(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Biodiversity Heritage Library | Children's Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "The Science of Painting"

Google 



This is a digital copy of a book that was preserved for generations on Hbrary shelves before it was carefully scanned by Google as part of a project 

to make the world's books discoverable online. 

It has survived long enough for the copyright to expire and the book to enter the public domain. A public domain book is one that was never subject 

to copyright or whose legal copyright term has expired. Whether a book is in the public domain may vary country to country. Public domain books 

are our gateways to the past, representing a wealth of history, culture and knowledge that's often difficult to discover. 

Marks, notations and other maiginalia present in the original volume will appear in this file - a reminder of this book's long journey from the 

publisher to a library and finally to you. 

Usage guidelines 

Google is proud to partner with libraries to digitize public domain materials and make them widely accessible. Public domain books belong to the 
public and we are merely their custodians. Nevertheless, this work is expensive, so in order to keep providing this resource, we liave taken steps to 
prevent abuse by commercial parties, including placing technical restrictions on automated querying. 
We also ask that you: 

+ Make non-commercial use of the files We designed Google Book Search for use by individuals, and we request that you use these files for 
personal, non-commercial purposes. 

+ Refrain fivm automated querying Do not send automated queries of any sort to Google's system: If you are conducting research on machine 
translation, optical character recognition or other areas where access to a large amount of text is helpful, please contact us. We encourage the 
use of public domain materials for these purposes and may be able to help. 

+ Maintain attributionTht GoogXt "watermark" you see on each file is essential for informing people about this project and helping them find 
additional materials through Google Book Search. Please do not remove it. 

+ Keep it legal Whatever your use, remember that you are responsible for ensuring that what you are doing is legal. Do not assume that just 
because we believe a book is in the public domain for users in the United States, that the work is also in the public domain for users in other 
countries. Whether a book is still in copyright varies from country to country, and we can't offer guidance on whether any specific use of 
any specific book is allowed. Please do not assume that a book's appearance in Google Book Search means it can be used in any manner 
anywhere in the world. Copyright infringement liabili^ can be quite severe. 

About Google Book Search 

Google's mission is to organize the world's information and to make it universally accessible and useful. Google Book Search helps readers 
discover the world's books while helping authors and publishers reach new audiences. You can search through the full text of this book on the web 

at |http : //books . google . com/| 



THE SCIENCE OF PAINTING. 



THE HORSE. 



BY 

E. DUHOUSSET, 
Lieut.-ColoneL 

A TRANSLATION 

LONDON : 
PERCY YOUNG, 137, GowER Street, W.C. 



\\ '^^^ 



SCIENCE OF PAINTING. 



BY 

J. G. VIBERT 



A TRANSLATION 
FROM THE EIGHTH EDITION, REVISED BY THE AUTHOR. 



LONDON : 

PERCY YOUNG, 137, GOWER STREET, W.C. 

1892. 



f/1 31'ilp-^-^ 



lARVARD 
FINE ARTS 



JAN 24 '00 



^45r P^^,^ 



Books are dedicated to esteetned coileagueSf to adtnired celebriiieSf or 
to illustrious individualSf whose patronage the author thus hopes to 
obtain. 

This book would be dedicated to the Institute of France^ were such a 
dedication permitted to any book. 



TO THE READER. 



The author, at the conclusion of the course of public 
lectures which he gave at the " School of Fine Arts," has 
willingly consented, at the request of many of his hearers, 
to publish his lectures in this book, which he has now the 
honour of placing before you. 

Having no pretension to give to his colleagues lessons, 
or even advice, except for the preservation of their works, 
the author will pass over all questions of beauty of drawing, 
of anatomy, of perspective and of composition, which form 
part of the art of painting, but which have no influence on 
its durability; he will only take up the practical part, or 
what might be vulgarly called the wire-pulling department. 
At the most he will only make some scientific digressions, 
necessary because certain effects cannot be properly under- 
stood unless their causes are known. 

This book, the fruit of thirty years of study and ex- 
perience, is the most serious and honest work which has 
been written on the subject. At least the author thinks 
so ; and he must say so, for should he through excess of 
modesty say anything else, he would not be believed. 

Notwithstanding the qualities which its author believes 
it to possess, will this book have the results which he 
expects from it? 



VI TO THE READER. 

Will it cause painters to adopt a more rational method ? 
May we hope, thanks to it, to see the masterpieces of the 
future preserve their brilliancy and freshness ? 

Of that the author is not quite sure. Not daring to feel 
certain of great success, he will feel himself rewarded for 
his efforts if his book finds one reader from beginning to 
end ; and you as that possible reader he now salutes. 



CONTENTS. 



CHAPTER I. PAGE 

The Process of Painting at Different Periods ... 9 

CHAPTER II. 
Light and Colours 17 

CHAPTER III. 

The Laws of Colouring. 

Mixing of Opaque Colours. — Mixing of Two Colours. — Mixing of 
Three Colours. — Superposition of Colours. — Superposition of 
Transparent' Colours on White and Black. — Superposition 
of Transparent Colours over each other. — Superposition of 
Translucid Colours. — Contrast of Colours by Juxtaposition. 
— Contrast of Black and White. — Contrast of Juxtaposed 
Colours . . . . , 31 

CHAPTER IV. 
With the Scientists 48 

CHAPTER V. 
Colouring Substances 56 

CHAPTER VI. 

Oils, Grinding of Colours, Essences, Petroleums, and Sicca- 
tives 71 

CHAPTER VII, 

Resins and Varnishes. 

Re-touching Varnish. — Painting Varnish. — Picture Varnish . . 84 

CHAPTER VIII. 
Canvas, Panels and their Sizings, Pastes . . .96 



VIU CONTENTS. 

CHAPTER IX. 

OUTUNE AND EXECUTION OF A PiCTURE IN OiLS. PAGE 

Outlines in OiL — Execution. — Repainting. — Glazing. — Embus . I lo 

CHAPTER X.- 

The Preservation and Restoration or Pictures. 

Cleaning 122 

CHAPTER XI. 
Wall Painting 130 

CHAPTER XII. 
Crayons, Distempering, Egg Painting, Water Body-Colours . 135 

CHAPTER XIII. 

Water Colours. ' 

Paper. — Gums. — Fixative. — Water Colours Fixed by Fire. — Sar- 

cocol Water Colours 146 

CHAPTER XIV. 
Conclusion . . 160 

APPENDIX. 

Recipes and Manipulations. 

Good and Bad Colours. — Lead Whites, — Zinc Whites. — Chalk 
Whites. — Earths, Ochres and Marls, Iron Lake, Yellow and 
Orange Colours. — Red Colours. — Blue Colours. — Green 
Colours. — ^Violet Colours. — Brown Colours. — ^Verification of 
Colours. — Cleaning of Pictures. — Varnishing of Pictures. — 
Fixative for Water Colours and Dissolving Liquid. — ^Varnished 
Water Colours. — Repair of little Daily Accidents. — Canvas 
Blistered, Cracked or Broken. — Panels of Unpolished Wood. 
Caseine or Cheese Paste. — Sizings of Caseine Paste and 
Zinc White. — Sarcocol and Sarcocolline. — Gelatine. — Starch 
or Farina Paste. — Albumen. — Dextrine. — Gum Lac. — Water, 
Eggy'Gumand Sarcocolline Varnish. — Inks. — ^To render Wax 
Miscible with Water and Glycerine. — To Prevent Vibration 
of Canvas or Paper stretched for Crayons. — Instantaneous 
Sizing. — Mastic for Plastering Up. — Method of Rendering 
Paper Transparent. — Paper for Taking Tracings from Oil 
Paintings. — Commercial Guarantee 162 



SCIENCE OF PAINTING. 



CHAPTER I. 
THE PROCESS OF PAINTING AT DIFFERENT PERIODS, 

As soon as men collected together anywhere to live as 
a society, they had a religion and an art, whose first 
manifestation has always been painting. 

The primitive process employed was everywhere the 
same. It still exists in all its simplicity with some savage 
tribes who use it to paint their idols, their utensils, their 
firearms, and even the bodies of their warriors. This 
process, limited to the use of argillaceous earths, naturally 
coloured by the presence of metallic oxides, or to dyes 
obtained from the decoction and the sap of certain plants, 
consists in mixing earth with water to form a coloured 
paste, and then by means of a little stick, or merely with 
the finger, spreading it over the object to b^ decorated. 
This is a very simple method! 

And yet, although this first process is so very elementary, 
it cpntains the germ of all the others ; and we are about to 
see that the numerous colouring-matters placed to-day by 
nature and science at the disposal of painters are nearly 
all combinations of three elementary substances — clay, 
metallic salts, and vegetable dyes. 

v.p, I 



10 SCIENCE OF PAINTING. 

This was afterwards improved by mixing gum with these 
elementary colours, to obtain more substance and more 
brilliancy. 

The Egyptians have bequeathed to us on their mummies 
specimens of these first gum paintings, which they further 
covered sometimes by melted wax, and which, being thus 
preserved from contact with the air, have retained an extra- 
ordinary freshness. 

In the most ancient times the use of coloured clays, 
incorporated with lime and cement, was customary, and 
also the manufacture of terra cotta covered with vitrified 
substances. Such are the coarse enamels and cements of 
various colours, which, broken into little cubes and after- 
wards encrusted in fresh mortar with dther pieces of marble 
or stone, constitute the earliest specimens of mosaic work. 

In the heroic age of Greece, the painter introduced those 
same colouring matters, reduced to fine powder, into melted 
wax ; often he added resin to this, and spread those pastes 
softened by heat on the surfaces which he wished to deco- 
rate, by means of a bronze spatula slightly warmed. After- 
wards, with the other end of the spatula, which was pointed, 
he drew, on the yet soft surface of colour, the object which 
he wished to represent ; and after having broken off all that 
was outside the outlines he filled up the place left vacant 
with paste of another colour. 

In this manner were painted the prows of the ships which 
carried the Greek kings during the Trojan war.* 

In short, until then, the art of painting had much in 
common with that of sculpture, and only consisted of flat 
tints. Much later, with the use of the paint-brush, the first 
attempts at shading appeared. 

* This kind of painting has lately been resumed, and a picture painted 
by this process was on view at the last ^alon. 



PROCESS OF PAINTING AT DIFFERENT PERIODS. II 

The artists of those days could, by spreading ground 
colours mixed with water on fresh mortar made of sand and 
lime, produce graduated tints ; and the first pictures worthy 
of the name were painted after this invention of fresco- 
painting. They painted afterwards with resinous gums into 
which was introduced wax, rendered miscible with water 
by the help of lime. 

This process finished, the painting was moved backwards 
and forwards before a bronze chafing-dish, in the form of a 
grating filled with hot coals and called a cauterium, .The 
wax and the resin, melting under the influence of the heat, 
then formed, with the colours, a homogeneous whole whose 
durability was almost unlimited. 

Paintings done by this process have been seen in a 
perfect state of preservation nine centuries after they had 
been painted, although they were on outside walls exposed 
to all the injuries of the weather. 

In the same way the Greek sculptors coated over their 
marble statues, to preserve them and to give them a verdi- 
gris of which unmistakable traces are still found on some 
fragments. 

At last, when by distillation they were able- to extract 
essential oils from certain plants, painters made varnishes 
by dissolving resins in these essential oils, and one may say 
that then the painting of the ancients attained its apogee. 
In fact, a picture of this period painted on lava was ex- 
hibited at the Universal Exhibition of 1889 in the Industrial 
Court, and all who saw it were struck with its extraordinary 
state of preservation. 

These different processes of antiquity were continued 
almost until the Middle Ages, when the use of wax was 
almost entirely discontinued, being superseded by egg 
painting which rapidly became general. The miniatures 



12 SCIENCE OF PAINTING. 

on the parchment of missals, the panels of costly shrines, 
the pictures painted on three-folding panels which orna- 
mented the altars and the walls of churches, were mostly 
painted by this process which is very substantial, as it 
admits of the introduction of resins — the yolk of egg con- 
taining an oil capable of dissolving the resins. 

Oil painting began in the fifteenth century. We are not 
here going to enter into that great discussion, which is not 
yet finished, as to whether oil painting was really discovered 
by Van Eyck, but perhaps we may venture to say that its 
discovery was really caused by a mistake. 

In the first place, neither John Van Eyck nor his brother 
€ver acquainted anybody with their processes, and their 
secrets died with them ; and if report is to be credited, they 
were even so jealous that they stabbed one prying individual 
who ventured into their studio. 

In vain distinguished artists, attracted by the fame of the 
two brothers, came from Italy to Bruges : they could learn 
nothing, except that the belief spread that Van Eyck owed 
the exceeding brilliancy of his colours to the use of oil. 

Now, at that time the word oil was used indiscriminately 
for all the slimy liquids which could be extracted from 
plants without the use of heat, and some of which certainly 
are essential oils. People did not know that such could be 
obtained also from the hard yolk of egg, and that these 
essential oils form with resins thick varnishes which have 
all the greasiness of true oils, and give to colours a trans- 
parency and a richness surpassing that given by oil alone. 

What is certain is that, from the processes of Van Eyck, 
only one word transpired, and that was — oil ! We now 
know that this word could be used with a double meaning, 
but for the painters of that date it was otherwise : they 
hastened to grind their colours with any sort of oil in order 



PROCESS OF PAINTING AT DIFFERENT PERIODS. 1 3 

to imitate the great inventor, and yet they never succeeded 
in equalling the powerful colouring of his pictures. 

Now, among the adepts at this new style of painting there 
were some great masters who ought to have been able to 
make as good use of the method as Van Eyck himself: we 
may therefore permit ourselves to say that the process, such 
as it has been employed since his time, was perhaps not his, 
or that it has been badly understood, for if this great painter 
really did use the oils which are still used to-day, he never 
used them except when much imbued with resin on panels 
prepared with size and outlined in egg : so that the oil 
colours applied semi-liquid or in glaze only merely exist as 
pellicles in his pictures. 

Not being able to penetrate the mystery which envelops 
the invention of oil painting, and convinced that, if it was 
Van Eyck who discovered it, he did not practise it as it 
has been practised since his day, we shall content ourselves 
with sajdng that the use of oil painting spread rapidly after 
Van Eyck's death, which occurred in 1450, and that, with 
regard to results obtained, the Flemish and Dutch schools 
were those which most nearly approached the great painter 
of Bruges — which allows us to suppose that they also 
approached him most nearly in technical methods. 

The custom of painting on surfaces prepared with size and 
of adding resin to oil-colours was continued for more than a 
century afterwards in Flanders. Otto Venius, the master of 
Rubens, retained the method, and Rubens himself painted 
all his first pictures in the same manner. When, later on, 
he used thickenings, it was only in the light colours, and he 
never abandoned the use of coatings of size. 

After this incomparable master, ^the method fell into 
disuse. Resins were no longer employed, which necessi- 
tated increasing the proportion of oil ; canvas and panels 



14 SCIENCE OF PAINTING. 

were prepared with coatings of oil, and thick layers of oil 
colours were put over them. To this abuse of oil was 
added that of turpentine ; and the painting, gradually losing 
its transparency, took a dull and floury appearance, and this 
went on increasing until the end of the eighteenth century. 

At the beginning of the nineteenth century all these 
traditionary methods disappeared, neglected by those who 
ought to have taught them, forgotten by those who ought to 
have practised them, and at last entirely unknown to the new 
generation. 

This generation, that of 1830, hastening to reverse every- 
thing, yet understood that a method was necessary, and 
they created some new ones : they created many, even too 
many, for not one of them was good. Never was so much 
written about painting as at that time, and never was paint- 
ing so bad in point of substance ; each group, each artist 
even, had formulas which he kept secret. 

One of them, facetiously inclined, wrote on the little 
bottles which lay about in his paint-box, " Oil of Perlimpin- 
pin," " Balm of Apollo," " Aerial fluid," etc. What looks of 
envy the pupils in his studio cast on those treasures ! How 
much they would have liked to have used them ! And 
later on, when they saw how brown the pictures of this old 
magician had become, how they congratulated themselves 
that they had not been able to do so ! 

To-day, artists have no longer any of that paltry jealousy, 
and, disdaining even to occupy themselves with the material 
part of their art, they leave the care of preparing their 
canvas and their colours to grinders who come down in 
hordes from the mountains, — we shall not say what mount- 
ains, so as to wound no susceptibilities. 

Those clever but ignorant colour-dealers invent oils, 
pomades, siccatives, etc., and under pompous names they 



PROCESS OF PAINTING AT DIFFERENT PERIODS. 1 5 

manufacture disastrous mixtures of colour. They furnish 
everything : the box, the easel, the paint brushes, the subjects 
of the pictures, even their own advice and the favourable 
opinion of the critics. 

The modern artist, furnished with all this amateur stock 
of wares and having no need to think of his requirements 
is free to follow the dictates of his fancy. He paints 
casually, without thought of the morrow, being merely 
desirous to follow the fashion, for that is important ! There 
are exquisite tints which it is necessary to have : veined flesh, 
marble transparencies, dull softenings, dusky shading, etc. ; 
there is not enough of that variety, — there must be more, 
the journalists insist ! 

Warm colours ? enamel ? 

No more of that ! 

And then there are the treasures of the virtuoso, the all 
powerful touch lovingly exhibited ! 

As for the vagaries of the paint brush invented by Paul 
de Saint Victor, they are old. 

And yet the masterpieces of yesterday, scarcely in the 
museums, get dark, crack, and weep tears of bitumen ! In 
the monuments, the new frescoes get mouldy, peel pif, fall 
from their places ; and the contemporaries who have seen 
when they were new the works of Henry Regnault and of 
so many others are obliged to tell to the young people who 
are unwilling to believe them, that the colours in those 
works were extremely brilliant and fresh when new. 

It is only necessary to take a walk in the Louvre to see 
that the preservation of the picture is in direct ratio to its 
antiquity : that is to say that in the paintings of the fifteenth 
century, to go no farther back than that, the colouring 
remains more brilliant and the materials more substantial 
than in those of the sixteenth century, and that in approach- 



1 6 SCIENCE OF PAINTING. 

ing our own time the painting deteriorates more and more ; 
those paintings which are in the worst state of preservation 
are not many years old. 

Whose fault is this ? Alas ! it is that of artists themselves, 
for their indifference surpasses all bo.unds. 

But, are they seeking to excuse themselves ? " What are we 
to do to make our painting imperishable ? Nobody ever spoke 
to us of it. Our professors themselves knew nothing about 
it." That is partly true. Therefore do not let us recrimi- 
nate, and let us forgive those who have gone before ; but, 
so that those who come after us may be wiser, let us find 
again those lost traditions which we shall do our best to 
perfect with the help of the discoveries of modern science. 

With this object we shall study all the materials employed 
by our predecessors, beginning always at the times of 
greatest antiquity and coming up to our own days; thus 
learning,* by the use which the ancients have made of their 
methods and the results which have reached us, what ought 
to be retained and what ought to be abandoned. We shall 
thus be able, on a sure basis made by the experience of 
many centuries, finally tp establish the essentials of the 
material processes of painting, and, shedding abroad the 
light into the darkness of ignorance and empiricism, bring 
forth from it a new science. .\ . 



CHAPTER 11. 
LIGHT AND COLOURS. 

It is not enough to give to artists good material to ensure 
the durability of their works, if those materials are badly 
used ; and it is not possible to indicate in a general manner 
how they ought to be used, as each object painted requires 
a different style of execution. 

The painter should obtain from his colours, by the 
different manners in which he puts them on by means of 
oils and varnish, all the effects of transparency, of opacity, 
of brilliancy, of dulness, etc., which light is capable of pro- 
ducing. Each of these particular manners of using the same 
materials so as to give a durable result necessitates special 
precautions which we shall indicate ; but in order properly 
to understand how one can reproduce artificially all the 
phenomena of light and of colour which present themselves 
to our eyes, it is indispensable first to know how they are 
produced in nature. 

According to the most modern theory, the luminous 
bodies by themselves, the sun, the stars, the fiame§, are 
composed of molecules in a state of perpetual vibration. 
This vibratory movement, communicated to the surrounding 
molecules, produces circular waves which, rolling off into 
space, cause to us when reaching the retina the sensation 
of light, in the same way that the sonorous waves when 
reaching the tympanum cause to us the sensation of sound. 



1 8 SCIENCE OF PAINTING. 

Some of these luminous waves are absorbed by bodies 
which they encounter, and thereby undergo chemical 
changes ; others make their way through transparent media, 
such as air, water, glass : this is the phenomenon of trans- 
mission. If they meet opaque bodies which stop them, 
they rebound and are thrown back into space : this is the 
phenomenon of reflection. 

But, according to the density of the transparent mediums, 
and according to the matter, the form or the nature of the 
surface of the opaque bodies, they are transmitted or 
reflected in different conditions. 

In mediums of homogeneous transparency they are 
transmitted in a straight line, but the direction changes as 
soon as they pass into a medium of another density : for 
instance, a stick plunged into water appears to be broken, 
that is called refraction. When the waves are bent back by 
an opaque body to a polished surface, the reflection is direct 
or specular, as by a mirror, for instance. In this case, if the 
light strikes the object perpendicularly, it comes back upon 
itself; if it strikes obliquely, it is sent back in the same 
oblique manner from the opposite side to the one whence 
it comes. When the body has a rugged surface, the 
luminous waves are sent back in all directions : this is 
diffuse reflection. But a body may be more or less trans- 
parent or opaque in its entirety, or composed of some 
parts very transparent and others very opaque. It may 
have a surface more or less polished or rough, or it may be 
composed of some parts very polished and others very 
rough; so that, combinations of transparency, of opacity, 
and of rough and polished surfaces being unlimited, the 
phenomena of transmission and reflection of light are also 
unlimited. 

On those general laws are still to be grafted the effects 



LIGHT AND COLOURS. 1 9 

of concave or convex surfaces — the convergence or diver- 
gence of rays ; the effects of multiple refraction from surfaces 
cut in facets ; the theory of prisms, etc., which constitute 
the science of optics, upon which we cannot here enter, 
but which painters would do well to study. 

Now that we know how His Majesty the Sun gives us 
this beautiful ray, we should -also like to know of what it 
consists. 

Beautiful sunbeams for our information enter this dark 
room, go through this little hole, and afterwards cross the 
prism. There ! Now the beautiful ray is analysed, spread 
out on a screen. It is now a luminous band divided into 
seven distinct colours : red^ orange^ yellow^ green, blue, ultra- 
marine, violet'^ and the sharp and learned analyst, getting 
ready to dissect it, calls it at this point the Macabrean name 
oi solar spectrum. 

Under the scalpel of science this spectrum reveals 
strange secrets. It shows the process of spectral analysis, 
thanks to which we are able to learn something of the 
chemical composition, not only of the stars in our planetary 
system, whose light comes to us in a few minutes notwith- 
standing the millions of leagues which separate them from 
us ; not only of the most distant stars, whose light takes 
years to reach us, but even of the nebulae, which, yet 
farther off, are lost in the infinitudes of space, where all 
thought or calculation would mean madness, were it not 
that there is found — God ! 

By the help of various prisms and decomposed rays, the 
analyst in his dark room places in juxtaposition and in 
superposition colours which are very interesting, but which 
it will be more profitable for us to consider later. 

He establishes the fact that the coloured rays cannot be 
decomposed, that their refrangibility increases when they are 



20 SCIENCE OF PAINTING. 

taken from left to right, and that they have each different 
undulations of length, which go on diminishing from red, 
where they are 620 millionths of a millimetre, to violet, 
where they are only 423 millionths of a millimetre.* On 
account of this the number of their vibrations per second 
increases from violet, which has 752. trillions of vibrations, 
to red, which has no more than 514 trillions. Finally, the 
analyst, reuniting the seven coloured elements of the poor 
sunbeam by means of two prisms placed opposite to each 
other, is thus, able to reconstitute the white light. 

Beautiful sunbeam-! you have taught us our lesson : you 
are now free. 

If the beautiful sunbeam could speak, it might tell us 
that, since the beginning of the world, the secret of the 
decomposition of light has been under every eye ; that sun- 
rise and sunset, the rainbow, the iridescent fringe of the 
glaciers, the thousand fires of the diamond, might have taught 
us ; and that there was no need to drag a poor sunbeam 
into a dark room in order to teach us. Whilst hearing this, 
man, so proud of his learning, might well feel ashamed of 
the time it had taken him to learn. 

Before studying colours, we are confronted with one 
primary question. 

Why is a body red or yellow or blue, etc. ? 

We do not know. But if we. do not know the cause, at 
least we may learn the effect of this phenomenon. 

All bodies do not act alike under the action of the light 
which they receive. They have the mysterious property of 
absorbing either the whole or part of that light, or some- 
times after having decomposed the light they only absorb 
certain coloured rays of it. Some bodies have only the 
faculty of absorbing, others have only that of decomposing. 

* A millimetre is *ooi of a metre. 



LIGHT AND COLOURS. 21 

Others, again, reunite in different proportions the faculties 
of absorbing and of decomposing, and those are the 
differences which determine the colour peculiar to each of 
them ; for the colour of a body is the sensation which is 
produced on the retina by the portions of light which it has 
not absorbed, and which it sends back. 

AH absorbed light produces darkness. A body which 
would absorb all the light which it receives would be quite 
dark ; it would be impossible to distinguish either light or 
shade. A body which would absorb nothing from the light 
which it receives would be just as vivid as that light ; but 
these two extremes, altogether unmodified, are not met with 
in nature. 

A body which absorbs part of the light and sends back 
the rest is grey. The whitest objects, therefore, are only 
very light grey, and the blackest very dark grey. However, 
the light which a grey body sends back is the same as 
that which is sent back by a white body : the difference is 
merely in quantity. Why do those two lights of the same 
quality give different sensations ? It is because, the light 
being shed equally over all bodies, our eye, in comparing the 
luminous intensity of several objects lighted by the same 
light, can perfectly distinguish the quantity which each of 
them absorbs, and our eye supplies the missing quantity 
with an equal amount of black. Consequently, if a body 
only sends back the half of the light which it has received, 
our eye has the sensation of a grey composed of half black 
and half white. 

All decomposed light produces the seven coloured rays 
of the spectrum. The bodies which, after having effected 
this decomposition, absorb one or more of these rays and 
send back the others are of the colour of the ray which they 
send back, if they send back only one, or of the colour 



22 SCIENCE OF PAINTING. 

composed by the mixture of the rays which they send back, 
if they send back more than one. 

Example: — A body which absorbs six rays and sends 
back only the red is red, and so forth. 

If a body, having absorbed a part of the light which it 
has received, instead of sending back the rest decomposes 
it, the colour of the coloured ray, or of the mixture of 
coloured rays which it will send back will be more or less 
darkened, according to whether it shall have absorbed much 
or little of the light. 

Example: — ^A body which absorbs the half of the light 
received, decomposing the remainder and only sending back 
the red ray, gives the impression of half-black and a seventh 
of half-red, Le.^ a dark red. 

If, on the contrary, a body sends back a part of the 
light received, and decomposes the rest, the colour of the 
coloured ray or of the mixture of coloured rays which it will 
send back will be of a colour more or less light, according 
to the quantity of light sent back. 

Example : — A body which sends back the half of the 
light received, decomposing the remainder, and sending 
back only the red ray, gives the impression of half-white 
and a seventh of half-red, i.e. pink. 

It is, then, in fact, the mixtures of colours between them- 
selves, and the large or small quantity of light or darkness 
which is added to them, that gives the millions of shades 
discernible in nature and which in painting is called 
colouring. 

But in the mixtures of colours much difference exists 
between mixing coloured rays and mixing coloured matter. 
Two rays of the same light passing one through a pane of 
blue glass, the other through a pane of yellow glass, give, 
at the place where they meet, a white light If, on Ithe 



LIGHT AND COLOURS. 2$ 

contrary, the two glasses are placed one over the other, the 
light transmitted will be green; and if, reducing the two 
pieces of glass to powder, the powders are mixed, th^ light 
reflected will still be green. 

In order to explain the reasons of this phenomenon and 
of many others, it would be necessary to enter into a number 
of scientific causes sufficient to drive an artist mad. Besides, 
as we never do have at our disposal on our palette the rays 
of the spectrum, and consequently cannot utilise them, any 
more than we can the effects of polarisation^ of phosphor- 
escencCy of efflorescence^ etc., we shall leave all that for the 
consideration of those material colours which are all that 
remain to us when we pass from the study of physics to 
that of painting. 

Those colours which consist of matter ground with 
different substances may be had in conditions more or less 
transparent or opaque. They act on the eye by transmission 
and reflection^ and consequently give different results 
according to the conditions in which they are used. 

In fact, if you add a colour to opaque white, you will not 
obtain the same shade as if you were to rub a thin coating 
of that colour on the white. In the same way a colour 
added to opaque black does not give the same result as if 
it were transparently put on that black. 

By this rule, two or more colours have different effects 
according to whether.they are mixed in an opaque condition 
or laid one over the other in clear coatings. 

The use of colours of different degrees of opacity consti- 
tutes what is called, in studio terms, solid zxA semi-liquid \ 
and the use of different degrees of transparency, scumbling 
and glazing. 

The appearance of a colour changes also according to 
the nature of its surface and the manner in which it is 



\ 



24 SCIENCE OF PAINTING. 

painted : the surface can be rendered dull by flaking^ 
smooth by using the badger brush, pr rough by dabbing i 
effects of vibration are to be obtained by strokes called 
hatches. 

In fact, a painter who knows his trade finds means of 
making his colours take all the different aspects which they 
present in nature; thus bringing into action unawares, as 
M. Jourdain made prose, all the phenomena of refraction, 
of specular reflection, and of diffuse reflection^ by means of 
which the coloured rays manifest themselves to our organs 
of sight. 

The artist obeys, therefore, immutable laws which he 
does not know. How can he do it ? The reason is that 
the laws of colour, like those of perspective, painters had 
felt before science had discovered them, and that artists 
have them all, more or less, by instinct. 

How much quicker, however, they would arrive at this 
facility by knowing, from the outset of their career, those 
laws which are unchangeable and which they only arrive at, 
using unconsciously later, after many attempts and jumbling 
efforts ! 

Yes ; but where are they to be learned ? 

Not in treatises on physics, where they are mixed up 
with all the questions of optics atid of chemidal and caloric 
luminous rays. Neither is it in works specially written for 
artists by professors, grave but inexperienced, who have no 
proper knowledge of what painting really is. 

Oh, no ! Without having seen them, one would not 
dare to believe it possible to write the contents of some of 
those volumes. 

In one which has very recently appeared, the author tells 
us : "In order to paint the head of a young man of white 
race, twenty-one years of age " (not twenty-two or twenty- 



LIGHT AND COLOURS. 2$ 

three — exactly twenty-one), " mix such and such colours for 
the brow, for the eyes, the lips, the cheeks," etc., and the 
author draws out a plan of cipher for his directions. It is 
true that this laughable author informs us that he did not 
invent the notation (which is to be regretted !). 

The predecessor had expressed the cheeks of the young 
man by this formula : — 

4 red 3^, 4 — 5 shade ; 

but the new writer changes the formula and thus simplifies 
it ! The young man's cheeks are written : — 

R I a Oi No 

R I i Oa Nu 

Ah ! what genius ! 

It is works of this kind that give the proportions of colour 
to be mixed in order to make the shades of the leaves of 
all the trees, the lakes and the rivers of Europe, the mount- 
ains of Switzerland, etc. ; to imitate the brightness of the 
rose, the velvet of the peach, or the flames of a fire ; to 
reproduce the tints of the human skin in all races of the 
universe, from the ebony skin of an African negro to the 
pearly colour of a patrician ; and one limits precisely all 
the shades according to whether one is painting an infant, a 
child, a young girl, or a grandmother : they do not give us 
the recipe for painting a woman who conceals her age ; 
perhaps all the colours should be mixed up together. 
Finally, they even furnish us with the colour of the passions 
— deadly paleness, the blue of anger, the red of shame, and 
the carnation of bashfulness ! All that is a good deal. Too 
much to be discovered by a single artist ! 

Let us suppose now that a pupil of this professor paints 
a picture, following out from point to point his programme : 

v.p. 2 



26 SCIENCE OF PAINTING. 

it is soon done. It is of a noble simplicity, a triumph of 
local colouring, a masterpiece of to-morrow : it is sold, or 
offered to the Louvre, and here we leave it. 

But if a thoughtful pupil were tempted to try in his turn, 
he would first think in this manner : We take a ball and we 
smear it all over with any colour, say vermilion. We shall 
next make a copy of this ball in painting. Do you think 
that for this purpose we can use the same vermilion ? Yes, 
but only for one stroke of the brush — that which corresponds 
to the exact middle of the ball ; for, at all the other points, 
the colour is modified by the bordering of light, the reflec- 
tions of neighbouring objects, the shadow and the half-tints 
which constitute the shading, and we should require almost 
all the colours of the palette in order to reproduce these 
modifications. 

Now, here is a picture representing an orange tree laden 
with oranges : we shall leave the fruit and proceed to darken 
the foliage, and also the sky and the earth. In fact, we now 
produce the effect of night, and the oranges, which have 
not changed their colour, are become luminous balls like 
those which adorn the trees on f§te nights. 

Now, let us take a white canvas on which we paint one 
touch of a brilliant green. Well ! according to what we 
paint round it, you may make of that touch whatever you 
like : an omnibus lantern, with a background of Boulevard 
at nightfall ; a leaf illumined by the sun, in a green bower ; 
the sacred emerald which shines on the brow of the god 
Buddha in a Hindoo temple. Without changing anything, 
this touch may lose its brilliancy and play the role of a 
lizard in half-tints amidst the effulgent odalisks of Diaz, 
or it may be lost in the shadow of a stake outlined on the 
Grand Canal at Venice, touched by the light of an Italian 
sunset. 



LIGHT AND COLOURS. 27 

Thus, a material colour, placed in a picture which remains 
lighted by the same light, changes its tone according to its 
surroundings. 

Delacroix said : " Give me some mud, I will make of it 
the skin of Venus, if you leave to me the choice of the 
surroundings." 

It is the same thing in nature, where the colour of a 
body can be modified to any extent by the degree and the 
colouring of the light which it receives from the reflection 
or the mere contrast of the colours near it, etc. 

Let us follow a cardinal, dressed in red, whilst he walks 
in his gardens. At every instant the colour seems different, 
according to whether he receives the blinding rays of the 
sun, or the white reflection from a cloud, or shelters under 
the verdant shade of a leafy grove. Whether we see him 
on the intense green of the sunny lawns, under the dark 
green of the cypress, on the silvery surface of a lake, or 
under the azure of the sky, he still changes. He changes 
always, becoming pale before a bank of geraniums, and red 
before the marble of the statues ; he gets dark in proportion 
as the daylight fades, until he becomes of a dark purple, 
and is dressed in black, like a simple priest, as he returns 
to his palace by the dusky shades of twilight. 

