue is
distinguished by the name of strong glue, a technical
term often employed in the forr^ul^ of different com-
posidons, ^d which cannot be applied to the sti'ong
dry glue sold in the shops. The addition of two
pounds of water will form a mean kiiid of glue ; and
eight pounds of water to the same quantity will give
simply glue: it may still be rendered y/eaker should
circumstances require it.
Glue of this kind must be employed immediately j
because it will not keep more than five or six days ir^
summer, even in a cool place. If the weather is tem-<
pestuous, it will soon corrupt : when it loses its con-
sistence and dissolves into water it has reached the first
term of alteration, and Boon passes to the state of pu=
trefaction. When this change m the consistence of
gliie is observed it caa no longer be used in distemper.
SIZING. 49ï-
Theée different kinds of giue, which differ from
each other only by the greater or less degree of their
purity and colour, may be applied to different kinds of
works, according to their fineness. The first kind is
destined to defend delicate painting, coloured paper,
paintings in water-colours, kc, from the attacks of
varnish. That of the second quality may be used,
yifith. the precautions already mentioned, for the same
purposes. That of the third is employed for common
sizing.
Sizhîg.
The word sizing denotes that operation by which a
solution of glue is spread over articles intended to be
painted in distemper or to be varnished. Size is ap-
plied cold. This stratum of glue fills up the pores of
the wood, paper, &c., and deposits in them a matter
impenetrable to alcohol and to the essential oils, which
serve as excipients to the resins employed in the com-
position of varnishes. If several successive strata of it
be applied it may even serve as a varnish itself; but
jjeing by its nature soluble in water, the least impression
of humidity, that of the moist hands, and the adhesion
of dust, which is the consequence, would soon tarnish
the objects to which it is applied and destroy their neat-
ness and brilliancy, which are their most valuable qua-
lities.
Varnish, therefore, may be applied to this first stra-
tum without injuring the colours and without pene-
trating further ; and if the strata be multiplied, so as to
give to the whole a sufficient thickness, it will bear the
operation of polishing. - • -
499 TREATISE ON VARNISHES.
The varnishes applied in distemper call forth the co-
lours with new lustre. This remark, however, cannot
be generalized without inconvenience, because evei^
kind of distemper does not produce, under varnish,
the Same result. Distemper, the basis of which is chalk,
does not possess this property in its whole extent ; it
becomes brov/n under the first stratum of varriish. This
application of varnish to distemper requires then a
choice in the bases, or in the colouring matters, which
constitute distemper in size. Clay supports varnish
better than chalk ; it also shrinks less ; but the colours
takeii from metallic substances are thoçé v/hich in dis-
temper harmonize best with the splendor of varnish ;
of this kind are ceruse, white lead ground and inixed
up with essence ihi- the first stratum.
ïf I have here specified cases which require that size
should be applied cold, there are others which reqaire
that the jelly employed for sizing should have a certain
strength ; that it should be thick, and consequeiltly
that it should be employed warm ; the last stratum ex^
ceptedj which must consist of weaker glue, if intended
to be covered with varnish.
'. The substances fit to be painted in distemper are
wood, walls, plaster, skins, cloth, pasteboard, paper.
But before I give examples in these three kinds of
distemper, it will be proper to lay before the reader
the preceptij w'hich belong to this kind of painting.
General precepts applicable to painting in distemper.
Distemper is often employed with a view of covering
it with j^ainting which exhibits some particular subject.
Precepts in regard .to distemper. 4^5
In this case it will be necessary, Ist, That the ground
to which the distemper is to be applied should contain
neither grease nor lime ; 2d, That it should be covered,
with some preparation to render tlie surface very smooth.
This preparation is generally made of white,, because
it heightens better the colours, v/hich always borrow
something from the ground ; 3d, That the consistence
of the colour should be such that it may run or drop
from the brush in a thread when taken from the pot.
This condition is contrary to that established, in a
similar case, in regard to painting in oil and in var-
nish. If the colour does not form a thread, it is too
thick, and the work will be in danger of becoming
scaly ; 4th, That all the strata, the h s': excepted,
must be applied warm, taking care, however, that the
.matter does not boil ; for when too hot it injures the
lirst strata and spoils the subject ; and if applied to
wood it may cause it to split. Besides, a solution of
glue exposed to too high a temperatui'e assumes a fat
character, and loses its tenacity. These four condi-
tions, according to artists, form the principal laws of
this kind of painting. .
I shall, however, add a ûfth ; which is, that if the
strata are to be multiplied they ought all to be of an
equal thickness. This equality depends on the strength
.of the glue and the quantity of the matter apphed : if
the strata vary in this respect the painting rises up in
scales.
If the ground to which the distemper is applied con-
tains grease or lime, this inconvenience may he re-
moved, by scraping, in case it be a wall • or by a so-
494^ TREATISE ON VARNISHED.
lution of the carbonate of potash (alkali of potash) if
it be wood; canvas must be cleaned by means of
a ley.
If the -walls destined to receive any subject in paint-
ing be very smooth, a stratum of warm glue is applied
which penetrates into them and disposes the surface of
the stone or plaster to incorporate with the colours.
vBut if they are rough, a coating of Spanish white or
chalk mixed with a soludon of glue is employed to
render the surface smoother. tVhen this coating is
<iry, it is scraped as clean and as equally as possible,
ît may readily be conceived that this operation is ap-
plicable only to small inequaiides; for if they were
considerable or accompanied with holes, it would be
necessary to equalize the surface with gypsum and to
allow the latter sufficient time to assume body, which
will not be the case till it be thoroughly dry.
The improvement made in common distemper, the
origin of Vvhich is as old as the use of badigeon, as
mentioned in the commencement of this chapter, hav-
ing very much extended its utility and diversified the
cases of its appHcadon, it is necessary to establish in
this branch of the art relative distinctions. These di-
stinctions seem to be justified not only by the modifi-
cations which it has been indispensably accessary to
admit into the processes, which must be varied accord-
ing to circumstances, but even by the precautions, the
address, and the experience which this kind of paint-
ing requires on the part of the artist, the success of
whose operation depends entirely on himself.
Painting in distemper tiien is distinguished into three
COMMON DISTEMPER. 491}
kinds; 1st, Common distemper; 2d, Varnished dis-
temper, known by the technical term of chipolin ,
^d, Blanc de roi, or royal white.
FIRST KIND OT DISTEMPER.
Example L
If plain distemper is to be applied to a wall or par-
tition covered with, plaster, some Spanish white or wiiite
of Troyes is thrown into water, where it may be easily
broken and diluted if allowed sufficient time to soak:
the water mnst be diarged with it to satui-ation. A
little charcoal black, diluted separately in some water,
is then added, to correct the too great whiteness, and
to prevent it from becoming yellow. To the water
saturated with white one half of a solution of strong
glue in water is added, exceedingly hot, but without
being in a state of ebullition, and it is then applied
with a brush. The coatings or strata are repeated till
it is observed that the tint has become uniform. This
operation is simple and merely mechanical ; yet it is
not an easy matter for the artist to give an miiforni
tone to all the parts of the work, when the surfaces to
be covered are so extensive as to render it necessary to
have recourse to new mixtures. One of the great in-
conveniences of this kind of painting is, that the effect
of it cannot be seen till it is dry. Care must therefore
be taken to try each mixture on pieces of prepared
wood, having the same tint as the ground, that the
real tint may be obtained.
It sometimes happens also, that when painting ia
496 TREATISE ON VARNISHES*
distemper is applied to surfaces which have been al-
ready painted, the colour refuses to adhere, and ex-
hibits the same phsenomenon as if water were presented
to oil.
In this circumstnnce there are two cases. The first;
is explained by the dryness of the preceding stratum ;
an effect arising from the chalk. It rarely occurs with
Spanish white, and never with ceruse or white lead.
The difference in the strength of the solution of strong
glue, employed for the two strata, is a second cause
of this result.
