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K.F.WE

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KJF,}NE.ti 8RARY
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215 N.RA'^"^/^^ AVENUE
MADISON. W1 S3706

.M^.

MOETAES, PLASTEES, STUCCOS

Marbles, Concretes, Portland
Cements and Compositions

BEING A

Thorough and Practical Treatise

ON THE

LATEST AND MOST IMPROVED METHODS OF PREPARING

AND USING LIMES, MORTARS, CEMENTS. MASTICS AND -

COMPOSITIONS IN CONSTRUCTIVE AND DECORATIVE

WORK, INCLUDING A PRACTICAL TREATISE ON

REINFORCED CONCRETES

Prepared, Compiled and Edited By
FRED T. HODGSON, 0. A. A.

AUTHOR OF

'Treatise on Uses of The Steel Square," "Modem Carpentry,"

"Architectural Drawing Self -Taught," "Up-to-Date Hardwood

Finisher," "20th Century Bricklayer." "Modern

Estimator," "Art of Wood-Carving," Etc.

PROFUSEtiY IliliUSTRATED

With Working Drawings and Sketches of Tools,

Appliances, Ceiling Designs and Examples

of Ornamental Stucco Work

CHICAGO
FREDERICK J. DRAKE & CO., PUBLISHERS

FBEDEBICK J. DBAEE & CO.

FBEDEBICK J. DBASE & CO.

FBEDEBICE J. DBAKE & CO.

216940 ^-2^3-a>f^f^

APR -9 i9l8

SNGr

PARTI

CONCRETES, CEMENTS, PLASTERS AND STUC-

COS— THEIR USES AND METHODS

OF WORKING SAME.

INTRODUCTORY

This book, or rather compilation, is largely made up
of the very best material available on the subjects it
proposes to discuss. All the latest improvements and
methods in the mixing, proportioning and application
of plaster, mortar, stucco and cement will be described
and laid before the reader in as simple and plain a man-
ner as possible.

The art of using mortars in some shape or other, is
as old as civilization, as we find evidences of its use in
ruins that date long before historical times, not only
in the older countries of Asia and Europe, but also in
the ruins of Mexico, Central America and Peru; and
the workmen who did their part, or most of this work,
were evidently experts at the trade, for some of the
remains of their work which have come down to us
certainly show that the work was done by men who
not only had a knowledge of their trade, but that they
also possessed a fair knowledge of the peculiar qualities
of the materials they used. ** Plastering," says Miller
in his great work on Mortars, **is one of the earliest
instances of man's power of inductive reasoning, for
when men built they plastered: at first, like the birds
and the bearers, with mud; but they soon found out a
more lasting and more comfortable method, and the

8 CEMENTS AND CONCRETES

earliest efforts of civilization were directed to plaster-
ing. The inquiry into it takes us back to the dawn of ■
social life until its. origin becomes mythic and prehis- j
toric. In that dim, obscure period we cannot pene-
trate far enough to see clearly, but the most distant
glimpses we can obtain into it show us that man had
very early attained almost to perfection in compound-
ing material for plastering. In fact, so far as we yet
know, some of the earliest plastering which has re-
mained to us excels, in its scientific composition, that
which we use at the present day, telling of ages of ex-
perimental attempts. The pyramids of Egypt contain
plaster work executed at least four thousand years ago
(some antiquaries, indeed, say a much longer period),
and this, where wilful vk)lence has not disturbed it,
still exists in perfection, outvying in durability the
very rock it covers, where this is not protected by its
shield of plaster. Dr. Flinders Petrie, in his * Pyra-
mids and Temples of Gizeh,' shows us how service-
able and intellig:ent a co-operator with the painter, the
sculptor, and the architect, was the plasterer of those
early days, and that to his care and skill we owe almost
all we know of the history of these distant times and ^
their art. Indeed the plasterer's very tools do yet re-
main to us, showing that the technical processes then
were the same we now use, for there are in Dr. Petrie 's
collection hand floats which in design, shape and pur-
pose are precisely those which we use today. Even our
newest invention of canvas plaster was well known
then, and by it were made the masks which yet pre-
serve on the mummy cases the lineaments of their occu-
pants.''

The plaster used by the Egyptians for their finest
work was derived from burnt gypsum, and was there-

INTRODUCTORY 9

fore exactly the same as our ** plaster of paris." Its
base was of lime stucco, which, when used on partitions,
was laid in reeds, laced together with cords, for lath-
ing, and Mr. Miller, who has examined a fragment in
Dr. Petrie's collection, finds it practically ''three coat
work,'* about % of an inch thick, haired and finished
just as we do now.

Plaster moulds and cast slabs exist, but there does not
appear any evidence of piece moulding, nor does any
evidence of the use of modelled work in plaster exist.
That some process of indurating plaster was thus early
known is evidenced by the plaster pavement at Tel-el
Amarna, which is elaborately painted. The floor of
this work is laid on brick; the first coat is of rough
lime stucco about 1 inch thick, and the finishing coat
of well-haired plaster about Vg inch thick, very smooth
and fine, and showing evidence of trowelling, the set-
ting out lines for the painting being formed by a struck
cord before^ the surface was set, and the painting done
on fresco. It is about 60 by 20, and formed the floor
of the principal room of the harem of King Amenhotop
IV., about fourteen hundred years before Christ, that
is, between three thousand and four thousand years
ago. Long before this, plastering of fine quality
existed in Egypt, and so long as its civilization con-
tinued it aided the comfort of the dwellings of its
people and the beauty of its temples.

Nor was it merely for its beauty and comfort that
plaster work was used. Even then its sanitary value
was recognized, and the directions given in Leviticus
xiv, 42-48, which was probably written about one hun-
dred years before this date, show that the knowledge
of its antiseptic qualities was widely spread, and the
practice of it regarded as religious duty.

10 CEMENTS AND CONCRETES

Unfortunately there is no direct evidence that the
adjacent Assyrian powers of Nineveh and Babylon used
plaster work. Possibly the fine clay brought down by the
rivers of the Euphrates and the Tigris sufficed for all
their purposes. Their records are in it: their illustra-
tions on the sculptured walls of their palaces are in
stone, their painting is glazed on their bricks, and for
them there seems to have been but little need for plas-
ter work, nor do we find until the rise of Grecian art
anything relating to our subject.

Very early in Greek architecture we find the use of
plaster, and in this case a true lime stucco. of most ex-
quisite composition, thin, fine and white. Some has
been found at Mycenae, a city of Homeric date. We
know that it existed in perfection in Greece about five
hundred years before the Christian era. With this the
temples were covered externally, and internally where
they were not built of marble, and in some cases where
they were. This fine stucco was often used as a ground
on which to paint their decorative ornament, but not
infrequently left quite plain in its larger masses, and
some of it remains in very fair preservation even to
this day. The Temple of Apollo at Bassae, built of
yellow sandstone about 470 B. C, has on its columns
the remains of a fine white stucco.

Pavements of thick, hard plaster, stained, of various
colors, were common in the Greek temples. One of
these, that of the Temple of Jupiter Panhellenius at
.^gina, built about 570 B. C, is described by Cockerell
as existing in the early part of the century, in good
condition, though the temple itself was destroyed ; and
I have seen at Agrigentum plaster existing in perfect
state, though scarcely thicker than an egg-shell, on the
sheltered parts of a temple built at least three hundred

INTRODUCTORY U

/ears before our era, whilst the unprotected stone waa
weather worn and decayed. ,

What care the ancient Greeks bestowed on their
stucco may be inferred from Pliny's statement that in
the temple at Elis about 450 B. C, Panaenus, the
nephew of Phidias, used for the groundwork of his
picture ''stucco mixed with milk and saffron, and pol-
ished with spittle rubbed on by the ball of the thumb,
and," says he^ ''it still retains the odor of saffron."
Lysippus, the first of the Greek "realists" in sculpture,
was the first we hear of who took casts of the faces of
living sitters about 300 B. C, so the art of plaster cast-
ing must have advanced a good deal by that time, as he
made presents of copies to his friends. Afterwards we
read of many sculptors who sent smaller plaster models
of their works to friends. These were, however, prob-
ably carved in the plaster rather than cast.

Whether the Greeks used stucco for modelling is a
somewhat doubtful point amongst antiquarians. From
certain passages in classic writers I am induced to think
they did. Pausanius, who describes the temple at Stym-
phalus, an almost deserted and ruined city when he
visited it about 130 A. D., describes the ceiling of the
Temple of the Stymphalides, built about 400 B. C, as
being "either of stucco or carved wood," he could not
decide which, but his very doubt would imply that
stucco or wood were equally common. Now, this ceil-
ing was ornamented with panels and figures of the
harpies — omens of evil, half woman and half bird, with
outspread wings. He also mentions a statue of Bac-
chus in "colored stucco." Of course these are not defi-
nite proofs of early Greek stucco modelling, but as the
city of Stymphalus had decayed and become depopu-
lated before 200 B. C, there is certainly presumptive

12 CEMENTS AND CONCRETES

evidence of the ancient practice of the art. Again, fig-
ures of unburnt earth are mentioned in contradistinc-
tion to those of terra cotta, and sundry other allusions
to plastic work occur, which lead me to the opinion that
quite early in Greek art this mode of using plaster be-
gan. At any rate, we know that it was early introduced
into Grecia Magna — the earliest Southern Italian col-
ony of the Greeks; and as colonists invariably preserve
the customs and traditions of their fatherland even long
after they have fallen into disuse in their native home,
we can have no reasonable doubt but this art was im-
ported rather than invented by th^m. Thence it spread
to the Etruscans of Middle Italy, a cognate people to
the Southern Greeks, by whom both plain and modelled
stucco was largely used. The Etruscans, as we have
seen, were more closely allied to the Greek than the
Latiil ;race, but in the course of time these two races
amalgamated, the former bringing skill in handicraft,
the latter lust of power, and patriotic love of country
and of glory, whilst the Grecian element, which blended
harmoniously with the first of these, added a love of art.

This union, however, took long to ripen to artistic
fruitfulness. The practical Etruscan element firstly
constructed the roads and the sewers, and gave health to
Rome. The Latins added to their territory until it em-
braced half of Europe, giving wealth to Rome, and not
till the luxury and comfort thus created did the artis-
tic element of the Greek come in, giving beauty to
Rome, and the day of decorative plaster work ap-
proached its noontide glory, making Rome the attrac-
tion of the world. The absorbance of Greece as a
Roman province took place B. C. 145, and the loot of
it began, giving an enormous impetus to Roman art.
Thousands of statues were brought to Rome, and to

INTRODUCTORY 13

be deemed a connoisseur in things artistic or a patron
of the arts became the fashionable ambition. But it
was not until the century just prece^ding the Christian
era that it became especially noteworthy. Of course
there is hardly anything left to us of the very early
plaster work of Rome. The constant search for some
new thing was inimical to the old. Old structures were
pulled down to make way for new, which in their turn
gave way to newer, and until the age of Augustus we
have but little of the early work left. Strabo, who
visited Rome about this time, complains of the destruc-
tion caused by the numerous fires, and continued pull-
ing down of houses rendered necessary, for even pull-
ing down and rebuilding in order to gratify the tastie
is but voluntary ruin; and Augustus, who boasted that
*'he found Rome of brick and left it of marble/' in
replacing the brick with marble destroyed the plaster
work. How that plaster work was wrought we shall
learn more from VitruviuS, who wrote his book on archi-
tecture about 16 B. C, and dedicated it to the emperor,
**in order to explain the rules and limits of art as a
standard by which to test the merits of the buildings
he had erected or might etect."

Now, Vitruvius was a man who had travelled and
seen much. He was with Julius Caesar^ as a military
engineer in his African campaign in 46 B. C, or ten
years after Caesar's invasion of Britain. Afterwards
he became a designer of military engines, what we
should call head of the Ordnance Department, and also
a civil engineer, persuading himself that he had a
pretty taste in architecture, just as though he were an
R. B. of today. Thus he had a practical and also an
artistic training, and here is what he says on matters
connected with plaster work in Book VII, Chapter 11.

14 CEMENTS AND CONCRETES

On tempering lime^ for stucco: '*This requires that the
lime should be of the best quality, and tempered a long
time before it is wanted for use ; so that if any of it be
not burnt enough, the length of time employed in slak-
ing it may bring the whole mass to the same consist-
ency." He then advises it to be chopped with iron
hatchets, adding that *'if the iron exhibits a glutinous
substance adhering to it, it indicates the richness of the
lime, and the thorough slaking of it." For cradling
out, and for ceiling joists, he recommends **the wood
to be of cypress, olive, heart of oak, box and juniper," as
neither is liable to */rot or shrink." For lathing he speci-
fies * ' Greek reeds bruised and tied with cords made from
Spanish broom," or if these are not procurable ** marsh
reeds tied with cords." On these a coat of lime and
sand is laid, and an additional coat of sand is laid on
to it. As it sets it is then polished with chalk or marble.
This for ceilings. For plaster on wall he says: **The
first coat on the walls is to be laid on as roughly as
possible, and while -drying, the sand and coat spread
thereon. When this work has dried, a second and a
third coat is laid on. The sounder the sand and coat is,
the more durable the work will be. The coat of marble
dust then follows, and this is to be so prepared that
when used it does not stick to the trowel. Whilst the
stucco is drying, another thin coat is to be laid on : this
is to be well worked and rubbed, then still another,
finer than the last. Thus with three coats and the
same number of marble dust coats the walls will be
solid, and not liable to crack. The wall that is well
covered with plaster and stucco, when well polished,
not only shines, but reflects to the spectators the images
falling on it. The plasterers of the Greeks not only
make their stucco work hard by adhering to these direc-

INTRODUCTORY 15

tions, but when the plaster is mixed, cause it to be beat-
en with wooden staves by a great number of men, and
use it after this preparation. Hence some persons cut-
ting slabs of plaster from ancient walls use them for
tables and mirrors." (Chapter III.)

You will see by. these remarks the great care taken
through every process, and how guarded the watchful-
ness over the selection of materials, and you will also
note the retrospectiveness of Vitruvius' observation,
how he felt that the work done before the frantic haste
of his own time was the better: very much as we find
now. Time is an ingredient in all good work, and its
substitute difficult to find.

There are other ** tips'' contained in this work which
are worth extraction, as, for instance, his instructions
as how to plaster damp walls. In such case he prima-
rily suggests a cavity wall, with ventilation to insure
a thorough draught, and then plastering it with ** pot-
sherd mortar," or carefully covering the rough plaster
with pitch, which is then to be **lime whited over," to
insure **the second coat of pounded potsherds adhering
to it," when it may be finished as already described.
Further, he refers to modelled plaster work which, he
says, ** ought to be used with a regard to propriety,"
and gives certain hints for its appropriate use. Speak-
ing o:^ pavements **used in the Grecian winter rooms,
which are not only economical but useful, '^^ he advises
''the earth to be excavated about two feet, and a foun-
dation of potsherd well rammed in," and then a ** com-
position of pounded coal lime, sand and ashes is mixed
up and spread thereover, half foot in thickness, per-
fectly smooth and level. The surface then being rubbed
with stone, it has the appearance of a black surface,"
**and the people, though barefoot, do not suffer from

16 CEMENTS AND CONCRETES

cold on this sort of pavement." Now all this bespeaks
not only theoretical knowledge, but practical observa-
tion and experience, and was written nearly two thou-
sand years ago, from which you can surmise how far
advanced practical plastering had then become. This'
written evidence is almost all we have of the work of
Vitruvius' own time, for even of the time of Augustus
hardly anything remains to us, as the great fire of
Nero utterly destroyed the greater part of the city in
the year A. D. 64, and almost the only authenticated
piece of plaster work done before or during his reign
is the Tabula Iliaca, a bas-relief of the Siege of Troy,
still preserved in ihe Capitol Museum at Rome. That
this was modelled by Greek artists is proved by the fact
that its inscriptions are all in the Greek language, and
by some it is considered to be of verj'' much greater an-
tiquity. So much for the ancient history of the art
of plastering, and I trust I will be pardoned if I con-
tinue this sketch, bringing it down to a more recent
period and show in what high respect the plasterers' art
was held in the Sixteenth Century, and later. Quoting
from an old work, giving an account of the institution
of **The Worshipful Company of Plaisterers, ' ^ and mak-
ing use of the quaint language then in use we are told
that: **The Plaisterers' Company, which ranks as
forty-sixth among the eighty-nine companies, was in-
corporated by King Henry VII., on March 10, 1501, to
search, and try, and make, and exercise due search as
well in, upon, and of all manner of stuff touching and
concerning the Art and Mystery of Pargettors, com-
monly called Plaisterers, and upon all work and work-
men in the said art or mystery, so that the said work
mighl be just, true, and lawful, without any deceit or
fraud whatsoever against the City of London or suburbs

INTKODUCTORY IT

thereof. The Charter gave power to establish the Com-
pany as the Guild or Fraternity in honour of the
Blessed Virgin Mary, of men of the Mystery or Art of
Pargettors in the City of London, commonly called
Plaisterers, to be increased and augmented when neces-
sary, and to be governed by a Mastar and two War-
dens, to be elected annually. The Master and Wardens
and brotherhood were to b^ a Fody corporate, with per-
petual succession and a common seal, and they were
empowered to purchase and enjoy in fee and perpet-
uity lands and other possessions in the City, suburbs
and elsewhere. And the charter empowered the said
Master and Wardens to sue and be sued as **The Mas-
ter and Wardens of the Guild or Fraternity of the
Blessed Mary of Pargettors, commonly called Plaister-
ers, London.''

TBS OLD COAT 07 ASM8#

The Company under tKe powers to make examiner
tions, appears to have inflicted fines on offending par-
ties for using bad materials, and for bad workmanship.
Search days appear to have been annually appointed
up to 1832, but not since, and the Company has not
exercised any control over Plaisterers' work for many
years.

18 CEMENTS AND CONCRETES

Another charter was granted by Queen Elizabeth in
1559, but it has been lost, and there is no record of
the contents. The Queen granted a new charter in
1597, which confirmed the privileges of the Company,
and extended the authority of the Master and Wardeps'
to and over all persons exercising the art of plaisterers,
as well English as aliens and denizens inhabiting and
exercising the said art within the City and suburbs and
liberties, or within two miles of the City.

Charles II., by a charter dated June 19, 1679, eon-
firmed the privileges granted by the previous charters.
Having in view the rebuilding of the City, he forbade
any person to carry on simultaneously the trades of
a mason, bricklayer or plaisterer, or to exercise or carry
on the art of a plaisterer without having been appren-.
tieed seven years to the mystery. The jurisdiction of
the Company waa extended to three miles' distance
from the City.

There were two orders made by the Court of Alder-
men (eiempMed undtor tia mayolratty Be&l, April 1^

INTRODUCTORY 19

1585) for settling matters in dispute between the tllera
and bricklayers and the plaisterers as to interfering in ■
ea«h other's tradea. The observance of these orders
was enforced by an order of the Privy Council dated
June 1, 1613, and a general writ or precept issue to the
same effect on August 13, 1613.

Indian Ckntbe-Piece.

There was also an order of the Cour' of Aldermen
(29 Elizabeth, February 14, 1586-7; relating to the
number of apprentices to be kept by members.

An act of Common Council was passed, under date
of 18 James I., October 5, 1620.

An act of Common Council {6 William and Mary,
October 19, 1694} was also passed to compel all persons
using the trade of plaisterer in the City of London, or

20 CEMENTS AND CONCEETES

the liberties thereof, to become free of the 'Company
tinder penalty to be recovered as therein mentioned. In
the East the Art of ornamental plastering was well
known and almost universally practiced before Mahom-
et established a new order of things, and the enriched
plaster work of India, Persia and other Eastern Em-
pires are evidences of the high character of the work-
manship of the Oriental workers in plaster. The
Arabian and Moor brought back the Art of the Western
World in the early part of the thirteenth century,
and it is to them we owe the splendid plaster work of
the Alhambra and other work still in existence in Spain.
In the Mosque at Medina, built in 622, are still to be
seen some fine specimens of old plaster work that was
wrought on the building at the time of its completion.
The Mosque of Ibu-tubun, Cairo, Egypt, which was fin-
ished in A. D. 878, abounds with beautiful plaster work.
It contains a number of arches and arcades, the capi-
tals of which, like the rest of the building, are enriched
with plaster buds and flowers made in elaborate de-
signs. Even in Damascus, thai old and far-off City
indulged in ornamental plaster-work when the people
of Western Europe were cutting one another's throats
for political ascendency. We illustrate a few examples
of old work taken from existing specimens. These will
to some extent, give an idea of what the old plasterers
could do. See illustrations attached.

During the middle ages in Europe plastering and
stucco existed only as a craft, and its highest function
was to prepare a surface to be painted on. Sometimes
it was used as an external protection from the weather
but rarely was it employed for direct ornament. Some-
times small ornaments were carved in plaster of Paris,
but it played no important part in decorative Art,

INTRODUCTORY 21

excepting perhaps, as gesso, th&ugb this belonged rather
to the painter than the plasterer. Nor was it until the
eommenceinent of the Renaissance in Italy that it
showed any symptoms of revival.

'AUIESQUI FHOU THR ClUT MOSiJUI. DAHASCVI.

With the commencement of the fifteenth century old
learning and old- arts began to be studied, the discovery
of the art of printing and the consequent multiplication
of the copies of the lore heretofore looked ■ up in old
manuscripts gave invention and progress new life,

22 CEMENTS AND CONCRETES

which has lasted until the present day. Italy has al-
ways been the nursing mother of plasterers, and in Mr.
G. T, EobiuBon'a "Glimpse of the History of the Art
and Craft," he has shown something of her great and
glorious past, and how she sent her sons over almost
all Europe to raise the art and status of this craft

Persian Centre- Piece.

Even during tlie depressing times of her history she
religiously preserved its ancient traditions and pro-
cesses, and in almost all her towns there was some one
or two plasterers to whom was confided the restoration,
the repair and the conservation of its frescoes or its
stuceos. The art dwindled, but it survived. So late
as 1851 an English architect, when alietching in the

INTRODUCTORY 23

•

Campo Santo at Pisa, found a plasterer busy in lov-
ingly repairing portions of its old plaster work, which
time and neglect had treated badly, and to whom he
applied himself to learn the nature of the lime he used.
So soft and free from caustic qualities was it that the
painter could work on it in true fresco painting a few
days or hours after it was repaired, and the modeller
used it like clay. But until the very day the architect
was leaving no definite information could he extract.
At last, at a farewell dinner, when a bottle of wine
had softened the way to the old man's heart, the plas-
terer exclaimed, '*And now, signor, I will show you
my secret!" And immediately rising from the table,
the two went off into the back streets of the town, when,
taking a key from his pocket, the old man unlocked a
door, and the two descended into a large vaulted base-
ment, the remnant of an old palace. There amongst
the planks and barrows, the architect dimly saw a row
of large vats or barrels. Going to one of them, the old
man tapped it with his key; it gave a hollow sound
until the key nearly reached the bottom. ** There, sig-
nor! there is my grandfather! he is nearly done for.''
Proceeding to the next, he repeated the action, saying:
''There, signor! there is my father! there is half of him
left." The next barrel was nearly full. ** That's me!
exclaimed he; and at the last barrel he chuckled at
finding it more than half full: '* That's for the little
ones, signor!" Astonished at this barely understood
explanation, the architect learned that it was the cus-
tom of the old plasterers, whose trade descended from
father to son for many successive generations, to care-
fully preserve any fine white lime produced by burning
fragments of pure statuary, and to each fill a barrel for
his successors. This they turned over from time to

24 CEMENTS AND CONCEETES

time, and let it ain — slake in the moist air of the vault,
and so provide pure old lime for the future by which
to preserve and repair the old works they venerated.
After-inquiries showed that this was a common prae-

PORTION OF A CeiLINC KROM TEHERAN, PERSIA-

tice in many an old town, and thus the value of old
air-slaked lime, such as had been written about eighteen
hundred years before, was preserved as a secret of the
trade in Italy, whilst the rest of Europe was advocating

INTKODUCTORY 25

the exclusive use of newly burnt and hot slaked lime.
"Was there in the early part, indeed even in the middle

of the present century, any plaster image seller who was
not an Italian f Indeed, at this present time, almost

26 CEMENTS AND CONCRETES

all the "formatore" or piece moulders for the majority
of the sculptors of Europe are of Italian nationality or
descent, and chiefly by these has the national craft been
maintained.

When after the long European wars of the eighteenth
and the commencement of the nineteenth century Italy
had rest and power to "make itself" (faro de se), the
first revival of Us industry was felt by her plasterers,
aqd as there was then, as now, more workmen than

VuntK FdEiB IN ^[Oil>uE or Sulias Hamk. Fou«teentii CiXTumr.

work, they emigrated to the neighboring conntries ; and
the major part of the plasterers along the Eevieda, in
the southern provinces of Germany and Austria, are
Italians who go off with and return with the swallows,
to earn that wage the poverty of their own country
cannot afford them. "With this brief historical sum-
mary I conclude the Introductory notice, and will now
pass on to the more practical domain of the Plasterers'
Art.

MATERIALS.

UMES^ CEMENTS^ MOBTABS^ SAND^ PLASTERS AND LATHa

LIMES.

The Lime Principally Used for internal plastering
is that calcined from carbonate of lime, in which the
impurities do not exceed 6 per cent., and is known as
fat lime, pure lime or rich lime. It is unfit for any
purpose where strength is required, or in situations
where it is exposed to the weather, as it has no setting
power, and is easily dissolved by wet.

Hydraulic Limes are those which, in order to set, do
not require any outside influences, their own chemical
composition of lime and silica, when burnt, being suf-
ficient for the purpose. The name is given for fheir
capability of setting and hardening under water. Hy-
draulic limes are obtained mostly from the lias.

Good Hydraulic Limes are obtained from many
places in the United States and Canada, the best
known is **The Rosendale Hydraulic Cement."

Artificial Hydraulic Limes may be made by mixing
a sufficient quantity of clay with pure lime to obtain
a composition like that of a good natural hydraulic
limestone. The lime^ if soft, may be mixed with the
clay and burnt raw, or, as is more usual, may be burnt,
slaked, ground, and then mixed with the clay and re-
burnt.

The Purer the Lime the quicker will it slake. Great
care should be taken that the lime is properly burnt
or otherwise it will not slake properly, and will prob-
ably **blow" in the work.

28 CEMENTS AND CONCRETES

The Perfect Slaking of the burnt lime before being
'ised is very important, as it will slake eventually, and
cause blisters in the work. In order to effect thorough
slaking, the lime should be ''run" as soon as the build-
ing is commenced. It should not be used unless it has
been slaked at least three weeks.

A Bushel of Lime requires in slaking about a gallon
and a half of water.

lAme which Slakes Quickly and with great heat is
generally considered to be the best for plasterers' work.

When Lime ^^FalW in dry weather without any
sufficient apparent moisture, it is considered to foretell
rain.

The Lime Should Be Run in couch on the site, where
it can be seen by the architect. Care should be taken
that as much lime is run as is required for the whole
of the building.

The Plasterer^ partly, perhaps, to avoid the money
outlay, and partly to avoid the necessity of having to
cart away any lime, has a tendency to run an insuf-
ficient quantity of lime. The result of this is that he,
commencing at the top, the usually less important part
oi the building, has used up his lime by the time he
has reached the principal rooms on the ground floor,
and has to have recourse to possibly insufficiently sea-
soned lime, with an unfortunate effect on the work, as
stated above.

SAND.

The Functions of Sand as used in plaster are (1) the
production of regular shrinkage and the prevention of
excessive shrinkage, otherwise cracking is the result;
(2) to form channels for the crystallization.

MATERIALS 2?

Sand should be clean, sharp, and hard. The size ot
the grains does not influence the strength of the mortar,
but, of course, the finer the plaster is required to be
the finer must the; sand be. Pine sand is best for hy-
draulic lime and coarse for fat limes, coarse stuff and
Portland cement for floating. Uniformity of size is
not desirable.

The Proportion of Sand to Lime will •vary consider-
ably, according to circumstances, and is difficult to de-
termine. One part of lime to two parts of sand is a
usual mixture.

Sand is Cheaper than Litne, and it must be remem-
bered that this is an inducement to use too large a pro-
portion of sand in order to cheapen the plaster.

Sand is Obtained from rivers, pits, or the sea. Sea
sand, or that from tidal rivers, should be avoided, as
the salt never dries, and will come out on the surface
sooner or later, discoloring the wall papers, paint, etc.^
and keeping the walls damp.

River Samd is often used, but it is jiot to be recom-
mended, because the sharpness , of the grains is worn
off by the action of the running water. It is easily
obtained, however, and the light color of much river
sand causes it to be used in internal work with the
white cements.

Pit Sand is the best. It sometimes contains loam or
clay, which should be carefuUy washed out.

All Sand for High-Class Plastering is best washed.

HAm. '

Hair is used in plaster in order to bind it together.

Oood Hair should be long, curled, strong, and clean.
Ox or cow hair is most generally used, and there are
three qualities.

30 CEMENTS AND CONCRETES

It Should Be Well Separated before being mixed
with the plaster, and care should be taken in the mix-
ing that the hairs are not broken.

CEMENTS.

Portland Cement, with a large proportion of sand,
as much as 90 per cent., is useful for internal work;
it may be used as a backing for a thin floating of the
white cements.

The Heavier and Slower in Setting cements are gen-
erally the stronger; but in such plasterer's work as
rendering walls the quicker setting cements may be used,
without disadvantage.

Roma/n Cement is a *' natural" cement. It is liable
to eflSoresce on the surface, but is useful where quick
setting with expansion is required, as in underpinning
or repairs, without any great ultimate strength.

Other ^^ Natural Cements'' very similar to Roman
are Medina, Rosendale, Windsor, etc., and are also use-
ful where quick setting is required.

The Use of the Natural Cements is much restricted
at the present time as compared with artificial cements,
such as Portland.

Parian Cement is valuable for internal work, by rea-
son of its hardness, nonporosity, and quick setting
properties. It is hence useful in cases where the walls,
mouldings, etc., have to stand rough usage. It is also
washable. This cement will not admit of being re-
worked.

Keene's Cement is one of the most useful of the
artificial cements. It is harder than the other kinds
made from plaster of Paris, and is much used for pilas-
ters, columns, etc.^ as it sets quickly and can be ix)l-
ished, and takes paint excellently.

MATERIALS 31

Martinis Cement is much the same as Keene's, and
used principally for dadoes, etc. In proportion to its
bulk it covers a large proportion of surface. It can
be painted, etc., as Keene's.

Robinson^s Cement has many advantages, among
which are its fire-resisting qualities and suitability for
use on concrete. It is also cheaper than other like
cements.

Adammit is another white cement, which is useful for
work where hardness, facility of application, quick dry-
ing, and a fine surface are required.

The Above Cements have plaster of Paris (calcined
gypsum) for their base, and are only adapted for in-
ternal uses, to which they are eminently suited. They
can all be brought to a good surface, and can be painted
almost at once.

Selenitic Cement is based on the property which sul-
phate of lime as plaster of Paris, when added to lime
possessing hydraulic properties, has of causing its more
rapid setting. It also increases the proportion of sand
which it will bear. It is useful in plastering as a back-
ing for the white cements, such as Parian.

PLASTER OP PARIS.

Plaster of Paris is made by the gentle calcination of
gyi)sum, previously ground. It is known in the plas-
tering trade as plaster.

The Principal Use of Plaster of Paris is in mixing
with ordinary putty in order to produce greater rapid-
ity in setting, but the fast setting plasters of Paris are
not, of course, the best for working with, nor do they
become as hard as the slower setting.

The Proportion of Plaster of Paris to ordinary lime
putty varies greatly from about 1 in 4 to 1 in 20, de-

32 CEMENTS AND CONCRETES

pending on circumstances, such as the state of the
weather, the speed with which the work has to be fin-
ished, etc. It is also used largely for cast ornaments,
in cornices, etc., and, by reason of its quick setting and
expansion when setting, for stopping holes, etc.

LATHS.

' Pine, Cedar and Metal are used for laths for mod-
ern work; only the best quality should be used.

Oak Laths and Cypress formerly used, are very liable
to warp.

The Defects to Be Avoided in Laths are sap, knots,
crookedness, and undue smoothness. The sap decays;
the knots weaken the laths; the crookedness interferes
with the even laying on of the stuff; and the undue
smoothness does not give sufficient hold for the plaster
on the lath.

' Biven Laths, split from the log along its fibres, are
stronger than sawn laths, as in the latter process the
fibres of the wood are often cut through.

Laths May Be Obtained in Three Sizes, namely:
*' Single'' (average 1-8 in. to 3-16 in. thick), ''lath and
half (average ^ in. thick) and ''double" (% in. to
% in. thick).

The Thicker Laths should be used in the ceilings, be-
cause of the strain upon them, and the thinner in ver-
tical partitions, etc., where there is but little strain.
Where walls and partitions have to stand rough usage
the thicker laths are necessary.

Laths Are Usually Spaced with about % in. between
them for key.

A Bunch of Laths usually contains a hundred pieces,
and such a bunch nailed, with butt joints, cover about

MATERIALS 33

4% yds. super., and requires about 500 nails if nailed
to joists 1. ft. from center to center.

The Lengths of Laths vary from 3 ft. to 4 ft., the
latter the usual length.

Laths Are Best Nailed so as to Break Joint entirely,
as for various reasons there is a tendency to crack along
the line of the joints if nailed with the butt ends in a
row. This may be obviated by using 3 ft. and 4 ft. laths
together. Ceilings are much stronger if so nailed.
Laths, however, are usually nailed in bays, about 4 ft.
or 5 ft. deep.

Every Lath should be nailed at each end, and wher-
ever it crosses a joist or stud.

Lap Joints at the end of laths, which are often made
in order to save nails, should not be allowed as this
leaves only ^4 iii- fo^* the thickness of plaster. Butt
joints should always be made.

Joists, etc, which are thicker than 2 in. should have
small fillets nailed on their under side or be counter-
lathed, so that the timber surface of attachment be re-
duced to a minimum and the key be not interfered with.

Walls which are liable to damp are sometimes bat-
tened or strapped.

Metal Lathing is now extensively used for its fire-
proof qualities and freedom from rot or harboring of
vermin.

Lathing Nails are usually of iron — galvanized, cut,
wire, or cast; where oak laths are used, the nails
should be galvanized or wrought. Galvanized nails
should also be used with white cement work. Zinc
nails, which are expensive, are used in very good work,
because of the possibility of the discoloration of the
plaster by the rusting of iron nails.

34 CEMENTS AND CONCRETES

The Length of Lathing nails depends on the thiek-
n6ss of the laths, % in. long nails being used for shin-
gle laths, 1 in. nails for lath and half laths, and 1^ in.
nails for double laths.

MEMORANDA.

One Yard Rendering requires 1-3 cu. ft. lime, y^ cu.
ft. sand, 2^ oz. hair, and 1% gal. water. One yard
render and set requires % cu. ft. lime, ^ cu. ft. sand,
3 oz. hair, and 2 gal. water.

One yard render, 2 coats and set, requires 3-5 cu. ft.
lime, 2-3 cu. ft. sand, 3 oz. hair, and 2^ gal. water.

One yard render and float requires ^ cu. ft. lime,
% cu. ft. sand, 2^^ oz. hair, and 2% gal. water.

One yard render, float and set, requires 3-5 cu. ft
lime,. % ft. sand, 3^ oz. hair, and 2% gal. water.

Two bushels of gray lime, or 3 of blue lias lime, or
3 of Roman cement, or 2 of Portland cement, or 14 lbs.
plaster of Paris, equal one bag.

1 lb. hair is allowed to 2 cu. ft. of coarse stuff fop
good work, and 3 cu. ft. for common work.

100 yd. super, of lime whiting, if once done requires
1^ cu. ft. of lime; and if twice done, 2 cu. ft. of lime.

WORKMANSHIP.

EXTERNAL WORK.

Portland Cement is unquestionably the best material
for external plastering. For weather resisting proper-
tieSy strength, and capacity for moulding and painting,
it is unequalled.

The Cement for Rendering requires to be mixed with
sand in the proportion of about 1 of cement to 4 of
sand, but for projecting cornices, etc., the proportion
of sand should be only about half this, as, of course, the
addition of sand .decreases the adhesive power of the
cement. The fining coat is mixed in the proportions of
about 2 to 1.

External Facades in Portland Cement are usually
laid in two coats ; the first coat, known as the rendering
or floating coat, is worked to screeds, and is from i^
in. to % in. thick. This coat must be carefully cleared
and well wetted for the second coat, which is known
as the finishing or fining coat, which is about 3-16 in.
thick, and is worked with a hand float.

The Key for External Plastering on brick work may
be obtained either by building the walls roughly with
the mortar projecting or by raking the joints at least
% in. Stone work should be hacked.

The Surface Must Be Well Wetted, or the wall will
absorb the water from the rendering coat.

There is a Te^ndency to Mix Fat Lime with Portland
cement in order to make it work more freely, but this
should not be allowed.

36 CEMENTS AND CONCRETES

Stucco is the term which is loosely applied to all
kinds of external plastering, whether of lime or cement.
An enormous amount of ''stucco" was done at the end
of the eighteenth century and the beginning of the
nineteenth, but is now out of fashion, except for coun-
try and suburban residences. The term is also applied
to some forms of internal plastering. The principal
varieties of stucco are common, rough, bastard, and
trowelled, but cement has largely superseded them.

Common Stucco was principally employed for ex-
terior work, and was composed of 1 part hydraulic lime
and 3 parts sand. The surface of the wall should be
rough and wet as for Portland cement rendering.

Bough' Stucco was used on a floated ground in po-
sitions where it was desired to imitate stone. It was
worked with a hand float covered with a material such
tis rough cloth, in order to raise the sand and produce
a stone-like appearance. Cement is now used for the
same purpose.

Bastard Stucco and Trowelled Stucco were chiefly
adapted for painted internal work, and each is laid on
the second coat as a finish; the first and second coats
being as for ordinary three-coat work.

Trowelled Stucco consists of 1 part sand to 2 parts
fine stuflp. It is worked with the hand float till a very
fine smooth surface is produced.

Bastard Stucco contains a little hair and has not so
much labor expended upon it.

Sgraffito is the name given to ornament which is
scratched on plaster work. Patterns may be obtained
by laying differently colored coats (usually two or
three) on ordinary roughened Portland cement ren-
dering, and removing portions of each coat in the form
of a pattern.

WORKMANSHIP 3T

The Design for the Sgraffito is applied in a cartoon
and pricked and pounced on the work in the usual way. >
If more^ colors are required than the coats provide, the
background may be washed and a combination of
sgraffito and fresco used. The cutting should be deep
enough to give a sharp appearance, but not too deep
tc hold dirt and wet.

Rough Cast, also known as pebble dashing, is the
coarsest kind of external plastering. It is very durable
if properly mixed. Its use in this country dates back
to very early times. The wall is first plastered, and
gravel, shingle, or other materials such as spar, broken
bricks and glass bottles, broken pottery, etc., are thrown
or dashed at it while it is soft. If the gravel is mixed
and laid with the plaster there is a tendency in laying
for it to tear the plaster away from the wall, and as
the gravel is covered with plaster its appearance is not
so good. The lime for rough cast should be weather
resisting, and is generally used hot.

Depeter is a form of rough cast on which the gravel
is pressed in by the hand. Ornamental patterns in
color may be worked in it. Effective but simple deco-
rations for external plaster may be made in various
ways. Patterns, such as sunflowers, etc., may be in-
cised in it, and^a very effective decoration has been
obtained by merely tapping the plaster with a scratch
six or seven times alternately in a diaper pattern. In
half-timber work the plaster is much more' pleasing if
carefully laid with a carelessly unlevel surface, and, of
course, set back from the timber face about % in.

INTERNAL WORK.

Lime Plastering is compounded of lime, sand, hair,
and water. The proportions of these materials vary

38 CEMENTS AND CONCRETES

according to their nature and the position of the plas-
ter. For successful wark good materials and skillful
mixing are essential. It is applied in one, two, or three
coats, and by the number of these the plaster is named.

The Thinner the Coats of plaster are the better, as
the plaster has a better chance of drying and harden-
ing.

One-Coat ^ Work, necessarily the commonest and
cheapest, is limited to very inferior buildings, such as
outhouses and places where it will not be seen, as be-
hind skirtings. One-coat work on laths is specified as
'*lath and lay," or **lath anfl plaster," and on walk
simply as ''render."

Two-Coat Work is that usually employed in inferior
work, such as factories, warehouses, etc., but it is also
used for the least important rooms in better class build-
ings. Common setting for walls and ceilings is gener-
ally used for this class of work. Two-coat work on
laths is specified as **lath, lay, and set," or **lath, plas-
ter, and set," and on walls as ** render, and set."

Three-Coat Work is that used in all good buildings,
and forms a most satisfactory wall finish, when well
done. Three-coat work on laths is specified as *'lath,
lay, float, and set," or'**l^th, plaster, float, and set,"
and on walls as ''render, float, and srt."

The Processes in Plastering ordinary three-coat work
are as follows:

For the First Coat a layer of well-haired coarse stuff
known as pricking-up is laid to a thickness of about
i^ in. This should be laid diagonally and with each
trowelful overlapping. If on laths it should be soft
enough to be well worked through them to form a key.
The surface is then scratched with a lath to fol'm a
key for the next coat in lines about 4 in. apart. It is

WORKMANSHIP 39

ready for the second coat when too hard to receive an
impression from ordinary pressure.

The Coarse Stuff used in the first coat is mortar com-
posed of sand and lime, usually in the proportions of 2
to 1, with plenty of hair, so that when a trowelful is
taken up it holds well together and does not drop.

The Second Coat known as floating, is next laid.
Pour processes are involved in laying the second coat,
namely: Running the screeds, filling in the spaces,
scouring and keying the surface. The scouring is done
Ti\4th a hand float, the surface being sprinkled by a
brush during the process. The keying consists in lining
the scoured surface with a broom or nail float to form
an adhesive surface for the finishing coat.

The Floating is of finer quality than the coarse stuff,
it does not contain as much, hair, and is used in a softer
state.

The Third Coat is the finishing coat, and is known
as the setting coat. Great care must be taken in laying
this coat in order to obtain uniformity of surface, color,
smoothness, and hardness. The second coat should be
uniformly keyed, clean and damp before the third is
laid. The processes involved are laying, scouring, trow-
elling, and brushing.

Fine Stuff, which should be used for the finishing
coat if the walls are to be papered, consists of pure
lime, slaked and then saturated till semi-fluid, and al-
lowed to stand till the water has evaporated and it
forms a paste. It may then be thoroughly mixed with
fine sand in the proportion of 3 parts of sand to 1 part
of fine stuflf.

Plasterers' Putty is much like fine stuff, but is care-
fully sieved.

40 CEMENTS AND CONCRETES

.'. Gauged Stuff is plasterers' putty an(J plaster of
Paris in the proportion of three or four to one. If too
much plaster is used it cracks in setting. It is largely
used in cornices, and also where the second coat is not
allowed time to dry, and the work has to be done in a
liurr3^ As it sets rapidly, it must be mixed in small
quantities.

The White Cements (such as Parian, etc.), of which
plaster of Paris is the base, are usually laid in two
coats; the first, of cement and sand, is about % in. to
% in. thick, and the second of the cement neat.

Cracks in Plaster Work are caused,, apart from the
natural settlement of the building and the use of in-
ferior materials and workmanship, by the too fast dry-
ing of the work, the laying of the plaster on walls of
too great suction, by laying one coat on another before
the lower one has properly set, and by the use of too
little sand.

Joist Lines on Ceilings are very unsightly, and are
caused by the filtration of dust through the intervening
spaces. They may be prevented by using a good thick-
ness of plaster, and working it well, that it may be hard
and nonabsorbent and as the dust cojnes from the top
and filters through, by protecting the upper side of the
plaster.

, Pugging consists in laying a quantity of plaster be-
tween the joists of a floor or between the studding of
a partition for the purpose of preventing the passage
of sounds or odors. In the first case, which is the more
common, the plaster is laid on thin, rough boards fixed
^0 battons on the sides of the joists; in the second case,
which is called **counterlathing'' in some parts of the
country, by plastering on laths nailed between the par-
tition studs.

WORKMANSHIP 41

Pugging Should Not Be Used Too Wet. There are
three objections to this — ^the first that it takes a very-
long and inconvenient time in drying; and secondly,
that the water is liable to be absorbed by the wood,
and to cause it to rot; and thirdly, it is liable to crack
in the drying. For this last reason it should always be
laid in two coats.

The Battons should all be nailed at an equal depth
from the tops of the joists, and the plaster should be
of an equal thickness throughout, which is obtained by
drawing a trammel along the joists.

Mineral Wool is far more sanitary than ordinary
pugging, has considerable sound and fire resisting qual-
ities, it does not absorb moisture and so rot the laths
and timbers, is a preventive of vermin, and is light in
weight.

Lime Whiting or Whitewash which is lime dissolved
in water, is a useful and sanitary covering for the
walls of cellars and outhouses.

If Lime-Whited WaMs Have to Be Plastered, the wall
should be first carefully picked, as if the lime is left on,
the plaster is liable to scale.

Fibrous Plaster is coDjposed of plaster, canvas, wood,
etc. It is light and dry and can be quickly fixed.

Ornamental Plaster ceilings may be either modelled
throughout in situ, or cast in pieces, or formed by work-
ing the ornament on a previously formed flat ceiling.
The first method is the more costly, but more feeling
is thereby obtained.

SPECIFICATION CLAUSES.

MATERIALS.

1. The sand for plastering is to be fresh-water river,
or pit sand, and free from earthy, loamy, or saline
material, to be well screened, and to be washed if re-
quired.

2. The laths to be straight-riven or saron pine of the
strength known as lath and half, well nailed with lin.
oxidized lath nails, properly spaced for key, and with
butt-headed joints, double nailed, and breaking joint
in 3 ft. widths.

The lathing to be ** Expanded metal,'* No. — gauge.

3. The lime for coarse stuff to be approved well-
bumt grey-stone lime, to be run at least one month
before- being required for use, to be kept clean, and
well mixed as required with two parts sand and one
part lime.

4. The coarse stuff for ceilings, lath partitions, and
elsewhere where directed to have 1 lb. of good, long
curled cowhair, free from grease, leading, or other im-
purities, well beaten in, and incorporated with every
3 cu. ft. of coarse stuff.

5. Approved lime, free from lumps, flares, or core,
is to be used for setting, putty, etc., and is to be run
at least one month before, being required for use.

6. The Portland cement is to be of the best quality
and description for plastering purposes, from an ap-
proved manufacturer, and must on no account be used

fresh, but be spread out to cool for at least weeks

in a dry shed or room.

SPECIFICATION CLAUSES 43

All suitable cement and all other materials required
in plastering are to be of the best of their respective
kinds and descriptions.

7. Provide all plasterers' plant, necessary scaffold-
ings, tools, moulds, running rules, straight edges, tem-
plates, etc., of every kind and description necessary for
the proper execution of the work.

WC«KMANSHIP.

8. Lath, plaster, float, and set all wood joist ceil-
ings, soffits, and stud partitions, and finish partitions to
line in trowelled stucco.

The concrete ceilings and soffits are to be well hacked
for key and floated and set in gauged stuff, and the
concrete partitions are to be floated and set.

Do all dubbing out where required to concrete ceil-
ings, soffits, and partitions in gauged stuff.

The concrete soffits of strong rooms to be finished
with one coat of putty gauged with plaster only.

9. Cover all chases containing pipes, etc., with heavy
wire lathing suitable for plastering on, securing the
same in a thorough manner. The wire lathing to be
wetted in lime water before being put on.

10. Bender, float, and set all walls where not other-
wise described. The walls to to be finished in

trowelled stucco.

11. All cornices and moulded work throughout to
be run clean and accurately to the sections given.

All mitres and returns to be truly worked, and all
enrichments and modelling to be to architect's ap-
proval, and strictly in accordance with the models and
instructions given.

Bun moulded plaster cornices .... girt to ... . rooms,

44 CEMENTS AND CONCRETES'

with all mitres, returned, ^topped, and mitred ends,
etc., Ba required. j| .

The cornices to .... are ta be i^n in fibrous plas-
ter, fitted and ixed with proper oxidized nails, and
made good to. ^

12. All narrow reveals, splays, and returns to be
finished in suitable cement on a- Portland cement back-
ing.

Run strong cement angles and arrises on Portland
cement backing to all projecting angles except the fol-
lowing, which are to be moulded, viz. :

Run rounded angles to of 3 in. girt in strong

cement as before.

Run avolo moulded angles 3 in. girt with 2 in. wings

to opening, finished with moulded stops and short

lengths of angle and arris to detail, all in best cement.
• AH exposed surfaces of concrete lintels and girder
casings are to be finished in white cement internally
and Portland cement externally, kept flush with faces
of brickwork; all with arrises and an^gles excepting
those otherwise described.

13. Run Portland cem^it flush skirting 9 in. high
to basement, where plastered, with flush head to top and
trowelled face.

The skirting to ...... to be 12 in. high and 1 in.

projection, sunk and twice moulded in white on Port-
land cement backing.

Float off the concrete floors of .... in Portland ce-
ment to the required level to receive mosaic and the
pavings.

14. Run all necessary quirks, spla>s, arrises, etc.,
and make good to all mantelpieces; cut away for and
make good after all other trades, and cut out and make

SPECIFICATION CLAUSES 4?

good all cracks, blisters, and other defects, and leave
plaster work perfect at completion.

15. Ding walls where shown on plans with a coat of
Portland cement 1 part, sand 2 parts, pea-grit 1 part,
and ground chalk 1 part. Finish walls where shown
with a rough coat of Portland cement 1 part and sand
3 parts, and rough cast with fine pea-grit.

16. Stop apd twice liine white soffits and walls of . .

17. Twice distemper white all ceilings, soffits, and
cornices, and twice distemper to approved tints the
walls of all rooms.

-^i

PREPARATION OF BILL OF QUANTITIES.

f ■ ■ • ' .

MATERIALS.

• • Materiah aiid Plant , etc. — 1 to 7. These items ap-
-pear in the heading under Specification clauses. .

WORKMANSHIP. .

. ^ kJ w

Ceilings, Partitions, and Walls. — 8 and 10. These
are all billed at per yd. super, including lathing where
required, also hacking concrete and any dubbing in the
latter, stating the thickness. Keep all plaster work
less than 12 in. wide separate in ** narrow widths."

Wirelathing. — 9. These being narrow, it is advisable
to measure them at per ft. run, stating the width.

Cornices. — 11. Cornices and mouldings under 12 in.
girt are measured at per ^. run and those over this
girt at per ft. super, number all mitres, stoppings, etc. ;
those to the running items following same, and those
to the superficial items averaged for girt. See whether
bracketing is required; if so, take the girt required at
per ft. super., numbering angle brackets to mitres and
returned ends, and averaging the girt.

Measure the walls and ceilings less by the height and
projection of the cornice, and add to the girt of the
cornice 2 in. (i. e., 1 in. for each edge) for the portion
lip to the ceiling and walls.

Enrichments are measured at per ft. run, giving the
girt and description, and including the modelling. If

BILL OF QUANTITIES • 47

of exceptional character, a provision for modelling is
sometimes inserted.

Angles. — 12. These appear in bill in feet run with
the girt of moulding or bead (if any) and also the
widths of returns. Number the stops, mitres, etc., al-
lowing each to follow the item to which they apply.

The finishings to concrete beams, lintels, etc., is kept
separate as in ** narrow widths to beams, etc./' and all
arrises, etc., being measured at per ft. run.

Skirtings or Dadoes.— 13. Describe skirtings or dadoes
giving height and projection, and also finish at top, and
measure at per ft. run, numbering all mitres, ends, etc.
Include the dubbing with the item. The general wall
plastering is deducted for these.

Floating for mosaic and tile pavings appears in the
bill in yard super.

Quirks. — 14. Labor to splays, quirks, arrises, etc.,
are measured at per ft. run.

The attendance on trades is frequently measured in
detail, as '* making good around mantels" or gratings,
etc.

The cutting-out and making good appears at the end
of the bill in the form here given.

Bough Cast. — 15. As clauses 8 and 10.

Lime Whiting and Distempering. — 16 and 17. These
appear in the bill in yd. super! In the case of distem-
pering, if the colors are in any way special mention
this, and also if in dadoes and filling, taking the di-
viding line in feet run.

Distempering on cornices is usually measured in ft.

super., stating the number of tints, and if lines picked

out in ft. run ; as is also distempering on enrichments,

^taking the latter as ** extra to,*' the distempering to

cornices being measured over enrichments.

48 . CEMENTS AND CONCEETES

LATHS GENIALLY. ^

General opinion is undoubtedly in favor of split
laths, and split laths are sometimes specified by archi-
tects for ceilings and partitions. Sawn laths, unless
cut from specially selected straight-grained stuff, would
most assuredly have weak places from uneven grain,
and in order to avoid this weakness the sawn laths
would have to be made thicker than split laths, and
only the best quality should be used. Oak laths, for-
merly used, are very liable to wiarp. The defects that
are to be avoided in laths are sap, knots, crookedness,
and undue smoothness. The sap decays; the knots
weaken the laths; the crookedness interferes with the
even laying on of the stuff, and the undue smoothness
does not give sufficient hold for the plaster on the lath.
Riven laths, split from the log along its fibres, are
stronger than sawn laths, as in the latter process the
fibres of the wood are often cut through. Sawn laths
are, however, cheaper than riven laths, and have super-
seded^ them, which is not desirable in good work. Thick
laths, because of the strain upon them, should be usied
in the ceilings, and the thinner laths should be used in
vertical partitions, etc., where the strain is but small.
Some walls and partitions have to stand rough usage;
in such cases the thicker laths are necessary. Laths are
usually spaced with about % in. between them for key.
A bunch of laths usually contains 360 lin. ft. and such
a bunch nailed with butt joints, covers about 4^ super,
yd., and requires about 400 nails if the laths are nailed
to joists 16 in. from center to center. The length of
laths varies from 3 ft. to 4 ft. Laths are best nailed so
as to break joint entirely, because, for various reasons,
there is a tendency to crack along the line of the joints

BILL OF QUANTITIES 4J9

if the laths are nailed with the butt, ends in a row. This
may be obviated hy breaking joints; ceilings are much
stronger if the laths are nailed in this way. Laths,
however, are usually nailed in. bays, about 4 ft. or 5 ft.
deep. Every lath should be nailed at each end, and also
at the place where the lath crosses a joist or stud. Lap
joints at the end of laths, which are often made in or-
der to save nails, should not.be allowed, as this leave?
only ^ in. for the thickness of plaster. Butt joints
should always be made. Joists, <etc., that are thicker
than two in., should have small fillets nailed to the un-
der side, or be counter lathed, so that the timber surface
of attachment may be reduced to a mini;num and the
key not interfered with.