There is still another reason why the colour of a body 
cannot be defined by a formula : it is that the colour does 
not appear alike to every one. Although it is said that 
" Tastes and colours should not be discussed,'' and although 
popular sayings have always a foundation of truth, that 
would not be a sufficient proof; we require better arguments. 

We said that light had other properties besides that of 
enabling us to see. It develops heat, and it acts as a 
chemical agent. If we move a thermometer under the 
different coloured rays of the spectrum, we shall see that 



28 SCIENCE OF PAINTING. 

heat increases from violet to red, and passing red it con- 
tinues to increase, although in the shade, to a culminating 
point which is to be found left of red, at a distance equal to 
that existing between red and yellow. Starting from this 
point heat diminishes, but it is still appreciable at a distance 
from red equal to the extent of the entire spectrum. 

As for the chemical effects of light, it is impossible to 
name them all. Let us merely think of those forming the 
basis of all photographic processes. These may be of 
great violence, since chlorine and hydrogen, which are 
without effect upon each other whilst in darkness, combine 
explosively when they are exposed to the sun. 

The chemical power of the coloured rays of the spectrum, 
contrary to those of heat, increases when going from red to 
violet. Farther than the last violet rays, we finish by per- 
ceiving another shade, to which the name of lavender grey 
has been given ; in the same way that beyond the red is 
now distinguished a beginning of a darker shade named 
crimson. The truth therefore is that the solar spectrum 
stretches from the extreme point, where heat begins to be 
felt, to the other extreme point, where all chemical action 
ceases ; but to us it is only visible in its central part. We 
say now visible, because our organs of sight becoming un- 
ceasingly, not stronger, but more delicate, we already see 
better than formerly ; and perhaps a day may come when 
we shall be able to distinguish yet more than we Aow can. 

With this reasoning we must admit that the ancients had 
not the power of seeing all the colours which we see. 

Well ! but why not ? 

Certain scholars have already tried to prove that the 
ancient painters did not use either blue or violet, and that 
the language of Homer has no words expressive of those 
colours. Are we to infer from this that there was once an 



LIGHT AND COLOURS. 29 

epoch when these extreme shades of the spectrum were not 
yet seen ? 

At all events, amongst organised beings there exist some 
who, gifted with an organ of vision enabling them to 
perceive light, nevertheless do not see colours, or only see 
certain colours. Little crustaceae of a particular kind, in a 
globe full of water, frisk about, and hasten towards a jet of 
light, if that light is presented to them of a certain colour, 
and do not move if the light is not of that particular colour. 

The human race presents similar anomalies. Certain 
people, affected with an eye malady called Daltonism, are 
unable to distinguish all colours. It has been remarked, 
since examination has been compulsory to the employes of 
the railway companies, how great is the number of Dal- 
tonians amongst those men who present themselves for 
examination. The proportion is quite as great amongst 
those who do not present themselves; only these latter 
generally have no suspicion of their infirmity. Many are 
artists, and some are even very talented. 

One of them, whom we knew as a student, could not 
distinguish red from green. To him, vermilion and Verona 
green were identical. He was guided by the labels on 
his tubes, and, knowing by hearsay the use of these two 
colours, he painted moderately well. There certainly were, 
here and there, some wandering touches which " howled " 
SL little, in studio phrase ; that passed for originality. But 
having one day, by inadvertence, taken the palette of a 
neighbour who did not arrange his colours in the same 
order as himself, the secret was discovered. All those who 
have seen it must still be able to remember the academical 
figure of the ancient wrestler, conscientiously painted in all 
the greenest tints of spinach and leeks. One can imagine 
the burst of laughter which this caused amongst his^com- 



30 SCIENCE OF PAINTING. 

rades ; it was spoken of for a long time. The poor boy, 
in desperation, dating from that memorable day, cleared 
from his palette all reds and brilliant greens, and contented 
himself with painting subjects not requiring much eflfect 
from colours. As he drew very well, had the idea of 
relative values well developed, and keenly felt the poetry 
of nature, he became, in spite of all, a great artist ; only 
no picture ever left his studio without a friend sincere (but 
indiscreet as you may see) coming to make sure that no 
mistake had slipped in, and that the few indispensable reds 
were well in their places. 

We may therefore conclude from the preceding examples 
that the colour of a body is perpetually modified by all sorts 
of causes, and that it is not the same to every eye. 

If, therefore, professors, imposing but ignorant, having no 
knowledge of painting (we must repeat it), dare any longer 
to wish to formulate the precise colours of objects, may they 
be the laughing-stock of the lowest of the colour-grinders I 



CHAPTER III. 

THE LAWS OF COLOURING, 

The seven colours given by the decomposition of light 
seem to melt insensibly into each other ; but a practised eye 
distinguishes almost a thousand shades in the extent of the 
solar spectrum. 

The presence has also been ascertained of about two 
thousand dark rays, which separate those shades into 
unequal parts. 

All scientists, however, are not agreed about choosing 
exactly amongst those shades the seven normal colours. 

One considers red as being a little nearer to orange, for 
instance, and the other considers it to be a little farther 
off, etc. 

That alone would render impossible the establishment 
of a normal universal spectrum. It has been proposed to 
decide with common consent, that the true red, the true 
yellow, etc., should be between such and such rays, these 
latter remaining always in the same place. Unfortunately, 
if the rays are immovable the shades are not ; they change 
according to the intensity of the light which produces them : 
when the light increases, all the colours of the spectrum go 
nearer to the centre, which is greenish-yellow : then the 
yeUow becomes a greener yellow, the orange yellower, the red 
more orange, the crimson redder ; and on the other side of 
the centre the green becomes a yellower green, the blue 



32 SCIENCE OF PAINTING. 

greener, the ultramarine bluer, the violet more ultramarine. 
On the contrary, in proportion as the light diminishes, the 
colours get farther from the centre : the yellow becomes 
more orange, the orange redder, the red more crimson, and 
this last, going on towards darkness, becomes darker. On 
the other side of the centre, the green becomes bluer, the 
blue more ultramarine, the ultramarine more violet, and this 
last like crimson, going on towards darkness, gets darker. 

So that, if you decree, for example, that the true red is 
between such and such rays, as the red moves to the left 
or to the right according to the intensity of the light, the 
red will not always remain between those rays, for the rays 
do not change place. 

It would therefore be necessary to establish some practi- 
cal means of measuring this intensity of light, so that we 
might say : it is at such a degree of luminosity that the 
spectrum should be consulted. 

Whilst admitting that that might be possible, there still 
remains one objection : it is that light is differently coloured 
according to the season, the climate or the hour of the day. 

After these explanations it is easy to understand why 
those who have tried to fix a universal standard have all 
failed. 

But even if we could overcome the difficulties which 
oppose the realisation of this standard, what practical results 
should we obtain from it ? 

You ask a manufacturer for a stuff of a certain shade by 
this standard ; but according to the material which will be 
dyed to prepare the stuff ordered so will the shade differ. 
Yarns of silk, wool or cotton, having surfaces more or less 
shiny, will reflect back the white light in a small or great 
degree, and, being twisted or woven in different ways, there 
will be effects of multiple reflection, which lighten or darken 



THE LAWS OF COLOURING. 33 

the colour. And if an artist wishes to make use of this 
standard, if he put colour of the normal tone on his palette, 
what will be the use of it to him ? As we have seen, the 
material colours which he uses change their tone according 
to the manner in which they are used, and according to 
their surroundings ; without counting the chemical reasons 
which cause them to vary still more. 

If we are stopping in order to protest against this non- 
existent colour standard, it is because it is being constantly 
proposed in special works all very unpractical, as, for ex- 
ample, in a recent chromatic summary, where the author 
gives chromo-typography tables in which all the shades 
correspond to written formulae. Only, he artlessly tells us 
that his shades have not come out very well, and, further, he 
begs us to keep the book shut as much as possible, to prevent 
his plates fading from exposure to the light. And in this 
manner he professes definitely to settle colours. 

Thatjwould be very amusing were it not that such volumes 
written for artists do great harm to those who read them. 
In fact, their perusal is time wasted, and by always reading 
without understanding one loses all desire for learning. 

The solar spectrum, as we have just seen, has only one 
fixed point. It is a yellow-green. From it we can go to 
violet, which is the last perceptible colour on the right, the 
left extreme being a deep crimson. 

As soon as the human mind seeks to penetrate the secrets 
of nature, it finds always infinitude — that great hope ! 

Infinitude is represented by the figure of a serpent biting 
his own tail : this is a bad illustration, for the idea of 
a circle, a closed and imperfectible figure, more properly 
represents a proud despair. This idea fits in with those 
which declare that when human sensation stops all is 
finished ; and, as regards our present subject, somebody 



34 SCIENCE OF PAINTING. 

should think of considering the solar spectrum as a definite 
whole and uniting the two extremities. This suggestion 
has not been lacking. It is fortunate that to prove the 
folly of this conception we have other arguments than 
philosophical fancies. 

In the first place, the theory of luminous waves does 
not allow us to suppose that the shortest waves can be 
immediately joined to the longest ; further, the laws which 
regulate the mixtures of the colours of the spectrum would 
not apply at all if it were desired to mix the extremities- 
Thus violet, returning to the side of red and mixed with it, 
does not give the hue in which crimson takes its origin. 

It is a very convenient theory that colours are arranged 
in a circle, but as it is not true it must be renounced. It is 
like the three primary colours which founded all the others. 
But that is another mistake. It is true that green can be 
made with yellow and blue, orange with yellow and red, 
and violet with red and blue \ but this green, this orange 
and this violet are darkened, by a phenomenon of interference 
which it would take too long to explain here. The primary 
colours would have to be soiled to make them harmonise 
with the compound colours, and we should have to be 
satisfied with a circumscribed palette which could have 
no crimson. Yet crimson exists in nature, and painters 
cannot dispense with it if they wish to reproduce all they 
see. 

Haying explained why we must renounce, with reference 
to painting, the study of the mixtures of the coloured rays 
themselves, we shall therefore begin by treating them as 
palpable substances, and copy the solar spectrum with the 
material colours which are at our disposal. Leaving all 
scientific experiments, we shall collect the phenomena 
which produce the mixtures of these colours, their super- 



THE LAWS OF COLOURING. 35 

positions and their contrasts, under the general name of 
laws 0/ colouring. 



Mixtures of Opaque Colours. 

Colours prepared to an equal degree of opacity and of 
luminous intensity will be arranged on a black palette in the 
order of the spectrum. Certain mathematical coincidences 
which we find in the mixtures of colours being of use to 
us, they are numbered so as to distinguish, immediately, the 
odd numbers from the even, and the fixed point at yellow- 
green is marked by a cross ; moreover, each space between 
two colours representing the intermediate shades, is 
separated into five equal intervals, which divide the spec- 
trum into thirty-seven degrees. The shades are further 
subdivisible, as the eye can perceive a thousand of them ; 
but that would be useless for our demonstration. On left 
and right, crimson and violet occupy the degree No. 3 of 
the intermediate shades between the two extreme colours 
and those unknown. 

Mixtures of Two Colours, 

1. When two colours come together, their mixtures, in 
all proportions, produce the intermediate shades with all 
their luminous and colouring intensity. 

Example: — Red and orange produce all the shades of 
red-orange and of orange-red; blue and green, all the 
shades of green-blue and of blue-green, etc. 

2. The mixture in equal parts of two odd colours separated 
by a single other, produces the colour which separates them, 
but with less colouring intensity. 

Example: — Red and yellow produce an orange greyer 



36 SCIENCE OF PAINTING. 

Crimson ^^^.^.—^^^w^— m^— ^^^ 



Red . • . . 



Red-orange 



Orange . . 



Yellow-orange . 



Yellow . . « 



Yellow-green . 



Green . . .  



Blue-green . . 



Blue . . . .  



Blue-ultramarine 



Ultramarine . 



Violet 



• • • 



+ 



I odd. 



2 even. 



3 odd. 



fixed point. 



4 even. 



5 odd. 



6 even. 



Whilst reading what refers to it, you would do well to have a copy of 
this list. 



THE LAWS OF COLOURING. 37 

than the normal orange ; yellow and blue a green greyer 
than the normal green. 

3. The mixture, in equal parts, of two even colours 
separated by a single other, produces a grey somewhat 
approaching the colour which separates them. 

Example : — Orange and green produce a yellowish grey, 
green and ultramarine a bluish grey, etc. 

4. The mixture in equal parts of two colours separated 
by two others, which consequently is always the mixture of 
an odd and an even colour, produces a grey approaching 
the odd colour. 

Example : — Red and green produce a reddish grey ; 
orange and blue a bluish grey; yellow and ultramarine a 
yellowish grey, etc. 

But if one doubles the quantity of the even colour, ;>., 
in the proportion of one-third odd and two-thirds even 
colour, the perfect grey, corresponding to the mixture of 
white and black, is obtained. 

Example : — 



The complement 


of red . . 


No. 


I is I -h 3 = 4» green. 


»» >» 


orange . 


» 


2 „ 2 + 3 = 5, blue. 


»» >» 


yeUow . 


M 


3 »> 3 + 3 = 6, ultramarine. 


») }) 


green . 


>» 


4 „ 4 - 3 = I, red. 


)> f> 


blue . . 


>» 


5 » 5 - 3 - 2, orange. 


}» >> 


ultramarine „ 


6„ 6 - 3 = 3, yellow. 



To find the complement of an intermediate, we calculate 
in the same way as for the colours nearest to it, deducting 
from the found complement the same number of degrees. 

Example: — ^To find the complement of crimson, we 
shall seek that of the nearest colour : this is red, of which 
the complement is green. As crimson is three degrees left 
of red, its complement will be three degrees left of green, 
i.^., yellow-green; violet being three degrees right of 



38 SCIENCE OF PAINTING. 

ultramarine, its complement will be three degrees right of 
the complement of ultramarine, which is yellow: it will 
therefore be yellow-green. The two extremes have thus 
for complement the fixed point — which is the centre. If 
we seek the complement of the red-orange shade placed 
at the first degree after red, we find it at the first degree 
after green, etc. 

The Mixtures of Three Colours, 

1. The mixture in equal parts of the consecutive colours, 
two odd and one even, produces the even one with less 
intensity of colour. 

Example: — Red, orange, and yellow, produce a greyer 
orange than the normal orange, but also less grey than that 
produced by the mixture of red and yellow \ yellow, green, 
and blue, produce a green greyer than normal green, but 
less so than that produced by the mixture of yellow and 
blue, etc. 

2. The mixture, in equal parts, of three consecutive 
colours, two even and one odd, produces a grey approaching 
the odd colour. 

Example : — Orange, yellow and green, produce a yellowish 
grey ; green, blue and ultramarine, a bluish grey, etc. 

3. The mixture, in equal parts, of three odd colours, 
produces perfect grey. 

4. The mixture of three even colours produces also 
perfect grey. 

As a matter of course, results obtained by mixtures of 
equal portions would be influenced by any colour the pro- 
portion of which was increased : thus, red and yellow, which 
in equal proportions produce orange, would produce a red- 
orange if the proportion of red were increased, and an 
orange-yellow if the proportion of yellow were increased. 



THE LAWS OF COLOURING. 39 

As for all other combinations beyond those above specified, 
they give greys more or less coloured. 

The Superposition of Colours. 

If we paint a transparent colour over so thin a white that 
this foundation white has influence, it is as if we were to put 
light behind that colour, which is then transmitted to us by 
transparency instead of by diffuse reflection^ as when it is 
opaque. The effects obtained by the laying on of colours 
are more perfect in proportion as the colours used are more 
transparent. Leaving those which we have just used, as 
well as the black palette, we shall again copy the spectrum ; 
but, this time, on a white palette and with colours which 
we shall render all equally transparent with more or less 
varnish, and leaving to them equally their colouring 
intensity. As for the luminous intensity — the light coming 
from below, produced by the white of the palette — it is 
perfectly regular for layers of similar thickness. 

The first observation which strikes us is that by this new 
means we obtain a much greater colouring intensity for the 
same luminous intensity : /.^., when, with opaque colours, 
we wish to have, for instance, a very light red, we must add 
to, it so much white that we arrive at a pale pink where the 
sensation of red is almost lost, whilst, by transparency, we 
obtain at the same degree of light a pink much more vivid, 
in which the sensation of red is still palpable. 

Another example still will help to show this difference. 

Being given red the most intense possible to make with 
opaque colour, it would be useless to put more on the top, 
— it would not render it more intense ; but if you painted it 
over with transparent red in glazing, you would increase 
considerably the colouring intensity without diminishing its 
luminous intensity. 



40 SCIENCE OF PAINTING. 

Superposition of Transparent Colours on White and on 

Black. 

A colour painted over white increases in luminous in- 
tensity in proportion to its being in coatings more or less 
thin ; but it gets near to the fixed point of the spectrum (/>. 
the yellow-green), according to the law that we have already 
mentioned. 

Example : — In coatings thinner and thinner : 

Left of f y^^^°^ becomes more and more yellow-green, 
the fixed J °'!°8« " " •' y'""" 



*e fi-ed \ SSLarine" 



pomt. 



violet 



>» 






orange, 
red. 

yellow-green, 
green, 
blue, 
ultramarine. 



On the contrary, if you increase the thickness of the 
coatings, starting from the point where the colours are at their 
greatest degree of colouring intensity, they go farther away 
from the fixed point (/.^. of yellow-green), the luminous 
intensity diminishing. 

Example : — In thicker and thicker coatings : 

Left of { yellow becomes more and more orange, 
the fixed -[ orange „ „ „ red. 

point. \ red „ ,, ,, crimson. 

And as after crimson is darkness it gets darker : 

Right of r green becomes more and more blue, 
the fixed -j blue ,, ,, „ ultramarine, 

point. [ ultramarine ,, „ violet. 

And violet, going also towards darkness, like crimson 
becomes darker. On black, if it were absolute, a trans- 
parent colour would not go. On account of its being 
transparent, it does not send back the light which strikes it ; 



% 



THE LAWS OF COLOURING. 4 1 

it can only transmit what comes behind it : so, if there be 
only darkness it can transmit nothing. But, as we mentioned 
before, there is in nature no body of an absolute black. 

If we divide into a hundred parts the quantity of light which 
strikes a black screen, the screen reflects about five parts ; 
yet this small quantity is sufficient to render perceptible the 
transparent colour painted on the screen : the effects there- 
fore will be the same as upon white, but considerably 
darkened. In painting transparent colours upon lighter and 
lighter greys, you may see the results of this law accentu- 
ated in proportion as the gradations get lighter. 

Superposition of Transparent Colours upon each other. 

If you paint one transparent colour over another, there 
are mixtures by transparency and those mixtures follow the 
same laws as do the opaque colours. If the bottom colours 
contain white or black, you add to them the results which 
are given by the superpositions on white and black that we 
have just been studying. 

Superposition of Translucent Colours. 

Bodies composed of very small minute particles exist in 
suspension in a transparent gaseous medium either liquid 
or solid, such as clouds of dust and smoke, the gummy 
liquid of paste, mother-of-pearl, opals, tortoiseshell, etc. ; or 
composed of little imperceptible drops of liquid in suspen- 
sion in a medium, also transparent liquid but of different 
density, such as all emulsions ; or in a gaseous medium, like 
all the vapours in the air — mist, dew, fog, etc. 

These bodies, which are called translucid, uniting the 
properties of transparency and opacity, transmit a part of 
the light which they receive and reflect a part ; but the part 
which they receive takes a more orange tint, and the part 

KP. 3 



42 SCIENCE OF PAINTING. 

which they reflect a bluer tint. Those two colours, orange 
and blue, of which tints the light, transmitted and reflected by 
the translucent bodies, is, are placed in the spectrum, just at 
the centre of each of the halves separated on the fixed point. 

Example : — Smoke when escaping from the chimney of a 
hut appears bluish on the dark green of the trees, because, 
having no light behind to transmit, we only see the reflected 
light ; but the same smoke appears reddish when it is on 
the luminous sky. We see it then by transparency. 

A glass of milk seen in transparency is orange ; but if 
you spill some of it on a dark table, it becomes bluish, 
because then we only see it by reflection. 

The air itself, holding in suspension solid corpuscles, 
obeys this law of translucent bodies. The sky is blue, 
because, the terrestrial atmosphere, being unable to transmit 
the infinite darkness stretching beyond it, reflects the light 
of the sun. But turning aside, the atmosphere, transmitting 
to us its light by transparency, is no longer blue, and in 
proportion as the radiant orb descends towards the horizon 
its rays, coming through the translucent coatings of the 
mists which rise from the earth, are transmitted to us more 
and more orange as the mists are thicker and thicker; 
and quite at the approach of night, when the luminous 
intensity diminishes, orange, following the laws which we 
have explained, proceeds towards crimson, which is the last 
tint of the setting sun before darkness. 

These are also the causes which make the sun appear like 
an enormous incandescent ball on foggy days. 

In the same way can be explained the blue colour which 
the skin takes where the veins pass, the bluish tint of the 
white of the eye, etc. 

Artists who, often without knowing the causes of Nature's 
phenomena, have yet observed them all, have for a long 



THE LAWS OF COLOURING. 43 

time expressed instinctively this law of translucent bodies 
by separating their, colours into two classes, warm tones and 
cold tones. Warm tones correspond to all that part of the 
spectrum left of the fixed point, whose centre is orange. 
Cold tones correspond to all the part right of the fixed point, 
whose centre is blue. 

Painters speak the truth when they speak of the green 
leaves of plants lighted by transparency as of a warm green, 
and of those lighted from above as cold green. 

Poets are not equally correct. Their famous phrases 
should be suppressed which speak of the golden sun of the 
South, the empurpled skies of the East, etc. On the contrary, 
the nearer the sun is to zenith the whiter its light is, and 
the farther you go to the regions of the South, the atmosphere 
there being less charged with vapours, the bluer is the sky 
and the paler and more intense the light. We must go to 
the North, to the countries of fogs, to find the warm colouring, 
the golden reflections and the purple rays. 

Besides, it is in those northern places — in Holland, in 
Flanders, in England, at Paris — that the greatest colourists 
have lived. In Italy they are much fewer, except at Venice, 
which is a misty place. If we go thence south-eastward 
we do not even find great artists. 

If you add to the material opaque colours a transparent 
liquid, such as varnish, or if you use them in thin coatings, 
you render them translucid and they produce the results we 
have just been describing. Rubbed on dark tones, they 
approach blue and become colder ; rubbed on light tones, 
they approach orange and become warmer. 

A colour altogether opaque should have no transparency, 
even in the thinnest coatings ; and a transparent colour 
should always remain so, even in a very thick coating. 
Now, as neither absolute transparency nor absolute opacity 



44 SCIENCE OF PAINTING. 

exist in nature, and as oil and similar necessary mediums 
render paints more or less translucid, the opacity which we 
obtain from them is only relative, and it is by the degree 
of thickness of the coating that we render this quality 
perceptible. As for transparency, we can, by the help of 
varnish, arrive more completely at it; but to light our 
opaque colours in front and our transparent colours behind, 
we have not the command of light at the greatest degree of 
intensity which it displays in nature. 

To light a white canvas by the sun we must content our- 
selves with the diffuse light of a studio or museum reflected 
by our oil-white, or our paper if it be water-colours that we 
are using ; and this white absorbs already much light, for it 
only reflects 40 per cent, of what it receives. 

To represent a pane of stained glass transparently lighted 
by the sun, as our back-light we are obliged always to use 
those same feeble whites. In the matter of darkness we 
are also limited, having only black, which reflects 5 per 
cent, of the light which it receives, and which consequently 
is already grey in comparison to an absolutely dark hole. 
Yet if painters of talent arrive at giving us truthful repre- 
sentations with those limited means, it is only by using 
subterfuges — by exaggerating opposites, by sacrificing certain 
parts and making much of others — that they succeed. In 
fact, that is the art of painting, and the art is not to be 
learnt in a book; but what is to be learnt there is the 
law of the contrast of colours, which may be made very 
profitable. 

The Contrast of Colours by Juxtaposition. 

Contrast of Black and White, 

White, placed beside black, makes the latter appear 
blacker and itself whiter ; but this effect is produced more 



THE LAWS OF COLOURING. 45 

and more strongly the nearer the two are brought together. 
Consequently, when a white band and a black one touch 
each other, the part of the white band which limits the 
black, seeming whiter than the rest of the band, the white 
stripe appears shaded like a white stick ; in the same way 
the part of the black band which limits the white, seeming 
blacker than the rest, the black stripe has the effect of a 
black stick. A succession of grey and white bands 
alternately side by side would give the impression of a 
fluted pilaster. This, applicable to all colours, which are of 
different luminous intensities, will produce each time only 
two tones, containing each more or less white or black than 
the other. 

Contrast of Colours in Juxtaposition, 

1. When two colours which follow each other in the 
order of the spectrum are placed side by side, they take 
more and more, in proportion as they approach each 
other, the aspect of the colour which precedes or follows 
them. 

Example : — Red and orange : the red which verges on 
orange approaches the crimson colour which precedes it ; 
the orange which verges on red approaches the yellow 
colour which follows it. Yellow beside green becomes 
more orange ; green beside yellow more blue ; blue beside 
ultramarine becomes greener ; ultramarine beside blue more 
violet; violet beside crimson more ultramarine; crimson 
beside violet redder, etc. 

2. When two colours separated by another in the order 
of the spectrum are in juxtaposition, the same results are 
obtained. 

Example : — Red beside yellow becomes more crimson ; 
yellow beside red greener, etc. 



46 SCIENCE OF PAINTING. 

3. When two colours are separated by two others in the 
order of the spectrum they are, as has been said, comple- 
mentary ; then they do not change when in juxtaposition, but 
they intensify. 

Example: — Red beside green increases in intensity — it 
becomes a brighter red ; green beside red appears a brighter 
green, as do all the colours with their complements. 

4. When two colours separated by more than two others 
in the order of the spectrum are in juxtaposition, each 
approaches the complement of the other. 

Example: — Red and blue. Red beside blue verges on 
orange, complementary to blue it becomes more orange ; 
blue beside red verges on green, complementary to red 
it becomes greener. Red and ultramarine, — Red beside 
ultramarine verges on yellow, complementary to ultramarine 
it becomes more orange ; ultramarine beside blue verges on 
green, complementary to red it becomes bluer. — Orange 
and ultramarine. Orange beside ultramarine verges on 
yellow, complementary to ultramarine it becomes yellower ; 
ultramarine beside orange verges on blue, complementary 
to orange it becomes bluer, etc. 

After these explanations, it is easy to understand how the 
aspect of a colour may be modified without changing it. 

When you have exhausted all the resources of the palette 
to make a colour intense, you can still increase its brilliancy 
by cleverly surrounding it with objects of its complementary 
colour ; if, on the contrary, you find that a colour is too 
pronounced, you can soften it by surrounding it with objects 
of the same colour, more intense. 

Example : — An orange drapery can be rendered yet more 
orange surrounded by blue tones ; a red surrounded by green 
tones will seem redder, etc. A portrait may have carnations 
that one thinks rather too red, but does not want to change. 



THE LAWS OF COLOURING. 47 

The normal aspect may be given by a red background : if it 
is too pale it will become pinker with a green background, 
etc. 

Nature has at its disposal luminous and colouring intensi- 
ties which we have not on our palette. We are therefore 
obliged, in order to imitate the phenomena produced by 
nature, to exaggerate them. It is therefore necessary to 
know them. 

Let us resume our former example, where we saw that the 
smoke of a hut appeared bluish on the dark background 
of trees, and reddish on the sky. If, after having painted 
the trees and the sky, we take the uniform tone to represent 
smoke, we shall not obtain the same result as in nature. Our 
sky has not the luminous intensity of the real one, and to 
give the appearance of it we have exaggerated the dark- 
ness of the trees; we must therefore also exaggerate the 
blue tone of the smoke when passing over the trees, and 
its orange tone on the sky. 

If we paint this smoke according to nature, we shall make 
this exaggeration instinctively ; but if the hut does not 
smoke that particular day, and we do not know these laws, 
it is more than probable that we shall carefully paint a smoke 
false in tone. 

Finally, what we wish to have understood is, that a know- 
ledge of the laws of colouring facilitates the work of the 
artist, by enabling him to give reasons for the causes which 
produce the different effects that are made by colours in 
nature, in the same way that drawing becomes easier when 
perspective and anatomy are known. 



CHAPTER IV. 

WITH THE SCIENTISTS. 

The laws of colouring, as they have been formulated in the 
preceding chapter, unite almost all the results made by dis- 
coveries up to the present, but presented in a form especially 
suitable for artists; for men of science have been more 
inclined to the study of the coloured rays than to that of 
concrete colours. 

This theory, therefore, has nothing new but the form in 
which it is presented* Rule without exception, absolutely 
demonstrated, universally controlled and recognised, it is 
at last the truth. 

To explain the reason of it is quite another matter. 
Learned men are not agreed upon this subject, and when 
" doctors differ " the majority of people find it difficult to 
form an opinion. 

The best thing would be to wait, but artists are impatient 
to know what is hidden at the bottom of this mystery, — all 
the more so that we are enticed by treatises on harmony 
of colours by following which every one can (at least so 
they are promised in the prefaces) instantly become a 
great colourist. This is very tempting. If therefore any 
one is on the point of plunging into the furnace, let him 
first listen to this. 

A young artist, anxious to know the reason of everything, 
prowled unceasingly round the domain of science, that sacred 



WITH THE SCIENTISTS. 49 

grove where the pontiff scientists hide from profane eyes 
the secrets they discover from nature. One day the young 
artist finished by penetrating into the mysterious sanctuary, 
where a ta]l old man with a keen and cunning look im- 
mediately came to him. This grave personage carried over 
one arm skeins of wool of all shades, and in the other 
hand he held a disc, divided like a cake into parts of all 
the colours of the rainbow. He spoke in a loud voice : 
"Young man, the senior student, to-day a centenarian, 
welcomes you, and knowing the object of your visit, he 
congratulates you on having found immediately the best 
guide whom you could follow. My system is marvellous : it 
explains everything; it replaces everything. No more of the 
antiquated names by which colours have been named : we 
shall hear no more turtledove grey, nymph pink, dead- 
leaf, or Dauphin brown ; but for example, in such a case, 
the fifteenth tone of the reduced yellow scale, seventh, 
eighth or ninth shade, according to whether the Dauphin 
brown were more or less green." 

" Yes," thought the young man. 

"And see how simple it is," continued the old man, 
showing his disc. "Do you seek the complement of a 
colour? Exactly opposite, following the diameter, — no 
error possible ; obligatory harmony for everything. 

"I regulate the toilet of ladies, military uniforms, the 
arrangement of gardens and salads; I regenerate the art 
of the upholsterer, of the glazier, of the artist, and of the 
decorator. 

" Ah ! this chromatic circle is a work of genius. And 
mark well, young man, that in writing on these subjects a 
volume of 730 pages, I have done nothing lightly. I tell 
you so in my preface. I have submitted each experiment 
to my pupils, to my friends ; and it is not the judgment of 



50 SCIENCE OF PAINTING. 

my own eyes that I have written, but the average judgmenc 
of many." 

" Pardon," insinuated the young artist ; " you appear to 
confess by that, that your arrangements of colours may 
present different effects to different people, in which case 
your universal system would cease." 

" One moment, young man. Do not try to make me say 
what I think; at my age we don't do that. It must be 
admitted that my system is applicable to every one; with- 
out that it would be useful to no one. The hypothesis must 
also be admitted on which it is constructed, of three simple 
colours, red, yellow, and blue ; and of three colours composed 
by the mixtures of simple colours, orange, green, and violet ; 
otherwise, I could not divide my circle into corresponding 
parts : nothing would harmonise ; there would be confusion, a 
mess — if you prefer a mess.'' 

" No ! no ! only you are suppressing one of the colours of 
the spectrum." 

" Which, please ? " 

" Well, ultramarine, it seems to me." 

** You say ultramarine ? Yes, what in my time was 
called indigo : you see it has even changed its name. But 
it is not really a colour. It is a spurious mixture of blue 
and violet, the favourite of laundresses, in any case worse 
than useless, an intruder, a hindrance. No, but do you see 
it in my circle ? It prevents it from being perfectly round. 
As well put up my disc at once, and restore the Gobelins 
to Louis XIV." The noble old man, going away visibly 
ruffled, exclaimed these last words : " Presumptuous young 
man, from the moment that you defend indigo, you may 
choose another guide." 

In fact, the young artist, turning round, found himself 
before two other personages. 



WITH THE SCIENTISTS. 5 1 

"I present to you the celebrated Thomas Young, the 
pioneer whom I am proud to have followed," said one of 
the two, introducing, his colleague ; " the first half of our 
common glory." 

" And I," said the other, " present to you in my turn the 
celebrated Helmholtz, my worthy successor, the second 
half. — Well, young man, then you do not adopt the 
hypothesis of that obstinate old man ? " 

" Our system," continued the celebrated Thomas, " ex- 
plains everything, replaces everything ! Our three funda- 
mental colours " 

" Ah ! you have also three colours ? " 

" Yes, but they are not the same : ours are red, green, and 
violet. We suppose the retina to be composed of nervous 
rootlets united in threes, and we suppose that each of the 
three is sensible of one of our three colours." 

" Ah ! you suppose also ! " sighed the young artist. 

But the " worthy successor," understanding the thought, 
added diplomatically : " Remark that Thomas had made 
those suppositions long ago ; I had, therefore, nothing to 
suppose when I presented that theory whose glory we 
share. After reading our works you will be doubly con- 
vinced." And the two men of learning took leave of the 
young artist, each cordially pressing one of his hands. 

The apprentice of learning, somewhat discouraged at this 
beginning, sought no more guides, and decided to penetrate 
the mysterious labyrinth alone, listening here and there, 
sometimes to the pleadings of David Brewster, the intrepid 
defender of the three primary colours, and of J. J. Muller 
and Maxwell, Thomas Young's disciples; sometimes new 
theories about the retina containing three visual substances 
with six fundamental sensations, or even the theory of the 
waves producing on the retina different compounds according 



52 SCIENCE OF PAINTING. 

to their length; sometimes also, the fantastic lucubrations 
of demented brains, rules of music applied to painting, 
chromatic pitch, chromometer, etc. Even the lamentations 
of the forgotten and ignored, such as Wiimst, who professes 
to be the discoverer of Young's theory, and poor Newton 
who cannot forgive the theft of his disc : " I invented it 
first," he often said with bitterness; only I made no 
flourishes to attract loungers ! " 

In short, when our young artist came out of this domain 
of science, his hair was grey, and he was more than 
fifty years old. Common Sense was awaiting him at the 
door. 

** You are here at last ! '* cried he (Common Sense is a 
companion of childhood that we often lose sight of in life, 
but who always considers us children). " Have you, at last, 
adopted a system ? " 

" No." 