If the sizing of the first stratum be stronger than
that of the second, there is only one method of ob-
viating the inconvenience which takes place ; namely,
the addition of a little ox gall in the new stratum. I
have produced the same effect by an alkaline liquor of
potash; for if the glue be too strong, too abundant,
or too much heated, it assumes an unctuous charac-
ter which the chalk is not able to modify. Spanish
white, or that of Bougival or Morat, will ensure suc-
cess, in consequence of their argillaceous nature.
Distemper, if intended to serve as a ground for any
subjects painted in fresco or in oil colours, requires
another preparation, formed of a more solid substance,
which may give more hold to the colours it is to. receive.
Ceruse will answer this purpose better than Spanish
white, which however is superior to white of Troves.
This application will remove every restraint in regard to
the kind of painting; it may be in gum, in fine dis-
temper, or in oil : this is an advantage which cannot
be expected from an earthy substance.
*> COMMON DISTEMPER. " 497
By this attention, in regard to the choice of the
matters which are to serve as the ground, the paintings
with which apartments are decor-ted wili always pro-
duce their effect, to whatever light they may be ex-
posed; the greater the light, the livelier and more b ^au-
tiful they appear. They participate with crayon- paij ting
in the property of not being subject to those reflecdons
of the light which prevent the beauty of a painting
from being seen, except under a certain point of view,
and in a determinate direction of the luminous rays.
This method holds the first rank among the com-
mon kinds of distemper; but there are many cases
which do not require either the same precision or
very long details. There has lately appeared in the
Décade Philosophique a new process, described by
Cadet-de-Vaux, which this author substitutes for that
of painting in distemper. Though I have r,ot tried it,
the confidence which 1 place in the exactness of a per-
son so well known for his knowledge and zeal in
regard to every object of public utility, induces me to
introduce into this work the formula of his compo-
sition.
In regard to those kinds of distemper employed for
some particular ardcles in the interior part of houses,
I shall content myself with extracting from Watin's
work such examples as may be useful in our method
of buildine;.
2 iv
49S TREATISE ON VARNISHE3,
Example IT,
Painting in milk.
Take Skimmed milk 4 pounds.
Lime, newly slaked, 6 ounces.
Oil of pinks, or linseed, or nut oil, 4 ounces.
Spanish white 3 pounds.
Put the lime into an earthen vessel or into a clean
bucket, and having poured over it a sufficient quan-
tity of milk, add gradually the oil, stirring the mixture
with a wooden spatula; then pour in the remainder of
the milk and dilute the Spanish white.
Milk skimmed in summer is often found to be
curdled; but this is of no consequence for the present
purpose. The contact of the lime soon restores its
■jBuidity ; but it must not be sour, because in that case
it would form with the lime an earthy salt, susceptible
of attracting the humidity of the atmosphere.
The lime is slaked by immersing it in water, from
^'hich it is taken that it may be suiiered to effloresce ia
ihe air.
The choice of the oil is a matter of indifférence :
any of the three above mentiv)ned may be employed ;
but for a white colour that of pinks ought to be pre-
ferred. The mixture of the oil with the lime forms a
kind of calcareous soap ; and in this state the oil i»
.susceptible of an union \^■ith the whole of the ingre-
dients.
The Spanish white is pounded and carefully strewed
PAINTING IN MILK. 499
over the surface of the liquid. It gradually becomes
impregnated with it, and falls to the bottom. This,
process is apphcable to every kind of distemper made
with chalk or with white argillaceous earths. When
the white has fallen to the bottom it is stirred with a
stick. This painting may be coloured, like every other
in distemper, by means of the different, colouring sub-
stances employed in common painting. The above
quantity will be sufficient to give a first stratum to a
surface of 24 square yards.
The author, in his rnemoir, explains the advantages
of this kind of painting ; they are such that no doubt
can remain, in regard to its superiority, when com-
pared with the results of painting in distemper with
size. It is stronger, and does not, like the latter, detach
itself in scales. The gluten which composes it is not
susceptible of decomposition, like the glue or animal
gelatin which gives body to common distemper. The
latter becomes speedily decomposed, and passes to the
acid state by the effect of the humidity which it attracts
and retains. As the colouring body is not then bound
by any gluten, it assumes the form of dust, which is
detached by the least friction.
Besides, this preparation is less expensive, and par-
ticularly in countries where milk is abundant. Jt is
also attended with less trouble, especially as the best
glues from the clippings of skin spass so readily to the
acid state, and lose their strength, independently of the
bad odour which they emit in this state of decompo»
sition, and of the dampness which they maintain in the
walls,
2k2
500 TREATISE ON VARNISHES.
This painting in distemper dries in an hour, and the
oil which forms part of it loses its odour in passing to
the saponaceous state by its combination with the
Hme.
. One stratum will be sufficient for places which are
already covered with any colour, if the latter does not
penetrate through it, and produce spots ; two strata
on new wood ; one stratum on staircases and on ceil-
ings.
The author does not confine this composition to dis-
temper alone : he applies it also to painting in oil,
which he calls resinous paiiiti/ig hi milk^ and which
he employs for external objects. As this composition
forms neither common distemper nor oil painting, I
thought it improper to separate them.
Resinous paintbi g in milk.
For painting external objects, add to the preceding
composition for painting in milk:
Slaked lime.
Oil, >of each 2 oanceSo
}
White Burgundy pitch, J
Put the pitch* into the oil which is to be added to
the liquid milk and lime, and dissolve it in a gentle
heat. In cold weather the milk and lime must be
warmed, to prevent too sudden a cooling of the pitch,
and to facilitate its division in the milk and lime.
It appears to me that time alone can determine
whether tliis kind of painting be as durable as oil.
4
paiîn'Ting for fire-places. 501
painting ; for the shrinking, to which certain strata
of painting on wood are subject, depends in a great
measure on the nature of the wood. At Geneva, the
fir wood employed for constructing works exposed to
the influence of the air is not equally proper for paint-
ing in oil. That of Savoy is porous, splits in the air,,
and is more subject than any other kind to be eaten
by worms. The stratum of painting applied to it de-
taches itself in scaly leaves. The Burgundy fir is more
compact and more resinous, and the resin it contains,
by forming a ground to the painting, contributes to its
solidity and preservation. It is always smooth and
firm, and has not the inconvenience of yielding to the
influence of dryness and moisture, which is always less
observed in wood of this kind than in that which is
exceedingly porous. The latter kind of painting may
be substituted for badigeon^ which will be described
as the fourth example of painting in distemper.
Example III.
raiiitiiigfor tJieJlre-hlaces and hearths in kitchens, &c.
The Genevese method.
The Genevese employ a kind of stone, known under
the name of molasse, for constructing fire-places and
stoves, after the German manner. This stone is brought
from Saura, a village of Savoy, at no great distance
from Geneva : it hr.s a grayish colour, inclining to
blue, which is very agreeable to the eye. This tint is
similar to that communicated to common whitewashing
with Hme, chalk, or gypsum, the dullness of which
2 K 3
502 TREATISE ON VARNISHES.
is corrected by a particle of blue extract of indigo, or
by charcoal black.
Very fine beds of pretty pure clay, the colour of
which is exactly similar to that of the molasse of Sura,
has been discovered at Y voire, another village in Savoy:
it is employed by the scr/ant maids to scour out or
conceal the spots of grease or of charcoal which some-
times stain the hearths or chimney-pieces in kitchens.
They keep by them some of this clay mixed up with
a little water, and apply it with a brush destined for
that use after the stains have been rubbed with a frag-
tnent of the same stone. This is a kind of plain dis-
temper without size.
Some whitewashers have lately conceived the ex-
cellent idea of employing this clay in their distemper
for articles much exposed to be dirtied ; such as
kitchens, workshops, &c. They treat it with a solu-
tion of glue, as in the first example. The tone of its
colour, which is always uniform, presents one ad-
vantage not found in artificial mixtures, the true tone
of which cannot be known till the stratum is dry. In
this case, therefore, the operator proceeds with more
certainty, and avoids those repeated trials which are
inevitably necessai*y to obtain an uniformity of tint
when new mixtures must be made to complete the
work. Besides, servant maids, by the daily use of
this clay mixed up with water, are enabled to wipe out
stains and repair other accidents which may alter the
uniformity of a stratum of this distemper.