Lathing nails are usually of iron, and are galvanized,
cut, wrought, or castj where oak laths are used, the
nails should be oxidized or wrought. Oxidized nails
should also be used with white cement work. Zinc nails,
which are expensive, are used in very good work, be-
cause of the possibility of the discoloration of the plas-
ter by the rusting of iron nails. The length of lathing
nails depends on the thickness of the laths, % in. nails
being used for single laths, and 1^ in. nails for double
laths.

TOOLS AND APPLIANCES USED BY THE
^ PLASTERER.

The illustriations shown at Figs. 1 and 2 show a num-
■ber of tools, and appliances made use of by the plas-
terer, and others — speeial-r-will be shown further on,
when it is necessary to describe and illustrate some
special process or method of working. The tools the
plasterer requires are many and varied, and may be
enumerated about as follows: They consist of moulds
for running cornices, and center moulds, which may
never be used only in the one piece of work, as the de-
signs and styles of cornices and centers are continually
changing. As these tools do not cost much, however,
the changes do not fall heavily on the workman ; but it
is as well, whenever it can be done, to charge each
mould against its own particular job of work. A good
spade and shovel will be absolutely necessary to the
plasterer's outfit, and will be among the first tools he
will require. These should be light and strong, and
well handled, or helved; after using they should have
all the lime and mortar cleaned off them, and should
be placed away where they will not be exposed to the
weather.

The following list and descriptions of tools will give
a new beginner an idea of the kind and character of
tools he will be likely to require before he can success-
fully carry on the plastering business. Most of these
tools will be illustrated further on:

The Hoes and Drags. — These are tools so well known
that they require no description here. They are used

TOOLS AND APPtilANCES

■52 CEMENTS AND CONCRETES

chiefly for mixing hair in the mortar, and for loosening
mortar when too '* stiff," or when it has developed k
tendency to ''set." They are also used for preparing
'*putty" and fine ''stuff." (See Fig. 2.)

The Hawk, which is a square board about thirteeiji
inches square, with a short handle on the under side.
It is used for holding stuff while the operator is ajt
work. It is generally made of pine or some other light
Avood; it is made thin on the edges, being beveled fronii
the center on the under side to each of the four edges;
the handle should be about six inches long, and one and
a half inches in diameter.

The Mortar-Board is a board similar to a table top,
and is about fortj'- inches square; it is made by joint-
ing two or more boards together, which are secured by
two battens, and screws or nails. * It is used for holding
the mortar delivered from the hod direct by the laborer.

Trowels, which are of two kinds : the ordinary trowel,
which is formed of light steel four inches wide and
about twelve inches long; this is the laying and smooth-
ing tool, and is the most important in a plasterer's out-

fit. The other is termed a gauging trowel, and is used
for gauging fine stuff for courses, etc. ; it varies in size
from three to seven inches in length.

Of Floats, which are used for floating, there are three
kinds, viz.: the darby, which is not a proper float, is
single or double, as liiay be required; the single being
for one man to use, the double for two. The single one
should be four feet, five inches long, and about four
inches wide, with a handle, near one end, like a hawk
handle, and a cleat near the other end running length-
wise of the blade ; the lon^ darbvs have a hawk handle
on eaclLend. The hai^i, float, which is used in finishing,
and the quick float, which is us'^^d in floating angles.

TOOLS A|s[I) APPI/IANCES

J. .TT y

' •''!..-;

^fTc/fJaaf

^7^^ Af^/pf/7 TroH^A

A/iode///n^ 7oo/s

NO. 2.

54 CEMENTS AND CONCRETES

The hard float is made of good pine, and has a semi-
circular handle on the back; a strip of hard wood is
sometimes dovetailed into the blade, and the handle is
screwed fast to the strip previous to the latter being
driven in the dovetail; this is a good way, as there are
no nails then driven through the blade, which, by the
rapid wearing of the latter, would soon project above
the blade and scratch the plaster where it was intended
to have it smopth. The quick float is seldom used in
this country; it is shaped like the angle it is intended
to work down, and is a trifle handier for this purpose
than the ordinary hard float.

Moulds. — These are used for running .stucco cornices,
and are infinite in shape and variety. The reverse of
the contour of the cornice is cut out of sheet copper or
iron, and is firmly attached to a piece of wood which
is also cut out the reverse shape of the intended mould-
ing. Their uses will be explained under the head of
Operations. Moulds or matrices for leaves, flowers, or
other ornaments are made of plaster and glue, or bees-
wax; these will be discussed hereafter.

Center-Moulds are made on the same principle as the
reverse moulds for linear cornices, with an arm at-
tached which is perforated at different radii to suit the
diameter of center-piece. Sometimes the moulds for
cornicing are so formed, by placing the plates at an an-
gle of forty-five degrees, that they will finish the cor-
nice right into the angle and form the mitre ; more fre-
quently, however, the mitres are finished by hand.

The Pointer is nearly the same shape as a bricklayer's
trowel, but it is not so large, being only about four
inches long. It is chiefly used for small jobbing, or
mending broken or defective ^ork.

TOOLS AND APPLIANCES 55

The Paddle is simply a piece of pine wood less than
thre 3 inches wide and six long, by one thick ; it is made
wedge shaped on one end, the other end being rounded
off ibr a. handle. Its use is to carry stuff into angles
when finishing.

Stopping and Picking-Out Tools, or, as they are fre-
quently called, Mitering Tools, are made of fine steel
plato, seven or eight inches long, and of various widths
and shapes. They are used for modeling, and for fin-
ishing mitres and returns to cornices by hand where the
moulds cannot work.

Mitering-Rod. — This is a tool one foot or more long,
and about one-eighth of an inch thick, and three inches
wide, the longest edge is sharp, and one end is bev-
elled off to about thirty degrees. It is used for clean-
ing out quirks in mouldings, angles, and cornices.

The Operator also requires a good whitewashing
brush with a short handle. The best should be ob-
tained, as it will prove the "cheapest in the end.

A Scratcher is generally made of short pieces of pine
two inches wide and one inch thick; three or four of
them are nailed to two cleats, and are placed about an
inch apart. The center slat should be about eighteen
inches longer than the others, so as to form a handle.-
See illustrations. The slats on the opposite end to the
handle should be cut off square with one side arid point-
ed. Its use is to make grooves, or bond in what is called
the scratch coat. When completed it has somewhat the
appearance of a gridiron.

Hod. — This is formed by two boards, eleven and
twelve inches wide, respectively, and eighteen inches
long, the wide board being nailed on the edge of the
narrow one, making a right-angled trough; one end is
closed, and the end piece is rounded over the top; the

56 CEMENTS AND CONCRETES

boards forming the sides are rounded at the opening.
A handle about four feet long and two inches in diam-
eter is then fastened about two inches forward of the
middle nearer to the open end, and a piece of wood
called a pad is fitted with a groove on the angle just
back of the handle. The object of this block is to pre-^
vent the arris of the hod from chafing the shoulder of
the^laborer. Much controversy has taken place among
workmen at various times regarding the exact size of
hod, but this, I think, should be governed more by the
strength of the person who has to use the particular
hod than by any fixed rules. Hods for carrying mortar
need not be so large as hods intended for carrying
bricks. (See No. 2, Fig. 1.)

Sieve, — This is used for straining through putty for
finishing; it requires to be very fine for the purpose.
Sometimes a hair sieve is used, but they are not last-
ing, and should never be used when a wire sieve is ob-
tainable. Sometimes a hair sieve may prove convenient
where dry plaster or cements have to be run through a
sieve of some kind before it can be used; so, on the
whole, the plasterer who desires a full and complete
outfit, should provide himself with one good hair sieve,
and at least two sieves of wire. (See Fig. 7, No. 1.)

Sand Screens are usually twenty-one inches wide in-
side by about six feet long. On small work they are
stood up at an angle of forty-five or more degrees, and
the sand is shovelled against them ; in some large works
the 'screen is suspended, and one man shovels in the
sand and a second one swings or shakes the screen.
These screens, to be lasting, should have their sides and
ends made of sheet iron, and the bottom should be
formed with parallel rods of small round iron having
wires running across them at regular intervals. . These

TOOLS AND APPLIANCES 57

cross wires should be attached to th«f iron rods so as to
hold them in place. The parallel rods may be placed
at such distances from each other as will be most con-
venient for the work in hand.

Mortar Beds are made of rough lumber of any kind,
and should be built partly in the ground, where cir-
cumstances will permit. They require to be strongly
put together, as they have considerable weight to sus-
tain. The writer has seen mortar beds built up with
bricks and cement where large works have been under
construction. Sometimes, master workmen, who do a
large business, and who employ a great number of men,
keep a large mortar bed or two in the rear yard of
their shop and tool house, in which they keep always
en hand a supply of ready-made stuff, which enables
them to do small jobs or repairs at a moment's notice.

The Slack Box. — This is generally made of boards,
and is eight or nine feet long, and from two to four
feet wide, and twelve or sixteen inches in depth. An
opening about eight inches square is left in one end,
with a slide door attached, so that it can be opened or
closed at pleasure. The opening should be covered on
the inside with a grating, so that when the lime is run
off no lumps or stones will get through. The grating
may be made with iron rods, or may be formed with
wooden laths or slats. The bottom of the box should
be made as close and tight as rough boards will permit.
(See No. 1, Fig. 11.)

Lathing^ — It frequently happens in towns and coun- '
try places that the plasterer has to do his own lathing,
or at least have it done under his own supervision,
therefore it will be necessary to have something to say
on this subject, and on the tools employed by the work-
man whose duty it is to prepare the walls for the plas-

58 ' CEMENTS AND CONCRETES

terer. These tools need not be extravagant ones or
many in number. THey consist of the following:

Lather's Hatchet. — This is a small hatchet with a
blade not more than one and a half inches wide, and
rather larger in proportion than ordinary hatchets.
The opposite end to the cutting edge is a hammer, with
which the lather drives the nails. Sometimes the face
of the hammer end is grooved, which makes it cling to
the nails if the latter are not struck fairly on the head.
An expert lather, however, will prefer a flat hammer
face for driving lath nails. The cutting edge is used
for ** nipping" off laths when they are too long, or
when short spaces of lathing are required to be made.
In cutting lath with the hatchet, the workman gives the
wood a short sharp blow with the tool at the point
where the severance is required, and the lath is in-
variably cut at the first blow, if the operator is an ex-
pert. (See 0, Fig. 2.)

Nail Pocket. — Perhaps the best nail pocket a lather
can have is made from a portion of an old boot leg cut
off to about four inches deep, and having a bottom of
semi-circular shape made of wood, and to which the
portion of the boot is fastened by means of broad-head-
ed tacks. The pocket is fastened to the workman's
waist by means of a strap, or other suitable device, and
hangs in front of him in a convenient position. Some-
times nail pockets are made of canvas, but these are
not so handy, as the top is apt to close and then nails
are difiicult to get at. This never occurs with the boot
leg pocket.

Cut-off Saw. — ^A cross-cut saw is an indispensable
tool to the lather for cutting lath in larger quantities
for short spaces, and for rigging up platforms to work
on, and for cutting supplementary studding or strips

TOOLS AND APPLIANCES 59

where such are necessary. The saw should have rather
coarse teeth and have plenty of set. Usually, the lather
thinks that almost any old used-up saw is good enough
for this purpose, and we find him struggling away with
all his strength cutting through a bundle of lath, when,
if he had a saw that was worth anything — as a saw —
he would perform his labors with about one-half the
effort, and one-third of the time. It is all wrong to
think of being ^ble to work satisfactorily with inferior
or imperfect tools. There is no economy in using tools
of this kind, and any lather who fancies he iis going
to make or save anything by making use of an old
buckled, mortar-stained saw, makes a terrible mistake.
Get a good saw and keep it in good order, and it will
pay you in two weeks. (See X, Fig. 2.) Besides these
enumerated, there are many other tools and appliances
that the plasterer will require, such as jointing rules,
moulding kbives, modelling tools, drags> chisels, com-
passeSy plumb rules, etc.

PLASTER, LIME, CEMENTS, SAND, ETC.

Plaster of Paris, — Gypsum, from which plaster of
Paris is made, is a sulphate of lime, and is so named
from two Greek words — ge, the earth; and epsun, to
concoct, i. e., concocted in the earth. In Italy it is
known by the name of gesso; in Scotland it is called
stucco; in this country it is known as calcined plaster;
and in the English trade as plaster. The term '* plas-
ter'' will henceforth he used in this book. The writings
of Theophrastus and other Greek authors prove that
the use of plaster was known to 'them. A stone, called
by Theophrastus gypsos, chiefly obtained from Syria,
was used by the ancients for converting into plaster.
Gypsum is mentioned by Pliny as having been used by
the ancient artists, and Strabo states that the walls of
Tyre were set in gypsum. The Greeks distinguished
two kinds — ^the pulverulent and the compact. The lat-
ter was obtained in lumps, which were burnt in the fur-
naces, and then reduced to plaster, which was used for
buildings and making casts.

Gypsum is found in most countries — Italy, Switzer-
land, France, Sicily, The United States, and some of
the South American States; also in Newfoundland and
Canada. The latter is said to be the finest deposits in
the world. It is found in England in many places.
The finest gypsum is called ''alabaster," and is soft,
pure in color, and fragile. This white translucent ma-
terial is a compact mass of crystalline grains, and is used
tor making small statuary, vases, and other ornaments.
Gypsum is found in immense quantities in the tertiary

PLASTER, LIME, ETC. 61

strata /of Montmartre, near Paris. This gypsum usual-
ly contains 10 per cent, of carbonate of calcium, not al-
ways in intimate union with the sulphate, but inter-
spersed in grains. This sulphate gives the Paris plas-
ter some of its most useful properties. Pantin, near
Paris, has l^rge beds of gypsum, one bed being hori-
zontal and over 37 ft. thick.

The term ** plaster of Paris" was mainly applied to
it because gypsum is found in large quantities in the
tertiary deposits of the Paris basin. Another reason
is that lime and hair mortar is seldom used in Paris for
plaster work, plaster of Paris being used for most kinds
of internal and external work. Plaster is known in the
color trade as terra alba. Plaster of Paris was known
in England by the same nanie as early as the beginning
of the thirteenth century. The gypsum, in blocks, was
taken .from France, and burnt and ground there. It
continued to be burnt and ground by the users until
the middle of the nineteenth century. The burning
was done in small ovens, and the grinding in a mill,
sometimes worked by horse-power, or more often by
hand.

Plaster is the most vigorous as it is the oldest vehicle
for carrying down generation after generation the mas-
terpieces of art with which the golden age of sculpture
CDriched the human race. For reproductive uses, plas-
ter enables youth to contemplate antiq[uity in its noblest
achievements. Today plaster is revolutionizing indus-
trial art for us, and in all probability for those who
are to come after us. Plaster, lowly and cheap, but
docile and durable, is the connecting agent with this
greatest of men's endorsement in the past. Plaster
thus employed in duplicating works of marble, pottery,
and metal work, is today extending the finest indus-

62 CEMENTS AND CONCRETES

tries, modern and ancient. Plaster is one of the best
known fire-resisting materials for building purposes.
After the conflagration at Paris, it was found the beams
and columns of wood which had been plastered were
entirely protected from fire. In cases where limestone
walls had been ruined on the outside by the flames pass-
ing through the window openings, the same walls in-
ternally escaped almost unscathed owing to their being
protected with plaster. Plaster in some climates has
great lasting properties. The Egyptians covered their
granite sometimes, and sand stone always, with a thin
coating of stucco. The Greeks coated even their mar-
ble temples with plaster, and the plaster portions are
now in better preservation than unprotected masonry,
particularly at Agrigentum in Sicily.

Quick and Slow Setting Plaster. — ^M. Landrin, in giv-
ing the results of his long continued studies relative
to the different qualities of gypsum, states that the
vifiiore or less rapid setting of plaster is due to the mode
in which it is burned. Its properties are very different
when prepared in lumps or in powder. The former
when mixed in its own weight of water sets in five min-
utes, while the latter under similar conditions takes fif-
teen minutes. The reason probably is that plaster in
powder is more uniformly burned than when it is in
lumps, which tends to prove this fact, that when the
latter is exposed longer than usual to the action of heat
it sets more slowly. Gypsum prepared at a high tem-
perature loses more and more of its aflSnity for water,
retaining, however, its property of absorbing its water
of crystallization. Plaster heated to redness and mixed
in the ordinary manner will no longer set; but if, in-
stead of applying a large quantity of water, the small-
est possible portion is used (say one-third of its

PLASTER, LIME, ETC. 63

weight), it will set in ten or twelve hours, and becomes
extremely hard. To prepare good plaster, it should not
be burned too quick to drive off all its moisture, and
for its molecules to lose a part of their aflSnity for the
water. If the plaster is exposed to heat until it has
only lost 7 or 8 per cent, of its moisture it is useless,
as it sets almost immediately. If, however, the burning
is again resumed, the substance soon loses its moisture,
and if then exposed to the air it very rapidly retakes
its water of crystallization, and absorption continues
more slowly. It then sets slowly, but attains great
hardness.

Testing. — The quality of plaster may be tested by
simply squeezing it with the hand. If it cohere slight-
ly, and keeps in position after the hand has been gently
opened, it is good; but if it falls to pieces immediately
it has been injured by damp. Although plaster does
not chemically combine with more than one-fourth of
its weight of water,*yet it is capable of forming a much
larger quantity into a solid mass, the particles of plas-
ter being converted into a network of crystals, mechan-
ically enclosing the remainder of the water. Sulphate
of lime (plaster) is soluble in water to the extent of 1
part in about 450, the solubility being but little influ-
enced by temperature. It is on account of this solu-
bility in water that cements which have to a large ex-
tent plaster for their bases are incapable in this raw
state of bearing exposure to the weather. The setting
of plaster is due to hydration, or its having but little
water to take up to resume a state of consolidation.
Plaster is used with hydraulic limes to stop the slaking,
and convert the lime into cement. These are then called
"selenitic."

In 100 parts of gypsum there are 46 acid, lime 32,

64 CEMENTS AND CONCRETES

and' water 22 parts. \i6ood plaster should not begin 1x)
set too soon, and it should remain for a considerable
time in a creamy state. When once set it should be
very hard. Plaster should set slowly, as it gives more
time for manipulation, but principally because one
which sets quickly and swells never becomes so hard
as slow-setting material. VPhe quality of plaster can-
not be determined by its color, the color being regu-
lated by that of the gypsum ; but all things being equal,
the whitest and hardest generally yields the best plas-
ter. But as the exception proves the rule, it may be
mentioned that some plasters (such as Howe's) are of
a delicate pink tint, and of a very fine grain, and ex-
ceedingly strong when gauged. This pink plaster is
much appreciated by many plasterers for making origi-
nals, as owing to its fineness and density it is very suit-
able for cleaning or chasing up models taken from the
clay, and also for durable moulding pieces. One of the
whitest plasters known, which is also very close in tex-
ture, is that manufactured by Cafi'erata. For cast work
the color of plaster is of small moment, because the cast
work is sooner or later colored with paint, and more-
over, unfortunately daubed over with distemper, or
worse still, with whitewash. Coarse plasters are darker
in color than fine. Coarse plasters of a sandy nature,
and which rapidly sink to the bottom when put in
water, contain too much silica, or improperly burnt
gypsum, or are derived from a bastard gypsjim, and
are generally of a weak nature.

Compressive and Adhesive Strength. — The compres-
sive resistance of properly baked plaster is about 120
lbs. to the square inch when gauged with neat water
and 160 lbs. when gauged with lime water; thus show-
ing that lime water hardens and improves the affinity

PLASTER, LIMB, ETU. 65

of plaster. The adherence of plaster to itself is greater
than to stone or brick. The adhesion to iron is from
24 to 37 lbs. the square inch.

French Plaster, — A considerable quantity of French
plaster was formerly used in this country but our own
is more unifonn in quality and cheaper in price, so the
use of the French material is somewhat limited. In
Paris various kinds of gypsum mortars are in general
use, raw gypsum and other materials being often inter-
mixed. They also contain free carbonate of lime, ac-
cording to the degree of heat to which the raw stone
has been subjected. The Hotel de Platres, in Paris,
affords a good illustration of the constructive uses to
which plaster can be put, some of the blocks being
about a hundred years old.

Limes, — ^Lime is one of the most important materials
in the building trades. Limestone is the general term
by which all rocks are roughly classified which have
carbonate of lime for their basis. They are obtained
from many geological formations, varying in quality
and chemical properties. The carboniferous consists
of nearly pure carbonate of lime. In the limestone of
the lias carbonate of lime is associated with silica and
alumina (common clay), in proportions varying from
10 to 20 per cent. Carbonate of lime is found in a state
of chemical purity in rhombohedral crystals as Iceland
spar. It is also found in six-sided prisms, ktiown to
mineralogists as arragonite. Its purest form as a rock
is that of. white marble. Colored marbles contain iron,
manganese, etc.

The lias strata consists of a thin layer, of hard lime-
stone separated by another of a more argillaceous char-
acter, or shale, containing various proportions of car-
bonate of lime.

66 CEMENTS AND CONCRETES

Hydraulic Limes. — ^Hydraulic limes are those which
have the property of setting under water or in damp
places, where they increase in hardness and insolubil-
ity. The blue lias lime formation is that from which
hydraulic lime is principally made. This lime, while it
has excellent hydraulic properties, can hardly be classed
as a cement. The stones which produce these limes con-
tain carbonate of lime, clay, and carbonate of mag-
nesia. The clay plays an important part in giving hy-
draulicity to the lime, consequently this power is great-
er in proportion to the amount of clay contained in the
lime. The proportion of clay varies from 10 to 30 per
cent. When lime contains clay it is not so easily slaked
as pure lime, and does not expand so much in doing
so, and therefore does not shrink so much in setting.

Lias lime (called blue lias from the color of the stone
from which it is produced) is very vari)able in quality
and is generally of a feeble nature, but is sometimes of
an hydraulic nature. M. Vicat divides them into three
classes: feebly hydraulic, ordinary hydraulic, and emi-
nently hydraulic. ** Those belonging to the first class
contain from 5 to 12 per cent, of clay. The slaking
action is accompanied by cracking and heat. They also
expand considerably, and greatly resemble the fat limes
during this process. They are generally of a buflf color.
Those of the second class contain from 15 to 20 per
cent, of clay. They slake very sluggishly in an hour
or so without much cracking or heat, and expand very
little. They set firmly in a week. The eminently hy-
draulic limes contain from 20 to 30 per cent, of clay,
are very difficult to slake, and only do so after a long
time. Very frequently they do not slake at all, being
reduced to a powder by grinding. They set firmly in
a few hours, and are very hard in a month."

PLASTER, LIME, ETC. 67

A natural hydraulic lime is obtained from what ap-
pears to be a sedimentary limestone that has been
formed by being deposited from water which held it in
solution. It is very fine-grained, and contains almost '
no fossils, and scarcely the trace of a shell is to be seen,
except at the top and bottoms of the divisions, which
are four in number, and in all from 9 to 12 ft. thick.
When first worked, the stone was slaked in hot kilnsj
but now this is effected by grinding. According to the
*'M*Ara*' process, the **lime shells'* from the kiln are
ground in the same way as the clinker of Portland ce-
ment. Beginning with a stone-breaker, the lime passes
from this to a pair of chilled crushing rollers, and final-
ly to the millstones, after which the powder is carried
by scre^-conveyor and elevator to a rotary screen, 12 ft.
by 4 feet, covered with wire cloth, which retains and
returns to the millstones any residue in excess of the
required fineness. Sifting is a very important factor in
the process, as it is scarcely possible to have the mill-
stones so perfect that they will not pass a few large
particles.

The residue of imperfectly ground lime will doubt-
less slake when mixed with water, but at long or un-
certain periods, so that it is obvious that fine grinding
is a necessity, and the setting properties are not fully
aiid safely developed unless the whole is finely pulver-
ized. With regard to **Fat lime": the general prac-
tice is for lime producers to show their lime as rich as
possible by analysis, and for users to prefer a rich lime,
for the reason that it makes a more plastic and better
working mortar with the usual quantity of sand. Now,
it has been proved by experiments, many and varied,
and extending over a long period, by the most eminent
authorities, French, German, English and American,

68 CEMENTS AND CONCRETES

that this preference should exactly be reversed, and
that the poorer common limes will make the best mor-
tar, and will, in a comparatively short time, show some
light setting power, whereas the very rich limes never
take band, except in so far as they return to their orig-
inal condition of carbonate by the reabsorption of car-
bonic acid from the atmosphere, and by the slow evap-
oration of the water of mixture. If it does not evapo-
rate, the mortar remains always soft. If it evaporates
too quickly, the mortar falls to powder, a result which
must be in every one's experience who has witnessed
the taking down of old buildings, and the clouds of
dust created by the removal of every stone.

Some of the stones from which fat lime is produced
contain a portion of sand as an impurity. They there-
fore yield an inferior substance. This, though cheaper,
is not so economical as pure lime, as it does not increase
its volume so much when slaked. The pure or fat lime
should only be used for plastering, as it is easily slaked,
and therefore not so liable to blister as most hydraulic
limes. It expands to double its bulk when slaked, and
can be left and reworked again and again without in-
juring it.

The Romans are said to have prepared their limes.
This *4ime putty,'' prepared by immersion for a longer
or shorter period — seldom less than three weeks — ^before
being used, is laid on in a very thin coat, and gives
a hard skin to the surface. This hardness is largely, if
not wholly, due to the fact that the lime is laid on in
a thin layer on the floating coat that has already ab-
sorbed carbonic acid from the air. This thin layer be-
comes harder than the main body Ox tke plaster.

The whole process of preparing lime and laying li
on the walls in thin coats, with a considerable space ox

PLASTER, LIME, ETC. 69

time between the coating, is conducive to the ultimate
hardness of the whole. The lime is first slaked, and
then made into coarse stuff, and setting stuff, all this
t'me being exposed to the carbonic acid of the atmos-
phere. Again, each coat is long exposed to the same
influence before being covered with the next, although
in marked contrast to the system of using the mortar
in building.

Calcination. — The process of **lime burning" is car-
ried out in several different ways. But whether the
operation be carried out in the simplest manner, or in
kilns constructed on the most scientific principles, it
will still depend (both as regards the quality and quan-
tity of lime produced) upon the kilnsman, as it is only
by constant observation from day to day that the man
becomes capable of judging whether the proper tem-
perature has been reached or that a correct opinion
can be formed as to the effects produced by the various
disturbing causes which exert an important infiuence
upon the working of a kiln, such as its size, shape, the
quality of the fuel, and the state of the atmosphere.
The kihis vary in size and shape in different districts,
though, they are generally inverted cones or ellipsoids,
into which layers of limestone and fuel are alternately
thrown. When worked continuously as running kilns,
the lime is periodically withdrawn from below, fresh
quantities of fuel and stone being filled in at the top.
When lime has not been properly calcined, or *'dead
burnt," it will not slake with water. This may arise
from two causes — from insufficient burning, when the
limestone, instead of being entirely caustified, has only
been changed into a basic carbonate, consisting of two
equivalents of lime and one of carbonic acid, one-half
only of its carbonic acid having been expelled. This

70 CEMENTS AND CONCRETES

basic carbonate, .on the addition of water, instead of
forming a hydrate of lime, and being converted into
a fine and impalpable powder, attended with the pro-
duction of a large amount of heat, is changed, with
little elevation of temperature, into 'a mixture of hy-
drate and carbonate. In the case of hydraulic limes
which contain a considerable amount of silica, * this
*'dead burning" may arise from the limestone having
been subjected to a too high temperature, whereby a
partial fusion of the silicate of lime formed has been
produced, giving an impervious coating to the inner
portions of the stone, retarding the further evolution
of the carbonic acid. On this account the eminently
hydraulic limes require to be carefully calcined at as
low a temperature as practicable ; and hence it is not
infrequently found that lias lime has been imperfectly
calcined. Pure limes, if ,subjected to an excessive
temperature, exhibit somewhat less tendency to com-
bine with water than is the case with lime properly-
calcined. Caustic limes unite with water with great
energy, so much so as to evolve a very considerable
amount of heat. When water is poured upon a piece
of well-burnt lime heat is rapidly generated, and the
lime breaks up with a hissing, crackling noise, the
whole mass being converted in a short time into a soft,
impalpable powder, known as ** slaked lime.''

Slaking. — Chemically speaking slaked lime is hydrate
of lime — that is, lime chemically combined with a
definite amount of water. In the process termed ''slak-
ing" one equivalent or combining proportion of lime
unites with one equivalent of water, or in actual weight
28 lbs. of lime combines with 91 lbs. of water (being
nearly in the proportion of three to one) to form 37
lbs. of solid hydrate of lime. The water loses its liquid

PLASTER, LIME, ETC. 71

condition, and it is to this solidification of water that
the heat developed during the process of slaking is
partly due.

Slaking is a most important part in the process of
making coarse stuff and putty lime. Unless the slak-
ing is carefully and thoroughly done, the resultant ma-
terials are liable to ** blister" or **blow,'' owing to
small particles still remaining in a caustic state. Blis-
ters may not show until a considerable time has
elapsed. There are three methods of slaking ** lump-
lime" — ^the first by immersion; the second by sprink-
ling with water; and the third by allowing the lime to
slake by absorbing the moisture of the atmosphere/
Rich limes are capable of being slaked by immersion,
and kept in a plastic state. They gain in strength by
being kept under cover or water. Pliny states that the
Romans had such great faith in this method that the
ancient laws forbade the use of lime unless it had been
kept for three years. All rich limes may be slaked
by mixing with a suflScient quantity of water, so as to
reduce the whole to a thick paste. Lump lime should
first be broken into small pieces, placed in layers of
about . six inches thick, and uniformly sprinkled with
water through a pipe having a rose on one end, or by
means of a large watering-can having also a rose, and
covered quickly with sand. It should be left in this
state for at least twenty-four hours before being turned
over and passed through a riddle. The layer of sand
retains the heat developed, and enables the process of
slaking to be carried out slowly throughout the mass.
Any unslaked lumps may be put into the middle of the
next heap to be slaked. The quantity of water should
be perfectly regulated, as if over- watered a useless paste
is formed. If a sufficient quantity is not supplied, &

72 CEMENTS AND CONCRETES

dangerous powdering lime is produced. Slaldng by
sprinkling and covering the lime lumps is frequently
done in a very imperfect and partial manner, and por-
tions of the lime continue to slake long after the mortar
has been used. Special care must be exercised, and
sufficient time must be allowed for the lime to slake
when this method is employed.

Different qualities of lime require variable amounts
of waiter; but the medium quantity is about a gallon
and a half to every bushel of lime. No water should
be added or the mass disturbed after slaking has be-
gun. In most places the lime for making coarse stuff
is generally slaked by immersion, and is run into
a pit, the sides of which are usually made up with
boards, brick work, or sand, the lime being put into
a large tub containing water. When the lime is slaked,
it is lifted out by means of a pail, and poured through
a coarse sieve. It is sometimes made iii a large oblong
box, having a movable or sliding grating at one end to
allow the lime to run out and also to prevent the sedi-
ment from passing through.

In preparing lime for plaster work, the general prac-
tice is to slake it for three weeks before using. Not
only so, but a particular cool lime is selected, for the
reason that it is not liable to blister and deface the
internal walls when finished. Now, while all this pre-
caution is taken in regard to plastering, in making mor-
tar for building the lime is slaked and made up at
once, and it is frequently used within a day or two.
But this is not all. Limes which are unsuitable for
plaster work, known as hot limes, and which, when
plasterers are obliged to use^ must be slaked for a
period of — ^not three weeks, but more — ^nearly three
months before using, and are then not quite safe from

PLASTEE, LIME, ETC. 73

blistering, are the limes mostly used for building pur-
poses. It will at once be seen that when mortars of
these limes are used immediately, the unslaked par-
ticles go on slaking for a long time, drying up the
moisture, and leaving only a friable dust in the joints.
This should help in understanding the old Roman law
which enacted that lime should be slaked for three
years before using. If three years should seem to us
an absurd tinae, yet it may be justly said that at least
three months are required to slake completely, and to
develop fully the qualities of many of the common
limes in everyday use. Major-General Gillmore, the
eminent American specialist on the subject of Limes
and Cement, mentions that in the south of Europe it
is the custom to slake the lime the season before it is
to be used.

Mortar. — This is a term used for various admixtures
of lime or cement, with or without sand. For plaster
work it is usually composed of slaked lime, mixed with
sand and hair, and is termed ** coarse stuff/' and some-
times **lime and hair," also "lime." In Scotland the
coarse stuff is generally obtained by slaking the lump
lime (locally termed shells) with a combination of
water sprinkling and absorption. The lime is placed in
a ring of sand, in the proportion of one of lime to
three of sand, and water is then thrown on in suffi-
cient quantities to slake the greater portion. The whole
is then covered up with the sand, and allowed to stand
for a day; then turned over, and allowed to stand for
another day; afterwards it is put through a riddle to
free it from lumps, and allowed to stand for six weeks
(sometimes more) to further slake by absorption. It
is next '* soured" — that is, mixed with hair ready for
use. Sometimes when soured the stuff is made up in

74 CEMENTS AND CONCRETES

a large heap, and worked up again as required for
use. This method makes a sound, reliable mortar. In
some parts lime slaked as above is mixed with an equal
part of run lime. This latter method makes the coarse
stuff *' fatter" and works freer. All slaked limes have
a greater affinity for water than the mechanically
ground limes.

Grinding is another process for making mortar or
*'lime," and if made with any kind of limestone is
beneficial. It thoroughly mixes the material, increases
the adhesion, adds .to the density, and prevents blister-
ing.. When there is a mortar-mill, either ground or
lump lime can be used, and the coarse stuff may be
made in the proportion of.l part lime and 3 parts
sand. The lime should be left in the mill until thor-
oughly reduced and incorporated, but excessive grind-
ing is detrimental. The process should not be con-
tinued more than thirty minutes. Both material and
strength is economized if lump lime is slaked before
being put in the mill.

When a mortar-mill is used for grinding the lime,
the sand may be partly or wholly dispensed with, and
excellent results are obtained by using old broken bricks
(clean and well burnt), stone chippings, furnace cin-
ders (free from coal), or slag. It is most essential in
all cases that the materials used should be perfectly
clean. It should be "Borne in mind that a complete in-
corporation of the ingredients is essential in the slak-
ing and mixing for coarse stuff, whether done by hand
or machine. The sand or other material used can be
tested by washing a portion in a basin of clean water^
then sifting through a fine sieve. If there is an undue
residue of clay, fine dust or mud in the water or sieve,
the whole of the aggregate should be washed or re-

PLASTER, LIME, ETC. 75

jected. Lias lime should be mixed dry with sand and
damped down for seven or ten days to ensure slaking.
It should not be used fresh for floating or rendering.
Pure or rich limes are not so well adapted for outside
work, or places exposed to the action of damp, as hy-
draulic limes. Mortar should be well tempered before
using. Pliny states that it was an ancient practice to
beat the mortar for a long time with a heavy pestle
just before being used, the effect of which would be
not only more thoroughly to mix the materials, but to
take from the outside of the sand the compound of
lime and silica (if such had been formed during the
period of seasoning) and by incorporating it with the
mass, dispose it more rapidly to consolidate. Smeaton
found that well-beaten mortar set sooner and became
harder than mortar made in the usual way. Mortar
made from hydraulic limes should be mixed as rapidly
as is compatible with the thorough incorporation of the
materials, and used as soon as practicable after mixing,
because if put a^ide for any length of time its setting
properties will deteriorate.

Pure limes, may be rendered hydraulic by mixing,
Ibem with calcareous clays or shales, which have been
so altered by the agency of heat that the silica they con-
tain has to some extent assumed the nature of soluble
silica. Ill good coarse stuff each granule of sand is
coated over with the lime-paste so as to fill the inter-
stices; the lime-paster is to hold the granular sub-
stances in a concrete form. If too much lime-plaster,
is present, it is called *'too fat''; if the lime-paster is
deficient it is ''too lean" or ''poor.'' This can be
tested by taking up a portion on a trowel; the "fat"
will cling to the trowel while the "lean" will run off
like wet sand. The coarse stuff can be tested by mak-

76 CEMENTS AND CONCRETES

ing briquettes and slowly drying; the good will stand
a great pressure, whereas the bad will not^n some
cases falling to pieces. Some coarse stuff will appear
*'fat" on the trowel, but it may be the fatness of mud,
not the fatness of lime, because sometimes sand is
adulterated with fine-screened earth. When this stuff
is made in the form of briquettes and dried, it will be
extremely friable and easy to crush; or if put into
water until soft, the earthy matter can be seen. Fine-
screened earth, when dry afid in bulk, does not seem
an objectionable material; but in a wet state it is dirt
or mud, and should at once be sent off to the works.
All limes increase in strength by the addition of sand,
being the reverse of Portland cement, which is weak-
ened by this addition. Mr. Read made four samples
of mortar with the proportions of ground lime and sand
as follows: '* Ground lime mixed with 4, 6, 8 and 10
parts of clean washed sand to 1 part of ground lime
respectively. All set and went hard. One of each
was placed in water; that made with 4 parts of sand
expanded and went to pieces; those with 6, 8 and 10
parts of sand remained whole, and continued to get
harder." The addition of a small proportion of brick
dust to mortar will harden and prevent the disinte-
gration of mortar. The proportions are 1 part of brick
dust, 2 parts of sand and 1 part of lime, mixed dry
and tempered in the usual way.

Adhesive Strength, — The adhesive strength of mortar
varies according to the amount of sand used. The
more sand used in the mortar, the less its adhesion.
The following table shows the force required to tear
apart bricks bedded in mortar made with the usual
proportions of sand at the end of twenty-eight days :

PLASTER, LIME, ETC.
Adhesive Strengths of Limes and Cements.

Fat lime and sand

(lto3)

4% lbs.

per Sq. In.

Common lias lime and sand

((

9 ''

(( (( tt

(( (( it <( <(

(lto4)

6% "

ti tt tt

Portland cement " **

(1 to 4)

23 ''

tt tt tt

<< (( tt ' It

(lto6)

15X ''

tt tt tt

The old mortar which was held in such high esteen*
by the Romans is said to have consisted of iime mixed
with puzzolana or trass. Tra^s is a material similar
in its nature to puzzolana, obtained from extinct vol-
canoes in the valley of the Rhine, also in Holland, and
is largely employed in engineering works. The name
trass is derived from a Dutch word meaning a binding
substance. Much has been written and said about the
ancient and the old Rom^n mortars, but it may be
safely said that, from the year one up to the present
time, no cement or mortar has the strength, or could
excel, or stand our variable climate as well as Portland
cement. The primary cause of the premature deca>
which takes place in stuccos and cements, when used
externally as a coating to walls, is the presence of
muddy earth and decayed animal and vegetable matter
in the sand used in the lime and cement. To this may
be added the frequent impurities in the limes and ce-
ment themselves. The impurities in the sand may be
eradicated by a thorough washing, and the lime should
be carefully selected, prepared and manipulated. Hav-
ing now briefly reviewed the principal parts and
process of mortar, the practical conclusions to be
drawn are, that the quality of the lime is of as great
importance as the quantity, and thorough slaking is
imperative ; that the proportions of sand may vary con-

78 CEMENTS AND CONCRETES

siderably, and that it should be coarse and irregular in
size, and of a clean and hard nature.

The Hardening of Mortar. — According to the results
obtained from tests and experience, the hardening of
mortar is due to several causes acting collectively.
These causes appear to be absorption of carbonic acid
from the atmosphere, and the combination of part of
the water with the lime which act upon the sand, dis*
solve and unite with some of the silica of the sand is
composed, thus forming a calcium silicate (silicate of
lime). / Some authorities state that the silicate of lime
is formed by the reaction of lime and silicate, of mor-
tar, and to this is due the hardness of old mortar. In
mortar fr^om the pure lime, the initial setting is due
to the evaporation of water, and to the production of
minute crystals of hydrate of lime, which slowly ab-
sorbs carbonic gas from the air, the rapidity of this
absorption necessarily decreasing in proportion to the
difficulties presented to the free access of air. The
setting and hardening of hydraulic limes are due mainly
to crystallization brought by the action of water on
the silicate of lime and not mere absorption of carbonic
gas from the atmosphere, as is the case of fat limes.

The Romans were convinced that it was owing to
prolonged and thorough slaking that their works be-
came so hard, and were not defaced by cracks. Al-
berti mentions that he once discovered in an old trough
some lime which had been left there five hundred
yeai4, as he was led to believe by niany indications
around it, and that the lime was as soft and as fit to
be used as if it had been recently made. Common mor-
tar made of rich lime hardens very slowly, and only
by the evaporation of the water of the mixture, and by
the absorption of carbonic acid from the atmosphere.

PLASTER, LIME, ETC. 79

with which it forms a crystalline carbonate of lime.
This process, however, is so slow, that it gave rise to
the French proverb that '*Lime at a hundred years old
is still a baby''; and there is a similar proverb among
Scotch masons, "When a hundred years are past and
gane, then gude mortar turns into stane/' Mortar
from the interior of the pyramids, where it has been ex-
posed to the action of the air, still contains free lime,
although it is five thousand years old. It has been
ascertained that in rich lime mortars the carbonic acid
penetrates about one-tenth of an inch into the joint in
the first year, forming a skin or film which opposes the
further absorption of carbonic acid, except at a decreas-
ing ratio, so that the lime remains soft for an indefi-
nite period. In illustration of this several cases have
been cited, amongst others one by General Treussart,
who, in the year 1822, had occasion to remove one of
the bastions erected by Vauban in 1666. After these* 156
years the lime in the interior was found to be quite
soft. Dr. John, of Berlin, mentions that in removing
a pillar of 9 ft. diameter in the Church of Saint Peter,
Berlin, eighty years after erection, the mortar was found
to be quite soft in the interior.

General Pasley mentions several instances at Dover
Harbor, and at Chatham dock yard, the latter in par-
ticular, when part of the old wall was pulled down in
the winter of 1834. The workmen were obliged to blast
the brickwork fronting the river, which had been built
with Roman cement, but the backing, done with commoti
lime mortar, was in a state of pulp; the lime used had
been prepared from pure limestone or chalk. But it
is 'unnecessary to go back so far for knowledge of the
absence of the setting quality in the rich limes, as
there have been frequent experiences of it in the pres-

80 CEMENTS AND CONCRETES

ent age. While these remarks are true of the richer
limes, many of our limes are comparatively poor in
carbonate, and associated with silica, alumina, mag-
nesia and oxide of iron, which may either be partially
combined in the natural state, or enter into combina-
tion with the lime during the process of calcination,
and these limes might be termed slightly hydraulic.

M. Landrin, who submitted to the French Academy
the results of some experiments on the hydraulicity and
hardening of cements and lime, came to the conclusion
that (1) silicates of lime raised to high temperature
set with difficulty, and in any case do not harden in
water; (2) for the recalcination of cements to exert
a maximum influence on the setting, in connection with
water of the compound obtained, the process must be
carried sufficiently far for the limes to act on the silica
so as to transform it into hydraulic, and not fused
silica; and (3) carbonic acid is an indispensable factor
in the setting of siliceous cements, in as much as it is
this substance which ultimately brings about their hard-
ening. The comparative strengths of various mortars
are shown in the following table:

PLASTER, LIME, ETC.

Ilia

If 4

'I
3i

8S t.s

82 CEMENTS AND CONCRETES

Magnesia in Mortars, — Magnesia plays an important
part in the '.'setting" of hydraulic limes as well as in
Portland cement Vicat, after many experiments, was
led to recommend magnesia as a suitable ingredient of
mortars to be immersed in the sea, stating that if it
could be obtained at a cost that would admit its appli-
cation to such purposes, the problem of making con-
crete unalterable by sea water would be solved. Gen-
eral Gillmore, speaking of the American lime and ce-
ment deposits, says: ** Magnesia plays 'an important
part in the 'setting' of mortars, derived from the ar-
gillo-magnesian limestone such as those which furnish
the Rosendale cements. The magnesia, like the lime,
appears in the form of a carbonate. During calcination
the carbonic acid is driven off, leaving protoxide of
magnesia which comports itself like lime in the pres-
ence of silica and alumina, by forming silicate of mag-
nesia and aluminate of magnesia. These compounds
become hydrated in the presence of water, and are
pronounced by Vicat and Chatoney to furnish gangues,
which resist the dissolving action of sea water better
than the silicate and aluminate of lime. This statement
Is doubtless correct, for we know that all of these com-
pounds, whether in air or water, absorb carbonic acid,
and pass to the condition of subcarbonates, and that
the carbonate of lime is more soluble in water holding
carbonic acid and certain organic acids of the soil in
solution than the carbonate of magnesia. At all ev« ats,
whatever may be the cause of the superiority, it is
pretty well established by experience that the cements
derived from argillo-magnesian limestones furnish a
durable cement for construction in the sea."

In Marshal Vaillant's report to the French Academy
of Sciences, from the Commission to which Chatoney

PLASTER, LIME, ETC. 83

and Rivot's paper was referred in 1856, this superiority
of the magneskn hydrates is distinctly asserted. .A few
years ago the French Government Office of Civil En-
gineers made a series of comparative tests on three sam-
ples each of French, English and German cement, in
which the results are given in favor of the German
cement, which contains magnesia to the extent of 2.4
per cent, against 0.26 in the English and 0.32 in the
French, and summed up thus: **A great value partly
due to the higher percentage of magnesia contained in
it.'' Gillmore further says that magnesian limestone
furnishes nearly all the hydraulic cement manufactured
in the western part of the State of New York. At
East Vienna it has been used for cement, and at Akron,
Erie County, N. Y., a manufactory of some extent is in
operation. Vicat says: ** Having analyzed several old
mortars, with the view of discovering, if possible, to
what their superior durability might be attributed, I
found, in some excellent specimens of very old mortar,
magnesia to exist in considerable proportions.'' The
limestones, therefore, from which these mortars were
prepared must have contained the silica and magnesia
as constituent ingredients; and it is to be remembered
that it is the presence of tjiese substances which com-
municates the property of hardening under water. Pro-
fessor Scorgie says of carbonate of magnesia: *' Mag-
nesium carbonate is a substance very similar to carbon-
ate of lime; it loses its carbonic acid in burning, com-
bines with silica, etc., and behaves generally in the
same way; it does not slake, however, on being wetted,
but combines with the water gradually and quietly sets
to some extent in doing so. Magnesium carbonate com-
bined with lime, reduces the energy of slaking, and in-
creases that of the * setting' process; when other sub-

84 CEMENTS AND CONCEETES

stances are present, its behavior and combination with
them are similar to those, of lime. When carbonate of
magnesia is present in sufficient quantity, say about 30
per cent., it renders lime hydraulic independently of
and in the absence of clay." Colonel Pasley also, by
experiments, demonstrated that magnesium limestones
are suitable for hydraulic mortars.

The foregoing assertions that magnesium carbonate^
combined with lime, reduces the energy of slaking and
incrieases that of the ** setting" processes are satisfac-
tory and conclusive. Many such evidences showing the
value of magnesia in hydraulic mortars might be quoted,
but perhaps these are sufficient.

Effects of Salt and Frost in Mortar, — ^Few experi-
ments have as yet been made to test the general effects
of salt in mortars, though as a preventive of the effects
of frost it has been tried with varying results.

In some experiments, designed to ascertain the effect
of frost upon hydraulic limes and cement gauged with
and without addition of salt to the water, cubes of stone
were joined together with cement mixed with water
ranging from pure rainwater to water containing from
2 to 8 per cent, of salt. Before the cement was set the
blocks were exposed in air at a temperature varying
from 20 to 32 degrees Fahr., after which they were
kept for seven days in a warm room. At the end of
this time the samples were examined. The cement
made with water was quite crumbled, and had lost all its
tenacity. The cement made with water containing 2 per
cent, was in better condition, but could not be described
as good ; while that containing 8 per cent, of salt had not
suffered from its exposure to the lowest temperature
available for the purpose of experiment. It is suggested
as possible that the effect of the salt was merely to pre-

PLASTEE, LIMB, ETC. 85

vent the water in which it was dissolved from freezing at
the temperature named, and so permitted the cement*
to set in the ordinary way. But it must be allowed
that in practice, salt dissolved in the water for mixing
mortar has been successfully used to resist the effect
of frost. A solution of salt applied to new plastered
walls in the event of a sudden frost will protect the
work from injury. The addition of a small portion
of sugar will improve its adhesion, and increase the
fros1>resisting powers.

Salt takes up the vapors from the atmosphere, caus-
ing the work to show efflorescence, and in some instances
to flake, especially in external work. That some en-
gineers believe there is 'sartue in salt water is beyond
doubt, because salt water has been named in their spedi-
fieations for the gauging of concrete. Salt in Portland
cement seems to act somewhat differently; as regards
efflorescence it shows more in this material than in lime
mortar. Salt should not be used in Portland cement
work that has to be subsequently painted. According to
the results of tests of mortar used for the exterior
lirick facing of the Forth Bridge piers below water they
• show a good average tensile strength. One part of
Portland cement and one part of sand were slightly
ground together in a mill with salt water, and briquettes
made from this gauge gave an average of 365 lbs. per
square inch at one week, and 510 lbs. at five weeks after
gauging. It would be interesting to note the condition
of this mortar a century hence, time being the trying
test for all mortars.

A solution of commercial glycerine mixed with the
setting stuff, or used as a wash on newly finished lime
plaster work, is a good preventive of the evil effects o^
frost. Glycerine solution may also be used for the same

86 CEMENTS AND CONCRETES

purpose on new concrete paving. Strong sugar water
mixed with coarse stuff has some power in resisting
frogt. The quantity depends upon the class of lime,
but the average is about 8 lbs. of sugar to 1 cubic yard
of coarse stuff or setting stuflf. The sugar must be dis-
solved in hot water and the stuff used as stiff as pos-
sible.

Sugar With Cement. — Sugar or other saccharine mat-
ter mixed with cement has been tried with varying
success. It is well known that saccharine is used with
mortars in India* According to some experiments made
in this country, the results obtained were that the addi-
tion of sugar or molasses delayed the setting of the
mortar, the retardation being greater when molasses was
used. When certain proportions were not exceeded, the
strength of the mixture was that of the pure cement,
Less than 2 per cent, of sugar must be added to Port-
land cement, and less than 1 per cent, to Roman, other-
wise the mortar will not hold together. The sugar ap-
pears to have no chemical action on the other materials,
crystals of it being easily detected on the broken sur-
faces, the increased bmding power of the cement
brought about by the addition of sugar being due more
to mechanical than chemic£^l causes. In my own experi-
ments with sugar added to Portland cement for cast-
ing deep undercut ornament figures and animals out
of gelatine moulds, the results at first were very irregu-
lar, some casts attaining great hardness, while others
crumbled to pieces. The time of setting also varied
considerably. Three different brands of cement were
used, and it was found that the cement containing the
most lime required more sugar than the lowest limed
cement, but the average is about II/2 P^r cent, of added
sugar. The sugar must be dissolved in the water used

PLASTER, LIME, ETC. 87

for gauging. The setting and ultimate hardness is also
influrneed by the atmosphere. The easts should be kept
in a dry place until set and dry, before exposing them
to d^mp or wet. Portland cement has a tendency (es-
pecially if over limed) to **fur" gelatine moulds, but
the sigared cement leaves the moulds quite clean.

In experiments by Austrian plasterers, mixtures of
1 pai t of cement and 3 parts sand, and 10 per cent, of
water, and of pure cement with as much water as was
necesmry to give the mass plasticity, were prepared.
FroHA. 1 to 5 per cent, of powdered sugar was well mixed
with the dry cement. The cement used was of inferior
quality, the sand being ordinary building sand, and
not the so-called *' normal' ' sand, which is of a superior
quality. They were left to harden in a dry place, and
not under water. For each series of samples made with
sugar a comparative series without sugar was prepared,
all the samples being made by the same man, under the
same conditions and with the same care. The tenacity
was ascertained by Kraft's cement-testing machine. The
strength, was far below that prescribed and generally
obtained. It should be mentioned that the samples with
sugar (especially those of pure cement) showed a strong
tendency during the first twenty-four hours to combine
intimately with the smooth china plate on which they
were placed to swell, and the results of the trial showed
that with mixtures of cement and sand, and by harden-
ing in a dry place, the binding effect may be increased
by the addition of sugar, which reached its maximum
with from 3 to 4 per cent, of sugar added. With pure
cement the binding effect was not much increased.t, If
the sugar used for gauging had been dissolved, and not
mixed dry, the results would have proved better.

88 CEMENTS AND CONCRETES

Sugar in Mortar. — ^Most writers have supposed that
the **01d Roman Mortars'' contained strong ale, wort,
or other saccharine matter, and it is probable that the
use of sugar with lime passed from India to Egypt and
Rome, and that malt or other saccharine ma-tter was
used in their mortars. The addition of sugar to water
enables it to take up about 14 times more lime than water
by itself. The following is an extract from the Roorkee :
**It is common in this country to mix a small quantity of
the coarsest sugar, *goor,' or *Jaghery,' as it is termed
in India, with the water used for mixing up mortar.
Where fat limes alone can be produced their bad quali-
ties may in some degree be corrected by it, as its influence
is very great in the first solidification of mortar. This is
attributed to the fact that mortars made of shell lime
have stood the action of the weather for centuries owing
to this mixture of Jaghery in their composition. Experi-
ments were made on bricks joined together by mortar
consisting of 1 part of common shell lime to 1^^ of sand,
1 lb. of Jaghery being mixed with each gallon of water.
The bricks were left for 13 hours, and after that time
the average breaking weight of the joints in 20 trails
was 6l^ lbs. per square inch. In twenty-one specimens
joined with the same mortar, but without the Jaghery,
the breaking weight was 41^ lbs. per square inch. ' '

The Madras plasterers make most beautiful plaster
work, almost like enamelled tiles, the shell lime being
mixed with Jaghery. The surface takes a fine polish
and is as hard as marble, but it requires a good deal of
patient manipulation. Dr. Compton has made some ex-
periments with sugar gauged with cements and mortars,
and says, ' ' That in medicine there are two kinds of lime-
water, one the common lime-water, that can be got by
mixing lime and water, and it is particularly noted

PLASTER, LIME, ETC. 89

that, add as much lime as you like, it is impossible to get
water to dissolve more than half a grain of lime in one
ounce, or about two teaspoonf uls of water. But by add-
ing 2 parts of white sugar to 1 part of lime, there is a
solution obtained which contains about 14j^ times more
lime in the same quantity of water. Here it is to be ob-
served— and it is a most important point — ^that there are
hot limes, such as Buxton, which if they be incautiously
mixed with them, will bum the sugar, make it a deep
brown color, and convert it into other chemical forms,
and possibly destroy its value in mortar.''