** So much the better ! " 

** Yes, but I have made one ! " 

" So much the worse ! " 

" Oh ! don't laugh : my system is admirable ; it explains 
everything, it replaces everything. Here is the principle : 
bodies, whatever they may be, absorb the light which they 
receive, up to a point variable in each body, when they 
become saturated with light ; then only they begin to de- 
compose it in a certain proportion still variable, and at last, 
when they can neither absorb nor decompose any more 
light, they send it back with the coloured rays which they 
have not absorbed." 

** Very good ! that is no worse than anything else ; but 
are you quite sure about it ? " 

" Well ! I suppose it : if my hypothesis be not admitted, 
my system no longer exists." 



WITH THE SCIENTISTS. S3 

Then Common Sense began to laugh — a laugh terrible to 
hear. 

" How ? " he resumed : " you find all systems bad because 
they rest upon suppositions, and in order to replace them 
you invent one more, also a supposition. It is time to 
beware of that ! " 

" Then, if my system is not good, what am I to say to my 
colleagues, who are simple enough to ejcpect my revelations ?" 

" The truth." 

" The truth ! Am I then to tell them that, in harmony of 
colours, there is no absolute rule ? " 

" Exactly so." 

" That beyond the elementary laws of colours, there is 
nothing we can apply in all the theories known up till now ? " 

" Yes.'' 

" That artists should only take advice from nature, and, the 
better to understand it, should study the manner in which 
the great masters have interpreted it ? " 

"Wonderful!" 

" Then, they must be told also that there were magicians 
called Veronese, Rubens, Delacroix, and many others, who 
knew more about colouring than any scientist in the world ; 
for with their colours they have created a language which 
speaks to the soul, which communicates feeling and life, 
long before science has even suspected that coloured rays 
influenced the brain." 

" Bravo ! That really is the truth ! " 

" If this be the case, as well as immediately confessing 
to my colleagues that I thought to astonish them by my 
learning, I must tell them that all I bring back from my 
journey to the scientists is limited to this advice : Don't do 

as I have done, don't lose your time in seeking that which 
does not exist ! " 



54 SCIENCE OF PAINTING. 

" Well ! but acknowledge it without blushing — at your age 
one may still acknowledge — this advice will be valuable, 
should it serve to spare others the worry you have given 
yourself, and that will restore a little the inflation of pedantry 
of which I have just seen you deprived. The pedant, do 
you see, is detestable because he lacks charity. He thinks 
in his vain egotism : * I have grown pale over volumes, I 
have searched dictionaries, I have scrawled notes, I have 
dissected, analysed, and that for years, to discover some- 
thing ; and this something, I would go to tell in two words 
to others, who would thus know it without trouble. Ah ! 
no, let them learn first to understand the noble phraseology 
of science, for I do not speak a language comprehensible to 
the vulgar crowd : I call a colour a pigment ; a paper horn 
a spiral cone; and the good God, Lord Archetype or 
Demogorgon ! Afterwards the converts will swallow my 
prefaces, the recital of my unsuccessful theories, my refuta- 
tions to my adversaries. 

" * I will present problems without giving the solutions of 
them, I will develop hypotheses which I shall afterwards 
destroy, I will scatter Latin and Greek quotations without 
translation, archaeological notes supported by documents, 
etc., etc., and the useful substance I shall only give out 
little by little, bits at a time. If I ever see a colleague 
engaged in a search which I have followed, and which leads 
to nothing, I will let him have his turn at it, let him get 
embarrassed as I did, let him wander as I wandered, even 
if he should perish where I was able to pass. Ah ! but it 
would be too convenient then ; they would only have to 
fold their arms, and to assimilate science from others with- 
out seeking it themselves ! ' Dull pedant ! you can never be 
covered with enough contempt ; but with how much respect, 
honour, and love, may be hallowed the memory of those 



WITH THE SCIENTISTS. 55 

true scientists who work throughout their lifetime in order 
to leave to the world a single phrase which may be written 
in the book of human science ! 

" But you make me forget my duties," cried Common 
Sense, interrupting himself ; " to-day I must preside at an 
assembly of artists ; I have been absent from those assem- 
blies several times, — they will begin to think that I don't 
wish to appear there any more." And he went away. Let 
us hope that we shall meet him again ! 



CHAPTER V. 
COLOURING SUBSTANCES, 

In taking, to determine the laws of colouring, the compounds 
of colouring-matter which may best represent the free 
colours of the solar spectrum^ we have made a theoretic 
palette ; but the exclusive use of that palette would not be 
practicable for painting. 

In the first place, the substances which compose them 
are not all solid, and some of their mixtures would produce 
chemical reaction capable of changing them. Further, those 
colours are not found ready made, and their manufacture, 
which could scarcely be counted upon with absolute cer- 
tainty, would be expensive. 

Then why should we deprive ourselves of earths, ochres 
and marls which are quite sufficient for broken tones 
frequently wanted, and which join to a perfect fixedness the 
precious qualities of covering well and of drying easily ? 

Do not let us banish, from prejudice, any colouring-matter 
from our palette ; for, as M. de la Palisse might have said, 
" All that can be used are useful," always provided that they 
are substantial, and that is what we have now to consider. 

Ancient artists, in the time of Apelles, had only four 
colours : chalk white, yellow ochre, red ochre, black. 

Are we quite sure of that ? Pliny, who came some cen- 
turies later, affirms it, and he tells us further that in his time 
painting was already enriched by a large number of new 



COLOURING SUBSTANCES. 57 

colouring-matters, whose nomenclature is here re-estab- 
lished in modern language : — 

Chalk white, variously produced. White lead, and its derivatives. 
Massicot and minium orpiment (sulphur of arsenic, red, and 

yellow). 
Red lac — lakes of purple colours, prepared from shell-marl. 
Natural and burnt ochres. 
Cinnabar (native vermilion). 
Indigo. 

Blue pulverised enamels. 
Verdigris. 
Brown earths. 
Various blacks prepared from the combustion of different bodies, 

e.g,^ ivory, grapestone, etc. 
Sepia. 

And Pliny laments this profusion of colours, regretting 
the time when there were only four of them. He cries : 
" To-day, when purple even covers our walls, when India 
procures to us the coloured sand from its rivers and colours 
drawn from the blood of its dragons and its elephants, we 
have no longer noble paintings. Then, when we were poorer 
in materials, we really were richer in art. It is no longer 
soul that one paints, it is the luxury of personages. It is 
the material that is now appreciated in art." 

Were it not that we know that Pliny wrote that more than 
eighteen hundred years ago, we might believe that we were 
reading an article of yesterday. Yes ! if art be always young, 
we may say that criticism has always been old. 

In spite of Pliny, the domain of painting continued to 
increase. 

Means of preparing yellow lakes from buckthorn, and red 
lakes from cochineal and certain woods, and finally madder, 
were discovered after his time. 

For blue lapis was used, and the palette was enriched by 
new terre-vertes and browns. 



S8 SCIENCE OF PAINTING. 

However, chemistry did not yet exist. Painters, confined 
to the productions of nature, cared only to procure them as 
pure as possible. 

In a bam of Antwerp Museum there exists a trunk which 
belonged to Rubens, carefully preserved, and in which he 
had stored away collections of pigments gathered during 
his travels. Besides the inestimable value attached to this 
souvenir of the artist, this trunk is for us a valuable lesson. 
One learns by it the personal trouble which the great artists 
took in selecting their pigments, and the authentic specimens 
this trunk contains permit us to learn exactly the materials 
with which the pictures we so much admire to-day were 
painted, and to choose amongst them those which are best 
preserved. 

White lead, cinnabar (native vermilion), lapis, charcoals, 
madder lakes, earths and ochres have resisted very well ; but 
buckthorn, like all yellows, reds and vegetable greens, has 
more or less disappeared. Those results should be noted. 

Since the time of Rubens, many new colours have been 
invented, and science constantly furnishes new ones ; unfor- 
tunately more attention is bestowed upon their brilliancy 
than upon their solidity. 

The discovery of aniline amongst others has been quite a 
catastrophe for art. 

It is true that as soon as a colour is reputed bad, con- 
scientious artists dismiss it from their palette ; but it quickly 
reappears disguised, like swindlers who change their name 
to make new dupes, and it becomes very difficult to recognise 
those bad materials in the clever mixtures in which they are 
concealed. 

So, from fear of being deceived, certain artists fall into 
an excess of distrust which prevents them from using new 
productions that they might safely employ. 



COLOURING SUBSTANCES. 59 

Without knowing enough of chemistry, they know too 
much of it and take fright at certain names. Thus, know- 
ing the misdeeds 'of chrome yellow, they hesitate to use 
oxide of chrome (emerald-green), one of the best colours 
existing, because they do not know that the most terrible 
substances may become inoflfensive when they are mixed. 
For example, pour into one glass some muriatic acid 
and into another glass a concentrated solution of caustic 
soda ; then, into each of those glasses throw little pieces 
of meat : they will be instantly dissolved under your eyes. 
Then, mix the contents of the two glasses by pouring the 
one into the other and — swallow the whole ! It will taste 
just like a glass of sea-water, nothing more. Those two 
rightful corrosives are transformed into chloride of sodium, 
which is merely common kitchen salt. Chlorine is another 
substance that one is still desirous to see amongst pigments, 
for everybody knows it destroys almost all other substances. 
When it is alone, yes ! — but with others it is often perfect, — 
like a policeman, implacable in uniform, but tender and 
gentle in the bosom of his family. 

It will therefore be preferable, instead of studying pig- 
ments separately under names which are not real, and 
allowing ourselves to be guided by prejudices accompanying 
these names, to group the pigments according to their deri- 
vation, and to consider their general qualities and faults. 

We can thus establish five categories of colours : 

First Category : Vegetable colours. 
Second ,, Animal ,, 

Third „ Mineral ,, 

Fourth „ Colours obtained by vegetable and 

mineral combinations. 
Fifth „ Charcoals. 

l!:\i^ first category includes coloured substances procured 



6o SCIENCE OF PAINTING. 

directly from vegetables, fresh, dried or torrefied, such as 
iris green, chicory brown, coffee brown, indigo, gamboge, 
saffron yellow, etc. All the colours of this category are 
bad: they fade from exposure to light, some of them 
change tone on. contact with fat bodies, and others are 
frequently destroyed by mineral combinations with which 
they are mixed. 

The second category includes coloured matter procured 
from animal substances, such as purple, Indian yellow, 
carmine of cochineal, sepia, etc. 

Purple, which was produced from shell-marl, is now only 
known by name, and the recipe for its manufacture is lost ; 
but now a similar product is obtained from the purpurate of 
ammonia obtained from uric acid. 

It is said that Indian yellow is obtained from the excre- 
ment of the chamois or of cows fed on certain plants ; in 
any case it is a very alkaline substance, which changes oil 
into soap, and may become, consequently, soluble in water, 
if the grinding is not carefully done. 

Carmine fades in light. 

Sepia is solid in water-colours, but does not grind well 
with oil. 

The third category includes all combinations of metallic 
basQs, whether natural or obtained by chemical processes ; 
some are to be found in a free state, like carbonate of 
lead (white lead) and sulphide of mercury (cinnabar), whilst 
others are more or less firmly fixed in coatings of clay to 
form the coloured earths to which we give the name of 
ochres, or in silicious matters to form stones like malachite 
and lapis. 

All these mineral colours are generally solid, but they are 
not of a good homogeneous tone ; and although after being 
powdered, they may be washed with great care, one can 



COLOURING SUBSTANCES. 6 1 

never quite succeed in getting rid of the impurities which 
they contain. This is detrimental to their brilliancy. 

It will be understood, therefore, that in re-making by the 
aid of chemistry the same combinations met with in nature, 
and by establishing them on pure and uncoloured substances 
like aluminum and silica, which are the bases of natural 
clays, we obtain those same colours quite as solid and much 
more beautiful. It is thus that marls reproduce all the red 
and yellow earths coloured by oxide of iron, and that Guimet 
ultramarine is the reconstitution of lapis-lazuli as vermilion 
is that of cinnabar. 

Chemistry does not merely confine itself to reproducing 
combinations which may be found in a natural state; 
chemistry has already given us many others, and it is to be 
hoped that it will continue to enrich this category of mineral 
colours to which it has already added so much precious 
matter. It is true that on the other hand it has given us 
some useless and even bad, which we must be careful not 
to use : we shall therefore devote a chapter to the practical 
means of recognising them under whatever name they may 
be called, and in whatever mixture they may be introduced.* 

The fourth category includes all vegetable and mineral 
combinations whose principle consists of fixing on aluminum 
or silica vegetable dyes dissolved in water by means of 
precipitation. 

In this way are obtained red lakes, with dyes of madder, 
Brazilian wood, Pernambuco wood, Campeachy wood, etc., 
and the yellow lakes with dyes of woad, Avignon berries, 
buckthorn, etc. These last often bear the primitive name 
of stil de grain. 

All the colours of this category are bad ; they fade in the 
light, and are changed by contact with certain mineral 

* See Appendix — " Verification of Colours." 



62 SCIENCE OF PAINTING. 

colours ; they should not be used. We must here, however, 
except the madder lakes, which are comparatively solid, and 
which are indispensable, because we have no others. 
Besides, by taking certain precautions, we can minimise the 
inconveniences. As for yellow lake, it can be advantageously 
replaced by iron lake, which, in spite of the diffidence natural 
to an inventor, we recommend as being of perfect solidity. 

The fifth category includes charcoals produced by the 
calcination of certain vegetable or animal matter, such as 
peach kernels, wood, cork, vine shoots, chestnuts, ivory, 
bones, etc. 

This category furnishes only blacks, all of which are good. 

We have only to reject bistre and lampblack, which are 
bad on account of the tarry matters contained in them.* 

Bitumen, which we have not classed with mineral colours, 
will not find place with charcoal either, for it must be 
formally excluded from painting. It is the plague, the death 
of pictures. It never dries thoroughly, or at least it softens 
and runs as soon as the temperature rises above 30° to 35° 
per cent By mixing it with a very siccative oil, you may 
give it an appearance of solidity, but, sooner or later, it is 
certain to run and exude from the canvas. It is all the 
more destructive for being used to prepare foundations; 
and pictures thus painted upon foundations which are always 
soft, must, of necessity, crack. 

To give examples caused by ravages owing to the use of 
bitumen, it is sufficient to refer to the canvases in our 
museums which it has already been necessary to restore 
several times, such as the " Shipwreck of the Medusa,", by 
Gdricault, the " Portrait of Cherubini," by Ingres, and so 
many others, alas ! 

* It is possible by careful preparation to get a lampblack free from 
tar. 



COLOURING SUBSTANCES. 63 

But the fanatic lovers of bitumen answer you : " That is 
not the fault of bitumen, it is the manner in which it is 
used." Here^ then, is another example. A well-known 
picture dealer, who is also an intelligent collector, has suc- 
ceeded in collecting a large number of palettes which had 
belonged to artists of renown. These palettes were taken 
after the day's work of the artist) was over, and not only 
were they covered with the pigments used, arranged in the 
order habitual to the artist, but they still showed all the tones 
improvised whilst actually painting, and on many of them the 
artist had painted a little bit, according to his own method. 
We have thus many specimens of almost all the' methods 
in which bitumen can be used. Those palettes as well as 
pictures are hung on the wall. They are taken good care of, 
as you may suppose, and even if they are subject to sudden 
changes of temperature, those changes are common to all. 
Well ! all the palettes having no bitumen are in perfect 
condition, exactly as they were left by the artists ; but in all 
cases where bitumen has been used, the bitumen has run ; 
not merely the small quantity arranged in its place with the 
other colours, but also the tones mixed with it. Is this con- 
clusive ? At least the bitumen enthusiasts cannot pretend 
that no artist knows how to use bitumen. This unique 
collection will be bequeathed by its proprietor to the Louvre 
Museum, and it will be a great lesson for the future. 

Some artists pretend to have substantial bitumen ; they 
either deceive themselves, or are deceived. Colourmen 
give them a false bitumen made with yellow lakes and 
aniline black. Those false bitumens fade in the light. 
Real bitumen also fades. 

However, if bitumen is essential to certain artists, it is 
quite possible for them to make a bitumen with substantial 
pigments united with normal resin soluble in oil, and 



64 SCIENCE OF PAINTING. 

not melting at a low temperature. This imitation bitumen 
will have all the qualities of the real bitumen in the way of 
convenience, and will not have its disadvantages.* It will 
have the additional advantage of not fading in light. As for 
mummy-umber, that is still bitumen, and the few particles 
of Pharaoh which it may contain must not induce us to 
accept it. 

We give (Appendix — " Good and Bad Colours ") detailed 
explanations on good and bad colours ; but for those whom 
these details may tire, here is the list of the colours which 
may be used with perfect certainty : — 

White lead (carbonate of lead). 

Zinc white (oxide of zinc). 

Cadmium yellows (sulphide of cadmium). 

Strontia yellow (chromate of strontia). 

Zinc yellow (chromate of zinc). 

Iron lake (oxide of iron on aluminium basis). 

Vermilion (sulphide of mercury). 

Madder lakes (madder dye on aluminium basis). 

Cobalt blue (oxide of cobalt on aluminium basis). 

Emerald green (oxide of chrome). 

Mineral violet (phosphate of manganese). 

Cobalt violet (phosphate of cobalt). 

Further, all the natural and burnt ochres, all natural and 
burnt earths having oxide of iron for basis, are equally good, 
as well as all the marl colours, which are oxide of iron at 
diflferent degrees of calcination on aluminium basis. As 
for blacks, they are all good except lampblack, containing 
some tarry matters. 

From this list we exclude all colours on lead bases, such as 
chrome yellows (chromate of lead), Naples and antimony 
yellows, massicot and minium, which are white lead more or 
less calcined, because those metallic combinations are liable 

* See Appendix—" Brown Colours.*' 



COLOURING SUBSTANCES. 65 

to get black when brought in contact with the air, and they 
may be replaced by others ; still they may be used if certain 
precautions are taken, and also Veronese green and certain 
other colours. (See Appendix — "Yellow and Orange 
Colours.") 

If we have not rejected white lead itself, it is because 
there is no equivalent for it known up till now : its covering 
and drying qualities, and the hardness which oil imparts to 
it, make it indispensable. Still it is very dangerous to use it 
with sulphides such as vermilion and cadmiums, with which 
we consider nothing but zinc white should be mixed. For 
cadmiums this precaution is useless if they are well manu- 
factured. 

This question of the chemical solidity of colouring-matters 
is excellent for the preservation of painting ; unfortunately 
artists will never give it their personal attention ; many of 
them will not even read the chapter in which we shall give 
precautions to be taken for the manufacture of pigments 
and their use, as well as the practical means of analysing 
them. (See Appendix — " Good and Bad Colours.") 

Colourmen should therefore be forced to furnish good 
materials, and here is a means which we consider excellent 
for obtaining this result. 

Artists should insist, when they buy a tube of colour, 
that the ticket bears, in addition to the usual name of the 
colour, its chemical formula according to the above list. 

In this way, if the colourman does not furnish what he 
professes, he can be summoned for fraud ; there is deception 
about the quality of the merchandise. Whereas now we 
cannot even complain, because the names Capucin lake. 
Geranium lake, China rose, given to all sorts of concoctions, 
profess nothing, any more than golden yellow, malachite 
green, Venetian red, etc. 



1 



66 SCIENCE OF PAINTING. 

For instance, you buy a tube of celestial blue : this blue 
is made of Prussian blue, or of anything else ; it is of no 
consequence to anybody ; the colourman may call any- 
thing he pleases celestial blue. You evidently consider it 
sufficiently celestial since you have taken it. Yet if artists, 
seeing that this celestial blue is not substantial, should cease 
to ask for any more of it, it would discard its name and 
reappear, with more or less white, under the names of azure 
blue, peacock blue, turquoise blue, sapphire blue, Smyrna 
blue, etc. We are still far from having exhausted all the 
names of precious stones, flowers, towns, birds, of which the 
colourmen's vocabulary is composed; and if the reform 
which we propose should have no further result than to 
render useless all these fantastic appellations, it would even 
then do good service, for the number goes on increasing in 
ridiculous proportions. If we do not stop soon, there will be 
thousands of those new shades, which are, as a rule, merely 
common pigments of bad quality dyed and done up with 
aniline products, all fading in the light. 

From a technical point of view, it is also puzzling if 
different people give to the same thing different names, or 
the same name to different substances. Thus, an author in 
whom you have every confidence asserts to you that ver- 
milion is solid ; you therefore make use of it, but instead of 
the sulphide of mercury recommended to you, it is iodide of 
mercury or dyed minium or anything given to you under 
this name of vermilion : not merely do they sell to you at the 
rate of 15 francs what is worth 40 sous ; but they compromise 
your work. It is a swindle and an abuse of confidence, 
which could not occur if you bought your colours under their 
true names. Ask a druggist for an anti-fever powder, and 
he may give you a little lentil flour sweetened 3 but if you ask 
for sulphate of quinine, he is obliged to give you some, as 



COLOURING SUBSTANCES. 67 

the colourman will be forced to give you whatever may be 
stated by the ticket on his tubes. But, some one will say, 
this colourman is himself deceived, for often he does not 
manufacture the colours he sells. In that case, when buy- 
ing his primary materials, let him exact from his furnishers 
the guarantees which his customer requires from him, and 
you may be sure, should the subject ever be one for litiga- 
tion, he will know how to make the true perpetrator of the 
fraud responsible. 

The only serious objection which could be brought 
against it is this : you cannot force colourmen to make their 
tickets as you ask. That is true, but neither can you force 
artists to buy there rather than elsewhere ; and it will be 
enough for one colourman to begin, for all the others to 
be obliged to do as much under penalty of losing their 
customers, for to refuse to give the guarantees given by a 
colleague would be to confess intentions of inveterate fraud. 

Further, this guarantee of chemical formulas, which 
might be immediately obtained, is not the only one which 
we might ask : in a future perhaps nearer than we think, 
we shall have many more guarantees, and if the project 
which we have submitted to the " Society of French Artists " 
is accepted, the members will no longer have anything to 
desire with regard to the purity and good fabrication of the 
productions they require. 

This is the style of project : — 

I. That a permanent commission on the material 
processes of the arts should be named by the committee. 
It would be composed of members of the society — artists, 
sculptors, engravers and architects; whilst all branches of 
art having, from a practical point of view, problems to solve 
and advantages to draw from the work of this commission, 
are interested in being there represented. 



68 SCIENCE OF PAINTING. 

Members foreign to the " Society of French Artists " — 
chemists, manufacturers, etc., whom their capabilities would 
render useful — could be added to the commission by a 
temporary or definite title. 

The duty of this commission would be to study all inven- 
tions and all processes, both ancient and modern, and to 
indicate, in special reports, those which might seem to them 
preferable ; to receive and to class communications made 
to them ; to reply to questions which might be addressed 
to them ; in short, to centralise all that might be said or 
written on the matter. 

The commission would have the power of preparing all 
treaties and conventions with manufacturers and dealers 
in products destined for the arts, which treaties and agree- 
ments would not bind the society until after having been 
regularly accepted by the committee. 

2. There should be added to the monthly bulletin of the 
society a rubric the direction of which should belong ex- 
clusively to the said commission, who might introduce into 
it all communications, correspondence, articles scientific or 
otherwise (even when emanating from collaborators foreign 
to the society), should their publication be found useful. 

3. There should be founded a laboratory where the 
society would maintain a chemist charged with studying the 
questions'submitted by the said commission, and with making 
all analyses required by the artists, manufacturers or dealers. 
The analyses might be charged at prices which would enable 
the society to refund its expenses. 

4. The treaties between the society and the dealers or 
manufacturers should be made upon the largest possible 
bases — />., the society would grant no monopoly to any one, 
and would exclude no one. The society would be satisfied, 
abandoning all idea of commerce on its own account, to 



COLOURING SUBST/^NCES. 69 

authorise absolutely without fee the said dealers and 
manufacturers to put a mark determined by the society and 
belonging to it, upon those of their products which the 
society bad recognised as good, after the decisions of the 
said commission on the material processes. 

Each dealer or manufacturer, on depositing the sample of 
the product which he desired to have stamped, would bind 
himself in writing, under penalty of a heavy fine in case of 
non-fulfilment, to manufacture always a product identical with 
the sample, which would be guarded under double seal to 
bring forward as a proof should litigation ever become 
necessary. 

Artists, being afterwards informed that the products 
stamped by the society are guaranteed of pure matter, of 
good manufacture, and in no way injurious to the preserva- 
tion of their works, will have the right, it will even become 
their duty, to insist that their furnishers submit their goods 
to this stamp, as it will be refused to no deserving person. 
Let no one say that this project of treaty with manufacturers 
is a chimera ; for we can name already the house of Lefranc 
& Co., which is quite disposed to be the first to sign. 

As for the necessity of assuring the greatest possible 
durability to our works, some critics sneer at this as at 
a ridiculous pretension, and some artists, through false 
modesty, consider it may be neglected ; but we are of 
opinion that it is only honest, and that honesty in everything 
is the best policy. 

In fact, as we sell our pictures, we make of them mer- 
chandise, and all merchandise which deteriorates and loses 
its value in the hands of the acquirer is soon discredited, — 
all the more so that to-day the prices at which amateurs 
acquire works of art give them the right to be exacting. 

In letting it be supposed that modern painting can be 



70 SCIENCE OF PAINTING. 

unsubstantial, it is not only to ourselves that we should be 
doing wrong, it would be also to our successors. Yet it 
must be so. But as we cannot know what the future alone 
can demonstrate, it is well to let the fastidious care which 
we take be known, and also the guarantees with which we 
surround ourselves in the choice of the materials that we 
use. 



CHAPTER VI. 

OILS, GRINDING OF COLOURS, ESSENCES AND 

SICCATIVES. 

The colouring-matters being chosen, and offering the best 
guarantees of solidity, we have now only to grind them with 
an agglutinative of some kind, so that, reduced to the smallest 
possible particles, they may be in a condition suitable for 
whatever style of painting they are destined. 

We shall speak of gums, wax and other agglutinative 
substances used for this purpose when we shall study the 
different processes of wall-painting, water colours, distemper 
painting, pastel, etc. 

For the present, we shall only consider oil painting, which, 
being the furthest developed and the most generally used, 
is entitled to the first place. 

Oils. 

The name of oil has been given to many liquids which 
are neither of the same composition nor possessing the same 
properties. 

I. The essential oils are extracted by distillation, from 
certain plants, such as rosemary, lavender, fennel, etc., or 
from certain resinous balms, such as turpentine. Some are 
also obtained merely by pressure, like the essential oil of 
lemon. Now the name of essential oil is fallen into disuse ; 
those products in general are called essences. Essences 
dry by evaporation, but they leave a residue more or less 



72 SCIENCE OF PAINTING. 

viscous ; some are used in painting, and we shall notice them 
later. 

2. Etnpyreumatic oils are produced by the analysis of 
certain bodies by heat, such as oil of wax, oil of camphor, 
etc. Nearly all the resins burnt emit vapours which con- 
dense into empyreumatic oils. Bistre and certain tars are 
emp5n:eumatic oil of wood mixed with charcoal. These oils 
also dry by evaporation, but very slowly, and they leave yet 
more viscous residue than the essences, so they are not 
used, except oil of wax, an attempt to utilise which was 
made about 1830, but in a kind of encaustic painting with 
a basis of wax and resin : the author who speaks of it merely 
advises timidly the trial of it with oil paints. 

3. Animal oils are obtained chiefly by boiling the feet 
and hocks of animals, such as neat's-foot oil, sheep's-foot 
oil, etc., and they are also found in a natural condition under 
the skin of certain fish, such as whale oil. They are not 
siccative, and are of no use for painting. An oil is also 
prepared from eggs, either by pressing the yolks hardened 
in boiling water, or by putting the yolks into sulphuric 
ether, which dissolves the oil, that is afterwards collected 
when the ether evaporates. This egg oil is not yet of any 
use j but it is well to know of it, because it is certainly one of 
the principles of egg-painting, so much used formerly, and 
which has given such substantial results. This oil does not 
corrupt, like other animal oils, and perfectly dissolves cold 
resins, with which it forms varnishes comparatively hard at 
the end of some time, although used alone it is not siccative. 

It is not in short used ; but perhaps some day it will be. 

4. Fixed oils are procured by means of pressure from 
different vegetable matters which contain them. They are 
not all suitable for painting, and some are not siccative — such 
as olive oil, for instance. 



OILS. 73 

Those which dry present a peculiarity distinguishing 
them from essential and empyreumatic oils; they do not 
evaporate, on the contrary they increase in weight by 
drying, and this increase is due to the quantity of oxygen 
they absorb ; but, whilst increasing in weight, they diminish 
in volume. In fact, if you put a certain thickness of oil into 
a plate, at the end of some time a pellide is formed whose 
surface remains perfectly soft. Yet when the oil gets 
thoroughly dried the surface is lined, because the fresh oil, 
shut under the pellicle as under a skin, coming to dry in 
its turn and diminishing in volume, the same phenomenon 
it produced as when a balloon gets disinflated or a person 
gets thin, the skin becomes too large and forms folds. 

The term " to dry," applied to oil which passes from a 
liquid to a solid state is not appropriate, as nothing evapo- 
rates — quite the contrary. In reality, there is condensation 
and absorption of oxygen; but what happens with this 
oxygen ? Is there a combination ? Is a new body formed ? 
In any case the solidified oil no longer dissolves in any of 
the solvents of fresh oil, except benzine. And, on the 
contrary, the alcohols which do not dissolve fresh oil dis- 
solve dry oil. 

There has therefore been at least a serious modification 
in the nature of the oil to produce such great differences. 

Amongst the oils now used for painting there are two 
which are generally preferred : linseed oil, and poppy oil. 

Linseed oil is the more siccative of the two ; it acquires 
greater hardness and remains more transparent whilst drying 
than poppy oil ; but it is more viscous and gets more easily 
sour. In this last case, chemical combinations operate in 
the tubes with certain colours, especially those having an 
aluminium basis — such as lakes, for instance, which become 
like india-rubber. It is said of pigments arrived at this 

F.P. c 



74 SCIENCE OF PAINTING. 

condition that they are greasy, and can only be used when 
diluted with oil or essence ; but they should ncft be used. 
They should be entirely discarded, because they will never 
dry thoroughly. The use of colours ground with acidified 
oils is one of the principal reasons why pictures crack. 

We should always be careful, before grinding the colours, 
to assure ourselves by means of litmus paper that the oil 
is not sour; which often happens after submitting it to 
operations said to be for purifying it and rendering it 
siccative. 

The Grinding of Colours. 

In the process of oil painting, colours are used at different 
degrees of opacity and transparency ; we must therefore give 
to each of them one of those qualities, in the proportion 
which suits it best, and it is by an intelligent and sensible 
grinding that this result can be obtained 

Unfortunately, most of the people who grind colours for 
artists are merely concerned with the commercig,l side of 
this industry. To prepare colours which shall keep fresh in 
tubes the longest possible time and in all climates, such is 
their principal object ; but this object, good for the foreign 
market, is not so for us. If, unlike the ancient ajrtists, we 
do not ourselves grind the colours, we should at least be 
capable of doing so, in order to know if those to whom we 
entrust the important care of preparing our colours do it 
properly. 

People are not agreed as to whether ancient artists 
preferred to paint with linseed oil or poppy oil, and it is 
now scarcely possible to clear up this mystery : now only 
poppy oil is used, except for some dark colours, where the 
use of linseed oil is extolled. We shall not trouble the 
grinders with this subject, as it is really of little importance ; 



THE GRINDING OF COLOURS. 75 

and since poppy oil is preferred as rendering the colours 
less viscous, let us have poppy oil ! 

But what we cannot admit is the exaggerated quantity 
used — generally one-third more than really necessary. Now, 
as oil is pernicious for painting, because it darkens it and 
changes fatally with time, no more should be introduced 
than just sufficient to obtain solidity. 

Many artists, convinced of this excess, have adopted the 
custom of leaving their colours some minutes on blotting 
paper before using them. It would surely be more practical 
not to put so much in than to take it out afterwards. But 
the grinders allege that the colours would then be too dry 
to grind, that a great many of their customers never find 
them sufficiently liquid, and at last the eternal bad reason 
that they have always done so. The truth of the matter is 
that colours ground liquid keep longer, and then — oil costs 
less than pigment, and the more there is of the one the 
less there is of the other. Only the colours are so thickly 
charged with oil that they would run on the palette if wax 
were not added to restore some body to them; the more 
wax the more oil may be put : one might even do without 
any pigment at all. With a few grains of aniline dye, you 
may dye more than a pound of a gluten made of wax and 
oil, and- thus have colours superb in tone and of a very 
consistent thickness. 

In fact, we are brought back to the oil and wax method 
formerly invented by Taubenheim; and the great incon- 
venience which results from it is that the oil, sinking into 
the canvas or panel, leaves the wax on the surface, and that 
the following coating does not adhere to the preceding one 
because oil does not hold on wax. All artists have noticed 
that very often, when wishing to scrape away roughnesses, 
they raise a pellicle, and that by continuing they can take 



76 SCIENCE OF PAINTING. 

away a large piece which has not assimilated with the sketch 
over which it has been repainted. 

Besides this great fault, compromising the solidity of the 
painting, the introduction of wax into the colours reduces 
their opacity and intensity : not only do they no longer cover 
the canvas, but they deteriorate, for they derive their richness 
neither from oil nor wax, but from colouring-matter. 

Grinders allege still that wax gives body to the paste, 
which yields better to the palette knife, and that it gives to 
the colours a smoothness which all artists now seek. 

To this we answer that they can perfectly well grind closer 
than they now do (it is only a little more fatiguing). By 
putting less oil the colours remain dull without the need of 
wax ; and if the paste seems too firm in certain cases, it is 
easier to add oil than to take it out. 

Besides, there is a very simple way of satisfying everybody : 
it is to grind pigment ac'cording to our wishes for those 
artists who wish to return to sound tradition, and to continue 
grinding in the modern way for those who paint trowel- 
fashion, or undertake long voyages. 

By grinding colours with only the quantity of oil strictly 
necessary, we are able to introduce other useful substances 
to perfect the different qualities that we require from each 
of them. With more or less resin soluble in oil, cold, we 
shall increase at will the transparency of some, leaving to 
others all their opacity ; and if we fear that in this condition 
the paste will be too stiff to be convenient, we can increase 
its fluidity by means of a petroleum but slightly volatile, 
which, taking as long to evaporate as oil does to dry, will 
give us, whilst working, the feeling of a pigment containing 
much oil. If certain colours ground in these conditions 
showed a tendency to run, like vermilion for example, one 
might add to them, instead of wax, a salt of aluminum with 



ESSENCES. 77 

which the consistency of pomade can be given to oil without 
any inconvenience. The colours, being thus conveniently 
prepared, might be used as they are, especially for painting 
solid work. But it is necessary, in certain cases, to be able 
to increase fluidity, siccativeness, and transparency. It is 
to answer the call of these three indispensable qualities that 
the innumerable quantity, of ingredients has been invented 
which are mixed with colours on the palette, and which, 
under the names of unguents, pomades, balms, mediums, 
lotions, gluten, varnish, essences and siccatives, litter the 
studios, and are, without exception, poison for painting — in 
different degrees, however. We are about to try and put a 
little order into all this collection. 