Clay of a bright gray colour is very commofi. It is
even so rich in variety of shades, that it may be of
1
PAINTING FOR FLOORS. 503
great use in families who wish to imitate this part of the
cleanliness of the Swiss. The advantage they might
derive from it would not be confined merely to gratifi-
cation of the eye. The first step towards an improve-
mient in the convenience of domestic life soon leads to
attempts towards other objects; and it is in this manner
that people, without any direct design, and even with-
out perceiving it, remove from their habitations every
thing that might alter the salubrity of them. The bene-
ficial effects which result from continued care, in re-
gard to every thing that tends to promote cleanliness,
are too apparent not to be observed and to be justly
appreciated. Diseases which become epidemical in.
certain districts in our neighbourhood, and which
often occasion great ravage, seldom appear among us
with the same malignant characters. Cleanliness, I
may even say minute attention to cleanliness, both of
furniture and persons, together with sobriety, is the
best preserver of health. This observation is not foreign
to a subject which treats on the best method of giving
elegant simplicity to the interior of houses.
Example IF",
Distemper for parquets or floors of inlaid work.
The use of parquets^ properly so called, or those
combinations of oak and walnut-tree which produce so
good an effect, is not very common in Swisserland, and
those which exist admit only of waxing. The name
of parquets is given to boards of fir intersected by
pieces of walnut-tree j or disposed in compartDients of
2 K 4
j^d^ ^ ■ TREATISE ON VARNISHES.
whrGli tiji; walnut-tree forms the frame or border'* ;
but tQ,âfich works no other lustre is comrriunicated
than, '^kt which they receive from wax, ar d from
beiiîg frequently cleaned. Some jfloors have been exe-
cuted of plaster, on which the lemon yellow colour
destined for parquets of oak produces a vei"y good
dFect.
To obtain this colour, boil in Î 6 pounds of water
half a pound of yellow berries, and as much terra
mérita and bastard saffron; add to the mixture four
ounces of sulphate of alumine (alum), or carbonate of
potash, which is preferable ; and having strained the
whole through a silk sieve, add to the strained liquor
four pounds of water charged with a pound of Flan-
ders glue.
Apply two strata of this colour with a brush, and
when dry wax it, and polish tiie surface with a rubber.
In this preparation nothing is sought fcr in the
bastard saffron but the colouring part soluble in water :
thai which is soluble in the alkali passes partly into the
bath, if carbonate of soda (potash) has been employed.
But as the addition of an acid would be necessary to
make the latter appear, its effect in this case is scarcely
perceived: it contiibutes, however, to the solidity of
the tint.
Example V.
Red for corridors and halls paved ivlih tiles.
A brush dipped in the water which comes from a
common ley, or in soapy water, or in water charged
•■■^ Some of the floors in France and other countries on the con-
tinent are constructed in tliis manner. — T.
RED FOR FIALLS PAVED WITH TILE
s. /■ •:^dêj\.
Avith a twentieth part of the carbonate of potasi {alkali
of potash), is in general drawn over the tiies.y- This
washing thoroughly clearis thein, carries oiF the g(^asy
spots, and disposes all the parts of the pavement^^-tp
receive the disiemper. They are then left to dry.
On the other hand, dissolve in eight pounds of
"water half a pound of Flanders glue, and while the'
mixture is still in a state of ebuilidon, add two pounds
of red ochre, mixing the whole with great care. Thea
apply a stratum of this mixture to the pavement, and
suffer it to dry. A second stratum is applied with
Prussian red, mixed up with drying linserd oil, and a
third with the same red, mixed up with size. When
the v/hole is dry rub it with wax.
Such is the m? thod generally employed ; and this
succession of strata is attended with peculiar advantages.
The lirst ley, penetrating into the tiles, forms a ground
of adhesion to the second ; and the last receives^ from
the second a great deal of solidity, and prevents the
slowness of the desiccation of the stratum with oil,
which would adhere to the feet or be rubbed oft by the
scrubber, were it not entirely dry. The third stratum
may be dispensed with, if pulverized litharge be mixed
with the colour, which will then become more drying.
I have shortened the . operation very, m.uch by i;ed-
dening the new tiles with a preparation composed of
the serous and colouring parts of ox blood, separated
in the slaughter-house froin the fibrous part. This
preparation is exceedingly strong. If a single stratum
of red bole, mixed up with drying linseed oil, be then
applied, it may soon after be waxed and rubbed. This
^06 TREATISE ON VARNISHES.
applica&on is solid, and costs less than the fonner. I
have gfeen, in a house inhabited for tliirty years, the
floor of a hall painted in this manner, where the co-
lour still retained its lustre without being ix}. the least
diminished.
I have communicated a very beautiful red colour
also with a bath of alumed madder. A pound of
madder coarsely pulverized, four ounces of alum, and
tweke pounds of water, are sufficient for this prepa-
ration. Two strata of it are applied to new tiles, after
larhich it is waxed and rubbed.
This application produces a very fine effect j but it
K not so durable as the preceding.
Example VL
Distemper in Badigeon,
Badigeon is employed for giving an uniform tint to
houses rendered brown by time, and to churches when
it is required to render them brighter. Badigeon, in
general, has a yellow tint. That which succeeds best
îs composed of the saw-dust or powder of the same
kiùd of stone and slaked lime, mixed up in a bucket
of v/ater holding in solution a pound of the sulphate
of alumine (alum). - It is applied with a brush.
At Paris, in the nei'ghbourhood of that city, and in
other parts of France, where the large edifices are
constructed of a soft Idnd of stone, which is yellow,
and sometimes white, when it comes from the quaiT)^,
but which in time becomes brown, a little ochre de
Tse is substituted for the powder of the stone itself,
BADIGEON. CHIPOLIN. 50Y
and restores to the edifice its oHginal tint. But, at
Geneva and Lausanne, and in the neighbouring cities,
where buildings are constructed of molasse, a kind of
soft freestone, the tint given by ochre de iTie would be
different from that intended. We are indebted to one
of my fellow-citizens, the late Lagrange, for a method,
both simple and effectual, of giving to old edifices Z
new appearance, and of reviving their original tint :
it is adapted to the nature of the stone. Nothing is
necessary but to rub the surface of the edifice with
pieces of the same mola'^se, taking care to select the
hardest : by this process the stone will acquire its for-
mer colour. It was employed at the time of the repa-
ration of the church of St. Peter, our cathedral, forty
years ago ; and the state of that edifice still attests that
none better could have been used.
SECOND KIND OF DISTEMPER»
Example I,
T^arnished distemper, Chipolin,
Painting in distemper covered with a varnish callel
chipolin* and royal white, which vAW furnish an ex-
ample of the third kind of distemper, is the most
elegant of this sort ; but the preparation it requires
renders it very expensive. It is to chipolin that we
* The origin of the word c/tzpoZw is very uncertain. On this
subject there are two opinions, which seem to have the same de-
gree of probability. Some think it is derived from the resemblancç
observed between this kind of painting, when well executed, and
cipolin or chipolin marble, in regard to tlie pearly or talc-like bril^
liancy which it acquires and retains when well polished. The first
508 TREATISE ON Vx^-RNISHES.
are indebted for those brilliant decorations in varnish
applied to candelabra with delicate sculpture, the ar-
gentine white of which, set off with pale gold, pro-
duces such beautiful effects by reflected light ; but this
truly noble Idnd of painting, in consequence of the great
labour it requires, is reserved for valuable furniture,
and for ornamenting apartments in palaces.
The eye dv/ells with pleasure on chipolin which has
been executed with ingenuity and taste. The vanity of
man ought to smile at the sight of those superb apart-
ments where the splendour of the painting, heightened
by the pale gold which combines so well in this species
of it, attests at the same time the pov/er of the owner
and that of the arts, which subjects the sovereign
.himself to that tribute which they impose on taste and
love of the beautiful.