The Jaghery sugar used in India is sold in the London
market at about a penny a pound. Treacle seems to be
the most promising form of saccharine matter; beetroot
sugar is not good for limes or cements. There is a rough
unrefined treacle which is very cheap, and it is supposed
would have an excellent effect.

Herzf eld states that he used coarse stuff, consisting of
1 part of lime to 3 of sand, to which about 2 per cent.
of sugar had been added, to plaster some walls in the
new building of the Berlin Natural History Museum,
and on the day following he found the lime plaster had
hardened as if gauged with plaster. He also found it
useful in joining bricks, and recommends the coarse stuff
to be fresh made, and not with a great proportion of
water; and states that good molasses will yield as good
results as sugar.

Lime Putty, — This material is prepared in a similar
way to run lime intended for coarse stuff. It is run
through a finer sieve into a box or pit. If the latter is
used the interior should be plastered with coarse stuff to
prevent leakage and keep the putty clean. For good
work the best class of lump lime should be used. The
putty should be allowed to stand for at least three

90 CEMENTS AND CONCRETES

months before it is used. For common work the mmp
lime for making coarse stuff, putty and setting stiiflf is
often run into one pit. The putty at the end fax thest
from the sieve, being the finest, is retained for putty and
for making setting stuit, and the remainder, or coarser
portion, being used for coarse stuff. In many instances
the putty is left for months in an unprotected state dur-
ing the progress of the building, which is wrong. It may
be kept for an indefinite time without injury if protected
from the atmosphere, and therefore it should be covered
up to resist the action of the air, as it absorbs the car-
bonic acid gas and thus becomes slightly carbonated and
loses to a certain extent its causticity, and. consequently
its binding and hardening properties.

Pliny states that the old Roman limes were kept in cov-
ered pits. If a small portion is taken off the top of the
putty it will be found not only dry, but scaly, short and
inert ; whereas a portion taken from the middle, or up to
the part carbonated, will be found to be of an oily and
tenacious nature. A cute plasterer always selects the
putty furthest from the sieve for mitring purposes, as it
is the finest.

Setting Stuff. — This material is composed of lime
putty and washed fine sharp sand. The proportion of
sand varies according to the class of lime and kind of
work, but the average is 3 parts of sand to 1 of putty.
The various proportions are given where required for the
different works. Setting* stuff is used for finishing coat
of lime plastering. It is generally made on a platform
of scaffold boards, and sometimes in a bin. The putty
and sand are thoroughly mixed together by aid of a
larry. The sand should be sized by washing it through a
sieve having a mesh of the desired size. In some districts
it is made by pressing or beating the putty and sand

PLASTER, LIME, ETC. 91

through a ** punching sieve'' into a tub. Setting stuff is
less liable to shrink and crack, and is improved generally
if it is allowed to stand after being made until nearly
hard, but- not dry, and then ** knocked up'' to the re-
quired consistency with water (preferably lime-water)
and the aid of a shovQl and larry. While the stuff is
firming by evaporation it should be covered up to protect
it from dust and atmospheric influences. It should be
used as soon as ** knocked up." Setting stuff may be
colored to any desired tint, and also mixed with various
ingredients to obtain a brilliant and marble-like surface.

Haired Putty Setting, — Haired putty was formerly
used to a very considerable extent as a setting coat in
districts where the local lime was of a strong or hydraulic
nature, not very readily manipulated when mixed with
sand, as used for setting stuff. This material is com-
posed of fine lime putty and well-beaten white hair. The
hair was thoroughly mixed with»the putty to toughen
and prevent it from cracking. To such an extent was hair
added that in some instances the setting coat when
broken had the appearance of white felt. This class of
setting stuff is now seldom used.

Lime Water. — This water has many medicinal virtues,
and is a simple and inexpensive remedy for cuts and
bruises. Plasterers are generally healthy and free from
any infectious diseases. This may be partly owing to
their almost constant contact with lime. Lime water,
used as a wash, will harden plaster casts. It is also used
when scouring and trowelling setting stuff to harden the
surface.

Hair. — Hair is used in coarse stuff as a binding me-
dium, and gives more cohesion and tenacity. It is usu-
ally ox-hair (sometimes adulterated with the short hair
of horses). Good hair should be long, strong and free

92 CEMENTS AND CONCRETES

from grease or other impurities. It is generally obtained
in a dry state in bags or bundles. This dry hair should
be well beaten with two laths to break up the lumps, as,
unless the lumps are thoroughly broken so as to sepa-
rate the hair they are only a waste, and worse than no
hair at all^ since the lumps have no binding power and
will cause a soft weak spot in the plaster when laid.
Many failures of ceilings have been caused by the hair
not being properly beaten and mixed. Human hair is
sometimes used for jerry work. Goats' hair is often used
here. Hair is usually obtained direct from the tanners'
yard, fresh and in a wet state. This makes the best
work, as it is much stronger and mixes freely. Hair
should never be mixed with hot* lime, and with no mor-
tars until nearly ready for using, because wet or hot
lime weakens the hair, more especially if dry. Coarse
stuff for first coating on lath work requires more hair
than for brick or stoned work. When coarse stuff is made
in a will the hair should not be added until the stuff is
ground, as excessive grinding injures it.

Fibrous Substitutes for Hair, — ^Manila fiber as a sub-
stitute for hair in plaster work has been the subject of
experiments in this country. One of the' most conclu-
sive of these tests was made by four briquettes or plates
of equal size, one containing manila hemp, a second sisal
hemp, a third jute and a fourth goats' hair of the best
quality. The ends of the plates were supported and
weights suspended from the middle. The result showed
that plaster mixed with goats' hair broke at 144^/^
lbs. weight, the jute at 145 lbs., the sisal at 150, and the
manila at 195, in the latter case the hemp not breaking,
but cracking, and though cracked in the center, the lower
half of this plate, when it was suspended, held onto the
upper half, the manila securing it fast. The three other

PLASTER, LIME, ETC. 93

plates were broken — ^that is, the two parts of each plate
had severed entirely. Another experiment consisted in
. mixing two barrelf uls of mortar, each containing equal
portions by measure of sharp sand and lime, one of the
barrels, however, being mixed with a proper quantity by
measure of manila hemp, cut in lengths of 1^ to 2
inches, and the other of best goats' hair. On being thor-
oughly mixed with the usual quantity of water, the re-
spective compounds were put in the barrels and stored
a^ay in a dry cellar, remaining unopened for nine
months. On examination the hair mortar crumbled and
broke apart, very little of the hair being visible, showing
that the hair had been consumed by the action of the
lime,; but the other, containing the hemp, showed great
cohesion. It required quite an effort to pull it apart,
the hemp fiber permeating the mass and showing little
or no evidence of any injury done to it by the lime.

Sawdust as a Substitute for Hair. — Sawdust has been
used as a substitute for hair, also for sand in mortar for
wall plastering. It makes a cheap additional aggregate
for coarse stuff. Sawdust mortar stands the effects of
rough weather and frost when used for external plaster-
ing. The sawdust should be used dry and put through a
coarse sieve to exclude large particles. I have used it
with plaster for both run and cast work. It proved use-
ful for breaks of heavy cornices by rendering the work
strong and light for handling. Some kinds require soak-
ing or washing, otherwise they are liable to stain the
plaster. Several patents have been issued in America for

the use of sawdust in place of hair and of sand. One of
these is for the use of equal parts of plaster, or lime and
sawdust ; another is for the use of 4^^ parts each slaked
lime and sawdust to 1 part of plaster, l^ part of glue
and 1-16 part of glycerine, with a small part of hair.

/-
94 CEMENTS AND CONCRETES

Kahl's patent plaster consists of 35 per cent, of saw-
dust, 35 per cent, of sand, 10 per cent, of plaster, 10 per
cent, of glue, and 10 per cent, of whiting.

Sand. — Sand is the most widely distributed substance
in nature, not only in the mineral but also in the animal
and vegetable kingdoms. Clay contains no silica (the
chemical name for sand). Sand is the siliceous particles
of rocks containing quartz, production by the action of
rain, wind, wave and frost. Some kinds of sand are also
found inland; the deposits mark the sites of ancient
beaches or river beds. Sand is classed under various
heads, viz., calcareous, argillaceous and metallic. Sand
varies in color according to the metallic oxides contained
in them. Few substances are of more importance 4;han
sand for plastic purposes. Its quality is of primary im-
portance for the production of good coarse stuflf, set-
ting stuff, and for gauging with Portland or other
cements used for plaster work. Its function is to induce
the mortar or cement to shrink uniformly during the
process of setting, hardening or drying, irregular shrink-
age being the general cause of cracking. Sand is also a
factor in solidity and hardness; while being of itself
cheaper and used in a larger proportion than lime or
cement, it decreases the general cost of materials. There
are three kinds — pit, river and sea sands. They gen-
erally contain more or less impurities, such as loam,
clay, earth and salts, necessitating their being well
washed in water, more especially for the finishing coats
of plaster or cement work. Pit sand is sometimes found
quite clean; it is generally sharp and angular. River
sand is fine grained, not so sharp as pit sand, but makes
good setting stuff. Sea sand varies in sharpness and
size, and for plastering it should be washed to free it
from saline particles which cause eflBorescence.

PLASTER, LIME, ETC. 95

Regarding the use of sand in mortars, it may almost
be spoken of as a necessary evil. Sand is necessary to
give body and hardness to an otherwise too soft and
plastic material, and the coarser and cleaner the better,
as the coarse particles allow the carbonic acid to pene-
trate further into the body of the mortar, and assist in
the hardening process for this reason. In the case of
cements of all kinds sand is only good for lessening the
cost of the aggregate, and in the case of the majority of
sands in daily use in most places the strength is reduced
out of all proportion to the saving effected. Brunei, in
the Thames Tunnel, was so convinced of this that he used
pure Portland cement in the arches; and General Pas-
ley, treating of this, recommends that only pure cement
should be used on all arduous works.

As to the quality of sands, they are of very wide
variety— so much so, that 1 part of an inferior or soft
clayey sand will reduce the strength of mortar as much
as 3 or 4 parts of clean sharp granitic sand. This is well
exemplified in the sand test, which is made with what is
called standard sand, being a pure silecious sand sifted
through a sieve of 400 holes to the square inch and re-
tained on one of 900.

Good sand for lime plaster should be hard, sharp,
gritty and free from all organic matter. For coarse stuff
and cement for floating coats it should not be too fine.
Good sand for plaster work may be rubbed between the
hands without soiling them. The presence of salt in sand
and water is found not to impair the ultimate strength of
most mortars; nevertheless it causes an efflorescence of
white frothy blotches on plaster surfaces. It also ren-
ders the mortar liable to retain moisture.

Pine-grained sand is best for hydraulic lime; the
eoAnSe-grained is best iot fat iime^, and coarse stuffs and

96 ^^MENTS AND CONCRETES

Portland cements for floating. Sand should not be uni-
form in size, but, like the aggregate for concrete, should
vary in size and form. A composition of fine and coarse
sand for coarse stuff, unless the sand is naturally so
mixed, gives the best results, for as the lime will receive
more sand in that way without losing its plasticity it will
make a harder and stronger material, whether, coarse
stuff, setting stuff or for Portland cement work. If there
is plenty of fine sand and a scarcity of coarse sand, they
should' be mixed iQ the proportion of 2 of coarse to 1 of
fine. If on the other hand, there is plenty of coarse
sand and a scarcity of fine, they should be mixed in the
proportions of 2 of fine to 1 of coarse. The proportion of
sand varies ficcording to the different kinds and qualities
of limes and cements, also purposes. Baryte is some-
times used as a substitute for sand. Silver sand is used
for Portland cement work when a light color and a fine
texture is required.

Mastic. — Mastic was formerly extensively used foi
various purposes in which now Portland cement is chiefly
employed. It is still used sometimes for pointing the
joint between the wood frames of windows and the stone
work. Mastic is waterproof, heat-resisting and adheres
to stone, brick, metal and glass with great tenacity. . Mas-
tic is made in various ways. Some plasterers make their
own.

Scotch Mastic is composed of 14 parts of white or
yellow sandstone, 3 parts of whiting and 1 part of lith-
arge. These are mixed on a hot plate to expel any mois-
ture and then sifted to exclude any coarse particles. It
is then gauged with I'aw and boiled linseed oil in the
proportion of 2 of raw to 1 of boiled oil. The sandstone
is pounded or ground to a fine powdered state before

PLASTER, LIME, ETC. 97

being: mixed. The surface to be covered is first brushed
with linseed oil.

Common Mastic is prepared as follows: 100 parts of
ground stone, 50 parts silver sand or of fine river sand,
and 15 parts of litharge. These are all dried and mixed
and passed through a fine sieve; it then resembles fine
sand. This mastic may be kept for any length of time in
a dry place. When required for use it is gauged with
raw and boiled linseed oil (in equal proportions) until
of the consistency of fine stuff. It requires long and fre-
quent beating and kneading — in fact, the more it is
knocked up the better it works. Its fitness for use can
be ascertained by smoothing a portion of the gauge^with
a trowel. If there are any separate parts of the differ-
ent materials or bright spots seen the knocking-up must
be renewed until it is of even texture. The addition of 15
parts of red lead is sometimes used to increase the tenac-
ity of the mastic.

Mastic Manipulation. — The walls are prepared for
mastic by raking out the joints and sweeping with a
coarse broom, and the brick work well saturated with lin-
seed oil. Narrow screeds about 1 inch wide are formed in
plaster to act as guides for floating the work plumb and
level. When laying the mastic it must be firmly pressed
on and the fioating rule carefully passed over the" sur-
fiace until it is straight and flush. The screeds are next
cut out and the spaces filled in with extra stiff mastic.
The whole surface is then finished with a beech or syca-
more hand fioat, leaving a close and uniform texture.
Mastic moldings are first roughed out with Medina or
other quick-setting cement. The running mold is muflBed
so as to allow ^ inch for the mastic coat.

Hamelein's Mastic, — This mastic consists of sand and
pulverized stone, china, pottery, shard, to which are

98 CEMENTS AND CONCRETES

/ 1

added different oxides of lead, as litharge, gray oxide
and minium, all reduced to powder, .to which again is
added pulverized glass or flint stone, the whole being
intimately incorporated with linseed oil. The propor-
tions of the ingredients are as follows: To any given
weight of sand or pulverized pottery ware add two-thirds
of the weight of pulverized Portland, Bath or any other
stone of the same nature. Then to every 550 lbs. of this
mixture add 40 lbs. of litharge, 2 lbs. of pulverized glass
or flint stones, 1 lb. of minium and 2 lbs. of gray oxide
of lead.. The whole must be thoroughly mixed together
and sifted through a sieve, the flneness of which will de-
pend on the different purposes for which the mastic is
intended. The method of using is as follows : To every
30 lbs. of the mastic add 1 quart of linseed oil and well
mix together either by trestding or with a trowel. ; As it
soon begins to set, no more should be mixed at a time
than is requisite for present use. Walls or other sur-
faces to be plastered with this material must first be
brushed with linseed oil. /'

Mastic Cement, — ^Mix 60 parts of slaked lime, 35 parts
of fine sand and 3 parts of litharge, and knead them to
a stiff mass with 7 to 10 parts of old linseed oil.' The
whole mass must be well beaten and incorporated until
thoroughly plastic. This mastic cement assumes a fine
smooth surface by troweling. It is impervious to damp
and is not affected by atmospheric changes.

TERMS AND PROCESSES.

The following descriptions are suited to most locali-
ties, though there are districts in the East and South
that vary somewhat from the processes as described;
the difference,* however, is so trifling that the regular
plasterer will have no trouble in reconciling such differ-
ences.

. Three-Coat TTorfc.*— Three-coat work is usually speci-
fied by architects for all good buildings, but sometimes
two-coat work is specified for inferior rooms, closets, at-
tics or cellars in the same building. Three-coat work
makes a straight, smooth, strong and sanitary surface for
walls and ceilings when properly executed. The follow-
ing is the process for three-coat work^ which consists of
first-coating, floating and setting.

First-Coating. — ** First-coating'* is termed in the
United States ** scratch-coating." It is executed by lay-
ing and spreading a single coat of coarse stuff upon the
walls and ceilings to form a foundation for the subse*
quent floating and setting coats. Coarse stuff for first-
coating should be uniformly mised or **k^nr»lrp/^ ^ip^ ' ' as
commonly called. It should contain more hair than that
used for floating, so as to obtain a strong binding key on
the lath-work and form a firm foundation for the float-
ing coat. Coarse stuff may be tested by lifting some
from the heap on the point of a trowel. If it is suffi-
ciently haired and properly mixed the stuff should cling
to the trowel when held up and the hairs should not be
more than 1-16 inch apart. It should be stiff enough to
cling and hold up when laid, yet sufficiently soft and

100 CEMENTS AND CONCRETES

plastic to go through the interstices between the laths.
Unless the stuff is made to the proper consistency it will
**drop'' — ^that is, small patches where the excess water
accumulates or at weak or too wide spaced laths will fall
soon after being laid.

When first-coating ceilings, the coarsfi-stiiff should be
laid diagonally across the laths,. a trowelful partly over-
lapping the previous one, the one binding" the other. By
laying the stuff diagonally the laths yield less, present a
firmer surface and are not so springy as when laid across
or at right angles to them. Laying the stuff diagonally
and overlapping each trowelful helps to retain the stutf
in its place, which otherwise is apt to ''drop.'' The stuff
should be laid on with a full-sized laying trowel, using
suflScient pressure to force it between the laths and to
go sufficiently through to form a rivet and lap or clinch
on the upper sides of the lathing. The stuff should be
laid fair and as uniform in thickness as possible. The
thickness should not exceed % inch or be less than %
inch. If too thick it tends to weigh down the lath work
and is apt to crack ; if too thin the subsequent scratching
is liable to cut the coat down or nearly to the laths, thus
leaving a series of small detached pats which* are un-
stable and form a weak foundation for the floating coat
and are a source of cracks and often the cause of the
work falling when subjected to vibration. A thickness
of ^ inch gives the best results.

Ssiai^akMxtg, — Scratching is sometimes termed "scor-
ing,'' also ''keying." It is done with a wooden or iron
scratch, which may have from one to five points.
Scratching is scoring the surface of the first coat to
obtain a key for the following coat. The first-coating
should be allowed to stand for an hour or two to allow
the stuff to get firm before proceeding with the scratch-

TERMS AND PROCESSES 101

ing. If scratched while the Istuff is soft it is apt to drop,
and unless a man is careful and light in his working the
scratch will go too deep and weaken the body and the
rivets of first-coating. A wide scratch should be slightly
angular at the points; if square, it should be drawn
across the work in a slanting position so as to give an
undercut key. The whole of the surface should be uni-
formly scratched with a moderately sharp pointed
scratch. The surface should be cross-scratched diag-
onally. Square scratching cuts and weakens the rivets,
especially when the scratch is drawn in the same line as
the laths. Good work is generally scratched with a sin-
gle lath. This, like other scratches, should be drawn in
a slanting position, so as to give an undercut score. Sin-
gle scratches is the best way for circular surfaces. First
score it diagonally across the laths and then crossways
diagonally, keeping the scoring rather square than loz-
enge-shaped. When too pointed the acute angles are
liable to be broken when laying the floating coat. The
scores should not be more than ll^ inch from center to
center, or less than one inch from center to center. Close
scoring weakens the body of the first-coating, while wide
scoring affords insufiicient key. Scratching with a single
lath requires thrice or even more tinie than if done with
a four or five pointed scratch, but the work is stronger,
as the body and the rivets of the first coating are- not
cut too deep or otherwise weakened. In some instancies —
such as a thin body of first-coating already mentioned — ■
the scoring is so deep that the body of the work is cut
into a series of detached parts. By using a single lath
or point the scoring is also more uniform and better un-
dercut, thus obtaining a stronger surface and a better
key for the floating coat. The additional time required
for ** single scratching" should be taken into considera-

102 CEMENTS AND CONCRETES

tion, and annotated and allowed for when making speci-
fications and estimating. All scratching should be done
uniformly, taking care not to miss any parts, especially
round door and window frames, wood grounds or where
there may be jarring or vibration. On the regular and
proper scratching depends the key and stability of the
succeeding coats. Scratching with the point of a trowel
should not be permitted. The use of a trowel as a
scratch is detrimental to the strength of the stuff and the
key. The sharp edge of the trowel cuts the hair and
thus weakens the stuflf. The smooth and thin plate of the
trowel leaves a smooth and narrow key; the smooth side
of the key presents no attachment for the second coat,
while the deep part of the key is too narrow to receive
its due portion of stuff to fill it up, thus leaving a space
for contained air and a more or less hollow and unsound
body.

Rendering. — The first coat on brick, stone or concrete
walls is called rendering. Before laying the coarse stuff
the superfluous mortar in the joints of brick or stone
walls should be cleared off, as the mortar used by brick-
layers and stonebuilders often contains live or imper-
fectly slaked lime, which in many instances is the cause
of the plaster work blowing or scaling off. The walls,
whether of brick, stone or concrete, should be well swept
with a hard coarse broom and thoroughly wetted to cor-
rect the suction, which otherwise would absorb the requi-
site moisture from the coarse stuff, causing it to become
inert and dry, consequently weak and non-adhesive. In
some cases the joints of brick-work should be raked out
and the face of stone walls roughened by picking. The
coarse stuff for rendering walls does not require so much
hair or to be used so stiff as for coating lathwork. Pirst-
coating or rendering is generally looked upon as a simple

TEEMS AND PROCESSES 103

process, but it should be carefully laid and scratched, as
it is the foundation for the other work.

Floating. — ^Floating or second-coating, termed ** brown-
ing," is the laying of the second coat of coarse stuff on
the first coat when dry to' form a straight surface for the
finishing coat. If the first coat has been standing for
some time it should be well swept to clear off any dust
that may have accumulated during the interval between
the application of the coats. "Where the coarse stuff is of
a porous nature a damp brush should be passed lightly
over the first coat as the work proceeds to prevent the
moisture being sucked out of the second layer, which, if
too dry, would tend to crack and fall away. The coarse
stuff for floating should be used in a softer state than
for first-coating, because when too stiff the extra press-
ure required for laying is apt to crack the first coat on
lath work. It also goes more freely and firmly into the
recesses of the scratching. (It may be here mentioned
that a mortar called **dogga'' is extensively used in
South Africa for plaster and building work. Dogga is
the ground dug up and tempered with sand, about 2 to
1 for rendering and floating. Heavy ground requires
more sand. Lime is very expensive in that country and
is only used for the best class of work.) Floating for
lime plastering consists of four parts: (1) Plumbing
and levelling ** screeds" to act as bearing for the floating
rule and running mold; (2) flanking or fllling in the
spaces between the screeds ; (3) scouring; (4) keying the
surface. These parts are performed as follows :

ScreedsA — In good work the wall screeds are plumbed
and the ceiling screeds levelled.* Wall screeds are
plumbed by forming **dots" at the top and bottom of
the internal and external wall angles. If there are wood^
grounds to receive wood skirtings they are used instead

104

CEMENTS AND CONCRETES

42SS^kS&M^>

NO. 3.

of bottom dots. The dots are made by
driving two nails through, the first coat
into the studs or joints of the wall,
allowing them to project about ^/^ inch
beyond the face of the^first coat. The
position of the top nail should be imme-
diately beneath the cornice bracket. If
there is no bracket the depth of the
cornice should be allowed for. The
bottom nail is placed in a liije with the
upper member *of the skirting molding.
The nails should be pla(!ed perpendicu-
lar with each other, otherwise the
plumb-bobline will not worl^ in unison
with the gauges. The dots are plumbed
by means of a plumb-rule. If the walls
are too high for an ordiuary sized
plumb-rule to be used a chalkline, with
a plumb-bob attached, and two wooden
gauges will be required. Illustration
No. 3 shows the nails, gauges and
plumb-bobline in position. BB are the
nails in the wall, one just below the
cornice bracket and the other a little
above the floor line; AA are the gauges
with the line- hanging fair with their
shoulders, being the correct position
when the nails are plumb. The gauges
are generally cut out of a strong lath.
They must be made exactly to the same
length. The plasterer at the top holds
the end of onp gauge on the top nail,
with the chalk-line resting on the shoul-
der of the gauge, while the plasterer

TERMS AND PROCESSES lOi

at the bottom holds the other gauge on the bot-
tom nail with one hand and guides the plumb-bob
with the other. The nails are now driven in as re-
quired until they are plumb. Care must be taken to
allow for a fair thickness for the floating coat. This
should not be more than % inch or less than % inch.
When working from a wood ground the top dots should
be kept a little inside the plumb-lhae to allow for the
traversing of the cornice screed, because this screed and
the gathering at the bottom of the cornice are apt to
throw the wall out of plumb unless cut oflf or allowed for.
The dots are completed by laying narrow strips of
gauged coarse stuff up to and in a vertical line with the
top and bottom nails; the floating rule is then applied
and the stuff worked down until flush with the nails. The
dots should not be wider than the width of the floating
rule, as the rule when bearing on the nails can only be
worked with an up-and-down motion, taking in only its
own width. The length of the dots may vary from 5
to 7 inches, according to the bearings required for the
cornice and skirting running mold. Narrow screeds are
easier, quicker and truer made than wide screeds. The
latter are apt to have a more or less wavy surface. This
applies more especially to **laid screeds" — ^that is
screeds that are simply laid and ruled off without dots
or other bearings.

Lath dots are sometimes used instead of nail dots ; they
are generally used on ceilings and lathed partitions ; they
are not so liable to crack the first coat as nails. They
are formed by laying a strip of coarse stuff and placing
thereon a straight lath about 6 inches long and then
applying a plumb-rule or plumb-bobline as described
for the nail dots. The lath gives strength and resist-
ance while working the floating rule. After the screeds

106 CEMENTS AND CONCRETES

are finished the laths are taken out and the spaces made
good. Having finished all the top and bottom dots, the
top and bottom longitudinal spaces in a line with the
dots, or, in other words, the screeds are laid with coarse
stuff. The long floating rule is then applied, bearing on
the dots and working up and down in a slanting posi-
tion, a plasterer working the rule at each end, and work-
ing together so as to keep the rule square on edge and
uniformly level. . Any surplus stuff is taken off the rule
and applied to make up any hollow parts in the screed
or returned to the gauge board, as the case may be. If
the screeds are extra long another man (sometimes more)
is required to wojrk at the center of the rule, also clean
the surplus stuff off, and make up any deficiencies in the
screed. After the screeds are finished, the nails must be
extracted to avoid rust discoloring the finishing coat.
Large surfaces on walls or ceilings should be divided in-
to bays by narrow screeds placed from 6 to 9 feet apart.
This affords more freedom and regularity for laying and
ruling off.' Gauged coarse stuff is sometimes used for
the main screed, i. e., the wall and ceiling screeds on
which the cornice is gnin. In this case the screeds are
finished smooth, or so*that they only require a very thin
or filling-up coat of gauged putty for the cornice screeds.
The splayed edges of screeds, especially gauged screeds,
should be cut square. A splayed edge being generally
smooth, affords little or no key, and also being unequal
in thickness, makes a bad joint for the floating coat.
If there are any breaks in the room, the screeds must be
set off square from the side walls, and the projections
at each angle of the breast made equal. The sides are
best squared with a large wooden square, and the pro-
jections regulated with a gauge.
Flanking, — Planking or filling in consists of laying

TERMS AND PEOCESSES 107

the intervening spaces between the screeds with coarse
stuff, and then ruling the surface straight and flush with
the screeds, with a floating rule. Two squads of men, two
or three in each squad, are required for this purpose —
one squad on the floor, and the other on the scaffold. If
the height of the room necessitates more than one scaf-
fold, an additional squad is required for each interven-
ing scaffold. In the latter ca^e, the distance between the
top and bottom screeds would be too great to allow a
floating rule to be conveniently worked. To overcome this
difficulty, intermediate screeds must be made at conven-
ient distances} This is done by stretching a chalk-line
from the top to the bottom screed, and then forming dots
flush with the line, and laying the screeds as previously
described. The coarse stuff for flanking should be laid
upwards, and in an angular line. This plan is not so apt
to spring the lath or crack the key at the deepest, which
is the thinnest part of the flrst Ct)at, as if laid across the
laths. After a bay is laid, the surface is straightened *
with a floating rule. A plasterer at the top and one at
the bottom works the rule together uniformly up and
down with a cutting motion, and keeping it in a slightly
angular position, so that any surplus stuff may not fall
on the man below! A rule should not be worked on
either of its face edges, as by so doing the face becomes
round and uneven, and conducive of unequal screeds.
The filling in and ruling off is continued until all the
walls are completed. When elaborate ceilings have to be
done, involving the expenditure of much time, the top
longitudinal screeds are only formed, and the floating of
the walls left until three or four (feiys before the setting
can be begun, as the setting coat made from some limes
adheres better when the floating coat is partly green, or
at least not bone dry. As previously mentioned, the

108 CEMENTS AND CONCRETES

whole process of preparing lime plaster and laying it on
the walls in thin coats, with a considerable space of time
between the coatings, is conducive to the ultimate hard-
ness of the whole, the lime being first slaked and then
scoured, all this time being exposed to the carbonic acid
of the atmosphere. Again, each coat is long exposed to
the same influence before being covered with the next,
thus enabling each coat to harden by a natural process
before the following coat is laid. All things being equal,
it is advisable to allow each coat to stand as long as pos-
sible before proceeding with the next. ' Where the wall
surface is irregular, causing extra thick parts in the
floating coat, the hollow parts should be rendered or
** dubbed out," and the surface scratched before la>dng
the floating coat. The dots for the ceiling screeds are
formed close to the cornice bracket. If there are no
brackets, the projection of the cornice must be allowed
for. Lath dots are best for ceiling screeds. They are
formed at all the angles, and made level all round the
ceiling. This is done with the aid of a ** parallel ceiling
rule." When all the dots are made, the screeds are fin-
ished, and the surface flanked in as already described.
For common work, the wall screeds are seldom
plumbed; but if there are breaks in the room, the ex-
ternal angles, which are more noticeable, should always
be plumbed. For this class of work two men generally
work together. Working from the floor upwards, one
man lays a coat of coarse stuff about 7 inches wide, and
as high as he can conveniently reach up on both sides of
the internal angles ; his colleague follows on with a float-
ing rule and rules them straight. Before finishing the
screed, the rule is applied on the portion done, and grad-
ually moved up until one end reaches the cornice line,
to see if there is a sufScient thickness for the upper part

TERMS AND PROCESSES 109

of the screed. The space between the first-coating and
the face of the rule shows the thickness available for the
floating coat. The desired thickness is obtained by lay-
ing more stuff on the screed, or working it down, as
the case may be. As the floating rule cannot be worked
close up to the angle, a seam of coarse stuff is formed in
the angle.

To allow for shrinkage, and to obtain a firm and
square angle, the seams are left until all the floating is
done, after which they are cut off square and flush with
the floating. This is done with a laying trowel, w irking
it on its flat on the firm floating. Any defects in the
angles are made good when scouring the float-
ing. After the vertical angle screeds are firm,
horizontal screeds are laid at the highest conven-
ient line, and ruled with a floating rule bearing
on the vertical screeds. The intervening spaces are then
flanked in by laying with coarse stuff until flush with
the screeds. The surface is sometimes ruled fair with a
floating rule, but more often straightened with a darby.
After the scaffold is erected, the top portions of the ver-
tical screeds are laid and ruled with a floating rule,
working it so as to bear on the lower part of the screed
previously made, which gives a bearing and guide for
the rule. After allowing for the depth of the cornice
(if not bracketed), the top horizontal screed is then
laid and ruled with a floating rule bearing on the ver-
tical screeds. The intervening spaces are then filled in
with coarse stuff, and ruled in or, darbied as previously
described. The ceiling screeds are made close to the cor-
nice bracket, or (if not bracketed) in a line with the
outer member of the intended cornice. A screed is first.
made at each of the long sides of the ceiling, and when
firm the end screeds are laid and ruled, using the long

110 CEMENTS AND CONCRETES

screeds as bearings for the floating rule. If the scaffold
is in position before the floating is commenced, the
vertical screeds should be formed in one operation. A
plasterer on the floor lays the lower part of the screed,
while his partner on the scaffold lays the .upper part,
after which both work with floating rule together in
their respective positions. Where practical all screeds
should be finished in one operation. In the event of a
screed being too long for an ordinary sized rule to take
in the whole length and work it in one operation, the
screed can be made straight by working the rule back-
wards and forwards from end to end, testing the
straightness by applying the rule on various parts of the
screed. The straightness is further proved by lightly
stretching a chalk-line from one end to the other end
of the screed. After the screeds are firm, the main
portion of the ceiling is laid with coarse stuff flush with
the screeds, and thea made fair with a darby.

When floating large surfaces with a darby, it should
be worked in all directions — longwise, crosswise, and
diagonally and finishing with a circular motion. For or-
dinary work a darby is an excellent tool for straighten-
ing large surfaces of floating and setting. It also forms
a pleasing and easy surface on circular work. For base-
ment and attic rooms a darby properly manipulated will
form fairly straight screeds as well as the main surfaces.
When floating large ceiling or wall surfaces for plain
work, or where it is not necessary that they should be
perfectly straight, involving time and material, a hol-
low surface is preferable^ to a round surface. A hol-
low surface is liot so. noticeable, and is less objectionable
to the eye than a round surface. It will be understood
that a hollow surface, to be pleasing to the eye if noticed,
should flow gradually and regular from the screeds to

TERMS AND PROCESSES 111

the center of the surface, and not suddenly or in wavy
parts or patches. ,

There is an inferior kind of floating practiced by
piece-workers, in some districts, for cottage work, and
even some of the modern jerry-built- houses. This is
executed by floating direfet ^irr*?the walls in one coat.
The surface is^sometimes dry-scoured with a **nail hand
float," water and proper scouring beipg unknown in this
class of so-called plastering. The ceilings are simply
laid with coarse stufl:, and the ridges and smooth sur-
face left by the trowel are worked down and roughened
by a few rubs with a hand float. This porous and cracked
shdl is finished with setting stuff, gauged with just as
much plaster as will hold the materials together for the
time being. The minimtim of (or possibly less) trowel-
ling is attempted; a stock brush being found a morej
easy and speedy tool than a trowel for finishing. The
brush is made to perform the trowelling and brushing
off in one operation. This shoddy work is unsafe and
unsanitary, and ought not to be tolerated.

Scouring Coarse Stuff, — Scouring floated coarse stuff
is of great importance. It not only consolidates and
hardens the surface, but also prevents cracks in its own
body and the subsequent setting coat. For these reasons
it should be well and sufficiently done. The straightened
coarse stuff should be allowed to stand to permit of
shrinkage, evaporation of surface moisture, and a firm
surface before proceeding with the scouring. Working
a hand float on a soft surface tends to form *' water
blubs" and hollow parts* When the surface is firm,
but not dry, the work is fit to scour. This is done by
the plasterer having a hand fioat in one hand, and a
stock brush in the other, with which he sprinkles watei^
on the surface, and vigorously applies the float with a

112 CEMENTS AND CONCRETES

rapid circular motion, using a little soft stuff to fill up
any small holes or inequalities that may have been left
after the floating rule. Care must be taken that no part
is missed or less scoured and that the whole surface is
thoroughly and uniformly scoured. The floating should
be scoured twice, or for best work three times, and allow-
ing the work to stand from three to five hours, accord-
ing to the state of the atmosphere, between the first and
second scouring, and one day between the second and
third scouring. The final scouring should be continued
until there is little or no moisture left on the surface.
To obtain the same strength and solidity, all other things
being equal, coarse stuff composed with a weak lime or
containing inferior or an excess of sand, or having in-
sufficient hair, or sparsely tempered and used in an
over-soft condition, requires a greater amount of scour-
ing than coarse stuff which is Composed with a strong
lime, or containing good sand and in due proportion, or
with an ample quantity of hair, or well tempered, and
used in a moderately stiff yet plastic condition. Even
with extra scouring the ultimate strength of inferior
coarse stuff is remote and doubtful. This simple mat-
ter is a witness to the fact that inferior or insufficient
materials require more labor than good and sufficient
materials and that the results are somewhat vague and
often unsatisfactory.

Keying, — ^AU plastic materials • have great adhesive
powers, especially to each other. Yet when laying a thin
body of fine material on a coarse material which has a
more or less smooth, dry and absorptive surface, such as
laying setting stuff on floated coarse stuff, the adhesion
is partly nullified. Portland cement or hydraulic limes,
which set nearly as soon as laid, require no scouring, and
being left from the floating rule with an open grained or

TERMS AND PROCESSES H3

rough surface, a natural key is obtained for the final
coat; but coarse stuflf, which only sets or becomes hard
by evaporation of its moisture, must be scoured to con-
solidate the yielding and soft body.. Scouring leaves a
close-grained and somewhat smooth surface, offering lit-
tle or no key to the setting coat. The floated coat being
often dry before the setting coat is applied, the suction
varies greatly ; sometimes it is regular, at other times it
occurs in patches. Sometimes the suction is so excess-
ive that the setting stuff dries up and peels as soon as
laid, and in other instances the reverse occurs, there
being no suction at all. In the latter case the setting
stuff runs downwards in the form of globules or in rivu-
lets^ These defects may to a certain extent be corrected
by laying the setting stuff while the floating is still
green, or by saturating the surface if the floating is dry.
Yet to obtain permanent cohesion in the two coats it is
necessary to key or roughen the surface. This is best
done by brushing the surface as soon as scoured with a
stiff whalebone broom or with a wire brush. A common
plan is to dry scour with a "nail float" — i. e., a hand
float with the point of a nail projecting about % inch
beyond the sole of the float. When this method is em-
ployed the float should be worked in a close circular
motion so as to leave a series of close and irregular in-
dents. The usual and careless way of working the float
in a wide circular motion leaves the indents too wide
apart to give a sound and uniform key; indeed, this
method is of little service. A new tool for keying coarse
stuff has been recently introduced, which is called a
** devil" and is similar to the nail float, with the excep-
tion that there are four nail points projecting on the
sole, one of which is placed about 1^^ inches from each
angle. The process of keying the coarse stuff with this

114 CEMENTS AND CONCRETE^

is termed ''devilling." The work is more speedily and
better done with the ''devil" than with the nail float.

After the floating is finished the next part of interior
plaster work is the running of the cornice, and then fin-
ishing the ceiling and walls; but in order to continue
the methods of setting, the running of the* cornice, etc.,
are described in subsequent pages, and the setting and
other parts of wall work are first described as follows :

Setting, — Setting is the laying and finishing the final
coat on floating, termed "flnishing," and "hard finish"
or "putty coat." In the best work great skill and care
is required to make the surfaces perfectly true and uni-
form in color, smoothness and hardness. The material
for three-coat work is generally known as "setting
stuff." The mode of making has already been de-
scribed. Setting stuff should ^not be applied until the
floating is quite firm and nearly dry, to allow for any
contraction that may take place in the floating. ^ If the
floating should become quite dry during the time re-
quired for cornice and ceiling work, or where subjected
to strong winds or a warm atmosphere, it should be well
wetted a day or two before the setting coat is com-
menced. This prevents the too rapid absorption of mois*
ture from the setting coat and gives a closer union of
the floating and setting coats. Before wetting copi-
ously, a small portion of the floating should be tested
with a wet brush to ascertain the degree of suction. In
some floating there is no suction, or at least there is
none until the surface has been dampened and the glaze
and sometimes grease has been washed off. Glaze is
caused by slightly hydraulic lime, also by insufficient
scouring. Glaze is more noticeable on first-coating
which has been left smooth by the laying trowel. Grease
occurs through friction, also dirt where the float is left

TERMS AND PROCESSES 115

long exposed. These matters of excessive and non-
suction, dry, glazed or greasy surface, either singly or
in combination, also smooth or unkeyed floating, are the
cause of cracked or scaly setting, which one sees more or
less in a plaster career. It is therefore absolutely neces-
sary, to insure perfect cohesion of the two coats, that
the floated surface should be uniformly keyed, clean and
damp before the setting coat is layed. Setting consists
of laying the stuff, scouring, trowelling and brushing the
surface.

Laying Setting Stuff a — The setting stuff is laid in two
coats, the second following immediately upon the first.
The laying is best done with a skimming float, which
leaves the face of the first coat rougher to receive the
second than if done by a laying trowel, which leaves it
smooth. The second coat should also be laid with a
skimming float, which leaves a more open grain for the
purpose of scouring. When laying setting stuff some
men take a trowelful or skimming-floatful off the hawk
and stoop to spread the stuff from bottom to top with
an upward motion, laying the joint with a return down-
ward motion; but a smart man can take a trowelful or
floatful of stuff and spread it with a downward motion
from top to bottom and lay the joint with the return mo-
tion, this saving one stoop in each spread or floatful.
This is similar to laying setting stuff on a ceiling. A
man who has a thorough command of the trowel hand
always lays the stuff in a long even spread outward,
and lays the joint with the inward return motion. After
one side of a bay or wall is laid the surface is then
scoured, trowelled and brushed.

Scouring Setting Stuff, — The importance of good and
suflScient scouring of setting stuff with water cannot be
too strongly insisted upon. The scouring and the water

116 CEMENTS AND CONCRETES

combined consolidate, harden and render the surface of
a uniform texture and evenness. The work must be well
and thoroughly scoured^ twice with water and an ordi-
nary hand float and finally with a cross-grained float.
The hand flcat is worked with a short and rapid circular
motion and sprinkling water uniformly with a stock
brush until the surface is uniform in moisture and tex-
ture. After a rest to allow the stuff to shrink the scouring
is repeated, and then it is ready for the final scouring.
This is best done with a cross-grained hand .float, which,
liaving sharp square edges, cuts off all ridges and leaves
the setting with a uniform and even surface that cannot
be so quickly or as well done with an ordinary hand float.
Water is more sparingly used for the final , scouring,
using only as much as will moisten the surface and allow
the float to work freely. The scouring is continued until
a dense, even and close-grained surface is obtained for
the trowelling.

Trowelling and Brushing Setting Btujf, — Trowelling
setting stuff is best done by the use of a half worn
trowel (commonly called a ** polisher''), the edges of
which should be perfectly straight and parallel. Some,
men use an old and worn trowel with the point narrower
than the heel. This shaped trowel should never be used
for high class work, since, not being parallel, the press-
ure when trowelling is not equal, and the heel or widest
part is apt to score the surface of the setting. The
trowel and water should be perfectly clean to prevent
any discoloration. The trowelling should be done by
one man following up the other, who is finishing the final
scouring. This is done by the plasterer having a polish-
ing trowel in one hand and a stock brush in the other,
with which he sprinkles water on the surface and works
the trowel in long and vigorous strokes, first downwards

TERMS AND PROCESSES 117

and upwards, and then crossways or diagonally. This ia
repeated, using the water more sparingly and finishing
or ''trowelling off with an up-and-down motion and
leaving the surface free from **fat'' or **glut/' The
work is then brushed with a wet stock brush, first up and
down, then crossways, afterwards up and down a sec-
ond time. The brush is then semi-dried by violent shak-
ing, or rubbing on a clean board, the work again being
brushed as before and finished perpendicular.

General Remarks on Setting, — ^When ^the work is re-
quired for painting the setting stuff is laid on the form
of screeds, and when firm the intervening spaces are
laid fiush with the screeds and the whole surface ruled
fair with a fioating rule. Should there be any hollow
or soft places (the latter being liable to shrink), they are
filled in with more setting stuff and ruled over again.
This is repeated until the whole surface is true and uni-
form in thickness and firmness. The whole surface can
be scoured, trowelled and brushed in one operation.
This method has the advantage of saving joints at the
connections between the height a man can lay and finish
the setting stuff.

Joints, unless carefully done, are an eyesore, as they
are liable to be more or less discolored and uneven on
the surface.. The best method for making joints and
setting stuff, where it is inconvenient to lay and finish
the whole surface in one operation, is to leave the edge
of the joint untrowelled, leaving a scoured margin so
that the adjoining portion can be laid and scoured with-
out spoiling the trowelling of the first portion. For in-
stance, when setting the walls of a room one scaffold
high the top parts are laid down to the level of the
scaffold, or as far as convenient, and the surface scoured
and trowelled. The latter must not extend to the en<^

118 CEMENTS AND CONCRETES

of the scoured part, so as to leave an untrowelled margin
about 4 or 5 inches wide until the scaffold is struck.
After the scaffold is removed the lower portions of the
walls are laid flush with the untrowelled margin, and
then the surface is scoured as before, always going well
over the joint. The surface is then finally scoured with
a cross-grained float, taking care to moisten and rescour
the untrowelled margin to render the whole of the
scoured surface equal in texture and moisture for trowel-
ling. The surface is then trowelled and brushed as al-
ready .described, taking care to go over the trowelled and
brushed joint. By this method no joints are visible, and
an even surface is obtained. When the suction is slow
or irregular, causing the setting stuff to run or be soft
in places, float the surface with a darby until sufficiently
fair and firm to be scoured. A darb}" is very useful for
forming a fair surface on setting stuff before scouring
and trowelling. It forms the next best surface to a
ruled surface. A darbied surface is better and truer
than a laid surface.

No more setting stuff should be laid than can be con-
veniently finished in one operation or day. Where prac-
tical, one side of a wall should be finished in one piece,
•and sufficient men should be employed thereon. If the
room is not too high, one man or set of men may do the
upper part, while another man or set of men does the
lower part. The joints are then made while the setting
stuff is green. In high rooms, several sets of men work
together on different scaffolds, each about 6 ft. 2 in.
apart. All angles should be ruled in with a long float-
ing rule. External angles are sometimes formed by
nailing a running rule or a straight edged plumb on one
side of the wall, to act as a guide, but external angles are
generally finished with a run cement bead or an arris.

TERMS AND PROCESSES 119

An average thickness of % inch of setting coat when
finished gives the best result. It should not exceed 3-16
inch, or be less than* 1-16 inch in thickness. If too thick,
it is liable to crack and flake; if too thin, it is liable to
peel. Where extra strength, and c(ihesion between the
floating and setting coats is desirable, the first coat of the
setting has a little white hair mixed with it. White hair
does not show through the last coat.

Common Setting. — Common setting for wall and ceil-
ings is generally used for second-class work. It is done
by laying one coat of setting stuff with a skimming float,
and scouring and trowelling once and brushing twice.
Where the floating cracks by contraction, or by using in-
sufficient hair in the coarse stuff, or by want of scouring,
or where the work is green, the cracks are knocked in
with a hammer. The indents are then filled up with
gauged setting stuff, and the whole surface laid with a
coat of this material, on which a coat of neat setting stuff
is laid, scoured, trowelled, and brushed in the usual
way.

Skimming, — Skimming is an inferior class of setting,
and is only used for the most common work. It is done
by laying a coat of fast-setting stuff with a laying trowel.
The stuff is skimmed over the floating as thin as possible,
using only as much stuff as will whiten and smooth the
floating surface. It is trowelled once, and brushed as
soon as laid.

Colored Setting, — ^A beautiful color and brilliant finish
for walls is obtained by mixing an equal quantity of
sifted marble dust with setting stuff and using this
** marble setting stuff'' as a final coat. Ordinary setting
stuff is greatly improved by substituting a part of mar-
ble, or alabaster, or gypsum dust, equal in bulk to half
the sand generally used. The marble dust should be as

laO CEMENTS AND CONCRETES

coarse as the sand. Crushed spar is sometimes used in
setting stuff to obtain a sparkling surface. Barytes, ^o-
ria, and slag are sometimes used as a substitute for sand,
for coloring and hardening purposes. Brick dust is also
used for coloring, and weather and heat resisting pur-
poses. Ground glass as used by Indian plasterers gives
a sparkling surface. Setting stuff may also be colored
with the same materials as described for colored stucco.
Where marble dust or any of the above materials are
used, they should not be added until the setting stuff is
required for immediate use. They should not be used
until perfect amalgamation has ensued.

Gauged Setting, — Gauged setting is used where the
floating is soft, or where the work is required for imme-
diate use, and also for finishing gauged floating. This
is performed by one man laying the gaugied stuff with
a skimming float, while his partner follows up with a
darby to lay the surface fair. Another batch of setting
stuff is then gauged, and one man lays a thin coat with
a trowel, and the other man follows immediately and
trowels the work before it is set. The surface is finished
by brushing with a semi-wet brush. Gauged setting
should never be scoured unless the size water is used in
the gauge to delay the setting, as it will kill the plaster
and render the stuff useless. Even if size water is used,
the scouring must be slightly and quickly done. If a
gauged surface is desirable, a fair and hard surface is
obtained by simply darbying and trowelling as soon as
laid.

Gauged Putty SetA — Ceilings are sometimes set with
gauged putty. This is best done by first laying a
** scratch coat'' of gauged putty with a skimming float,
and then passing a hand float over the surface (before
the stuff is set) to lay down any ridges, and make the

TERMS AND PROCESSES 121

surface more even to receive the second coat. This is
laid with a laying trowel, and then trowelled before the
stuff is set. The surface is then finished with a semi-wet
brush. Trowelling after the stuff is set, or even has
begun to set, kills the stuff, and causes it to peel. A
little washed sand added to the putty makes a stronger
surface, and not so apt to peel.

Putty Set. — In some districts common ceilings are fin-
ished with a thin coat of neat lime putty ; but unless the
putty is made from grey limestone, or is of a hydraulic
nature, the work is more or less weak, and in most cases
practically useless.

Internal Angles. — The setting coat of internal angles
on room walls should be ruled fair and th.en cleaned out
with a feather-edged rule: Before scouring the setting
stuff, the angles should be squared and made straight
with an angle float. The angle float is a tool now unfor-
tunately seldom used, but it is the best tool for making
a true angle. In the absence of an angle float, the angle
should be made fair and square with a cross-grained
float, and finished with a margin trowel or the heel of a
laying trowel. The common way, used in some districts,
of finishing an angle with a gauging or pointed trowel,
should not be encouraged, as it is impossible to make a
true angle with a tool of this shape.

External Angles. — The external angles of room walls
and windows are generally finished with a bead, but in
some instances with a plain arris, splay, or small mould-
ing. They are formed with Parian or other white
cement, and usually run after the floating is done. The
floating should be cut square on each side, and down to
the brick or lath work. After dusting and wetting the
foundation, a running rule is flxed on one side, and then
the bead or arris is run. The run efdges form bearings

:22 CEMENTS AND CONCEETES\

for the setting coat. A run arris is more speedily done
and truer than a ruled and trowelled arris. In some
districts woo'den beads are used for external angles. The
floating is cui down at each side of the bead, to allow the
quirks to be formed when the setting coat is laid. When
the setting coat is trowelled, the quirks are formed by
applying a large-headed nail on the bead, and drawing
it up and down to cut the stuff out. They are then fin-
ished by working a laying trowel up and down until
smooth and true, and afterwards wet-brushed. The
bead quirks are sometimes cut out by aid of a wooden
template, also by laying a straight edge on the work as
a guide for cutting the stuff out. They are then finished
with a trowel and brush, as already described.

Skirtings. — Skirtings or base, are sometimes formed
in wood, but are often formed in cement. Cement skirt-
ings are far more sanitary than wood skirtings, as the
former connects the wall and the floor in one solid fire-
resisting and vermin-proof body, whereas wood skirtings,
owing to their nature and construction, afford a ready
harbor for vermin, and offer but little or no resistance
to damp and fire — indeed, their hollow formation pre-
sents a vent in the case of fire. Parian or other white
cement is generally used where a fine finish is desirable,
and Portland cement where the work is exposed to wet
and hard wear. Skirtings are generally run by first
roughing out the plinth by aid of a gauge rule bearing
on the floating, and then forming a running screed, and
fixing a running rule on the plinth. The skirting mould-
ing is then run in the usual way, after which the running
rules are taken off, and the plinth set." The mould plate
should be cut to form about 1 inch of the top part of the
plinth, to form the arris, and a bearing when setting the
plinth. The annexed illustration (No. 4) shows the

TERMS AND PBOCESSES 123

method of forming the core and plinth, and running
the moulding. Pig. 1 shows the gauge rule (G) in posi-
tion to form the core (C). The gauge rule is from 3
feet to 4 feet in length. The plinth is formed ay first
roughing out with gauged stuff, and then drawing the
gauge rule along the floating to form the core, and a
fair surface for the running screed. Fig. 2 shows a sec-
tion to form the core (C). The gauge rule is from 3
(B) fixed on the plinth or core (C).

tSkirting Format ic

Two-Coat Work. — This is a cheap method of plaster-
ing, and only used for common work, such as the walls
of factories, warehouses, &e. It is performed by laying
one coat of coarse stuff and then forming the surtace
fair with a darby, after which it is scoured onee. It is
then finished hy laying a thin coat of setting stuff over
the surface, and then trowelling once and brushing twice
wet and once semi-wet.

One-and-a-Half-Coat Work. — This is sometimes termed
"coat-and-half work." It is a species of two-coat work
—in factj it is so termed in some districts. It is done by

124 CEMENTS AND CONCRETES

first laying a coat of coarse stuff fair, and then scratch-
ing the surface with a coarse broom, after which a thin
coat of Qxtra fat coarse stuff is laid, straightened .with a
darby, and then trowelled and brushed. The second coat
must be laid while the first is green. This permits the
two coats to amalgamate better, and the surface to be
more easily worked and finished.