Essences. 

If we wish to render a colour liquid, to sketch clearly, 
glaze or paint transparent and vaporous objects, we use an 
essence which distempers the colour. Many essences are 
used for this purpose : essence of lavender or aspic (a variety 
of lavender), essence of turpentine. 

All the essences procured by distillation from plants or 
resinous balms have the fault of becoming resinous by 
contact with the air. They get thick and yellow: it is 
then said that they are greasy. Arrived at a condition of 
bird-lime, they are no longer volatile, and consequently, not 
drying, they become a cause of cracks in the painting. 

One must be careful to rectify them, i.e., to distil them 
afresh before using them. 

In this rectification, the parts already resinified remain 
in the alembic, and the essence once more becomes limpid 
and colourless ; but in a short time the phenomenon occurs 
again, and none but recently rectified essences should be 



78 SCIENCE OF PAINTING. 

used, so as to diminish as much as possible this incon- 
venience ; as for suppressing it entirely, that is impossible, 
if merely from the fact that it evaporates on contact with 
the air; the purest essence becomes resinified, and there 
always remains a viscous residue which never dries, but gets 
yellow and attracts and retains all dust. A true manufacture 
of black. 

In fact, all essences, without exception, cause paintings to 
blacken, and become yellow. 

If they have not hitherto been discarded, it is because 
there has been nothing to replace them with ; but now we 
find in petroleums liquids offering many more qualities 
without inconvenience. 

Petroleums. 

Petroleum, by taking in distillation only volatile particles, 
evaporates without forming any residue. It serves as a 
means, and leaves nothing behind it. Spread on white 
paper it is impossible when evaporated to find even any 
trace of it. 

Further, the facility of having it at various degrees of 
volatility allows the work to be regulated according to the 
desire of the artist. We have obtained some essences of 
petroleum which evaporate in five minutes, others in an 
hour, others in several hours, and even in several days (see 
next page). At this point it will be useful to make a 
little observation. It may seem that very volatile petroleum, 
evaporating in five minutes for instance, and petroleum but 
little volatile, only evaporating in several days, mixed in 
different proportions, would be sufficient to obtain all the 
degrees of volatility. That is an error. The petroleum 
which evaporates in five minutes is distilled between loo 
and 150 degrees of heat; that which only evaporates in 



PETROLEUMS. 79 

several days is distilled between 300 and 350 degrees of 
heat. Now, if you put half of the one and half of the other, 
say twenty grains in all, into an open vase, at the end of 
five minutes only ten grains will remain ; that which evapo- 
rates in that length of time will be gone, but the remaining 
ten grains will require some days to evaporate. 

These essences of petroleum should therefore be care- 
fully kept apart, and not mixed together except in cases 
where one might reasonably benefit from those differences of 
volatility. For instance, having to paint a sky rapidly, you 
wish your colour to be very liquid, to spread it on easily, and 
afterwards suddenly less liquid, in order to finish. You will 
take then, as a liquid to mix your colours, a mixture com- 
posed of a petroleum evaporating very quickly, which will 
be gone when you have finished the sketch, and another 
much slower, which will remain as long as you require to 
finish it. 

Products derived from petroleum submitted to a special 
treatment, become absolutely colourless, and can be ren- 
dered almost inodorous, which gives them a great advantage 
over all other essences, whose penetrating odours are in- 
supportable even to professional artists. This advantage, 
and that of leaving no residue, are not the only advantages 
which petroleum has over essences. It is further superior 
by its power of penetrating through bodies, and especially 
through dry oil. A drop of petroleum on a canvas long 
after painting, goes through the painting without dissolving 
anything, and comes out at the other side there, where 
essence of turpentine would not even penetrate. It follows 
that resins, oil and transparent colours diluted with 
petroleum are carried by it much farther into the depths of 
the old coatings over which they are laid, than they could 
be by any other medium. 



8o SCIENCE OF PAINTING. 

To understand the importance of this quality of petroleum, 
it is necessary to know how one coat of paint operates 
on another. It is not like gum, where the new coat, 
distempering the preceding one, unites with it. Here the 
fresh oil has no action over the dry oil, and the adhesion 
is entirely mechanical. 

The oil of the new coat filters into the old by a multitude 
of little wells remaining open, which are like the pores of 
the skin, and these filterings hardening become solid fila- 
ments, remaining rooted in the old coat like the roots of 
a tree in the earth. Now, according to whether the oil- 
painting be more or less dry, its pores are more or less open ; 
a time arrives when they are sufficiently shut up for no new 
oil to be able to enter; but petroleum penetrates these 
perfectly, and if you have been careful to rub an old 
painting over with it before repainting the upper surface, the 
new oil dissolving in the petroleum will be carried by it to 
where it could not have filtered alone. 

If the colours contain wax, adhesion does not take place, 
as has been said above, and it is now easy to understand 
that in fact this wax, corking up the pores, does not allow 
the oil to cast its roots ; in this case, petroleum, instantly 
dissolving the wax, uncorks the pores, and adhesion can 
take place. For all those reasons you will do well to use 
petroleum. If, however, your fancy inclines to turpentine, 
only use it when rectified and renew it often, like the boy 
who remains faithful to his friend but who changes the 
friend every month. 

Siccatives. 

There is only one means known of rendering oil very 
siccative, /.^., to add to it oxides of manganese and lead ; not 
either, but both at the same time, and in equal proportions. 



SICCATIVES. 8 1 

Why so? 

We are about to have the boldness to try to explain. 

We have said that in order to pass from the liquid state 
to that of solidity, oil is required to make with oxygen a 
kind of combination. This oxygen the oil takes from the 
air, but it can absorb an appreciable quantity of it without 
combining with it, and consequently without drying. 

Oxide of manganese has the property of taking the oxygen 
where it finds it, and by the help of the oxygen transforming 
itself into double oxide. 

Oxide of lead has the property not of taking oxygen 
wherever it may be, but from those bodies which had 
already combined with it. 

As for oil, it only combines well with oxygSn when at 
transition point — i.e., when leaving one combination to enter 
into another. 

In fact, we have three thieves who constantly rob each 
other ; let us watch their operations when united. 

Oxide of manganese, taking oxygen where it finds it, 
takes even the oxygen brought by oil when not yet com- 
bined with the oil ; by this means it gets speedily rich and 
becomes bi-oxide, which is the millionaire of oxides. 
Then oxide of lead steals its' money, i.e., its oxygen, to 
appropriate it to itself. 

Oil appears afterwards as the third thief, and takes the 
oxygen to itself at the precise moment when it is passing 
from the manganese to the lead, for it is in those conditions 
that the oil combines best with oxygen. Here is an 
illustration. 

A man has in his meadow grass which contains azote, 
phosphorus, and other matters required for his nourishment, 
but which, in this form of grass, would be difficult for him 
to digest. He gives this grass to his cow, which eats it, and 



82 SCIENCE OF PAINTING. 

thus absorbs the azote, phosphorus, etc. Then the dairy- 
maid milks the cow, and the man, drinking the milk, re- 
finds the azote, phosphorus, etc., which under this new 
form are to him perfectly digestible, and he may then profit 
largely. 

If this explanation does not enable you fully to under- 
stand what happens when oil is brought into contact with a 
siccative on a basis of manganese and lead, it may at least 
give you some vague idea of it. 

The most common type of this kind of siccative is that 
called Courtrai siccative. Its manufacture is at the same 
time barbarous and mysterious. If you ask information on 
the subject from the colourmen, they are as dumb as if 
their back-shop were the seraglio of the Sultan ; or rather 
they will tell you that they have their siccative direct from 
Courtrai. Some one was simple enough to go and see. At 
Courtrai they did not even know what it was ! The truth is 
that the colourmen do not make the siccative themselves, 
and the majority of them do not know how it is made. They 
content themselves by insisting that it shall be very black 
(this is absurd but quite true), so that the manufacturer, 
who might with care make a better production, is quite at 
liberty to let all impurities pass, since it is never sufficiently 
dirty, and he is obliged to add lamp-black to it. 

Colourmen receive this siccative in large cans, and they 
content themselves with putting it into bottles, the smallest 
possible. Those who are more conscientious than the 
others (there are some) wait for some time until it clears, 
before performing this operation; but then there remains 
at the bottom of the can a large quantity of muddy deposit, 
and one must be very conscientious to consent to such a loss 
as that. 

This siccative should be made chemically pure ; it would 



SICCATIVES. 83 

then be much less coloured, and it might be introduced into 
colours in the form of paste. One would thus have the 
advantage of being able better to regulate the necessary 
quantity ; for too much is always used, and this should not 
be with colours that do not dry easily. If, however, you 
choose to continue the liquid form to which we are 
accustomed, it should first be made with petroleum instead 
of turpentine for reasons already stated, and it should not 
be kept within reach in a cup fixed to the palette, as is 
generally done, because every instant the paint brush is 
dipped into it, it is used as essence and in the end a 
ridiculous quantity is used. This is all the worse, because 
when used in more than a certain proportion it does not 
aid drying, and it is destructive to introduce oxides in too 
large proportion; for, when the oil is saturated with them, 
they continue their effects to the detriment of certain 
colours with which they remain mixed. 



CHAPTER VII. 
I^ES/NS AND VARNISHES. 

We cannot, for this study, follow the method which we 
have hitherto used ; for, if it be indubitable that ancient 
artists mixed resins with their oil-colours, it is impossible 
for us to know, for several reasons, what those resins were. 

1. Chemical analysis is still powerless in this respect. 
Resins not having been seriously studied by any one, their 
composition is not known; we know that they contain 
hydrogen, carbon and oxygen, but the formulas are not 
settled. The proportionate quantities of those three sub- 
stances vary, not only in each resin, but they change 
perpetually by contact with the air, whether in solution or 
in a dry state ; so much so that in analysing a resin taken 
from an old picture, we have the proportions of hydrogen, 
carbon and oxygen at which it has arrived in this musty 
condition, but it would be impossible to infer from this 
statement what the proportions in its primitive state were. 

2. The researches which can be made in old works treat- 
ing of painting only furnish very obscure information about 
the resins formerly used, whilst the names under which they 
are designated are, for the most part, unknown to-day, and 
those names which have traversed the centuries have always 
been applied indiscriminately to all kinds. 

The names of resins, even in our time, are not yet fixed ; 
what is called copal gum in France is called quick resin 



RESINS AND VARNISHES. 85 

in England, and vice versa -y this copal gum is alternately 
named gum of Calcutta, of Zanzibar, etc. — not according 
to the names of the places of its production, but merely 
those of the countries where stores for it have been es- 
tablished. Now, as the route of ships has been modified 
through steam, the boring of isthmuses and other circum- 
stances, the places of storage have been changed and the 
names have been altered. Besides, arbitrary classifications 
have been made. Thus several kinds of resin have been 
arranged into three categories : hard copals, semi-hard and 
soft copals, sometimes also known as male and female 
copals. Hard copals were the male, and soft copals the 
female. This classification permits the sale without fraud, 
under the general name of copal varnish^ of the commonest 
and least solid solutions of resins. 

To increase yet more the confusion, it happens that the 
custom-house has imposed a heavy tax on all resins imported, 
leaving gums scarcely taxed. Immediately commerce 
hastened to call gum all that had hitherto been called resin; 
and now there are only coarse resins, refuse from the manu- 
facture of essences manufactured in France, which have 
preserved their names. The result of all this is that when 
one finds anywhere a recipe for varnish, one never exactly 
knows of what resin the author is speaking. It is thus that 
we find continually processes detailed for dissolving the true 
hard copal, whether in an essence, in alcohol, or in any 
other solvent. Now, the true hard copal does not dissolve 
in anything! absolutely nothing! Or at least if any 
solvent exist, it is not yet discovered. It therefore follows, 
that not to treat as deceivers those practitioners who 
profess to have dissolved it, we must conclude that the resin 
which they have taken for hard copal was not the same as 
that which to-day bears this name. We have, therefore, 



86 SCIENCE OF PAINTING. 

nothing to gather from the examination of old pictures on 
this subject, and we are obliged to take the resins in the 
condition in which modern commerce presents them to us. 

We class them into four groups, not basing them either on 
their names or their places of production — all that may still 
be changed — but on their solutions, which do not change. 

Group I. — All the resins which dissolve entirely in cold 
alcohol, and not in essence, like gum lac. 

Group 2. — All those, which are dissolved in their own 
essential oil, and can be put over another essence, such as 
Canada balm^ balm of Copaiba^ turpentines of Scio, of 
Switzerland, of larch, of Bordeaux, American resin (elemi), 
etc. 

Group 3. — All those which dissolve equally well in 
alcohol and cold essences, such as mastic^ sandarac, etc. 

Group 4. — All those which do not dissolve in anything 
without the help of fire, such as Manilla^ Madagascar^ and 
copal gums, etc. 

What is to be done in order to, find, in all that, the 
elements of a varnish suitable to be used with colours ? 

Works of reference are only filled with empirical recipes 
eternally copied, twisted, and never actually tried by him 
who describes them ! If some author brings occasionally 
a novelty of his own, we find fantastic mixtures, as for 
example to have oil cooked with lime to use as a pomade 
for touching up. 

The scholar who gives this recipe to artists had already 
given them (he gave many) bitumen and greasy oil of sad 
memory : one might say leprosy and plague. 

He had been speaking of a journey to Italy, and he relates 
himself how he made this fine discovery. One day, he 
stopped in the street to contemplate a noble old man who, 
on the threshold of his door, was painting a picture yet 



RESINS AND VARNISHES. 87 

older than himself. This circumstance was not surprising 
in a town where every one is more or less of a broker and 
restorer of pictures ; but one peculiarity had forcibly struck 
the traveller. This old man was not alone ; he was accom- 
panied by a little pot ! Yes, a little earthenware pot in 
which was some strange substance. Into this little pot, the 
old man automatically dipped his paint brush at regular 
intervals; and each time that, after this immersion, the 
paint brush came back to the picture, the picture became 
darker and older ! — ^Oh ! the secret of the little pot or death, 
is it not ? (This was in 1830.) This secret the old man had 
from his grandfather, who had it from his, who had in- 
herited it from a friend one of whose ancestors had formerly 
bought it from a robber ! — who had stolen it from a cele- 
brated monk — in the neighbourhood of Florence. 

Fra Bartolommeo! — Hush, old man. — Be quiet. — Here 
is gold! — And the little benefactor bore the treasure over the 
hill, without explaining that this mixture of baked oil and 
lime was only a kind of black soap ! 

We cannot enter into details of all the recipes which have 
been published ; they may ultimately be reduced to this : — 

1. Use balms in their natural state : 

2. Dissolve one or more resins in alcohol and essences, 
and use them as varnish : 

3. Bake resin in oil to make oily varnish ; and add wax 
to it to make pomade. 

The use of balms is to be discouraged, because the 
essential oil which they contain, requiring a long time to 
evaporate, prevents the colours from drying regularly. It 
forms a crust on the surface, whilst inside parts remain soft ; 
and as essence of balm always evaporates at last, even if it 
should be through the pores of the dry soil, the lower 
coatings then shrink, and the surface is liable to crack. 



' 



88 SCIENCE OF PAINTING; 

Alcohol varnishes are not used in oil painting ; but there 
is one of them which is too frequently made use of on 
account of its being convenient ; viz. : — Sochn^ retouching 
varnish. It does not mix with colours, and it is only used 
to get out an embu^ and to repaint over the top. This 
varnish is absolutely pernicious, because it has a basis of 
gum lac and being altogether insoluble in oil the coatings 
of colour are thus separated into isolated flakes, making of 
the picture a mass of leaves without cohesion. Besides, this 
varnish is easily affected by damp, which makes it dull and 
bluish. Essence varnishes have all one great drawback : 
they do not evaporate completely, but leave a viscous and 
coloured residue besides the. resins with which those var- 
nishes are made, are either not soluble in oil, or form with 
it a mixture disagreeable to use and even decomposing in 
the presence of siccative, such as mastic for example. 

As for oily varnishes, only one is known — oil copal. It is 
the same as that used in the thirteenth century by a 
learned monk to preserve the paintings in his convent. 

He prepared it himself during the calm of the night, on 
account of the dangers of the operation; and when the 
peasants returning from the fields passed near the old 
chapel where he had installed his laboratory, they crossed 
themselves when they saw the pestilent vapours, all red 
with reflection from the brazier, escaping from the windows. 
Since then nothing new has been discovered, except that it 
is no longer in old chapels, but outside the barriers of towns, 
that this dangerous and disgusting manufacture is carried on. 

It has remained absolutely at the same point. Some 
makers, not even yet knowing that mercury thermometers 

* Embu is equivalent *to the English word sinking. It means a part 
of the picture where the painting is dull owing to the foundation having 
absorbed in the oil. 



RESINS AND VARNISHES. 89 

exist registering to 400 degrees, have no other means of 
ascertaining the temperature of oil than by frying in it a 
clove of garlic and a crust of bread. 

Let us therefore take this production such as it is and 
see what we can learn from it in the cause of painting. 
From all the resins which do not dissolve in oil without 
the help of fire we shall choose the most beautiful and the 
hardest, true copal, leaving all the others as only fit for 
varnishing carriages. 

To recognise resins at first sight it is not enough to have 
read the description of them : one must be in the habit of 
manipulating them. If young artists had at their disposal 
specimens of all the resins and also of all materials used in 
painting, they might, without much trouble, familiarise 
themselves with all the products of nature or science the 
very names of which are unknown to them at present : and 
this would be of great use to them later. It seems that at 
the School of Fine Arts a collection of this kind ought to 
have its place in a laboratory, where a practical chemist 
might show to the pupils the different elementary prepara- 
tions which constitute art materials ! Let us hope ! True 
copal dissolves at 370 degrees of heat. Subjected to this 
temperature, it sends forth vapours which condense into an 
empyreumatic oil, as do all resins soluble Under the action 
of fire. 

When copal has thus lost in vapour 10 per cent, of its 
weight it can be dissolved in the essence of aspic : this is 
what it called copal essence forming the basis of Haarlem 
siccative (but do not go there to seek it). In this condition, 
copal neither dissolves in oil, turpentine, nor petroleum, and 
it yields a bad result if mixed with colours. 

It appears to cause them to dry because as soon as the 

essence of aspic evaporates, not remaining dissolved in the 
v.p. 6 



90 SCIENCE OF PAINTING. 

oil, the copal dries by itself; but it also bringis into the 
painting a foreign matter which does not incorporate with 
it. (We shall speak of its effects later.) In all cases, those 
preparations are only false siccatives which in no way dry the 
oil, since oil only solidifies when mixed with oxygen. When, 
continuing the operation of dissolving copal by heat, the 
copal has lost 25 per cent, of its weight, it can be dissolved * 
in oil and essences, even cold. This is the production 
known as copal oil. It can then be painted over essence 
or petroleum, and it is no longer destructive to the painting 
except that it is very yellow and becomes even more so 
with time. It dries badly and leaves a dull surface. 

In reality, this resin, dissolved in oil, is no longer hard 
copal : if we separate it from the oil, it is dry, yellow and 
friable between the fingers like colophony. 

It is, therefore, not worth while to take the rarest and 
most solid resin, since it can only be utilised by making it 
like the commonest and most fragile. 

Before the experiments which have permitted us t6 know 
this were made, copal was put into oil over the fire, and, seeing 
it melt there, it was imagined that it was thereby incor- 
porated with all its qualities. To-day we are forced to 
acknowledge that the same disintegration takes place in 
warm oil. As soon as the oil attains the temperature of 
370 degrees, the same vapours escape, and it is only when 
\he copal has lost 25 per cent, of its weight that it begins to 
dissolve. Only it is almost impossible to prevent the oil 
from rising to a higher temperature, and then the copal 
burning becomes partly charcoal, which, with its empy- 
reumatic oil, makes actual tar. It is the same with all the 
resins of the fourth group requiring the help of fire. They 
themselves are not dissolved; it is only the product of 
their dissociation that is dissolved. Amber, succinum, or 



RESINS AND VARNISHES. QI 

yellow amber about which so much has been said lately, 
acts like copal. Yet persons, whose veracity may not be 
doubted, have' affirmed that they have found the means of 
dissolving amber or copal without the help of fire. There 
is only one remark to be made about this ; it is that copal 
may be dissociated by some chemical means other than 
heat, thereby obtaining the same result. 

What we should like to see would be a varnish made with 
copal, which, once dry, should be as brilliant, as transparent, 
and as hard as copal itself. That has not yet been seen ! 

As far as we have arrived, the result is that no resin 
known is suitable to be used in painting. 

Must we, then, wait until others are discovered ? No t 
One must be made, or rather one must be purified. After 
many trials and much patient study, we can affirm that 
nearly all resins, as they are collected, are in a partial state 
of disorganisation; or, if you prefer it, just about to be 
organised, which is almost the same thing. All their parts 
are not soluble in the same solvents, are not coloured alike, 
do not melt at the same degree of temperature, and do not 
contain the same proportions of hydrogen, carbon, and 
oxygen. 

One single resin we have been able thus to separate into 
twenty-three different parts. Those parts are in varied 
proportions not only in each resin, but even in the same 
resin the proportions are perceptibly variable from month 
to month. Would they continue to vary indefinitely, or 
does there exist a definite condition towards which all those 
parts are travelling and at which they will stop ? We do not 
know. We have never found any arrived at this condition. 
On the contrary, we have remarked in several a more or 
less considerable part no further divisible, uncoloured, hard, 
crystallisable, perfectly transparent, soluble in cold oil and 



92 SCIENCE OF PAINTING. 

petroleum, and which would be, were such a definition 
admissible, the normal resin, having as yet undergone no 
transformation. This is the normal resin that you ought- to 
seek, if you want a substance invariably the same, what- 
ever may be the climate of the country, the nature of the 
soil where the tree grows which produces it, the manner in 
which it is gathered, and the changes to which it has been 
subjected ; for all those conditions which one cannot know 
influence the composition of the resins, which consequently, 
although of the same kind, are never absolutely alike. With 
the normal resin we shall compose, by the help of petroleum 
at diflferent degrees of evaporation, the three kinds of 
varnish which are necessary to facilitate the process of oil- 
painting : 

1. Varnish for re-touching ; 

2. Varnish for painting (or oil varnish) ; 

3. Picture varnish (or final varnish). 

Varnish for Re-touching. 

. Dull patches or sinkings, of which we shall speak later with 
regard to the painting of a picture, should hot trouble the 
artist, since, with a light scumbling of re-touching varnish he 
can remove them whenever they appear. 

As this varnish dries in a few minutes, it can be im- 
mediately painted over ; and as it forms a solid link between 
the different coats of paint, it is even very necessary never 
to repaint any piece without first painting it over with this 
varnish as a preliminary. 

It can be mixed with colours to make rapid glazings, but 
it is too volatile to be used for solid painting.* 

For this purpose painting varnish should be used. 

* If, however, in certain cases, this quick drying is no inconvenience, 
there is no other objection to painting with re-touching varnish. 



PAINTING VARNISH. 93 



Painting Varnish. 



This varnish, which should be kept in the trough of the 
palette, is used for painting by mixing it, by means of 
the paint brush, with . colours whose fluidity, brilliancy, 
and solidity it increases. It is of excellent service for 
glazing, and, not being too siccative, it allows a long time 
for shading in the fresh paste. It replaces re-touching 
varnish in all cases where it is desired to paint on wet instead 
of dry canvas ; and mixed with re-touching varnish in all 
proportions it can be used for all requirements. All these 
varnishes are composed of purified petroleum, more or less 
volatile, leaving no residue after their evaporation, and 
composed of solid matter perfectly soluble in cold oil. So 

• 

that, whether they are painted over, or directly mixed with 
the colours, those substances are always penetrated by the 
oil, dissolve easily in it, and, completely incorporating with it, 
they give to it much more resistance, without withdrawing 
from it its suppleness and without hindering, its work of nar- 
rowing. Further, those varnishes render the drying of the 
painting quicker and more equal by a phenomenon which a 
short explanation will make clear. As we have already said, 
oil must be oxygenised in order to dry. Left to itself, it 
borrows oxygen from the air. If siccative be added to it, 
the siccative collects the oxygen and transmits it to the oil, 
which is a quicker process ; but in any case, contact with 
the air is always indispensable. 

When the first film forms on the surface, this contact 
having no further hold than through the pores of the dry oil, 
the drying of the deep coatings is naturally kept back until 
this film thickens. Now, amongst the materials which these 
varnishes contain, is to be found a rather large quantity of 
oxygen in a chemical condition which renders it very easily 



i. . ^ 



94 SCIENCE OF PAINTING. 

assimilable with oil : the latter can, therefore, oxygenising 
without the help of air, dry much quicker, and in an equal 
degree at all depths. 

It is again useful to explain that all re-touching varnishes, 
and all glutens, pomades or siccatives that have been until 
now introduced into oil-painting, besides their characteristic 
of becoming yellow aiid black, have the serious fault of 
being largely composed of substances insoluble in cold oil, 
so that the successive coats of paint are separated by 
isolatir^ pieces, and the oil with which these colours are 
ground is divided by foreign substances, unequally dis- 
tributed, which solidify quicker than the oil and become 
harder and more brittle. 

It follows that the oil, which contracts whilst drying, can 
no longer do its work regularly, in the midst of all these 
obstacles ; it then happens that successive solutions cause 
the outlines of cracks that go on always increasing as the 
work of the oil proceeds. And this process of oil-shrinking 
continues for years ! 

These accidents are not prevented by the final varnish, as 
their causes lie below. Often the accidents are rendered 
worse by the final varnish, for it brings a new resistance, if 
it is not perfectly supple, and it cracks in its turn when too 
dry. The greatest care should therefore be exercised in the 
choice of picture varnish. 

Picture Varnish. 

The final varnish which is painted oyer the finished 
picture has for its object, whilst giving brilliancy and trans- 
parency to the colours, to preserve the picture from direct 
contact with the impurities liable to be deposited on its 
surface, as well as from the gases in the atmosphere ; and 



PICTURE VARNISH. 95 

that, without trammelling the incessant work of shrinking 
and dilatation of the oil, the wood and the canvas. 

In order, therefore, that this object may be attained, the 
varnish must remain uncoloured and transparent, at once 
resisting and supple ; it must be possible to wash it when 
dirty, and should it be desirable to take it off, it must be 
possible to do so without spoiling the picture. 

Now, all varnishes hitherto employed become more or less 
yellow as they get old. They get blue with dampness, sticky 
with heat, crack, and in time always finish by getting white 
and opaque. They cannot be washed when dirty without 
spoiling them, as they do not withstand damp. They have 
to be renewed, and can only be removed by rubbing them 
with the finger, or by damping them with alcohol and essence 
of turpentine. All those processes, however careful one may 
be, always attack the painting a little, — so much so that after 
several removals of varnish the picture is half destroyed. 
Many amateurs know this danger, and they often prefer to 
keep their smoky pictures, almost invisible under deteriorated 
varnishes, rather than risk experiments. 

The varnish which we propose joins to all the requisite 
qualities the great advantage of being easily cleaned as 
often as may be desired, without changing in any way, 
which enables the pictures to be kept in a constant state of 
cleanliness, absolutely necessary for their good preservation. 
The petroleum with which this varnish is made, evaporating 
less rapidly than the essence, renders the varnishing much 
easier, by enabling the operator to apply the coating more 
leisurely, without the drying being thereby retarded : quite 
otherwise, for this varnish is completely dry at the end of 
about an hour. Further, as it does not contain any viscous 
matter, there is no stickiness to attract the dust in the air. 

For directions for varnishing see Appendix — "Varnishing. ' 



CHAPTER VIII. 

CANVAS, PANELS, AND THEIR PASTES^-^SIZINGS. 

Having chosen with the greatest care the materials re- 
quired for painting, we have still to know on what we are 
going to paint ; the question of canvas, panels, etc., is one 
of great importance. 

A picture is composed of three altogether distinct ele- 
ments : — 

' I The support, or the material substance painted on, as 
wood, canvas, stone, paper, etc. 

2. The coating or sizing used to cover the material support. 

3. The final painting, formed by successive layers of 
colour applied over the sizing. 

If the painting be done under bad conditions, and con- 
tain in itself the germs of its destruction (spoken of above), 
the picture is irretrievably lost, and that in spite of the good 
quality of the support, and of the sizing. 

But, admitting the hypothesis that the painting is as per- 
fect as it ought to be, it is also necessary that the two other 
constituent parts of the picture {Le, the support and the 
sizing) should be perfect. 

The support will first be chosen as substantial as possible, 
but it can still be preserved from many causes of destruction 
by covering it behind and on the sides by means of mastic 
and suitable protective varnish. {See Appendix — " Panels 
of Unpolished Wood.") 



CANVAS, PANELS, AND THEIR PASTES. — SIZINGS. 97 

If, however, it happens to spoil even when all precaution 
has been used, a clever picture restorer can still save the 
painting by transferring it to another canvas or panel, always 
provided that the sizing sustaining it remains in good 
condition. 

A proof of this preservation of painting on destroyed 
supports is to be found in an examination of the old triquet- 
rous altar screens, whose three panels of the same wood, 
painted by the same artist over similar sizings, are in the 
best conditions to be usefully compared. Nearly always 
the middle panel, remaining attached to the wall, is rotten, 
owing to damp, while the two side leaves, being surrounded 
by air, are yet perfectly sound. In those conditions, when 
the sizings are good, the painting is equally preserved on 
the middle panel and on the side leaves, whilst on the con- 
trary on bad sizings, the painting is spoilt on the rotten 
panel and preserved on the leaves in good condition. 

In fact, therefore, the preservation of the painting depends 
on the quality of the sizing. It is not enough that the sizing 
should be solid: were it like steel, indestructible as the 
diamond, we should still require to have it less brittle ; for 
should it scale off, melt or powder, it would involve the 
painting with it. It must even be sufficiently supple to lend 
itself to the peculiarities of the painting, as it contrapts 
when drying, and yet it must be of sufficient resistance to 
preserve the painting from too sudden movements of the 
support. It should absorb the excess of oil and varnish 
which comes to it from the painting, and it should reject all 
which might penetrate through the support. In short, com- 
pelled to obey the slightest caprices of the one and to resist 
all the attacks of the other, it is required from it, as from all 
servants, to be equal to the occasion. 

Notwithstanding the. importance of the rdle which the 



98 SCIENCE OF PAINTING, 

sizing plays, and * perhaps rather on account of this import- 
ance, it is often suppressed — first, for painting on paper in 
water-colours and pastel where it is not necessary, and 
sometimes even for oil painting when done directly on the 
support. 

In this case supports should be chosen having something 
of the qualities the sizing would have had — ue,^ dilating little 
and shrinking little, of a fine texture, uniformly porous, and 
containing neither acids, resin, nor any other matter capable 
of influencing the colour ; if found too absorbent it will be 
well before painting to brush the support over with a little 
re-touching varnish, or painting varnish, or a mixture of 
both, according to whether the painting is to be in a dry 
style, or the colour is to glide smoothly over the surface. 
{See Chapter IX.—" Oil Sketching.") 

The ancients painted on wood, on tanned skins, on lava, 
on marble, on slate, on metals, on walls covered with lime 
mortar, and on stone itself, after having saturated it with a 
sizing of resin made to penetrate by the heat of a chafing- 
dish. 

Their portable panels were very thick and very solid. It 
is related that at the siege of Rhodes the soldiers made use 
of pictures by Apelles for a table. In the middle ages the 
same substances were used to paint on, but especially wood, 
chiefly oak and poplar. 

The joins of the boards which formed the panel, and its 
coating, were made of animal glue (TaurocoU), or of flour- 
paste mixed with plaster or chalk, or even with a paste made 
of cheese and lime, the recipe for which Theophilus gives 
in a celebrated manuscript. This last paste is by far the 
most solid. It has been proved that on old panels altogether 
rotten the coating remained intact, and that even at the 
place where the joins were solidified by bands of canvas 



CANVAS, PANELS, AND THEIR PASTES. — SIZINGS. 99 

prepared with this paste, the wood which it covered had 
been preserved* 

Sometimes, for valuable pictures, they gummed all Dver 
the surface of the panel a leather coated with resin or covered 
over with plates of gold. But as they could not make those 
plates as thin as they are now made, they were valuable 
enough to tempt the cupidity of the iconoclasts, and nearly 
all the pictures painted on those foundations considered 
indestructible were just the ones that were first destroyed. 

The exclusive use of wood panels was preserved in Italy 
till the time of Raphael, and in the Low Countries much 
later, till the time of Rubens. 

At that time so strong was the conviction that panels for 
painting should be scrupulously chosen, that government 
had monopolised their manufacture. 

Only perfectly dry and faultless wood was used, the 
workmanship was of the best, and it was forbidden, under 
penalty of fine, to paint on other panels than those of the 
government, for the following reasons : ** that the genius of 
an artist is the patrimony of his country ; that it is the duty 
of the country to guarantee the longest possible duration to 
its masterpieces, and that, to make this sure, equal pre- 
cautions should be taken with regard to all pictures ; as a 
painter, however celebrated he may become, always begins 
by being unknown, he may by chance be modest, and con- 
sequently ignorant of the ultimate value of the work which 
he undertakes, and therefore the possibility of his compro- 
mising the work by negligence or economy should not be 
permitted." 

This law, which to-day would make many people smile, 
was rigorously enforced during the zenith of the Dutch 
school, and it is perhaps to it that we owe the preservation 
of many of the finest gems in European museums. 



lOO SCIENCE OF PAINTING. 

When canvas became more general, the sizings which had 
been used for wood panels were continued, and it is on 
the same concoctions of paste and •chalk that the first canvas 
pictures were painted. These concoctions were afterwards 
abandoned by degrees — />., the sizings of paste, getting 
thinner and thinner, were re-covered by others made of oil 
and white lead, and finally no paste was used at all. But it 
was soon observed that canvas, in direct contact with oil, 
burned and became like touchwood. This sad fact estab- 
lished, artists returned to the use of a first coating of paste, 
merely to separate the canvas from the oil coating ; but this 
first coating was of a gelatinous substance susceptible to 
damp, and the canvas became rotten. 