Besides the splendour which this kind of painting ac-
quires under the influence of the light, it possesses the
property of keeping apartments cool. This effect,
which would be produced by marble, must result also
from chipolin. Being composed of very fine parts,
-\rhich a state of solution brings into perfect contact,
and whose adhesion is very much increased by the glu-
tcrij which gives them a very great consistence, its tex-
ture cannot be very much different from that of marble.
ripolin^ perhaps^ v.ns only an imitation of this marble, and exhi-
bited those greenish veins with which it is cniriched and ornament-
ed. Others suppose that this denomination originated from the
use which tlie first painters in this branch made of tlie juice of
onions, applied by way of preparation. Were I called upon to de-
«Ide this question^ I should declare in favour of the lirst opinion.
CHIPOLIN. 50^'
I have seen chipoliii employed in the decoration of
altars, which was harder than marble with crystal-
lized grains. The latter is more susceptible of being-
scratched.
Though this kind of painting is not frequently em-
ployed, I think it necessary to give the reader a sufn-
cient idea of it, by a short account of the process, as
described by Watin in his PaTfait Ferm'sseur ; but I
shall remove the veil of mystery which he throws over
the composition of the varnish he would employ, were
he to undertake chipolin. The following is the order
adopted in the distribution of the labour for argentine
white chipolin. In regard to further details, the reader
must recur to the work above mentioned :
. 1st. Wash the wainscoting with a warm decoction
of absynthium, to which a few heads of garlic are
added. Mix this decoction with parchment glue, which
when cold assumes the form of a jelly. This process
opens the pores of the wood, and disposes it to aiibrd
the means of adhesion to the following strata.
2d. A stratum of warm glue vt^ith Bougival or Spa-
nish white, which will give the w^ork more solidity.
White of Pvîorat may be substituted for that of Spain.
3d. Eight or ten strata of the same v/hite, well mixed
and exceedingly fine ; taking care to preserve the saine
degree of strength and the same thickness in each
stratum. But care must be taken at the same time not
to choke up the mouldings, and to apply the last stra-
tum with glue somewhat thinner than that used in the
preceding strata.
4th. Soften the surface with pumice stone, to w^hich
SîO TREATISE ON VARNISHES.
such a form has been given that it can be introduced
into the small cavities of the mouldings and sculpture.
Employ small sticks of different shapes to polish the
mouldings and the plain surfaces. The process of po-
lishing may be shortened by drawing immediately over
tlie work a soft brush dipped in water.
5th. Clean the cavities of the mouldings and sculp-
ture with small iron instruments prepared for that pur-
pose.
6th. After these preparations apply two strata of
colour made of white oxide of lead, to which a particle
©f prussiate of iron and black has been added, and
mixed up with parchment size, strained through a sieve
to separate the portions of size still granulated : these
two strata must be softened with the brush.
7th. Apply two other strata of thin glue, beaten up
cold, and strained through a sieve, to separate the por-
tions of jelly not diluted. They are apphed cold, care-
fully softening the work, that there may be no need of
passing several times over the same place.
8th. Apply, with the same precautions, two or three
strata of the varnish No. 2. of the first genus, or of
No. 14. of the third; and keep the place warm, to fa-
cilitate evaporation and desiccation before the dust can
adhere to it : the work will then be completed. Such
\s the process for this preparation, which requires eigh-
teen or nineteen strata, and a great deal of care in the
execution. It is needless to remind artists of the prin-
ciple already laid down, that a mau stratum ■mmt 7iot
be applied till the preceding be dry. When the chipo-
Jili is destined for pieces of sculpture, it is customary-
IMITATION OF CHIPOLIN- ^îl
to heighten its splendour by that of gold, which is ap-
plied and left unbumished on all the salient parts of
the work. This addition increases in a singular manner
the richness and magnificence of this Idnd of deco-
ration.
The author, who gives a more circumstantial detail
of this labour, points out a method which was known
to painters before the publication of his work, and
which they employed with modifications, according ta
local circumstances, and to the time and expense which
they were willing to sacrifice. This method is much
shorter than the former, since it enables artists to imi-
tate chipolin by an operation which requires onlj
twenty-four hours : it will form the subject of the se-
cond example.
Example IL
Imitation of chipolin,
Watin prescribes two strata of size made of Spanish
white, mixed up with strong parchment glue, hot, and
even in a state of ebullidon*.
* The application of size so hot swells the wood and retards the
desiccaiion. The wainscoting, indeed, at Paris, and in the neigh-
bourhood, is of oak, and tliis wood is less liable to swell than our
fir at Geneva. I should apply the first two strata in tiiis caseivith
ceruse of the first quality : the tint is solid, and calls forth the co-
loured strata equally well. They ought to be applied witli essence.
Over tliese two strata I would apply two others of colour mixed
up with pretty strong glue, kept liquid, and would polish after the
first coloured stratum. These ought to be covered with two strata
of varnish of the first class, or the varnish No. 14. of the tliird^ or
the colour should be aiixed up with the varnish.
Sl^ TREATISE ON VAP.NIStlES.
The desiccation is accelerated by nmiiitaining a fire
in the apartment which has been varnished, if the sea-
son be unflivourable.
"When the second stratum is dry, rub it with pumice
stone to equalize and smooth the surface, and apply
three strata of colour. If an azurey gray white be re-
quired, mix with great care on a porphyry slab one
ounce of ceruse, one gros of charcoal black, and as
much prussiate of iron (Prussian blue). Take a por-
tion of this mixtur»e, and grind it slightly on the por-
phyry stone with the ceiTise which is to compose the
colour, adding the latter in portions, that the ingredi-
ents may be better mixed. When this first division is
effected, sift the v>diole through a silk sieve to complete
the mixture.
Then add four ounces of this preparation to a pound
of varnish , and mix them with a brush. The varnish
proper for this purpose is No. 1 . of the first genus. It
will be proper not to mix up more matter at a time,
because the varnish evaporates. Extend it in as uni-
form a manui^r as possible, and when the stratum^ is
dry, rub it v/ith a strong new piece of , linen cloth to
polish it. This friction, which at first requires consi-
derable care, completes the desiccation of the varnisli,
and glazes it. For the second stratum take only one
half of the powder, and mix it up in the same quantity
of varnish as for the first ; and for the third olily half
an ounce of powder. If you are desirous of giving
lustre to the v/ork you must add a fourth stratum, not;^
more charged with colour, than the third. Then ru^b
l;he surface with a cloth, to give it that splendour which
ROYAL WHITE. î:^''" ' 5î3-
always results from a perfect uniformity in the extension
of the varnish.
This is the method which I have always employed in
painting in distemper, and I recommend it for colours
of every kind applied to wainscoting of white wood,
which is too much liable to swell under size of every
kind, and which renders the first preparadon scaly.
THIRD KIND OF DISTEMPEPv.
Blanc de roi. Royal 2chite.
This kind of distemper takes its name from the use
made of it in decorating the interior of palaces. Royal
white is very much employed, and is easily executed,
when not intended to be covered with varnish : when
fresh it is exceedingly beautiful. It is attended with
the fault of becoming soon spoiled in apartments con-
stantly inhabited, and particularly in bed-rooms, because,
not being defended by varnish, the exhalations and other
vapours which emanate from living bodies react on
the white oxide of lead, and make it first turn yellow
and then black. It is employed chiefly for saloons,
where the mouldings and carving have been orna-
mented* with gold, the paleness of v/hich is richly set
off by the splendour of the colour. It is not customary
* TJie author here makes use of the word rechampir, which, in a
note, he says is a term of art tliat signifies to contrast one colour
with another. He adds, that it must not be confounded witli the
term rehausser d'or, which expresses painting of a gold colour on
canvas, either in oil or distemper, and which represents piece»
«f sculptiyre^ bas reliefs. Sec.
2 L
514 TREATISE ON VARNISHES.
to varnish white grounds when accompanied with gild-
ing and beautiful ornaments.
In painting royal white, it will be proper to form, the
ground with a stratum of Spanish white, or white of
Morat, mixed up with strong parchment size, and
applied in a state of ebullition ; paying attention, how-
ever, to the nature of the wood, as already remarked.