^^ta^^etrt^Stucco is an Italian term usually applied in
Italy to a superior species of external plastering. Ac-
cording to Vasari, Primaticcio * * did the first stucchi ever
executed in France, and also the first frescos.'' In the
United States stucco is a somewhat indefinite term, used
loosely for vRrinns plastifi miYtiirPH in wh^'gfi ^nrnp^^^l-
4^1 lime, plaster, or cements enter. Hydraulic lime

was formerly used tor external stucco. Roman cement
was extensively used for stucco fronts during the first
half of the present century. Selenitic lime has some-
times been used for a similar purpose. These materials
are now entirely superseded by Portland cement. The
adoption in England of stucco externally to give brick
houses the appearance of stone is due to Robert Adam.
Its plastic nature enables it to adapt itself to most archi-
tectural purposes with very considerable decorative ef-
fects. The more general use of stone and the improve-
ments in terra cotta have so greatly decreased the use of
stucco for fronts, that stucco has become a synonym for
a sham, and its real usefulness for certain works and
places has been greatly overlooked. When properly pre-
pared and manipulated it makes excellent work, and in
the near future a* large use may be predicted for its use.
Old Stucco. — It has already been shown that stucco
was largely employed by the ancients for plain and dec-
orative purposes. The temple of Apollo at Delos, and
even the first Parthenon under the -^gis of Pallas her-

TERMS AND PROCESSES 125

self, were plastered T^^ith stucco. Vitruvius in his sev-
enth book mentions stucco under the name of opus al-
barium, sometimes written album opus. Tectorium opus
(from tector, a plasterer) was a name given by the Ro-
mans to a mortar used for plastering. According to
Vitruvius, Palladius, and Pliny, there seems to have been
a difference between tectorium opus and that called al-
barium or album opus. Vitruvius says tectorium was
composed of three coats of lime and sand, and three of
Kme and marble. According to Winckelman, the united
thickness of these coats was not more than one inch.
The first coat was of common, but old, lime and sand,
and when it was nearly dry a second coat of lime was
laid, and on this drying a third coat of fine lime was laid
and made fair. The work was then laid with another
two coats of lime and marble, and finished with a coat
of fine marble powder. The marble mortar was fre-
quently beaten to render it tough and yet pla3tic, and
it was judged fit for use when it would no longer stick
to the trowel. When the lime mortar was dry, the mar-
ble mortar was laid, each successive coat of marble mor-
tar being laid before the preceding one was quite dry.
The first coat of marble mortar wias composed of coarse
ground marble and old lime, the second of fine ground
marble and lime, the finishing coat being neat marble
ground to a fine powder, and laid before the second coat
was dry, and worked with a wood float until the surface
was consolidated and straight. When dry it was pol-
ished with lime and chalk or with marble until like mar-
ble itself. Old stucco has been found so hard and highly
polished that it has been used for looking-glasses and
tables. In time it became hard and not liable to crack,
and formed an excellent ground for the painting with
which the Greeks and Romans decorated the walls of

126 CEMENTS AND CONCRETES

their houses. According to Vitruvius, this painted plas-
ter could be detached without fear of injury, and de-
tached slabs were carried to Italy and inserted in the
walls of Roman houses. To prevent the cracking of the
work done on wood, it was st?:engthened by two layers
of reeds, one layer crossing the other at right angles.
To insure dryness, and allow the plaster to attain its
proper hardness, the walls were perforated at suitable
places. The tectorium was then decorated with brilliant
colors, which were applied on, the last coat while it was
fresh; and to heighten, the brilliancy and endurance of
the colors the surface was rubbed over with wax and
pure oil. When marble was used with lime in place of
sand it was termed martmoratum. The alburium or
album opus was what we term plaster or stucco. The
Greeks named tectorium and alburium, koniama and
kalachrisis.

Slabs oi tectorium from the walls of Pompeii and Her-
culaneum are now in the Museum of Portici, and speci-
mens are also in the South Kensington Museum. In the
Museum of Practical Geology, London, there are several
pieces of old plaster, taken from the ruins of Pompeii,
some of which show that the decorative colors wer6 not
applied a la fresco, but subsequent to the polishing.
Stucco and plaster are really two very different things.
Stucco has for its base carbonate of lime, generally burnt
limestone or chalk, with which putty lime and coarse
stuff is mixed with sand, &c., and used for plastering
walls and ceilings. Plaster has for its base sulphate of
lime, being made from gypsum, and is used for cast
work and gauging with lime putty, &c. The best kinds
of stucco will resist the action of weather, and can fee
washed. Plaster, unless specially prepared or indurated,
perishes by exposure, at least in our climate, and cannot

TERMS AND PROCESSES 127

be washed. Stucco is a superior kind of mortar, and it
may be used for plastering or for modelling. The ad-
mixture of various materials with lime and with plaster
to form stucco is referred to by many ancient writers.
Pliny mentions -fig juice as being mixed with stucco.
The Egyptians mixed mud from the Nile with plaster
for some of their work. Elm bark and hot barley water
was mixed with the stucco for Justinian 's Church of the
Baptist, Constantinople. We find bullocks' blood em-
ployed for this purpose as well in mortar for Rochester
Cathedral in the latter part of the ninth century. Bishop
Gundulph (1077-1108) is stated to have mixed blood
with lime to make it hard.. Hot wax mixed with lime
was used at Rockingham Castle in 1280. White of eggs
and strong wort of salt were mixed with lime used for
Queen Eleanor's Cross at Charing Cross in 1300. Pitch
and wax were mixed with the lime used for Edward
II. 's works at Westminster in 1324. Mediaeval build-
ers habitually used beer, eggs, milk, sugar, gluten, &c.,
for mixing with mortar for cathedrals. Frequent en-
tries found in the archives prove this. One reads, *'For
beer to mix with the mortar." Bess of Hardwicke's ma-
sons used beer in their mortar, having to melt it in the
cold winter of her death. Old plaster is found to have
rye straw mixed with it for binding, and was very strong.
A brown substance somewhat like plaster, but full of
fibre, was in use in the sixteenth century. The accounts
for the repairs of the steeple of Newark Church in 1571
contain an entry, **6 strike of malt to make mortar to
blend with ye lyme and temper the same, and 350 eggs
to mix with it." During the building of the Duke of
Devonshire's house at Chiswick, the exterior of which
was plastered with stucco, the surrounding district was
impoverished for eggs and butter-milk to mix with the

128 CEMENTS AND CONCRETES

stucco. Peter le Neve's mention of rye dough stands
not alone, as Sir Christopher Wren's **Parentalia"
(1750) records the use of ** marble meal" as the eld and
still the modem way of stucco work in Italy. ** Marble
meaP' simply meant marble dust ground as fine as meal.
This dust was used for fine work. Sugar and the gluten
of rice are used in Ceylon and India. The Chinese use
a rich unctuous earth in combination with lime. In some
parts of France urine was used with plaster in the six-
teenth century. Nearly all these admixtures are to re-
tard the setting, to allow more time for the manipulation
of the stuccos. Some are to accelerate the setting, and
some are to increase their ultimate hardness.

Many of the ancient buildings in various parts of the
universe, which were built of mud, clay, or sun-dried
bricks, had their surfaces decorated with hand-wrought
stucco. During explorations in Peru, South America,
Dr. Le Plongeon found some interesting specimens of
ancient plaster work in a number of the ruins of the
early Peruvian houses and cities, which date back to re-
mote antiquity. At Chenni Concha he found the frag-
ments of some ancient ornamental stucco on the adobe
(or clay-built) walls, /30vered with bas-relief decorative
designs, while the material is after many centuries still
in good preservation. The design and the execution are
of considerable merit, and it seems wonderful that a
people ordinarily held to be but little better than savages
could have conceived ornamentations so aesthetic, and
have executed them with such high technical ability.

Cav. M. Geggenheim, who has had much stucco work
done in the Palazzo Papadopcli and elsewhere, gives the
following formula for the stucco duro which is still used
in Venice : It is old stone lime, slaked for three years
at least, mixed with Carrara marble dust, ground as fine

TEEMS AND PEOCESSES 129

as flour, into the consistency of paste. This of course
13 for the finishing coat, the rough modelling being ex-
ecuted with a coarser material.

There are four kinds of so-called stuccos which are
used in this country. They are known as common, rough,
bastard, and trowelled. The methods of working these
species of plastering are embodied in the description of
three-coat work — in fact the only difference between
these stuccos and three-coat work lies in the setting coat,
the first-coating and floating being the same for all.
Some of the aibove terms are now only used by work-
men, and the use of stuccos is to a great extent super-
seded by Portland cement for exterior work, and Parian
and other white cements for interior work. The follow-
ing is a summary of the materials and methods used for
the various stuccos.

Common Stucco. — Common stucco was principally
used for exterior work. It is composed of 3 parts of
coarse sharp sand to 1 of hydraulic or grey lime, to which
a small portion of hair is added. It is laid in a similar
way to ordinary renderiag in one coat, and the surface
fini^ed with a hand float.

Bough Stucco,- — This is generally used for plastering
churches, corridors, and entrance halls to imitate stone.
The work is floated with ordinary coarse stuff, and then
set with stuff composed of 3 parts of washed sharp sand
and 2 of grey lime putty, not chalk. This is laid with
a trowel, and then ruled in with a straight edge until
the. surface is full and fair. After this it is scoured
with an ordinary hand float, and flnished with a **felt
float," not to raise the grit, but to keep it down. The
felt float is an ordinary hand float with an unplaned
sole, on which a felt scle, about ^ inch thick, is fixed
with gauged plaster. This tool before using generally

130 CEMENTS AND CONCRETES

requires to be rubbed on a straight stone to obtain a uni-
form face. Great care must be exercised when laying
and finishing the surf ace, so that no joints are shown,
or else they will never dry out. When wanted to repre-
sent ashlar masonry, the surface is set out with lines to
the size of the required stones, and then the lines are
indented to form the joints with a jointer or the ring
end of a key. The grain of the stone can be better imi-
tated by patting the surface with the hand float as a
finish. The staining of stucco to represent the color of
stone is done by diluting sulphuric acid (oil of vitriol)
with water, and mixing with it the liquid ochres and.
other colors to the required tints. The setting stuff may
also be mixed with the ochres before using. A small por-
tion of the colored stuff should be dried to ascertain the
tints before laying the whole surface.

Bastard Stucco is somewhat better in quality than or-
dinary setting. The final coat is composed of 2^^ parts
of washed sharp sand and 2 parts of chalk lime putty.
It is laid in tw:o coats with a skimming float, scoured up
once and then trowelled off and brushed.

Trowelled Stucco is generally used for work that has
to be subsequently painted. The stuff for the finishing
coat is composed of from 2i/^ to- 3 parts of washed sharp
sand to 2 parts of chalk lime putty. The sand is not so
fine as that used for ordinary setting, being washed
through a sieve having about 12 mesh to the inch. The
stuff is laid on, and then traversed with a floating rule
in all directions, up and down, across and diagonally.
The surface is then scoured up without water, and after
a rest to admit of shrinkage, the surface is scoured up
threfe times with water ; the trowel to immediately follow
the third scouring up. This trowelling is continued
until the work becomes so hard that no impression can

TEEMS AND PROCESSES 131

be made on the surface; it is then brushed off with a^
soft damp brush (not wet), first horizontally, then diag-
onally, and finally perpendicularly, leaving a brilliant
face. When dry, the gloss goes off, and leaves a fine
.surface for paint.

Colored Stucco, — The Italians execute lime stuccos in
colors, mixing in the lime various oxides — i. e., blacks
are obtained by using forge ashes containing particles of
iron; pearl greys are made by mixing ashes with the
marble ; greens are obtained by using green enamel, with
a large proportion of marble powder, worked up with
lime-water; browns by mixing ashes with the lime and
marble in proportions varying with the tints desired;
reds by using litharge, or the red oxide of lead; blues
by mixing 2 parts of marble powder and 1 of lime, and
% of oxide, or carbonate of copper. Stucco may also
be colored witbl the same materials as described for
colored setting, also for sgraffito and concrete.

Method of Working Keen's, Parian, and Martin's
Cements, — ^When describing the technique or practical
manipulation of Parian and the other white cements
which have been invented in the nineteenth century, it
is only natural that one should feel animated by a pecu-
liar pleasure, because in these cements, our industry,
aided by modem science, has, as far as is known,
equalled, if not excelled, anything of the kind produced
by the ancients, tested by any experiment, whether for
strength, solidity, or durability. With these a great sav-
ing in time can be effected, as work can be begun and
finished in one operation, without waiting for the differ-
ent coats to dry, as in ordinary lime plastering. For
sanitary purposes they are unequalled. This, combined
with their chemical properties, which enables them to be
painted, papered, or distempered as soon as finished,

132 CEMENTS AND CONCRETE;^

renders them the most valuable of all plastering materials
in this go-ahead age. They are free-working, sanitary,
durable, and practically fireproof. They are the very
best materials for plastering walls, dadoes^ or in similar
exposed positions. For skirtings they are invaluable,
as they offer an effectual resistance to fire, vermin, and
dust. When properly manipulated, they can be worked
to a porcelain-like surface. They are nearly perfection,
and constitute perfect plasters for most interior work.
Their only drawback is that they will not resist the ef-
fects of moisture. It is therefore imperative that damp
walls should be floated with Portland cement, where
a white cement finish is desirable. By the aid of the
hard and sanitary white cements plastering has become
a tangible reality, instead of a comparative makeshift,
which it has hitherto been. The object aimed at in the
invention of white cements for internal use is to pro-
duce a material of which plaster is the base, which shall
set sufficiently slow to be easily manipulated, become
dense, hard, non-porous, and may be painted as soon as
finished. Before the introduction of these cements, all
making good, as it is technically called (i. e., patching
holes in old plaster work), used to be done with neat
plaster, plaster and sand, or lime gauged with plaster.
Keen's was first introduced, then Parian, and lastly
Martin 's. Parian being most in demand, claims priority
in description. Parian and other white cements are uni-
formly reliable in quality, but through the rapacity of
some contractors the cements are often adulterated with
plaster to lower the cost, and hasten their setting. This
adulteration causes the cement to swell, and in many in-
stances to peel or fall off. Even if it does adhere, it
never attains its due hardness, and thus is no better than
ordinary plaster. Unfortunately adulteration brings

"terms and processes 133

discredit on the cement and the trade. The only remedy
is proper supervision by a plasterer who possesses a thor-
ough knowledge of plastic materials and the methods of
using them. If plasterers were awarded certificates of
competency, adulteration would be prevented, and good
work ensured. Honest employers would find this bene^
ficial, for scampers can only thrive where there is a lack
of knowledge of the technique peculiar to plastering,
and which only plasterers of experience really possess.
. In using Parian cement on lath-work, exceptional care
must be observed that all the lath nails be galvanized,
or painted ovef, or ooated with shellac, to prevent rust.
For this same reason all nails used for plumbing and
levelling purposes must be extracted after the screeds
are set. For first-coating and floating ceilings with this
material, the proportions for best work are 1 part of
cement to 2 of clean sharp sand, adding about the same
quantity of hair as for lime plaster. Walls are generally
floated with Portland xjement in the proportion of 1 part
of cement to 3 of sand, and finished with neat Parian.
This system is adopted as a matter of economy, as Port-
land cement is cheaper than Parian; and where time is
no particular object, makes equally as good work. For
walls intended to be painted or polished immediately, it
is necessary to mix the materials in the same proportion
as for ceilings, with the difference that more sand may
be used — ^say 2 parts of cement to 5 of sand. The rea-
son for this is, that when floated with Portland, and
finished with Parian an efflorescence invariably appears
on the finished surface, and until it has time to dry out,
it is inimical to successful painting or polishing. Gaug-
ing is an important point; it must be carefully and
quickly done to insure success and obtain the full
strength of the cement. For first-coating or floating

^ I

134 CEMENTS AND CONCRETES

ceilings, empty a sackful, or half a sack according to
requirements, in a clean banker; then add the sand in
the proportions already given, and thoroughly mix the
cement and sand while yet dry; then form a ring, and
pour in the water, taking care not to pour in too mucl;i,
as it must be gauged, and used as stiff as practicable.
There will be no diflBculty in thus using it, as it will take
some hours to set, according to the season of the year
(quicker in summer than in winter). When the water
is in, add the hair (which must previously be well beaten
and soaked), and gauge the whole mass together. Then
begin the first coating, scratch it in the' usual manner,
and so on, until the whole ceiling i^ first-coated. It
should stand for twenty hours before starting to float.
Hair is generally omitted for common work, or where
the laths are close.

Parian cement ceilings should be dead level, and have
a uniform and straight surface; therefore the screeds
should be levelled, made narrow, and the sides cut square,
and when firm the whole ceiling should be ruled in with
a floating rule, sufficiently long to reach from screed to
screed. The floating stuff is gauged moderately stiff,
and laid diagonally across the line of laths, so as not to
spring the lath- work, or disturb the key of the first-coat-
ing. After the ceiling has been laidj the floating rule is
applied, a man holding each end (and one at the center
if extra long). It is then drawn gently and steadily
along, filling up hollow places, until the whole surface
is straight and true. When the surface is firm, it is
brushed with a coarse broom to form a key for the finish-
ing coat. If there is a Parian cement cornice to be run,
the usual mode for plaster and putty is adopted for the
running rules. The screeds should be made sufficiently
smooth to run on, without forming an extra thickness or

TERMS AND PROCESSES 135

traversiiig screed. The cornice is roughed out with the
samQ kind of material as used for the floating, employ-
ing a muflBed running mould for running the rough stuff.
It may not be practical to rough out all the cornice at
once, as this stuflE does not set quick, therefore it may be
necessary to leave it for a time until the stuff stiffens.
No definite directions can be laid down in this matter, as
the suction is greater in some seasons and rooms than in
others. A little extra hair, also extra stiff gauging, is of
service to make the stuff cling together, thus allowing
the work to be roughed out sooner. The running moulds
must be made of strong zinc or copper (no iron to be
used on any account). Where the work is in cornices,
skirtings, achitraves, &c., the mould should be muf-
fled with a zinc or copper plate. If there is only a small
quantity to be run, a plaster muflSe may suffice. After
the cornice is roughed out, it is finished with neat Parian,
and then the mitres formed in the usual way.

In preparing to finish a large space (ceilings or walls)
it is absolutely necessary that no more should be laid
than can be finished the same day, therefore as many
men should be put on the job as will accomplish that
object, as no sign of a joint should be shown on the sur-
face. In the case of large or high walls, the scaffold
should be so arranged that the men can work the whole
wall from the cornice down to the skirting in one op( ra-
tion. If a wooden skirting has to be subsequently fixed,
one end of the rule bears on the fixing grounds ; but if a
Parian skirting or base is specified, it is generally run
before the walls are finished, and allowed to get thor-
oughly hard, so as to bear the end of the rule used for
the finishing coat. The lower end of the rule is cut to
fit the upper member of the skirting. Another way is
to nail a board onto the end of the rule, so that it bears

136 CEMENTS AND CONCRETES

well on the plain plinth and clears the members of the
skirting. The cornice screed must be keyed with a .drag
before the finishing coat is laid. For large cornices it
is often desirable to traverse the running screeds. In
this case they must be cut down to the floating, leaving
only the margin formed by the running mould. This
margin forms a bearing for the top end of the rule. In
some instances a special margin or bearing is cut at the
outer members of running moulds for cornices and skirt-
ings, and when run they form a bearing for the floating
rules.

When ready for the finishing coat, empty as much as
required of neat Parian cement into a clean banker, and
gauge it smooth and stiff; then soften it down to the
desired consistency, always bearing in mind not to make
it too soft, as sloppy stuff for any purpose is ever to
be avoided. The gauging should be so arranged that
when one batch is in use another one is ready, which
prevents delay in laying the whole space, thereby ensur-
ing similarity of texture and results. The thickness of
the finishing coat should not exceed % inch. When
there are about a dozen yards laid, two men must follow
dn and rule the surface fair from screed to screed on
ceilings, and top and bottom on walls. The greatest pos-
sible care must be observed that the whole surface is
ruled in fair and uniform, otherwise the surface will be
imperfect.

White cements, owing to the suction of the walls or
ceilings, have a tendency to shrink more or less, accord-
ing to the stiffness of the gauge and the section, there-
fore they must be ruled in twice. When the coat already
laid is firm, then some more cement, gauged softer than
the first, should be laid thinly all over, and ruled as care-
fully as before. Having done this the whole surface is

TERMS AND PEOCESSES 137

nearly ready for scouring. It is allowed to stand for an
hour or two, or until quite firm. If scouring is at-
tempted before, it will work into hollows, and a bad job
will be the result If the finger cannot make an im-
pression upon it easily, it is sufficiently firm, and then
all hands begin to scour the work, using very little water,
and working the hand float with a circular motion. The
hand float must not be worked long on one spot, but kept
moving over all the surface within reach, and working
back again until the whole surface has an even grain or
texture. The whole work must be scoured twice to bring
it up to a fine solid surface. When there is about half
of the wall scoured, two or more plasterers can continue
the scouring, and the remainder of the men go back and
start the trowelling. This must be done with good long
strokes, using very little water, and taking care not to
dent the surface with the trowel. After the men have
finished the scouring, they come back and start at the
beginning with the second ''trowelling pflf or final
trow^elling. This is done both vertically and horizour
tally, and when the work begins to harden, the trowel i^
laid on the near edge and worked with a cutting motioi;i
downwards. This is repeated all over the work until
every particle of glut or **fat*' is cleared off the surface.
If the work has to be polished, the cutting action with
the trowel must be followed with a 9-inch joint rule an<J
a damp brush, but the work must be hard before this
last can be attempted. Work carried out on the above
plan will reflect credit on the material and the workers.
The same methods apply equally to Keen's and Martin's.
Martin's is preferred by some plasterers for running
cornices because it sets quicker than Keen's. For plain
surfaces, such as walls and ceilings, it sets too quick,
and has to be ** killed" (that is working the stuff again

138 CEMENTS AND CONCRETES

and again with water until the initial set is stopped or
**dead") before it can be conveniently used. Although
it finally sets fairly hard, it never attains the same de-
gree of hardness as Keen's or Parian.

Several other white cements and plasters have been
introduced during the last two decades. They will be
noticed later on.

White Cement Efflorescence. — ^For work that has to
be painted, care must be exercised in the selection and
manipulation of the materials used for the plaster work,
so as to avoid as far as possible subsequent eflBorescence.
In the manufacture of Keen's, Parian, and Martin's
cements, Keen's original process is doubtless the best.
It requires, however, great care in carrying out, the
chemicals used and temperature employed requiring to
be suited to the peculiarities of the gypsum. The de-
sired result is extreme hardness, combined with non-ef-
florescence. Keen's cement is practically non-efflores-
cent, as if applied on a dry wall containing no soluble
salt, in itself there would be no efflorescence that would
spoil paint. Perhaps one should not say that Keen's
cement, or at least all brands of it, are absolutely non-
efflorescent, as there is generally a powdery coating comes
on the surface, just enough to whiten a colored hand-
kerchief, something like the coat of puflf powder used
on some female faces. On no account should Keen's
cement be used on walls as a preventive of damp, as
it is useless for this purpose. If used on a damp wall,
or in places exposed to atmospheric influences, it will
effloresce more or less, as its base is gypsum, which al-
ways remains soluble. In damp situations the walls
should be rendered or floated in Portland cement before
the finishing coat of Keen's cement is laid. The same
remarks apply to Parian and Martin's cements. The

TEEMS AND PROCESSES 139

Keen's cement manufactured by Hunkin's and Willis,
St. Louis, Mo., is practically pon-efflorescent.

Cornice Brackets. — ^Brackets or cores are used to de-
crease the amount of materials and weight, and also to
form a foundation and support for cornice or other
mouldings. For large exterior work they are generally
formed with stone, and for small work bricks, tiles, or
slates are used, which are built into the walls as the
work proceeds, and roughly fashioned to an approxima-
tion to the profile of the intended cornice or other mould-
ing. For interior work the brackets are sometimes con-
structed with metal lathing, also with spikes and tar
bands, termed ** spike and rope brackets,'' but the oldest
and most general way for cornice mouldings are **lath
brackets." The '* brackets" on which the laths are sub-
sequently nailed are cut out of boards from % inch to
1^2 inches thick, according to the size and form of the
cornice. The section of the brackets should be about 1
inch less than the profile of the proposed cornice to allow
for a thickness of lath and plaster. The thickness of the
plaster should not exceed 1 inch, or be less than ^ inch.
If too thick it is a waste of materials, and the undue
weight is apt to pull or spring the laths from the brack-
ets, and if too thin the stuff is apt to crack. The profile
of the bracket need not follow closely that of the cor-
nice, but a general or approximate outline of the most
salient members followed. Any thin projecting mem-
bers may be subsequently strengthened by means of
projecting nails and tar-strings similar to a spike and
rope bracket ; also by using extra hair and plaster in the
roughing out stuff. Brackets for enriched cornices re-
quire special notice. Unless a due allowance is made for
sinkings for the thickness of the cast enrichments and
a correct form of bed, there will be unnecessary trouble

140 CEMENTS AND. CONCRETES

in cutting and hacking the lath work and brackets when
the running of the cornice is commenced.' There is a
marked difference between the section of a running
mould for an enriched cornice and that of a plain cor-
nice, even if the profile of both are the same. To avoid
mistakes of this nature the plasterer should supply the
carpenter with a section of the brackets, taken after the
bed of the enrichments are set out on the tracing of the
proposed cornice.

Skeleton brackets is a term applied to a method some-
times used for coring out angles, to save materials where
there are no brackets, and for small mouldings. This is
effected by placing the mould in position and then fitting
a piece of lath in a vertical position, and allowing a space
of about % inch from the face of the lath to the nearest
part or most prominent member of the mould. A mark
is then made on the ceiling and wall at the top and bot-
tom of the lath. Similar marks are made at the other
end of the wall and ceiling, and then a line is struck on
the marks, from end to end of the ceiling and wall, by
means of a chalk line. The stuff which forms the parts
of the screeds inside the lines is cut away, dusted, wetted,
and then a narrow strip of gauged coarse stuff is laid
along the lines where the ceiling and wall screeds are
cut, and the laths which have been previously cut to the
length of the first or trial one are fixed vertically into
the gauged stuff, keeping them apart as in ordinary lath-
ing. They are further secured by laying strips of
gauged stuff on the outward surfaces at the top and bot-
tom ends. After the stuff is set, the cornice is run in
the usual way.

Cornices. — Cornices, either plain or enriched, are
formed with a running mould cut to the profile of the
intended cornice. The formation of cornices consists of

' TERMS AND PROCESSES 141

constructing the mould, making the running screeds,
fixing the running rules, running the cornice and mitring
the angles, with' the addition of fixing the cast omasient
for enriched cornices. Cornices were formerly run in
short lengths and in sections. Two, three, and even four
inoulds were employed for cornices that are now done
with one. For large cornices, where the mould is diflS-
eult or sluggish to run, or apt to jump, the bearings
should be greased or brushed with soap or dusted with
powdered black lead or French chalk. Running moulds
are run in some places with the left hand, from left to
right, and the mould plates are also fixed to the left hand
side, having the bevelled part of the stock to the right
or running side. In America the plates' are fixed oh the
running or right side, and the mould is run with the
right hand from right to left. The way of running from
left to right with the left hand allows more freedom,
especially in small mouldings, for the right or trowel
hand to assist in feeding the cornice with the stuff that
gathers on the mould. It also gives more freedom to
his partner who is laying on the stuff, as with the hawk
in his left hand and his trowel in his right he is able to
work in a natural position, namely, from left to right, as
in laying coarse or setting stuff on walls, whereas, when
the mould is run with the right hand, and from right to
left, the worker has not' so much power or freedom in
assisting to feed the mould with his left hand. His part-
ner, who is^ laying the gauged stuff, is working back-
handed, and if using a laying trowel, can only work from
its heel instead of from the point as is usual; and if
using the large gauging trowel for laying on every
trowelful used must be put on with a backhanded turn.
It may be a matter of opinion as to which method is
better, and depends a good deal upon which way the man

142 CEMENTS AND CONCRETES

has been taught, but the manner of running the mould
and laying on of stuff from left to right, the same as
in writing, is the most natural. Running screeds are
used as bearings for running moulds. They are com-
posed of gauged stuff, and made straight with floating
rules. Screeds for cornices are formed with raw or with
gauged coarse stuff. They are next traversed. The
line of the screed is got by placing the running mould
in its true position or at one end of the wall, and mak-
ing a mark on the floating screeds at the outside of the
nib and the bottom of the slipper. The same operation
is repeated at the other end of the wall, and a continuous
line from one mark to the other made on the ceiling wall
by means of a chalk line. A narrow strip of gauged
putty and plaster is now laid on the lines by one man,
while his partner follows on with a traversing rule, work-
ing the rule with a slanting motion, and moving back-
wards and forwards until the screed is just and true.
Where the walls are very long, running screeds are done
by two men working a long straight edge or floating
rule. The screed is afterwards further fined by draw-
ing a cross-grained hand float three or four times over
it in a longitudinal direction. Where the coarse stuff
screeds are not gauged, the running screeds are made in
a similar manner, but the putty is mixed with an equal
proportion of setting stuff before gauging. The addi-
tion of sand gives more resisting power to the wear of
the nib and slipper of the running mould. The run-
ning screeds are made on the long sides of the room,
and when set they give a bearing for the end screed in
its true position at one end of the wall.

Fixing the running rules is the next operation. This
is done by placing the running mould in its true position
at one end of the wall, taking care that the mould is

TERMS AND PROCESSES 143

square," that is, that the perpendicular parts of mem-
bers are plumb with the wall. This may be tested with
a plumb bob hanging over the side of the mould, and by-
seeing that the line of the plumb bob hangs properly over
a marked line, which has been previously made by squar-
ing off from a square member or by extending a parallel
line from an upright member of the mould. When the
mould is plumb and square, a mark is made on the ceil-
ing screed at the outside part of the nib, and another
made on the wall screed at the bottom of the slipper.
The same operation is repeated at the other end of the
wall, and the line extended from mark to mark by using
a chalk line. The line in this case should be blackened
by means of charcoal or burnt stick, as it shows better
than a white line on the light-colored screeds. As the
chalk line may sway when striking. the wall line, this
line should not be trusted for fisSng the running rules
to. This may be proved by placing the mould every 3
or 4 feet apart in the length of the wall, taking care to
keep the outer edge of the nib at the ceiling line; then
marking with a gauging trowel at the bottom of the slip-
per. Nails are now driven into each of these marks and
left projecting as a guide for fixing the running rules.
The running rules should not be less than 2^^ inches
wide or more than 3^ inches wide and ^ inch thick,
being made out of good redwood or pine planed on both
sides and edges. The rules are now fixed into the wall
screed either by nailing them to the studs or into the
joints of the walls. They are also fixed by wetting one
face of the rule and laying dabs of gauged putty and
plaster about two feet 6 inches apart. The rules are
now pressed' on the wall while the stuff is soft, taking
care not to force the guide nails out of position. The
mles are further secured by laying patches of gauged

144 CEMENTS AND CONCRETES

stuff underneatji the rule partly on the wall and rule
where the dabs are. When the rules are fixed by nail-
ing, it is apt to crack the first-coat of floating, and the
joints of the wall are not always easily found. The
coarse stuff for the first-coat of cornice brackets should
be extra haired and carefully scratched to feive a strong
foundation for the following coats of gauged stuff, which
in many instances is extra thick ^at bold or projecting
parts of the mouldings.

For large moulding and wire lathing it is best to leave
the brackets uncoated when first coating the general
work until the cornice running is commenced, and then
to rough out the whole cornice from the lath work with
gauged coarse stuff. This gives uniform suction and
strength. If the brackets are lathed with wood, they
should be first-coated with ga^ged coarse stuff and
scratched before the- screeds are formed, so as to allow
time for the lath work to settle before the mouldings
are roughed out. Weak laths frequently twist by moist-
ure from the first-coating, and gi*adually settle or re-
sume their original form during the drying of the first-
coating. Leaving the lathed brackets uncoated also
forms a vent for the moisture from the wall and ceilin<?
first-coating, thus allowing it to dry sooner. ' The coarse
stuff for roughing out the cornice should be gauged uni-
formly in strength and consistency, as unequal gauging
tends to cause unequal swelling in the material, conse-
quently the mould is more difficult to run true. The
coarse stuff should be laid regular in thickness, taking
care to gradually build up and form all thick parts and
projecting members with the trowel to prevent the stuff
from dropping and the mould from dragging it off, as
generally happens if the stuff is laid in thick and irregu-
lar coats. When roughing out large mouldings with

TERMS AND PROCESSES *145

coarse stuff, the members of the mitres should also be
filled in and ruled fair before the running with gauged
putty is commenced, because when mitring, it will be
more easily and quickly done, materials will be saved,
and when finished, the whole will be more uniform in
color.

When all the mouldings are roughed out, the plaster
muffle or muffle plate, as the case may be, is taken off,
and the running with fine gauged putty commenced.
The gauge board and all tools should now be cleaned to
free them from grit. A ring of putty is formed on the
gauge board, leaving the bottom of the board cjear;
water is put in the ring and the plaster quickly and
evenly sprinkled over the water, taking care not to sprin-
kle it on the putty ring. The plaster and water are
mixed together by stirring with the point of a trowel.
The putty is then quickly mixed with the gauged plaster
by using the trowel and turning it over with the hawk.
It is put on with a large gauging trowel, or if the mem-
bers are large, with the laying trowel, following the form
of the mouldings. The mould is then run along by one
man, who also feeds the moulding with any stuff that
may gather on the side of the running mould. This
operation is continued until all the members of the
mouldings are filled out. A thin gauge of fine putty,
having less plaster than the previous gauges, is lightly
drawn over with a trowel, or. brushed over the flat mem-
bers, and thrown with a brush for small or dry mem-
berg. This mould is then quickly and steadily run along
the cornice from beginning to end and finished. If the
moulding, is extra large in girth, or a long length of
moulding has to be run, extra men are required to lay
the stuff, while two may be necessary to run the mould.

146 CEMENTS AND CONCRETES

When running small mouldings, say of 10 or 12 inches
in girth, one man can run and feed the mould while his
partner is laying on. When all the mouldings are run
around, the running rules are taken down, the screeds
cleaned and scraped, and any holes or defects caused
by nails or patches used for the rules made good by fill-
ing up with gauged putty. If soap, black lead, or any
other materials already mentioned are used to aid and
ease the running of ,the mould, they should be scraped
off with a drag as soon as the cornice is run off, other-
wise they will prevent the finishing coats for wall and
ceiling from adhering to those parts.

To Set Out and Construct Corinthian Entablature. —
To enable the plasterer to set out a full size or working
drawing from the architect's design, also to comprehend
the cornice and the architrave, which are sometimes used
alone or as separate mouldings, their proportions with
that of the entire entablature are given. The entabla-
ture and the details of the enrichments of the coffers
and modillions are shown on plate.

The whole Iveight of the entablature is divided into
ten parts, giving three to the architrave, and three to
the frieze, and four to the cornice, as shown by the first
upright scale at Fig. 1. This figure shows the combined
section and elevation of the entablature. The height
of the architrave is subdivided into five parts to form
its members, as shown by the second upright scale.
Projection is taken from the lower fascia, and is equal
to one-fourth part of its height. As the cornice of the
Corinthian order is frequently used alone as a separate
moulding, an enlarged view with figured details is given,
see illustration Fig. 4. It is necessary that the details
of the cornice should be mastered before proceeding with
the entablature. See Plate 1.

TERMS AND PROCESSES 147

•

With regards to the enrichments of the entablature,
as shown in Fig. 1, the whole must be set out and so dis-
posed and arranged that the centre of each will be in line
with 4Bach other, or, in other words, that they are regu-
larly disposed perpendicularly above each other, as
shown from A to B (Fig. 1) where it will be seen that
the centres of the modillion, dentil, egg, and other bed-
mould enrichments are all in one perpendicular line.
Enrichments set out in this way are said, in plasterers'
parlance, to *' principle.'' Nothing is more careless, con-
fused, and unseemly than to distribute them without
any order or principle, as they are in many buildings.
The centre of an egg answers in some places of the cor-
nice to- the edge of a dentil, in some to the centre, and
in others to the space between, all the rest of the enrich-
ments being distributed in the same slovenly artless
manner. The larger parts must regulate the smaller.
All the enrichments in entablatures are governed by the
modillions, or mutales, and distribution of these must
depend on the interval of the columns, and to be so dis-
posed that one of them may come directly over the centre
of the column, as shown in the present example at C
(Fig. 2), the axis of each column.

The enrichments must partake of the character of the
order they enrich. When the frieze is enriched, and the
enrichment may be characteristic of the order, or it may
serve to indicate the use of the building, the rank, quali-
ties, profession, and achievements of the owner. Hav-
,ing set out the profile and the enrichments, making the
running mould and the running mouldings now claims
attention. Foi* large work the cornice and the archi-
tr'ave are run separately, the cornice being run from the
slipper screed made on the frieze and a nib screed, and
the architrave from a slipper screed made on the wall

148 CEMENTS. AND CONCRETES

and a nib screed made on the frieze. Sections of the
cornice and architrave running moulds are shown at
Fig. 4. .

It may be here remarked that the nib and slipper
bearings of the cornice and architrave running moulds '
are made for work on ceilings and walls; but if the.
entablature projects or is independent, and supported by
columns, the nib of the cornice mould must be cut so
as to bear and run on a nib running rule fixed on the
weathering of the cornice, and the slipper of the archi-
trave running mould cut so as to bear and run on a
running rule fixed on the soffit of the architrave. The
frieze, if plain, is set by hand; and if enriched, a bed
for the enrichment must be made by running a small
part of the bed at the top and bottom of the frieze when
running the cornice and architrave mouldings. In this
case the screed on the frieze must be set back to allow
for the plate or ground of the omainent, and the nibs ,
and slippers of the running moulds extended at these
parts. In setting out the mould plates an allowance
must be made for the bed of the various enrichments, as
previously described.

k The profiles of the three largest enrichments are indi-
cated by the dotted lines. The angles of the beds of
these enrichments are splayed, as shown, to save fine
plaster used for the cast work. This also strengthens
the top member of the architrave while it is being run.
It will be seen that an in-dentil is used in this cornice,
Bs sho^vn by the dotted line at 1 on the elevation. This .
is the space between the face or main dentils. The in-
dentil is run witb the mouldings, and the dentils ar6 cast
and planted. The in-dentil and the dentil may also be
cast together in short lengths, and then planted. In
this case the running mould must be cut to form a bed

TERMS AND PROCESSES 149

for the combined dentils, as indicated by the dotted line
on the outside of the section of the running mould. The
dotted line on the section of the running mould shows
the section of- the main dentil. In some examples the ,
external angles of the bed of the dentils are filled in with
an ornament fashioned like a cone or pineapple, instead
of using an angle dentil. An enlarged view of this classi
of ornament fixed in position is shown at Fig. 11. The
bed of the small enrichments is made square as shown.

When setting out the mould plate, the profile of the
soflSt of the corona must be taken through the centre of
the sunk panel, as shov/n by the shaded part at Fig. 3,
thus forming the raised part of the mould as shown at
Fig. 4.

The most intricate part in the construction of a Cor-
inthian cornice consists in the formation of the coffers,
as shown at Fig. 2. This is a plan of the cornice at an
external angle. F is a coffer, and M is a modillion or
•'block," as it is commonly called. The coffer consists
of a sunk panel, with an enrichment on the four sides,
and a rose or patera in the centre as shown. A section
of the coffer is shown at Fig. 3. The coffers are formed
by fixing a '* style, '* as from S to S (including the side
enrichments), on the sunk panel, so as to connect the
two run plain sides of the soffit and form two sides of
the coffer. The lines in the front and back of S and
S indicate the joints of the style before they are stopped.
It will be understood that the style is fixed before the
block is fixed. .A plan of the complete style is shown at
Fig. 5. When making the model of the style, the side
enrichments must be set out mitred and fixed on the
plain part of the style, and a perforation made in the
centre to act as a key for the fixing stuff used when
fixing the block. A mark must also be made in the cen-

150 CEMENTS AND CONCRETES

tre of the front of the style to act as a guide when fixing
the styles. The model of the style is moulded in wax,
taking care to splay the back and front edges and the
centre perforation, also the mitres of the enrichments,
to allow the mould to draw in one piece. These parts
are trimmed square after the styles are cast. Having
fixed two styles, the front and back parts of the coflfer
enrichments, as shown at Figs. 6 and 7, are fixed; then
the patera (Fig. 8) is fixed; and then the joints of the
styles are stopped, which completes the coffer. This
done, the block (Fig. 9) is fixed, and then the small en-
richment (Fig. 10) is fixed, thus completing a part of
the soffit of the corona. The other parts are of course
made and fixed in a similar way, but the positions of
the coffers and blocks must be set out on the whole
length of the cornice before the fixing is commenced.

Setting out coffers and blocks is a simple matter, yet
it requires care to ensure accuracy. First fix a coffer
and a block in each mitre, as shown at the external
mitre (Fig. 2) ; then from the centres of these blocks set
out the whole length of the cornice. This is best done by
measuring the full length of the cornice from the mitre
blocks, and dividing the total by the combined width of
one modillion and a coffer, and if there is no remainder,
the combined width is marked on the soffit ; but if there
are a few inches over, they are divided among the given
number of blocks. The marks are proved by going over
them with a compass or a wood gauge. When the exact
positions of the centres of each coffer with the block is
ascertained, the marks are extended across the corona
and down the plain member on which the back end of
the block rests on by the aid of a square. These ex-
tended marks or lines give the centres for fixing the
styles of the coffei's and the blocks. Fixing the coffers

TEEMS ANt) PROCESSES 151

and the blocks is the next part of the process. This
being done, as already described, taking care to use the
cent] -e mark on the coffer as a guide for fixing it fair with
the centre lines on the soffit, and using a wood square to
prov-? the square of the style, also using the edge of the
square to prove the level of the coffer with the run sides
of t]ie, soffit, then clean off any excess stuff that may
exude at the keyhole and edges of the style. After this
the back and front side enrichments are fixed, as already
mentioned. Before fixing the paterae a keyed or under-
cut hole must be cut in the sunk panels to give a key for
the stuff that is used for fixing the paterae. A corre-
sponding keyed hole must also be formed on the back
of the paterae. This is best done by making the desired*
size of sinking in the model of the paterae before it is
moulded. These sinkings must be undercut after the pa-
terae are cast.

The model of the paterae is generally moulded with a
front and back waxed mould. For large paterae, or those
having a deep projection a piece of twisted galvanized
or copper wire, sufficiently long to enter the keyed holes
in the paterae and the soffit, should be inserted in the
fixing stuff when fixing the paterae. This method should
always be adopted where the bedding surface of the pa-
terae is small, so as to enable it to resist the weight of a
brush while being painted or gilded. If the paterae are
extra deep, and project below the line of the soffit, they
should be fixed first, otherwise they are liable to get dis-
turbed when fixing the blocks and other enrichments.

The modillions should be fixed with stiff gauged stuff
for the keyed holes in the styles, and the corresponding
holes in the blocks (which are made while being cast),
and using softer gauged stuff for the bedding surface of
the block. After the fixing stuff is laid, place the block

152 CEMENTS AND CONCRETES

in position, and work it gently but quickly from right to
left, so as to force the excess stuff out, and obtain a true
and solid bed, taking care that the centre of the block is
linable with the centre mark on the soffit, and using a
square to prove the squareness of the block, and then
clean off the excess stuff. The small enrichments (Figs.
6, 7, and 10) are fixed with soft gauged stuff, .so that
they can be easily and quickly fixed. Small cast work
of this kind should always be fixed with soft gauged
stuff, as there is very little weight to carry until the stuff is
set. The suction alone between the two bodies is often suf-
ficient to support the cast until the stuff is set. These small
enrichments are moulded with a face ,or front wax mould.
Modillions or blocks were
formerly cast in three parts,
namely, the body, the main part
of the leaf, and the tip or curled
end of the leaf; the body being
cast IQ a wax piece mould (some-
times a plaster piece mould), and
the leaf and its tip in a front and
back wax mould, but now the
complete block is generally cast
Moamion, "^ '^^^ piece in a gelatine mould,

NO. 6. The body of the block may be

cast in a gelatine mould, but
where the back section of the leaf is clear or away from
^e block near the scroll end, as shown in the accom-
panying illustration, and seen in fine old buildings, the
leaf should be cast and fixed separately. An enlarged
view of the plan and side elevation of a modillion is
shown in illustration No. 5. The bed moulds and the
other small enrichments in the entablature are generally
cast in wax moulds.

TERMS AND PROCESSES

153

When fixing the enrichments in an entablature, take
special care that they all "principle" with each other
as already mentioned, thus forming a pleasing and artis-
tic finish, which is characteristic of well-designed mould-
ings.

-TRnp

, ,'

1 ,. ., ,, i-.3

=v —

•< 1,—^ "|- !. 1 ^

«i S"!' W

To Set Out a Corinthimt Cornice. — The members
- which are enriched in the cornice, shown in the preced-
ing plate, are drawn as plain members on this cornice so
' as to show the profile and method of setting out more
of^r.

154 CEMENTS AND CONCRETES

The combined elevation and profile of the cornice
shown at Fig. 1, in the accompanying illustration, No. 6,
is an enlarged view of the cornice of the Corinthian en-
tablature. The first upright scale contains four parts of
the ten into which the whole entablature is divided, as
on the preceding plate. The second scale is divided into
five parts, the ttird of which goes to the modillion, the
fourth to the corona, and fifth to the cymatium; the first
and second together are divided into three parts, the first
for the reversed cyma at the bottom, the second fot the
dentils, and the third for the ovolo. The smaller mem-
bers are in proportion to the greater, as shown by the
smaller divisions on the scale. The modillions are 1-6
of the diameter of the column, and their distances two-
sixths and a half. Half a diameter is divided on the
corona at Fig. 2 into six parts, of which the width of the
modillion is two, and the length of it is four. The cap
projects 1-3 of those parts, and the distance between the
modillions is five. By this rule the exact distance from
centre to centre of the modillions is 7-12 of the diameter.
The dotted line A C answers to the diminished part of
the column, from whence the cornice is projected; the
projection being equal to its height, is divided into four
parts, as shown by the scale at the bottom of the cor-
nice. One-fourth of this scale is divided into six parts,
as shown at C, five of which gives the width of the modil-
lion. The distance between them is in proportion to it
as figured at Fig. 2. The fillets, F F, of the modillion
are Yg of its width, and so is the bead, B. The position
and size of the sunk panel are indicated by the dotted
lines in the corona at Figs. 1 and 2, the size being ob-
tained as shown by the figures in the dotted spaces. The
width of the dentils, D, is obtained by dividing the semi-
diameter of the column marked on the corona at Fig. 2

TERMS AND PROCESSES 155

into fourteen parts, two of which gives the width of the
dentil, and one the space between them. This space of
course is also the width of the in-dentil, the height of
"which is one-fourth of the height of the main dentil, as
indicated by the small division on the inner side of the
second upright scale.

The centres and radius for describing the profiles of
the cymatium or cymarecta, the ovolo, and the inverted
cyma or ogee members are indicated by small crosses and
dotted lines.

Mitring. — ^Mitring is looked upon by the generality of
plasterers as a test of speed and ability. As they gener-
ally work in pairs on other portions of the work, their in-
dividual ability is not easily seen, but when mitring a
man carries the operation through alon,e.^ Mitring being
done by hand, is a near approach to modelling, and is an
operation of which a dexterous and good plasterer is nat-
urally proud. The quality and time required for mitres
greatly depend upon the degree of hardness of the run
cornice, also upon the suction. A mitre can be more
freely worked and more expeditiously done on a hard
cornice surface, and where there is a suction. The extra
absorbing powers of brick walls as compared to lath par-
titions cause the gauged stuff to get firm sooner, and
enables the mouldings to be more readily blocked out be-
fore the stuff is set. A common error when mitring is
gauging the stuff stronger than that which has been used
for the running of the cornice, causing extra swelling
and difficulty of ruling the members over, and cutting
the run part of the cornice with the joint rule, especially
if the stuff sets before the plasterer has had time to rule
all the members over, and then being stronger, and con-
sequently setting quicker, he has not so much time for
forming the members. Ordinary sized mitres can be

156 CEMENTS AND CONCRETES

done with one gauge by using less plaster than in the
gauge for running the cornice, and stiffening the greater
portion with dry plaster, and using this for roughing out
the mitre; then using the soft portion left for brushing
over the members and filling up all holes, and afterwards
working the joint rule over the metal to take the su-
perfluous stuff off. Should the mitre not be fine enough,
the gauged stuff can be further softened on the hawk by
adding water, and working it with the gauging trowel,
brushing the soft or creamy stuff all over the mitre
again, then working the joint rule again. Small mem-
bers, and those at the top and bottom of the cornice,
where there is most absorption, should be worked by the
joint rule first, leaving the large members, drips or coves,
or where there is a large body of stuff, to be ruled over
last. The joint rule should always be worked horizon-
tally, especially when dealing with beads and carvettos.
Drips and large members should be worked with the
joint rule with an upright motion, because if worked
down, the stuff may be pulled down. Mitres should not
be worked, fined, or tooled with small tools, as they can
and should be brought to a good and straight surface
by the proper use of the joint rule. Small tools should
only be used for laying the stuff when required, and
cleaning out the i itersections of the mitres, quirks, and
for stopping. A square-ended small tool may be used
for smoothing flat, straight surfaces. Returned mitres
and short breaks are '*run down,'* then cut to the re-
quired lengths and planted. They may also be mitred
by hand.

Mitre-Mould. — ^Various attempts have been made to
construct a running mould that would form the mitres
simultaneously with the cornice running. Most plasterers
will have heard of, and some may have tried to make

TERMS AND PROCESSES 157

and work b mitre-mould to save hand labor. Those who
have tried it will have found the results far from satis-
factory.. The subjoined illustration, No. 7, shows the
method of setting out and constructing a mould intende<^

-Mitre- Mould.

for forming the moulding and mitres in one operatioa
The mould is made by fixing the metal plate at an angit
of 45 degrees on the slipper, or in other words fixing the
iron plate at one angle of a square slipper, which allows
the mould to run nearly up to the angle, one face of the
slipper being used for one side of the wall, and the other

158 CEMENTS AND CONCRETES

face at right angles being used for the other side of the
wall. Fig. 1 shows the method of setting out the profile
of mould. A is a given section of a moulding, and B
is the section of the moulding at the mitre. To obtain
this, first draw the moulding A full size, and then extend
the ceiling line and draw another wall line. Then from
the projection of the top member draw an angle line at
45 degrees. Carry up the projections of the various
members to the angle (or mitre line) and then draw hori-
zontal lines from the various members; also centre lines
of large members as from a to 1 (the vertical letters).
Take off the lines a to 1 (diagonal letters) on the angle
line, and set them on the ruling line from a to 1 (hori-
zontal letters), and then laying them down to the hori-
zontal lines, the intersections give the profile for the
mitre-mould. Fig. 2 shows a side elevation of the mitre-
mould, and Fig. 3 shows a front elevation. It will be
seen that the mitre-mould is an expensive and unsatis-
factory fad. . The time expended in setting out the elon-
gated members, making an extra mould, and cleaning
out the intersection by hand (as the mould does not leave
a finished mitre), also making good the parts broken by
drawing out the mould from interlocked or undercut
members in the moulding, is not repaid. An average
plasterer would put in all the mitres of an ordinary
sized room while the mould was being made. The mould
will only run into every second angle, and must be taken
off and reversed to fit the next. It may seem a waste of
time and space to describe and then show the utter use-
lessness of a mitre-mould, but having met many plas-
terers who stated that they had used or had seen a mitre-
mould that worked wonders, I am constrained to give a
description, not only to save future futile controversy,
but to show that in this book the much-debated trade

TERMS AND PROCESSES 159

subject has not been omitted. In concluding this sub-
ject, it may be stated that not any one of the mitre-mould
plasterers would or could practically explain the modus
operandi of this mysterious mould.

Fixing Enrichments. — Enrichments should be fixed
straight, square, plumb, and firm. Cornice enrichments,
such as bed moulds, friezes, &c., for which a bed or sink-
ing to receive them is formed by the running mould, do
not require such strong gauges stuff as soffits, medallions,
or other hanging casts. For light enrichments the gauged
putty and plaster should never be stronger than that
used for the cornice, and clean strong size water should
be used. This gives more time for fixing a number of
easts, and improves the cementing force. The bed for
the cast work should be scratched, dusted, and wetted
before the cast work is applied. A small portion of fine
plaster (the same as used for casting the enrichments)
should be gauged with clean size water, to be used for
the joints. The gauged fixing stuff should be spread
evenly over the back of the cast and over the scratched
bed of the moulding. No more should be laid on than
will fully fill up the scratches. Then place a small piece
of the white or joint gauge on the point, and press the
cast into position by gently but quickly sliding the cast
twice or thrice backwards and forwards to expel the air
and incorporate the two bodies. It is a mistake to dab
a lump of gauged stuff at random on the back of the cast
and press it on the bed, as the stuff does not properly
enter the scratched part of the bed, and the contained
air prevents proper cohesion and solidity. When too
thick a coat of stuff is laid on the coat, straight and even
fixing is more difficult. The excess stuff oozes out at the
sides, and unless time and care be taken in cleaning it
off, the moulding, or cast, or both, get damaged. A

160 CEMENTS AND CONCKETES

small portion may also ooze out in the first mft^od, but
it will be so thin that it can be brushed off while soft.
When fixing medallion blocks or trusses, a dovetailed
hole should be cut in the vertical and horizontal parts of
the bed, and similar holes in the blocks (which are made
when being cast) are filled in with gauged stuff and
applied in position. If the cast should be very heavy,
or of Portland cement, it is further secured by inserting
a slate or iron dowel while the stuff is soft, allowing a
portion of the dowel to project to enter into the body of
the cast. Heavy casts should be temporarily supported
by wood props until the fixing stuff is set. When fix-
ing heavy casts the plain surface of the plaster work
should be cut as far as the lath to obtain a better and
stronger key. The putty in the fixing stuff should be
mixed with long strong hair or tow, as described for rib
mouldings or ceilings. Hair or tow may also be used
advantageously in fixing Portland or other cement work.
Cast work, when extremely heavy, should be further se-
cured by means of long screws or bolts, placed so as to
pass through the cast work and into the timber, the
casts being bedded with gauged haired stuff and tem-
porarily propped up. The screy^rs or bolts should be
fixed before the stuff is set to a\oid the probable dis-
turbance of the gauged bedding. Before fixing any cast
work they should be placed in position to prove their
correct fitting. Centre, side and end lines should be
made on the surface of the bed to give a guide for fix-
ing. It may be necessary to fix nails at intervals in the
lines to give a further guide.

Mitring Enrichments. — Before fixing continuous or
space cast work, the length and width of the panel or
room should be set out to prove that the mitres are equal-
sided, balanced and have flowing lines. Nothing looka

TERMS AND PROCESSES 161

so slovenly or unworkmanlike as a mitre in an ornament
cut haphazard, with the leading stem disjointed or
springing out of a flower or tendril. If the design is
vertical, say a bed mould or frieze with an alternate leaf
and husk, what can be more offensive to artistic taste
than a part of the leaf on one side and a part of the
husk on the other side of the mitre! There is no ex-
cuse for this want of taste and wanton treatment. A
little time expended in setting out the work will obviate
these defects. Where there are no shrinking and stretch-
ing casts the mitres can be eased by stretching or shrink-
ing the cast work at the joints. Stretching or shrinking
are evils, and it depends on the design of the enrich-
ments which of the two is the lesser, but in most: instances
shrinking is the greater evil. Shrinking does not require
so much labor to make the joints good. Stretching does
not show quite so much, especially if the joint is well
modelled and of the same color. It also gives greater
scope and freedom. It has already been mentioned that
in good shops the breaks or other short lengths are set
out in the shop and that there are stretching and shrink-
ing casts and mitres modelled and made to' facilitate the
formation of good mitres. This latter method is cer-
tainly the cheapest and most satisfactory in the end. The
setting out is best done by cutting a lath as a gauge to
the length of the cast and marking the length of each
cast temporarily on the bed of the cast work from mitre
to mitre. When the mitre has been determined on and
the casts set out to come in, the marks are made more
distant to give a guide for fixing each separate cast as
required. It is better to measure thrice than alter twice.
Space ornaments should also be set out accurately, but
there is no difficulty in the mitres, as the intervening

162 CEMENTS AND CONCEETES

space between each cast can be increased or diminished
as required.