Another method was then tried — viz., putting behind the 
canvas another coating of separating paste re-covered with a 
second coating of oil and passing them between two cylinders 
to press them. But, thus imprisoned, the canvas lost all 
suppleness, and could no longer be stretched on the frames ; 
then they stretched the canvas first, and the coatings put on 
the stretched canvas were merely numerous coatings of oil- 
white, and by therewith entirely covering the grain of the 
texture, manufacturers tried to get a surface as smooth, as 
that of a panel. 

This method had the inconvenience of encumbering the 
studios with frames, each canvas requiring two or three 
years of constant exposure to the air for its preparation ; 
trying to shorten this time, siccative means were used — such 
as replacing a portion of the oil with essence of turpentine, 
using oil prepared with litharge, umber, or red earth mixed 
with white and sometimes even using no oil at all. 

These practices were not calculated to improve the 
qualities of a coating already doomed to scale off fatally — 
quite the contrary ; but they facilitated the manufacture of a 



CANVAS, PANELS, AND THEIR PASTES. — ^SIZINGS. lOI 

kind of canvas which assured to artists a rapid and valuable 
execution in great favour for a long time especially amongst 
portrait painters whose supreme ambition was to imitate 
porcelain. 

Did they suspect that they would imitate even its cracks ? 
In any case, time has amply revenged the fiimsiness of those 
guilty pretensions : to-day a portrait of an ancestor that is 
cracked loses much of its value ! 

After this period of brittle canvas, the ordinary laws of 
reaction brought on a taste for supple canvas, and much 
ingenuity was exercised in procuring this quality. A sizing, 
was added of mucilage paste, such as linseed, snail-slime, 
honey, fig-juice, etc. An oil was also used, rendered ' 
viscous by rancidity — ue,y acidified and never drying. For 
reasons of economy, manufacturers substituted for white 
lead, chalky whites of Troyes) whiting, white of Meudon, 
white of Bougival, pipeclay, etc., which gave them results 
just as good in the matter of suppleness, none of the car- 
bonates of lime ever drying thoroughly when they are 
ground with oil. 

Every one knows that glazier's putty, which is made of oil 
and whiting, will remain soft for many years under a hard 
and wrinkled coating. 

It is easy to understand, therefore, that painting must 
crack when done over coatings that continue to shrink long 
after the painting is dry. The invention of railroads, which 
has changed so many things, is also not without influence on 
painting-canvas, for like all other things pictures also now 
travel, and the constant rolling and unrolling jiecessi- 
tates the use of more and more supple canvas, until 
suppleness is now the chief property considered in its 
manufacture. 

This is the present state of the manufacture. 






I02 SCIENCE OF PAINTING. 

By an inexplicable anomaly, unbleached canvas costs 
more at the French custom-house than prepared canvas 
does. Now, painting-canvas being made chiefly in Holland, 
and hand labour costing less there than at Paris, it has 
become the custom to apply the coating at the place of 
manufacture and to send the canvas ready prepared in 
large rolls : this has the double advantage of costing less and 
of not encumbering the shops. Further, the canvas being 
rolled as quickly as possible, the oil deprived of the light 
before becoming dry, gets rancid and diminishes the supple- 
ness of the coating, as has been said above. 

This canvas is therefore perfect ? For the tradesmen, yes ! 
But it is yellow, it has a disagreeable odour, and pictures 
painted on it remain to posterity blackened and cracked. 
Of course manufacturers do not work for posterity. 

By comparing the works which remain to us and by 
examining the materials on which they are painted, it is 
easy to convince ourselves that the best preserved pictures 
have been painted on paste sizings. 

Is that to say that all those which are on paste sizings are 
well preserved ? Assuredly, no. But that does not affect 
the principle, because, very often, the cause of destruction 
is independent of the sizing, and" sometimes the paste used 
was of bad quality. 

Paste should be incorruptible, supple, perfectly neutral, 
and not susceptible to damp. In this condition it isolates 
the colours from all chemical reaction liable to result 
from the support ; neither contracting nor expanding, it 
occasions no cracks, and its suppleness enables it to follow 
the movements of wood and canvas ; whilst oil sizings, on 
the contrary, oxidise, get yellow, produce chemical reaction 
on certain colours, shrink, and in the end invariably become 
brittle. 



PASTES. 103 

. The conclusion of all this is, therefore, that oil sizings 
should be rejected and paste used. But it must be carefully 
chosen. 

Pastes. 

How should we proceed to study pastes ? 

As in all other studies, by consulting books treating of 
the subject. 

Yes! but clever practitioners, well informed, have not 
left books, and one gets mystified with a deluge of manuals 
and collections scarcely intelligible. The recipes therein 
found are often impracticable. They are frequently dis- 
torted by successive errors of print, and in that condition 
they are carefully collected, reprinted and perhaps translated 
into several languages by one of the sham philosophers who 
write about everything, satisfied with re-copying what has 
been done before their day, without understanding it and 
without ever making personal experiments themselves. 

It is thus that the greatest errors and follies have come 
to us through all ages, from book to book, as if they were 
gospel truths. 

If, however, you still desire to consult all those old 
authorities, here is a kind of key to facilitate their study. 

When you hear of oyster shells, crabs' eyes, stags' horjis, 
mother-of-pearl, pearls, you will know that by them is 
meant carbonate of lime, of which the type is chalk. When 
you hear of the blood of a pig or of any other victim, of 
milk, of fresh cheese, of crust of Gruyfere, of yolk of egg and 
of powdered insects, the principle of all that is caseine, 
fibrine or vitelline, which are almost the same thing. 

White of egg is albumen ; if you hear of fishes' bladders, 
cows' tails, old gloves, boot-tags, skins of rabbits, still-born 
kids, or sheep's feet, all that is gelatine. 



104 SCIENCE OF PAINTING. 

All the ferinaceous feculents, wheat, barley, sago, tapioca, 
rice, potato, etc., furnish starch and gluten. Many trees 
and exotic plants having Latin names, not the same in all 
books, yield gums and resins ; and if in some recipes you 
read that a candle should be burned over the boiler, it is 
only the wax which falls from it that can be useful. 

As for quicklime, the urine of camels and dung, they 
act like alkali, and can be replaced in almost all cases by 
volatile alkali (ammonia).. 

. You will also hear of other unimportant ingredients, which 
must not be considered as of consequence. Amongst 
them are figtree sap, syrup of snails, linseed, honey> all 
used as mucilage to give suppleness, and not one of which 
is equal to glycerine for this purpose. 

AH the pastes imagined and described up till now (there 
are some thousands of them) are really made with only eight 
substances, four of which are animal and four vegetable. 



Animal, 


Vegetable. 


Gelatine 


Starch 


Albumen 


Gluten 


Caseine [px fibrine, or vitelline) 


Gums 


Wax 


Resins 



Glycerine as mucilage, and ammonia as alkali, yield an 
assistance often indispensable. 

. By taking, therefore, those substances chemically pure, it 
is possible by mixing them to reproduce all the most com- 
plicated ancient pastes. For this purpose it is enough to 
consider those of the substances which contain the materials 
composing the paste that we wish to reproduce. For 
instance, here, in an old manuscript, is the simple recipe of 
a paste used by the Benedictines to prepare the parch- 
ment of missals on which they painted miniatures : " Gather 
bees during the summer months after vespers ; pound them 



PASTES. 105 

in a mortar with lime-water, and afterwards filter the mixture 
through linen." 

By analysing this strange mixture, we find that bees contain, 
like all other animals, a little gelatine and fibrine, and bees 
further contain wax and honey. 

The presence of lime transformed the fibrine into paste, 
and rendered the wax miscible with water ; filtering separated 
the useless particles, the legs, wings and other impurities. 
As for the advice to choose the summer months and the 
evening hours, it is doubtless at that time of the year that 
bees make most wax and honey, and in the evening that 
they have most of it. 

Let us now consider the subject synthetically. Instead of 
fibrine we shall take lascine, which is analogous ; instead of 
honey, glycerine ; instead of lime, ammonia ; we shall add 
gelatine, wax and water, and, without even requiring to 
filter it, we shall have made the Benedictine paste, 
excellent for the purpose for which they used it. It is 
not at all susceptible to damp, incorruptible, supple, and 
perfectly good to preserve the leaves of a book destined 
to be often handled. 

And that is how science, which sometimes immolates so 
many victims, can to-day save the bees from the terrible 
pestle and mortar of the monks^ and leave them to buzz in 
peace amid the flowers of the meadows ! 

With the eight substances mentioned, we are not limited 
to re-making ancient pastes : we can compose new ones. 

Only, when we consider that each of these substances can 

be separately treated in different ways, and that certain of 

them, such as gum and resin, offer different and numerous 

types whose qualities should be separately studied, when we 

consider the number of combinations that can be produced 

with eight figures, that in each of these combinations the 
v.p. J 



Io6 SCIENCE OF PAINTING. 

proportion may be changed many times, and that it is after- 
wards necessary to try all these pastes, first on supports of 
all sorts, to see how they are affected by wood, canvas, card- 
board, paper, etc. ; and that afterwards paintings in all styles 
should be subjected to dampness, dryness, sunshine, darkness, 
and that it is prudent to wait several years to judge fairly 
the results of these trials, it can be understood that it is only 
toward the end of his career that an honest experimentist 
can allow himself to say that he thinks he has finished. 

Let us now see how each of these eight substances can 
be transformed into paste or can be assimilated with it. 

Gelatine^ dissolved in water, gives the paste generally 
known as animal gluten and glue. Strength may be given 
to those gelatinous pastes by the addition of quicklime, oily 
varnish, or gum lac ; or they can be preserved liquid whilst 
cold by acetic acid or other means ; glycerine, chloride of 
calcium and indiarubber will give suppleness ; and they can 
ultimately be rendered insoluble by chromic acid, acetate 
of aluminum, and bichromate of potash. {See Appendix — 
" Gelatine.") 

Albumen is obtained by beating up the whites of eggs 
in snow, and at the end of an hour collecting the liquid 
which flows from it. It may also be bought in a dry state. 

This paste can also be made supple with glycerine, and 
becomes insoluble when it is heated to loo degrees in a 
damp state. 

Caseine may be bought in a dry state from chemical dealers, 
or it may be extracted from cheese. It becomes supple with 
glycerine. {See Appendix — " Caseine or Cheese Paste.") 

Wax is a natural production. It should be chosen free 
from the suet with which dealers mix it. It is rendered misci- 
ble with water by volatile alkali (ammonia). {See Appendix 
— " To render Wax miscible with Water and Glycerine.") 



PASTES. 



107 



Starch and Gluten furnish paste, dextrine, etc. {See 
Appendix—" Starch or Farinaceous Paste.") 

Gum dissolves simply in water. — By adding boric acid to 
gum water it will keep a long time without corrupting. It 
becomes supple with glycerine. 

Resins dissolved in oil (oil varnish) or in essences mix 
with paste in the state of emulsions, or directly by means of 
alkali — ^as gum lac, for instance, which, dissolved in borax 
or ammonia, can be thus introduced into sizings. (See 
Appendix — " Gum Lac") 

With the above any one can make for himself combinations 
suitable for all purposes ; but we are here limited to the 
search of better sizings for surfaces destined for oil paintings. 

The great fault of those who make researches on a subject 
and write about it is that they wish to make their readers 
feel all the extent of their work, and they begin, before giving 
the result at which they have arrived, by relating all the 
unsuccessful attempts that they have made — like conjurors 
who fail in their tricks several times to excite the public all 
the more when they succeed. 

Dismissing this pretentious practice, we shall say at once 
that the best of all sizings that can be used to prepare canvas, 
panels or cardboard destined to receive oil painting, is cheese 
paste (or caseine paste) ; but there is a way of making it 
which should be followed to the letter, if good results are 
wished. (See Appendix — :" Sizing of Caseine or Cheese.") 

When the sizing has been executed on the canvas in good 
condition, the next thing to think of is the wrong side of the 
canvas, which also requires a sizing impervious to water 
and oil, so that the excess of oil coming from the colours 
shall not go through the tissue, as that might burn it, and so 
that dampness shall not be able to penetrate it, as that might 
cause it to rot. 






0-- 



% 



I 



io8 



SCIENCE OF PAINTING. 



4 



■J 



This sizing must also be supple, so that the canvas may 
roll up easily. Many substances may fulfil those require- 
ments — ^indiarubber dissolved in petroleum, wax and resin,, 
gum lac. But what is yet better, especially for canvas of 
small dimensions, undesirable to thicken too much, is to put 
/ two coatings of water-colour fixative. 

It has been advised through excessive precaution to put 
also a fireproof coating of somC'kind as a preservative against 
fire ; but this cannot be put on the front of the picture and 
would be consequently of little use in case of fire. A better 
plan would be to nail a metallic canvas on a light frame, 
attached by hinges behind the picture (so as to be easily 
opened at will). This metallic canvas, being thus held about 
half an inch off from the painting canvas, would allow the 
air to circulate and would preserve the picture from shocks, 
such as contact with flame, of which there is much more 
danger from behind than in front ; for it is noticeable that in 
museums, at picture dealers' and in the houses of amateurs, 
servants who have the greatest respect for pictures when 
hung pay no attention to them when standing with their 
faces to the wall : they drag ladders about, and move round 
with lighted candles through piles of heaped up frames, 
without taking the smallest precaution, although, on the 
contrary, they ought to take the greatest care. 

We might still, besides the sizings properly so called, 
whose liquid basis is water, find in the substances which 
chemistry has already discovered, and will discover, the 
elements of a sizing more perfect than cheese paste ; but we 
are unable to find one that offers the substantial guarantee 
which this does of having been used for centuries, and of 
having resisted all causes of destruction. 

If, however, you have enough of confidence in the 
science of an old practitioner who has consecrated his life 



PASTES. 109 

to the study of painting, and if you wish to try something 
new, here is a sizing which he proposes, and which he con- 
siders absolutely perfect : — 

Grind zinc-white with alcohol and mix it with water- 
colour fixative. 

Lay on one coating ; and when it is dry, which will be in a 
few minutes, rub with glass paper. As a matter of course, 
the more zinc-white you add, the more absorbent the sizing 
will be, but it will be less solid in proportion. {See Appen- 
dix — " Instantaneous Sizing.'*) 

Over all these sizings we can paint equally well in oil or 
water colours. Only one question regarding the sizing 
remains to be considered : and that is, what tone we should 
prefer to give it. We do not hesitate to answer that the 
sizing should be perfectly whit^, and that for several reasons. 
First, to obtain effects of transparency without the necessity 
of painting in oil-whites and afterwards glazing, which 
involves waiting a long time until the under coatings are 
dry, and sends us back into all the inconveniences of oil 
sizing. Secondly, because the under coatings always work 
up a little, and a picture, painted over a coating of any tone 
whatever, will ultimately always become itself of that tone, 
especially in those parts least covered. Certain pictures of 
Poussin and of the French school of the eighteenth century, 
painted over red coatings, are striking examples of this. 
Some artists have preferred umber, and even pure black, 
but their works have not lasted a century. Their pictures 
have become quite invisible, in half tints, at the end of a 
very short time. 

Apart from the preservation of the picture, there is another 
important consideration — viz., white foundations naturally 
cause greater luminosity and that is a valuable quality; 
darkness always comes on soon enough. 



CHAPTER IX. 

OUTLINE AND EXECUTION OF A PICTURE IN OILS 

SINKINGS. 

We have substantial colours, well ground; petroleum 
volatile in. diflferent degrees, siccative, liquid or in paste ; 
re-touching varnish, painting varnish and canvas or panels 
covered with excellent size, in short, for painting under 
favourable circumstances, we have everything in good 
condition. 

We shall not trouble about the tools, brushes^ paint 
brushes, knives, pans, etc. ; each artist can make his own 
choice ; they do not affect the solidity of the painting. We 
shall only mention the palette. We advise it to be white, 
and quite impervious to oil, because that allows a correct 
judgment of the transparency of the colours, and also tends 
to keep things light, and the sizing of the canvas or panels 
being also white, tones will have the same effect on it as on 
the palette. The latter being impenetrable, preserves to the 
colours exactly the quantity of oil or varnish judged well to 
add to them, and a white palette is easy to clean. The 
utmost cleanliness in palette and all other requisites is quite 
indispensable. 

The Outline. 

Whether we paint on a panel, or on canvas sized with 
cheese paste, or on a panel of unpolished wood, or on 
water-colour paper, the outline may be done either in oil 



THE OUTLINE. Ill 

or water colours. If in water colours, it is best to use 
ordinary water colours, not paste — being careful, if on un- 
polished wood, not to put on too much wash, so as to have 
no misadventure with the wood. 

1. If the sketch is to be done in water colours on canvas, 
or panel sized with caseine paste, one very even coat of 
painting varnish should be laid over it : this varnish' will 
partly soak in with the sizing, and, even before it is dry, the 
oil painting may be continued. This is the process of Paul 
Veronese. 

2. If the sketch is to be done in water colours on water- 
colour paper, one very even coating of water-colour fixative 
should be laid over the paper: this fixative will soak 
completely into the paper, and will be dry in a few minutes. 
It is possible that this coating may not be sufficient, because 
some papers absorb more and some less fixative. The fact 
may be? ascertained by putting a drop of oil on one of the 
corners : if this oil does not penetrate into the paper, there 
is enough of fixative ; if not enough, then put on a second 
coating. . 

In any case those operations cannot take more than from 
fifteen to thirty minutes, after which the oil painting may be 
immediately continued. This method allows us to do in 
water colours the part that they are capable of doing well — 
viz., the sky, water, etc. — in fact, all the transparencies. The 
solid parts which require much shading may be done in 
oils. 

The whole once varnished is of perfect solidity and of great 
beauty of execution. 

For this process, paper of fine grain should be chosen, 
coarse grains always having a bad effect when varnished. 

3. When the outline is done in water colours on un- 
polished wood, it is well to give one good even coating of 



112 SCIENCE OF PAINTING. 

water-colour fixative, and the oil painting can be continued 
as soon as the fixative is dry, which will be in a few minutes. 

Outlines in Oil. 

If required to outline directly in oil : 

1. On canvas or panel sized with caseine paste, paint 
over the sizing one very even coat of painting varnish which 
will partly soak in, without which this sizing would be too 
absorbent. If, however, it is desired to make use of this 
quality, a rather large quantity of painting varnish should be 
mixed with the colours to make the work less tedious. 

2. On water-colour paper, before beginning the oil 
painting, one or two coats of water-colour fixing should be 
applied, according to whether it is desired to have the 
paper absorbent or not. 

3. On a panel of unpolished wood, the outline may be 
done directly in oil. It is also well to apply first a coating 
of water-colour fixative, or of re-touching varnish, according 
to taste, and accprding to whether the panel is to be absorb- 
ent or not. Oil painting adheres admirably to the fixative. 
When we said that for outlining in water colours impasta- 
tion was not to be used, it was by way of caution, for it is not 
a suitable process for this. But if the outlining be done 
directly in oils, we must also dispense with it, and that 
requires much care. 

Oil colours for sketching should be used fresh ground, 

being careful to put everywhere the same thickness (a light 

semi-liquid), so that all the parts, however different in tone, 

may have a generally equal coating, without blisters or harsh 

ouches. . 

The merest trace of siccative should be put into 
black, and the lakes, so that the oil of this first coat, not 



OUTLINES IN OIL. II 3 

drying too quickly, may penetrate deeply into the pores of 
the object ; and the badger brush is not to be used, so that \ 
this oil may not be brought back to the surface. 

Each part of the picture should be outlined in flat 
tints, of the lightest and most intense tone possible, of 
the principal colour of the object which they represent, 
because the lower layers of colour having always a tendency 
to work upward, it is best that they should be very brilliant, 
as this counteracts the tendency to darkness of the upper- 
most layers. 

Great care must be taken to blend the outline, and to leave 
no careless stroke of the brush to be a trouble afterwards. 

Before re-painting this sketch, any roughness which may 
exist must be taken off with a very sharp scraper. 

In short, this outline directly in oil is more a preparation 
given to a support to make it suitable for painting, than an 
intelligent sketch. It may be answered : But this is dull 
and monotonous ; it is a manoeuvring method ; nothing is. 
left to inspiration or to chance. Firstly, let us always leave 
as little as possible to chance ; and as for inspiration, it is just 
in order to give it more liberty at the moment of finishing, 
that we take so much pains with the preparatory part. If, in 
the warmth of execution, you leave little empty spaces be- 
tween your touches, you will find them very convenient : the 
tone of the outline being almost definite no longer needs to 
be blocked up everywhere ; whilst if you introduce another 
tone into the sketch, all these little intervals have to be filled 
up, which will soften the execution and give more liberty 
to the painter. If just at the spot of a delicate detail you 
fall upon an impastement or an empty place, as will be 
found in an inspired sketch, you will be greatly troubledr- 
and it will be quite another bungling work to fill up the 
holes and scratch off the lumps ; and frankly, if there i to 



114 SCIENCE OF PAINTING. 

be any bungling, it is better it should be below than above. 
Besides, if the sketcli has any faulty features, or any particu- 
larly strong points, as in finishing the primary drawing is 
not exactly preserved, these features are much less trouble- 
some if the outlines and accents are but lightly marked. 

Inspiration (here it is !) might induce you, whilst executing 
the painting, to be satisfied at certain places with a simple 
scumbling, which would be all right on a solidly and 
evenly covered foundation; but if you happened just at 
that place to be on a part of the inspired sketch where 
there was already almost nothing, those two almost nothings 
one over the other would not suffice, and you would be 
forced to fill up with colour this forgotten place, to the detri- 
ment of that lightness of execution which is just what you 
wanted to keep. 

Besides, you can always in finishing make the tone as 
soft, as broken as you wish, on a brilliant sketch, even 
a little crude,, whilst you will never obtain a colour at its 
maximum of intensity on a dull sketch. On the contrary^ 
by putting an intense colour over itself, you increase its 
power in a considerable proportion. 

In short, it is to leave to the artist liberty to execute to his 
own taste solid painting, semi-liquid, scumbling, and even 
glazing, that we advise to him a sketch which never con- 
strains, and which ensures to him the physical possibility, 
by realising all his fancies, of working out his inspiration as 
far as he has any. 

And then this sensible and regular sketch is the guaran- 
teed health of the painting ; it is its under garment. 

That we may wear with impunity, at all seasons, light 
fanciful clothing, we wear underneath a good flannel : well ! 
the sketch which we are recommending is the flannel of the 
picture. 



THE EXECUTION. II5 

The sketch being finished miist of course be left to dry 
before re-painting. 

As its colours are not thick, and as the oil is partly 
absorbed in the wood, or in the sizing, it is not necessary 
to wait as long as if you had sketched on a non-absorbing 
surface with impastements. A month in a very dry studio, 
or a fortnight in fine summer sunshine, is quite enough. 

When the sketch is very dry, a general coat of re- 
touching varnish should be painted over the whole picture 
before continuing. This varnish, as we said above, dries 
in a few minutes, and may be immediately painted over. 
The object of this varnish penetrating into the sketch is to 
go and fill up all the empty spaces in the coating of colour 
left by the oil absorbed into the support painted. Filling 
up the spaces in the coating of colour, it will deposit on its 
surface a skin of normal resin, which will serve as a link 
between this coating and the following one, and it also 
removes dull spots, and gives more brilliancy and trans- 
parency. 

The Execution. 

We have said that, in the execution, the artist, released 
from all trammels, might paint to please his own fancy ; we 
shall, however, remark that excessive impastements, besides 
not being always seen underneath, are rather destructive to 
the solidity of the painting, and it is not necessary to make 
much use of them, since finding always in places which are 
in the light a luminous sketch, and in dark places a sketch 
already dark, in order to cover them we shall not require 
efforts which always show by a thickening of colour, when 
we want to produce light on a dark ground, or darkness 
on a light ground. 

Here an objection naturally presents itself, if, in spite 



Il6 SCIENCE OF PAINTING. 

of one's knowledge, one makes a mistake in the sketch, or 
if one changes his mind — ^for instance, where he had 
sketched somebody in blue wishes him to be in red, or 
if, after having intended to put a coloured tablecloth on 
a table, it is wished to replace it by a white tablecloth, 
etc. 

To this we reply that there should be no hesitation in 
promptly and completely removing the sketch with ben- 
zine at the place where the change is desired, and then 
putting in a new sketch as wished. 

Of course it is always better, when possible, to put every- 
thing in at once without any changing, but it is certain that 
it is not always possible to do this successfully. Certain 
portions are sometimes unsuccessful, and glazings are neces- 
sary. 

When forced to go over a certain piece several times, it 
should never be done without first rubbing a little re-touch- 
ing varnish over it, and the same piece should never be 
re-painted two consecutive times with solid colour: Z.^., 
avoid re-painting. 

Re-Painting. 

If a piece does not satisfy you completely — let us suppose 
it is a head, whose shading you wish to soften, to colour, or 
to brighten — ^with semi-liquids and glazing you can obtain 
what you desire without being obliged to re-paint. But if, on 
the contrary, the drawing of it was defective, features have 
to be altered, the brow made higher, the mouth lower, etc., 
that would necessitate new impastements in light colours on 
the dark parts and in dark colours on the light parts. This is 
what is called re-painting. Sooner or later the re-covered 
parts will show again, and will be a cause of regret. 

Here is a striking example of this kind of accident : There 



GLA2ING. 117 

exists at the museum of Madrid an equestrian portrait of 
Philip IV., by Velasquez, in which the horse has eight legs, 
not all equally apparent, but still they are discernible. It 
is evident that four of these legs were not intended by 
Velasquez. Not liking them as they were at first, he 
had re-covered them with an earth-coloured tone, without 
removing them from the canvas, and then he painted new 
ones in other places. It is absolutely certain that when 
Velasquez finished that picture, the effaced legs did not 
appear, as he assuredly would not have left them there ; and 
it is not less certain that in time they reappeared. 

Re-painted pictures have still another inconvenience, 
which is, that new colours thickly laid on other thicknesses 
imperfectly dry at the bottom cause cracks. Here, again, 
there should be no hesitation in scraping down to the out- 
line the parts to be re-painted in full paste. 

Glazing. 

As for glazing, it should never be put on dry if it is desired 
to have it even. 

The following are precautions which it will be well to take. 
If the place on which you wish to put a glazing has been 
already covered with re-touching varnish, rub it over with 
some petroleum oil and wait a few minutes until the varnish 
gets thoroughly distempered ; then put on the glazing, mixing 
with the colour a little painting varnish, and a little siccative 
if the colour be a lake. When the place to be glazed has 
not yet been covered with varnish, rub a little painting varnish 
over it and apply the glazing as above. 

Besides these preparations one may sometimes be, in 
certain cases, desirous of rendering the colour used for 
glazing more or less liquid, sometimes requiring it to be 
merely of the consistency of a wash. For this purpose use 



Il8 SCIENCE OF PAINTING. 

essence or petroleum oil, according to whether you wish it 
to dry quickly or not. There is only one observation to be 
made — viz., that the more petroleum you put in the glazing 
the more necessary it is to see that the foundation is 
thoroughly dry. It is a question of taste whether the colour 
used for the work shall be more or less liquid or ropy. Each 
artist, with his two varnishes that he may mix in any pro- 
portions he pleases and his petroleums more or less volatile, 
may act as he thinks best : nothing is forbidden, there is no 
destructive excess to be feared. 

The siccative which solidifies oil, on the contrary, should 
be sparingly used, whether in paste or liquid. Very little 
should be put into light tones, none into white lead ; and 
it should be well mixed into the colour with a knife on the 
palette, so as to be equally distributed. 

Embus, or Sinkings. 

Where, in the execution of a picture on account of repeated 
re-touching, embus or sinkings appear, it is possible, as said 
above, to make them disappear with a light scumbling of 
re-touching varnish. This operation should even be repeated 
as often as the stains appear ; for when an embu is obstinate, 
it means that the interior vacuums are not filled up, and for 
the preservation of the picture it is requisite that they should 
be filled up. 

Those embus are the disease of oil painting, and, in order 
to cure it, it must first be well known. Until now artists , 
have been content with getting rid of its immediate effects, 
but without studying their causes, and consequently without 
bringing any remedy to the effects which this malady may 
have in the future. We are therefore obliged at this point 
to give some explanations. 

Ground colours cqntain the oil necessary for keeping 



EMBUS, OR SINKINGS. II9 

together the small parcels of colouring-matter, and for giving 
to them, according to the laws of refraction in centres of 
different density, an aspect more coloured and more trans- 
parent than if these parcels of matter were in a state of free 
powder ; but that on one condition — viz,, that the oil shall 
remain equally distributed amongst all these parcels. And 
that does not always occur. 

Let us say firstly that, in the case which we are considering, 
oil does not follow the laws of weight, but it obeys the 
capillary law, which is that in channels of small dimensions 
liquids disperse in all directions, as much from bottom to 
top as laterally or from top to bottom. 

Now, the interstices which the imperceptible parcels of 
colour leave between themselves, form a number of little 
canals very propitious for this phenomenon. One of the 
best proofs of this is that the oil does not descend to the 
bottom of the picture, although the latter is nearly always 
vertical : it remains in suspension in the layer of colours 
which contains it, but, in the thickness of that layer, it is 
differently distributed according to circumstances. That is 
what we are going to study. 

When a first layer of paint is applied to a panel, a canvas 
or any support — in fact, on the plane surface of any material 
whatever, if that material is porous, such as wood, card- 
board, a wall of stone or plaster — the oil gets partly absorbed 
into it and the colour remains more or less dull, according 
to the quantity of oil it has lost. If the materials on which 
the painting is done have been prepared by means of sizing, 
still the sizing will always be a little absorbent ; and this is 
requisite, so that the oil by penetrating a little may throw 
out the roots which enable it to adhere. In this case a 
little oil is used in this manner, and the colour is still slightly 
dull, but less so than if there were no sizing. 



120 SCIENCE OF PAINTING. 

It would seem that, by continuing to put on one layer 
after another, the oil from each would filter into the pre- 
ceding one to fill up the vacuums there formed, so that we 
should have a succession of layers all dull ; yet this does not 
always occur, for the following reason : — 

If you tread on sand which has been wet, water will 
spring up without the soil sinking. If you even make a 
little hillock of this wet sand and renew the experiment, 
water again comes to the top. A similar phenomenon may 
be noticed in the clay used by potters and in a damp wall 
when knocked. The more you triturate the colour, the 
more the oil comes up and collects on the top. Under 
these conditions a layer of colour applied over another, 
even if the under layer be sunken, remains bright. 

It would still seem that in re-painting over this bright 
surface the layer should be normal. That does not matter, 
because the oil, in rising to the surface, has left, in the 
inside of the layer, some colour deprived of oil : all the little 
canals spoken of above, produced by the interstices between 
the parcels of colours, are empty under this exterior sheet 
of oil, and this is what happens when it is painted upon. 
The oil, leaving the new colour, penetrates through the pores 
of the dried oil on the surface of the preceding layer. It is 
sucked up by the empty canals as if by a sponge, and the 
result is still an embu. Now, the embu will come whether 
you re-paint a dull or a bright surface, if that surface, 
although dry, has not been long dry. But if the bright 
surface is tolerably dry, and its pores are sufficiently shut to 
prevent the new oil from penetrating, the painting will be 
normal ; only the canals at the bottom will remain empty, 
and as often as there are vacuums in the construction of the 
painting it will be to the detriment of its durabiUty. 

It is like a wall made of dry stones merely covered outside 



ii - 



EMBUS, OR SINKINGS. 121 

with a coating of mortar. Should the slightest earthquake 
occur, the mortar cracks and the wall falls. Now, for the 
construction of a picture the movements of the canvas or 
the panel are terrible earthquakes. The pomades used for 
getting out the embus do not penetrate deep enough to 
fill up the vacuums formed. A new mortar must therefore 
be filtered into those little catacombs, and for this work 
petroleum is useful. 

Shall this mortar consist of oil ? 

We said above that there was quite enough of oil in the 
colours. Its being badly distributed is no reason for using 
more of it ; it is better to take norma} resin which will give 
solidity, preserve and even increase transparency, without 
the yellowness and darkness which time always produces 
with oil. 

For this purpose it is well to use resin dissolved in 
petroleum; if this resin dissolves well cold in oil, it is 
because all the pores will remain shut up by this resin if 
no re-painting be done, and should re-painting be done, the 
oil dissolving this resin which shuts up the pores will be 
able to become rooted. 

This ought to explain how everything intended to get 
rid of the embu, which is not soluble in cold oil, is alto- 
gether disastrous. In fact, the want of adhesion makes 
the picture scale off, and is most disastrous to it. 

By observing carefully all the precepts given above, an 
oil painting may be executed under the best possible con- 
ditions for durability, and the maximum of brilliancy and 
freshness can be obtained from the colours. 



v.P. 8 



CHAPTER X. 

THE PRESERVATION AND RESTORATION OF 

PICTURES. 

Once upon a time there was a little dealer in Swiss articles : 
villas, cuckoos, milkmaids and mountaineers of white wood. 
But, this style of thing being no longer the fashion, the 
little dealer, in spite of his intelligence and courage, saw his 
business on the verge of ruin. One day, when no longer able 
to pay his landlord, he was obliged to forfeit all his goods 
to him. 

He took refuge, sad and desolate, in a lodging which he 
toot in a hurry. Fortune at last, compassionating his 
distress, sent to his lodging a messenger in the form of a 
servant from a large house. The servant thus addressed 
him : " Sir, the Count, my master requires your services. I 
have spoken to him of you, because in the neighbourhood 
I was told that you were the nearest. I might have gone 
to look for another, so I hope you will not forget my little 
commission — all the more so as the Count is generous, and 
if you deal with him properly, his business may amount to 
some thousands of francs. We understand each other, do 
we not ? I shall say that you are coming directly." 

The servant ran joyously downstairs, leaving the unhappy 
little dealer perfectly stupefied, unable to understand what 
this unknown Count could expect from him. 

Still, hypnotised by the words "several thousands of 
francs,*' he mechanically took up his hat and stick to go out. 



THE PRESERVATION AND RESTORATION OF PICTURES. 12^ 

As he shut the door, the mystery was revealed to him. 
There it was ! Expert^ engraved in beautiful black letters 
on a brass plate. This plate and the title of expert belonged 
no doubt to the former occupant. 

Might he appropriate them — profit by this mistake ? Oh 
yes ! A drowning man does not trouble about where the 
plank which saves him comes from. So, putting remorse 
behind him, that is if he had any, and resolving to profit by 
this opening, he had recovered his composure when ringing 
the Count's door-bell. The servant, who expected him, 
ushered him into the drawing-room, announcing with dignity: 
" The Expert ! " His fate was thrust upon him — he was an 
Expert ! But expert at what ? 