It requires the same operations as chipolin ; but private
individuals generally dispense v/ith this nicety of execu-
tion, which would require long time, and occasion very
great expense. On this account I shall refer to the
processes already detailed, in regard to the execution
of azurey grayish white chipolin, which furnished the
second example of the second kind of distemper.
(Seep. 512).
To render it very beautiful, white oxide of lead
ought to be preferred to ceruse ; and the insipidity of
the white should be heightened with a small quantity
of prussiate, of iron or of indigo, in the same dosés
nearly as for pearl gray chipolin. Polishing with a cloth
produces a very good effect ; but the beautiful reflec-
tion of the light depends as much on the m.anner in
which the last strata are applied as on the polishing
which completes the smoothing of the surface.
In our happy country (Swisserland), where the luxury
of apartments is confined within certain bounds which
individuals never pass, where the citizen consults neat-
ness and cleanliness rather than pomp and splendour,
people are contented with the simple composition of royal
white, heightening its dullness with a little prussiate of
iron and black. This kind of painting is reserved, in
ROYAL WHITS-. 515
particular, for the upper apartments of country houses.
Its solidity renders it superior to that with white of
Troyes. But all white oxides of lead are attended witJi
the inconvenience of experiencing veiy sensible alter-
ations in their colour at the end of a certain number of
years, which renders it necessary to repeat the applica*-
tion of white in bed-chambers, or to cover them with
varnish. The splendour given by this addition, and
the easy means it affords of guarding against the perni-
cious effects of dust, are real advantages which coun-
terbalance the expense.
Besides, though this preparation seems attended with
no insurmountable diiiiculty, even to the amateur, it
requires in the artist who ujidertalces it good taste, care,
and practice. Royal v/hite, indeed, is not always pre-
pared with that care and attention which render it va-
luable. A skilful eye is often shocked to see the out-
lines of well executed wainscoting disappear under the
unequal and too thick daubing of the strata, in which
Vv^hite of Troyes even is often substituted for ceruse.
As this deception is frequently practised, people ought
to be on their guard against it. The employer, who has
a double interest to defend, may put the honesty of the
artist to the test by a very simple experiment. Place
on charcoal a small quantity of the white matter wjiich
represents ceruse ; if it be chalk, it will become brown
when you blow the charcoal ; but if it be ceruse, it be-
comes yellow, changes to a red colour, and is soon re-
duced to lead. This revivification of the lead is speedier
when the fire is urged by a blow-pipe.
2l 2
516 TREATISE ON VARNISHES.
Such are the resources which society derives from the
combination of colours and compositions, the variety
of which produced by diversity of tastes develops
under the hand of the artist very powerful means, which
have the threefold advantage, of adding new branches
to national industry, gratifying the wants of indivi-
duals, and multiplymg, at their pleasure, the enjoy,
ments of life.
C 517 ]
CHAPTER YI.
ùfthc inslruments necessary in the art of varnishing : olserr
rations on the use of some of them.
It is generally believed, and without much examina-
tion, that the art of the painter requires more practice
or experience than funds. A palette destined for the
distribution of the colours, an easel to maintain the
pictures at different heights, a rod to support the
hand which directs the pencil, a few casts to serve as a
guide in the drapery and different attitudes, bmshes,
and a brush-holder, are, it 13 said, the whole apparatus
of the painter.
A good education, an extensire acquaintance with
antient and modern history, as well as mythology, great
knowledge of the world, a certain ea^e of circum-
stances capable of maintaining independence during the
long period of study, and of fcicilitating travel, that he
may familiarize himself with the beautiful models of
antiquity, to correct his taste, and to fix it on the true
beautiful and sublime kind of composition, and to enable
him to acquire correct ideas respecting every species
of painting and in regard to human nature, and in
particular genius, are the requisites nccessaiy to consti-
tute a great painter. Genius unites the great painter
with the great poet, and conducts them to the same end
by different routes. The one captivates our senses by
warmth of colouring, judicious arrangement, and cor-
2 L 3
518 TREATISE ON VARNISHES.
rcctness of design; the other seizes on the mind, and
conducts it by the magic, the delicacy and elevation of
his thoughts, and by the harmony of his verses. Venus
displays as xnany graces luider the pencil of Apelles as.
under that of Homer.
The scarcity of great painters proves that great ta-
lents arc necessary to arrive at celebrity; a point to
which all artists of every kind ought to direct their
aim.
The house-painter and varnisher participates with the
former only in the term which serves to denote his
profession. The functions of the latter are different.
He pursues an occupation merely mechanical, which,
requires only a certain, degree of dexterity, taste, and
experience. The former composes a great deal and
consumes very little; the latter consumes much and
does not compose at all, unless he adds designing to
his art, which consists merely in a simple application of
colours.
In cities of a certain extent the painter and varnisher
ÎS a dealer as well as an artist. For the most part he is
pro\'ided with varnishes and colours of different .kinds,
suiîlcient for all the uùdertakings that may be offered
to him, and to satisfy the demands of amateurs. The
state of the p2iinter and varnisher, considered in this
point of view, requires a certain stock which does not
'«idmit of his being confounded with those workmen
who confine their talents to a mere application of co-
lours, and who purchase them as they are used.
The painter who composes his own varnishes, wha
INSTRUMENTS USED IN VARNISHINC. 519
manufactures his own colours, and who appHes them,
requires for his business a situation in which two essen-
tial conditions, extent and dryness, must be united.
In consequence of the first condition, the premises
must be accompanied with a court or yard for the com-
position of the varnishes, in order that he may be pro-
tected, as well as his neighbours, from the damage
which may be occasioned by negligence or other causes.
The second condition relates to the care necessary <-o
be employed in preserving the colouring matters, which
are easily altered by moisture.
Whatever may be the dryness of the matters at the
time of their preparation, there are some, and particu-
larly substances of an earthy nature, and metallic oxides,
which imbibe the moisture of the air, and even with
great avidity. This moisture is not hurtful to metallic
colours, when destined for distemper; but when in-
tended for painting in oil or in varnish, the case is
different. It injures the splendour of the colour ;
and this effect is more sensible with varnish than with
oil. ^
Moisture prevents perfect contact betweeri the co-
louring part and the excipient. With the concurrence
of the air disseminated among the moleculas of the co-
louring part, it produces that immense quantity of air
bubbles which covers the surface of a colour when
mixed up with oil. If the colour is mixed with varnish,
this humidity precipitates a part of the resin w^hich is
the basis of it : the colour then granulates, runs into
globules under the pencil, and breaks the contact in
such a manner that it becomes as it were mealy. It
2l 4
520 TREATISE ON VARNISHES'.
cuts or changes the reflections of the light, and seems
to tarnish its splendour.
But, iis it is not always possible to obtain a situation
according to one's wishes, great care and attention must
be employed to preserve these compositions from hu-
midity. They must, therefore, be kept in boxes of
hard wood, such as oak or walnut tree; for white wood
is a real hlter to moisture. The same end may be ac-
complished by shutting them up in glazed earthen ves-
sels with a large aperture. These vessels may be easily
shut by cork stoppers covered with parchment.
Liquid substances requh-e to be kept in glass or stone
ware. Varnishes are kept in large strong glass bottles
with a wide mouth, for the convenience of taking theni
out ; but as light has a powerful influence on thesff
compositions, and renders them thick, I would recom-
mend wrapping up the bottles in sheep's skin or moist
parchment, folding it. round the neck, and tying it with
several turns of packthread. This addition is attended
with the double advantage,, of guarding against thé in-
fluence of light, and of preventing those accidents which
result Ironi blows.
Drying oils are less delicate than varnishes made with
alcohol or essence. They may be preserved exceed-
ingly well in stone-vv'are jars, in large bottles, or in
leaden vessels with a wide mouth. Leaden vessels are
;iot liable to those accidents which are most to be appre-
hended ; and if this advantage be not sufficient to make
them be preferred, tliey possess another well known
and consistent with theory, which is, that they add to
ÛiQ drying qualit)^ of the varnish.
THE LABOP.ATORY. 521
A table, weights, and scales, and a few boards to
form shelves, are all the utensils necessary for the work-
shop of a painter and varnisher.