When fixing medallion blocks, dentils or paterae, the
mitres should be fixed first and then the spaces and posi-
tions set out. Special care must be taken when mitring
enrichments with distinctive vertical parts, such as fig-
ures, or pendants of fiowers, or fruit in friezes, that the
cast work is not unequally or irregularly scratched so as
to enable them to come to an equally balanced mitre at
the angles. Where there are no stretchers the cast woA
should be cut between the main vertical parts, so that the
joint on each side will be equal, or, in other words, that
the vertical parts will be equidistant from the main or
other parts when fixed. The same remarks apply to
shrinking. The mitres of running enrichments, such as
soffits, etc., are made up with bands or ribbons, which
are cast or worked in situ by hand. The latter way is
the quickest and most artistic. Another plan is to fix
paterae or drops at the internal and external mitres.
The scroll work of the enrichment is then formed to
spring from the paterae and finish at the patera at the
next mitre. -Sometimes the inner member at each side
of the soffit is worked across at right angles at each mitre,
thus forming a small square sinking or panel, which is
then filled in with a patera or drop.

Bed moulds, such as an egg and dart, have internal and
external mitre leaf modelled and cast. .This is a neat
and quick way of forming mitres. A good cornice, with
well-modelled and effective ornament, may be disfigured
and spoiled by careless mitring, yet it is as easy (and in
many cases more so) to make good and satisfactory
work. It is therefore best to set out correctly and make
sure of a correct finish before beginning to fix. Illustra-

TERMS AND PROCESSES 163

tion No. 8 shows the method of mitring various fonns
of fret enrichments.

Pugging. — Pugging or deafening is a body of plastic
materials laid on bou'ds fixed between the joists of a
floor, or lath and plaster partitions. It is intended to
prevent sound and smells from passing from one room
to another. Pugging is generally performed by laying
a thick coat of coarse stuff on a foundation of rough
boards on fillets, which are nailed on the sides of the
joists. Chopped hay, straw or ferns, mixed with lime, is

.«Fket Oknauents.

NO, 8.

sometimes used for the plastic coat. Coarse plaster with
and without reeds is also used in some districts. Saw-
dust ia sometiitaes substituted for reeds. Pugging may
be done by forming a foundation with thick rough lath
■wood. On this a coat, about 14 ''"'b thick, of coarse stuff
is laid, and when dry a layer about 2 inches thick of dry
ashes or lime riddlings is deposited on it. The upper sur-
face is then sprinkled with water and finished with a coat
of coarse stuff. This makes sound-proof work, but in the

164 CEMENTS AND CONCRETES

event of subsequent damage or alterations the dry ashes
run out, causing further dust and damage. In some in-
stances the dry ashes are gauged with lime. When laid
the upper surface is beaten and smoothed with a shovel.
This makes sound-proof and durable work, impervious to
vermin. Partitions are deafened by lathing between
the studding and then laying on a coat of coarse stuff.
When dry the partition is lathed and plastered in the
usual way. Pugging slabs of fibrous plaster are now
largely employed. They have the advantage of being
light and dry and are rapidly fixed.

Sound Ceilings, — ^No lath and plaster ceilings can be
made sound and free from cracks unless the joists are
well seasoned, firmly fixed and sufficiently strong to
carry the overhead weight, as well as sustain the weight
of the lath and plaster, and resist jarring. Ceiling joists
should never be more than 12 inches apart from center
to center. Where double lath is used the joists may be
14 inches from center to center. Good laths, with break
joints every three feet, and well nailed, are also impera-
tive. If the above dimensions are exceeded the laths
are liable to give or twist on account of the weakness of
the laths or the weight of the plaster, or both com-
bined. If the joists exceed 2 inches in the width they
should be counter-lathed or strapped to ensure a key for
the plaster. Where it is impracticable or inconvenient
to fix the ceiling joists so close they should be brand-
ered. This strengthens and stiffens the joists, also gives
a free key for the plaster and forms a sound, level ceil-
ing.

Brandered or strapped ceilings are done by nailing
wood straps or fillets across the under sides of the joists.
The fillets are from 1^ to 2 inches square and are fixed
from 12 to 14 inches from centre to centre. The sizes

TERMS AND PROCESSES 165

and distance apart varies according to the thickness of
the lath and the class of plaster work. Brandered ceil-
ings are largely used in some places and make good
sound ceilings.

Cracked Plaster TTorfc.— Cracks in plaster work are
due to various causes. They may act individually or in
combination. Cracks are often caused by settlement in
the building. These cracks may be easily discerned by
their breadth, depth and length. They also arise from
the shrinkage of bad or unseasoned timber used in the
construction or framing of the building, which may
cause displacement in the joists or the laths. Cracks
are sometimes caused by the laths being too weak, or by
too much plaster being laid on weak laths, or too little
plaster laid on strong laths. Other causes are the too
sudden drying of the work, strong winds or heat, Ihe
laying of one coat of mortar on another coat, or on walls
that have a strong suction which absorbs the moisture or
'*life" of the coat being laid, when it becomes short, or
crumbly, scaly and apt to peel or fall off. In this last
case it does not set, but only dries and shrinks, which
gives rise to cracks, and eventually falls or crumbles
away. The use of bad materials, insufficient use of lime
and hair, or scamping of labor is often followed by
cracks. Insufficient labor and unskilled workmanship in
the application of the materials is a great source of *
trouble, but it will be understood that the best quality
of labor will not make bad materials good and strong;
and, on the other hand, the best materials will not com-
pensate for bad labor. It is only by judicious selection
of materials and their skillful manipulation that a high
and enduring class of work can be obtained.

Repairing • Old Plaster. — Repairing is also termed
"patching," ''jobbing" and ''making good." When

166 CEMENTS AND CONCRETES

repairing or making additions to old plaster work, care
should be observed in cutting the joints so that the key of
the existing work is not injured or broken. The joints
one way should be cut on the studding or joists and in
a line with the laths the other way. A joint at the edge
of a lath is stronger than at the center. If the lath work
is weak the joints should be cut diagonally. Never use
a hammer to cut joints on lath work, for the repeated im-
pacts will weaken and crack the old work. If the old
plaster is hard, cut the joint with the saw or with a ham-
mer and chisel and finish with a strong knife. Avoid
acute angles in patches. Square, round or oval patches
not only look better but are much stronger than zigzag
ones. Having cut the joints neat and square on edge
and then repaired the old lath work, brush the joints
and the laths with a dry broom and then wet the joints,
but only dampen the lath work, as excessive water tends
to warp the laths. The joints are sometimes painted to
prevent damp from extending to the old work or caus-
ing injury to any surface decoration. Gauged coarse
stuff is generally used for roughing out and gauged putty
for finishing ordinary work. The coarse stuff is gen-
erally gauged with coarse plaster. For small patches
the whole thickness is generally brought out in one coat,
but for large patches it is best to lay a first coat and
then scratch it in the usual way. If time permits this
should stand for one day, or even two, to allow the lath
work to settle. The stronger and stiffer the gauge, the
less power the laths will have to warp. The floating coat
is gauged moderately stiff with coarse plaster or with
fine plaster and coarse in equal proportions.

When laid, the surface is ruled in with a straight-
edge, keeping it within the line of the old work to allow
for plaster swelling and a thickness of 1-16 inch for the

TERMS AND PROCESSES 167

finishing coat. It is often necessary to drag the surface
down to allow the finishing coat to be ruled fair and
flush with the old work. The surface should be left fair
but rough. Gauged work should never be scoured, as it
only kills the plaster, and therefore weakens the body of
the material. The putty for the final coat should be
gauged with fine plaster and a little size water. After
being laid the surface is ruled flush with the old work,
and when firm it should be smartly trowelled off and
finally finished with a semi-wet brush. The joints should
be trowelled flush and smooth and the old part brushed
to free it from any gauged stuff. All rubbish should be
damped as it falls, and removed as soon as possible to
prevent further dust and dirt.

Parian or other white cements are used for best work,
or where time is a consideration. All white cements
having plaster for their basis are manufactured to be
non-efflorescent, non-porous, durable, free from liability
to unequal shrinkage (which causes cracks), and free in
working. They form admirable materials for repairs or
additions. When making good old or broken lime plaster
work with any of these cements, the joints and lath nails
roust be painted with red lead, quick drying paint, or
with shellac. Galvanized nails ought to be used for the
lath work where these cements are to be used. Small holes
and cracks are usually stopped with fine plaster gauged
with putty, or better still, putty water. Parian cement is
also used for a similar purpose. The holes and cracks
should be brushed with Parian solution before the stiff
Parian is applied. This solution is simply fine Parian
gauged to a thin creamy consistency with water. New or
damp lime-plastered walls can be painted or papered
much sooner, and with greater safety, if brushed with a
thin Parian solution. It is also useful for stopping the

168 CEMENTS AND CONCRETES

suction on dry floating and fibrous slabs before laying
the final coat. Severalof the new patent plaster and
white cements are well adapted for repairs, or where
time is limited.

Gauged Work, — ^AU gauged work should be regulated
in strength according to the purpose required. A brick
or stone wall would not require so much plaster as a lath
partition. Work not subject to friction or wear does not
require so much plaster. If the work is required for
immediate use, as with running screeds, or blocking out
large mouldings, or fixing large castings much plaster
must be used. The amount of plaster required for scaf-
fold work varies from 14 to equal proportions for gaug-
ing coarse stuff or setting stuff, and from ^-3 to equal
proportions for coarse stuff for heavy cornices, and 1-3
to equal proportions for putty and fixing ornament. The
amount of plaster also depends upon the quality of the
plaster, some of which are much stronger than others.
Coarse plaster that is of a dark and sandy nature is gen-
erally weak, sets quickly, and becomes soft and useless.
Fine plaster should be used for gauging putty when run-
ning cornices, also for fixing enrichments. All gauged
work should be gauged with uniformity, each separate
gauge having the same amount of water and plaster as
required for the bulk of stuff being gauged. Unequal
gauging causes hard and soft places in the -work, and
when more plaster is used in one gauge thaA another
there is an extra expansion caused by the swelling of
the plaster, which makes the work more difficult to do
when floating, setting, running mouldings, or mitring.

A quart and a pint measure should always be kept on
the scaffold for measuring the water used for the vari-
ous gauges. The quantity of water will regulate the
quantity of plaster for each gauge. A proper plaster

TEEMS AND PEOCESSES 169

box should also be on the scaffold, made to hold a sack of
plaster, and having a lid mJlde in two halves hinged from
the centre. This prevents the plaster from getting dirty
by falling stuff, and from getting damp by absorption
from the atmosphere. Where there is a large quantity
or continuous gauging, the box should be placed on a
stand (this is called a stand-box) to preyent unnecessary
exertion and loss of time by stooping for each handful.

When gauging coarse stuff for large surfaces which
require several gauges to complete the work in hand, size
water should be used in proper proportions with the neat
water used for gauging, so as to allow sufficient time to
properly manipulate the material. In the event of
gauged stuff settings before the work is laid and ruled off,
it is difficult to make the surface strong and fair. This
also allows the various gauges to be laid on or against
the previous ones while they are in a soft state, thus
forming stronger joints and better cohesion between the
various gauges. The use of size water in gauged set-
ting stuff and putty enables the work to be freely trow-
elled and finished. Gauged stuff should not be hand-
floated, as excessive working, destroys the setting powers
of the plaster.

Joist Lines on Ceilings; — Common flat ceilings show
in time the precise position of the joists above, and in
many instances the position and form of the lath work
can be easily discerned. Many theories have been ad-
vanced as to the cause of these unsightly lines or marks,
which are so distressing to the mind and eye. In my
opinion they are due in a great measure to insufficient
material and inferior work. The plaster which is be-
tween or separate from the jibists is more pervious to the
atmosphere than that which is in more direct contact.
The air in passing through leaves behind it particles of

170 CEMENTS AND CONCRETES

dirt assigned in larger measure to the unattached than
to the attached portions. Dust that finds ingress be-
tween the joints of floorings boards lies on the unattached
portions, consequently the joists show themselves as
lighter lines on a more or less dirty background. The
same causes apply to the lines on the lath work. An-
other cause is that the plaster work is too thin. In many
instances the floating is brought up from the lath in one
coat. This is a most pernicious habit, as it is not only
the cause of lath lines, but the ceiling invariably cracks,
and develops spontaneously original patterns indicative
of rivers, which too often lead like Niagara to a catas-
trophe in the form of falling plaster. Joists and lath
lines on thin ceilings may be partly obviated by laying
strong brown paper over the upper side of the lath and
plaster and then pasting the edges to the sides of the
joists, so as to form a cover to the plaster work. The
better and most sanitary way is to lay the work in three
coats, allow the first coat to dry, consolidate the floating
coat by well scouring with a hand float, and render the
setting coat hard, non-absorbent, and impervious to the
air by thorough scouring, trowelling, and brushing.

Rough Casting.

Several years ago I was requested by the Editor of
** Architecture and Building" of New York to prepare a
short treatise on the subject of ** Rough Casting" for
publication in that magazine. The article was pub-
lished in almost every architectural journal in the coun-
try, and Mr. Kidder embodied it in his excellent work,
*' Building Construction and Superintendence, Vol. I. *'
I reproduce it here, as the directions given therein have
been found to be of the very best, and most workmen in

TERMS AND PROCESSES 171

this line of the trade adopt the methods of manipulation
herein described.

** Rough casting, or, as it is sometimes called, slap
dashing, both of which are synonymous with the French
hourdagey rough work, and ravalement, having a similar
meaning, is a method of plastering the outside of a build-
ing much used in the northern part of Canada because
of its being durable, cheap and well adapted to keep out
cold winds during the long winters in that section of
the world. The methods of applying rough cast and the
mixing thereof do not materially differ from the meth-
ods adopted in Northern Europe or even in the North-
western States, but it is these minor differences, says a
writer in an exchange, that make the Canadian rough
casting superior, so far as durability is concerned, to
much that is done in other parts of the world.

There are frame cottages near the City of Toronto and
along the northern shores of Lake Ontario that were
plastered and roughcasted exteriorly over 40 years ago,
and the mortar today is as good and sound as when
first put on, and it looks as though it was good for many
years yet if the timbers of the building it preserves re-
main good. Rough cast buildings are plentiful in every
province in the Dominion from Halifax to Vancouver
and from Lake Erie to Hudson Bay, and when well built
and the rough cast properly mixed and properly applied
the result is always satisfactory. It is quite a common
occurrence in Manitoba and the Northwest Territories
in the winter to find the mercury frozen, yet this inten-
sity of frost does not seem to affect the rough casting in
the least, though it will chip bricks, contract and expand
timber, and render stone as brittle as glass in many
eases, and the effect on iron and steel is such as may

172 CEMENTS AND. CONCRETES

prove dangerous if exposed to sudden and unexpected
strain.

In preparing a frame or log building for rough cast-
ing care must be taken in putting down the founda-
tion. A good stone or brick foundation is, of course, the
best, but where rough casting is intended stone or brick
foundations are seldom used because of their cost, and
the builder is compelled to use posts of wood. The
posts are generally made of white cedar, which has a
lasting quality of 35 or 40 years if sound when used.
The posts are put in the ground from 3 to 5 feet, the
deeper the better, as they should be deep enough in any
case to prevent frost from forcing them upward. When
a sufficient number of posts have been properly placed
a line is struck on them a proper height from the ground
and the tops levelled off. The sills are then placed — all
joints being broken on top of posts — ^and the whole made
level. These sills and al] the other timber, scantlings
and lumber should be well seasoned, if possible, for the
greatest enemy to the plasterer is unseasoned timber;
shrinkage of joists, posts and scantling not only breaks
the bond of the mortar, but causes great cracks in cor-
ners and angles that no amount of pointing or patching
can ever make good.

When the frame is up and the rafter on and well se-
cured the whole of the outside should be covered with
good, sound, common inch stock pine] hemlock, spruce,
or other suitable lumber, dressed to a thickness. If put
on diagonally so much the better, but this is not abso-
lutely necessary if the rough casting is to be of the best
qu^ity, as will appear hereafter.

When it can be done it is best to get all partitions set
in place and lathed, the roof on and all necessary out-
side finish or grounds put in place and made ready to

TBEMSlvANDlPEaCESSES 1*73

receive the lath. The cfirpenter must prepare his finish
or grounds for finish ta accommodate the extra lath, as
the walls will be thickened. accordingly.

For the cheaper sort of rough casting in one or two
coats the following method 'Of lathing is employed : Nail
laths on the boarding-— over paper or felt, if paper or
felt is used — perpendicularly 16 inches from centre to
centre if 4 foot laths are Used, or 18 inches or 1 foot
from center to center if 3 foot laths are used. The whole
surface to be rough cast will require lathing this way.
When done lath as is ordinarily done with No. 1 pine
lath, breaking joints every 15 inches. Put 5 nails in
each lath, driving each nail home solid, coat over with
mortar, well haired, and that has been made four or more
days; smooth and straighten as well as possible with a
darby. When done and while yet soft the rough cast is
thrown on it with such force as to drive the pebbles or
small stones deep into it. The mixture or dash, as it is
tailed, is composed of fine gravel, cleto washed from all
earthy particles and mixed with pure lime and water
till the whole is of a semi-fluid consistency. This is
mixed in a shallow tub or pail and is thrown upon the
plastered wall with a wooden float about 5 or 6 inches
long and as many wide, made of ^ inch pine, and fitted
.with a wooden handle. While with this tool the plaster-
er throws on the rough cast with his right hand, he holds
in his left a common white*wash brush, which he dips
into the rough cast and then brushes over the mortar
and rough cast, which gives them, when finished, a reg-
ular, uniform color and appearance.

For this sort of work the following proportions will
answer : To one barrel of prepared gravel use a quarter
of a barrel of putty; mix well before using. This may
be colored to suit the taste by using the proper materials.

174 CEMENTS AND CONCEETES

•

as given further on. It must be understood that the fore-
going is the cheapest sort of rough casting, and is not
recommended where more durable but more expensive
work is required.

The best mode of doing this work as practised in the
Lake district of Ontario is nearly as follows. Have the
frame of building prepared as indicated in the foregoing,
with partitions all put in and well braced throughout and
well secured. Lath diagonally with No. 1 pine lath,
keeping ll^ inches space between tha lath. Nail each
lath with 5 nails, and break joints every eighteen inches.
Over this lath again diagonally in the opposite direction,
keeping the same space between the lath and breaking
joints as before. Careful and solid nailing is required
for this layer of lathing, as the i)ermanency of the work
depends to some extent on this portion of it being honest-
ly done. The mortar used for the fir^t coat should have
a goodly supply of cow's hair mixed in with it, and
should be made at least four days before using. The
operator must see to it that the mortar be well pressed
into the key or interstices of the lathing to make it
hold good. The face of the work must be well scratched
to form a key for the second coat, which must not be put
on before the first or scratch coat is dry. The mortar for
the second coat is made in the same way as that re-
quired for the first coat, and is applied in a similar man-
ner, with the exception that the scratch coat must be
well damped before the second coat is put on in order
to keep the second coat moist and soft ointil the dash or
rough cast is thrown in. The rough casting is done ex-
actly in the same manner as described for the cheaper
sort of rough cast work.

A building finished in this manner, if the work is well
done, possesses many advantages over the ordinary

TERMS AND PROCESSES 175

wood covered structure. It is much wanner being al-
most air tight so far as the walls are concerned. It is
safer, as fire will not eat its way through work of that
kind for a long time. It is cleaner, as it will not prove
such a harbor for insects. It may be made as handsome
as desired, for before the rough cast is dashed it may be
laid off in panels of any shape by having strips of bat-
tens tacked over the soft mortar, which may be removed
after the rough casting is done and the coloring finished.
It is much superior to the so-called brick veneered house,
as it is warmer, more exempt from fire and cheaper.

For 100 yards of rough casting in the manner
described the following quantities will be required : 1800
laths, 12 bushels of lime, 1% barrels of best cow hair,
1% yards of sand, % yard of prepared gravel and 16
pounds of hot cut lath nails, ll^ inches long. The gravel
should be sifted through a ^ inch mesh screen, and
should be washed before mixing with the lime putty.

To color 100 yards in any of the tints named herewith
use the following quantities of ingredients : For a blue
black mix 5 pounds of lamp black in the dash. For a
buff use 5 pounds of green copperas, to which add 1
pound of fresh cow manure ; strain all and mix well with
the dash. A fine terra cotta is made by using 15 pounds
of metallic oxide mixed with 5 pounds of green copperas.
A dark green color is made by using 5 pounds of green
copperas and 4 pounds of lamp black. Many tints of
these colors may be obtained by varying the quantities
given. The colors obtained by these methods are perma^
nent; they do not fade or change with time or atmos-
pheric variations. Many other colors are used but few
stand like the ones named. A brick color may be obtained
by the use of Venetian red and umber mixed in whisky
first and then poured into the dash until the proper tint

176 CEMENTS AND CONCRETES

is obtained. In time, however, like all earthy pig-
ments, these colors fade and -have a sickly appearance ;
they answer better in cements than when incorporated
with fat limes. ^

VAEIOUS METHODS OF RUNNING CORNICES,

CIRCLES, ELLIPSES AND OTHER ORNAMEN-
TAL STUCCO WOEK.

Diminished Columns. — The diminishing of columns is
an interesting but somewhat difficult operation. Great
care must be exercised not to overdo the entasis or swell-
ing. The swell may commence very gradually from the
base to the capital, or the third part of the column njay ^
be of the same diameter, and then swell and diminish for
the remainder of its height. Two methods are here given
to show how this may be done. These are given more
to illustrate the method of setting out the diminished
floating rulea — so necessary to the plasterer — ^than to
define the swell or diminishing of a column, which, being
within limits a matter of taste, pertains more correctly
to the architect.

The best instrument for forming a diminished column
(plain or fluted) is a diminished floating rule, with a
cutting edge made to the contour of the proposed col-
umn. This rule is used to determine the central posi-
tion of the astragal and base mouldings (which act as
bearings when ruling oflf jthe floating stuft' and the finaJ
coat), so as to obtain a true and uniform diminish, and
also to form a fair surface. The appended illustration
No. 9 elucidates the method of setting out diminished
oolnnms which is also used for setting out the diminished
rule for both columns. The method for setting out a
diminished rule for a column thjit diminishes two thirds
of its height is as follows : The dimensions of the column

177

CEMENTS AND OONCEETES

METHODS OF WORK 179

having been fixed, i. e., the height of the shaft and its
upper and lower diameters, draw a perpendicular line
which may be taken as the centre line of the column;
then set out the upper and lower diameters, as shown in
Pig. la. This figure also shows one-half of the con-
structural brick work, and the plaster, which is dis-
tinguished by being dark shaded with the floating rule
in position. A floating rule for forming the curved and
diminished surface requires an iron plate, similar to a
mould plate, as shown, so that it will cut the stuff off
cleaner and truer, and last longer. The other half of the
elevation shows the lines and divisions for obtaining and
setting out the entasis.

To diminish the column, first divide the height into
three equal parts then at the lower third (5) draw a
semicircle equal to the lower diameter. of the column.
Next divide the upper portion of the column into four
equal parts, as shown at 1, 2, 3 and 4, then draw a line,
parallel with the axis or centre line of the column, from
figure 1 at the top of the column, cutting the semicircle
at 1, divide the remainder of the semicircle into four
equal parts, which gives the diminishing points. From
these points draw lines parallel to the axis of the column,
and from the corresponding figures, or from 2 to 2, and
so on. In these intersecting points fix pins or nails, and
bend a flexible strip of wood or metal round the nails,
and draw the curved line. The whole line from top to
bottom is then transferred on to the board that is to be
used for making the floating rule. This column will have
its greatest diameter for one-third of its height, and the
upper portion its entasis. This method is so far defect-
ive as to require the curve to be drawn by baud, a de-
fect, however, obviated by using a column trammel,
which is used for. a column that diminishes with a grace-

180 CEMENTS AND CONCRETES

f ul curve from the base to top of the shaft. This ti^ammel
is made as follows:

Column Trammel. — ^A column trammel is simple in
construction, and when carefully used gives very satis-
factory results, forming a graceful diminished curve
from the lower diameter to the upper diameter of the
shaft. Before describing the method of setting out and
constructing the column trammel, the method of finding
the point D on Fig. 2 is given on a separate sketch (Fig.
5) to show the method more clearly.

Fig. 5 illustrates the method of obtaining the point D,
on which the centre pin is fixed for the trammel to
slide on while working. This point also gives the length
of the radius-rod. This sketch is reduced one-half in
size to that of Fig. 2a, but the letters correspond to it.
Having set out the axis or centre line of the column (A
B) and the base line (A C) (extending the latter indefi-
nitely) as described for Fig. la, proceed as follows. From
A as a centre, and from A to B as a radius, describe an
arc, as indicated by the dotted line; then from the in-
tersecting point at C as a centre, and from C to the
point at B as a radius (as indicated by the dotted line),
describe an arc until it cuts the base line at K. This
done add the distance from the point at A to the point
at K to the base line, outward from the point at C, which
gives the desired point D.

The trammel should be set out on a wall or a clean
floor. To set it out, first draw a line to the exact height
of the proposed column, as A B on Fig. 2a, then draw
a line (indefinitely in length) at right angles to A B, as
shown from A to D. This line A B is the axis or centre
line of the column, and the line A D is the base line. To
construct the trammel, take two rules, each the length of
the column,* and about 2 inches wide, and 1^ in. thick;

METHODS OF WOKK 181

fix one on eacH side of the axis of the column, taking care
to keep them equidistant and parallel to the axis, and
forming a grooved space about 2 inches wide, as shown
at a, a, the rules, and b the groove. These rules are
made thicker than the board intended for the floating
nile, so ajs to allow the trammel pencil to run freely
when marking the diminished line on the board. This
is shown by the section at Fig. 1. This is as when done
in a temporary way on a floor, but a better way is to
fix the rules on a board (a flooring board will be found
suitable). This makes a permanent groove, and forms an
easy ground for the sliding block to work smooj:hly . It
also allows a greater space for a thicker board for the
floating rule.

Fig. 2 shows enlarged details of the groove rules (A,
A,) the groove (b,) the sliding block (B), with the pin
(H), the radius-rod (F), with the pencil (G), and the
board for the floating rule (C), with the diminished
line. Fig. 1 shows a section of Fig. 2.' The letters in
all figures correspond with each other. Fig. 2a shows
the whole column with the trammel and finished floating
rule (C). Make the radius-rod about 2 inches wide, 1
inch thick and in length a little longer than the distance
from D to B, and the half diameter of base of the shaft.
The sliding block (H) is about 4 inches long and equal
in depth and width to that of the sliding groove (b). It
should be made smooth, and flt the groove easily, so that
it will slide ireely from end to end when working. In
the exact centre of the block fix a hardwood pin or a*
round nail (H). This must be fixed exactly over the
axis of the column, and so fitted that it will run imme-
diately over it from end to end. Bore a hole in the ra-
dius-rod to fit this pin, then from the centre of the pin
set off exactly half the diameter of the base of the col-

182 CEMENTS AND CONCRETES

umn on the radius-rod, which will give the point for
the pencil hole (G). At this point bore a hole large
enough to receive a pencil, which must be tightly held in
it. At the lower end of the radius-rod cut a slot just
wide enough to receive the center pin at D.

A plan of the radius-rod with the slot and centre pin
is ishown at Fig. 3 and a section at Fig. 4. The block
beneath the radius-rod, in the section is used to keep the
rod level with the rules and sliding block, as shown on
Fig. 1. To ascertain the length to cut the slot, place the
radius-rod along the line A D,,and the pencil at the out-
side of the semi-diameter at the base of the column, and
slide it to its place ; mark on the rod where the centre
pin (D) comes; then place the pencil end of the rod at
the top diameter, and mark the rod again at the centre
pin ; this will give the length of the pin. Having made
the trammel, provide a stout board to form the floating
rule (cc). This board should be planed on both sides
and one edge. Place it near the rules a a, keeping the
planed edge outwards, and parallel with the axis or
centre line of the column. This allows the planed edge
of the floating rule to be used as a straight edge to
plumb by when fixing the top and bottom rims or mould-
ings, which are used as guides and bearings when float-
ing the column. Place the sliding block in position, and
lay the radius-rod over the center pin, and the p,in of the
sliding block, keeping the rod in a line with D A, tak-
ing care that the pencil is in its true position ; then care-
fully move it upwards, and pressing the pencil gently
upon the board which will give the line for cutting the
diminishing floating rule. The floating edge is strength-
ened by nailing a strip of sheet iron on the board in a
similar way to that in which a mould plate on a running
mould is treated. This is of special use when floating

METHODS OF WORK 383

diminished fluted columns or pilasters, as the thin and
sharp edge allows the flutes to be more easily formed.
The diminished line on the metal plate can also be
fonned with the trammel.

A column trammel can also be used for setting out
other diminished floating rules for columns less in size
than the original one. The only alteration required for
this purpose is to alter the point D to suit the size of flje
proposed column, and the shortening of the radius-rod.
It will be seen that the floating rules for both columns
are made long enough to bear on the base and necking
mouldings, but it is usual to make them shorter so as to
bear on cast or run rims or collars, which are fixed at
the top and bottom of the shaft.

Constructing Plain Diminished Columns. — ^Plain
diminished columns and pilasters are formed with a
diminished rule fashioned at both ends to work on the
necking and base mouldings (termed rims), or on collars.
The method of making rims and collars, which are used
as bearingis, is as described for diminished fluted
columns.

To Set out the Flutes of Diminished Column. — The
annexed illustration No. 10 elucidates the method of set-
ting out the flutes of a column. Fig. 1 shows the half
plan of a column; A is the plan of the flutes at the base,
and B the plan at the top of the shaft. Fig. 2 shows the
elevation of the column, with the various parts marked.
Pig. 3 shows the plan and centres for setting out the
flutings for the different orders with arrises or with fil-
lets. A fluted column may be divided into twenty,
twenty-four, or twenty-six flutes, according to the style
0/» 0rder. There are two different sorts of flutes used.
/J is worked to an arris, and sunk down in, different
^^ths, one of which is described by the fourth part of

184 CEMENTS AND CONCEETES

— DmiNisHFjj nuTEB Columns.

so, ID.

METHODS OF WORK 185

the circle, one by the sixth, and others by the half
circle, ais shown at C, D, E, Fig. 3.

The square or fillet of the sepond .kind is equal to one-
third part of the flute. It will be seen in Fig. 2 that
two lines are shown at the top of the flutes. The lower
one shows how the flutes finish, when the fourth and
sixth depths are taken, and the top line when the half-
circle is taken together with the fillets. Flutes that
finish with an arris are usually employed for columns in
the Doric order, and those that finish with fillets are used
in the other orders. The fillets or lists at the top and
bottom of the shaft of a column, which serve to divide
the shaft from the capital and base mouldings, are com-
monly called the upper and lower fillets, and sometimes
the horizontal fillets, but in architecture they are known

as ** cinctures." The curved parts at the top and bottom
of the shaft which are usually curved into the upper and
lower fillets by a concave curve or inverted cavetto, are
in architecture termed **apophygis."

Constructing Diminished Fluted Columns. — The
formation of diminished fluted columns by means of a
running mould is an absorbing and vexed topic among
plasterens, and many ingenious plans have been advanced
for the construction of hinged and spring running
moulds, and diminished running rules. I have known
more than one self-improving plasterer who has ex-
. prided a vast deal of time and lime (not forgetting
plaster) to prove by actual practice the possibility of
running a diminished fluted column, while others have
been content to work them by theory, forgetting that an
ounce of practice is worth a ton of theory. Some men
thought they had accomplished a feat when they had
ran a single flute with a hinged mould, between two run-
xuDg rules fixed to form diminution in width, forget^'

186 CEMENTS AND CONCRETES

ting or not knowing that flutes diminish in depth a& well
as width.

The difference in depth of flutes, at the base and the
top of the shaft, is shown at A, the base, and B, the top,
in Fig. 1, illustration No. 10. Running moulds have also
been made with springs to regulate the diminish in
depth, but their action was uncertain, and they are also
too expensive for the purpose. Another form of run-
ning mould was made by fixing wire, catgut, or leather
on one end of one of the slippers, and on the upper edge
of the stock, jso that the slipper, when being forced up
the diminished space between the running rules, became
more angular, or in other words, the slipper on which
one end of the wire was attached was higher up the
diminished space than the other slipper, and thus caused
the stock to cant forward, or be drawn out of an up-
right, and reduce the depth of the flute. The stock in
this case is connected to the slippers not by hinges, but
by a pivot inserted at each slipper to allow the stock
to cant forward when pulled by the wire. This form
of mould also proved to be too erratic in its working
to be of useful service. Running moulds having the
stock connected to a slipper at each side by means of
two hinges (termed a double-hinged mould) allow the
mould to assume an angular or slanting form as it passes
up the diminished space, thus forming a, diminution in
the width of flute, but it does not form it with a true
arc all the way. On the contrary, it assumes an elliptical
form which becomes more and more pronounced as it
reaches the top of the shaft.

The nearest approach to perfection in running dimin-
ished flute is performed by means of a running mould
made with hinged slippers as described, but having the
mould plate and stock cut through th^ centre of the

METHODS OF WORK 187

profile, the two parts being then connected' by a hinge.
This form of running mould (termed a ** triple-hinged
mould") allows the mould to collapse in the form of a
V on plan, and the slippers to run level or parallel with
each other, thus forming each half of the flute alike, and
at right angles from the centre. Still this has the defect
of forming the flute without the necessary decrease in
depth.

A method for diminishing the depth of the flutes is to
make the running rules with a diminish on face, or
rather to make them with an increasing thickness towards
the top ends, so that the mould when running up on the
increasing thickness will form a corresponding de-
creased depth of flute. When running a fluted column
by this process, the running rules are fixed flush with
the face line of the fillets. Only one flute can be run at
a time, but twelve may be in band at the same time. As
there are generally twenty-four flutes in a column,
twelve rules would be required to keep a couple of
plasterers going. .When the fl^rst set of flutes are run,
the rules are taken off and flxed to run the remaining
flutes. When all are run, the returned ends at top and
bottom require to be made good. It will be seen that the
running rules for this method must be carefully made
and fixed to ensure true lines and forms. It will be
understood that a bed or ground must first be formed
as a guide for setting out and fixing the running rules
on. This is done with the aid of a diminished floating
rule. It will also be self-evident ^hat the floating rule
would be more profitably employed for forming the
entire shaft with the flutes, thus dispensing with run-
ning rules and hinged moulds. This method of running
the flutes is slow and tedious, but the worst part is that
the flutes are not true segments ; in fact, the whole of the

188 CEMENTS AND CONCRETES

methods mentioned are more or less a rule of thumb, un-
certain and inaccurate.

A knowledge of the rudiments of geometry will prove
that the true form of a diminished and swelled fluted
column cannot be run with a mould, however ingeniously
made. This may be proved by cutting a plaster or card-
board disc to the former radius of a single flute, and de-
scribing a line round it on a board. This would be the
form the mould, when at right angles at the bottom of
the shaft, would give the flute. Then place the disc in
an oblique position (the same as the hinged mould would
be at the top), and project the plans by means of a set
square on to the board. It will be seen that the mould
would give the flute an elliptical form. It may be
further explained by stating that when the mould is
square at the base, or at right angles with the vertical
running rules, the form of the flute would be a true
segment; but when the mould is moved up the dimin-
ished spa<3e between the rules, it assumes an oblique or
slanting position. It gives the flute an elliptical form,
which increases and becomes more pronounced as it ap-
proaches the necking. It may be said that the pointed
or elliptical defects can be filled in and worked fair
with circular hand floats, but this plan necessitates a
series of hand floats to fit the ever-varying widths and
depths of the flutes.

It may seem unnecessary^ to describe the above meth-
ods, and then to point out their defects. However, the
methods and defects are given to prevent the rising plas-
terer falling into the same errors, and to enable him to
resist and rebut the arguments that are so often ad-
vanced by some men, who persistently assert that their
own particular way (generally one of the methods at

METHODS OF WOEK 189

ready mentioned) is the correct and only way of proper-
ly performing this different but interesting operation.

It is worthy of note, to show the interest taken in
this subject that a patent was obtained for a running
mould and process for forming diminished fluted col-
umns, in 1878, which obtained a provjpional protection
for ** improvements in moulds or templates for running
stucco or cement tapered- fluted columns/' The follow-
ing is a copy of the specification in extenso.: —

This invention relates to the running of stucco or ce-
ment in forming fluted or other columns, pillars, or pi-
lasters, and similar surfaces, in a more simple, economi-
cal, and expeditious manner than heretofore; and the
nature and novelty of the invention as applied for run-
ning or making the body part of a fluted tapered col-
unm of stucco or cement, consisting in constructing a
short box-shaped template, having two sides joined to-
gether by a back plate outside, with a handle upon it,
for drawing it up and down the column, and with an
open space inside the back between the sides open above
and below, equal to any desired section or segment of
the column at its base or widest part, into which the
column is equally divided by narrow longitudinal
strips of wood, against which the inner edge and end
surfaces of the sides of the template slide close, so as to
prevent the escape of the semi-liquid or stucco. A thin
elastic segmental mould plate is hinged or jointed at its
ends to the inner faces or edges of the template, formed
in its inner scraping edge to correspond to the segmental
curve of the base of the column, with rounded pro-
jections corresponding to the flutes to be formed on the
column. This, plate and its hinges are laid at an . angle
highest at the inner scraping edge, and inclined down-
wards towards the back, leaving a space between it and

190 CEMENTS AND CONCRETES

the back for the free passage or escape of the super-
fluous stucco or cement scraped off the column during
the ascent of the mould along the column on its longi-
tudinal shaping strips before mentioned.

**The one end or side of the mould is made to slide or
contract laterall}^ in slots or other equivalent guides in
the back of the mould frame as it ascends along the con-
tracting or tapering longitudinal laths, the thin plate
bending or yielding down in a curvilinear form on its
end hinges before mentioned, so as to bulge inwards while
bending downwards^ and so contract the column in a
nearly true radical and segmental form from the bottom
to the top of the column, the angle at which the scrap-
ing mould plate is set on its hinges determining this con-
traction of the scraping centre edge of its segment radi-
cally in a ratio corresponding to the contraction of the
lengths of the segment and moving sides of the mould,
which, for large moulds and columns, might be car-
ried and drawn up by handles secured to the tops of
the ends of the moulds with ropes led up and over pul-
leys at the top of the column, thence down to the hand
of the operators, so that the mould may be raised and
lowered at pleasure to form the whole segment of the
column from the bottom to the top in nearly as simple
and efficient a manner as plain mouldings are at present
run by the usual simj^le edge scraping moulds, one seg-
ment being run after the other in succession until the
column is finished.

•'For plain or other forms of columns the inner scrap-
ing edge of the mould plate is made to correspond to the
tapered surface of the column to be formed plain, seg-
mental, or fluted as desired ; and for flat, square, or polyg-
onal columns, which do not require a segmental moul^
scraper, this would be made straight, either plain or

METHODS OF WORK 191

fluted, as desired on its scraping edge, and set horizontal-
ly on its hinges, instead of at an angle as described for
the segmental mould scraper for forming round col-
umns ; and this mould scraping plate in any case is pre-
ferred to be made of thin elastic steel or tempered cop-
per or brass, which would bend and contract the flutes or
ridges on the surface of the columns or pillars, equally
and proportionally to the several parts of the column
over which the mould is traversed. Although the mould
or template has been described as made with only one
of its ends movable laterally, it is to be understood that
both ends or sides may be fitted so as to move in a
similar manner to suit different kinds of work.

This patent method would be better understood if it
had been illustrated. No provision for diminishing the
depth of the flutes is given in this method. The use of
flexible metal for diminishing purposes cannot be relied
on for accurate work.

Another method for forming diminished fluted col-
umns is thus performed : — ^Make a single flute in plaster,
and use it as a mould for casting reverse flutes composed
of fibrous plaster. After casting as many reverse flutes
as there are flutes in the proposed column, indurate them
with litharge oil or parafiSn wax. Casts of the necking
and base, each with about 3 inches of the fluted shaft, are
fixed on the brick core. The shaft is then laid with
Portland cement (or other desired cement) and sand un-
til within about one-third of the line of fillets, and
while this stuff is still soft, take a reverse flute
(previously oiled) and press it into position, using the
cement flutes at the necking and base as guides for flx-
ing, and using a diminished floating rule to prove the
outline. Repeat this process until all the flutes in the
column are filled with reverse flutes. The intervening

192 CEMENTS AND CONCRETES

spaces or fillets are then filled in with gauged cement
until flush with the outer surface of the reverse flutes,
and further regulated with the floating rule. When the
stuff is set, the reverse flutes are extracted, and any de-
fects in the flutes made good. On the care in fixing the
reverse flutes and filling in the fillets .depends the success
of this method.

Diminished fluted columns are also made by casting
two vertical halves, and then fixing them on the brick
core. The halves are fixed by means of cement dots,
which are laid on the core at intervals. (Corresponding
dots are laid on the interior of the casts. The casts
are then pressed on the core until the dots meet, and
both halves are in proper position. The cast work is
made solid with the core by pouring a thin and weak
solution of cement and sand into an orifice at the neck-
ing.

The cement and sand should be mixed jn the propor-
-tion of one of the former to five of the latter. This
gauge has suflScient binding power and strength for this
purpose, and is not liable to expand or contract in wet or
dry weather. This process is useful for small work, and
makes a good job when cleanly cast and neatly fixed. The
necking with the capital and the base may be fixed be-
fore or after the shaft casts are fixed, according to cir-
cumstances. The shaft casts are best formed in a reverse
casting mould.

Another method of casting a diminished fluted col-
umn is effected by making a reverse casting mould. Fix
it round the core, and pour the gauged material in at
the top of the necking mould. By using a reverse
casting mould made with a plaster face and a wood back-
ing, or a mould made in fibrous plaster, the whole
column with the core can be made in one piece. Hoi-

METHODS OF WORK 193

low columns, composed of Portland cement concrete,
can be made to carry any weight supported by a stone
column, or one constructed with a brick core of equal
diameter. Cast hollow columns are made by temporarily
fixing a wood or fibrous plaster core tapered to one end
to allow it to be withdrawn when the concrete is set. A
rough wooden or a fibrous plaster hollow core is used
when casting a hollow column in situ. The core in this
case is left in.

After many years' experience and observation on this
subject, I am of opinion that the true form of a dimin-
ished fluted column (composed in Portland or similar
cement, and constructed in situ) is best obtained by
hand, with the aid of cement rims or plaster collars
and a diminished floating rule. Most plasterers will
admit that what can be and is done in stone or wood,
can be done equally well in cement or plaster. A plaster-
er has one advantage, inasmuch as he can add as well
as subtract when forming circular surfaces, whereas the
mason can only subtract. The two methods hereafter
given for forming diminished fluted columns by hand
are simple, speedy, and accurate. They are on one prin-
cipal, and each may be used as circumstances require:
one is termed the **rim method," and the other the
''collar method.''

Forming Diminished Fluted Column by the Bim
Method, — First make models of the half circumferences
of the astragal or necking and base mouldings, each
having about 4 inches of the fluted shaft, as shown at
Fig. 1, the plan and Fig. 2, the elevation, on illustra-
tion No. 10. To make the models, cut a mould plate to
fit each of the full-sized mouldings, and the required
size of the shaft, and *' horse" them with radius-rods,
and run a little over one-half of each circumference in

194

CEMENTS AND CONCRETES

plaster, and then cut them to the exact half circumfer-
ence. This done, set out the flutes, then cut them out
and form the returned ends. The method of setting out
the flutes on the ends of the models is shown on the plan
at Fig. 1. A is the plan at the base, and B the plan at
the top of the shaft. The returned ends x)f flutes are
shown on the elevation. Fig. 2. Add the square plinth
to the base, as shown on the plan at Fig. 1, which com-
pletes the models. Piece mould the models in plaster,
and then cast as many half astragal and bases as re-
quired. The materials used for the casts must be of the
same kind as intended for the shaft. The brick or core
of the column is now cleaned and well wetted, and then
the astragal and bases are fixed in position, using the
diminished floating rule to prove if they are central, and
the flUets Unable with each other. Apply a plumb rule
on the back edge of the floating rule to test if the astragal
and base are concentrical and parallel with each other.
When these half casts are fixed together on the shaft they
are termed **rims.'' The intermediate space oh the
shaft is then filled in and ruled oflf with the diminished
floating rule; using the rims as bearings and guides for
forming the fillet line of shaft.

The methods of forming a diminished fluted column
by the ''rim method" is further elucidated by the an-
nexed illustration, No. 11. This shows an elevation of
the brick core of a shaft with the astragal rim, A and
the base rim, B, fixed in position. D is the diminished
floating rule in position for floating the main or fillet line
of the shaft. The method of using a diminished flute
rule for the flutes is illustrated in the ** collar method."

A second diminished floating rule is required to form
the back surface of the flutes. This can be quickly mada
by laying the first rule flat on the floor, and from thifi^

METHODS OP WORK 195

'witli compasses, describe the back line of the flute on
another board, which is afterwards cut to tiie desired

•f'LOATtiD Fluted Coi.u.

NO. 11.

line.' This rule is used as a long joint rule to form the
flutes. The rule should be worked with uniform pres-
sure, the man at the top working in unison with the man

196 CEMENTS AND CONCRETES

at the bottom, both working the rule with a eirculax
cutting motion. The flutes are fined down by the aid of
a small float semicircular in section. For extra lai^e
columns three floats should be used — ^No. 1 cut to the
top section, No. 2 cut to the middle section, and No. 3
cut to the bottom section. The length of the floats may
vary from 5 inches to 7 inches, according to the height of
the column. If the columns are required with a smooth
surface, the flutes are worked as above, but the floats are
covered with fine felt, leather, or rubber, and the sur-
face finished smooth with short joint rules or with pieces
of flexible busks. The cast parts of the shaft, to the
fillet members of the astragal and the base, should be
keyed with a drag, so that the whole shaft, from arris to
arris. of the astragal and base fillets^ can be fined, thus
giving a uniform texture and color, and avoiding a sur-
face joint of the cast work and the fined work.

A modification of this method is as follows: — The
lower horizontal fillet of the shaft and the base mouldings
are cast separately, the fillet part being used as bear-
ings for floating the shaft, as already described, and the
base is flxed after the shaft is fined. This plan is useful
for some purposes, such as for extra large columns, as it
gives more freedom for working the shafts and the bases
are not so liable to get injured while working over them.

Running Diminished Fluted Column by the Collar
Method, — Eun a plaster collar about IV2 inches wide to
the diameter of the top horizontal fillet of the shaft.
The thickness must be regulated eiccording to the space
between the brick core and the line of fillet. Cut this
collar in halves and fix them on the brick core, keeping
the under side in a line and level with the top of the
proposed fillet of the shaft. Kun another collar to fit
the horizontal fillet at the base of the shaft, and fix the

METHODS OF WORK 197

upper side of this one level with the bottom edge of the
fillet at base of the shaft. This done, make two plaster
models of the flutes, one for the top and one for the
bottom of the shaft, each about 3 inches wide, and in
thickness according to the brick core, the diameter being
taken about 1 inch above the returned ends of the flutes
at the top and bottom of the shaft. These models are
set out and made as described for the flrst method, but
using plaster instead of cement for the casts. The plaster
casts are fixed in position, and then the brick core is
laid and ruled off, using the main diminished floating
rule (and the plain collars as bearings) for forming the
main contour or line of the vertical fillets, including the
horizontal or top and bottom fillets of the shaft, and
using the diminished flute floating rule (and the plaster
models of the flutes as bearings) for forming the flutes.
This done, the fluted collars are cut out, the spaces filled
in and ruled off, and the returned ends of the flutes
are formed, and then the whole shaft is fined while the
work is green. The fillet collars are then cut out, and
the astragal and base mouldings are then fixed, thus
completing the column. ll will be seen that this method .
entirely dispenses with joints between cast and floated
work on the shaft, and allows it to be fined in one opera-
tion.

The method of running diminished fluted columns
with the aid of collars is further elucidated by the an-
nexed illustration No. 12. A C is the top fillet collar, B C
the bottom fillet collar, and F C and F C are the top and
bottom flute collars flxed on the brick core of the column.
D B is the main diminished floating rule in position for
forming the main contour or fillet line of the column.
This rule is rebated at the top to allow for a bearing on
the top as well as on the edge of the collar. This rule

198 CEMENTS AND CONCRETES

also forms the profile of the top and bottom horizontal
fillets, and the curved parta of the shafts below the top
fillet and above the bottom fillet. F R is the Ante

Forming Fluted Columns — Collak Method.

floating rule in position when forming the flutes. The
ends of this rule as shown bear on the ba«k surface of
a flute as indicated by the dotted lines. A portion of the
astragal moulding, A, with a part of the shaft is shown

METHODS OP WORK 19ft

80 as to indicate the position to fix the fillet collar, A C ;
a portion of the base moulding, B with a part of the
shaft, is also given to show the position of the bottom
fillet collar, B. C. It will be seen that these collars form
fair bed for the astragal and base mouldings, and when
taken off they leave true joints as indicated by the ar-
rows at A and B.

A modification of the above methods for forming the
fillets and flutes is effected as follows : — ^Fill in the spaces
on the shaft between the collars in this method — or the
rims in the former method — and rule them off with a
main diminished floating rule as already described and
when the stuff is firm but not set, the positions and forms
of the fillets and flutes are set out on the floated surface,
then the flutes are cut out by hand by means of gouges
and drags, and afterwards fined as already described.
This system is specially useful for small columns.

For extra high columns it will be found difficult to
work a floating rule to form the whole height of the
column in one operation, in fact, for some columns to be
seen in cities, which are 20 feet to 30 feet high, and
even higher, it would be impossible to form them with
one fioating rule. It is therefore necessary to divide the
column into two or more sections, and cut the floating
rules accordingly. In this case two or more plaster col-
lars about 3 inches wide, and made to the exact circum-
ference of the column at the point of division, are re-
quired. These collars are then temporarily fixed in posi-
tion to act as screeds, and after the whole surface of the
column is filled in and ruled off, the collars are cut out
and the spaces filled in, and then the whole surface
fined in one operation. Three or even more floats, as
already described, are required for the fining of high or
massive columns.

200 CEMENTS AND ^CONCRETES

Having now briefly reviewed the more or less useful
methods, and described some of the most useful and
practical methods, the conclusion to be drawn is, that
diminidied fluted columns are best done by working
them by hand, with the aid of diminished floating rules
and cast or run beai'ings. This first or rim method will
be found useful for many purposes; but the collar meth-
od, with the addition of intermediate collars for extra
high columns, is the best for general use.

Diminished Fluted Pildsters. — Pilasters are said to be
a Eoman invention. They bear an analogy to columns
in their parts, have the same names and standard of
measurements, and are diminished and fluted on the same
principals. When pilasters are placed behind columns,
and very near them, they should not project above one-
eighth of their diameter; but if they are from 6 to 10
feet behind the column, as in large porticoes and per-
istyles, they should project at least one-sixth of their
diameter. When they are in a line with columns, their
projection should be regulated by that of the columns.
When pilasters are used alone as principals in composi-
tion, they should be made to project one-fourth of their
diameter to give regularity to the returned parts of the
capitals. The process for forming pilasters is the same
as for columns.

Panelled Coves. — ^Large coves, segmental or elliptical
on section, having their surfaces panelled with mouldings
which spring from the back or above a wall or main
cornice, and finish at or intersect with a beam or other
moulding at the top or crown of the cove, require to be
carefully set out and screeded. The floating is done
from two horizontal screeds made at the top and bottom
of the cove, and from these vertical screeds are formed,
and then the intermediate spaces or bays are filled in

METHODS OP WORK

201

and ruled off with a floating rule bearing on the vertical
screeds. The horizontal screeds are easily made, but the
vertical ones require special care to insure all being uni-
form in section. These screeds are formed with a tem-
plate cut to the desired section, and about 2 inches thick.
For lai^e coves they are made with three or more pieces
of wood. The most correct and expeditious way of
forming circular screeds is by the ** pressed screed"
process.

Section of Covb Showing Pressed Screed I'rocess.

NO. 13.

Pressed screeds are simple and expeditious in con-
struction. They form accurate grounds for floating pur-
poses and for running mouldings on circular surfaces.
The method of forming pressed screeds and floating coves
is shown in the accompanying illustration No. 13. This
shows the section of a cove with the main or wall cornice
and the crown moulding. F is a nib rule used .when

20a CEMENTS AND CONCRETES

running the main cornice. To float this cove for the run-
ning of vertical mouldings, first form the top and bottom
horizontal screeds (A and B), then form the pressed
screed. This ia effected by temporarily fixing the
template, G, or by one man holding it on the bottom
screed, and another man holding it on the top screed,
while a third spreads and presses the gauged coarse stuff
until the space between the' first coating and edge of the
template is fiUed up, then drawing the trowel down each
side of the template clears off any superfluous stuff.

-Fic. I. Float:no Coves. Fic. i. Levelling Roul
NO. 11.

The template, .which has been previously oiled, is then
removed, leaving a narrow, but true and smooth screed
ready for working on. This method gives a truer
screed, especially in elliptical or long circular screeds,
than floating or working with a template, because if the
template is not worked perfectly vertical, the curve of
the screed is altered and not true.

The subjoined illustration (No. 14} elucidates the
methcd of forming the screeds for floating cove surfaces,
also for floating segmental, elliptical, or any other foma

METHODS OF WORK 203

of interior and exterior angles in coves. Fig. 1 shows a
plan of the cove. The letters in this sketch correspond
with those on the same parts in the section on illustration
No. 13. The first coating and the various bays, after
the screeds are made, are indicated by crossed diagonal
lines at the D's. The top screed, A, should be levelled
from end to end and made parallel in depth with the
crown moulding. Their levelness is tested with the aid
of a ''levelling'' rule. The bottom screed, B, should
be made parallel with the main cornice, so that the pro-
jection of the vertical mouldings will be uniform. The
vertical screeds, C, are next formed, making the first two
near the internal angles, then two at the external angles.
The intervening space is now set out, so that the screeds
may be 8 to 10 feet apart. The screeds may be formed
farther apart according to requirements. If there are
vertical mouldings to be run in the cove, the screeds
should be made at the sides of the proposed mouldings.
It is always best to have two or three screeds near the
angles, so as to give a bearing for the floating rule, R.
This shows the position of the rule when floating the in-
ternal angle. The external angles on the other side are
formed in the same way. The distance between the
' screeds used for floating the angles can be regulated ac-
cording to the depth or form of the angle. It will be
understood that the floating rule must be sufficiently
long to bear on two vertical screeds, and reach to the
extreme point of the angle. The floating rule, R, here
shown is termed a grooved floating rule. This is grooved
on both sides, as shown by the section, S.