• 

It was the Count who informed him. First the Count 
wanted to have his opinion about the authenticity of several 
old pictures, then to have some of them re-varnished, and 
afterwards to ferret out the works of promising young artists. 
For the Count had decided partly to renew his picture 
gallery. He considered the old masters full of merit, but he 
thought that an amateur should also interest himself in con- 
temporary artists, and that it is more interesting to discover 
them when rising than to follow with the applauding crowd 
when past their primer. (We see that the Count possessed 
intelligence far above the average.) Finally, he counted 
upon the enlightened assistance of the learned Expert to 
help in realising his plans. The Expert approved in every 
respect of the Count's ideas ; but he ^sked, before giving a 
formal opinion, if he might study the pictures a little nearer 
. . .It was a serious matter ! . . . etc. In short, he 
played his rdk admirably well, and when they separated, 
the Count and the Expert were mutually pleased with each 
other. 

Next day, the Expert's brass plate, brightly polished, shone 



124 SCIENCE OF PAINTING. 

like the sun on the door of the former dealer in Swiss 
articles. 

He knew already that he was doing no harm by keeping 
the title, as it is one which anybody may take. He took 
into partnership a picture restorer, as he was ignorant of 
the first step in his new business. He attended sales, visited 
artists, and in a short time he became a most important 
personage in the commerce of pictures. 

This anecdote, perfectly authentic, is to show how 
indifferent certain amateurs are as to the cqmpetence of 
the people to whom they confide works of whose great value 
they are perfectly aware. 

Were it a question of a valuable dog or horse, those same 
amateurs would not only call in to attend them a properly 
qualified veterinary surgeon, but they would require a 
substantial guarantee as to the skill of this Esculapius; 
whereas for the care of a picture the first comer will do. 

We do not wish to depreciate experts in general. Some 
of them are profoundly learned in their art, but there are 
others quite ignorant. What we blame is the thoughtless 
selection that is made from them; all the more so that 
the pictures abandoned to their care have often damages 
much greater than varnish worn off. They might be repaired, 
for restorers exist who are masters of their art and do 
wonders ; but if they fall into unskilful hands, they are 
irretrievably lost. And our indignation is roused to think 
that the support of a minister, the recommendation of friends 
in good positions, is enough to cause the treasures of our 
museums to be scoured by such hands. 

The end of this will be, that no one shall be allowed 
to take the title of expert in pictures without having passed 
regular examinations, such as are passed by lawyers and 
doctors. 



THE PRESERVATION AND RESTORATION OF PICTURES. 1 25 

This would not give to all experts great skill, but it 
would at least prevent any from being altogether ignorant. 

We have left the picture carefully done and substantially 
constituted. But on leaving our hands, its own life begins, 
and that is sometimes a hard one. 

The pictures which are not appreciated are the least to 
be pitied, for, as we have just seen, it is especially from the 
attentions bestowed upon them that pictures suffer most. 

The first operation to which they are submitted is 
varnishing. 

Varnish is the dress of the picture; it preserves it from 
destructive emanations, it protects its surface, it enriches its 
colours, and when it is faded, soiled by contact with, impurity, 
frayed, yellow, blackened by time and smoke, altogether 
worn out, it is taken off and a new one is put on. CI early » 
it is a dress ! But a dress fitting so closely that we might 
almost call it a skin, and a skin cannot be changed like a 
dress. Each time that a picture has the varnish taken off a 
little flesh comes with the skin. Unless very great pains are 
taken the process is one of flaying. Wishing to have the 
pictures ready too soon, they are always varnished too fresh, 
in which case the varnish penetrates yet more into the 
painting. We are not going to speak as did a celebrated 
practitioner of " the vamisher's art " ; yet to varnish well 
requires great care and long experience. . (See Appendix — 
" Varnishing.") 

When the picture is varnished, it may be left alone for 
some years ; but it is seldom so lucky. 

Amateurs have a habit, when looking at a painting, of 
making a circle with their finger to indicate thd part which 
they admire. 

The little circle is imaginary ; but not so the knocks from 
the admirer's nails. It is even fortunate if the excited 



126 SCIENCE OF PAINTING. 

patron does not hold a lighted cigar or a metal eye-glass too 
near the picture. 

Sometimes the admirer will even rub the remarkable place 
with a little saliva. The remarkable place consequently 
becomes of a dark blue colour, and the darker it gets the 
more the washing with this nicotine saliva is repeated. So 
that, if the picture contains many remarkable places, it soon 
becomes quite disgusting. 

When the amateur leaves home, you might expect that 
the picture would have nothing more to suffer. Ah, but yes ! 
Servants do not take the trouble to draw down the blinds 
when the sun is at its zenith, and, during the summer 
months the unfortunate picture receives every day at the 
same hour a burning ray of sunshine, under which the 
varnish swells, to crack afterwards as it cools. And the 
great cleaning days ! the knocks from feather brushes, whose 
broken feathers scratch it in all directions. And the flies ! 
it is really quite remarkable how they always collect on the 
lightest places, not exactly to eat the picture ! 

Then, winter comes back, with its cigar-smoke and coal 
fumes and general admiration ; until some day the amateur 
gets tired of the picture (which is very likely ! ) or .perhaps 
a tempting price is offered him for it, or he has losses in 
business, or ... he dies ! At any rate, sooner or later, the 
picture changes owners; then the expert appears, which 
always means cleaning and re-varnishing. Poor picture! 
There are unscrupulous people who, to get on faster, instead 
of taking off the varnish with the finger, use alcohol, which 
.takes off the painting, or they even re-varnish it without 
cleaning it, for we cannot call what they do to it cleaning. 
We have seen a very celebrated expert wash all the pictures 
in a gallery, estimated at some millions of francs, with the 
same wash-leather and bucket of water ; the dirt from the 



THE PRESERVATION AND RESTORATION OF PICTURES. 1 27 

pictures of Rubens passed over to the pictures of Teniers, 
and so on, but all were as dirty at the end as at the 
beginning. 

The precautions to be taken for the preservation of 
pictures are, therefore, to varnish them carefully with good 
varnish, to protect them from all abrupt changes of tempera- 
ture, and from any chance of being touched or knocked 
about, and to keep them always in a state of the greatest 
cleanliness, that the taking off of the varnish may be seldom 
necessary. 

But a picture may contract other maladies yet more 
serious than being merely dirty. These maladies come 
sometimes from causes in the painting itself when that has 
been carelessly done. 

The maladies inherent to painting are of two kinds : 

1. Change in the colours. 

2. Defective solidity in the colours on the support. 
The change of colours is due to two kinds of causes :— 

1. Chemical causes; 

2. Physical causes. 

The chemical causes of change in colours are the influence 
of light, which makes them fade or change tone, and the 
reaction which produces and destroys their combinations. 

This reaction is mostly the result of contact amongst 
themselves, or with oil, varnish, etc., which fix and cover 
them, or with the gases contained in the atmosphere. 

All the alterations proceeding from these chemical causes 
are irremediable, and often by trying to cure them the 
existence of the picture is compromised. 

As for the changes which have physical causes, they are 
occasioned by the presence of gluten and disorganised 
varnish, which, placed over each other, darken the colours 
without changing their nature, or sometimes by defective 



128 SCIENCE OF PAINTING. 

# • 

drying causing cracks, etc., or any other accident which 
may interfere with the continuity of the painting. 

The physical changes are reparable with intelligent care. 

The want of solidity in the colours on their support may 
be owing to the destruction of the support under the paint- 
ing, or to the lack of adhesion between the support and its 
sizing, or between the sizing and the pafhting. 

The destruction of the support is produced : if it be a 
panel, by dampness which rots it, or by worms which devour 
it ; if it be canvas, by dampness • which rots it, or by oil 
which burns it. 

The want of adhesion of sizing on a sound support arises 
always from the sizing being of bad quality; either it has 
been affected by damp, or it has become spoiled in itself ; 
but in either case there is no adhesion amongst its particles. 

The want of adhesion of colours on the sizing is the 
result of the same causes. The roots thrown out by oil will 
not hold in a sizing without consistency ; the repeated 
stretching of the canvas, as well as the play of the wood, 
hasten the catastrophe. The repair of all these accidents 
necessitates two operations : re-canvassing, done by gumming 
a new canvas behind the old one to consolidate it: and 
transferring, which consists in taking the painting completely 
off its panel, canvas, or even off its wall to' transfer it to a 
new panel, canvas, or wall. 

Let us say at once that ^en such operations are deemed 
necessary they should be done by professional repairers ; 
we have some who are true artists — extraordinarily clever, 
and who have done the work of restoring in a manner more 
wonderful than any painter could have done. We venture 
to advise to those restorers the use of caseine paste, to the 
exclusion of gelatine or rye pastes, which are much more 
susceptible to damp. 



CLEANING. . 129 

Trivial accidents, such as split or bruised canvas, blistering 
of paint, caused by excess of heat coming either from the 
sun or a stove, little creases, slits occurring during the exe- 
cution of the picture, through any neglect of requisite pre- 
cautions, in short, all the accidents of the craft, daily occur- 
ring, the artist himself should be able himself to repair; 
and to do this he will find the simplest and most practical 
means described in the Appendix ("Repairing of Small 
Everyday Accidents "). 

• 

Cleaning. 

Pictures sometimes only require to be cleaned. 

In all cases, they should be cleaned before re-varnishing, 
and the complications to be met with are not always easy 
to foresee. 

Besides dust, smoke, and all the other impurities with 
which paintings become covered in course of time, it is 
difficult to imagine all that the caprice of different owners 
may have put on it : egg varnish, oil scumbling, bacon rind, 
vaseline or other grease, burnt wax, carriage varnish, etc., 
even collodion. 

E^ch of these substances requires a different solvent, and 
we require a drug store at our disposal to clean perfectly 
certain pictures which perhaps may be only a few years old. 
(See AipPENDix — " Cleaning.") 



CHAPTER XI. 

WALL PAINTING, 

For the style of painting called fresco painting, one of the 
earliest in use, the sizing is of lime or mortar coloured with 
paints ground and distempered with water, and applied 
whilst this mortar is still 'fresh. 

The colours penetrate into the mortar, and the solidity of 
the painting depends upon that of the sizing itself. 

The colour does not leave the sizing, but often the sizing 
leaves the wall. 

The wall to be painted is first entirely covered with mortar 
made of lime and sand, put on about an inch thick ; this 
first bottom layer making a rough surface is called rough- 
casting ; over this rough-casting the sizing proper is applied 
composed also of lime, but less coarse, and of finer sand. 
Only as much ^s can be painted that same day is prepared 
at once, and the painting is only done when the sizing 
is sufficiently set to bear the pressure of a finger without 
sinking. Long-haired brushes should not be used, as they 
are apt to stick in the lime. 

Re-touching is not possible. The sized part that has not 
been overtaken during the day, and any parts that may have 
been spoiled, must be demolished down to the rough-cast- 
ing, and recommenced next day. 

In truth, it is a barbarous and inadvisable process, only 
spoken of here because it holds a high place in the history 
of art, and we owe to it several masterpieces. But the 



WALL PAINTING. I3I 

bad condition in which 'they are, to speak only of the 
frescoes of Raphael and Michael Angelo, when compared 
with pictures by the same masters executed in egg or oil, 
does not do much to recommend a style of painting so 
difficult to do and whose results are so limited. It is true that 
means have been proposed ^nd even tried for making fresco 
painting easier to manipulate and to re-touch, by mixing with 
the colours paste or mucilage enabling it to be resumed the 
following day; but that is really like distempering in egg, 
fig or cheese paste, etc., according to the material employed. 
The paint thickened and kept back by the substance 
added to it can no longer penetrate into • the mortar, thus 
diminishing its durability, and it is then quite useless to 
paint over the lime, as it may destroy certain colours. Only 
those whose use is applicable to the process should be 
employed^ i.e, carbonate of lime, white earths, enamel and 
ultramarine blues, smoke black. Cinnabar, or vermilion 
may also be used, but they must be prepared with lime- 
water, and that diminishes their brilliancy. 

Wax has also often been used for painting walls ) but on 
walls wax is not sheltered from damp, and that causes it 
to powder. 

The oil and wax painting invented by Taubenheim 
seemed for some time to be an improvement ; but the same 
causes spoiled it, and simple oil painting is now used, but 
with no better results. 

The question has not been properly gone into. All 
painting, good on canvas or panel, would be so on a wall ; 
when the painting is bad, the wall is blamed. 

It has been thought that this difficulty might be got over 
by putting complicated sizing on the wall. In fact, the 
colours do hold better on these sizings than on stone, but 
the sizings themselves disintegrate and fall. 



r . 



132 SCIENCE OF PAINTING. 

There is only one way of preparing a wall to make it 
suitable for preserving painting, Z.^., to size it with resin on 
condition that the resin penetrates deeply into it. Besides, 
stones get very easily permeated with resin, and then become 
so hard that iron tools can scarcely break them. Here is 
the process: First, instead of carefully filling up all the 
joints and holes with cement, which sooner or later always 
gets loose and falls off, you should, on' the contrary, 
thoroughly clean all thef interstices, and put bare stones 
everywhere. Afterwards dry it as much as possible by 
means of a chafing-dish passed up and down before all 
p^rts of the surface. 

When the wall is thoroughly dry and still warm, give it a 
first coating of resin dissolved in volatile essences, and when 
this varnish is set, by means of heat make it penetrate into 
the interior of the wall, repeating the coatings of varnish 
in the same way, until the stone refuses to absorb any more : 
and only then fill up any holes with a mastic made of the 
same varnish, fine sand and wax. The last is applied hot, 
with a glazier's knife. The wall thus prepared is now ready 
to receive the sizing you select as suitable for the kind of 
painting that you intend doing. 

Should oil painting be chosen, first apply a thick coating of 
re-touching varnish which, adhering by affinity with the resin 
already imbibed by the wall, will serve as a link between 
it and th^sizing that you will next apply, composed of white 
lead ground in oil and distempered with painting varnish. 

If wax painting be the style that you choose, the sizing 
must be composed of zinc-white ground with essential oil of 
petroleum and wax dissolved in re-touching varnish ; this 
sizing being dry, should be heated 30 that the materials 
of which it is composed may incorporate properly with the 
resin in the wall. 



WALL PAINTING. 1 33 

» 

Finally, should it be water colours that you choose, — 
yes, water colours, and that would be the best process, — the 
sizing must be composed of resin and zinc white, ground 
together with water : four parts of resin to five parts of zinc 
white by weight. After being applied and having dried, it 
must be heated so that the resin in melting may assimilate 
with the zinc white {see chapter on Water Colours, — " Water 
Colours fixed by means of fire "). 

This sizing may be rubbed when quite cold with 
pumice-stone powder and cold water, and other coatings can 
be applied above, until the surface becomes as smooth as 
semi-vitrified porcelain of dazzling whiteness. 

Over this hard sizing you should paint with colours 
specially ground with a solvent and glycerine. Those 
colours keep fresh for months if desired, and if you wish to 
dry them- you have only to heat them : the solvent melts like 
the enamel of earthenware, and when all is cold, after a few 
minutes' interval, wash with fresh water to take oflf the 
superfluous glycerine. Re-touches are always possible, and 
the painting is indestructible, almost as flat as pastels. It 
may be washed with black soap or potash, and resists the 
most violent acids. This process may be applied to all 
sorts of materials. We had invented it to do water colours 
on- wood and even on paper. We shall have occasion to 
speak of it again. {See chapter on Water Colours — " Water 
Colours fixed by means of Fire.") 

It is very easy to add wax to these colours, whether in 
painting or afterwards, rendering the wax invisible with water 
by means of* ammonia {see Appendix — "To render wax 
miscible with Water and Glycerine") ; in this case, it is melted 
with resin after using the hot chafing-dish, and the painting 
obtained by this means resembles the wall paintings of 
Pompeii which are always, although wrongly, called frescoes. 



V 



134 SCIENCE OF PAINTING. 

There is still another means of decorating walls besides 
painting them : that is, to cover them with painted canvas. 
In this case the canvas is pasted on the bare wall, or on" the 
oil sizing with a paste made of oil and white lead, or with 
rye paste. This operation is called priming. 

It is better to prepare the stone with resin, as we said 
above, and to mix picture-varnish with the oil of white lead. 
The use of paste for this kind of work is absolutely bad. 

On walls thus imbued with resin, especially in halls 
or theatres where there is much emanation from gas^ 
you may, by means of water-colour fixing, paste paintings 
executed in water-colours on paper, which, afterwards covered 
with several layers of the same fixative, would be as solid 
as earthenware, and as easily cleaned, for neither potash, 
acids, essences, nor even benzine, can attack these pictures. 

With these processes, which are not crude dreams, as for 
eight consecutive years specimens of them have been shown 
at each exhibition of French water-colour artists, we no 
longer ought to see what we have hitherto seen : master- 
pieceg covered with smoke in the lobby of the Opera 
House, which if cleaned at all must be done by rubbing 
with bread-crumbs for fear of spoiling them, a process at 
once expensive and insufficient. What is wanted is a 
commission of competent men thoroughly to study these 
methods, and if approving of them, recommend their use 
to artists, who should upon certain conditions bind them^ 
selves to use them. Is what we desire impossible ? Im- 
possible is a word that we are told is not in our language* 
Alas ! we always find it in a question of administration. 



CHAPTER XII. 

CRAYONS, DISTEMPERING, EGG-PAINTING, WATER 

BODY-COLOURS. 

When colours are ground merely with water, it is the 
medium of cohesion added to them to make them stick on 
the support, paste, gum, etc., that seems to determine the 
numerous different styles of painting to which this principle < 
has given rise. But it is rather the quantity of mediums 
than any difference amongst them which causes the variety 
of processes. In fact, as the proportion of medium increases, 
the transparency of the colour increases also, and the aspect 
of the painting is no longer the same. 

In classing, then, these processes by degrees of trans- 
parency, we begin with the crayon, which is not transparent, 
and in which the colours contain so little medium, that they 
remain in a state of powder. 

Next comes distemper, which is a half pastel. There is 
only a very little medium in it, but yet sufficient to obtain 
rather more solidity, and rather more transparency. Then 
come water body-colours, and egg-painting, in which the 
quantity of medium continues to increase. We arrive at 
complete solidity, but not at the utmost possible trans- 
parency. Ultimately, with transparent water-colour, the 
quantity of medium always increasing, we can arrive at a 
maximum of transparency almost equal to that obtained by 
varnish. 



136 SCIENCE OF PAINTING. 

The mediums used in these different processes, having all 
the same solvent {t\e,y water), and generally having much 
affinity amongst themselves, can be easily mixed. Con- 
sequently, there is nothing to prevent us from using several 
of these processes for the execution of the same picture. 
We can thus arrive at uniting all the qualities of opacity an.d 
transparency desired ; but the solidity, for instance, will not 
be equal in all the parts, and it is impossible to establish it 
uniformly, for reasons which we are about to give, in con- 
nection with the never-ending question of fixing crayons. 
• 

Crayons. 

These colours are ground with pure water. The clay 
added to them (generally pipeclay) is sufficient to preserve 
them in the form of a stick when they are dry. Those 
which do not contain clay are ground with water very 
lightly gummed. 

It is then in a state of powder that they are put on the 
support — paper, cardboard, canvas, etc. — and they are only 
kept on it by mechanical means, so it is necessary that 
this support should have a rough natural surface, or 
that it should be made .so with a layer of pumice stone or 
powdered sand mixed into some kind of paste. 

There are some useful points to indicate in the preparation 
of supports destined to receive crayons. Amongst the 
numerous causes of destruction in this kind of painting, the 
two principal are that the powdery colours easily leave 
the surfaces on which they are stuck, and that not being 
protected by any gluten, they, more than any others, are 
susceptible to damp and to emanations from gas. 

Now, the supports generally chosen for painting in pastels 
are those most conducive to its destruction. Canvas or 



CRAYONS. 137 

paper stretched on a frame is quite a sponge for dampness, 
and at the same time a drum which every noise and the 
rolling of carriages keep in a state, of perpetual vibration, 
the result of which is to make the powdery colour come off 
quicker still. On the contrary, such materials should be 
chosen as are little vibratory, and rather thick, e,g,, card- 
board, and secured from damp behind, and in front, 
either with water-colour fixative, or with painting varnish. To 
this sbme people will object that to paint in crayons on 
stiff objects is very difficult, that crayons break easily, readily 
crumble, and that the flexibility of the stretched paper or 
canvas is more agreeable. It is a question of lightness of 
hand ; but as some people are unwilling to let a requirement 
of solidity disturb their habitual customs, there is {see 
Appendix — " To prevent the Vibration of Stretched Canvas 
or Paper for Crayons") a means of stiffening canvas and 
paper stretched on frames, after the work is finished. 
Pumice-stone powcjer, sand or powdered glass, which give 
roughness to supports, should also be applied by means of 
impervious materials such as fixative or varnish,, and not 
with a susceptible paste liable to putrefy. 

If the cardboard used be thin, it should first be floored 
to increase its stiffness. 

We may give to the crayon a little more solidity than it 
has naturally, but to fix it completely is not to be hoped for : 
that is quite impossible without destroying the velvety look, 
which is its principal quality. 

To explain this it is useful to refer to the physical laws 
of light. 

The parcels of colouring matter which constitute crayon, 
colours are all in a free state, kept together merely by pres- 
sure of air, and held on the support by natural or accidental 
grapples, which catch on its rough or velvety surface, for th« 

V.P. ^ n 



138 SCIENCE OF PAINTING. 

power of the slight gluten which keeps them in sticks is 
broken directly the sticks are rubbed. 

These parcels reflect, by diffuse reflection^ the quantity of 
white light, and the uncoloured rays of the decomposed light 
absorbed, which determine their proper colour, increase 
in intensity by the fact that they reflect each other.- Further, 
these parcels often have smooth surfaces, which reflect the 
white light by specular reflection. Those of the surfaces that 
are placed at a propitious angle of incidence, send direct to 
our eye the light which they thus rfeflect ; the others send 
that light on the neighbouring parcels, which are thus 
further lighted, and their luminous intensity is consequently 
increased. All the reflections, diffuse and specular, from 
the parcels reach our eyes through a transparent homo- 
geneous medium — viz., the air in which they are themselves 
bathed. 

All these parcels cannot be fixed except by uniting them 
by some glutinous and transparent material. This material, 
in order to penetrate easily through the powdery colours, 
ought to be in a solution, but slightly concentrated in a 
volatile liquid without influence, and, whether it be applied 
behind a spongy object, or sprinkled in front by means of a 
spray, it will penetrate, attracted by the vacuum, through 
the interstices which separate the parcels, according to the 
laws of capillary attraction, and will come to accumulate first 
round those which are nearest to the support. 

If this material is in small quantity so as only to seize 
the parcels in the lower part of the layer of colours, it will 
solidify them without the appearance of the crayon being 
thereby changed, because those imprisoned parcels are 
just what we do not see ; . but the upper part of the layer 
will not be fixed. 

If we increase the quantity of glutinous niaterial so as 



CRAYONS. 139 

to -reach the surface of the layer without covering it, the 
solidity will naturally increase, since all the parcels will be 
laterally bound by the agglutinative — that is to say, they 
will be bathed in a transparent medium of greater density 
than air, and there will be produced, for the upper parcels 
that we see, new effects of refraction which will somewhat 
modify the sensation that they produce ; but the external 
surfaces of the parcels which are the most visible not being 
yet covered by the agglutinative, and consequently continu- 
ing to give the first sensation, the general aspect of the 
crayon will be little changed.. 

At this stage a distemper is being made of it : it no 

longer falls in powder when shaken, but still it comes off 

when rubbed ; if required to fix it entirely, the quantity of 

^gglutinant must be increased until it covers all the upper 

parcels to a sufficient thickness. 

Then these parcels are quite drowned in a transparent 
medium thicker than air, and they change entirely. 

This brings us to the aspect of a water colour more or less 
impasted. 

The crayon is quite fixed, but it has no longer either its 
velvetiness, bloom, or dull softness ; it is no longer crayon. 

So, in fixing crayon, it is better to stop short at half-fixing, 
corresponding to the consistency of distemper^ 

This process is especially good for outlines and founda- 
tions, which thus acquire a comparative solidity, and can 
spare a little of their bloom as they will afterwards be 
re-painted. A mistiake is made, in using for this purpose 
fixatives with a basis of gelatine, which they all have, fi:om 
the first invented by Latour more than one hundred year^^,- 
ago, to the most recent — which, privately, is exactly the 
same. 

A substance is thus introduced into the colour that 



140 SCIENCE OF PAINTING. 

attracts damp and causes fermentations of which the result 
is often the loss of the crayon whose guarantee is desired. 

Only incorruptible and impervious substances should be 
used as agglutinatives. 

Now, be quite convinced of this principle — that, whatever 
the process of painting used, the results arrived at will be 
the same. 

By grinding any pigment with petroleum as well as with 
another volatile liquid, either alcohol or water, the petroleum 
once evaporated, that pigment would be crayon. By adding 
an agglutinative sqluble in petroleum, oil or resin for example, 
in a very small quantity at first, the pigment would take, 
when once dry, the consistency and appearance of distemper ; 
and in proportion as you increased the quantities of oil or 
resin, you would see solidity and transparency increase. 

In short, whether the pigment be ground with more or less 
of any agglutinative, or whether more or less agglutinative be 
made to penetrate into a layer of colour already laid on, it 
comes to the same thing, and there is no getting out of this 
dilemma : — either the colour remains in powder and is not 
solid on the support, or an agglutinative is added which 
solidifies it, but then it is no longer in powder nor has it 
any longer the qualities of crayons. 

The colouring-matter used for crayons should be the same 
as those considered substantial for other kinds of painting. 
Carbonate of lime may even be used. It gives a desirable 
white, in the sense that it is not affected by gas emanations 
and cannot be used with oil because it does not adhere. 

Unfortunately, manufacturers of crayons are induced more 
than any others to give unsubstantial productions, because 
with these same carbonate of lime whites dyed with aniline 
dye, they obtain crayons of a good consistency and of 
magnificent tones, but which fade on exposure to light. It 



DISTEMPER PAINTING. I4I 

would ibe well, therefore, for these colours, to exact the 
same* guarantees as for oil colours, and to be particular 
about knowing whether, in the mixtures made by the manu- 
facturer to prepare the gradations of broken tones *which he 
presents to us, there be no substances liable ' to produce . 
chemical reaction on each other. 

Distemper Painting. 

In this process the pigment is ground with water and 
distempered in painting with animal gluten, rendered 
liquid in a balneum. We shall only just mention this style 
of painting, which is scarcely ever used except for theatre 
decorations. 

It is not the object of this book to teach all the different 
styles of painting which it describes, but merely to give to 
artists, whom we suppose to be already experienced, the 
means of rendering their work more durable. Therefore, 
why stop to consider a process which is only used by some 
of them for outline work, especially as we consider this use 
of it bad and only desire to dissuade them from using it ? 
In fact, as distemper is much too absorbent to be re-painted 
in oil, a preliminary layer of oil or varnish should be put 
on, and this darkens the distemper considerably, because 
it always resumes the tone that it had when wet ; all the 
benefit of its characteristic quality of freshness is thus lost. 
A good plan is to increase the quantity of paste, thus making 
of it a water colour in paste, instead of in gum. 

In this condition it is less absorbent and does not change 
tone under the layer of varnish or fixative, with which it 
should be covered before painting in oil. Only, gelatine in 
so large a quantity has the fault of scaling off; and as, for 
other reasons already explained, we exclude it from sizings, 
why bring it into outline work ? 



142 SCIENCE OF PAINTING. 

Cheese paste, which has not the same inconveniences might 
be used, but of it also a large quantity would have to be put. 

Now, as we have just seen, it is not the kind of paste or 
gum used which makes of a painting distemper, or water 
colour: it 'is the quantity put in. In distemper, the 
quantity of paste is so small that the parcels of colouring- 
matter are held together without being covered ; in water 
colours, on the contrary, the quantity of gum is large enough 
for the parcels to be completely drowned in it. 

Then with gelatine or cheese paste or gum, you can 
graduate from distemper to water colour. 

Well, it is in water colour, and not in distemper, that 
outlining should be done, i.e., with much paste or gum in 
the colour ; and as gum-arabic is more transparent than 
paste, we prefer it for this purpose. 

. As for those authors who have written that Veronese 
' outlined in distemper, they have not stated definitely the 
precise use of the word, and from this mistake have come all 
the unfruitful attempts which have been made to recover 
this process of the Venetian masters. Yes, they have 
outlined in paste, but with sufficient paste for the sketch to 
be transparent and impervious to oil in the necessary 
measure, as water colours are, and not floury and absorbent 
like distemper. 

Water Body-colours. 

Opaque water colour is merely distemper ; only its colours 
are distempered with gum-arabic melted in water, instead 
of animal gluten. We have, therefore, nothing more to say 
on this subject. 

Egg Painting. 

This process, one of the most ancient, lends itself to a great 
many combinations. It inay extend from distemper to water 



EGG PAINTING. I43 

colours, /.tf., from the greatest opacity to the greatest trans- 
parency ; and as it allows the addition of resins and of wax, 
it may acquire a solidity which oil painting will never have. 

Formerly the colours were ground with water, and dis- 
tempered with yolks of egg fresh emulsioned with cold water 
(this is egg distemper) ; to this was sometimes added natural 
white of egg or albumen to increase transparency. To 
introduce resins, they were first dissolved in essence and 
as varnish mixed with the egg, either directly or emulsioiled 
with water. 

To introduce wax, it had first to be rendered miscible 
with water, through the medium of an alkali, and at that 
time only one was known — viz., lime. 

It is by cleverly-used mixtures that those paintings of 
the middle ages were obtained, which have stood out for 
many centuries on damp walls, and which have often been 
mistaken for frescoes. Similarly, many pictures on wood, 
copper, slate, or other materials painted in. the same way, 
have been looked upon as oil paintings. The reason of this 
mistake is that, in these paintings the flesh shadings have 
been so harmoniously finished that they could only be done 
with a viscous paste long malleable, like oil colour^ but the 
painters of the middle ages obtained these same results by 
directly triturating the yolk of egg without water, but with 
resin; the oil contained in the egg dissolved the resin, 
and colours dissolved with this paste had absolutely the 
consistency of oil painting. 

To-day, if we seek to imitate this style of painting, it 
is not necessary to take eggs ; it is easier to analyse the 
materials contained in those mixtures and, by taking only 
those which are usefuj, thus reproduce this ancient process. 

What is there in an egg ? 

The yolk and the white. 



144 SCIENCE OF PAINTING. 

What is there in the yolk ? 

There is some vitelline, analogous to caseine, an oil, 
besides some sulphur and other materials that we need not 
consider. 

What is there in the white ? 

Albumen and other matter not required for our purpose. 

To reconstitute the useful parts of the egg, we therefore 
only require caseine, oil of egg, and albumen. We can* 
introduce into it resins by dissolving them directly in oil o^ 
egg, introduce into it wax with volatile alkali (ammonia), 
which transforms at the same time caseine into paste ; and 
we have then the egg painting, re-made chemically and purer 
than before, since we have not the useless parts of the egg — 
amongst others, sulphur, which would even be destructive, 
if used with white lead. A painting executed by this process 
is extremely solid, especially if covered over with a final 
varnish of good quality. For this purpose we might try a 
varnish composed of normal resin dissolved in egg oil in 
the proportion of two-thirds resin to one-third oil. As this 
varnish would be much too thick to be used, it might be 
applied with volatile petroleum, which, once evaporated, 
would only leave the oil and resin. But this varnish dries 
very slowly, it remains sticky for weeks, and it would be 
necessary to keep the picture sheltered from dust during 
all the time it was drying.; therefore we do not give this 
formula as a very practical one. 

Oil of egg can also dissolve copal, and decomposes it 
much less than any other oil, because the boiling point of egg 
oil is just the same as the disintegrating point of copal — 370*^ 
Centigrade — and the copal being well immersed in the boiling 
egg oil, cannot thus be brought to any higher temperature. 

The solutions of copal in the egg oil are uncoloured, and 
there is no loss of weight. 



EGG PAINTING. 145 

Varnishes thus obtained are therefore much stronger than 
those of linseed oil, and do not get yellow. 

All this, as we have said in connection with egg oil, is 
perhaps prospective, but, for the present, no one has yet 
studied this question, for the few experiments that we have 
been able to make cannot be instanced as a sufficient study. 
We have, alas ! been unable to continue our experiments, 
for the never-ending reason that life is short, and that to 
undertake everything is a sure way to accomplish nothing. 



CHAPTER XIII. 
WATER COLOURS, 

We have at length arrived at water colours. 

Under this name is meant, to-day, a very complex style 
of painting which includes impastements, opacities, and 
transparencies. It is, in different proportions, a mixture of 
the ancient paintings on missals with opaque water body- 
colours and washes. All these styles of painting, which have 
for liquid, water ; and for agglutinative, gum-arabic, are of the 
greatest antiquity ; but water colour properly so called, which 
is only a wash in colours, and where the paper is reserved for 
the lights, scarcely dates back beyond the beginning of this 
century ; for the artists who, before that time, used washes 
for their sketches, confined themselves to a few neutral tints 
which never went beyond a camaieu. Of all kinds of 
paintings that can be done with "colours ground with gum, 
having the same causes of destruction and requiring the 
same care for preservation, we shall not make special 
articles ; we shall confine ourselves to giving the necessary 
instructions for doing water colours in general, in a sub- 
stantial manner. 

Paper. 

Water-colour paper should be made only from linen rags, 
and should be bleached only by the action of pure water, 
air and sunshine \ but it is very seldom that such is to be 
found. 



PAPER. 147 

Cotton is introduced into it and, as it is sold by weight, 
kaolin or other heavy substances. To bleach it, chlorine or 
other chemical agents are used, which burn the linen and 
are often destructive to the colours. 

The sizing, which prevents it from being too absorbent, 
should be equally distributed in the paste and not put on 
the surface just at the last ; otherwise, as soon as the outside 
gets worn out by prolonged work, the inside is found to be 
irregularly spongy, and this causes stains. Not only the 
paper should be dry when used, but it should never have 
suffered from damp from the time of its manufacture, 
because then the sizing ferments, decomposes- and loses its 
properties. 

English manufacturers, to whom we are indebted for all 
water-colour requisites (one scarcely knows why!), send 
enormous quantities of their paper into France, and, for 
reasons of economy, the goods are conveyed to Paris by 
water ; so that sometimes the paper remains for weeks at the 
bottom of the hold in the ships, when arrived at the qiiay. 

Besides, the business being carried on by wholesale 
dealers, the latter, when they receive the reams of paper, heap 
it up on the ground floor of warehouses, sometimes even in 
cellars, until the paper is delivered over to the customers. 
After that the paper dries : but it is spoilt. 

We should either make our paper ourselves, which is not 
practicable, or a society of important artists should arrange 
with a manufactory (everything tends to this) to obtain paper 
in good condition. 