Of the laboratory ; and instruments necessary for the
labour.
The expense of fitting up a laboratory to furnish
articles for common consumption will be very small.
However, if to the making of varnish the preparation
of different coloured lakes be added, it will be some-
what greater. The instruments indispensably necessary
are :
1 St. An alembic, constructed according to the prin-
ciples explained in the first part of this work, with a
refrigerator and portable furnace.
2d. A few bottles for receivers, that is to say, of a
pretty large capacity, with different funnels of glass and
of tin plate.
3d. Two or three copper basons of different sizes,
according to the extent given to the establishment.
4th. Vessels of earthen ware to receive the varnish,
which is strained through a cloth, and to contain the
first deposit.
5th. Pieces of board of the same diameter as the
earthen vessels, to serve them as covers. They are
more convenient, and not liable to be broken like the
earthen-ware ones commonly employed.
6th. Large glass jars furnished with funnels, and the
latter with covers, for filtering the varnishes of the first,
second, and thii'd genera. (See the figure Plate V.}
522 TREATISE ON VARNISHES.
7th. A cast iron pot, polished in the inside and fur*
nished with a cover, for making varnish of the fifth
genus.
8th. Different spatulas of wood, rounded afthe end,
9th. A shovel and a pair of tongs.
10th. Two or three furnaces, of different diameters,
And in particular a small one with a sand bath.
1 1th. A small iron hooped tub with handles to con-
tain charcoal.
1 2th. An iron capsule, or small vessel with a short
handle to take out the charcoal.
13th. Some glass matrasses of different sizes, for
the immediate preparation of alcoholic varnish ; which
is effected by immersing the matrass into a bason, the
w^ater of which is raised to different degrees of heat up
to that of ebullition.
14th. A fixed table, some small tables, and a few
jboxes.
1 5th. A flask filled mth spirit of wine to prevent
the consequences of burns.
If alcohol be applied the moment the accident hap-
pens, it prevents the rising of blisters, which retard the
cure. If the burn be considerable, the apphcation of
fresh oil of eggs, and that in particular of a beautiful
,y.ellow colour, is the best topic to allay the. pain and
to promote a cure. Simple cerat, composed of one
part of yellow wax and two parts of good olive oil, or
of three parts in winter, produces an effect which may
be compared to that of oil of eggs, and is less ex-
pensive.
The i-aboratory. 52Ss
• 1 6th. An iron mortar of from twelve to fifteen inches,
in diameter, with an iron pestle. A slip of brass for*
taldng the matters from the bottom of the mortar, and
an iron spatula for detaching the matters which often
adhere to it in consequence of the contusion.
17th. Two or three pestles of hard wood, with pretty
large heads.
1 8 th. Different sieves of hair and silk. The latterv
oueht to be close.
o
1 9th. Some small iron bullets for the pulverization^-
of bodies which are apt to form tliemselves into a paste
Certain substances, such as indigo and the argillaceous
oxides of iron, are easily pulverized with bullets.
20th. Troughs of plaster for drying lakes.
21st. A frame two feet in length, and from eigh'^
teen to tv/enty inches in breadth, for receiving the fiU
tering cloth, when you are desirous of separating the
water from the composition of lakes. The cloth charged
"viith the sediment is removed to the plaster dryers, oE'
to nev7 bricks, v/hich absorb the greater part of the
water contained in the sediment. After each operation»
the dryers or bricks must be exposed to the open air
to diy them, and to render them proper for their first
use.
22d. Wooden boxes, and a few tubs of different
sizes, for washing and precipitation on a large scale.
23d. A porphyry slab, fixed on a table or stand,
furnished with a drawer, containing mullers or grind*
Ifig stones ; spatulas of iron, horn, or steel.
The stones employed for the extreme division of th«
colours vary in their nature,' Some employ the hardest
s524 TREATISE ON VARNISHES.
marble ; others brèche rock, and, in short, the hardest
that can be found. The Itahans use porphyry, a very
hard kind of stone, which was exceedingly common,
in the time of the Romans. Some beautiful pieces of
it are still found, from two to four feet square ; but
when of this size they are very dear.
24th. One or more flexible knives, called palette
knives ; spatulas of ivory or bone, and some leaves of
horn.
25th. Some vessels of tin plate, for contaim'ng the
ground colours.
^6th. Brushes and pencils of different kinds.
There are several kinds of brushes. Some are com-
posed of badger's hair. They are sometimes made of
à flat form, and are then called varnishingi brushes.
Others are made of goat's hair, or of the fine bristles of
swine, or of the wild boar. They are affixed to sticks
of greater or less length, according to the purpose for
which they are intended. When these pencils are large
they are called brushes, and are employed for the
strong parts of the work. Pencils are made also of the
hair of the martin, of the very pliable hair of children,
and of swan's down. The last are fixed into the barrel
of a quill, and are used for delicate kinds of painting.
The use of brushes or pencils is not limited to one
idnd of painting. In general, they are employed in
^different branches of it. Artists who have much em-
ployment assign a brush to each colour : they take
•care to wipe them when the work is done, and to pre-
ser\'^e them by covering them with water. Amateurs
a.re not under the same necessity of applying them to
v3
THE LABORATORf. 52.5
particular colours, or of preserving them in this man-
ner. One brush often serves thern for different colours,
if they take care to wash out the first colour before the
brush be dipped in another. This may be easily done,
if each brush be washed in the liquor suited to that
which has been applied in painting. Water easily se-
parates every colour in distemper, and essence of tur-
pentine all those which have been mixed up with es-
sence and with oil. In the first case the pencil is wiped
with a piece of hnen cloth ; in other cases a sponge will
answer the purpose, if it be wTapped round the brush
and pressed strongly with one hand while the brush is
drawn through it with the other.
In regard to those destined for varnish, washing in
alcohol will restore them to their former state, if the
varnish has been made with alcohol. Besides, if the
varnish has been suffered to dry between the hairs, a
few strokes of a hammer or mallet will pulverize and
separate the resin which unites them into a solid mass,
and by these means will restore to them the necessary
pliability.
27th. A vessel of tin plate with a flat bottom and
wide mouth, divided into two parts by a partition. Oil
or essence is put into one of the cavities : when you
wish to clean your pencil dip it in the oil, and press it
between your finger and the edge of the partition, in
such a manner that the oil stained by the colour shall
drop into the empty cavity.^ Painters, from a principle
of cleanliness, employ a small stick, which in this ope-
ration answers the same purpose as the fingers.
S26 TREATISE ON VAkNISHES.
28th. Two palettes, one of walnut or appîe tree,
which has been well ijibbed over with drying oil before
it is employed for holding the colours. The oil is rubbed
in until it refuse to take up any more. This kind of
palette serv'es also for varnishing, if the painter follow
both the professions ; another palette of tin plate re-
served for painting in distemper, in order that it may
be placed on the fire when the size becomes fixed.
Such is the furniture of the workshop of the painter
smd varnisher, who follows all the branches of his art*
The extent which a man of industry never fails to give
to his undertakings, when they are crowned with suc-
cess, may contribute to vary the form and multiply the
ïiumber of the instiHiments which are here considered
as necessaiy. Tiiese circumstances will always depend
on the occasion he may have to facilitate the execution
of processes on a large scale ; but the account here
given of the nature sud number of the utensils consi*
dered as necessary for a painter, can in no case be
thought superfluous. Let a real artist be placed in a
workshop thus furnished, and he will iijid himself at
'itoJossincoiiKiucting his business.
[ 521 3
REPORT
Made to the committee of chemistry of the society at Geneva,
for the encouragement of the arts, on this new treatise on
the art of preparing varnish^ , and of composing the colovrs
mixed up with them.
By M. Senebier.
The art of making and employing varnishes Is of a
very modcr-n date in Europe. If we except China and
Japan, where there is reason to believe that this art was
practised in v«ry early times, we are acquainted with
no nation that used it; and if the antients had any idea
of it, it must have been lost together with the works
which might have revived it. The antient authors make
no mention of it, nor have any images been borrowed
from it by their poets.