Fig. 2 shows the elevation of a levelling rule as used
for levelling dots for ceiling, beam, or crown screeds.
This is similar to an ordinary parallel rule, but with the
addition of a fillet, F, nailed flush with the bottom edge

204 CEMENTS AND CONCRETES

to form a ledge to cany the spirit level, L. The level-'
ling rule is applied on the dots to test if they are level ;
this is proved by inspecting the spirit-level ; if one dot is
too fuU it must be depressed until the levelling rule is
level.

Diminished Mouldings, — Mouldings that diminish in
depth or projection as well as in width (termed '* double
diminished mouldings") are not so common as those that
diminish in width only. The diminish in width is simple,
and is obtained by the aid of a ** triple-slippered" run-
ning mould and two running rules fixed to form a
diminished space, as described hereafter. The formation
of a regular and pleasing diminish in depth greatly de-
pends on the profile of the moulding. A moulding hav-
ing small members, especially at the sides, is more diffi-
cult to diminish than one having large members, es-
pecially one with plain and deep fillets at the sides.
Three methods are here given for running double dimin-
ished mouldings on domes, cupolas, or vaulted ceilings,
or en lower surfaces. These methods give good results,
especially if a little thought for the requirements of the
case is bestowed on the designing of the moulding.

Double Diminished Moiddings, False Screed Method —
By this method the diminish in depth is obtained by false
screeds, and the diminish in width by the aid of a dimin-
ished rule, which is fixed on the centre of the profile or
bed of enrichment. This method is elucidated in the fol-
lowing illustrations. The annexed illustration No. 15,
shows the section of a vertical moulding on the plaster
or floated surface of the inside of a dome. C is the
main cornice from which the inner line of the dome
springs. The D's are dots which are used to regulate
the -diminish of the false screeds. The various thickness-
es and positions of the dots are obtained by setting out

METHODS OF WORK 200

the full aize of the section on a floor or worked out to a
scale. If the section is elliptical, dots should be placed
at the points where the transition of curves takes place.
When the surface of the dome has been floated, the
diminishing dots, D, are placed aWeach side of the in-
tended moulding and at their proper posdtions, be^a-

Section 'Double DtMiNisHi^n MooLniKCS—
False Screed Method.

ning above the main cornice, C, and going upwards in
rotation but having no dot at the top. The spaces be-
tween the dots are next filled and ruled in, bearing on
the various dots with the cui'ved rules or templates.
When ruling the top bay of the screed, the top entJ cT
the rule bears on the origifaal floating at the top or ex-

CEMENTS AND CONCRETEa
F.3.2 Fiii

Elevation Double Dimi-
MSHF.u Mouldings — False Screed*
Method,

METHODS OF WORK. 207

treme point, this point being the true thickness of the
screed.

Illustration No. 16 shows the plan and elevation of the
work. Pig. 1 shows it in progress, and Fig. 2 when
finished. The A's on plan and elevation (Fig. 1) are
false screeds, the B's are brackets, while C C indicates
the diminished running rule. This rule is made as fol-
lows:— ^First plane one face of a pine board about V^
inch thick, and of sufficient length and width for the
desired purpose. On this make a centre line from end
to end. From this centre line set off the width at one
end, and the diminished width at the other end; then
extend the diminished width lines from end to end, and
then plane the running edges to the diminished lines. In
order to allow the rule to bend freely to the curved
surface, make a series of saw-cuts crossways on the back
or bed face. The false screeds are made as already de-
scribed. A centre screed for the running rule is made
by the aid of a template. This is made with two slippers,
one on each side, similar to a running mould, so as to run
on the false screeds, the centre or cutting edge of the
template being made to the depth of the proposed screed.
The face surface of the bracket is then laid with gauged
stuff and finished off by working the template up and
down. This done, fix the diminished rule, C, on the
centre of the screed. The running mould, E, on the
plan is made with the slippers, one to bear on the centre
screed and against the running rule, and the other to
bear on the side false sereed. The slippers are made
circular on their running edges, so as to fit the circular
screeds. A short slipper at the nib gives more freedom
and ease when running the moulding, and the mould is
not so liable to cut up the screeds. After the moulding
i& run on both sides, take the running rule off, then cut

208 CEMENTS AND CONCRETES

the false screeds down to the floating, and make the sides
of the fillet good, and then fix the enrichment. FifT 2
shows the plan and elevation of the finished moulding
and enrichment. A, on the plan, shows one side of the
moulding before the false screed is cut off, and G shows
the screed cut off and the member made good to the
floating. The amount of diminish from the bottom to
the top of the moulding is shown at the brax^kets B and
B, and by the profiles of the cornice on the plan and ele-
vation. The bed and section of the enrichment is shown
at F on the plan. As this enrichment is diminished (in
width and projection) the whole length must be
modelled.

Running Double Diminished Mouldings, Diminished
Rule Methods — This is a method which is introduced,
and is somewhat similar to the first method described. It
is well adapted for running mouldings, having no en-
richment on the centre of the section, the bed of which
may be used as a screed and bed for a running rule, as
used for the first method. By this method the whole
moulding is run in one operation. The diminish in
depth is obtained by the use of two running rules
diminished on the face, or in other words, diminished
in thicknesa The diminish in the thickness of the
rules is obtained by setting the full size, as described for
the false screeds in the first method. A series of saw-
cuts must be made on the backs of the rules to allow them
to bend to the circular surface of the dome. These
rules act in a similar way to the false screed used in the
first method, with the addition that they form the fillets
of the outside members, thus avoiding cutting the screeds
down and making good the fillets. They are also used for
obtaining the diminish in width. This is effected by
first making a central line on the bed surface of the

METHODS OF WORK 209

proposed moulding; then from this line, at each side, set
out the half width of the moulding, including the beax-
ing parts of the running mould. This is done at the
widest or bottom end of the moulding, and at the nar*
rowest or top end. Then from these width marks, lines
are extended from end to end. On these lines, nails are
inserted from 2 to 3 feet apart, which act as guides for
fixing the running rules. The inner sides of the rule are
placed against the outer sides of the nails and fixed, and
then the guide nails are extracted, thus forming the
diminished space and bearings. A triple-hinged mould
with a slipper at each side is used, so that it wiU close up
while being run up the diminished space. The stock is
rebated, so that it will run on the tops and inner sides
of the rules. The mould plate must be cut to fit the
section at the greatest width of the moulding, but care
must be taken that the depth at the outer members is
the same as proposed for the top. The ends of the inner
slippers and the adjoining parts of the stock are cut
so as to leave an open space, to allow both parts to work
freely when the mould assumes a raking position, as
shown on illustration No. 17.

The extra depth of the square of the outside members
is formed by the running rules. It may here be re-
marked that the thickness of the rules at the top should
be made about % inch thicker than the depth of the
square part of the outside members. For example, if
the depth of the fiUets or square part of the outside
members is i inch, the rules should be 1^ inches thick
at the top. This allows for the requisite bearing for the
running mould. The ends of the stock that bear on the
inside of the rules must be rounded oflE to allow the
mould to run freely when it closes up while being run
UD between the diminished space.

CEMENTS AND CONCRETES

The various parts of the running mould are shown in
the annexed illustration No. 17. Fig. 1 shows the mould

Elevations and Section or Ruhnino Mould

AND RiiLEii Foa DouBi,E_Di_MiNSHBi) Mouldings^

Diminished Rule Method,

NO. 17.

in position at the bottom or widest part of the moulding;

B, E, are sections of the running rules; S, S, the slip-

METHODS OF WORK

pers; and H, H, the hinges which connect the two
halves of the stock to the slippers. The hinge whick
connects the mould in the centre is fixed on the other
rsdde of the stock. Its position is indicated by dotted
lines. Fig. 2 shows the form of the mould when at the
top of the moulding. The letters correspond with those
on Fig. 1. The thin seams at the centre and sides of the
moulding which are caused by the joint of the mould in
the centre and by the joint of the mould and the rules
are cleaned off by hand. This method, like the first, has
the defect that the actual diminish or the whole depth of
diminish lies in the fillets of the outside members of the
moulding. The difference between the diminished mem-
bers and the regular members will be most noticeable on
the adjoining members, the vertical fillets of the cavettos.
If this defect should prove offensive to the eye, it may to
some extent be remedied by working these members down
by hand, with the aid of planes, gouges, drags, and joint
rules, after the moulding is run, so as to reduce the depth
of the fillets, and throw the difference into the cavettos.
A line should be set out to the desired diminish on the
fillets to act as guides when working the cavettos down.

Running Double Diminished Mouldings, Top Rule
Method. — Running double diminished mouldings by the
aid of a **top rule" is another method that I have intro-
duced for this purpose. The diminish in width is ob-
tained by fixing two slipper running rules to the de-
sired diminish and a triple-hinged mould ajs previously
described, and as shown at Figs. 1 and 2 on the an-
nexed illustration, No. 18. Fig. 1 shows the running
mould, M, and the slipper rules, R, R, at the full-sized
or springing end of the moulding, and Fig. 2 shows the
running mould and rules at the diminished end. The
diminishing depth is obtained by the aid of a **top rule*'

212 CEMENTS AND CONCRETES

which is fixed on two blocks, one at each end of the
moulding, as shown at Fig. 3, This shows the elevation

rig 6.

Fig 5.

Elevations, Plan, ani> Sections op
■RONNiNC Mould and Rules FOR Diminished
Mouldings— Top-Rule Method.

NO. 18.

of one side of the running moulds at the springing and
iliminiahed ends of the moulding, also the running rales.

METHODS OF WORK 213

B is the section of the fixing block at the springing end
of the moulding, and D is the fixiiig block at the dimin-
ished end, upon which the top rule, T, is fixed. This
rule is fixed on the slant, to suit the desired diminish.
It must be made sufiiciently wide to allow a bearing for
a part of each half of the stock, M, M, of the running
mould, and also fixed over the joints of the mould, as
shown at T, Figs. 1, 2, and 3. The top rule being fixed
on the slant, causes the running mould to gradually cant
over when it is drawn from its upright position at the
springing end of the moulding to the diminished end,
as shown at Fig. 3, thus forming the diminish in the
depth of the moulding. M a shows the end section of
the stock in an upright position when at the springing
end, and M is the section of the stock in a slanting posi-
tion when at the diminished ends of the moulding. The
dotted lines in both indicate the parts of the stocks in-
side the slippers, and the angular dotted line at H, H,
indicates the splayed or cut side of the hinge. S S is
the outer elevation of one slipper when at each end of
the moulding, and R is the slipper running rule. It
will be seen that the running mould at Fig. 1 is some-
^ what similar to the triple-hinged running moulds pre-
viously described. But there are two important excep-
tions, namely, the hinges at the centre and the two sides
of the mould.

The side hinges for this mould must be cut on one side
and the angles rounded off, leaving only one screw-hole,
so as to cause less friction, and allow this part of the
hinge to turn on a screw when fixed on the slipper. The
use of this will be seen hereafter. An elevation of a
binge, before and after it is cut, is shown at Fig. 4. The
lower hole on the cut half of the hinge is used, because
tiie nearer the '* turning points'' or pivots are to the

214 CEMENTS AND CONCRETES

running ground or screed, as the case may be, the less
will the bearing edges of the running mould rise when
the mould cants over. For instance, if the *' turning
points'' were made at the centre of the depth of the
mould, the bearing edge of the mould would rise from
the ground in proportion to the cant of the stock. This
would increase the depth of the lower members (those
below the pivots or turning points), instead of dimin-
ishing them. This hole must be enlarged so as to admit
of a short thick screw to give the necessary strength. It
will be understood that this part of the hinge works on
the plain part at the head of the screw.

Having cut the right and left hinges, they are screwed
on to the stock and the slippers of the running mould,
keeping the half of the hinge with the three screw-holes
on the st<5ck, and the cut part with one screw-hole on
the slippers, as shown at H, H, Fig. 1. It will also be
noticed that these hinges are fixed at the lower edge of
the mould. This is done so as to allow the stock of the
mould to cant from its base for the reason already men-
tioned. When screwing the cut side of the plate to the
slipper, allow just sufficient play for the hinge to turn
smoothly but firmly on the screw. The centre hinge con-
necting the halves of the stock, M, M, is formed with two
pieces of metal plate. The inner ends are rounded off
to allow them to turn and a circular orifice one-third the
width of the plate is drilled at the circular ends, and
then three or more screw-holes for fixing purposes are
drilled on the other ends. The two plates are fastened
together with a flat metal ring or with stout copper wire.
The thickness of this ring is regulated according to the
size of the orifice, but allowing just sufficient play for
the plates to turn both ways when the mould assumes a
slanting and an angular position, as shown at Fig. 2.

METHODS OF WORK 215

An enlarged view of the centre hinge is shown at Fig. 5.
The -centre hinge is screwed oh the inner side or profile
of the stock, as shown at C, Fig. 1. An enlarged view
of part of the stock at the joint, when inverted for fix-
ing the centre hinge, is shown at Fig. 6. The top and
bottc^m edges and the ends of the stock must be rounded
off, to allow it to cant over easily. The diminish of this
moulding, both in depth and width, as shown in the illus-
tration, is a little more than may generally occur in prac-
tice, but this is given to show the various parts more
clearly, also what to avoid in the amount of diminish
when using this method.

The diminishing depth here shown is about two-fifths,
and the diminishing width about one-third. The dimin-
ishing. depth, by this method, should not be overdone,
because the running mould assumes an angular position
both on plan and section, therefore it forms the vertical
parts of the ipembers in a slaniting line and the horizon-
tal parts out of a level. These defects become more pro-
nounced at the diminished end of the moulding, as
shown at Fig. 2. The top member can easily be made
level and fair by hand, but it would entail too much
labor to rectify the defects of the other members, there-
fore this method should only be used for small mould-
ings or where the diminish in depth is of a slight nature.
The se^m at the top member, caused by the joint of the
mould, is cleaned off and made good by hand.

Cupola Panels and Mouldings. — In order to facilitate
the setting out and formation of cupola panels and
mouldings, the method of drawing them is given. This
wiU be found very useful in the general setting out and
construction of cupolas, whether in ** solid" or in
** fibrous plaster." Various parts of cupolas and soflfita
of arches (from designs by J. Gibbs, architect, a pupil

216 CEMENTS AND CONCRETES

of Wren, and a great patron of the plasterer's art), with
the method of drawing same, are illustrated on plate 11.
To draw an octagonal cupola, as shown by the plan at
Pig. 1, take A B (the width of one side of the octagon)
as the base line. From the centre of this erect the per-
pendicular line D C, then draw the lines C A and C B ;
this will give the triangle ABC, forming the plan of
an eighth part of the cupola. The profile (Pig. 2) is
made by the quadrant of circle (A B. C) directly over
the plan. Divide half the base line, A B on plan, into
seven parts, as here figured, and six of them will make
two panels; the seventh will remain for the border. The
same divisions must be marked on the profile over the
line A B, as follows: — Take for the border at the bot-
tom four parts, as shown in the plan ; place them on the
profile from the base line to No. 1, and draw a line par-
allel to the base line of the plan; measure the length of
the two central lines marked 2 2, and place it in the
profile for the second panel. Prom thence draw another
parallel line, and measure the length of the two central
lines at 3 3 in the plan to find the square height of the
third panel, and so on to No. 8, as shown in the plan
and profile.

The elevation or upright side of this octagonal cupola
(Pig. 3) is made by the following geometrical rule.
Pirst draw the base line (A B) on plan even with the
base line (A B) of the profile; on this erect the perpen-
dicular line (DC) for the centre of the side; then draw
all the parallel lines as shown by G G, etc. Take half
the length of each line, figured in the plan, and mark it
on each side of the middle line of Pig. 3 until the length
of every panel is fixed. Prom these lines and points the
forms or outlines of the panels are taken. The inner
divisions are brought over to the number of panels con-

METHODS OF WOEK 217

tained therein in the same manner as they appear in
Fig. 3. The same rule is used for setting the side shown
at Fig. 4.

With regards* to the soffits of arches, if they are
divided into panels, they must be of any uneven number,
as shown at K and L, by having a panel in the centre.
The border must not be more than one-sixth nor less
than one-seventh part of the whole breadth. The quad-
rant or profile, E F (Fig. 2), on which the panels of this
semi-circular soffit are divided, will be sufficient to ex-
plain them. A circular soffit of lesser breadth is shown
at M, and one of greater breadth is shown at.N. Sec-
tions of each soffit are shown at the top of the eleva-
tions.

The method of constructing the plaster work of cupo-
las depends to some extent on the design and size of the
panels and mouldings. For example, if the diagonal
panels shown in Fig. 3 were sufficiently large to admit
of a running mould to run a piece of moulding (on each
side of the panels) not less in length than the mitres at
each end, the best method would be to run the four sides
of all^the panels; but if the panels were too small to
allow a running mould to run the requisite amount of
moulding, it would be necessary to run a part, and cast,
or run down, and plant the other parts. In some designs
it would be necessary to plant all the mouldings. In
some cases the panel mouldings, from the base up to a
third or fourth of the height of the cupola, can be con-
veniently run; but the panels above this which become
smaller, and are too small to admit of their being run
with economy, should be planted. Another method is
to run all the diagonal mouldings that spring from left
to right, as from A to a, in one length from Border to

218 CEMENTS AND CONCRETES

border, and then run the intermediate parts of th^
mouldings springing from right to left.

The intermediate parts may also be run down, or cast,
and then planted. By this method the intermediate
parts only require mitring, and if they are planted the
intersections only require to be stopped. If these parts
are run, the brackets from right to left must be cut
down at the intersections to allow the running mould to
pass when running the mouldings from left to right in
one length. Whichever method is employed, the surface
must be floated true to the various curves to form a
ground for the mouldings, whether run or slanted. The
surface should also be floated sufficiently smooth to act
as screeds without using gauged putty screeds for each
moulding. This is done as described for panelled ceil-
ings. The groundwork of the floating is effected by first
forming a screed on the base border (A B), and one on
the top border (at C), and then from these screeds as
bearings, form two screeds on the side or vertical bor-
ders, thus completing the main screeds, and from which
the panel surface is floated. Owing to the brackets and
the form of the panels, it is a somewhat difficult opera-
tion to float all the panel surfaces with a uniform depth
and curve. It will be seen that a floating rule (cut or
so constructed to clear the brackets), whether worked
vertically or horizontally, cannot travel into the angles,
and float the whole surface. This difficulty is overcome
by making dots in each angle, or making narrow screeds
from angle to angle of each panel. The horizontal dots
or screeds, as the case may be, are ruled off wit^^ a gauge
rule, which is cut to the required depth, and to bear on
the side screeds. The vertical screeds are ruled off with
the circular rule, on which pieces of board cut to the
desired depth and length of the various panels have been

METHODS OF WORK 219

previously fixed. The intervening spaces are then ruled
off with short rules cut to the angular curves.

Another and better way is to cut an angular floating
rule to fit the curve from A to a, and float all the panel
surfaces in a line from border to border in one opera-
tion. This angular rule is set out in a similar way as
described for angle brackets. The rules for this or the
first method must be made to suit the longest line or
set of panels. After each set of corresponding panels
in the other sides of the cupola is floated, they must be
shortened to fit the next set of panels, and so on, until
all the panels are floated. The mouldings being dimin-
ished in width, are run from a diminished running rule
fixed on a centre screed in the same way as described for
diminished dome mouldings. The screed for this method
is formed by an angular floating rule cut to the angular
curve, as already mentioned. For some designs the
moulding may be run with a twin-slippered running
mould. This form of mould can also be used for form-
ing about one inch of the panel surface. This acts as
a ground for floating the. panel surfaces. When large
paterae are uaed, the ground panel surface may be cast
with them, thus avoiding floating and setting. The oc-
tagonal panels shown in Fig. 4 are formed in a similar
way to Fig. 1. After the vertical and horizontal mould-
ings are run, the diagonal sides of the octagons are
planted. Where square panels form the design, the
mouldings can be run with a radius-rod running mould
from a centre pin and block. - The sections of the soffits
of the arches are run with a radius-rod running mould,
fixed on a radius board, and the cross styles or mould-
ings, as shown at K and L, are planted. A small portion
of the arch should be run to form a ground on which the

220 CEMENTS AND CONCRETES

enrichments may be modelled. Fibrous plaster is "weU
adapted for constructing the plaster lining of cupolas.

Panelled Beams. — ^When panelled beams have mould-
ings on the lower part of their sides or faces, and on the
soffit to form a sunk panel, they may be run in two parts.
Screeds are formed on the two sides, and one in the
centre of the soffit. If the mouldings on the sides have
more girth or are larger than the portion on the soffit,
they may be run from rules fixed on the side of the beam,
with the nib bearing on- the style or on the soffits. If
the style and mouldings on the soffit are small, the mould
is made to run the face, style, and soffit moulding in one.
If the styles are broad, the moulding on the sunk part
of the soffit is run from a parallel running rule fixed in
the centre of the soffit, thus forming a double rule to run
each side of the sunk moulding. The latter way is most
generally used. The end or other mouldings required
for panelling the soffit are run down and planted.

All beams of any length should always have a camber,
not only to allow for any settlement that may take place,
but to make it more pleasing to the eye. A beam dead
level and straight has the appearance of sagging in the
centre. This may be termed an optical illusion.

Trammels foi^ Ellipiical Mouldings. — It may at once
be pointed out that an ellipse and an oval are not the
same. Both ends of an ellipse are similar, and an oval
is egg-shaped, one end having a greater curve than the
other, therefore the term oval moulding or panel is
scarcely correct when applied to the following illustrar
tions. This term, however, is beist known and generally
used by most workmen in the building trades. The term
** elliptical ' ' is generally applied by plasterers when re-
ferring to mouldings where the whole ellipse is not car-
ried round, such as for mouldings or elliptiqal arches,

METHODS OF WOKK

221

windows, etc.; and the term "oval," where the whole
figare is completed, such as panels (elliptical on plan)
formed on walls or ceilings. In consideration of the
common usage of these terms, they will here be used in
describing the setting out or working of same.

Trammels are often used for running oval panel
mouldings, and for forming the lines when setting out
oval templates. Trammels are made of wood or metal.
A simple way to make a tram-
mel for small work is to sink
two grooves at right angles in
a hardwood board (terraed the
plate), about 7 inches long,
6 inches wide, and 1 inch
thick. The grooves are about
1-2 inch deep and 1-2 inch
wide. Two hardwood pins are
then made to St the grooves.
They have collars to bear on
the surface of the plate. The
upper part is made round to
£t the centre holes of the rod.
The subjoined illustration No.
Id shows a template and
various sorts of template pins.
Fig. 1 is a view of a template,
with the two pins, rod, with the
running mould attached in

position, and a part of a moulding. Fig. 2 shows various sec
tions of pins. A is the section of the pin as used in Fig. 1,
and C is the plan of the pin at the intersection of the
grooves. B is the section of a dovetailed pin used fop
another form of trammel. The rod is made to any d&-
sired length, so 4:hat it may serve for various sized ovals.

tTkAMMEL!!.
NO. 19. ■

222 CEMENTS AND CONCEETES

The average size for this kind of trammel is about 1 foot
6 inches long, 1 inch wide, and 1-4 inch thick. A series
of holes 1-4 inch in diameter (to fit the head of the pin)
is made about 1-8 inch apart on the flat side. The first
bole is made near one end of the rod, and continued
down the centre for about 15 inches, leaving the blank
space for screwing on to the running mould. A pin is
now laid into each groove, and the size of the desired
oval is obtained by regulating the length of the rod at
each diameter by means of the holes. The pin in the
short groove is the point from which the length of the
oval is taken, and the pin in the long groove for the
width. The trammel is fixed on the running board by
means of two or more screws, as shown. This size of
trammel -can only be used for oval mouldings from about
10 inches to 36 inches at their longest diameter, there-
fore larger sizes are required for larger ovals.

A trammel for running large ovals (say from 6 to 10
feet at the major diameter), if made solid, as shown in
Fig. 1, would be too heavy and cumbersome for fixing
on ceilings where the mouldings are run in situ. A
lighter kind termed a "cross'' template, is made as fol-
lows:— Cut three flooring boards, one a little less in
length than the longest diameter of the proposed oval,
and two less than the short diameter. Lay them down
on a floor in the form of a cross (similar to the grooves
in Fig. 1), and fix and brace them together. Four angu-
lar braces will hold them together, and allow the whole
to be fixed on the ceiling. On the centre of this 'ground
make two lines at right angles to each other, and from
these set out the width of the desired grooves at the ends
and intersections, and then fix wood fillets, each about
one inch thick and two inches wide, to the marks, thus
forming the grooves. In order. to prevent the pins drop-

METHODS OF WORK 223

ping out of the grooves when the trammel is fixed face
downward on the ceiling, the inner sides of the fillets
should be splayed so as to receive dovetailed pins, as
shown at B, Fig. 2. This may also be effected by fixing
running rules on the fillets so as to overlap about 1-4
inch, over the groove space, thus forming rebated or
square grooves. The pins are made with shoulders to
fit the grooves. In both modes a 1-inch pin must be in-
serted in the trammel pin to prevent the rod dropping.

A strong, accurate, and permanent trammel can be
constructed entirely with metal. To make this, procure
a sufficient length of metal tube, about 1-2 inch in diam-
eter, having a slot about 1-8 inch wide, cut longitudi-
nally. Out the tube into four piecefe, mitring the inter-
sections, and fix and brace them together in the form of
a cross, as already mentioned. A pin made to fit the slot,
fixed in a ball made to fit the tube, completes one of the
sliding pins. The rod may be made of metal or wood,
but the latter gives more freedom for changing the size
for different sized ovals.

Various methods are employed for running oval panel
mouldings on ceilings. The most useful are by means of
trammels, or wood or plaster templates. A trammel is
a good instrument for running oval panels where the
mouldings are not wide. Wide mouldings (say over 1
foot) cannot be run true or uniform in width in one
operation with a trammel, because the running mould,
which is fixed on the end of the rod of the trammel,
assimies a raking position when it is between the right
angle points of the major and minor diameters of the
oval. This raking position takes place at the four joints
or change of ounces of the oval, and is more pronounced
in extra wide mouldings. This difficulty is overcome by
running the mouldings in two parts, using a trammel

224 CEMENTS AND CONCRETES

mould for running the first or inner part, and a run-
ning mould (horsed to run on the run part) for running
the second or outer part. This is effected by dividing
the section of the moulding into two parts, taking care
to make the joint at the side of a fillet or in the center
of a flat member at the outer side of ^he part to be run
with the trammel mould, so as to allow for a ^ood bear-
ing (wide and strong) for the slipper of the running
mould used for running the second part. The running
mould for the first part is fixed on the rod of the tram-
mel as already mentioned. The running mould for the
second part is horsed with a circular slipper cut to fit
the curve of the first moulding. If the oval has quick
curves, a slipper with two pins will give the best re-
sults.

If there is an enrichment in or near the center of the
moulding, run the moulding in three parts, using the
bed of the enrichment (which is run with a trammel
mould) as a center running rule for running the outer
and inner parts, which are run with circular or pin-
slippered running moulds, as already described. It will
be seen that by using either of these three methods, wide
mouldings for oval panels can be run iinif orm on width ;
the trammel mould giving the form of the oval to the
first part of the moulding, or to the center running rule,
and the curved slippered running moulds giving the de-
sired uniformity of width to the full section of the
moulding. Most forms of oval panel mouldings are best
run with templates. When run with trammels, or with
radius-rods, the running mould is apt to jump and cause
cripples at the junction of the major and minor diam-
eters.

Templates for Running Elliptical Mouldings, — The
true form of an ellipsis can only be derived from the

METHODS OF WORK 225

diagonal cut from the cone or the cylinder, and the near-
est approximation to this curve must be obtained by
continuous motion. There is no other instrument so
well adapted for effecting this purpose as a trammel.
For a true eUipas, ma^e the distance from the outer end
of the rod to the nearest point or centre pin equal to

Tehflats and Pin-Mouij> for Running
Ellipticat. Arch Mouldings

NO. 20.

half the shortest or minor diameter of the ellipsis, and
from the centre pin to the outer pin equal to half the
longest or major diameter. This shows the use of a
trammel for setting out the lines to make a template for
this form of ellipsis.

The subjoined illustration No. 20 elucidates the method
of setting out another form of ellipsis; also an oval hav-

226 CEMENTS AND CONCEETES

ing its major axis one-third greater than its minor. This,
also shows the template and a pin running mould in posi-
tion for running an elliptical arch moulding. The
template (Fig. 1) is made to extend below the springing
line of the arch, so as to allow the mould to be run down
to the spring of arch and save mitring. The template
for running the arch extends to the shaded part; but
to utilize the space the curve has been continued round
to show a method of setting out a template from which
an oval moulding can be run, the oval having its major
axis one-third greater than its minor. The method of
setting out is as follows: First draw the line AB, the
greater diameter, to the desired length; th^n bisect it,
and erect the perpendicular line CD; this being the
lesser diameter, is made a third less than the line AB.
Then bisect each half of the line, which will divide the
line AB into four equal parts and give the centres E, E,
which are the centres for describing the ends, as from
F to F, and Fl to F2. Then from the centres C and D
describe the flat curves from F to Fl, and from F to P2,
which complete the oval. It is, however, better to set
out this template by the trammel, as the junction of the
segments of the circles always has a more or less crip-
pled look.

Fig. 2 shows a ''pin-mould'' in position when run-
ning an elliptical arch moulding. This mould is pro-
vided with two hardwood pins inserted into the bearing
face of the slipper. The pins bear on the edge of the
template, and owing to their position, and being apart,
allow the mould to take any change of curve without
** jumping."

Before running elliptical mouldings on arches or win-
dows, the centres and running rods should be tested, so
that the mouldings will intersect accurately, and so avoid

METHODS OF WORK 227

jumps at the change of curves. All centre pins should
be level with each other, and equidistant from the centre
of the arch or window. The outline and intersections of
the proposed moulding can be tested by temporarily fix-
ing a pencil on the outer aud inner profiles of the run-
ning mould, then working the mould over the screeds,
so that the pencils will form two lines. I have heard of
a three-centered elliptical hood moulding being run over
a window with what is called a **bolt radius-rod.'' This
rod is made in two parts and connected with a hinge,
and held straight when running the long diameter with
a bolt and sockets where fixed at the joint. The run-
ning mould is fixed on one end, and a centre plate on
the other in the usual way. The long diameter of the
moulding is run first, and when the radius-rod reaches
the change of curve the bolt is drawn back, and the short
diameter of the moulding run with the short part of the
radius-rod. A nail is inserted in a board which is pre-
viously fixed in the window opening. The nail must be
fixed in a line with the change of curve so as to stop
the radius-rod, and hold the long part in position while
the short part is working. The same operation is re-
peated for the other side of the work. It is needless to
say that this method is far too complicated to be serv-
iceable for general purposes.

Templates are used for running most forms of ellip-
tical panel mouldings. Plasterers may make their own
templates or running rules by using fibrous plaster casts
as a substitute for wood. This is effected by first set-
ting out a quarter of the proposed oval panel, then cut
out or run a temporary plaster running rule to fit the
inner line, allowing a space for the slipper of a running
^nould. Cut a reverse running mould to the section of
the proposed fibrous plaster rules (say about 1 inch thick

228 CEMENTS AND CONCRETES

and 3 inches wide), then run the quarter length of the
oval, and after making true joints at the ends, cast four
fibrous plaster quarters, and then lay and fix them re-
versely, thus completing the full oval template or run-
ning rule. The full oval running rule can also be run
in situ and in one operation. This may be done with
a trammel or with radius-rods, according to the form
and size of the panel. Strong and stiff gauged plaster
or a strong white cement, should be used for the run-
ning rule, to enable it to resist the friction of the run-
ning mould while running the moulding. Radius-rods
are more often used for setting out the lines for oval tem-
plates than for running the mouldings. Circular mould-
ings— vertical, horizontal, or angular — run off circulajr
grounds require special running rules, so that they will
take or bend to the double curvature. For this purpose,
cane, flexible metal pipes, and wooden rules, having series
of saw-cuts on the backs and sides, have been used, but
cast fibrous plaster rules or a jack template are more
suitable for most of these purposes. Template can also
be made by means of a plasterer's oval.

plasterer's Oval, — The subjoined illustration (No. 21)
elucidates the setting out of this form of oval to any
given size, also the method of forming two oval momld-
ings from two circle mouldings. The ovals are formed
by running two circular mouldings in plaster, the diam-
eter of one being exactly double that of the other. Each
circle is cut into four quadrants or quarters. Two of the
quadrants of the larger circle form the sides of one oval,
and two quadrants of the smaller circle form the ends,
the^ four segments making a fairly good oval. The re-
maining segments constitute another oval of similar size
and shape. The method is simple and speedy, and it
can also be emptoyed for the formation of elliptical

METHODS OF WORK

230 CEMENTS AND CONCRETES

mouldings on arches, doors, or windows as well as for
oval panel mouldings. The formation of ovals by this
method has been employed by plasterers for genera-
tions, but owing to the want of a definite rule for set-
ting out this fprm of oval to any given size, its use has
been somewhat limited. To meet this want, I have in-
vented a method which can be adopted for most pur-
poses, and which I give here for the first time. For
want of a better name we have called this a ** Plasterer's
Oval,'' for the reasoi^ that plaster lends itself more read-
ily than any other material to the formation of circular
mouldings. No one in the building trades can form a
circle or an oval moulding so quickly and accurately as
a plasterer. The method of setting out and of con-'
structing this form of oval is as follows : To set out an
oval to a given size, the greater diameter being given.
Take this greater diameter as a base to determine the
required diameters of the large and small circle mould-
ings, M and N, Fi^. 2. Let the line A B, Fig. 1, be the
given diameter, say 3 feet; on this form two squares,
each according to their diameter would be 1 foot 6 inches
by 1 foot 6 inches, as shown at C D E F and F G H C; J
then draw diagonals in each square as at G E and D P
and G .6 and F H and at their intersections 1 and 1 as
centres draw the circles 1 K and 1 K. The radius in this
example would be 9 inches. The quadrants M and M 1
correspond with the same letters in Figs. 2 and 3, and
they form the two ends of the oval. After this take G as
a centre, and with a radius from G to 0 at E or G de-
scribe that part of the circle L from 0 L 0, which forms
the upper side of the oval ; now take F as a centre, and
with the same radius describe the lower side, joining K K
at 0 and 0, thus forming the plan of the oval as shown
by the line ALB, and the dotted line below G. It will be

METHODS OF WORK ^ 231

seen that the respective centres to describe this figure
give the centres and diameters to run the two circle
mouldings from which the ovals are formed.

To construct the oval, first make a running mould to
the desired profile, using a radius-rod in the usual man-
ner, for running circles on the flat. Before running the
mouldings, set out two lines at right angles on the mould-
ing board, taking care to extend the lines a little be-
yond the outline of the large circle, as shown by the
dotted lines (Fig. 2), The extended parts of these lines
act as guides for cutting the moulding into exact quad-
rants. The intersection of them is the centre from
which both circles are run. Apply the running mould,
and turn it round, so that it leaves a faint mark on the
running board to indicate the width of the moulding to
be run. The width can also be marked by the aid of a
pencil, holding it at the outside member, and turning the
mould round, repeating this operation on the inside mem-
ber. On this space drive in eight tacks, two in each
quadrant, leaving the heads projecting about ^ inch.
The object of these tacks is to prevent the moulding
from lifting owing to plaster swelling, or from moving
round while being run. Cover the tacks with clay to
allow the moulding to be freely taken up after it is run
and cut. The moulding is then run in the usual way,
and is cut into four quarters, or quadrants. This is
done by applying two set-squares, one inside and one
outside of the moulding ; and at one of the quarter lines
lay a straight-edge over the moulding and against the
set-squares. The moulding can then be marked or sawn
at the proper place and angle. The dotted or quarter
lines divide the mouldings into quadrants, and give the
angles for cutting them.

232 CEMENTS AND CONCRETES

The use of extending the lines beyond the moulding
will here be seen. A part may be obliterated while the
moulding is being run, but the extended part will af-
ford a correct guide for the outside set-square. If the
quadrants are cut fine, square, and clean, the joints will
be scarcely perceptible when the four segments are
placed together. When this circle is cut and taken oflp
the board, the radius has to be altered to exactly one-
half of the large circle, and the small circle is run and
cut precisely in the same way as the large one. The four
quadrants can now be fixed to form an oval, as shown
in Fig. 3. If a quantity of oval mouldings be required,
a casting mould can be taken off this oval in which they
may be cast. It will be seen that the quadrants M and
N 1 form the sides of the oval in Fig. 3, and the quad-
rants M and M 1 form the ends. It will also be seen that
after completing this oval there are four quadrants left
to form another oval. If but one oval is required, run
only one-half of each circle, allowing a little space
beyond the centre line, so that a square and clean Jomt
can be cut. A thin saw with fine small teeth should be
used for this purpose.

Fig. 3 shows the four segments of the moulding in
position forming the oval. In this figure the moulding
is struck on the outside of the setting-out circle line, as
shown in Fig. 1, but the moulding in Fig. 2 is struck on
the inside of the setting-out lines. This is simply to
show that the same centres can be used for mouldings
struck on either side of the lines. A mould for casting
oval mouldings, also templates, can also be made by the
above process. For this purpose a reverse running
mould must be used for running the two circles. A
plaster piece mould for casting oval mouldings that are
undercut may also be formed by this method. In this

METHODS OF WORK . 233

case the running mould must be made and used as de-
scribed for ** reverse moulds."

Coved Ceilings.-^CoYes to ceilings are of various
heights, as one-third, one-fourth, one-fifth, &c., of the
whole height. The form of the cove is generally either
a quadrant of a circle or of an ellipsis, taking its rise, a
little above the cornice, and finishing at the crown or
other moulding. If the room is low in proportion to its
width, the cove must likewise be low; and when it is
high, the cove must likewise be so ; by which means the
excess of height will be rendered less perceptible. An
example of two coved ceilings (from designs by James
Gibbs) are shown is the annexed illustration No. 22.
Fig. 1 shows the plan and elevation of a coved ceiling,
with circular windows between the groius. Fig. 2 shows
the plan and elevation of a coved ceiling, the design of
which is less intricate than that of Fig. 1. The curve
of this cove is a quadrant of a circle, as shown by the
section at the side. The plans will enable the section
of each design to be understood, and vice versa, and the
whole will render the method of constructing coves and
circular mouldings on circular surfaces (which is given
hereafter) to be more clearly understood. The external
and internal angle mouldings in these coves may be'
formed with a jack template or as described for coves.

Circle Mouldings on Circular Surfaces, — The accom-
panying illustration, Plate III, is given to elucidate
various methods of running circular mouldings on cir-
cular surfaces, shows the elevation of a cove suitable for
an aquarium or marine hall. The external angle rib
moulding, C, and the panel rib moulding, D, spring from
the top or weathering of a main moulding, and intersect
with a horizontal or crown moulding at the top of the
cove. The section of the horizontal moulding is shown

234 CEMENTS AND CONCEETES

"Li

METHODS OF WCJRK 235

at G, and the section of the panel moulding is shown
above D; the section of the exteMal rib being of course
double that of the panel moulding. Where circular or
straight mouldings intersect mlh^ each other, it is ad-
vantageous in most cases to run' the circular mouldings
first, so that the whole of the moulding can be run,
and leave the intersection to be mitred on the
straight part, which is naturally the easiest part. In
some examples it is not advis«b& to run the circular part
first. For example, if the crbwii or horizontal moulding,
as shown at G, Fig. 1, was the lower part of a large
crown moulding made to intersect with small cove
mouldings, it would be best to run the straight moulding
first, and then cut away as much of the straight mould-
ing as will allow the nib of the running mould to pass
wl^ile running the circular moulding. For the section
in this example there would be verj^ little mitring to do,
aa it would simply be a butt liiitre up to the back of the
circular mouldings. The ei^S^al rib moulding, C, is
best run with a jack template* The circular panel
mouldings (one-half of a moulding is shown at D) can
be run by two methods. By the first, th6 moulding is
run in three parts, using a sledge-slippered' running
mould fixed on a hinged radius-rod, and the two straight
parts are run from running rules. By the second
method, the whole moulding is run at one operation by
using a fibrous plaster template, made as already de-
scribed.

Forming Niches.-^'Niches are recesses formed in walls,
sometimes for the purpose of placing some ornamental
object in them, such as statues, vases, &c., and they are
often constructed in thick walls^in order to save mate-
rials. The plans or bases of niches are generally semi-
circular, but some partake of all the segments under a

236 CEMENTS AND CONCRETES

semicircle, while others are elliptical, and in a few in-
stances they are square or rectangular. The elevations
of niches are generally in accordance with their plans,
but variations from this rule are sometimes met with.
The crown or heads of niches are generally plain, but
they are sometimes enriched with scalloped shells, &c.,
or panelled with mouldings. With respect to the pro-
portion of niches, there is no fixed rule, but the general
one is twice and a half their width for their height.
Various methods are employed in the formation of
niches. The crowns of circular niches are generally run
with a mould, because being circle on circle and small
in surface, it is difficult to finish them true and smooth
by hand.

The accompanying illustration (No. 23) .elucidates
two methods of forming semicircular niches with the aid
bf running moulds. Fig. 1 shows the elevation, and Fig.
2 the section of the crown and a part of the body of
niche, with the centre-boards and moulds in position
when forming the crown of the niche. Fig. 4 shows the
section of the body of the cove, with the mould in posi-
tion when forming same. By the first method the niche
is formed in two operations, and by the second method
it is formed in one operation only. For the first method,
cut a running mould to the section of the niche, as shown
at B, Fig. 1, then fix it on the centre board. A, with two
hinges, keeping the upper surface or mould plate level
with the top edge of the centre board, as shown on the
section of the niche. Fig. 2. This also shows the end
section of the centre-board and the mould, with the
mould plate and a hinge. The dotted line indicates the
distance the mould travels. After this, fix the com-
bined centre-board and mould on the wall, taking care
that the top edge of the centre-board is level and ex-

METHODS OF WORK

F^e

238 CEMENTS AND CONCRETES

actly at the t^pringing of the crown, C. The face of the
wall must be floated plumb, and an allowance made by
means of dots for the thickness of the setting coat be-
fore the centre-board is fixed. After the crown is fin-
ished, the centre-board and running mould is taken off
the wall and separated. The mould is then horsed with
two slippers to allow of its running the body or vertical
part of the niche. The mould works on a running rule
fixed on one of two screeds, which are formed on the face
of the wall, one on each side of the opening. Care must
be taken that the screeds are plumb with the centre-board
dots. Fig. 3 shows an elevation of the mouldy when
horsed. B is the mould, D is a connecting board on
which the mould is fixed by means of the cleats, C, C,
and F, F, are the slippers,. Fig. 4 shows an end section
of the horsed mould" in^ position when running the body
of the niche. The base is finished by hand.
• By the second method the niche is run in one opera-
tion, as already mentioned. This is effected by cutting
a running mould to the vertical section of the niche, then
fixing a pivot at the bottom and a bolt at the top. A
wood block, with a socket to fit the bolt on the mould, is
let into the face of the wall at the top of the niche,, and
temporarily fixed, then another block with a socket to fit
the pivot of the mould is fixed at the bottom of the
niche. Care must be taken that the sockets are plumb
and in a line w.ith the centre of the niche, also that they
are in a line with the face of the wall, so as to allow
the mould to form a true semicircle with perpendicular
arrises. Place the pivot of the mould in the socket, and
push the bolt up and secure it, and the mould is ready
for working.

Fig. 5 shows a section of the niche with the mould in
position. A is the mould with the pivot and bolt, and

METHODS OWmOBK 239

B, B, are the socket blocks. A plan of the niche and
mould is shown at Fig. 6. This abo shows the plan of
the pivot block, and a board whibhas' sometimes used to
secure the block. The dotted line indicates the dis-
tance the mould travels. Wheii there are splays or beads
on the angle of the- niche, the>rown part is run with a
radius-rod mould Srom a centine-board, and the vertical
parts with a *'twin-islipp<gr running mould/' on running
rules fixed on the Wall screeds,' or with a nib running
mould on a slipper and a nib running ruIe/7; ,

The vertical part* of the beads or splays ^ihay also be
ran with the mould shown in Fig. 3. For this purpose
two plates cut to the desired section must be fixed on the
mould, one at each side. The crown part is run with a
radius-rod, as already mentioned. The crown surface
and the angle moulding can also be run in one operation.
This is effected by cutting a mould plate to the section of
the moulding, including the section of the crown sur-
face, then horsing it with a slipper to run on the wall
surface, and a pivot to fit a socket formed in a centre-
board, or with a radius-rod to work on a centre-board.
A pivot will be found mast suitable for small work and
a radius-rod for large work. In either case they must
be fixed on the centre of the mould, so as to be in a line
'with the mould plate. After the crown is run, the mould
plate of the crown surface is cut off, and the remaining
part of the mould used for- running the vertical mould-
ings.

In some designs a small moulding, such as an impost
moulding, is carried round the body surface of the niche,
-and in a line with the springing of the crown. This
(moulding can be run in a similar way as shown at Fig.
5, or by fixing a flexible wood or a plaster running rule
'ion.the body of the niche for the mould to run on.

240 CEMENTS AND CONCRETES

The crowns of niches that are parallel with small
mouldings are best executed by making a model of the
design, then moulding it and casting, and fixing as many
as are required. In niche crowns that are enriched
with shells, foliage, &c., the enrichment should be cast
with the crown surface Qi^.a background. Fibrous plas>
ter is well adapted for tke coilstruction of niches. For
this purpose a reverse casting mould should be employed
for forming the casts. This is made by cutting a re-
verse running mould to the section of the niche, and after
a sufficient length of the body is run, cut the mould in
half and run the crown. Then fix it on the end of the
run body, and then fix rules at the sides and ends to
form fences and rims, thus completing the casting
mould.

Any of the above methods for forming niches with
running moulds can be advantageously used for forming
the body and crown of the Ionic niche when such is re-
quired.

RuNNiNQ AN Elliptical Moulding- in Situ.

In No. 24 a method of running an elliptical curve with
a trammel is shown. Fig. 1 represents the front eleva-
tion of the trammel mounted and in working order, and
Fig. 2 is a section of the same.

Take two floor boards, B, long enough to reach to the
springing line of the arch, and nail them on the back of
two lengths of 5 in. by 2 in.. A, which, as shown may be
somewhat longer. Fix these up inside the jambs of the
opening, taking care to see that they are perfectly up-
right, and keep them the thickness of the trammel boards
(which is 1 in.) back from the face of the opening on
whijch the architrave is to be. Then cut three pieces o£

METHODS OP WORK

241

5 in. b7 2 in., C, tight in between and secure them in
place with 3 in. cut nails, taking care to aee that the'
bottom side of the top one is above the springing line.
Then prepare the trammel boards, D and E, 6 in. by 1

in., and cut the slots, which are % in. wide and of a
length which may be easily ascertained by simple geom-
etry. Halve the boards together at the joint and fur-
ther secure them by screwing a plate of the thickest sheet
mnc (dbtaiaable dn the hack, as per Fig. 3. Nail the

242 CEMENTS AND CONCRETES /

boards up as shown, keeping the horizontal slot central
on the springing line and the vertical slot exactly in the
centre of the opening, and be most particular to see that
the whole lot is perfectly upright and level. Next pre-
pare the trammel stick, 2 in. by 1 in., and mount the
mould on the top in the usual majiher, as shown. Then
insert the pins in holes bored in the stick and secure by
a screw through the edge. Have them just thick enough
to work comfortably in the slots, and keep the centre of
the pin XI, the distance of the rise, and the centre of
the pin* X2, the distance of the half span from the hot-
tom member of the architrave. All the timber may be
deal except the pins, which must be of some kind of hard
wood. If well made and used with care this trammel
ought to serve many times ; the pins, of course, needing
adjustment for arches of different size.

MISCELLANEOUS MATTERS.

Depeter. — This is a sort of a rough-cast, and consists
of forming a fair surface with coarse stuff or Portland
cement. As soon as laid a hand-float is parred over the
surface a few times to give it an even and uniform tex-
ture, and wh"'^'* it is soft, pressing in by hand, small
pieces of hard coal, broken bottles, pottery, bricks, shells,
stones, pebbles, or marble. The design may be varied and
enriched by using various colored pieces in forming mar-
gins, bands or other ornamentation. On the contrast of
colors and the broad bands depends the effect of this
class of work. A combination of ** Depeter" and rough-
cast may be used with excellent effect.

Sgraffitto, — Sgraffitto or **graffitto" is an Italian word,
and means ''scratched." Scratched decoration is the
most ancient mode of surface decoration employed by
man. The primitive savage of the flint-weapon period
used this simple form of ornamentation. Scratched
work, as used by prehistoric man, may be fitly termed
the proem of the civilized arts of drawing, modelling and
sculpture. The term is now employed for plaster deco-
rations, scratched or incised upon plaster or cement be-
fore it is set. It may be used for both external and
internal decoration. The annexed illustrations (Nos. 25
and 26) will demonstrate the high degree to which the
art of sgraflStto attained in Italy.

Some graffittos are really low relief work rather than
the SgraflStto, they being very deep cut with the iron or
steel i)oint, which was necessitated by the final coat be-
ing plastered on instead of washed on. Deep cutting

243

CEMENTS AND CONORfi¥ES

L V.

MISCELLANEOUS MATTERS 245

gives a hard appearance to the design, prevents the water
from running oflf the walls, and catches the dirt. In exe-
cnting true sgraffitto, the cut or scratch should be ex-
ceedingly slight — in fact, some parts scarcely percepti-
ble.

SgraflStto decorations do not suffer materially from
stubbing it with an old broom, leaving it barely half an
inch from the finished face. For internal work, the ordi-
nary pricking up suffices. When this is dry, a thin coat
of selentic lime mixed with the desired coloring matter
for the background, is floated over it. This background
may be black, bone-black being used ; red, for which use
Venetian or Indian red, or the ordinary purole brown
of commerce, singly or mixed, to produce any tone de-
sired; yellow, produced by ochres or umbers; blue, by
German blue, Antwerp blue, or any of the commoner
blues, avoiding cobalt, and these colors you may use to
any degree of intensity cr paleness. When this coat is
nearly dry, skim over it a very thin coat of pure selentic
lime, which dries of a parchment color and generally
suffices. If you want a pure white lime, use a moderate
quick-setting one, as stiff as you can work it, and as
each variety of lime has its own individual perversity, I
can give no general direction, and would advise the be-
ginner to ^tick to selentic, which is always procurable.
You have, of course, prepared your cartoon. This is
pricked and pounced as for any other transfer process,
and then with an old, well-worn, big-bladed knife, for
there is no b^er tool, you can cut round all the out-
lines, and with a flat spatula clear away all the thin
upper coat, leaving the colored ground as smooth as you
can. If your plaster is not quite dry enough for the
two coats to separate easily, wait a little longer, but not
too long, for that is fatal. By the time you have cleared

246 CEMENTS AND CONCRETES

out your background, the plaster will be in a good con-
dition to allow you to cut out the .finer parts of the de-
sign, such as folds of the draperies, or the finer lines of
the faces or of the ornament. Use your knife slightly
on the slope, and if you want to produce half-tones, slope
it very much; but, as a rule, the more you avoid half-
tones, and the simpler and purer your line, the more
effective your work will be. Recollect, above all things,
you are making a design and not a picture, and you
must never hesitate, for to retouch is impossible. Some-
times it may be desirable to gild the background, and
you can then carve or impress it with any design you
choose. It occasionally happens you want to give some
semblance of pictorial character to your work when it is
small in scale and near the eye, and then you can pro-
ceed as though you were cutting a wood-block.

By cutting out your ground color in places, and
plastering it with that of another color, you may vary
any portion of it you desire. You can also wash over
certain parts of your upper coat with a water-color if
you desire, combining fresco with the sgraflStto, both of
which manners are often used ; but, as a rule, the broader
your design, and the simpler your treatment of it, the
better. It will be seen that this process is very available
for simple architectonic effects; and for churches, hos-
pitals, and other places where large surfaces. have to be
covered, it is the least costly process that can be adopted.
It has also the great advantage of being non-absorbent,
and it can be washed down at any time. The artist is
untrammelled by difficulties of execution, but he should
bear in mind that the more carefully he draws his lines
and the simpler he keeps his composition, the more
charmed with the process he will be, and the better will
be the effect of his work.

MISCELLANEOUS MATTERS 247

A well-known artist records- his experience of sgraffitto
as f(»llows:

**Rake and sweep out the mortar joints, then give the
wall as much water as it will drink, or it will absorb
the moisture from the coarse coat, as it will not set, but
merely dry, in which case it will be worth little more
than dry mud. Care should be taken that the cement
and /sand which compose the coarse coat should be prop-
erly gauged, or there may be an unequal suction for the
finishing coats. The surface of the coarse should be
well roughened to give a good key, and it should stand
some days to thoroughly set before laying the finishing
coat. "When sufficiently set, fix your cartoon in its des-
tined position with nails; pounce through the pricked
outline; remove the cartoon; replace the nails in the
register. holes; mark with chalk spaces for the different
colors, as indicated by the pounce impression on the
coarse coat ; lay the several colors of the color coat ac-
cording to the design as shown by the chalk outlines;
take care that in doing so the register nails are not dis-
placed; roughen the face in order to make a good key for
the nnal ooaL When set, follow on with the final sur-
face coat, only laying as much as can be cut and cleaned
up in a day. When this is sufficiently steady, ^x up the
ca'rtoon in its registered position ; pounce through the
pricked outline ; remove the cartoon, and cut out the de-
sign in the surface coat before it sets; then if the regis-
ter is correct, cut through to different colors, according
to the design, and in the course of a few days the work
should set as hard aad as homogeneous as stone, and as
damp-proof as the nature of things permit.

*' When cleaning up the ground of color which may be
exposed, care should be taken to obtain a similar quan-
tity of surface all through the work, so as to get a broad

248 CEMENTS AND CONCRETE^

effect of deliberate and calculated contrast between the
trowtelled surface of the final coat ©nd the scraped sur-
face of the simple contrasts of light againjst dark, or
dark against light. The following are the proportions
of the various coats : ♦

** Coarse eoats : One of Portland cement to 3 of washed
sharp co€krse sand.

** Color coat: One and one-half of air-slaked Port-
land to 1 of color laid Ys inch thick. Distemper colors
are Indian red, Turkey red, ochre, umber, lime blue;
lime blue and ochre for green; oxide of manganese for
black. In using lime blue, its violet hue may be over-
come by adding a little ochre. It should be noted that
it sets much quicker and harder than the other colors
named.