Whilst awaiting this golden age for artists, there is only 
one means of getting good paper ; and that is by choosing 
it. A paint box should be taken to the colourman's, the 
trial of a sheet of paper there made and, when found suitable, 
a stock of it should be bought. 



148 SCIENCE OF PAINTING. 

Paper well preserved, in a dry place, at a moderate 
temperature, does not spoil : on the contrary, it improves. 

As for any observations that you might make to your 
colourman for him to repeat to his dealer, thence to pass by 
the traveller to the manufacturer, they would be only trouble 
wasted. In this respect paper is not alone : it is the same with 
every other article ; and the objections of artists, even when 
of high reputation, are of no more importance to these 
gentlemen than are the cries of the sheep in the slaughter- 
house. 

Gums. 

The pigments for water colours are ground with gummed 
water ; but the choice of the gum is of some consequence. 
Gum-arabic was excellent for this purpose, unfortunately it 
can no longer be used ; for the very good reason that it is 
not to be had. 

How ? — ^it is not to be had ! All the druggists sell it. 

Yes, they sell a gum which they call arabic. 

Is it then false ? 

It is false in one sense, i.e, not being the genuine, it is 
false ; but the genuine, no longer existing, there cannot be 
any false. And then, such as it is, it is imitated. It be- 
comes then genuine, since it is imitated. 

If this somewhat strained reasoning suffices to quiet the 
consciences of the druggists, their gum-arabic is none the 
less very different from that of former times. It is obtained 
from the same kinds of acacias, that have been planted in 
Senegal and elsewhere, but which ate no longer in the same 
climatic conditions. 

It is supposed that in Arabia the gum of these same 
acacias owed its particular qualities to the heat of the sun 
to which it was exposed for a long time on the trunks of 



GUMS. 149 

trees; and that the trees could only support the high 
temperature of the country by the help of subterranean 
rivers in which the trees plunged their roots. The explana- 
tion is that these rivers are now dried up and become so 
finally ; in the countries where the gum acacias grew, they 
have now totally disappeared. It is •certain that heat is a 
necessary agent ; for, by subjecting the gums of Senegal to 
high and progressive temperatures in stoves ; chemists have 
now succeeded in restoring some of the qualities of the old 
gum-arabic. 

It is then understood that none but the giims of Senegal 
and other provinces are found in the commerce of to-day, 
and that those are the gums which are made suitable for 
water-colour painting by subjecting them to a preliminary 
treatment. 

In these gums there is naturally much variety, and also 
counterfeit imitation. Some of them contain no gum at all. 

Here is a specimen: From dextrine, gelatine or other 
cheap materials melted in water, a thick paste is prepared 
which is passed through a strainer with holes of unequal 
diameter, the edges of which are roughened with a pointed 
file ; the paste comes through these holes by its own weight, 
and the drops have their surface marked with stripes like the 
true gum. When the pieces are dry they are broken, and 
there is the gum ! 

Is it sufficiently Arabic ? 

It is necessary that the water colours should be easily 
spread on the palette ; but at the same time they should be 
sufficiently insoluble for it to be practicable to put a second 
tint over a first without taking the first off. 

This correct degree cannot be obtained for all colours 
with the saine gum. For almost all the gum that has been 
through the stove is necessary, because it distempers easily ; 



150 SCIENCE OF PAINTING. 

but with Others, the natural gum of Senegal is preferable, and 
for others such as emerald green, for instance, dextrine must 
be had recourse to. 

Chromates render the gum insoluble ; and emerald green, 
when not well manufactured, is affected in this way. 

The colouring materials that may he used for water 
colours are the same as for oil painting, and equal carje 
should be taken to make, sure of their purity. (Se€ 
Appendix — " Verification of Colours.") 

In the water colours of commerce we find one great 
fault, especially if it be desired to use them for outline work 
to be afterwards filled up in oil ; they are not all equally 
gummed. 

To obtain this equal gumming, the colours should be 
tried whilst grinding and gum added to them until the 
colour, when dry, has not the same tone as when wet. 
Once arrived at this equal gumming, colours imbibe no 
more at one place than at another. 

Artists, according to their tastes, like colours more or less 
damp ; and to satisfy them large or small quantities of honey 
or glycerine are added: sometimes even sugar is had 
recourse to ; but all these have drawbacks : first, the sugary 
matters attract dampness ; if there is any excess, the colours 
get so soft that, often, some water colours in a box stick to 
each other. 

But it is not only dampness which sugar attracts : it also 
attracts flies, and the harm which they do is irremediable. 
They leave everywhere, in the colour of the fresh tints, 
marks of their visits like so many little touches from a 
microscopic sponge. We have once seen a woman's head, 
very beautifully shaded, attacked by flies, which made her 
appear as if she had had smallpox. 

Often, to facilitate execution, especially for large pieces 



GUMS. 151 

like skies for instancj, very rapid drying is not desired, and 
it is necessary to keep the paper damp. For this a little 
glycerine may be put into the water, but very little ; or a 
solution of gum tragocanth or of chloride of calcium may be 
used. Some ancient miniaturists used for this purpose the 
slime of snails or the juice of the figtree ; but all these means 
are more or less efficacious, and are not without danger. 

Nearly all substances which take a long time to dry, only 
possess that quality, thanks to the affinity which they have 
for water : this affinity with water gives them the power of 
retaining- it for a long time, but also that of resuming it 
very quickly, and might transform water colours into 
barometers. 

A liquid should be sought which should have no affinity 
for water, but which should naturally evaporate much 
slower than it. We have found this liquid ; it has even the 
advantage of taking an hour to dissolve gum, so that the 
top can be re-painted without dissolving the bottom, and one 
may shade in full paste, as in .oils, for several hours. 

If, after having worked thus for some time, you desire the 
work to dry up quickly, by putting the water colour in the 
sun or before the fire this famous liquid will evaporate in a 
few minutes. 

Only (there is an only) this liquid is not an article of 
commerce ; at present it is but a curiosity of the laboratory, 
and actually costs ;;^i2 for a quarter of a gallon. 

This is not very available. 

Let us hope, however, that its production at a reasonable 
price may soon be arrived at, and that water-colour painters 
may be able to utilise this marvel — for it is one. 

In the process of water-colour painting, the uppermost 
colours adhere perfectly, as the second layer distempers the 
first and mixes with it. The only precaution to be taken 



152 SCIENCE OF PAINTING. 

for solidity during execution is to avoid impastements. 
Should white have been used and a light tone be wanted 
instead of a dark one, instead of thickening the touch until 
the dark tone has no more effect by transparency, it will be 
preferable to wash it off first ; and on the unpainted surface, 
even if soiled, much less impastement will be required to 
obtain the same tone. 

Water colour does not contain in itself anything which 
can change or destroy it ; but it is affected by the action of 
the air, water, and many other accidents, and if complete 
solidity be required it should be fixed. 

Fixative. 

Why, some people will ask, should water colours be fixed ? 
They are generally protected by glass, and it is not usual to 
wet them with water. To this we might answer that. an 
excess of precaution can never destroy, and that it is well 
to preserve them from any possible accident. But the 
fixative has another object. Water colours, even under 
glass, are often spoilt by many causes. The dampness 
which penetrates into the paper, facilitating the fermentation 
of the gum with which the colours are ground, causes the 
formation of microscopic fungi. The painting is then said 
to be getting rotten or sticky. 

Excess of heat, produced by the proximity of a fireplace 
or the rays of the sun through glass, brings the gum to such a 
state of dryness that it scales off in imperceptible quantities, 
and leaves the paper, taking the colour with it. The water 
colour, is then said to fade: as an art critic remarked, it 
forms a breakfast for the sun. 

Now, the object of the fixative is to prevent the sun 
from breakfasting upon water-colours, and dampness from 
cultivating fungi on them. 



FIXATIVE. 153 

Penetrating deeply into the paper, it surrounds the gum 
and the colouring-matters with a transparent cement, always 
supple, as hard as glass, incorruptible and quite impervious. 
It cannot be attacked by any acid, so that colours which 
cannot be used habitually, because of the influence of the 
gases in the atmosphere spoiling them, remain, when thus 
protected, perfectly solid. Besides these two destructive 
agents, dampness and dryness, which the fixative paralyses, 
water colours may be ruined in other ways. If left exposed 
to air, the paper gets yellow in time. Even in a box they 
catch dust, and even under glass coal smoke reaches them 
and spoils them. The fixative remedies all this. The 
paper does not get yellow when the water colour is fixed, 
and, however dirty and greasy it may become, washing with 
a clean soft sponge, water and black soap restores its 
brightness and freshness. 

These are the services which fixative renders to the 
amateur anxious to preserve the water colours which he 
buys and which he loves. 

But to the artist, whom modesty forbids to care about 
the duration of his works, fixative offers other advantages in 
the help which it gives to his work. 

The whole or part of a water colour may be fixed in the 
course of execution, to be retouched afterwards above, and 
that several successive times. 

With a dissolving liquid the whole or part of the fixative 
may be withdrawn from a water colour which can be restored 
to what it was before the fixing, so that any amount of 
re-touching is possible. {See Appendix — " Manner of with- 
drawing the Fixative.") 

In a case where the colour did not take easily on certain 
parts of a water colour already fixed, it is only necessary to 
put with a paint brush a little dissolving liquid on the parts, 

V. p. 10 



154 SCIENCE OF PAINTING. 

and to let it evaporate. The colour will afterwards take 
readily. 

The fixative is, besides, an infallible detective of the bad 
quality of any colours which should be banished from the 
palette. 

In order to be convinced of this, it will suffice to put on 
paper specimen touches of all the colours and to fix them, 
or merely pass above them some dissolving liquid ; all those 
which contain aniline or gamboge, and consequently are 
detestable because unable to bear light, will dissolve in the 
fixative and should never be used. 

Water Colours Fixed by Fire. 

We havie spoken, in connection with wall painting, of 
process which might be used for water colours. 

This process, to which we have given the name of fixed 
water colours {see Appendix — " Commercial guarantee"), can 
be used on paper, wood, or stuff, and all materials that can 
resist the degree of heat necessary for fixing them — i,e,^ from 
1 20 to 150 degrees. 

The colours enclosed in tubes can be preserved indefinitely, 
and on the palette remain fresh for months; when used 
they are dissolved with water, or with half water and half 
glycerine, if required to be kept a long time firesh whilst 
working. 

If left to dry on paper they take the appearance of crayons, 
but they can be again damped by means of a vaporiser, and 
when fixed by means of heat they resume the appearance 
which they have when wet. 

The fixing is done by means of a spirit lamp fiirnished 
with a bent tube, the orifice of which is moved about in 
front of the picture; when the colour takes a shining 



WATER COLOURS FIXED BY FIRE. 155 

appearance under the influence of heat it is left to cool and 
washed in plenty of water to take off the glycerine. This 
washing can be done under the tap of k fountain, or with a 
sponge pressed over the water colour, so that the water flows 
vertically, or, if the object is not very large, by plunging it 
into a bucket of water several times. Then it is allowed to 
dry naturally, or the drying is hastened by a lamp held 
pretty far off, and when all trace of water has disappeared, 
the lamp is brought nearer ; at the time the water colour is 
somewhat pale, and it resumes its colour perceptibly in 
proportion as the heat increases. 

When all the colours are restored to their primitive tone, 
the water colour is fixed. It may then be painted over 
without any fear of melting anything ; it may even be washed 
with a sponge like an oil painting; only it must not be 
rubbed too hard because it is not merely the colour that 
would come off but the paper which would tear like any 
wet paper much rubbed. 

Wax may be introduced into this painting. The wax is 
prepared by dissolving it in glycerine with ammonia (see 
Appendix — "To render Wax miscible with Water and 
Glycerine ") : the solution keeps quite well in bottles. 

The wax thus prepared mixes with the colours whilst 
painting, but the best plan is to apply a layer of it before 
painting. 

When this wax has been used once in a water colour it 
will be necessary to apply a layer of wax every time that it 
is wished to repaint it, because the heat of the fixing m^es 
it melt and the new colours will not adhere to it, but with 
this layer of prepared wax they adhere perfectly. 

The use of this process requires some practice, as may 
be understood, and in heating there is a knack of hand to 
be acquired ; but when one is accustomed to it it is very 



156 SCIENCE OF PAINTING. 

easy to do, and the results — of a perfect solidity — ^hold a 
middle place between crayons and water colours. It is well 
to reserve some paper for lights, so as not to be obliged to 
put impastements of white, and the white should be oxide 
of zinc, ifor the carbonates of lead or lime do not bear the 
necessary heat of fixing. 

When the water colour thu^ made contains no wax it 
may be varnished with a light egg varnish, and over that 
with re-touching varnish, fixative, or picture varnish. 

Water colours without wax may also be varnished with 
gum-lac, dissolved in water with borax {see Appe;ndix — 

"Gum-lac"). 
When the water colour contains wax, it is preferable to 

confine oneself to passing over it a layer of wax prepared 

with glycerine, and heating it; the wax melts, and the 

glycerine springs to the surface in tiny drops like lye ; a light 

washing takes it off at once, and a final heating unites the 

whole by spreading the wax equally over all the surface. 

When this process is used for coloured substances, such 

as wood, cardboard, etc., it is well to cover them with a sizing 

which produces a white surface. In this case to avoid 

washing and double heating, the white of zinc should be 

prepared in water without glycerine, and put on very evenly 

with a swallow-tail ; when this sizing dries, naturally it will 

be powdery like crayon, and one heating will be enough to 

fix it.* If in the course of the work it be wished to change 

some parts of the water colour already fixed, to get a white 

surface so as not to impaste, the piece to be taken off should 

be done with a linen rag saturated with the dissolving liquid 

(water-colour fixative), and afterwards with water. Over 

this place a layer of water-colour zinc-white should be put, to 

* The zinc- white ground in water contains the flux which is to be fixed 
by the heat. 



WATER COLOURS IN SARCOCOL. 157 

reconstitute the sizing. If it is on paper that is useless ; 
for after one washing in the dissolving liquid, the paper 
will be found quite white. 

These colours may be mixed with gum, in which case less 
glycerine should be used in the grinding, and they should 
be moistened with pure water. They are used just as in 
water colours, and after being heated there is no need to 
wash them, as there is no glycerine to take off. 

Colours fixed by heat are more waterproof than those in 
pure water colours, but are not altogether impervious, as they 
contain a little gum. 

It is true that recourse can always be had to fixing them 
with fixative, but then it must be done rapidly, and the same 
place must not be done over several times, because ttje 
fixative dissolves the other materials which unite the colours 
with the gum. 

Water Colours in Sarcocol. 

We have sometimes used sarcocol for uniting the pigments 
in water colours. Sarcocol is a gum resin soluble in water 
and in alcohol. 

It was known to the ancients, and was much used in early 
times, especially in Italy. Pliny speaks of it in his day as a 
substance very useful to artists and to surgeons (we may 
infer this from its name) ; bandages were saturated with it, 
and used to bind up wounds. Being replaced in pharmacy 
by cerecloth, and artists not having used it for several cen- 
turies, it is to-day difficult to obtain ; still it can be got, and 
nature furnishes an abundance of it ; it only requires to be 
harvested. 

After being gathered it must undergo some preparation 
to discolour it and extract the sarcocolline, which is the 
only part to be used. {See Appendix — " Sarcocolline.") 



IS8 SCIENCE OF PAINTING. 

Colours ground with sarcocolline, which acts like gum, are 
of an extraordinary richness and colouring intensity. They 
have the advantage of softening much less quickly than those 
ground with gum, consequently allowing glazing over water 
body-colours, and rendering the superposition of tints much 
easier. On the other hand, they have the inconvenience of 
being scarcely soluble when once dry on the palette, and 
the tenacity of this gum resin is so great that in drying it 
takes off the enamel from paint-boxes and leaves the tin 
bare. 

They can therefore only be used easily by keeping them 
damp in little bottles with large mouths, whence they are 
taken with the point of a knife. In this way they can be 
easily kept, by being careful to put occasionally, half water 
and half alcohol into the bottles, the presence of the alcohol 
preventing fermentation. 

These colours may be moistened with water mixed with 
alcohol in various proportions, and even with pure alcohol. 
We have thus a water colour drying very rapidly, which is 
sometimes very convenient, especially with objects more or 
less waterproof, on which the tints in pure water have a 
tendency to melt, and to run into each other. Indeed, it is 
all the more useful that, on materials which absorb little or 
none of the superfluous liquid used to lay on the colour, this 
liquid evaporates all the quicker for being but slightly 
absorbed. 

Colours in sarcocoUine, moistened with alcohol, have 
also the advantage of adhering very readily to greasy surfaces. 
By this means, painting in water colour may be done over 
foundations painted in oil. This process is very speedy, 
and produces wonderfully powerful effects. 

It is very convenient for the decoration of inhabited rooms 
where the smell of oil paint is feared ; and it gives a very 



WATER COLOURS IN SARCOCOL. 159 

substantial painting, especially if covered with wax or varnish, 
according to whether a dull or shining effect be desired. 

This kind of water colour cannot be fixed with the fixative, 
because the alcohol which the fixative contains would 
dissolve the sarcocoUine ; but it is easy to prepare a fixative 
which would not have this inconvenience. 

One word more, for those water-colour painters who have 
the bad habit of sucking their paint brushes : sarcocoUine 
has a bitter taste, something like aloes and similar medicinal 
qualities. 

Finally, all these processes may lend each other a mutual 
aid, according to the style of work; we have often mingled 
. several, and sometimes all, together in the same water 
colour ; but strict attention must be paid to their respective 
qualities and to the different methods in which each should 
be fixed. 



CHAPTER XIV. 
CONCLUSION, 

In finishing this book, we shall repeat what we said in its 
preface. It was not our object to write a treatise in order 
to teach artists that which they know as well as ourselves, 
nor to teach amateurs that which they can only learn by the 
help of a professor. We have limited ourselves to trying to 
destroy the prejudices of ignorance, the destructive practices 
of routine, and to furnishing to those artists who are willing, 
the necessary instructions for making the best use of their 
tools, for procuring substantial materials, and iot using them 
in such a way as shall let their works remain for the longest 
possible time in the condition in which they leave them, 
whatever may have been the processes used to produce 
them. 

The hope that this book will be useful to. those who will 
read it is very natural, but we have still the ambition to 
believe that it will have good results, even for those who will 
not read it. 

The kind reception which the pupils of the School of 
Fine Arts have given to the lessons on the material pro- 
cesses of painting, and the diligence with which they have 
attended to th6m, prove that they begin to be no longer 
indifferent to those questions ; and our pupils — in them 
lies the future ! 

The taste for science coming always in proportion to the 



CONCLUSION. l6l 

Study given to it, we shall soon see the young generation 
occupied in seeking for lost traditions, and in applying 
themselves to profit from the lessons of the past. Already 
the Society of French Artists has appointed a committee 
which will render, we hope, immense service. 

The bad fabrication of the materials used by artists is an 
acknowledged fact, and the idea of remedy is beginning to 
become general ; to-day this question is considered, and 
yesterday it was thought good form to ignore it. On all 
sides symptoms manifest themselves of an approaching re- 
action against ignorance; we see coming a psychological 
evolution which shall lead painters no longer to blush at 
knowing their business; and the moment is, not far off 
when a gentleman who shall say in a drawing-room " I do 
not care what becomes of my pictures after they are sold," 
will be thought as pretentious and as ridiculous as would be 
an architect if he made light of the solidity of the monu- 
ments entrusted to him to construct. 

This roving school on the fields of fancy has lasted long 
enough. Therefore let artists resume the ancient route 
traced by the old masters: they will find there noble 
examples to follow. Rubens, one of the most learned men 
of his time ; Vandyck, a distinguished chemist ; Leonardo 
da Vinci, engineer and mathematician; Michael Angelo, 
painter, architect, sculptor and poet, and so many others, 
have well proved that knowledge does not destroy genius. 

Let us hope, then, that science and painting, after having 
been so long separated,! will remain closely united in the 
future, as they have been in the past, and we shall then 
consider as a great reward of our work, that we have been 
somewhat instrumental towards that result. 



APPENDIX. 

THE COMPOSITION AND MANIPULATION OF VARIOUS 

PAINTS. 

We have collected into this Appendix all the practical 
directions necessary to those artists whose love of the 
science is great enough to induce them personally to 
make trial of the precepts which this book contains. 

But we do not venture to hope that this part of the book 
will find many readers ; and by thus calling attention to it, 
we almost acknowledge beforehand the dulness which is 
inseparable from it. 

To all those readers who find that statements of figures 
put them to sleep, to those ultra-refined beings to whom 
manual work is distasteful, to those lazy brains whom the 
slightest attention fatigues, to the superficial minds who take 
no interest in serious things ; .finally to all those who only 
read in order to amuse themselves, we are conscientious 
enough to say before they turn this leaf: " Beware ! 

Abandon all hope of amusement ! or go no farther ! 
We are about to teach ! " 

Good and Bad Paints. 

Chinese White or White Lead (Carbonate of 

Lead). 

Formerly this was obtained by a process (called the 
Dutch process), which was as follows : — 
Pieces of lead soaking in vinegar were put into earthen 



APPENDIX. 163 

pots, which, ranged in shelves, were buried in ditches the 
bottoms of which were filled with refuse straw and stable 
manure. The acetic acid of the vinegar formed with the 
lead acetate of lead, which was changed into carbonate of 
lead by the carbonic acid escaping from the dung. By 
chemical agency the same result may be obtained in a 
laboratory. 

Since that time white lead has been prepared by solution. 
This is called the Clichy process. The white thus procured 
is not entirely free from the water used in its preparation, 
and it does not cover a surface so well. In reality the white 
which is used, is made by processes almost similar to those 
which are the secret of the manufacturers ; but as the chief 
object of the manufacturers is to produce an article at the 
lowest possible price, so as to prevent competition, they 
have thus arrived at monopoly of production in some articles, 
so that being unable to procure any other, the artist must 
content himself with such white as he can get and that is 
frequently not of a proper consistency. 

It is the same thing with other colours : manufactures on 
a large scale have extinguished private industry ; and now, 
in order to obtain paints suitable for artistic painting, it 
would be necessary either for artists to make their paints 
themselves (which would be impossible),* or for them to 
arrange to have manufactured for them paints especially for 
their use ; and this, we hope, will soon be realisable. 

Carbonate of lead, by means of vapours of sulphuretted 
hydrogen which are often sent abroad into the atmosphere, 
forms sulphur of lead which is black. It is thus that certain 
water body-colours and certain white pencils, made of car- 
bonate of lead, become of a more or less dark grey shade. 
One may by moistening them with oxygenised water cause 
them to return to their primitive whiteness, because then the 



1 64 Science of painting. 

black sulphur of lead becomes a sulphate which is white. 
But if such an accident occurs in a painting, the remedy is 
of no use because the presence of the oil and varnish is an 
obstacle to the said transformation. 

Nevertheless, white lead or Chinese white remains, for 
the time, necessary in oil painting ; because it is the only 
kind which adheres. 

It must be banished from all encaustic or other processes 
requiring the help of fire, because it decomposes in any 
heat exceeding loo to 120 degrees. Neither must it enter 
into any combinations which might contain sulphur, as that 
would blacken it, nor acetic acid which decomposes it, — as 
for instance in a distemper, where one would use the cold 
paste very liquid, to avoid the trouble of the water bath. 



Zinc White (Oxide of Zinc). 

The white of zinc is procured by vapours of zinc oxidised 
by a current of air. 

It is not alterable like white lead, but rt does not acquire 
with oil the same solidity'; it remains more brittle, is spent 
more easily and does not cover so well. Yet one can give 
it more body by compressing firmly powder of oxide of zinc 
by the hydraulic press before grinding it, or also by grinding 
first this powder, and with water making it into cakes and 
drying them in a stove. Zinc white may be used in all kinds 
of painting : it is indispensable for mixing with vermilion, 
to the exclusion of white lead, and also for mixing with 
cadmium, should there be any fear about the manufacture 
of the latter. 

Finally, it is an excellent substance and very agreeable to 
use on all those occasions when, employing much white on 
the support by way of light, much impasting is not required 



APPENDIX. 



165 



Spanish Chalk White, Troyes Chalk White, Bougival 
Chalk White, Meudon Chalk White, Carbonate 
OF Lime. 

All these whites are solid when used with water, but 
when used with oil they become grey and transparent and 
never dry thoroughly ; therefore they should not be used 
even for water colours, when painting in distemper, water 
body-colour or any other kind of painting that is to be 
varnished or touched-up with oil. 

Like carbonate of lead, they do not bear strong heat, and 
like it they decompose with acetic acid. 

Earths, Ochres, Marls, Iron Lake. 

All these colours, consisting of oxide of iron more or less 
calcined, naturally fixed on clay or artificially on alumina, 
are perfectly solid ; but the catalogue of them is difficult to 
limit, for different kinds of coloured earth are constantly found. 

We mention here some of the colours most extensively 
met with. 

When we say that those colours are good it is understood 
that their genuineness is first to be proved ; for it is not 
enough that they are called by the names which we are 
about to give, it must still be proved that they are what 
they ought to be — viz., oxide of iron. 



Italian earth. 

Natural and burnt sienna, 

Red earth, 

Rose earth, 

Yellow earth, 

Foundation ochre, 

Red ochre, 

Prussian red, 

Venetian red, 

Antwerp red, 

Nuremberg red, 



Indian red, 

Colcothar or crocus martis, 

Vandyck brown. 

Red brown, 

Mars yellow, 

Mars orange, 

Mars red, 

Mars violet, 

Mars brown, 

Iron lake. 



1 66 SCIENCE OF PAINTING. 

It is quite understood that this list cannot be complete. 
Oxide of iron is presented and will continue to be presented 
under many other names until artists shall insist upon its 
bearing merely its true name. 

Orange and Yellow Colours. 

We have classed separately those earths, ochres, and 
marls which are yellow, red, and brown, because those 
substances form a distinct category ; but all the other kinds 
of colouring matter, whose chemical formulas are different, 
we shall class according to their colour, so that they may be 
more easily recognised, desiring it also here to be noticed 
that it is impossible for us to give a complete list of the 
numerous fancy names with which the prospectus of an 
artist's colourman is covered. In the first place we do not 
know them all, and before this book is printed many others 
will have appeared. We limit ourselves to the best known. 

Lead, in combination with other bodies, furnishes many 
yellow colours more or less bad. Such are : — 

Certain yellows of a lemon shade (iodide of lead). 

Chrome yellows (chromate of lead). 

Oipiment, king's yellow (arsenite of lead), obtained also by 

sulphur of arsenic. 
Mineral yellow (on a basis of oxy-chlorure of lead). 
Minium ^ 

Mineral orange V protoxide and bioxide of lead. 
Saturn red J 



.Straw yellow J s„tg„iphate oflead. 
* Mmeral turpethj 



All these colours get black or decompose the metallic 
combinations with which they are associated. 

* The subsulphate of mercury, also called mineral turpeth, could not 
be used in painting. 



APPENDIX. 167 

The following are also bad : — 

Ultramarine yellow (chromate of baryta). 

Certain yellows of the chrome kind made with chromate of lime and 
all the mixtures bearing the pompous names of 

Green Naples yellow, 

Brilliant yellow, 

Buttercup yellow, etc 

The following vegetable yellows are also bad : — 

Saf&on yellow, 
Gamboge. 

And all the yellow lakes which fade on expgsure to light 
and are changed by certain metallic combinations : — 

Wold lake, 
Yellow lake, 
Yellow alumina^ 
Golden yellow lake. 

We have said what we had to say about Indian yellow : 
it is a fairly substantial colour, but it requires to be very 
carefully ground so as not to be soluble in water, whilst, 
owing to its alkaline properties, with oil it forms a kind of 
soap. As we can very well dispense with it, being able 
to replace it admirably with iron • lake and cadmiums, we 
always think it wiser not to use it. Naples yellow (lead 
antimony) and antimony yellow (lead antimony and lime 
silicate) are two substantial colours, but very seldom pure 
and very often badly made; and as they are also not very 
useful, we have excluded them from the palette. 

The following are solid yellow colours : — 



Orange cadmium yellow 
Cadmium yellow 
Light cadmium yellow 
Lemon cadmium yellow 



- sulphur of cadmium. 



Before mixing the light shades of cadmium with white 



1 68 SCIENCE OF PAINTING. 

lead, it will be well to ascertain that they do not blacken, 
which would happen if, being badly made, they contained 
an excess of sulphur. 
The following are good to use as yellow colours : — 

Ochresi earths, maxls, iron lake, chromate of strontian and cadmium 
yellow. 

The firm of Lefranc & Co. now make an orange of a 
superb tone which may be very useful ; this colour, a com- 
bination of coal acid and naphthaline, is perfectly solid, but 
it must be used alone and, above all, not mixed with white. 

Red Colours. 
The following are bad : — 

Realgar (Sulphur of arsenic) blackens and decomposes metallic 

colours.* 
Scarlet (Iodide of mercury) fades in the light. 

All the lakes obtained by cochineal fade in the light : — 

Carmine, 
Lake Carmine ; 

or those procured by dyes from woods of Pernambuco, Brazil, 
wCampeachy, etc., undfer whatever names they may be pre- 
sented, as well as those which are due to aniline dyes : — 

. Geranium, 
Nasturtium, etc. 



The madder lakes are comparatively substantial. 

The following are also good : — 

Cinnabar ^ 

French Vermilion j- Sulphur of mercury. 

Chinese Vermilion J 



but care must be taken never to mix them with lead whites, 
but with zinc white only. 

Red colours good to use are therefore all the earths, ochres, 
and marls, vermilion and madder lakes. 



APPENDIX. 169 



Blue Colours. 
The following are bad : — 

Mountain blue (carbonate of copper). 
Berlin blue ^ 
Prussian blue 



TumbuU blue 
Antwerp blue 
Celestial blue 
Turquoise blue 
Mineral blue 



different combinations — formula, Ferrid 
cyanide of iron. 



All these blues of the same origin are decomposed by 
the majority of metallic oxides and disappear when exposed 
to light; some, however, reappear in the shade (excessive 
modesty). 

Still bad :— 

Indigo (a vegetable substance which gets black and green from 
contact with greasy bodies). 

The following are not bad, but useless, as they can be ' 
replaced, and grind badlji:: — 

Pompeii blue (double silicate of copper and lime).. 

Azure blue A 

Smalt blue ' 

Saxony blue y double silicate of potash and cobalt. 

Starch blue 

BlueofZaffre 

Enamel blue (known to the ancients as Alexandria frit). 

. The following are good : — 

Cobalt blue r Combination of aluminum and oxide of cobalt 
iDresden blue \ obtained at a high temperature. . 

f Combination of silicate of aluminum, silicate 
Ultramarme -^ ^^ ^^^^ ^^^ sulphur of sodium. 

Ultramarine badly made may sometimes blacken Chinese white ; a 
preliminary trial of it should therefore be made unless the artist is very 
sure of its quality. 

y.p. II 



lyo SCIENCE OF PAINTING. 

Blue colours good to use may therefore be reduced to 
two, which, besides, are quite sufficient : Cobalt and ultra- 
marine. 

Green Colours. 
The bad are : — 

Prussian green (double salt of cyanure of iron and cobalt ; turns to 

a grey-red in the light). 
Verdigris (acetate of copper). 

Scheele greenj ^^^^ of copper. 
Mineral green J 

t^ng isn green I j^i^tures of chrome yellow and Prussian blue. 
Green annabar J 

Green lake (mixture of wold lake and Prussian blue). 

' Schweinfurt green (arsenite of copper and acetate of copper). 

Vienna green (arseniate of copper). 

Bladder green, a lake made with buckthorn dye, and iris gr^en are 

also bad owing to their want of substance. 

Green earth is also not to be recommended ; it does not 
adhere. As for malachite green, or mountain green, or 
Bremen green, or Hungarian green, it is very scarce and 
difficult to grind. It is well imitated under the name of 
Brunswick green. The true malachite green is substantial 
but none of its imitations are. Veronese green is an arseniate 
of copper of a particular make ; it may be used on condition 
that it is le.ft by itself and carefully covered with varnish to 
avoid any contact with other colours. 

The green colours which are' really good are : — 

Cobalt green (oxide of cobalt and oxide of zinc). 
Emerald green (oxide of chrome). 

Violet Colours. 
All the violet colours obtained by aniline are bad, such 

^S ' Magenta violet, 

Solferino violet, etc. 

Vegetable viole^ obtained by dye of Campeachy wood 



APPENDIX. 171 

mixed with salts of lead, and violets derived from cochineal 
are also bad. 

An ultramarine violet is now made which is as solid as 
ultramarine, but does not adhere well and to which for that 
reason we prefer cobalt violet (phosphate of cobalt and 
silicate of cobalt), and especially mineral violet (phosphate 
of manganese). This last colour, very solid and adhering 
well, is especially useful; it may be had in two different 
shades, both equally good. 

Therefore, for violet colours, preference should be given 
to cobalt violet, mineral violet and Mars violet. 

Brown Colours. 

Amongst brown colours the worst of all is bitumen. It 
fades in light, melts in heat, causes the painting to crack, 
runs and compromises the existence of all the pictures in 
which it is used 

Next comes Cologne earth, which is only wood in a state 
of decomposition. 

Cassel earth, chicory brown, and natural or burnt umber 
(bioxide of manganese), are also bad. Umber is penetrating 
and blackens all the tones with which- it is mixed or over 
which it is laid. 

Prussian . brown (calcined Prussian blue) is completely 
useless, as it may be advantageously replaced by Mars 
brown, which is excellent as a covering brown. 

Imitation bitumen, of which we have spoken and which we 
have the honour to present to artists under the name of 
Viberthrown^ will give an excellent transparent brown, having 
all the good qualities of bitumen without its defects. This 
colour, perfectly substantial, is a mixture of lithanthrax and 
oxide of iron on an aluminum basis. Brown colours, there- 
fore, should be limited to Mars brown, and Vibert brown. 



172 SCIENCE OF PAINTING. 

As for blacks, as we have said, they are all good, except 
those which contain tar. 

Verificaiion of Colours. 

Unless one be a chemist and have at his disposal the 
various requisites of a laboratory, it is impossible to make a 
complete analysis of colours. But with the simple n^terials 
that are always at hand, either in kitchen oi: studio, the 
colours when pure may be verified and their principal 
adulterations may be discovered. 

The following is a list of the necessary materials and 
object's. They are neither numerous, costly, nor difficult 
to piocure. 

Strong vinegar. 

Kitchen salt (in wet solution). 

Copper water. (This can easily be prepared by purchasing 
from the grocer s6me oxalic acid in powder and making a 
solution by dissolving it in water.) 

Aquafortis, Composed of one part nitric acid to five parts 
water. 

Soda crystals in a wet solution. 

A spirit lamp. 

Some little glass vases and funnels, some paper filters, and 
an iron* spoon not tinned. 