"We are ignorant of the etymology of the word var-
nish, Vv'hich soine derive from the Greek word hernice^
supposed to signify amber, and others from vermis ros,
the vernal dew, because it seems to give a shining ap-
pearance to the leaves.
The discovery of varnish might be carried back to
the fourteenth century, which was tlie period of ther
discovery of paiiiting in oil : but it has no resemblance
to varnish ; and if the Chinese and Japanese preceded
us in this art, it was rather owing to their having the
juice of the varnl%h tree^ so well suited to this opera-
tion, than to any researches made on purpose.
4
528 TREATISE ON VARNISHES.
The lustre of the Chinese and Japanese works at-
tracted the attention of the Europeans, and the de-
scriptions given of them by the Jesuit missionaries in-
duced artists to m.ake attempts to imitate them. The
advantages which this art seemed to promise excited
their ardour. A taste for neatness, the necessity of
preserving from moisture various articles of value, the
splendour, lightness, and low price of different kinds
of toys, and the desire of having elegant apartments
and carriages, contributed towards the advancement of
the art of the vamisher. At length the celebrated
Martin, about the middle of the last century, establish-
ed the importance of varnish, by the perfection to
which he brought it in consequence of his employing
amber.
But as it was necessary that the improvement of
chemistry should have an influence on the progress of
the art of varnishing, it is founded on knowledge which
that science furnishes ; as the substances employed in
varnishes have been better studied, they can be com-
bined and applied with greater facility. C. Tingry,
therefore, was sensible of the advantage to be obtained
by subjecting the art of the varnisher to the test of ex-
perience; and the manuscript he has presented to you,
and respecting which you have charged me to make a
report, is the result of this labour.
This art, on the first view, might appear trivial; but
it adds to our enjoyments, lessens the ravage occasion-
ed by time in various objects of value, is interesting to
our commerce and manufactures, and may suggest
529
some theoretic ideas which will not be useless to science.
In describing an art it is necessary that aitists should
be instructed in regard to every thing that belongs to
it ; and that they should be made acquainted with the
matters they employ, the method of using them, the
instruments which may assist them, the dangers to
which they are exposed, the means of guarding against
them, and the care they ought to take to preserve in a
sound state the substances necessary for their opera-
tions. A series of processes minutely detailed might,
no doubt, answer their purpose ; but in this case the
artist would be a mere automaton, exercising his art
in the same manner as the bees make their combs. This
would not be enough at the present period, when
genius, instead of being satisfied with what it possesses,
still aims at improvement. It was, therefore, necessary
that the artist should learn to think ; that he should
find matter for reflection in a rational description of his
art, and in an account of the relation which exists be-
tween the processes prescribed and the principles exhi-
bited to him. Such are the views of C. Tingry in the
present work, divided into two parts : the first of which
treats on varnishes so called, and the second of the
colours used for painting intended to be covered by
these varnishes.
The preceding reflections are applicable in particu-
lar to this art, which abounds with pretended secrets
adopted in workshops. These secrets, if good, retard
the progress of the arts, by concealing the means of im-
proving them ; and, if bad, they injure the artists wixo
2 M
530 TREATISE ON VARNISHES.
employ them. I am almost inclined to wish that these
secrets may be always concealed from the whole world.
This work first contains an useful account of fifty-
seven solid and fluid substances which are generally
employed in the composition of varnishes-, and of
sixty-nine colouring substances often used along with
them. The artist will here find information respecting
their origin, their properties, and their uses, as well as
respecting the adulteration of them, and the means of
detecting it. The author shows also the falsity of some
prejudices adopted by artists ; gives neiv processes for
the rectification of some essential oils, and for freeing
fat oils from their greasy principles. He traces out the
different modifications effected in turpentine by various
methods ; ajid as the arts are more interesting accord-
ing to their general utility, it is satisfactory to observe
here the advantage which might be derived from the
products of the last mentioned substance in regard to
-the service of the navy.
The solid matters employed in tbe composition of
varnishes ought to be more or less transparent ; as it
is necessary that they should form a kind of glazing
on the bodies which they cover. They are ail found
in the class of resinous and gummo-resinous bodies.
The Uquids, for the same reason, ought to be colour-
• less, that they may not lessen the transparency of the
bodies which they dissolve ; they must be volatile, that
ithey may evaporate almost entirely, and free from
every thing that might attract the moisture of the air, in
Drder that they may more easily preserve the bodie? to
senebier's report.
which they are appHed : — of this kind are alcohol, ethe-
reous oils, and some fat oils, which have been render-
ed drying.
It results, then, from the qualities essential to the
substances proper for making varnishes, that a var-
nish is a transparent, dry, brilliant, and permanent sur-
face, deposited by the fluid in which the resinous sub-
stances have been dissolved on the bodies it is destined
to cover, and which speedily evaporates. This defini-
tion may serve to distinguish real varnishes from those
which water seems to form on the bodies on which it
falls, because they disappear with it in the same manner
as the varnishes composed of water charged with gum
or gelatin, and because they have Httle brilliancy and
attract moisture.
As the varnishes made with spirituous and oily fluids,
however, have no resemblance, C. Tingry has formed
them into diflferent genera, and these genera indicate by
their nature the use to which they ought to be applied.
By means of this division he has reduced a mass of
recipes and secrets to a small number of general cases,
which simplifies the art, and enables the artist to reflect
on his operations, and to accommmodate them to the
object he has in view.
The first genus is formed by the alcoholic varnishes:
these are the most drying, and constitute five species,
The;se varnishes have more splendour than solidity ;
they are applied to pasteboard and to wood.
The second genus contains alcoholic varnishes less
dicing than the preceding. They are indebted for this
^property and greater solidity to the nature of the resins
2m 2
5S2 TREATISE ON VARNISHES.
employed : they are, however, applied to the sam*
purposes as the former. C. Tingry observes, in his
remarks on these two genera, that spirit of wine never
becomes charged with a greater quantity of resin than
one-third of its weight. This observation is important ;
because all formulae prescribe a much greater quan-
tity, the overplus of which is mere loss.
The third genus comprehends those varnishes which
change the colour of the bodies to which they are ap-
plied, and those also called mordants. They are more
pliable, mellower, and more solid than the former, yet
equally durable. In these varnishes essence is substi-
tuted for spirit of wine. They are employed for giind-
ing colours and forming grounds. They are applied to
wood and metals, to which they give great lustre. These
varnishes are used for giving to buttons the most brilli-
ant colours, for making gilt leather, and for colouring
articles made oï papier machè. The varnishes applied
to fine paintings are also placed in this genus. Expé-
rience has proved, at Geneva, the excellence ^f that
made by C. Tingry. When he speaks of it, he describes,
with great minuteness, a method of reviving pictures,
Jby cleaning them before they are varnished.
The fourth genus is composed of varnishes made
with copal of an ambery colour, combined with ether
or with essence of turpentine reduced to a certain state.
This genus and the following are distinguished from all
the rest by their solidity.
A very drying varnish, without colour, free from
any bad smell, and which, when applied to metals,
forms a glazing as hard and as transparent as enamel is
4
senebier's report. 533
the kind, no doubt, which best answers the intended
purpose ; and this C. Tingry has discovered, by uniting
copal to ether of a certain degree of concentration. It
has a great resemblance to that made with essence ;
but though the preparation of it is easy and sure, and
though it supereedes the necessity of varnishes of this
Jdnd made with essence, the author shows how to make
the latter with or without an intermediate substance.
As the latter have furnished some curious obseiTations,
I think it my duty to say a few words respecting them.
C. Tingry, in the year 1788, presented to our So-
ciety observations on the solution of copal in essence
of turpentine. He there explained the cause why eveiy
kind of essence is not proper for this operation : he
also shov/ed, that the more essence differs from the
the state of ethereous oil the more energy it has to
dissolve copal ; that its dissolving property, in regard to
copal, is in the ratio of its density ; that essence of tur-
pentine, newly distilled, exercises no action on copal, but
that it assumes tiiis property after it has been exposed
some time to the light ; and that essence of turpentine
dissolves copal at a heat below that of boiling water.