** Final coat, internal work: Parian, air-slaked for
twenty-four hours to retard its setting, or fine lime and
selenitic sifted through a fine sieve.

**For external work: Three selenitic and 2 silver
sand.

**When finishing, space out the wall according to the
scheme of decoration, and decide where to begin, and
give the wall in such place as much water as it will
drink; then lay the color coat, and leave sufficient key
for the final coat. Calculate how much surface of color
coat it may be advisable to get on to the wall, as it is bet-
ter to maintain throughout the work the same duration
of time between the laying of the color coat and the fol-
lowing on with the final surface coat; for this reason,
that if the color sets hard before laying the final coat, it
is impossible to get up the color to its full strength wher-
ever it may be revealed in the scratching of the decora-
tion. When the color coat is quite firm, and all shine
has passed away from its surface, follow on with the

MISCELLANEOUS MATTERS 249

final coat, but only lay as much as can be finished in one
day. The final coat is trowelled up, and the design
is incised or scratched out. Individual taste and experi-
ence must decide as to thickness of final coat, but if laid
between % inch and 1-12 inch, and the lines cut with
slanting edges, a side light gives emphasis to the fin-
ished result, making the outlines tell alternately as they
take the light or cast a shadow."

Another method which I have used in sgraffitto for
external decoration was done entirely with Portland
cement. This material for strap-work or broad foliage,
or where minuteness of detail is unnecessary, will be
found suitable for many places and positions. Three
colors may be used if required, such as black for the
background, red for the middle coat, and grey or white
for the final coat. These colors may be varied and sub-
stituted for each other as desired, or as the design dic-
tates. The Portland cement for floating can be made
black by using black smithy ashes as an aggregate, and
by gauging with black manganese if for a thin coat. The
red is obtained by adding from 5 to 10 per cent, of red
oxide, the white by gauging the cement with white mar-
ble dust, or with whiting or lime, the grey being the nat-
ural color of the cement. After the first coat is laid,
it is keyed with a coarse broom. The second coat is laid
fair and left moderately rough with a hand-float. The
suction of the first coat will give suflScient firmness to
allow the third coat to be laid on without disturbing the
second. The third coat should be laid before the sec-
ond is set hard. The second and third coats may be
used neat, or gauged with fine sifted aggregate as re-
quired. The finer the stuflf, the easier and cleaner the
work, and the cut lines are more accurate and free from
jagged edges. The outlines of the desigiT may be

250 CEMENTS AND CONCRETES

pounced or otherwise transferred to the surface of the
work, and the details put in by hand. The thickness of
the second coat should be about 3-16 inch, and the third
coat about % inch. The thickness of one or both coats
may be varied to suit the design. The beauty of effect
of this method of linear decoration, aided by two or
three colors, depends greatly on the treatment of design,
the clearness of the incised lines, and the pleasing color
contrasts. It will be seen that in the three methods
described there is a similarity, yet the method of using
two color coats on a dark floating coat will give more
variety aud effect. There is a large use for sgraffitto in
the future, as it has been in the past, and its use is inti-
mately bound up with the f Mure of cement concrete.

In order that the foregoing examples of high-class
sgraffitto may not deter the young plasterer from trying
his *' 'prentice han' *' in this class of work, some simple
designs are given in the annexed illustration (No. 27).
Fig. 1 shows a design for a frieze in two colors. The
ground may be black or red, and the ornament buff or
grey. The colored material for the ornament is laid
first, and the colored material for the ground laid last.
Fig. 2 shows a design for a cove in two- colors, one with
two shades. The ground is grey, and the band work
buff. A deeper shade of buff for the honeysuckle can be
obtained by brushing this part with liquid color made
deeper than the original gauge, also by laying a black
coat first, and in a line with the honeysuckle ; then laying
the buff stuff for the band work next, and then laying
the grey color last. In the latter case the honeysuckle
is cut deeper than the band work, so as to expose the
black coat.

Different effects can be obtained by changing the col-

MISCELLANEOUS MATTERS 251

orB. SeeUoDS of the surface of the frieze and part of the
moulding are shown at the ends. ,

Fresco. — The plasterer is closely allied to the artist
painter. He has always to be in readiness to plaster the
wall for the artist. Owing to the alliance with distin-
^ished artists, and the various methods of preparing
and iising the plaster materials, I am induced to give a
few notes, also extracts from writers of authority.

; IN Two Colours.

Fresco is a mode of painting with water-colors on freshly
laid plaster while it remains naturally wet. It is called
"fresco" either because it was originally used on build-
ings in the open air, or because it was done on fresh
plaster. Fresco is an ancient art, being mentioned by

252 CEMENTS AND CONCRETES

Pliny. Mr. Flinders Petrie found some remarkably fine
specimens on floors and walls at Tel-el-Amarna, which
reveal the state of the art four thousand years ago. Pine
frescoes were discovered in the ruins of Pompeii. In
one of the principal houses the plaster walls are adorned
with theatrical scenes; in an inner room is the niche
often to be seen in Pompeiian houses. The frescoes on
the wall consist of floral dados. Above this is a whole
aquarium, with shells, plants, birds and animals. They
are all executed in their natural colors, and are natur-
ally and gracefully drawn. Michael Angelo's beautiful
fresco on the ceiling of the Sistine Chapel in the Vatican
is grand both in conception and execution. It measures
133 feet in length by 43 feet in width. Raphael's fres-
coes in the Vatican, Famesina Palace, &c., are wonder-
fully fine, and may be regarded as the high-water mark
of Cinque Cento decoration.

For fresco or huon fresco^ the lime has to be care-
fully run, and the sand should be white, clean, and of
even grain, being well washed and sifted to free it from
impurities or saline properties. Silver sand is pre-
ferred by some artists. The older the putty lime, the
better the results. The lime is slaked in a tub, and then
run through a fine wire sieve into a tank, and after being
covered up, is left for three months. It is then put into
the tub again, and re-slaked, or rather well worked, and
run through a fine hair sieve into earthenware jars or
elate tanks, and the water which collects at the top drawn
or poured off, the jars or tank being covered over to ex-
elude the air. Lime putty in this state will keep for an
indefinite time without injury. From 2 to 4 parts of
sand to 1 part putty is usual. Marble dust alone is
sometimes used in place of sand, and also sand with
equal parts. Every difference of lime and sand found

MISCELLANEOUS MATTERS 253

in various localities should be considered and tested be-
fore using. A soft sand is quickly dissolved by a
strong lime, and a plaster made of this is fit for use
sooner, aud will deteriorate more quickly than a plaster
made with a less powerful lime and a harder sand, or
with marble dust.

The wall surface to be plastered must be well scraped
and hacked, the joints raked out and brushed, and the
whole surface well scrubbed and wetted. The rendering
is done with the best possible prepared old coarse stuff.
If the walls are rough or uneven, they should be first
pricked up and then floated. In any case, the surf ace
is left true, and with a rough face, to receive the fin-
ishing coat. Portland cement or hydraulic lime gauged
with sand, also gauged with coarse stuff, has been used
where the walls were damp (damp is fatal to fresco),
or if exposed to the atmosphere. When Portland cement
or hydraulic lime is used, the work should be allowed to
stand until thoroughly dry to allow any contained sol-
uble saline efflorescence to come to the surface. This is
brushed off with a dry brush, and a few days are allowed
to elapse to see if there is a further efflorescence. When
this is all extracted and swept off, and the artist is ready
to commence, the wall is washed with a thin solution of
the fine setting stuff, and then laid about % inch thick,
with well-beaten, worked, and tempered fine setting
stuff. It is then rubbed with a straight-edge and scoured
with a hand-float (using lime water for scouring) until
the surface is true and of uniform grain. Most artists
prefer a scoured surface without being trowelled. No
more surface should be covered than can be conven-
iently painted in one day. While the plaster is still
soft and damp, the cartoon is laid on, and the lines and
details pounced in or indented by means of a bone or

254 CEMENTS AND CONCRETES

hard-wood tool. Should the finishing coat get too dry
in any part, it can be made fit for work by using a fine
spray of water. The method of plastering and the gaug-
ing of materials may slightly vary according to the de-
sire of the painter aad the kind of fresco in hand. The
following is taken from an old manuscript dated 1699 : —

**1. In painting the wall to make it endure the
weather, you must grind colors with lime water, milk, or
whey, mixed in size.

**2. Then paste or plaster must be made or well-
washed lime, mixed with powder of old rubbish stones.
The lime must be often washed till finally all the salt ie
extracted, and all your work must be done in clear and
dry weather.

*'3. To make the work endure, stick into the wall
stumps of headed nails, about 5 or 6 inches asunder, and
by this means you may preserve the plaster from peeling.

**4. Then with the paste plaster the walls a pretty
thickness, letting it dry; but scratch the first coat with
the point of your trowel longways and croesways, as
soon as you have done laying on what plaster or paste
you think fit, that the next plastering you lay upon it
may take good key, and not come off nor part from the
first coat of plastering; and when the first coat is dry,
plaster it over again with the thickness of half a barley-
corn, very fine and smooth. Then, your colors being al-
ready prepared, work this last plastering over with the
said colors in what draught or design you please — his-
tory, etc.,t — ^so will your painting unite and join fast to
the plaster, and dry together as a perfect compost.

*'Note — ^Your first coat of plaster or paste must be
very haired with ox-hair in it, or ebe your work will
crack quite through the second coat of plastering; AAd
will spoil all your painting that you paint upon the see-

MISCELLANEOUS MATTERS 255

ond coat of plastering; but in the second coat that is
laid on of paste or plaster there must be no hair in it at
all, but made thus: —

Mix or temper up with well-washed lime, fine powder
of old stones (called finishing stuff) and sharp grit sand,
as much as you shall have occasion for, to plaster over
your first coat, and plaster it all very smooth and even,
that no roughness, hills, nor dales, be seen, nor scratch of
your trowel. The best way is to float the second coat of
plastering thus: — ^After you have laid It all over the
first coat with your trowel as even and smooth as pos-
sible, you can then take a float made of wood, very
smooth, and 1 foot long and 7 or 8 inches wide, with a
handle on the upper side of it to put your hand into
to float your work withal, and thus will make your
plastering to lie even; and lastly, with your trowel you
may make the said plastering as smooth as possible.

*'5. In painting be nimble and free; let your work
be bold and strong ; but be sure to be exact, for there is
no alteration after the first painting, and therefore
heighten your paint enough at first ; you may deepen at
pleasure.

'*6. All earthy colors are best, as the ochres, Spanish
brown, terra-vert, and the like. Mineral colore are
naught.

**7. Lastly, let your pencil and brushes be long and
soft, otherwise your work will not be smooth; let your
colors be full, and flow freely from the pencil or brush;
and let your design be perfect at first, for in this there
is no alteration to be made."

Fresco /Secco.— Closely allied with the genuine fresco
(fresco buono) is another kind called fresco secco (dry),
or mezzo (half) fresco. The plaster work for fresco sec-
co is similar to that used for fresco buono. It is allowed

256 CEMENTS AND CONCRETES

to stand until thorougMy dry. The surface is then
rubbed with pumice-stone, and about twelve hours before
the painting is commenced it is thoroughly wetted with
water mixed with a little lime. -The surface is again
moistened the next morning, and the painting begun in
the usual way. If the wall should become too dry, it is
moistened with the aid of a syringe. There is no fear of
joinings in the painting being observable, and the artist
can quit or resume his work at pleasure. Joinings are
distinctly noticeable in the frescos in the Loggia of the
Vatican. Fresco secco paintings are heavy and opaque,
whereas real fresco is light and transparent. While the
superiority of fresco buono over fresco seceo for the
highest class of decorative painting is unquestionable,
still the latter is suitable for many places and forms of
decorative paintings. The head by Giotto in the National
Gallery, from the Brancacci Chapel of the Carmine at
Florence, is in fresco secco.

Indian Fresco and Marble Plaster, — ^''Fresco painting
is a common mode of decoration in Jeypore, and is used
in ornamenting walls inside and outside of buildings —
also as a dado or border round the wainscot or on the
floor — and on any surface where decoration is desired.
The beautiful marble plaster on which it is done is com-
mon Rajputana, and is used to line the surface of walls
or floors, and of baths or bath-rooms. It is admirably
adapted to places where coolness and cleanliness are de-
sired, and is very suitable to a warm climate. It would
no doubt be more commonly used if pure lime could be
obtained.

* * To prepare the marble plaster, the process in use in
Jeypore is as follows: — Take pure stone lime, mix
it with water until it has dissolved, then strain it through
a fine cloth. In Jeypore the lime is made from pounded

MISCELLANEOUS MATTEES 257

marble chips or almost pure limestone. The substance
which remains in the cloth is called bujra, and all that
passes through the cloth is called ghole. These should
be prepared a few days before they are required so as
to allow time to settle, and every day the water should
be changed, so as to leave a very fine sediment.

**Jinki, which is also used, is pure marble ground to
a very fine powder; kurra is a mixture of bujra and
jinki; and jinkera is a mixture of ghole and kurra.
These are the materials used, and the names by which
they are known in Jeypore. In Madras, where similar
plaster is used, it is made, I believe, from shells and the
ingi'edients are probably known by other local names.

''If the surface to be polished is a slab or stone, the
kurra mixture consists of 1 part by weight of burja and
iy2 parts of jinki. If the surface is a wall of a chunam
floor, it must be first thoroughly dry and consolidated —
then take equal parts of burja and jinki to form the
kurra mixture. Mix the burja and the jinki well to-
gether; add a little water and grind them well together,
in the same ways as natives mix their condiments, by
hand with a stone rolling-pin on a slab, until they form
a perfectly fine paste. Wet the surface which is to be
polished, and spread over it a layer of this kurra mix-
ture, about Yg inch thick. Then beat the surface gently
with a flat wooden beater, sprinkling a few drops of
clean water on the surface occasionally. Then mix a
little ghole with the kurra plaster, (described above as
jinkera) and lay it on evenly with a brush as if it were
a coat of paint ; rub the surface over carefully with any
^lose-grained flat stone, called in Jeypore jhaon. The ob-
ject of this is to smooth down all irregularity and
roughness, and to prepare a smooth even surface.
Sprinkle a few drops of water and repeat the process^

258 CEMENTS AND CONCRETES

taking care that no hollow places are allowed to re-
main. Paint it over with fine jinkera (ghole and
kurra mixed), increasing the proportion of ghole, and
rub it down well with a flat stone (jhaon) as before;
then paint it over with ghole only, after each coat rub-
bing it down carefully with the jhaon stone. After this,
rub it all over with a soft linen cloth, called in Jeypore
nainsukh, folded into a pad. Then give it another coat
of ghole, and now rub it down carefully with a piece of
polished agate, called in Jeypore ghinti, until it begins
to shine. The surface must not be allowed to dry too
rapidly, or a good polish will not be obtained. Care
must be taken that the lime has been thoroughly slaked
in the first instance, or it may blister; also that the sur-
face, if a floor, is thoroughly consolidated^ as the least
settlement naturally causes the plaster to crack. The
polishing process with the agate cannot be repeated too
often; the more it is carefully done, the better will he
the polish. Every time the agate is moved backwards
it should be made to pass over a portion of its .t)revious
course, so as to prevent any mark or line at the edge.
Lastly, if the surface is to remain white, take some water
which has been mixed with grated cocoanut, and lay it
on the surface. Let it dry, and then rub it down with a
fine cloth folded into a pad. If any coloring is desired,
the same process is adopted until the polishing with the
agate is begun. This is only done slightly. If any pat-
tern is desired, it is drawn on paper and pricked out.
The paper is placed on the surface, and is dusted with
very finely powdered charcoal tied up in a muslin bag.
The charcoal passes through the perforations and marks
the plaster surface. The paints are mixed with water,
and are painted on by hand while the surface is still
fresh and moist hence the term fresco. Where a large

MISCELLANEOUS MATTERS • 259

surface has to bfe done, it is necessary to employ several
men at the same time, in order that the surface might
be all painted before it has time to dry ; or else the pat-
tern must be so arranged that the connection of one
day's work with the work of the next will not be amiss.
Immediately after the surface has been painted the
colors are beaten in with the back of a small trowel, in
such a manner that the color is not rubbed or mixed
with the color adjacent. As soon as it shows to the
touch that the color has become incorporated with the
plaster, the surface is painted over with water mixed
with grated cocoanut, and is then polished down with
the agate.

''The following colors can be used in process: — ^Lamp
black; red lead; green (from a stone known as hara
pathar) ; yellow (from a stone called pila pathar) ;
brown or chocolate. A little glue is mixed with the two
first colors, and gum only with the others. The colors
used are mostly earths or minerals, as other will not
stand the action of the lime. Vegetable pigments can-
not be used for this model of painting, even when mixed
with mineral pigments, and of the latter only these are
available which resist the chemical action of the lime.
The lime in drying throws out a kind of crystal surface
which protects the color and imparts a degree of clear-
ness superior to that of any work in tempera or size
paint. The process, although apparently simple, re-
quires dexterity and certainty of hand, for the surface
of the plaster is delicate, and the lime only imbibes a
certain quantity of additional moisture in the form of
liquid colors, after which it loses its crystallizing quality,
and the surface or a portion of it becomes rotten. It is
only after the lime has dried that such flaws are dis-
covered, and the only remedy is to cut away the de-

260 CEMENTS AND CONCRETES

fective portion, lay on fresh plaster and do the work
over again. The colors become lighter after the plaster
dries, so allowance must be made for this. The advan-
tages which this process possesses are clearness, exhib-
iting the colors in a pure and bright state; the surface
is not dull and dry as in tempera or size painting, nor
glossy as in oil painting; it can be easily seen from any
point, and it is not injured by exposure td the air; it
will stand washing, and can be cleansed with water with-
out injury." ^

SCAGLIOLA.

Historical. — Scagliola derives its name from the use
of a great number of small pieces or splinters; scagliole
of marble being used in the best description of this
work. It is said to have been invented in the early part
of the sixteenth century by Guido Sassi, of Cari, in
Lombardy, but it is more probable that he revived an
old process, and introduced a greater variety of colors
in the small pieces of marble and alabaster used to
harden the surface, and better imitate real and rare
marbles. It is sometimes called mischia from the many
mixtures of colors introduced by it. The use of colored
plaster for imitating marbles was known to the ancients,
although the pure white, or marmoratum opus and oZ-
barum opus, mentioned by Pliny, was more used. The
plastic materials used by the Egyptians in coating the
walls of their tombs partook of the nature of marble.
The ancients also used a marble-like plaster for lining the
bottoms and sides of their aqueducts, which has endured
for many centuries without spoiling or cracking. In the
decoration of their domes the Moors used colored
plasters, which have stood the ravages of time. The

MISCELLANEOUS MATTERS 261

beautiful chunam or plaster of India, as used by the
natives, has a hard surface, takes a brilliant polish rival-
ling that of real marble, and has withstood for many
ages the sun and weather without sign of decay. The
roofs and floors of many houses in Venice are coated with
smooth and polished plaster, made at a later date, strong
enough to resist the effects of wear" and weather,
without visible signs of crack or flaw, and without much
injury from the foot. Scagliola was largely employed
by the Florentines in some of their most elaborate works.
It has been used in France with great success for archi-
tectural embellishment. The rooms are so finished that
no additional work in the siiape of house-painting is
required, the polish of the plaster and its evenness of
tint rivalling porcelain. Scagliola is the material used.
At times the surface of the plaster is fluted, or various
designs are executed in intaglio upon it in the hiost
beautiful manner.

Scagliola is one of the most beautiful parts of decora-
tive plaster work, and it is regrettable that there should
not be a greater revival of such a charming and beautiful
art. Its limited use in recent times is greatly owing to
its manufacture being restricted by rules and rigid
methods and even prejudices, and being confined to
monopolists, who kept the method secret until it was
looked upon as a mystery which greatly enhanced its
cost. But through the information now at hand, com-
bined with a little practical experience and enterprise,
there is no valid reason why architects should not adopt
it for second or even for third class buildings. It
possesses great beauty, and is capable of affording grand
effects arid the richest embellishments in architecture.
Scagliola, in skilful hands, can be produced in every
variety of color and shade, in every possible pattern, in

262 CEMENTS AND. CONCRETES

every conceivable form and size, from a paper weight
to the superficial area of a large wall. It can be made
at a price that would enable it to take the place of the
most durable material now in use. Experience has
proved that it will last as long as the house it adorns,
and with an occasional cleaning, it will always retain its
polish and beauty. It has been produced in past days
in our own and other lands, and carried to such high ex-
cellence, that many of the precious marbles, such as
jasper, verd antique, porphyry, brocatello, giailo an-
tique, Sienna, etc., have been imitated so minutely, and
with an astonishing degree of perfection, as to defy de-
tection. It will not only retain its polish for years, but
can be renovated at much less comparative cost than
painting and varnishing marbled wood, or plaster work.
It is cheaper and more satisfactory to use scagliola in
the first instance than to go to the expense of plastering
walls, columns, etc., with Keen's or other kindred ce-
ments, used for their hardness and ready reception of
paint, which are to be afterwards marbled and var-
nished. Both are imitations, but painted marble can
never be compared with scagliola, which has the look,
color, touch, and polish of the more costly natural
marbles.

Various Artificial Marbles, — ^Various patents have
been taken out for the production of artificial marbles,
having for their bases plaster of Paris. These patents
will be briefly mentioned here.

Evaux's Artificial Marble is composed of plaster mixed
with albumen and mineral colors, the ground being zine
white. Kowbotham also employed plaster and albumen
soaked in a solution of tannic acid. Lilienthal makes
an artificial marble with Keen 's cement, slaked lime, and
curdled milk.

MISCELLANEOUS MATTEES 26a

Pick's ^^Neoplaster/' — This composition was patented
in 1883, and is composed of 75 per cent, of plaster, mixed
with feldspar, marl, coke dust, and pumice-stone. Gule-
ton and Sandeman patented an artificial marble in 1876.
It is composed of Keen's cement backed with fibre, and
soaked dr brushed on the back with a solution of as-
phalt. Tlie slabs were made in glass moulds. La-
roque's patent marble is formed of plaster and alum
gauged with gum water, the veining being done with
threads of silk dipped in the required colors. The
backs of the slabs or panels are strengthened with can-
vas.

Mur Marble is composed of a mixture of Keen's and
Marin's cement in equal proportions, made into a paste,
with a solution of sulphate of iron and a small quanti-
ty of nitric .acid in water. The slabs are dried and
tarred at a temperature of 250 degrees F. for about
twenty hoursj and when cool are rubbed, colored, var-
nished, or japanned, as required. There is another
patent formed of plaster, gauged with a solution con-
taining tungstate of soda, tartaric acid, bicarbonate of
soda, and tartarate of potash. Another is composed of
Keen's cement 10 parts, ground glass 1 part, and alum
% part, dissolved in hot water. ,,

Guattaris Marble is obtained by transforming gypsum
(sulphate of lime) into carbonate of lime (marble).
There are two methods. The first consists of dehy-
drating blocks of gypsum, and then hardening by im-
mersion in baths containing solutions of silicate of soda,
silicate of lime, chloride of lime, sulphate of potash,
soda, acid phosphate of lime, etc. The blocks ai*e cut
into slabs or carved before being put into the bath. The
second method consists in dehydrating the gypsum, and
bathing in some of the above chemicals. They are then

264 CEMENTS AND CONCRETES

dried and burnt at a red heat, and allowed to cool.
After a second burning and cooling, the products are
ground as for plaster. This powder is called **Marmo-
rite''. The marmorite is gauged in a trough with some of
the water from the baths as above, kneaded into a paste,
and the colors added and mixed. The paste is then put in-
to moulds and pressed, and when set they are taken out,
dried, and finally polished. Mineral colors are used.
Yellow and its tints are obtained with citrate of iron
dissolved in oxysulphate of iron, sulphate of cadmium,
chloride of yttrium, chromate of lithium, and yellow of
antimony. Red and its tints are obtained with dragon 's
blood, sesquioxide of iron, mussaride red, and sulphate
of didymium, and the salts derived from it, which give
a rose color. Azure blue is obtained with sulphate of
sodium mixed with acetate of copper and tartaric acid
and oxide of cobalt. Green and its tints are obtained
with verdigris, hydrochlorate of cobalt. Black is ob-
tained by pyrolignite of iron reduced by boiling in gallic
acid with sirco black. Black marble is also obtained
by immersing gypsum blocks or slabs or the cast mar-
morite in a hot preparation of bitumen. During this
operation the dehydration of the material under treat-
ment is accomplished, and the bitumen not only pene-
trates the mass, but fills up all the pores and spaces
evacuated by the water which was contained in the ma-
terial treated, and a hard mass of brilliant black is ob-
tained in every way equal to Flanders marble. It is
said that the above imitation marbles are largely used in
Florence.

Scagliola Manufacture.— Sesigliolsi, can be made in situ
or in the work shop, according to the requirements of the
work; but in either case it is necessary that the work
place should be kept at a warm temperature, and the

MISCELLANEOUS MATTERS 265

work protected from dust or damp atmosphere. The
plaster should be the strongest and finest in quality, and
free from saline impurities. It should be well sifted to
free it from lumps or coarse grains, which otherwise
would appear as small specks of white in the midst of
the dark colors when the^ polishing is completed. Glue
water should be made in small quantities, or as much as
will sufBce for the day, as it deteriorates if kept too long.
Glue tends to harden the plaster, and gives gloss to the
surface. Unfortunately it is also the cause of its sub-
sequent dullness and decay when exposed to moisture
and damp air, hence the necessity of using the best glue,
good and fresh glue water. If scagliola is required to be
done in situ on brick walls, the joints should be well
raked out and the walls well wetted. This gives a good
key, stops the excessive absorption, and partly prevents
the evil effects of saline matters, that are found in most
kinds of new bricks. These saline matters are the prin-
cipal cause of subsequent efflorescence which sometimes
appears on plastic surfaces, and is so unsightly and dis-
astrous to surface decorations. Saline matters are* also
caused by acids, used in the manufacture of some ce-
ments. Saline is also found in mortars made with sea
water, or with unwashed sea sand. , These impurities
can be avoided by carefully selecting, mixing, and work-
ing of the materials. Brick walls for scagliola should
be allowed to stand as long as possible, and wetted at in-
tervals. This allows more time for the saline to exude
and be washed off. The exudation may be hastened or
the salts^absorbed and killed by brushing the walls with
a solution of freshly slaked lime. This is allowed to stand
until dry, and then cleaned off by scrubbing with warm
water and a coarse broom. If space permits, a wall bat-
tened and lathed is the best preventive. Scagliola slabs,

266 CEMENTS AND CONCRETES

screwed to plugs or battens, are protected from saline
and internal damp.

* Iron columns to support overhead weights, and fixed
as the building proceeds, are often covered with scaglio-
la. If the work is done in situ, the iron core is sur-
rounded with a wood skeleton and strong laths, or paint-
ed wire lathing. The wood templates are cut, equal to
the lower and upper diameters of the colunms, and one
fixed at the top and bottom of the shaft. The ground
work is then ruled fair with a diminished floating rule.
This gives a guide and equal thickness for the scag (the
trade abbreviation for scagliola stuff).

The floating coat is composed of the best and strong-
est plaster procurable, and gauged as stiff as possible
with suflScient strong size water, so that it will take from
twelve to twenty-four hours to set. The floating is gen-
erally brought out from the lath in one coat. A tenth
part of well-washed hair is sometimes mixed with the
gauged plaster, to give greater toughness and tenacity.
The surface must be carefully scratched with a singly-
pointed lath, to give a sound and regular key for the
scag, which is laid on in slices, and pressed and beaten
with a stiflSsh, square pointed gauging trowel, somewhat
like a margin trowel. The scag is laid about % inch
fuller than the outline, and when set, the surface is
worked down with a ''toothed plane.'' This plane is
similar to that used by cabinetmakers for veneering pur-
poses. The irons are toothed in various degrees of fine-
ness, and set at an angle of 70 degrees. If the columns
are fluted, a half-pound plane is required for the flutes.
As the planing proceeds, the outline is tested at inter-
vals with a rule, as a mason does in using a straight-
edge when working mouldings. A planed or chisel-cut
surface shows up the grain and figure of the marble

MISCELLANEOUS MATTERS 267

much better than if ruled. A rule is apt to woi^ out or
otherwise spoil the figure of most marbles. The beating
on the slices may disturb the figure of the marble at the
outer surface, but if the scag is gauged stiff, the inner
portion will be intact, hence the advantage of planing.
To obtain greater cohesion between the scag and the
floating, the latter is brushed with soft gauged stuff just
before each piece of the former is laid. The scratching
is also filled up at the same time, so as to obtain the full
power of the key with the least amount of pressing on
and beating the scag slices in position. When the shaft
is planed, the wood colors are taken off; then the base
and necking moulding, which has been previously cast,
are screwed in position, using plaster (colored the same
as the ground of the marble) for the joints. "JVhen dry,
the whole is stoned and polished. Pilasters or other
surface work done in situ are executed by similar pro-
cesses. Cast and turned work should always be support-
ed by strong wooden frames, formed with ribs, and cov-'
ered with 14 i^ch to ^ inch thick sawn laths. The
strength of the frames is regulated according to the posi-
tion and purpose of the intended work. For example, a
column with base placed on a square pedestal ^/ould not
require so strong framing as the pedestal which has to
support the column and base. Also being on the floor
level, it is more exposed to contact and pressure. Fram-
ing is also necessary for fixing purposes, and to allow
for the work being handled freely when being moved
from the work shop to the building, and when being
fixed. • Small work may be made without framing.
Turned columns are framed in two differeni methods,
each way being for a special purpose. If it is an ** in-
dependent column", or in other words a complete col-
Utnn, not intended to surround a brick or iron core, the

268 CEMENTS AND CONCRETES

frame is made lighter and thinner, and in such ways as
to admit the column to be ent either in two equal parts,
or with one-third ont, or jnst as much as will allow the
larg^ part to pass over the iron core. Care must be
taken that the inner diameter of the skeleton frame is
greater than the diameter of the iron core. This is to
allow for fixing. The outer diameter of the frame is made
about 1 inch less than the finished outline of column, to
allow ^2 i^ich for the core and % inch for the scag. The
two parts of the frame are fixed with wooden pegs (not
nails), so that they may be sawn when the column is cut
into halves. This is not done until the column is pol-
ished and ready for fixing. The parts are best separated
by cutting with a thin and fine-toothed saw. The thin-
ner the out the better the joint. The two parts are
fixed on the iron core with brass screws or clamps, from
3 to 4 feet apart, and the joints made good with colored
plaster as before. Sometimes a zigzag joint is made, the
'one side fitting the other, to give the marble or figure a
more regular and natural appearance. The joints are
then stopped with various tints, these being the same
gauge as used for the face.

Sometimes the framing is made longer than the shaft,
so as to project at each end. These projecting parts are
used as fixing points for screws, and binding round with
hoop-iron before the plinth and cap are fixed. These
parts project the edges of the work while being moved
and fixed. Considerable skill and patience is required
to make a strong joint, well polished, and imperceptible
to the eye. The frames are made with solid ends, with
a square hole in each to fit the spindle. The solid ends
are cut out of inch deal, and are used to keep the skele-
ton firm and in a central position when the spindle is
turning op. its bearings. One of the ends is fixed to

MISCELLANEOUS MATTERS 269

flange of the spindle with screws. If a case column^ is
being made, the solid ends are taken off before the col-
umn is cut ; but they form permanent parts of the fram-
ing for an independent column. The mould is fixed at
one side, and level with the centre of the spindle, which
is the centre of the column's diameter. Care must be
taken that the profile of the mould plate to the centre
of the spindle is one-half of the required diameter at
each end of the shaft.

Vases are generally made without wood framing. They
are turned on a spindle with a plaster core screwed to the
flange in the form of a parabola, to give the form of the
hollow inside. On the core a coat of scag is laid and al-
lowed to set. This is scratched to give a key for the
coarse plaster which forms the body of the vase. This
is formed to the desired outer profile by means of a
mould fixed on the outside, and muflBed to allow for a
tliickness of outside scag. When the core is run, the
muffle is taken off, and the scag laid, keeping it about %
inch thicker than the true profile, to allow for turning
and stoning. When the scag is set, it is turned, and
then the vase is taken off the spindle and plaster core.
The spindle hole is used as a key for a slate or iron dowel
for fixing the vase on to the square plinth. The vase is
then polished. Cheap work is usually run or turned
with a mould. This is done to save turning with chisels,
but it spoils the true figure of most marbles.

A more recent way of imitating marbles is known by
the name of Marezzo, which does not require so much
polishing, being made on plate glass or other smooth
surface. Keen's superfine plaster is used. The mode
of making Marezzo is described later on. Specimens of
the real marbles, to give the color and form of veining,

270 CEMENTS AND CONCRETES

spots, and figures, will be of great service to the be-
ginner.

Mixing. — ^Mixing the colors is ap. important part of
scagliola manufacture, and the following colors, mixing
and mode of using, will serve as an index for the imi-
tating of any other marble that is not detailed. Fine
plaster (not cement) is used for making the best class
of scagliola, gauged with sized water, which is made by
dissolving 1 lb. of best glue with 7 quarts of water. (This
is known in the trade as ** strong water".) The stuff,
when gauged will take about six hours to set. All mix-
ing is done on a clean marble or slate slab. One of the
principal arts is the mixing, but there are no two men
who mix exactly alike, and^ it is largely a matter of ex-
perience. The chopping or cutting into slices with a
knife is another important point in the mixing, apart
of course from the special colors. Where there are two
shades of one color in* any given work, the cutting does
not affect their original shade. No dry color is used,
only ground water-colors. The beginner had better ex-
periment with a small sample of ''Penzatti" or Pen-
zance marble. With one gill of size water, gauge plaster
middling stiff, then mix thoroughly with the gauged
plaster a little red. Do the same with a little black.
(See quantities below.) Blend this stuff properly by
working it on the bench with the hands (not tools), then
roll it out, and cut it into slices about one inch thick.
Take up these slices, and part them with the fingers
about the size of a walnut, and put them aside, a little
distance apart, on a bench.

The veining in this instance is white. Over these little
lumps scatter half a handful of crumbs, made by re-
serving a little of the gauged plaster, and making it
crumbly with dry plaster, mixing with it a few small

MISCELLANEOUS MATTERS 271

bits of alabaster or marble. Then gauge a little plaster
in a basin, with a tooth brush, about 2 inches wide, dip
into this gauged plaster, and smudge the little lumps all
over with it. Knock these lumps together into a big one,
and chop the big lump three times. (This chopping
means cutting with a knife into slices once, and knock-
ing up again ; cutting with a knife a second time, and
knocking up again ; and then cutting with a knife a third
time, when it is finished.) This lump is then ready to
be cut into ^slices, and applied to any purpose required ;
but in this case, being wanted for a specimen, it is cut
into slices about % inch thick, and laid close together
flat on a sheet of paper, and allowed to remain until set.
It is then planed, and when dry polished. This opera-
tion is an embodiment of the principle of **scag" mix-
ing nearly from beginning to end, only submitting on«
color for another for the various marbles. The mixing
is generally known as plain and rich, and may be
described thus: Take a Sienna pedestal, for instance'.
Two shades of sienna, plain mixing; one or two shades
of dark with veining, rich mixing, both done on the same
pi^inciple as Penzatti. They are cut into slices and laid
on alternately. AH veining of any color is done as
described above, only modified by the consideration that
if strong veining is wanted the stuff must be stiffish, and
for fine veining it must be slightly softer. Various-sized
measures for the water and scales for weighing the color
should be used. * Pats of each gauge should be set aside
as test pats to determine when the main portion of stuff
is set. It is advisable to number the pats for future
reference as to quantity of colors, time of setting, and
tints when dry. The various colors and tints are gauged
and chopped as previously described, and according to
the marble required. The core being laid on the skele-

272 CEMENTS AND CONCRETES

ton, and left in a keyed and rough state until dry and
expansion ceased, it is ready when set for the seag. The
core is now damped and well brushed with the white or
other vein that has to be made. The veining is gauged
thin, and being brushed and laid in the core, will tend to
make the slices adhere better, and fill up the interstices
caused by the jagged edges of the cut slices. The slices
are then taken and pressed firmly onto the core, arrang-
ing in proportion to the figure of the marble. To render
the work more dense, beat it with a flat-faced mallet
and a large gauging trowel with a square end. Try the
work with a rule to see if the surface is fair. The
rough surface should not be' less than % inch thicker
than the true line of the work, to allow for planing and
stoning. When required, pieces of alabaster are inserted
before the stuff is set. Metallic ores are used in
some marbles, also pieces of granite and real
marble. When the scag is laid, the work is left until
set and dry. It is then planed stopped, stoned and
polished. Columns and circular work are turned on a
lathe, and the rough surface reduced to the true profile
with long chisels similar to those for. turning wood or
other materials. This should not be attempted until the
materials are thoroughly set.

Colors and Quantities, — The following are the colors
and quantities used for various marbles. The propor-
tions of strong water, which is made varies, the due
quantity should be tested by gauging small pats of
plaster to ascertain the time of setting. As the tints of
real marble vary in some species, the mixing must to
some extent be left to the ingenuity of the workman.
With a little practice and perseverance, a careful and
observant man will soon succeed in getting the required
tints.

MISCELLANEOUS MATTERS 273

Penzance Marble, — 10 oz. of light purple brown to 1
pint. Veining (plain mixing), 2 oz. black to 1 gill; vein-
ing (rich mixing) 5 oz. black to ^ pint; veining (rich
mixing), 1 oz. black to ^ gill. All liquid measurements
refer to strong water.

Egyptian Green, — 5 oz. black to 1 pint. Veining, ^/^ oz.
green to ^ pint light shade; veining, ^ oz. green to ^
gill. White the same, black chopped three times ; a few
black spots same as brown Beige.

Brown Beige, — ^Four shades — 1 light purple brown
(indigo); 2 middle shades (blue black); 1 very dark
shade (vegetable black). Veining, burnt sienna with red
alabaster spots — 4 oz. (light shade) to ^ pint; 4 oz.
(middle) to % pint; 4 oz. (very dark) to ^ pint;
% oz. burnt sienna to ^4 pi^^* ; ^ oz. black to % pint ;
% pint for the grey with crumbs, and red alabaster
spots.

Dark Porphyry, — Color, light purple brown, with
black, and a little ultramarine, blue spots, black, ver-
milion grey, and a little red.

Green Genoa, — 214 oz. green to ^ pint (rich mix-
iag) ; 5 oz. black to 1 pint. Veining, ^ oz. green to %,
pint. White veining the same, with alabaster spots, and
black.

Rouge Boyale, — Color, light purple brown, with a little
sienna, and umber, with ultramarine, blue or blue black.
Vert- Vert. — ^ ozw green to ^ pint; dark green with
sienna; dry green plaster.

Devonshire Bed Marble. — ^All sienna work. Light
mixing — 1 shade grey; 1 shade lemon chrome; 1 shade
light purple brown; 1 shade flesh color; veining burnt
sienna. Dark mixing a — 1 shade light purple brown,
with indigo blue in it; 1 shade dark purple brown; 1
shade middling purple brown; 1 shade grey; 1 shade

S74 CEMENTS AND CONCRETES

lemon chrome. Veining, burnt sienna, with small ala-
baster spots.

Sienna Mixing. — 5 oz. sienna to ^ pint, dark shade;
3 oz. sienna to % pint, middle shade; 2 oz. sienna to
y2 pint, light shade.

Griotte Marble. — 10 oz. of light purple brown to 1
pint 5 oz. of dark purple brown to % pint, with ala-
baster spots. Ground with red veins, and small spots.

Spanish Buff. — Burnt sienna, 2 shades, with large ala-
baster spots. Veining, white and blue black, with small
alabaster spots. Ground with red veins, and blue spots.

Light Verd Antique. — 2% oz. green to V^ pint;
iy2 oz. black to 1 gill ; i/^ gill black to 1 gill grey shade.

Dark Verd Antique. — Green spots cut; grey spots cut ;
black spots with green and grey. Veining 2^^ oz. green
to ^ pint (rich mixing) ; 2^^ oz. dark green to i/^ pint
(rich mixing) ; ^ oz. black to ^ pint (rich mixing).

Plain mixing, same as above, with small alabaster
spots, and small black spots.

Black and Gold. — 5 oz. of black to 1 pint. Veining,

2 shades dark sienna to i/^ pint (rich mixing) ; 2 shades
light to % pint (rich mixing) ; 2 parts light and grey,
with alabaster spots, and crumbs. Veining must be stiff;

3 oz. of black to 1 gill.

Walnut. — 2 parts burnt umber; 1 part rose pink.

Verta Alps Marble. — 5 oz. black to 1 pint. Veining,
11/4 oz. of green to II/2 gills ; 1/4 oz. green to y2 gill, with
black crumbs chopped three times for the ground.

Rosse De La Vantz Marble. — Rich mixing with indi-
go blue — 1 shade light purple brown ; 1 shade dark pur-
ple brown; 1 shade Veneti?in red. Veining, black for
the ground, and white and green veining for the mixing,
with alabaster spots and crumbs.

MISCELLANEOUS MATTERS 275

Polishing White Scagliola, — ^White scagliola is often
made with superfine Keen's cement. A small portion of
mineral green or ultramarine blue is added to improve
and indurate the white color. White work requires spe-
cial care to prevent discoloration or specks. When the
work is left for drying purposes, or at the end of the day,
it should be covered up with clean cotton cloths to pre-
vent the ingress of dust, smoke or being touched with
dirty hands. The tools should be bright and clean. Steel
tools should be as sparingly used as possible. When the
cement has thoroughly set and the work is hard^ it is
rubbed down with pumice-stone, or finely grained grit-
stone, by the aid of a sponge and clean water, rubbing
lightly and evenly until the surface is perfectly true. It
is then stoned with snake-water (Water of Ayr), using
the sponge freely and the water sparingly until all the
scratches disappear. Afterwards well sponge the sur-
face until free from glue and moisture. It is now ready
for thfe first stopping. Stopping is an imiportant part of
the polishing process, and should be carefully and well
Jone, to ensure a good, sound, and durable polish.

First gauge a sufficient quantity of cement and clean
water in a clean earthenware gauge-pot. The gauged
stuff should be about the consistency of thick cream. It
is well dubbed in, and brushed into and over the surface,
taking care that no holes or blubs are left. When the
stuff on the face gets a little stiff, scrape off the super-
fluous stopping with a hard-wood scraper having a sharp
edge. Then repeat the brushing (but not the dubbing)
with the soft gauged stuff, and scraping two or three
times, or until the surface is solid and sound. The work
is now left until the cement is perfectly set. It is then
istoned again for the third time with a piece of fine snake-
gtone, and stopped as before, with the exception that the

276 CEMENTS AND CONCRETES

superfine stopping is not scraped off, but wiped off with
soft clean rags. The work is left until the cement is set
and the surface dry. It is then polished with putty
powder (oxide of tin), which is rubbed over the surface
with soft clean white rags, damped with clean water. In
polishing mouldings, the stone must be cut or filed to fit
each separate member of the moulding.

Polishing Scagliola. — The polishing of scagliola is
slightly different. It is rubbed down with a soft seconds
(marble grit) or gritty stone, using the sponge and water
freely until the surface is true. The glut and glue are
cleaned off with a brush and sponge, using plenty of
water, until the pores are free from grit. The moisture
is sponged off, and the work left until suflSciently dry.
It is then stopped in the -same manner as white work, but
using stiff stopping for large holes and steel scrapers in-
stead of wood. The stopping is made with the same
kind of plaster, size water, and color as was used for
the ground color of the ^marble that is being imitated.
The stopping and stoning is repeated as before, and it is
finally polished with putty powder, using pure linseed oil
instead of water. The repeated operations of stopping
and stoning must not be proceeded with until the
previous stopping is perfectly set, and the work dry. A
small portion of spirits of turpentine is sometimes added
to the gauged colored stuff to facilitate the drying. The
work between each combined stopping and stoning will
take from one to five days to dry, according to the size
and thickness of the work and the state of the atmos-
phere. Never dry the work by heat. The thorough dry-
ness and hardness of the work are most essential be-
fore proceeding to polish with the putty powder and lin*
seed oil, because any contained damp will work out and
spoil the polish. Work not perfectly dry may take a

MISCELLANEOUS MATTERS 277

high polish, but it will soon go oflf when the damp comes
through. Columns or large hollow work are not so liable
to be affected by the damp, as it may escape through the
back; but there must be some opening or ventilation to
allow it to finally escape.

If the polishing is well and carefully done, the polish,
produced on scagliola will equal, if not surpass, that on
real marble. Tripoli polishing stone, sometimes called
alana, is a kind of chalk of a yellowish-grey color. Water
of Ayr stone is also used for polishing. In large work
a rubber of felt dipped in putty powder may be used.
Salad oil is sometimes used for finishing. Linseed oil
makes the hardest finish, and dries quicker.

Marezzo, — Marezzo artificial marble manufactured
from plaster or Keen's cement and mineral coloring mat-
ter is made in wood or plaster moulds for moulded work,
and on slate or glass benches if in slabs. If thick plate
glass is used, the worker has the advantage of being able
to look through it to see if the figure of the work re-
quires altering. Glass also has the advantage of leaving
a smoother and more polished face. All wood and
plaster moulds should be got up with a good face, and
properly seasoned, to save stoning and polishing the face
of the work. Keen's cement may be used advantageous-
ly in making Marezzo, especially for chimney pieces, or
other works required for exposed positions. Keen's
cement for Marezzo should be of the highest class. If
the cement is not of the best, it will effloresce, rendering
the work of polishing difficult, if not spoiliug it alto-
gether. Keen's cement requires no size water, but in
gauging either Keen's or plaster, no more should be
ganged than can be conveniently used. The quantities
of colors. Keen's cement, plaster, and size water should
be measured and gauged pats kept for future reference.

278 CEMENTS AND CONCRETES

All gauge-pots snould be of earthenware, as they are-
more easily cleaned out, and do not rust, as is the case
with metal pots. All the tools should be kept bright and
clean, as when working scagliola.

Marezzo is made in the reverse way to scagliola, as the
face or marble is put in the mould first, and the core or
backing put on afterwards.

All the mineral colors should be of good quality, in
fine powder, and ground in water, known as **pulp.'' A
number of basins should be handy, and there should be
a supply of twist silk in skeins varying in diameter f ronoi
% to ^ of an inch, and cut into lengths of 14 to 18
inches. For common work, good long flax fibre may be
used. Canvas is also required. One end of the silk or
fibre skein must be knotted. These are known as **drop
threads."

After the moulds are made, seasoned, and oiled, the
young hand may begin by trying to make some easy
marble^ for a slab or chimney-piece. Gauge Keen's extra
superfine cement or superfine plaster, in a large basin
labelled No. 1, well mixing it until about the consistency
of cream. This is pure' white. Now pour a small quan-
tity of this white plup into two small -gauge-pots, Nos.
3 and 4. Pour a third of what remains in the No. 1
pot into another gauge pot. No. 2. Take some black-
colored pulp, and make No. 1 a blackish-grey. Color
in the same way No 2. only very much blacker than
isTo. 1. No. 3 is now slightly tinted with pulp f rom« No,
1. This leaves No. 4 pure white. Then take a skein of
twist (or threads), dip into No. 4, the pure white, and
well charge it by stirring it about with the fingers ; take
out the threads, taking each end between the thumb and
forefinger of each hand, and with the remaining fingers
of each hand separate the threads, allowing plenty of

MISCELLANEOUS MATTERS 279

**swrjg," and strike this into the face of the mould, mak-
ing each stroke at different angles, recharging the
threads when necessary. Repeat this process with pulp
from No. 3, but in a lesser quantity; then dip your
finger ends into No. 2, and fling drops about the size of
large peas all over the veining. These drops must be
throirn on with considerable force, so as to cut into the
"veing as much as possible. Dip the fingers into No.
1, and throw on No. 2, using alternately from each gauge-
pot until you get a uniform thickness of surface (scag),
about Ys inchr in thickness. Now run a trowel over this
to lay down any ridges. Cover the work with; a piece
of canvas, laying it evenly, smoothly, and without
wrinkles. Be careful to put the Canvas in the proper
place, as moving it would spoil the lines of the veining;
then spread a quantity of dry coarse Keen's lightly over
the entire surface. This will absorb any superfluous
moisture through the canvas. After the canvas and
coarse Keen's have lain from ten to twenty minutes, or
according to the stiffness of the gauge of the marble, the
canvas and coarse cement are easily lifted off.^ Should
any portion of the face of the scag leave the mould, and
adhere to the canvas, it is taken off and put back in
its place in the mould. The whole surface is now
trowelled to render it dense and hard. The moisture
should be sufficiently absorbed, or the trowelling may
spoil the figure. The proper absorption of the moisture
by the dry cement through the canvas, and well trowel-
ling, are most essential to good work, ensuring hardness
and density.

The core or backing is now made by using the coarse
Keen's previously used for absorbing the moisture from
the face, gauging it with some fresh coarse Keen's as
stiff as possible. This is laid on as thick as required. Ijf

280 CEMENTS AND CONCRETES

the face of the seag be very dry, spread a thin coarse
gauged Keen's, so as to give a perfect cohesion between
the marble and the backing. The flat surface of the
backing should always be ruled or floated straight with
a uniform thickness, so as to give a true bed for the cast
when it is taken out of the mould, and laid on a bench
ready for stoning, stopping, and polishing. This can.
be done as soon as it is thoroughly set and bard, and in
the same manner as scagliola.

Marbles having long stringy veins require a different
method of putting in the veins. Take the skeins, or
** threads," by the knot with one hand, and thoroughly
saturate them with the veining mixture, and run the
finger and thumb of the other hand down the threads
to clear them of any excess of veining color with which
they may be charged. Then give the end not knotted to
your partner, holding the knot in your left hand. Pull
the threads asunder, so as to take the form of the veins
of the marble you are copying, then lay them in the
mould, leaving the knots hanging over the edge of the
mould, or at least visible, to facilitate their removal
when required. The threads should be arranged on the
mould so as to take the form of the veining. The other
colored materials are then thrown upon the thread veins,
which quickly absorb the coloring matter from them;
care being taken that the various colors are thrown or
dropped from the finger tips, to form the figure of the
body of the marble that is being copied. When the
mould is sufficiently and properly covered with the
marbling, take hold of the knots and withdraw the
threads. These should be cleaned by passing down the
finger and thumb for future use, saving the superfluous
stuff for filling up any holes in the marbling. The
iibsorption of the use of canvas and dry coarse Keen's,

MISCELLANEOUS MATTERS 281

and the filling in of the^ backing or core, is then
proceeded with as before described.

Granites, porphyries, etc., are made in a different
manner. For porphyries with white and black specks,
make a slab of white Keen's about Yg inch thick, and
another in black, tbje same thickness. When they are
set and hard, chop them into small pieces, then run them
through a sieve, having a mesh to let through the pieces
of the required size only. The pieces retained in the
sieve can be broken and sieved again. The whole is
now sieved again through a smaller mesh, which de-
tains only the size wanted. The refuse can be used for
small work or backing up. When the gauged stuff for
the facing is mixed of the required tint (a reddish-
brown), damp the black and white specks with the
gauged color by means of a trowel and rolling, care
being taken not to break the edges and faces of the
black and white specks. When it is well mixed, lay it
onto the face of the mould about 3-16 inch thick, press-
ing it as firmly and evenly as possible. Then absorb the
moisture by means of canvas and dry coarse Keen's,
trowel it well to give density, and fill in the backing or
core as before. For ** Rouge Royale,'' **Verd Antique,''
&c., requiring large white patches of irregular size, the
sieving can be dispensed with. The white pieces are
broken haphazard, and pieces of alabaster can also be
inserted in these, and many other marbles, due regard
being given to the size and quantity, so as not to produce
an unnatural effect. The remainder of the figure is
formed with the **drop threads," and the other colors
being thrown on.

From this description of Marezzo, the workman will
understand that in the case of marbles classed as ^'Brec*
cias,'' such as '*Editge Royale," ** Black and Gtold," &c..

282 CEMENTS AND CONGRETES

having patches and rough jagged veins in them, he must
have flat pieces of the required color previously made
and broken up, or alabaster, as the case may be inserted
into them, and the veining done with the **drop threads''
and that fine or long veining threads are not required;
that unicolored marbles require no veining threads ; that
the long veined marbles require the long threads, and in
eome cases the **drop threads" as well, and that granites,
porphyries, &c., require no threads; that black is diffi-
cult to make owing to the pure white cement requiring so
much color; and finally, that in all cases, whether Ma-
rezzo or scagliola, the polishing is done in a similar man-
ner, whether using plaster or Keen's cement.

The details given must be carefully followed to pro-
duce work artistic in figure and appearance. The direc-
tions for making **St. Ann's" so far as manipulation is
concerned, apply to all others. A little patience, prac-
tice, and perseverance will soon give confidence and ex-
pertness in producing sound scagliola and Marezzo.

Granite Finish. — Granite is a peculiar finishing coat of
plaster which is sometimes used in this country to imi-
tate granite, ^or granite finish, first render the walls
with hydraulic lime, and when nearly dry lay with a thin
coat of the same material but colored light brown. Then
while this coat is still moist, splash the surface lightly
with white stuff, then with black stuff, using only half
Bs much as used for the white stuff. The red stuff is
best applied by dotting the surface with a small brush
charged with the colored stuff. After these colored lime
stuffs are firm, but not set, the surface is carefully trow-
elled, using the minimum of water so as not to mix the
various colored stuffs. The surface is sometimes left in a
rough state, or as left when splashed. After the surface

MISCELLANEOUS MATTERS 283

is firm, it is set out and jointed to represent blocks of
graite. - '

Granite Plastering, — Granite plastering is a method,
introduced by the author, to imitate granite. This mode
of imitating granite is based on the scagliola process. It
is also somewhat similar to the granite finish, and gives
better and more reliable results.