The colour to be analysed should first be reduced to 
powder ; if an oil colour, it should first be dissolved in a 
glass of benzine and allowed to settle, the liquid then gently 
poured off, and the process repeated with new benzine. 
This should be done several times, until all the oil be 
eliminated and the powder which remains quite free firom 
grease : it should then be put to dry on blotting-paper.* 

* We insist on the colour being completely free from grease, because 
in the reaction obtained by fire any trace of oil would give rise to 
smoke, which might cause an error. 



APPENDIX. 173 

If the colour to be analysed be a water colour, the same 
process should be gone through with water to remove the 
gums, honey, glycerine, etc. In any case the liquid which 
comes off must not remain coloured, as that would indicate 
the presence of certain aniline colours.* 

It is therefore quite understood that, in all the following 
operations we treat the colours as in a state of dry powder 
and perfectly free from grease. 

White Lead or Chinese White (Carbonate of 

Lead.) 

Put into a glass a small quantity of the white, and pour 
over it about six times that amount of aquafortis. If the 
white be pure, it should dissolve entirely with effervescence : 
an insoluble residue would indicate the presence of sulphate 
of baryta. To this solution add a large quantity of kitchen 
salt in solution, it will form a precipitate white which is lead. 
Filter, and to the liquid which comes off clear, add a solution 
of soda crystals until the bubbling stops. If a precipitate 
white be formed, it shows that the white contained oxide of 
zinc or carbonate of lime. 

Zinc White (Oxide of Zinc). 

Oxide of zinc should dissolve in vinegar : if a very heavy 
white residue remain which falls at once to the bottom of 
the glass, it shows that the white contains sulphate of baryta. 
When the oxide of zinc is dissolved in the vinegar, add the 
solution of salt (twice the volume of zinc) the liquid should 
remain clear : if it form a precipitate, there is carbonate of 

* Sometimes the colours are ground so fine, such as ultramarine for 
example, that the water remains coloured for a long time, and patience 
is required until the deposit is properly formed. 



174 SCIENCE OF PAINTING. 

lead Put back some of the clear solution of oxide of zinc 
into the vinegar, dilute it with fifteen times its volume of 
water and add some copper water, about the same volume 
as there was of the zinc : the liquid should still remain 
clear; if there be a precipitate, it shows that the white 
contained carbonate of lime. 

Strontian Yellow (Chromate of Strontian). . 

Put the chromate of strontian into a glass with ten times 
its volume of aquafortis : it ought to dissolve entirely. The 
solution becomes orange-coloured if a solution of salt be 
added to it; should it precipitate a yellow residue, that 
would be chrome yellow. 

Cadmium Yellow (Sulphur of Cadmium). 

Put the sulphur of cadmium into a glass with four times 
its volume of nitric acid : it ought to dissolve ; the solution 
is milky, and a certain quantity of sulphur floats on the top. 
If the solution be more or less grey, and after the deposit 
the purified liquid be coloured a greenish blue, it shows that 
the sulphur of cadmium contained chromate of lead; if 
the residue be of an intense red, it shows that it contained 
vermilion. 

Vermilion (Sulphur of Mercury). 

Heated in an iron spoon, the sulphur of mercury should 
be completely volatilised. Should a residue remain it shows 
that it is n6t pure. Put to boil in water and filter when 
boiling ; the clear liquid should not, on cooling, precipitate 
any red powder : that powder would be iodide of mercury. 

Madder Lakes. 

Madder lakes boiled with a weak solution of crystallised 
soda give a red colouring ; cochineal lake would give a violet 



APPENDIX. 175 

colouring. The solution of crystallised soda should be 
made with thirty times as much water as lake and an equal 
quantity of crystal and lake. 

Lakes which colour alcohol contain aniline. Whether or 
not they will bear light should be ascertained. 

Ultramarine. 

Ultramarine should dissolve cold in ten times its volume 
of copper water cleared with sulphuretted hydrogen (smelling 
of rotten eggs). The solution is of a milky grey, but with- 
out the slightest tint of blue ; should there be any blue tint 
it contains Prussian blue. 

Heated in the iron spoon, the ultramarine whilst burning 
should not emit any vapour of a beautiful purple colour, 
that would show that it contained indigo: these vapours 
have a strong and characteristic smell. Ultramarine is 
rarely adulterated with indigo. 

Cobalt (Oxide of Cobalt). 

Cobalt put in a glass with ten times its volume of copper 
water should preserve the same tone that it would have in 
pure water; boiled, and left to settle for an instant, the 
floating liquid should be uncoloured. If it were blu6, that 
would indicate the presence of Prussian blue. 

If it emitted an odour of rotten eggs, that would indicate 
ultramarine. 

Cobalt should get red in the spoon without vapour, like 
ultramarine. 

Emerald Green (Chrome Oxide). 

Boiled with pure nitric acid emerald green should not 
change ; if water be added and the liquid strained it should 



176 SCIENCE OF PAINTING. 

be uncoloured. If it be yellow, it is from the presence 
of chromate of strontian, lead or zinc. Boil the emerald 
green with copper water ; after it has settled for a short time, 
if the liquid on the top be coloured blue, that shows it 
contains Prussian blue; heated in the spoon, it should 
emit no vapour; should it emit a white smoke with an 
odour of garlic when put on a red-hot spoon, that would 
show that it contained arseniate of copper. 

Cobalt Green (Oxide of Cobalt). 

This is like emerald green, only it dissolves entirely in 
aquafortis mixed with water and the solution when pure is 
of a light pink. The solution will be orange if it contain 
chromates or does not entirely dissolve; Prussian blue 
would remain at the bottom if there were any. 

Blacks. 

All blacks which are the product of carbonised animal or 
vegetable substances, when kept red-hot for an hour in the 
spoon, will leave an amount of ash equal to the amount of 
black paint. 

Lamp blacks leave little or no ash. 

Earths (Ochres). 

These ^colours are not generally adulterated ; impurities 
they contain vary in degree ; the only deception practised 
is to enrich their tones with aniline dyes : by putting them 
into alcohol we can at once see if the alcohol colours. 

Cleaning. 

To clean a picture, the first thing to do is to wash it with 
lukewarm water and a soft sponge to take off the dust and 
coal slag from its surface. 



APPENDIX. 177 

Afterwards, if it is varnished, the varnish may be taken 
oflf with the finger, washing it from time to time and leaving 
it to dry before resuming the de-varnishing until there is no 
longer any dust to be felt under the finger. Then put on 
a little essence of petroleum, applied with a linen rag the 
surface of which must not be fluffy : the picture is then 
ready to re-vamish. But if under this varnish first taken off 
there is another which does not yield to the finger, or if this 
first varnish itself does not yield to the rubbing, there would 
be every reason to suppose that we had come to an oil 
varnish or an ordinary varnish over which some kind of 
greasy matter had been passed. The picture should then be 
covered with essential oil of petroleum, and at the end of 
twenty-four hours a layer of finely powdered chalk passed 
through a sieve should be sprinkled over the oil on the 
picture laid horizontally. The object of this chalk is to 
suck up the petroleum charged with fatty matter. Twenty- 
four hours after this operation, the picture should be washed 
with lukewarm water to take off" the chalk, and afterwards 
with water slightly soaped to finish taking off the grease. 

If these means are not sufficient, it may be washed with 
acetum and water, but it should be cautiously done, and 
first tried on a small corner to see the effect. 

After each washing, the finger should always try to 
de-vamish ; if, however, the varnish persists in nqt coming 
off, we may be sure that there is an oil varnish. In this case 
it would be dangerous to try and take it completely off — ^it 
would be necessary to try alcohol or benzine, which would 
attack the painting. We must be satisfied with taking off 
merely the surface with acetum and water and a silk rag, and 
doing only a very small part at once ; or it may be done with 
egg oil mixed with the dissolving liquid of water-colour 
fixative. But if, under this varnish that we do not wish to 



178 SCIENCE OF PAINTING. 

take entirely off, the picture seems very dirty, the reason is 
that this varnish had been applied over coatings of old grease, 
which happens very often. In such a case what is to be 
done ? It must be taken off; but there is a risk of destroying 
the picture, and the best thing to do is to entrust it to the 
care of a restorer who will only do what you would do 
yourself, but who will do it more cleverly. In any case it 
is always a hazardous operation. 

To take off the colour from dried oil on a picture, either 
in part or entirely, a rag soaked in benzine, or even a scraper, 
should be used. On an unpolished panel this last means 
is good, but on sizings or paper, benzine is preferable; 
with it there is no risk of making either holes or scratches. 



Varnishing. 

Before varnishing a picture it should always be washed 
in lukewarm water, as said above, and left to dry thoroughly. 

Next the picture should be placed horizontally, and a 
first layer of essence of petroleum applied (it is indis- 
pensable that the picture to be varnished should be 
sufficiently dry) and immediately afterwards the layer of 
picture varnish, applied by passing the swallow-tail brush 
evenly from right to left and left to right, until the entire 
picture is covered with varnish, after which repeat the 
operation with the swallow-tail from top to bottom and 
bottom to top, so that the passage of the brush may have 
been everywhere crossed. At the end of an hour the 
picture may be placed upright, and two hours afterwards 
the varnish will be sufficiently dry to prevent any dust 
adhering to it. This would not be the case with essence 
varnishes, as they remain sticky sometimes for days. 

For varnishing dry weather should be preferred, and the 



APPENDIX. 179 

work always done in a room warmed at least to twenty 
degrees. As a matter of course all precaution should be 
used to ward off dust during the two hours required for 
drying. 

At all times, when from any cause a picture has been 
washed with water, it should never be left wet, but gently 
and thoroughly dried with a silk rag, to prevent the dampness 
from penetrating. 

Water-colour Fixative and the Dissolving 

Liquid. 

The object of the dissolving liquid sold with the fixative 
is to liquefy the latter when too thick. • It is also useful to 
take off the fixative when desired, and to wash the paint 
brush after the fixing. 

Method of Fixing. 

When required to fix a water colour it should be laid flat 
and one or two coatings of dissolving liquid applied with 
a flat or soft brush. The paper being thus saturated, the 
fixative will be better distributed over all the surface, and 
will penetrate better into the interior. Before the dissolving 
liquid evaporates a layer of fixative should be immediately 
applied with the same brush, going over it first one way 
and afterwards crossing it, as in varnishing. 

It should be left to dry in the air, and at the end of some 
minutes or a quarter of an hour, according to the temperature, 
the liquid having evaporated, the water-colour will be 
sufficiently fixed to allow new tints to be painted without 
melting those below; if a more complete fixing be desired 
allowing the water-colour to be washed freely in water, a 
second layer of fixative should be applied, but this time 
without the preliminary layer, of dissolving liquid. Besides, 



l8o SCIENCE OF PAINTING. 

the need of this second layer will be greater or less 
according to whether the fixative has been applied thick or 
thin, or whether the paper has been much or little sized. 

Only one bit at a time should be fixed : e.g.^ a part already 
shaded that is to be glazed at leisure, without fear of 
melting what is below it, or, on the contrary, a flat tint over 
which the shading can be done without destroying the local 
tone beneath. 



Method of Taking Off the Fixing. 

To withdraw the fixing, a layer of dissolving liquid should 
be applied, and it sHould be afterwards sponged with linen 
or blotting-p^per but not rubbed, so as not to wear off" the 
colour nor grains of paper. This operation should be 
renewed until all the fixative comes off", which may be 
ascertained by trying on a corner if the colour melts readily 
in water. This de-fixing is useful in certain cases. First, 
although it is quite easy to paint over the fixative, some- 
times it is desirable to retouch by washing in order to 
accentuate the lights, and it is necessary that the colour 
should melt. Besides, it will often happen that the fixative 
has only been used in a provisionary state as a means 
of work. 

Thus, being satisfied with a head, for instance, the back- 
ground behind it may be objected to ; therefore the head 
alone should be fixed with a small paint brush and the back- 
ground washed off" all round; but to repaint another 
background and blend the contours, the head must be 
defixed. It would be the same if on the contrary the head 
were to be washed out and the background preserved. The 
latter should then be fixed and defixed afterwards when the 
head has been washed off". 



APPENDIX. l8l 

When the fixative is used in this way there is no harm 
in putting a good deal of it, as it will afterwards be taken 
oflF. 

Sometimes, also, it is very tiresome all the time that 
a water-colour painting is being done, to reserve little white 
places like the brilliant buttons of a doublet, the ornaments 
of a sword handle, the pattern of a stujff, etc., and they are 
consequently done in Chinese white afterwards ; but this 
method is despised by genuine water-colour painters. If, 
therefore, they want to do away with these disgracing touches, 
they have only to border them off with fixative, and after- 
wards, washing it off they will find the paper white and intact 
and the touches will remain quite clear. 

In this way falling snow may be done, and the method is 
useful on many other occasions. 

Even when a water-colour is not definitely fixed after 
being finished, the fixative can still render good service 
during its execution. 

Varnished Water-colours. 

To varnish a water colour, it should first be fixed ; and 
to know if one la/er is enough a little varnish should be 
applied in a corner over the first layer. If the varnish 
does not penetiate into the paper, that is enough ; if the 
varnish penetrates, a second layer of fixative should be 
applied, and so on until the varnish no longer penetrates ; 
then the picture is to be varnished as if done in oils. 

Repair of Little Daily Accidents. 

Indented Canvas, — Wet the canvas behind the place of 
the indentation with a sponge soaked in lukewarm water and 
let it dry in a medium temperature. 



1 82 SCIENCE OF PAINTING. 

Blisters. — Soften the blister on the top with an equal 
mixture of essential oil of petroleum and essence of petro- 
leum ; next, pierce it in the middle with the point of a 
needle, and drop into this hole with a tiny syringe (like 
those used for dropping medicines in single drops) a little 
picture varnish. Press with a rag, to flatten the blister and 
at the same time to take off any superfluous varnish ; and 
afterwards have the canvas pressed under a piece of zinc 
or glass, so that the borders may be smooth and show no 
mark. A small piece of paper sized with paste should be 
put between the glass and the blister, because any varnish 
which might come out would stick to the glass, whence 
it would be awkward to get it off, whereas the paper can be 
taken off with a little lukewarm water. 

Splits, Flaws, Cracks, — When the colour is split — ^which 
often happens when the repainting is done too soon, 
especially in a dark tone over a light one — it should be 
rubbed with a little re-touching varnish and the splits filled 
up with a knife and a special mastic that we have invented 
for the purpose. (See " Mastic for Stopping Up.") 

Burst Canvas, — When canvas bursts it is customary to 
glue behind it a little piece of fine linen saturated with hot 
melted wax. This is a very bad method. In the first place 
the wax alone is not impervious to damp, and these mendings 
often rot. Next, the wax passes to the other side of the 
canvas through the crack, and as the canvas must always be 
re-painted to hide the repair, the re-paintings are not sub- 
stantial, ojl paintings (as said above) not adhering to wax. 
It would be better, before glueing the piece, to apply with a 
knife a little caseine and zinc-white sizing (see " Sizing of 
Caseine Paste and Zinc White "). This sizing would prevent 
the wax from passing through, and instead of pure melted 
wax, a mixture of half wax and half dammarine resin melted 



APPENDIX. 183 

together in a water bath should be used. This would 
diminish the chance of dampness. 

But the following is another means which we consider 
much superior. 

The picture should be placed horizontally, face down- 
wards, on a slab of marble or metal separated from the 
painting by a sheet of paper sized with essential oil of 
petroleum. The edges of the burst canvas should be 
brought well together by the help even of a flat iron if 
necessary, being careful to heat this iron only over boiling 
water. 

All the destroyed part should now be coated with caseine 
paste according to the formula. When the dampness has 
evaporated a little and the paste feels sticky under the 
finger, a sheet of paper, thin, but sized, {ue. not blotting- 
paper, so that the paste may not come through. It should 
then be well flattened with the moderately hot iron. Not 
the slightest flaw must remain. All this being dry, a new 
piece of sized paper should be applied, and a piece of fine 
canvas rather smaller than the paper, because the canvas 
would not adhere well to the other canvas. It should be 
flattened with a warm iron as before ; and everything being 
quite dry, one or more successive layers of re-touching 
varnish should be applied, letting each layer dry before 
putting on the next. The varnish should pass the borders 
of the paper and touch the old canvas, so that the edges of 
the pieces of canvas and paper are well secured and have no 
tendency to rise if scratched by anything. 

When the last layer of varnish is dry, the picture should 
be turned and placed upright. If, by chance, the paper 
sized with essential oil of petroleum which was put between 
the table and the picture should have stuck, it can be taken 
off" with a little lukewarm water. All that now remains to 



184 SCIENCE OF PAINTING. 

be done is to fill up the traces of the crack with fiUing-up 
mastic (see " Mastic for Filling Up "), or with a little zinc 
white and caseine paste. A mastic can even be made with 
caseine paste and a coloured powder of the tone desired. 

If caseine mastic be used, it should be painted over with 
painting varnish and left to dry before being re-painted. 



Panels of Unpolished Wood. 

Choose the grey or Dutch poplar, because its pores are 
open and its grain regular. The oak and mahogany have 
veins some qf which are hard and some soft, consequently 
the oil from the pigments gets more deeply absorbed in the 
soft veins than in the hard ones, and there results a want of 
smoothness in the painting which increases layer by layer 
to the end. 

The panel should be rubbed with sand-paper, and for 
the last rubbing the paper should be soaked in essential oil 
of petroleum. By this means rays are avoided, the petro- 
leum evaporates and the panel remains smooth without 
having lost either its grain or its porosity. 

The panel should be floored and kept in a dry place 
until it has shrunk— which will be about one inch in a 
hundred. Only then should the back of the panel be sized 
with a flooring composed of equal parts of thick linseed oil 
and . re-touching varnish without siccative, and, when this 
layer is dry, with another layer of picture varnish. The 
painting should be done over several layers of white lead, 
and between each layer the panel should be rubbed with 
glass paper, and painting varnish with a little siccative 
should be mixed with the colours. The object of these 
precautions is to preserve the panel from the attacks of 
dampness and worms. 



appendix.' 185 

Paste of Caseine or Cheese. 

Take of caseine of commerce, about 20 grammes* 
according to quantity of paste required. Put it to soak in 
TOO grammes of cold water for some time. Occasionally it 
requires to soak for some hours. The length of time 
depends on the condition of the caseine, which may be 
more or less hard through drying on the stove. 

Whilst stirring, add 4 grammes of ammonia by degrees, 
stirring with a spatula, or a stick of wood, glass, or horn 
but not metal. When the ammonia is incorporated with 
the mixture, leave it alone for some minutes, then stir it 
anew every ten minutes for a few seconds each time. The 
mixture thickens gradually, and the paste is ready when it 
streams from the end of the spoon in a thick syrup without 
lumps. Still stirring, add 20 grammes of glycerine. Mix 
well in stirring. The paste is then fit for use. Next day it 
is still good, but after that it loses its strength and becomes 
spoilt. 

If you have no caseine, and wish to use cheese, the. 
method is as follows : — ^White cheese (called new cheese), 
100 grammes, to which, whilst stirring, add 4 grammes of 
ammonia, and stir until the cheese becomes paste. Next 
add to it 10 grammes of glycerine. It is always preferable 
to use caseine, because, the cheese being more or less 
drained, it is impossible to judge exactly the quantity of 
caseine contained in it. The following is the method of 
obtaining the caseine from the cheese. 

Put about 100 grammes, according to quantity required, 
of white cheese into muslin, and rub it whilst thus confined 
in warm water, to extract all the watery particles, spread it 

* A gramme is about ijVth of an ounce avoirdupois. It is 15*432 
grains. 

V.P. 12 



• 



1 86 SCIENCE OF PAINTING. 

out on blotting paper and let it dry naturally on the stove, 
but at a temperature below 80 degrees. The caseine thus 
obtained should be in the proportion of about 12 gramtnes of 
caseine for 100 grammes of cheese used. 

« 

SiziNGs OF Caseine and Zinc-white Paste. 

Grind the zinc white in water in the proportion of 100 
grammes of water to 100 grammes of zinc, and mix this 
zinc white with 200 grammes of caseine paste already pre- 
pared. This paste should be kept moist with a wet linen cloth 
over the jar, so that it does not dry. The wooden panel to 
be sized, having been well smoothed with the glass paper, 
should be washed with a very clean rag and benzine, to take 
off any trace of greasy or resinous matters which would 
prevent the paste from adhering. 

When the benzine has quite evaporated, give, with a 
swallow-tail brush, a first layer of paste and white. 

Let this dry at a mild temperature. Under the influence 
of the water contained by the paste, the pores of the wood 
will open, and, rising up, will become so many little links to 
facilitate the adhesion of the following layers. 

Be careful, when this first layer is dry, not to polish or rub 
the panel, so as to leave to the wood any roughness which it 
may have acquired. 

Give a second layer. Let it dry naturally, or if wanted 
quickly, put it in the sun covered by gauze in a room not 
warmer than 25 degrees, so as not to make the panel 
crack. 

It may then be polished with glass paper or powdered 
pumice stone by means of a cork or dry rag.* 

* According to the manner in which they have been prepared, the 
zinc whites are more or less dense, and consequently more or less 
heavy. The proportions given are for the heaviest, which weigh about 






APPENDIX. 187 

If a brilliant white be desired, the third coat may be 
doubled, or even trebled ; but between each coat it must be 
left to dry, and polished. 

When the sizing is satisfactorily white, a last coat should 
be given. 

This last coat should be put on very evenly, and so as 
to require no rubbing, as that would give a disagreeable 
polish, on which the painting will not look so well. 

All the coats should be given thickly, /.^., the brush 
well charged with matter. As, according to the temperature, 
the water of the paste evaporates more or less quickly, if 
the paste get too thick, a little water should be added. 
The liquid sizing should always come uninterruptedly to 
the end of the brush when it is lifted out of the jar. 

The canvas should be stretched on a frame, and freed 
from grease with benzine. The canvas should be rubbed 
with glass paper after the first coating, because the grain 
of the canvas will always give sufficient adhesiveness, and it 
is necessary to get quickly rid of the straws, threads, and 
knots which would interfere with the following coats : 

After this first coating it is a good plan to lay on a very 
light coat of re-touching varnish, which must be allowed to 
dry thoroughly. 

800 or 900 grammes to the litre (a litre -» 1 76 pint). Those are the 
best to use, "but there are. some like snow-white which only weigh 450 
to 500 grammes per litre. Should the latter be used, it is evident that 
the weight given in the formula should change in proportion. Besides, 
these formulas can only be approximate. The nature of the wood, 
cardboard or canvas, desired to be covered, as well as the d^;ree of 
absorption that the artist desires to obtain, will compel each one to 
decide for himself the proportion most suitable. The only caution to 
be given is that each time the coating cracks and lacks suppleness, 
it contains too much white. Other whites than zinc whites may be 
used, but in that case the proportions of paste would not be the same. 



1 88 SCIENCE OF PAINTING. 

Second coat, No. 2. 

Third coat, No. 3, to be put as desired according to taste, 
to the thickness of the canvas, and to whether it be desired 
to preserve much or little grain. 



Sarcocol. 

Sarcocol, about 50 grammes, according to quantity 
desired. Treated by alcohol at 96 degrees, boiling until all 
boiled away. The distilled alcohol leaves a red residue, 
soft, looking like turpentine. This residue still contains 
much alcohol, and is dried in a stove at from 70 to 80 
degrees with much difficulty ; this is the sarcocolline, of 
which there will be 35 grammes. 

Sarcocolline is soluble in water, except a very small por- 
tion which dissolves in sulphuric ether. This watery solution, 
treated by a solution Of acetate of lead, forms a scanty 
precipitate, which is separated by filtration, and the liquid is 
treated with sulphur. To eliminate the lead, this filtered 
liquid is evaporated until dry, and thus a very slightly 
coloured production is obtained, preserving all the properties 
of sarcocolline. 

It is a glucoxide in which a resin is combined with the 
elements of a sugar. 

The alum and acetate of aluminum considerably diminish 
its solubility without rendering it completely insoluble. 
Practically, one may be satisfied to put the sarcocol in solu- 
tion in boiling alcohol. The liquor allowed to cool is filtered, 
and may be whitened by leaving it for some time in contact 
with bone black exposed to great light, filtered afresh, and 
the solution preserved in a well-corked bottle exposed to 
light. 



appendix. 189 

Gelatine. 

To render gelatine liquid {i.e. to prevent it from becoming 
a jelly when cooling), dissolve the white gelatine in its weight 
of the following liquid : — 

Half acetic acid and half water . . . . f 

Alcohol at 95 degrees ^ 

Add a little alum. 

To render the gelatine supple, a little glycerine is added, 
in different quantity according to the degree of suppleness 
desired. 

To add st^rength to the gelatine, some gum lac may be 
added to it, either in alcoholic solution, or in solution with 
water and borax. {See " Gum lac") 

Gelatine mixed with linseed oil and our picture varnish 
makes an emulsion which, ground with zinc white or white 
lead, makes sizings drying slowly but of wonderful solidity ; 
when they are to be painted over we do not advise their 
use, preferring the sizing of caseine paste to them, but in 
certain cases they may be useful. To render the gelatine 
insoluble, it should be added to a mixture composed of one 
part chromic acid to five parts of gelatine or of bichromate 
of potash and left to dry in plenty of light ; but in this 
condition the gelatine is of a yellow colour. 

If it be desired to preserve the gelatine uncoloured and 
liquid whilst rendering it insoluble, we prefer the following 
means : — 

Gelatine .... I | 

Water 10 I 

Acetic acid . . . . 3 ? '"^^*^ *°8ether in a water bath. ^ 

Acetate of aluminum 3 ) 

Add a little alcohol when all is melted. On all occasions 
when gelatine contains acetic acid, care must be given not 
to mix it with colours which are carbonates. 



190 science of painting. 

Starch or Farina Paste. 

The starch or farina should be put into cold water, and 
thoroughly mixed ; when the starch or farina no longer 
forms lumps, put it on the fire, keep stirring, and take it off 
after it reaches boiling point. Starch paste with gelatine and 
turpentine (resin) makes a very good paste, that dries quickly. 

Boil in water 

Starch 100 gr. 

Gelatine 50 

Turpentine 50 



)) 
)» 



Albumen. 

Albumen dissolves in alcohol, in water and in glycerine ; 
the paste obtained from it may be mixed with gum lac 
like gelatine and like it, becomes insoluble by acetate of 
aluminum. 

It also becomes insoluble if heated above 100 degrees, 
when still damp. 

Dextrine. 

Dextrine may be extracted from itself by the following 
means : — 

Starch needles 100 gr. 

Water . • 40 ,, 

Azotic acid 4 ,, 

Make a paste, let it dry in the open air, heat it afterwards 
in a stove for an hour at a temperature of 120 degrees. 

Gum Lac 

Brown gum lac dissol>ies in alcohol, as does also white 
gum lac, cold or in the water bath. 

Brown gum lac dissolves in ammonia cold after soaking 



APPENDIX. 191 

for five weeks ; white gum lac takes two or three months. 
Gum lac dissolves also in water by the help of borax. 

Gum lac . , 60 gr. 

Borax 10 ,, 

Distilled water 500 „ 

With very long boiling all the gum lac will dissolve. 

Afterwards filtered and evaporated to a syrupy consistency, 
this liquid is a good deal coloured. ' 

It may be whitened by means of oxygenised water in large 
quantity. 

Water Varnish. 

Varnishes may be made with water, and have the 
advantage of being easily taken off with a sponge and 
some warm water. 

Gum Varnish. 

Water saturated with borax. Senegal gum in sufficient 
quantity according to the thickness desired for the varnish, 
sugar to one-eighth the amount of the gum, all melted cold 
and passed through muslin. 

Egg Varnish. 

Beat the whites of eggs to a froth with h^f a piece of sugar 
reduced to powder for the white of each egg. Leave it to 
settle for an hour, then draw off the transparent liquid fallen 
to the bottom of the jar. This varnish does not keep, and 
must be used fresh. 

Sarcocolline Varnish. 

Make a solution of sarcocolline in alcohol at 60 degrees, 
filtered and purified, with the addition of some drops of 
glycerine. 



192 SCIENCE OF PAINTING. 

This varnish adheres very well over oil paintings, even 
when rather greasy. 

We may also use as varnish a solution of gum lac in water 
and borax ; but this once dry would not come off with water, 
— it would require alcohol. 

Inks. 

Indelible ink which may be used with steel pens : 

Aniline Black . . ... . . 4 gr. 

Alcohol 15 „ 

Gum Arabic 6 ,, 

Water 90 „ 

Add concentrated hydrochloric acid 60 drops. 

Drawing ink which may be washed. — Good Chinese ink 
has this property ; but where it cannot be procured, it may 
be made with a solution of gum lac in borax added to 
aniline black dissolved in alcohol. There is no deposit 
from this ink, but before shutting it up in a bottle, the 
alcohol should be allowed to evaporate for a day or two. 

To RENDER Wax Miscible with Water and 

Glycerine. 

Take 10 grammes of wax broken into little pieces, and 
put it on the fire in 100 grammes of water, or in 100 
grammes of glycerine. 

When the wax is melted, drop in gradually whilst stirring 
rapidly some drops of ammonia : the wax will soon become 
a liquid emulsion, and may be kept in that condition for a 
long time ; the bottle into which it is poured should be left 
uncorked for several days, so that the excess of ammonia 
may evaporate. 



APPENDIX. 193 

To Prevent Vibrations of Canvas or Paper 
Stretched for Crayons. 

A wadded mattress should be prepared and placed behind ' 
the canvas or paper, and between it and a sheet of cardboard 
fixed on the frame by screws. Mineral cotton in spun glass 
or a stuffing of asbestos may be used, as they are both in- 
destructible by fire or dampness. 

The cardboard or shelf which is to give resistance behind 
should be carefully rendered waterproof. 

Instead of the cotton, cork or any similar body might 
be used, provided the body were impervious and very light, 
and had no tendency to sink to the bottom of the frame, 
and that its pressure remained equally distributed over all 
the surface of the paper or the canvas. 

Instantaneous Sizing. 

If a sizing be desired which shall dry immediately, we 
advise it to be made as follows : — 

Water-colour fixative . . . 20 gr. 

Dammarine resin 3 ,, 

Oxide of zinc 3 „ 

The whole well mixed together and applied with a knife. 

If it be desired to apply this sizing with a brush, it may 
be liquefied with water-colour fixative dissolving liquid. 

Either water-colour or oil painting may be done over this 
sizing. 

Mastic for Filling up. 

Take powdered colour, according to the tone desired for 
the mastic, and mix it with dammarine resin, equally pul- 
verised in the following proportions : 

V, P. - 13 



194 SCIENCE OF PAINTING. 

For almost all tones, two grammes of colour and one 
of resin. For vermilion three grammes of colour and 
one of resin. For cobalt a little more resin is required. 
For lakes, there should be one-half more of resin than for 
the other colours, but they should not be used in filling up 
mastics for which opaque and adhesive colours are greatly 
preferable. 

The colour being mixed with its proportion of resin, the 
whole should be ground with water-colour fixative to a 
liquid paste, and some minutes sho\ild elapse before using 
it, to let it thicken to the consistency of mastic. Paste of 
different colours may be prepared before being wanted, and 
kept in bottles. 

Should they dry through being badly corked, they can 
easily be moistened with the water-colour fixative dissolving 
liquid. 

An equally good mastic can also be made with caseine 
paste and powdered colours. For this purpose the paste 
should be prepared a little thicker than for sizings, or more 
patience will be required until it thickens by evaporation. 
Over this paste mastic retouching or painting varnish should 
always be applied before painting. 

Manner of Rendering Paper Transparent. 

If in want of tracing paper, it can easily be prepared, by 
applying a good layer of essential oil of petroleum to any 
kind of white paper, and when that oil shall have thoroughly 
penetrated through the paper, wipe off any excess, from 
both sides, with a clean rag. 

Ink and pencil take very well on paper thus rendered 
transparent. The transparency lasts from ten to twelve 
hours according to the temperature, and the petroleum is 
completely evaporated at the end of two days. 



APPENDIX. 195 

This method is very useful in certain cases, as it saves 
the trouble of tracing and retracing several times. For 
instance, if you wish to make a pen-and-ink drawing of 
a water colour or other picture with the ordinary tracing 
paper, you have first to trace, then take off the tracing on 
the white paper, and finally outline with ink; whereas by 
preparing with petroleum the paper itself on which you are 
going to draw, you may directly at one tracing make the 
first outline with the pen. Next day your paper is no longer 
transparent, and you may continue as if the paper had never 
had any petroleum. 

Paper for taking Tracings from Oil Paintings. 

To take a tracing from an oil painting, instead of using 
paper rubbed with black lead or red chalk, or white lead or 
lamp black, the tracings on which have the disadvantage of 
disappearing as the painting proceeds, and sometimes of 
soiling the tones, it is preferable to prepare a tracing paper 
of the shade desired by rubbing oil colour mixed with 
siccative on an ordinary piece of tracing paper. In order 
that very little colour may remain, any excess should be 
well wiped off with a rag pad. 

The layer of colour being very thin and very siccative, 
this kind of paper is only serviceable for a few hours. 

Its use has great advantages : the tracings obtained from 
it when dry look as if painted with a very fine paint brush ; 
they do not run when painted with new colour — they may 
even be done over with semi-liquids or glazings ; and they 
bring no foreign body into the painting. For designs on 
stuffs, tapestries or other ornaments which have to be 
traced on backgrounds, and which require going over, this 
kind of tracing is very convenient, because by doing it with 



196 SCIENCE OF PAINTING. 

the exact tone, there is no need to repaint the tracing. 
No others should be used for tracings of perspective or 
architecture often done in ink, seeing that the ink does 
not adhere well on the painting ; and if it happen to come 
off, it brings off the top paint, and the tracings reappear, the 
tones of the under part being thus laid bare. 

Commercial Guarantee. 

All the new productions spoken of in this book may be 
found in the house of Lefranc & Co., 64 & 66, Rue de 
Turenne, Paris. 

Not only are these productions fabricated according to 
our directions and formulas, but we have only authorised 
their manufacture on condition that they should be at all 
times under our supervision. 

One can understand that an author niay from self-esteem 
desire his inventions to yield results such as he professes, 
and that he should surround himself with all possible 
guarantees, but at the same time one can understand that 
he cannot be responsible for all that may be fabricated 
and has been already fabricated with his methods more or 
less badly carried out. 

That, therefore, is the reason why the author of this book 
declares, that amongst the productions which commerce 
may present as made according to his methods, he only 
guarantees those which bear the trade mark of Lefranc 
&Co. 

With regard to colours ground specially for Water Colours 
to be fixed by Fire, colours on this principle are prepared by 
the house of Mary & Son, 26, Rue Chaptal. This house 
has the monopoly of them.