Pie observed that essence is not proper for this solu-
tion, when it deposits an acidulous water ; and that it
gives spontaneously a concrete volatile acid salt, nearly
similar to that formed in certain essential oils which
have been long kept, and which, in my opinion, ap-
proaches near to camphor.
C. Tingry, after long researches on copal, furnishes
nev/ resources to artists to enable them to make this var-
nish and that of amber in a more certain manner^ to
2m 3
5.'34 TREATISE ON VARNISHES»
give them, their ^full splendour, and to avoid certain
processes by which they might be deceived.
This copal varnish, in consequence of its hardness,
may be substituted for transparent enamel : it has
withstood on a box, for a great number of years, the
continual friction of the pocket, though the same fric-
tion has destroyed the metallic ring which surrounded
it. The author, therefore, has opened a new branch
of industry for the manufacturing of foil and of vari-
ous kinds of toys much used, in which transparent en-
amels, far more expensive and more hazardous in the
execution, are employed. In a word, this varnish will
supply enamellers with the easy and sure means of re-
pairing those accidents which happen not only to trans-
sparent, but also to opake, enamel, as experience has
shown in our manufactories.
The last kind of varnish comprehends fat varnishes.
They are exceedingly solid, and dry veiT slowly. They
are made with essential oils, or some fat oils, or with
both these kinds of oil united and combined with amber
or copal. These varnishes are distinguished by their
transparency, their lustre, and their solidity. They may
be applied, with ad^■antage, to carriages, and utensils
"exposed to daily friction, such as stools, waiters, &c.
In treating this subject, C. Tingry shows how to
distinguish diying oils from others, and furnishes new
means for obtaining them with facility, by pointing out
a process for oxygenating them, when necessary.
The varnishes made at present are much superior to
.ihose of China, which are confmed to three colours,
red, yellow, and black \ which require long tedious
1
SENEBIER S REPORT. 535
processes, prejudicial to the health of artists, and
which are never proper for delicate articles. This an-
lient nation may boast of expert and patient hands; but
the Europeans have been guided by genius.
C. Tingry gives general precepts for making var-
nishes on a large scale. He collects every thing that
ought to be expected from a learned chemist and expe-
rienced artist : he details the most successful manipula-
lations, describes the most convenient form of the ves-
sels, and prescribes the most appropriate methods for
the filtration and clarification of the liquors. He makes
known also a new alembic, which has the double ad-
vantage of facilitating the mixture of the matters during
the operation, and of preventing the dangers, so com-
mon and so alarming, which arise from the fire in pro-
cesses of this kind.
The second part of this v/ork treats on the application
of colours. The same order is here followed as in the
former; and a description is first given of the colouring
matters employed in varnishes.
To proceed with certainty in the composition of co-
lours, it was necessary to have some principle to serve
as a guide. This principle the author found in the
fundamental colours, which exhibit the different refrin-
gibility of the rays of light by the prism : and as- each
colouring substance does not always give individually
the required colour or shade, he establishes this colour
and shade according to the effects produced by a mix-
ture of the different rays refracted.
The author then describes the common processes for
the composition of colours, and fixes the cases in which
SS6 TREATISE ON VARNISHES.
they can and ought to be employed, by showing the
method of combining them with varnish.
He here stops to consider the different kinds of lakes
employed in painting ; that is to say, the colouring
fec«las combined with alumine or calcareous earth.
These productions, in consequence of their import-
ance, deserved great attention : but it was still neces-
sary to find out some more certain means than any
before employed of ascertaining the fixity of the colour
of lakes; and these the author has here given.
But as a knowledge of the manipulations employed
in the preparation of colours is not sufficient, the author
describes also the workshop of the vamisher as well as
his operations. He insists, in particular, on the ex-
treme division of the colouring matters used for colour-
ing varnishes, and determines the cases in which the
diiferent varnishes ought to be employed : he prefers
the application of varnish charged with its colour to
transparent varnish extended over a coloured ground ;
because on applying a colour in distemper to wood, it
is injured by being moistened with the size, which
forces the coloured coating to detach itself in scales ;,
but he supposes that wood intended to be varnished is
very dry. The author, however, does not confine
himself to details of tliis kind: he shows in what m.an-
ner the expense may be lessened, without hurting the
beauty of the work ; and thus renders equal service to
•the artist and to his employer.
The author gives also a description of painting in oil,
which he treats with the same care ; determining the
cases in which it ought to be preferred, and pointing
senebier's report. 537
out, according to circumstances, the oils and colours
that ought to be employed, with the method of pre*
paring and applying them.
As waxed cloth and waxed silk are, strictly speak-
ing, varnished cloth and varnished silk, since no wax
is used in the preparation of them, the author makes
them the object of his researches, and with the more
reason as this part of the arts had been entirely neg-
lected by men of science, though it may become a
capital object of commerce. He describes the method
of manufacturing these cloths, which vary according
to the use for which they are destined. He next de-
scribes the method of maldng the celebrated English
court plaster, which is applied to cuts, and of detect-
ing the spurious kind.
This part is followed by numerous details in regard
to painting in distemper. As it is founded on the pre-
paration of glue or size, the author makes known the
different kinds ; establishes the cases in which this kind
of painting may be employed, and describes the different
grounds necessary to be made, according to the colours
intended to be applied to them : he describes with mi-
nuteness the different processes for each method.
The work concludes with precepts to colourmen and
artists in regard to the preservation of the substances
employed in varnishes.
The author appears to me to have treated in this
work the art of the varnisher and that of the house-
painter, &c., in a useful and complete manner. I am
therefore of opinion that it merits the approbation of
538 TREATISE ON VARNISHES.
the committee of chemistry. I even request that the
committee will prevail on the Society for the encou-
ragement of the arts and of commere to thank C. Tin-
gry for the labour he has undertaken, and to beg that
he will suffer the public to enjoy the fruit of his re-
searches, as it must improve the practice of an art,
one part of which is universally employed, while the
rest may produce new branches of industry, or facili-»
tate and render more productive those already known.
ENGLISH AND FRENCH WEIGHTS.
The translator thinks it necessary to inform the
reader, that the quantities of the ingredients in the dif-
ferent formulae given in this work for the composition
of varnishes, &:c<, are expressed according to the old
French denominations. As they could not be converted
into correspondent English denominations without frac-
tional parts, which would have been still more ti'ou-
blesome, and might have occasioned mistakes, he
thought it better to leave them in their original state,
and to subjoin a table of the French pound, with rules
for reducing the French to English troy weight ; but
if weights be made according to the old French stand-
ard this reduction will not be necessary. In many
cases, also, where the ingredients consist of ounces, no
difficulty will occur.
The reader, therefore, is requested to observe that
the old Paris pound, poid de marc, of Charlemagne
contains 9216 Paris grains, which are equal to 7561
Enghsh troy grains. It is divided as follows :
1 pound - - - - 16 ounces.
1 ounce - - - - 8 gros or drams.
I gros . - - - 72 grains.
Sometimes the gros is divided into 3 deniers, and the
denier into 24 grains.
The English troy pound, of 1 2 ounces, contains 5760
English troy grains, and is equal to 702 1 Paris grains*
540 ENGLISH AND FRENCH %-EIGHTS.
The English avoirdupois pound, of 16 ounces, con-
tains 7000 English troy grains, and is equal to 8538
Paris grains.
To reduce Paris grjuns to English troy grains, divide
by 1-2189.
To reduce Paris ounces to English troy, divide by
1 -01 57 34, or the conversion may be made by means
of the following table :
The Paris pound = "7361'
The ounce = 472-5625
The gros = 59-070S
The grain = -8204
If Paris pounds, therefore, are given to be reduced
to English troy grains, multiply by 7561 ; if French
ounces are given, multiply by 472-5625 : the product
will be English grains, and so of the other denomi-
nations.
ERRATA.
Page 83, line 14, for lakcd oils read boiled oils.
119, line 8 from the bottom, for Fint species read Third sprries.
156, line 13, for or read o)i.
207, line 8 from the bottom, for Sixth species read Seveûth specie^'
4^
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en
THE END.
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