The method of executing granite plaster work is as
follows: First select the most suitable lime or cement
for the situation, such as Portland cement or hydraulic
lime for exterior work, and Parian or othei^ white cement
for interior work. Having decided on the material,
gauge three different colored batches, one white, one red,
and one black, taking care that the stuff is gauged stitf
and expeditiously so as to obtain a hard substance. The
material is colored to the desired shades, as described
for scagliola or colored stuccos. When gauged the stuffs
are laid separately on a bench and rolled until about
3-16 inch thick, and when nearly set they are cut into
smaU irregular cubes and allowed to set and harden. The
wall is then floated, ruled fair, and the surface keyed,
and when set it is laid with a thin bedding coat of simi-
lar stuff used for the floating, but colored light brown.
The colored cubes are then mixed together in due propor-
tions, and gauged with a portion of the light bro^vn col-
ored stuff and laid on the thin coat while it is soft. The
whole is then firmly pressed with a hand-float until a
close, compact, and straight surface is obtained, taking
care when pressing the^ stuff not to break the cubes.
After the stuff is set and perfectly dry and hard, the
surface is rubbed down and polished, as described for
scagliola or for marble plaster. The bedding coat should
be sufficiently thick to receive the colored cubes, other-
wise the larger cubes will project at parts, and cause

' fc

284

CEMENTS AND CONCRETES

extra labor in making a uniform and straight surface.
Unless the cubes are fairly level when pressed, the sur-
face will have a spotty appearance, besides being more
difficult to polish. Where expense or time is a consid-
eration, a striking appearance is obtained at less cost
than polished work, by simply finishing the surf ace with
a cross-grained 'hand-float, and a semi-polished surface is
obtained by trowelling, or by scraping the surface with
a joint-rule. Grey or light-colored granites are imitated
by altering the colors of the cubes and the bedding coat
as desired. Bold and striking effects on wall surfaces
can be obtained by a combination of different colored
granites, laid out in bands and borders. The effect can
be increased by the introduction of borders in sgraffito*
with the bands in granite plaster.

PART II

CEMENTS AND CONCRETES, AND HOW TO USB

THEM.

It is not necessary to the workman that he should ex-
pend a long period of his valuable time in reading up
the history of cements and concretes, nevertheless it is
proper he should be acquainted with the outlines of the
origin, growth, and development of cements, concretes
and their uses, and to this end the following brief his-
torical summary is presented, sufficient to give the work-
man a fair idea of the beginning and growth of the use
of cements and concretes:

The word concrete is of Latin origin, and signifies a
mass of materials bound or held together by a cementing
matrix. The Romaas used concrete B. C. 500. They
made good use of lime concrete both in the construction
of buildings and roadways. ** Roads,'' says Gibbon,
**were the most important element in the civilization
of ancient Rome ; and the cost of the Appian Way was
such as to entitle it to the proud designation of *Re-
gina Viarum' (the Queen of Roads).'' The Appian
(the oldest of the Roman highways) was commenced by
Appius Claudius Caius, when he was censor, about three
centuries before the birth of Christ. It extended from
Rome to Capua, whence it was consequently carried on
to Tarentum and Brundusium. Antonio Nibby, an
archaeologist of the highest authority, states that the
Appian Way had an admirable substructure, with lime
concrete materials superimposed, and large hexagonal

285

286 CEMENTS AND CONCRETES

blocks of stone laid on the top of all. The Romans built
concrete aqueducts, often several miles long, to convey
water to the cities. T}ie palace of Sallust, the historian,
was built about B. C. 50, and was frequently used as a
residence by most of the emperors until as late as the
fourth century. It was partly burnt by Alaric in the
year 410. Tliis once magnificent edifice was erected on
jt strange site, partly in the valley at the foot of the
Quirinal Hill, and partly on the top of the hill. Th«
' latter portion of the palace, which was of great extent,
has been almost wholly destroyed by the builders of the
inodem boulevard. The walls, which were thick and
.high, were most valuable examples of the Roman use of
. concrete, unf aced by brick or stone. There is still visi-
ble evidence, in the form of impressions left on those
walls, which clearly demonstrates their method of cast-
ing walls in situ by means of wood framing. Rows of
timber uprights, about 10 feet high, 6 inches wide, and
3 inches thick, were fixed along both faces of the in-
tended wall. Boards about 10 inches wide and 1%
inches thick, in suitable lengths, were then nailed hori-
zontally along the^ uprights, thus forming two parallel
wooden walls, into which the concrete was laid and
rammed until the space between the boards was filled
to the top. When the concrete had set, the wood fram-
ing was removed, and refixed at the top of the concrete,
the whole process being repeated until the wall was
raised to the required height. This concrete was far
more durable than brick or stone. The jerry-builders of
the modern Rome had no difficulty in pulling down the
stone wall of Servius, but the concrete walls required tjxe
use of dynamite to complete their destruction. After
withstanding the wear and tear of many centuries, and
the repeated onslaughts of the Goths and Vandals, it was

HOW TO USE THEM 287

left to the nineteenth-century speculative builder to de-
stroy those interesting remains.

The use of concrete for floors and roofs is of great an-
tiquity. It was employed for this purpose by the Ro-
mans in the time of Julius Caesar. Professor Middleton,
in his first book, ** Ancient Rome," states that the whole
of the upper floor of the Antrium Vesta is formed of a
great slab of concrete, 14 inches thick, and about 20 feet
in span, merely supported by its edges on travertine cor-
bels, and having no intermediate supports. In his sec-
ond book, '^The Remains of Ancient Rome,'* Professor
Middleton mentions that the Romans used concrete for
the construction of the Pantheon, which was erected
about the time of Christ. A curious and apparently un-
accountable feature as regards practical purposes is 'that
the concrete is faced with bricks, which were faced again
either with stucco or (in special cases) with marble
veneer. The Professor ^ves a sketch showing the ex-
terior facing and the section of a wall of this kind, the
entire mass being composed of concrete, except a facing
of thin bricks, triangular in plan, with the points in-
wards. As the author observes, these bricks could not
possibly be intended as a matrix for concrete, as it would
not have withstood the pressure of the latter while in a
wet state. It must therefore have been necessary to re-
tain the brick and the concrete with an external tim*
ber framing, as in the case of unfaced concrete. There
could be no gain of strength or other benefit to compen-
sate for the time expended setting the brick skin. The
dome of the Pantheon is 142 feet in diameter and 143
feet high. This is also formed with brick-faced concrete!.
It has often been described and even drawn by various
authors as essentially a brick dome. Professor Middle-
ton remarks there must have been very elaborate con-

288 CEMENTS AND CONCRETES

fitruction of centring for this and other massive concrete
vaults. He states they employed, a method, which has
become common of late, to avoid the necessity of build-
ing up the centring from the ground. They set back
the springing of the arch from the face of the pier, so
as to leave a ledge from which the centring was built,
the line of the pier being afterwards carried up until it
met the intrados of the arch, leaving it a segmental one.
The Professor also found signs of timber framing for
walls in the remains of the Golden House of Nero, un-
der the Thermae of Titus, where, he says, **the chan-
nels formed by the upright posts are clearly visible.
These upright grooves on the face of the wall are about
6 inches wide by 4 inches deep, and they are afterwards,
filled up by the insertion of little rectangular bricks, so
as to make a smooth unbroken surface for the plaster-
ing.'' This method is difficult to understand. Accord-
ing to the present practice, the supports should be fixed
outside the line of wall surface and leave no space to
fill in afterwards. He also mentions a striking example
of the tenacity of good concrete in the Thermae of Cara-
calla, at a part where a brick-faced concrete wall origin-
ally rested on a marble entablature supported by two
granite columns. **In the sixteenth century," he says,
**the columns and the marble architrave above them were
removed for use in other buildings, and yet the wall
above remains, hanging like a curtain from the concrete
wall overhead. ' ' This proves that the Romans bestowed
as much thought and care on the materials and their
composition as they did on their construction. Profes*
sor Middleton notes that the larger pieces of aggregate in
the concrete, which are not close together, are so evenly
spaced apart as to lead to the conclusion that they must
have been put in by hand, piece by piece.

HOW TO USE THEM 289

Dr. Le Plongeon, during his explorations in Peru,
found many remains of mud concrete walls. Although,
they i were built many centuries ago, they have proved
sufficiently durable to exiiit until to-day. The materials
were placed between two rows of boards, and well beat-
en, and the exteriors were sometimes decorated with plas-
ter work. Thus it appears that the Peruvian builders of
the period of the Incas anticipated by centuries the
method, (but not the material) of our modern concrete
buildings. Le Plongeon 's researches conclusively estab-
lish the fact that these Indians were masters of concrete
building and plastering. The walls of the fortress of
Ciudad Rodrigo in Spain are built of concrete. There
are over twelve miles of arches and tunnels constructed
with concrete in the Varone Aqueduct, which supplies
Paris with water. One of the arches over the Orleans
Eoad, in the Forest of Fontainel^eau, has a span of 125
feet, without a joint, the arches and the water-pipe or
tunnel being entirely composed of beton, njade with
Portland cement, hydraulic lime, and the sand found on
the spot. Con<;rete blocks weighing over 20 tons were
used in the construction of the ^uez Canal, 3,000,000
tons of these blocks being required at Port Said alone".
Besides the unquestionable durability of concrete, it also
possesses fire-resisting and waterproof powers of the
highest degree. Constructional works formed with con-
crete carefully made and applied may be considered ab-
solutely fire-resisting and damp proof; in fact, in these
respects concrete has long since passed the experimental
period, inasmuch as numerous tests, under the most try-
ing and adverse circumstances^ attest the superiority of
this material for sanitary and durable work.

The best concrete in France is that made under Coign-
et's system of ** beton agglomere,'* and has been used

290 CEMENTS AND CONCRETES

with great success in the construction of yarious large
and important works. In Paris many miles of the sew-
ers have been formed of this material, and a church in
the Gothic style, from the foundations to the top of the
steeple (which is 136 feet high) is entirely formed of
beton. -The work was prosecuted without cessation for
two years, and was exposed to rain and frost, but has not
suffered in the slightest way from the extremes of tem-
perature. The strength of this material for constructive
work may be judged by the thickness, or rather want of
thiekness, in the construction of a house, six stories high,
having a Mansard roof — cellar, 19 inches, first story, 15
inches; second story, 13 inches, and diminishing 1 inch
every successive story, so that the sixth story was 9
inches. The cellars have a middle wall from back to
front, from which spring flat arches having a rise of one-
tenth of the span, th% crown being 5 inches thick, and
at the springing 9 inches, which formed strong damp-
proof and fireproof cellars. There are many houses in
Paris, and this country, constructed of this material. It
has been used in London in the construction of sewers,
&c. This concrete is composed of Portland cement,
sand, and lime. Hydraulic lime is used for sewers and
waterworks, and common lime for ordinary work. The
lime is used in a powdered state. The whole of the ma-
terials are mixed in a dry state by hand, and afterwards
gauged in a specially made pug-mill. The least possible
amount of water is added by means of a fine jet while the
pug-mill is in motion. The mixture is then spread in
thin layers, and beaten by rammers formed of hardwood.
The quantities for coarse work, where a fine face is not
required, are: Portland cement, 1 part; common lime,
% part; gravel, 13 parts; coarse and fine sand, 6 parts.
And for sewers : Portland cement, 1-5 part ; hydrattUc

HOW TO USE THEM 291

Kme, 1 part; sand, 6 parts. And for external work of
^ood quality: Portland cement, 1 part; lime, % part;
sand, 7 parts. The above proportions are all by measr
Tire. Specimens of Coignet beton at two years old have
attained a crushing strength of 7,400 lbs. to the square
inch.

Fine Concrete, — ' * No book pn plastering, " says Miller,
** would be complete without a description of the meth^
cds for working 'fine concrete' (here termed *fine con-
crete' to distinguish it from rough concrete as used for
foundations, &c.), which is now coming into general use
for paving purposes, staircases, and constructive and
decorative works for buildings. Floors, roofs and simi-
lar works which are finished with fine concrete, being
within the plasterer's province, also demand description.
The proper manipulation of the plastic materials, which
is imperative for sound concrete, is undoubtedly plaster-
er's work. The higher branches of concrete work, for
architectural construction and decoration, embrace
model-making, modelling, piece-molding and casting.
Concrete construction is therefore essentially a part and
parcel of the plasterer s art and craft. The construc-
tion of concrete staircases in situ affords a striking ex-
ample of the necessity of employing plasterers. Only a
plasterer can manipulate the materials correctly, make
the nosing mitres sharp and true, and set the soffits of
the stairs and landings, and form a true arris at the
stringing, whereas the non-plasterer leaves the work un-
even, rough and unsound. The non-plasterer can just
manage to spread the stuff laid on the ground for him
when laying paving, but he is entirely lost when the
stuff has to be taken up on a hawk and laid with a
trowel on an upright or overhead surface. He then gets
upset, or rather he upsets the stuff. The non-plasterer

292 CEMENTS AND CONCRETES

possibly may have been an unfinished apprentice, or a
dunce at his former trade, hence his trying another.
These remarks are not caused by any hostility to other
trades, but are inspired by the fact that many failures
in the better class of concrete are due to the non-plaster-
er's incapacity in working, and his laclc of knowledge of
the materials. Portland cement concrete pavements were
first used about sixty years ago. Its introduction, im-
provements, and subsequent rapid strides for paving,
and in the construction of staircases, cast and made in
situ, are due to the plasterers. Concrete is one of the
best materials for paving the sidewalks of streets, abat-
toirs, stables, breweries, &c. It is jcintless, impervious,
non-slippery, and can be laid with a plain surface or
grooved to any desired form. The only objection to
paving laid in situ for streets is that when it is cut to
repair or alter gas or water pipes it is difficult to make
it good without the patches showing. This slight defect
can easily be overcome by cutting out the whole bay
where the patches are, or by forming a movable slab
over the pipes.

There has been in recent years some controversy as
to the department of the building trades to which lay-
ing concrete paving properly belongs. The claim is un-
doubtedly upheld in the strongest way for the plaster-
ers. A further argument, if one is needed, to identify
the operation as a plasterer's job, is that the tools, skill
in which is necessary, are exclusively those of plaster-
ers. The laying trowel and the hand-float are prin-
cipally used, and none but plasterers exclusively employ
them, no other workman in any branch of the building:
trades being habituated to their use. In every part of
the world where <Joncrete paving has been used it has

HOW TO USE THEM -293

been laid down by plj^sterers, so that it may be looked
upon as their legitimate sphere of work.

Concrete is now extensively used in preference to
earthenware for making sewer tubes. Experience has
proved that the acids present in liquid sewage and the
gases generated by the action of a faecal decomposition
do not injure the concrete tubes, but on the contrary tend
to harden them. Among the many unlikely purposes for
which concrete has come into use may be mentioned stat-
uary, vases, fountains, sinks, tanks, cisterps, cattle-
troughs, silos, railway sleepers, platform copings, man-
telpiecesj chimney pots, tall chimneys, tombs, tombstones,'
and coflSns. Concrete is slowly but surely coming to the
front as one of the most useful, economical, constructive,
and decorative materials for works requiring strength
and endurance. It may now be said to be indispensable
to the architect, engineer ai^d builder. Concrete, when
properly made with a Portland cement matrix, and slag
or a similar aggregate, is undoubtedly the best fire-proof
material used in any building construction. It can be
made thoroughly waterproof and acid proof, and may be
moulded or carved to any design and colored to any
shade. After this brief historical review of concrete, the
practical considerations of the modem working by plas-
terers claim attention. Before describing the methods
of working the concrete, a description of the materials,
with their characteristics and application, is given as a
preliminary guide and reference.

Matrix. — ^Matrix is a word used to designate any ma-
terial having a setting, binding, or cementing power,
such as limes, plaster or cements. For concrete paving,
stairs, floors, or cast work for external purposes, it may
be truly said that there is only one matrix, namely, Port-
land cement.

294 CEMENTS AND CONCRETES

Aggregate, — This is a term applied to those materials
held or bound together by the matrix. Aggregates may
be fibrous or non-fibrous, natural or artificial. The nat-
ural aggregates comprise granite, stone, shells, marble,
slate, gravel, sand, metal^filings, &c. ; the artificial slag,
brick, pottery, scharflf, clinkers, coke-breeze, ashes, glass,
&c.; and the fibrous slag, wool, -coir, fibre, reeds, hair,
cork, tow, chopped^hay, straw, shavings, &c. The fibrous
aggregates while being principally of a natural kind, are
generally of a vegetable nature. They are commonly
used with a plaster matrix for the interior works. The
best aggregates for the upper coat of concrete paving
are granite, slag, and some of the hard limestones. The
best and cheapest for the first layer or rough coat are
broken bricks, old gas retorts, clinkers, whin and other
stones. Stone chippings from masons' yards and quar-
ries are cheap and good. Shingles and gravel are also
used, but owing to their round and smooth surfaces they
afford little or no key for the matrix. When found in
large quantities and at a cheap rate, they should be
broken to render them more angujar, so as to give a bet-
ter key. Aggregates are broken by a crushing or stamp-
ing machine. In Paris, the stone aggregates used for
casting figures, vases and similar ornamental works is
generally broken by hand.

Aggregates should be clean, and their surfaces free
from mud and dust. Coarse aggregates are easily
cleaned by turning on a strong stream of water from the
hose. The aggregates should be laid on an inclined plane
to allow the water and dirt to run off. The importance
of a clean aggregate is seen from the fact that briquettes
made from washed particles resist a tensile strain from
15 to 20 per cent, higher than those made from unwashed
particles, wl^en tested under similar conditions.

HOW TO USB THEM 295

Porous Aggregates. — ^AU aggregates of a porous na-
ture or having a great suction should be well wetted
before being gauged, to prevent absorption of the water
used for gauging the matrix. A porous aggregate re-
quires more cement than one of closer texture, and is
not as strong. Water has no power to harden or set an
aggregate. It is used to render the mass plastic, and to
set the cement. No more than is necessary for this pur-
pose should be used. Sloppy cement will not attain the
same degree of hardness as a firm or stifif gauged cement,
consequently it stands to reason that if the water or a
part of it be absorbed by a porous aggregate, it will ren-
der the matrix, or that part next to the aggregate, friable
and worthless. This may be proved by gauging a part
of neat cement and spreading it on a brick and another
part on a slate. It will be found that the latter will set
and become hard, whilst the former will either crumble
before setting, or partly set, without getting hard. All
aggregates are more or less absorbent, but while the por-
ous kinds will absorb the water from the matrix, not
only leaving the portions in immediate contact with the
aggregate inert, but also weakening the whole body of
the concrete, the non-porous have little or no absorption,
water being retained in the matrix, or a portion may lie
on the surface of each particle of aggregate, thus tend-
ing to harden the matrix and increase the general
strength of the coQcrete. It may be thought that these
defects are trivial, and can be overcome by thoroughly
saturating the porous aggregate to prevent suction, but
the fact still remains that after this or other excess water
has dried out, the body of the concrete must still be por-
ous, and this is one, if not the principal reason, why
some concretes are not damp-proof. The quantity of
matrix used for ordinary concrete being very much less

296 CEMENTS AND CONCRETES

than the quantity of aggregate, and the matrix not being
of suflSeient thickness to resist the force of atmospheric
moisture, the damp finds a ready passage through the
porous portions. A mass of porous aggregate will ab-
sorb external moisture, and this will gradually work
through the body to the weakest or driest surface, or be
retained for a time, according to the state of the atmos-
phere. The extra keying power claimed for a porous
aggregate is infinitesimal. It may be said not only to be
of no value, but imnecessary, bearing in mind that in
well-made concrete every particle of aggregate is envel-
oped with matrix.

Another point to be considered is the great tenacity of
Portland cement to most clean surfaces, however smooth.
Many men will- have noticed how it clings and adheres
when set to iron, even to the smooth blades of trowels
and shovels. The ultimate tenacity of neat Portland
cement after being gauged twelve months is about 500
lbs. per square inch.

Compound Aggregates. — The proper selection and use
of aggregates for a true concrete is not secondary, but
of equal importance to the matrix. As inferior aggre-
gates are in the majority, it is advii^able to take their de-
fects into consideration. For concrete floors, roofs, and
stairs, where strength, durability, and fire resisting prop-
erites are imperative, gravel and coke-breeze as aggre-
gates stand lowest in the scale. Owing to their abun-
dance and cheapness, however, or for "want of better ma-
terials, their use is often unavoidable. Their individual
defects may be partly if not wholly corrected by a com-
bination of two or more aggregates so as to balance their
respective good and bad qualities. It is self-evident that
the hard, non-porous, and incombustible nature of gravel
will correct the soft, porous, and combustible nature of

HOW TO USE THEM 297

coke-breeze, and that the light, rough, angular, and elas-
tic nature and variety of size of coke-breeze will counter-
balance the disadvantages of the heavy,* smooth, round,
and rigid nature and uniformity of size of gravel. The
strength, irregularity of size, and form of broken bricks
and its incombustible nature, causes it to be a direct gain
to either of the above. The mixing of various aggre-
gates may seem of small importance, but if by their judi-
cious amalgamation the strength is enhanced, or the
weight or cost of the material decreased, or gained, if the
practice enables any waste or by-product to be utilized,
then the advantage becomes obvious. To argue by
analogy, it is well known that it is by the judicious com-
bination and manipulation of various materials that
mortars and cements attain their strength and hardness,
therefore the same course wift-^ive equally good results
with concretes, while rendering economy with safety pos-
sible.

The compressive and tensile strength of concrete is
influenced both by the matrix and the aggregate. Aggre-
gates which are uniform in size (or if of various sizes
which are not graduated in proportion to each other), or
having their surfaces spherical, soft or dirty, will not
bind with the matrix, or key^op* bend with each other, so
well as those which are of various graduating propor-
tional sizes, and have their surfaces hard, angular and
clean.

Sand and Cement, — Sand is extensively used as an
aggregate in Portland cement for cast work, mouldings,
and wall plastering. Fine sand does not give so good
results for strength as coarse sand, and a hard-grained
sand is more durable than a soft one. Ground brick-
bats or pottery, sandstone and flints, fine gravel, smithy

298 CEMENTS AND CONCRETES

ashes, and coke-breeze are often used as substitutes for
sand.

, It has generally been assumed that sharp coarse sand
is one of the best and strongest for gauging with cement,
but, according to experiments made by Mr, .Grant, clean
sharp pit sand gives better results, as he found that
whereas test briquettes having a sectional area of 2^4
superficial inches, composed of equal proportions of
coarse sand, broke at the end of twelve months with a
tensile strain of 724 lbs., it required 815 lbs. to break
briquettes composed of equal parts of cement and pit
sand. With reference to various sands suitable for mak-
ing mortar with cement, Mr. Grant's experiment is of a
most surprising nature, as it indicates that sand made
from ground clay ballast, or ground brick— which are
identical — and Portland stone dust, were superior to pit
or sea sand, or smiths' ashes.

The following shows the results of tests of various
aggregates made by Lieutenant Innes. The briquettes
are composed of Portland cement, sand, or other aggre-
gates, in the proportions of 1 to 2, and were kept in
water for seven days.

It will be seen that Portland stone dust gave the best
results, and the others follow in this order— coarse sea
sand, rough pit sand, smooth pit sand, drifted sea sand,
and lastly smithy ashes. If the dust had been elimi-
nated, the tests would be more valuable. The degree of
coarseness has a considerable influence on the strength
of the concrete and mortar. Fire sand makes weaker
mortar than coarse. The following table gives the re-
sults of two series of tests carried out by Mr. Grant.
The cement was sifted through a sieve with 2,580 meshes
to the square inch, and was made into briquettes with 2

HOW TO USE THEM

299

I— I

02
Eh

xn.

fl
«

00
«

O
ft
(0

\ p rtOQ

po
o

O OSGQ

u a>

00 « -fl

OQ A

So
o

CO
CO

03
u
bo

03
OP

73
OP

OP
o3 ^

•tH

■§

fCJ OQ

bo ^

2 ^

•» CQ

■ 03 q=l

OQ <0

• IH

•♦H

• f-l
M

OQ •iH

bo"

3 ^

i-i GQ

o 3

OQ ifH

QQ
OQ

bO'-^

t3
a

03
bO

•4A
QQ

o «

s ^

o
Ph

10 '

tH •

rt< CO rH Oi CO r-l

• • • • • _.?

C^ (M O "^ tH t^

10 C^ ""^ CO CO iH

&^
P 03

bo 03

.9^

P bO

P
o

P
O
o

QQ »-•

(U bO

OQ -M

o3 °Q

a «

800

CEMENTS AND CONCRETES

parts of sand by weight. All the briquettes are kept in
water.

Tensile Tests of Poetland Cement and Sand (Coarse

AND Pine).

No.

•

Sand
tested

by
Sieves.

At 28
days.

60
days.

91
days.

182
days.

278
days.

t6i

days.

First Series-^

- Nob.

IbB.

lbs.

1 cement to 8 sand.

20^

78.5

113.9

116.9

142.8

178.

206.5

ditto.

10-20

187.1

239.5

228.

231.5

254.5

251^

1 cement to 8 sand.

20-80

117.2

134.5

145.

156.

167.8

213.

ditto.

10-20

212.

236.5

2fi6.

253.

267.5

278.5

In the above each figure is the average of ten tests,
the result being given in pounds per square inch. The
sand used in tests 1 and 3 passed a sieve with 400 meshes
to the square inch, and the sand used in the tests 2 and
4, through a sieve with 100 meshes to the square inch.

Fireproof Aggregates. — The selection of the best
known fire-resisting aggregate for fire-proof concrete
construction is of vital importance. Granite, stone, and
'flints splinter and crack when subjected to great heat,
or to the sudden reaction caused by cold water used for
extinguishing fires. Coke-breeze concrete, when under
the influence of intense heat, as for example, in the midst
of a building on fire (stated by Captain Shaw to be
from 2000 degrees to 3000 degrees Fahr.), will gradually
calcine and crack, and finally fall to dust.

Slag is one of the best, fire-proof aggregates. It is a
well-worn axiom that **what has passed through the fire

HOW TO USB THEM 301

will stand the fire/' There is no other material that has
passed the ordeal of fire like slag. Its great hardness,
density, and angularity (when cruidhed) all tend to make
it one of the best substances for fire-proof construction.
Slag is cheap and abundant, liut requires great eare in
selection, as some kinds contain a large amount of sul-
phur, which is very detrimental to Portland cement,
causing the concrete to blow and expand. The presence
bf sulphur can often be 13et66ted by the smell alone.
When sulphur is present in a heap that has lain for
some time, or sufficiently long to allow the atmosphere to
cleanse the outer surface, it is more difficult to detect. A
hole should then be dug in the heap, and the presence
of sulphur can be ascertained by smell, heat, and color.
It will smell strong, and if nev will be warm, and show
yellow patches. The power of the sulphur is so great
that washing the slag once will not entirely cleanse it.
In some cases frequent washings and long exposures to
the air are necessary. Thel-e are some slags that are free
or nearly so from sulphur, and which can be had direct
from the iron furnaces. The slag from coal and iron
furnaces is largely employed for concrete paving. It is
hard and practically free from sulphur. The best size
is % inch screenings. This when sifted yields a fine kind
for topping, and the residue is useful for the rough coat.
The next best fire-resisting aggregates are fine-bricks,
pottery, scharff, hard clinkers, and pumice-stone. The
last has the advantage of bein'^'extremely light, but it is
too soft for the frictional w6ar. Coke-breeze may to a
certain extent be deprived of its combustible nature and
rendered more fire-resisting by washing and passing it
tlurousrh a ^ inch sieve, then adding 1 part flowers of
^aiphur and 10 parts fine broken bricks to 20 parts of
toke-breeze. The larger breeze rejected by the sieve can

302 CEMENTS AND CONCRETES

be broken small, or used for internal layers of concrete.
The bricks should also be passed through a ^i inch sieve.
The finel* the breeze and brick, the better for receiving
and retaining nails.

Voids in Aggregate^^rr-T^^^ quantity of voids or in-
terstices depends on the shape and size of the aggregates.
The least quantity of voids will be found in those aggre-
gates which are broken small, and contain pieces of va-
rious sizes. Gravel free from sand contains about 30
per cent, of voids, and broken stone of uniform size about
50 per cent. Sand is often mixed with gravely stones,
&c., to lessen the quantity, or fill the voids, so as to en-
sure the full strength of the concrete, without adding
more cement than the proper ratio. The following
method is us^ed to ascertain the voids in aggregates: —
Pill a box of known capacity with damp, broken aggre-
gate ; start shaking it during the operation ; then fill the
box to the brim with water ; the quantity of water is the
measure of the voids in the aggregate. Having now
briefly reviewed the characteristics of the aggregates
most used, the practical conclusions to be drawn are that
they should be angular in form, ]iard in nature, grad-
uated in size, and clean.

Crushing Strength of Concrete. — The crushing
strength of concrete depends upon the ratio of cement,
jand the nature of the aggregate. Another important
factor is compression, done by heating and ramming.
Compression increases the weight of concrete about 4 per
cent., and the strength about 25 per cent. The follow-
ing table shows the crushing strength of concrete made
with Portland cement and various kinds of aggregates as
given by Mr. Grant. The tests were made with 6-ineh
cubes. One-half were compressed by heating the con-
crete into the mould with a mallet; the other half were

HOW TO USE THEM

303

not compressed. The whole were kept in the air for a
year before being crushed.

The granite and slag might have been expected to
have given the better results. It is probabk that they
were unwashed, and contained a considerable amount of
dust. If the compression was done by hydraulic power,
so as to obtain a uniform compression in all the cubes,
the results would be more reliable.

Cbushing Strength (in Tons per Square Foot) op
Portland Cement Concretes Having Various

Aggregates.

Six to One.

Eight to One.

Ten to One.

Nature of Ag-
fcregate.

Com-
pressed.

Not
Com-
pressed.

Com-
pressed.

Not
Com-
pressed.

Com-
pressed.

Not
Com-
pressed.

Ballast

Portland stone

Granite

Pottery

Slag

Flints

81.6
162.4
122.
115.2

92.

82.

72.8
120.
98.
98.4
80.
62.

54.
132.
78.4
88.
78.
70.

50.
98.
58.
72.
56.
56.

42.
88.
62.
74.
42.
60.

32.
76,
46.
56.
34.
51.2

Water for Concrete. — ^Water for concrete should be
perfectly clean, and free from organic and inorganic
impurities. As regards the quantity, it can only be
said that for such purposes as the foundations for pav-
ing, casting blocks, &c., or where the material can be
well rammed, so as to insure perfect consolidation, less is
required than where the concrete can only be poured or
laid in position. When mixed with sufficient water, the
concrete occupies about one-eighth more space than when

304 CEMENTS AND CONCRETES

mixed with the full quantity, and percolation through
the former gauge would be greater than through the lat-
ter. Yet by thorough ramming the former would oc-
cupy less space and offer greater resistance to moisture.
An over-watered gauge >i§ ^low to set, difficult to work,
liable to surface cracks, and often there is a loss of
strength, caused by escape of a portion of liquid cement.
The work will also be unequal in strength, owing to the
liquid cement flowing to various or lower parts, leaving
parts of the aggregate bare and weak.

It must not be inferred from the fpregoing remarks
that water is entirely unnecessary or of little value for
concrete. On the contrary, it is of the utmost value.
The evil is in the fibuse, not in the use. Portland ce-
ment has a great affinity for moisture. For instance, if
a sack of cement is left on or in a damp place, a part of
the contents soon becomes set and extremely hard, which
is a proof of its affinity, and that moisture alone will
set cement without water, far less excess of water. Fresh
cement requires more water than stale cement. Cement-
gauged with sea water sets more slowly than with fresh
water. Sea water should not be used in concrete in-
tended for paving stables, chemical tanks, or similar
places where it will come in contact with ammonia. Sea
water having a lower freezing-point than fresh water, is
sometimes used in frosty weather to allow the work to be
carried on. It ought not, however, to be used for ex-
temal work, especially for plastering facade as it has
the property of attracting moisture and causing an ef-
florescence on the surface. Sometimes in frosty weather
hot water, also hot lime, is used for concrete; but al-
though these hasten the setting and hardening of coiv
Crete, they also wash away some of the finest and best
particles of the cement during the gauging. A part of

HOW TO USE THEM 305

the water also forms in little globules throughout the
mass, and when the water-drops evaporate a series of
small holes or bulbs are left, which deteriorate the
strength of the concrete. Finally, it may be stated that
the quantity of water required for gauging concrete is
regulated by the cla^ and condition of the aggregate, by
the state of the atmosphere, and by the purpose for
which the concrete is required. Another important point "^
is the careful and thorough incorporation of all the ma-
terials when gauging. A mass of raw materials, if
gauged carelessly, will require more water to attain the
same plasticity than that which is carefully gauged. Ap-
proximate quantities of water are given for Portland
cement plastering.. For concrete the quantity is about
21 gallons of water to 1 cubic yard of dry materials. Or
about 1 part by volume to 8 parts. It is a good maxim
to bear in mind when mixing water for concrete, that
other things being equal, the minimum is better than the
maximum. Water may be said to give birth to the
strength of cement; to carry the simile further, the ag-
gregate may be termed the bone, the matrix the skin and
sinew, and the water the blood of concrete.

Gauging Concrete. — It is a common idea that concrete
can be gauged and used anyhow, with any aggregate, or
with any amount of water; and in consequence of a lax-
ity in supervision in the selection of the materials, and
their correct gauging and manipulation, unsatisfactory
results are sometimes arrived at, the blame being at-
tributed to the wrong cause. Gauging concrete re-
quires considerable care to avoid waste of the materials
and obtain the best possible work. Concrete can be
gauged either by hand or by machinery. For small
quantities, such as for stairs and similar work, the
former is almost invariably us^d; and for large quan-

306 CEMENTS AND CONCRETES

titles, such as for foundations or buildings, &c., the lat-
ter, being more economical, is preferable. A careful
and uniform method should be employed for hard
gauging; nothing should be left to chance or rule of
thumb. The gauge-board should be sufficiently large to
allow the materials to be turned over without spilling, it
should be placed as near the work as possible, and it
should be cleaned after each gauge.

For fine concrete, no more than 1 cubic yard should be
gauged at a time. This is as much as three men can
properly gauge at once and m the proper time — ^that is,
before the ** initial set" begins. Portland cement con-
crete, unlike some mortars, does not improve by pro-
longed working. If larger quantities are desirable, then
more men must be employed in the gauging. All ma-
terials should be measured for each gauge, to ensure uni-
form setting and strength, and also the best work. This,
combined with the saving of time and materials, will re-
pay a hundredfold the cost of the measures. It is a
common yet a wrong way, when gauging for paving pur-
poses, to measure the aggregate by so many barrowfula
to a sack of cement. Neither the aggregate nor the ce-
ment can be accurately measured in this haphazard way.
No man fills a barrow twice alike, and the cement being
turned out of the sacks direct onto the aggregate is apt
to vary, as it may contain lumps caused by damp, and
very often some of the finest cement is retained in the
sack, as more often than not it is simply drawn up and
then thrown on one side without shaking it, as would be,
or at least should be done if the cement was emptied for
air-shaking. The aggregate should be measured in a
bottomless box or frame with handles at the ends, the
cement in a box (with a bottom), and the water in a
gallon metal measure or a pail made to contain 4 gal-

HOW TO USE THEM 807

loBS. Five pailfuls of this size are about sufficient to
gauge 1 cubic yard where the concrete can be well
rammed or punned. For work that is simply laid, 1 gal-
lon extra is required. The box frame is laid on the
gauge-board and filled with aggregate (in a damp state).
The frame is lifted off, and the aggregate spread over the
board until about 6 or 7 inches thick. The cement is
then distributed over the aggregate. The materials are
then gauged by three men, two with shovels, and one
with a rake or larry, the former facing the latter. The
dry materials should be carefully but energetically
turned over twice or even thrice, and then when being
turned over the third time water must be gradually ad-
ded by means of a rose fixed on a water-can. Water
poured from a pail is apt to wash pArts of the cement
away ; the water also cannot be regularly and gradually
distributed over the dry materials as when a rose is
used. The mass is again turned over twice or even
thrice, until thoroughly incorporated. This turning over
does not consist of merely turning the mass over in the
centre or on one place of the board, but to be effectively
done a shoveller should stand at each side of the board,
and the raker at the end to which the mass is to be first
turned ; the shovellers lift the stuff and spread or rather
scatter it on one end of the board with a jerking mo-
tion, and the raker further mixes the stuff by working
each shovelful backwards and forwards. This is repeat-
ed, the stuff being turned to the other end of the board,
after which it is turned to the center, the water being
added as already described. The wet mass is then turned
over twice in a similar manner, and finally finished in
the centre of the board. The shovellers in the final mix-
ing turn the stuff from the outside of the heap to the
centre, while the raker gives the final touches. After

308 CEMENTS AND CONCRETES

being gauged, it should not be disturbed, but immediate-
ly shovelled into pails, and conveyed to the place of its
use. The ''initial set" begins nearly or as soon as gauged,
and any after or unnecessary disturbance tends to de-
stroy the setting properties of the cement. The practice
of gauging, and afterwards regauging or knocking it up,
is most objectionable, as it destroys its setting properties.
No more should be gauged at one time than can be con-
veniently laid in one operation. The gauging of this
valuable material should not be left entii^ely to unskilled
labor, but ought to be carried out under careful super-
vision.

Bamming Concrete. — The ramming, beating, or pun-
ning of concrete is of great importance. It compresses
the concrete, rendering it more dense and free from
voids, and forces out all superfluous water. The re-
sultant gain in strength, durability, and imperviousness
is by no means to be despised. Without compression it
is impossible to obtain impervious concrete. Prolonged
ramming, however, is dangerous, as it may be contin-
ued until the cement is set, which would be a direct loss
of strength. For this reason, the ramming of concrete
made with quick-setting cement should immediately fol-
low the deposition of the material, and be expeditiously
done. The concrete should always be gauged rather
stiff than soft. If in the latter form, the ramming will
separate the more fluid portions, and produce strata of
different densities. When the concrete is deposited in
layers, the joints of each layer, if dry or exposed, should
be well swept and watered before the next layer is de-
posited. It is often advisable, especially in very dry
work, to brush the joints with liquid cement after th«y
have been swept and wetted. For larger constructional
work, the joints should also be keyed by aid of a pick, op

HOW TO USE THEM 309

by inserting stones at intervals into the concrete before
it is set, leaving them projecting 3 or 4 inches above the
level of the joint. Another method of forming a key is
eflfected by forcing a batten on edge about 2 or 3 inches
deep into the concrete, at the middle of the joint, and
when the concrete is firm or nearly set the batten is ex-
tracted, thus leaving a groove which forms a key for the
succeeding layer.

No layer that has to be left for some time, or until
dry, should be less than 4 inches deep. Thin layers are
always a source of weakness. If the successive layers
can be laid before the previous one is firm or set, the
thickness is not of so much consequence. For large
work, when each layer has to stand until set, the thick-
ness may vary from 9 to 12 or even 18 inches. Eam-
ming may be done by using an iron punner, or one made
of hardwood and bound with iron. Wooden mallets
and punchers or iron hand-floats are most suitable for
ramming stairs and east work. The gain in strength
is shown in the table of the crushing strength of Port-
land cement concrete.

Thickness of Concrete Paving. — The ttickness of con-
crete paving laid in situ is regulated according to the
purpose and the position of the work. The thickness al-
so depends upon the nature and solidity of the founda-
tions. It is obvious that a thicker paving is required
for a foundation that is weak or soft than for one that
is strong and hard. The best foundations are those com-
posed of strong and well-laid rough concrete. Founda-
tions composed of broken bricks or stone thoroughly con-
solidated by ramlning are the next best. The thickness
of foundations is also regulated by the nature of the
soil and the subsequent traflSc. Paving for the sidewalks
oi mam streets, or where the traffic is heavy and con-

310 CEMENTS AND CONCRETES

tinuous, should not be less than 2 inches. For a medium
traffic, and on a strong foundation, a thickness of 1^
inches will be. sufficient. For side streets, garden paths,
passages in houses, or similar places where the traffic is
light and limited, a thickness from 1 to 1^ inches will
be ample if on a rough concrete foundation ; but if on a
dry **dry,'' that is, broken brick or stone one^ the thick-
ness should not be less than 1% inches. The thickness
for stable floors may vary from 3 to 4 inches, according
to the class of horses. For instance, a thickness of 3
inches would be ample for irace or carriage horses, but 4
inches is necessary for heavy cart horses. The same
rule applies to yards, a thickness of 3 or 3^^ inches
being sufficient for carriages, while 4 inches is required
for carts, wagons^ &c. Factory floors are generally made
2 inches thick, but where there is machinery or wheel
traffic a thickness from 2^ to 3 inches is employed. By
computing the volume and nature of ^ the traffic, and
comparing the tests of concrete paving given herein, the
requisite thickness will be readily obtained. It must of
necessity greatly depend on the class of the materials
and manipulation used for the paving. Like most other
articles, a good material will go further and last longer
than a bad one.

Concrete Paving. — Good pavements proclaim a city's
progress. Isodorus states that the Carthaginians were
the first people to pave streets. The subject of paving
and floors will be best understood by dividing it into two
parts — ^namely, paving, which is a floor surface laid and
resting on solid ground ; and floors, by which are meant
floors over voids. The following items briefly embody
the processes used for most concrete pavings now in
use. Paving in situ is either laid in **one coat" or
**two coats,*' the latter being in more general use than

HOW TO USE THEM 311

the former, yet each method has its individual merits.
One-coaf work is not so liable to rise or laminate as two-
coat work. It takes slightly less labor, the whole thick-
ness being laid in one operation. The aggregate is
either granite or slag, or both in equal proportions,
gauged with Portland cement in the proportion of 2 of
the latter to 5 of the former. Two-coat is laid with
two different aggregates and gauges. The first coat has
a cheap aggregate, such as ballast, clinkers, bricks, or
whinstone, broken so that they will pass through a 1
inch mesh riddle, and gauged in the ratio of 1 of Port-
land cement to 5 of the aggregate. It is laid till within
1 inch of the finished surface. The second coat is laid
as soon as the first is set, and is composed of 1 part of
Portland to 2 of the aggregate, the latter being either
crushed granite, slag, limestone, or whinstone that will
pass through a 3-16 sieve. In some districts fine shingle
is used for the topping aggregate.

Quick-setting solutions are used to reduce the time re-
quired to allow the paving to harden before it is avail-
able for traffic. Many pavements are ruined by being
used before having become sufficiently hard and set.
Many of the so-called quick-setting materials have the
desired effect of setting the concrete quickly, but the
work in many cases is none the better for these solutions.
On no account should these quick-setting materials be
used, unless thoroughy tested and the concrete proved
durable by use and time. In order to protect the sur-
face and allow the paving to be used immediately, P. M.
Bruner, an American engineer and concrete specialist,
covers the surface of the pavement directly it is finished
with a thin coat of plaster or Parian cement, which ad-
mits of walking upon in a few hours, and resists pedes-

312 CEMENTS AND CONCRETES

trian traflSc until the surface proper is sufficiently hard,
after which it is shelled off with a trowel.

Eureka Paving. — This is the name for an improved
concrete, which has been extensively used with good re-
sults for many purposes, such as pavements, floors and
stairs. Eureka, if not exactly one-coat work, is nearer
that than two-coat work, and may be said to be the
happy medium, or a combination of both. Eureka is
laid in two layers. The first is termed the *' rough
coat,'' and the second the ''fine coat" or ''topping."
The topping is laid nearly as soon as the rough coat is
laid, just as in rendering or dubbing-out plaster work.
The materials and gauges are nearly alike for both
layers. The gauged rough stuff is laid on the founda-
tion, previously wetted to prevent suction, and spread
and beaten with an iron hand-float. The laying, spread-
ing and beating is continued until the rough surface
is within l^ inch of the finished line. The surface of
the rough coat is made fair, and a uniform thickness
for the topping is obtained by passing a "gauge-rule"
across the surface. A uniform thickness of topping
gives an equal expansion, therefore the surface is not
liable to crack. The suction is also more regular, which
permits of the trowelling to be done with greater free-
dom, and without causing hard and soft places on the
surface.

As many alternate bays are laid as will allow of all
being topped and finished the same day. When the
number of bays to be laid in on one day has been de-
cided, and the last one roughened in, the first bay will
be firm to receive the topping. The topping is laid and
spread with a wooden hand-float, ruled and trowelled
and brushed as afterwards described in the general pro-
cess. This method of laying a part of the thickness ot

HOW TO USE THEM 313;

the paving, gauging stiff and beating the mass, forces
it into the interstices of the broken dry foundation, and
not only consolidates the foundation and the rough coat,
but also forms a solid bed to receive the topping. The
topping goes in sooner and more regularly on a stiff-
gauged and well-beaten coat than on a soft-gauged one,
or than if the whole thickness of the paving were laid
in one coat.

Eureka Aggregate, — The method of preparing the ag-
gregate for Eureka is of the utmost importance. The
labor expended on its preparation is more than repaid,
not only in the ease and rapidity when finishing, but also
in the satisfaction of doing a strong and workmanlike
job. Slag and granite is far more preferable to gravel
or stone as an aggregate. Slag and granite in equal
proportions have been used with good results. The size
ordered from the furnace or quarry should be % inch
screenings. It must be washed through a % inch sieve
in a tub or iron tank. The coarse part rejected by the
sieve to be laid aside for the rough coat. The fine ag-
gregate is then washed again through a fine sieve to ex-
tract any mud or impalpable powder, as the presence of
such impurities weakens the consolidating power of the
cement, and decreases the ultimate strength of the con-
crete. This fine aggregate for the topping should be
angular and of various graduating sizes, from that of
fine sharp sand to the largest size that has passed through
the % inch sieve. It has been proved by experience and
the test of time that an artificial stone made with a fine
aggregate has not only more resemblance to the grain or
texture of natural stone, but is also denser, and wears
better and with more uniformity, than one made with a
large, round, or equal-sized aggregate. The use of small
and angular aggregate of the graduating sizes ensures

314 CEMENTS AND CONCRETES

their fitting closer and interlocking together, thus form-
ing a stronger bond, giving a regular key and freedom
for each separate piece to be coated with cement, the
whole forming a solid and homogeneous body with a
hard surface. Concrete with large or round aggregate,
and the various pieces disproportionate in size to each
other, will fit loosely and unevenly, and only touch at
their most prominent points, thus leaving voids, and con-
sequently unsound work. The voids may perchance be
wholly or partly filled with matrix, still this is an un-
necessary waste of cement. Consequently, concrete pav-
ing having large or round aggregate wears unevenly, and
leaves the large or round pieces tincoated and loose, or
so exposed above the surface that they soon get dis-
lodged, leaving a series of small holes, which sooner or
later wear larger and larger. Another point of import-
ance is that concrete with a fine hard aggregate is more
plastic, works freer, and has a greater compressive
strength than concrete with a large or soft aggregate.
Eureka concrete, having a fine, clean, and regulated ag-
gregate, should be used for the topping of paving, steps,
landings, or for any class of work exposed to friction or
wear. It is well to remember that a good matrix will
not make a bad aggregate strong, although a bad ag-
gregate will make a good matrix weak, or rather the re-
sultant concrete weak.

Eureka Quantities. — The quantities for the rougji
coat are 1 part of Portland cement and 4 parts of the
coarse portion of Eureka aggregate. These materials
must be gauged stiff, only as much water being used as
will allow the mass to be thoroughly mixed and plastic.
The quantities for the topping are 2 parts of Portland
cement to 5 of the fine aggregate, and gauged about the
consistency of well-tempered ** coarse stuff," as used for

HOW TO USE THEM 315

floating. Experiments prove that neat cement is infe-
rior in wear-resisting qualities (such as frictional wear
and pedestrian traffic) to mixture of cement with sand
or other aggregate, being in fact equal to a mixture of
about 1 part of cement to 3 parts of aggregate. The
best wearing qualities are obtained by a mixture of 2
parts of cement to 3 of aggregate.

Levels and Falls, — ^Accurate levelling and adjustment
of the requisite falls are important features for pave-
ments and flooring. Levelling is the art by which the rel-
ative heights of any number of points are determined.
Falls are used to allow rain and water used for cleansing
purposes to run off into channels and drains. The levels
and falls in godd buildings are generally marked, on the
drawings, but it is imperative that the worker should be
conversant with the necessary amount of falls for paving
purposes, as many unforeseen difficulties often arise in
this class of work, especially in large surfaces. The most
accurate and speedy way of setting out levels and falls
is of special service to concrete paviors. The importance
of these features will be readily appreciated, especially
where these paving preliminaries are left to the care of
the concrete layers. The amount of cross fall for street
pavements varies according to the class and position of
the work. The fall is also regulated by the gradient. For
a level stretch of paving it is generally 1 to 60, therefore
for a pavement 6 feet wide it would be 1 inch. Tljie fall
for rising ground is usually % inch for every 2 feet in
the width of the pavement. The falls for stables and
yards are given under their respective headings. The
points for levelling — also for falls — are formed by driv-
ing wooden pegs into the ground at the most suitable
points. The heads of the pegs represent the finished face
of the pavement. They are made level with each other

816 CEMENTS AND CONCRETES

by the aid of a parallel rule and a spirit-level. Inter-
mediate pegs may also be levelled by means of boning
rods.

Pavement Foundations — Good foundations for con-
crete paving are of primary importance, and unless the
bottom is firm, and the foundation is sound, the best
made and laid concrete will subside, crack, and be per-
manently spoilt. Pavements generally cover a large
area, and the superstructure, however strong, must have
a firm foundation. Foundations consist of two parts —
the first is the bottom ground or natural foundation ; the
second is the made-up or artificial foundation; but for
simplicity the first is termed the ** bottom," and the lat-
ter the ** foundation." The latter may be **dry" or
** gauged." If the bottom is soft, it must be well ram-
med before laying the dry materials for the foundation,
or a layer of common coarse concrete for gauged work.
When excavating the ground to receive the foundation,
the depth from the intended finished surface of the
pavement should be about 5 inches for paving 2 inches
thick, 6 inches deep for paving 2^ inches thick, and 7
inches deep for paving 3 inches thick. The above depths
are for dry foundations, and where the traflSe is light,
such as side-walks, playgrounds, and passages. If the
bottom is soft, or the paving intended for heavy traffic,
the depths may be increased, and the bottom well ram-
med before the materials are laid. The materials for the
dry foundations are broken bricks^ stone rubble^ or other
hard core. They should be spread on the bottom, and
broken in situ. The breaking in situ tends to consoli-
date the bottom and the foundation. When broken, no
piece should be left that will not pass through a 2^4 inch
ring. If the paving is intended for heavy traffic (carta

HOW TO USE THEM 317

or the rolling of heavy casks) it is best to have a rough
concrete foundation. The rough concrete should be
from 4 to 7 inches deep, according to the firmness of the
bottom and class of traffic. This concrete is composed
of ballast or equal parts ballast and broken bricks, coke-
breeze, or hard clinkers, gauged in the proportion of 1
of Portland cement to 5 or 6 of aggregate. It should be
laid to the desired fall. If lime instead of Portland ce-
ment is used for the rough concrete, great care should
be taken to thoroughly damp the surface, and allow a
sufficient time for the lime to expand and any lumps of
unslaked lime to slake, before the fine concrete is laid. No
paving should be laid until the rough concrete is thor-
oughly set. Allowance must also be made for any set-
tlement of the bottom, and for any subsidence, contrac-
tion, or expansion of the concrete foundation. The
rough is not so liable to contraction or expansion as fine
concrete, but it is more liable to subsidence. Expansion
is due to the cement not to the aggregate ; and as there is
less cement in rough concrete than in fine, it has less
power of expansion, and owing to the greater amount
and weight of aggregate, there is the lesser power of con-
traction. The size of aggregate for rough concrete is
also larger than for fine; consequently each piece offers
a greater resistance to the cement. Subsidence is due to
the settlement by gravitation of the aggregate to the bot-
tom, which takes place after the excess water, or even
the liquid cement, has percolated through voids or spaces
of badly made or laid concrete. Unequal subsidence is
caused by bad and unequal gauging; one gauge being
firm, keeps in position ; while if soft and sloppy, the ex-
cess water either settles in the deepest places, or escapes

318 CEMENTS AND CONCRETES

into the ground, thus allowing the body of the concrete-
at those parts to subside.

Screeds and Sections. — Screeds are used as guides and
bearings for leveling and ruling off. They are general-
ly formed with wood rules, planed on all sides, and in
suitable sizes, and are termed ^'screed rules." Screeds
are sometimes formed with the same kind of material as
used for the pavement, and are termed * * gauged screeds. ' *
Screed rules give the best results ; they are speedily laid ;
can be used at once, and form a clean and square joint
when laying work in sections. Screed rules are tempo-
rarily fixed on the foundation by laying them on narrow
strips of gauged concrete, and then made straight, and to
the proper falls, by laying the edge of a straight-edge on
them, and tapping with a hammer till firm and true.
When the bay is finished and set, the screeds are re-
moved by gently tapping with a hammer, leaving a clean,
straight, and square joint. Where there is only a small
quantity of screeds required, or where time will not per-
mit of waiting for the concrete bedding strips to set, the
screed rules can be fixed on gauged plaster, which al-
lows the screeds to be used at once. The plaster should
be cleaned off at the side intended to be laid, to ensure a
sound bed for the concrete, and a square joint. Gauged
screeds may be also formed with gauged coarse plaster.
They are best done as described for *' pressed screeds."
In laying large surfaces it is best to arrange the screeds,
so that the work can be laid in alternate sections or bays,
which will afford greater facility to get at the work, and
also to allow the isolated bays to expand. For instance,
if laying a stretch of paving 50 feet long and 6 feet wide^
this would be laid out in 5-feet bays, the screed rules,
each 6 feet long, being laid so as to form the odd num-

HOW TO USE THEM 319

liered bays to be laid and finished first. This allows the
workmen more freedom by standing on the empty bays
when finishing the laid bay. The screeds are then re-
moved, and the intermediate bays laid, the sides of the
finished bays serving as screed or bearing when ruling
in. Boards or bags are laid on the finished bays to pro-
tect the surface, and give a footing for a workman to
finish off the intermediate spaces. It must not be for-
gotten to fix the screed rules toward the curbs, also to
keep the ends of the screed about % inch about the curb,
to allow for any subsidence, and for the water to run
off. This also provides for the greater amount of wear

StCnOHS OF CONCBBTX KEU, OlAKNItL, AND

Pavihc.

that takes place near t« than actually on the curb. The
foundations should be thoroughly saturated with water
before the screeds are fised. If this is not done, the
brick or other dry material used will absorb the moisture
or life from the concrete, and render it dry or dead. The
drenching with water also frees the broken materials
from the dust caused by breaking the large pieces in
situ. In laying paving or a gauged foundation, the sur-
face should be well swept with a hard broom and after-

320 CEMENTS AND CONCRETES

wards damped, so as to ensure the perfect cohesion and
solidity^ of the foundation and the paving.. The curbs
and channels are sometimes made in situ, but more often
they are cast and laid in the same manner as ordinary-
stone. Cast work is harder than laid work; it also al-
lows the paving to be laid with greater freedom. Illus-
tration No. 1 shows sections of the street curbing and
channel which may be used in connection with slab pav-
ing, or pavements laid in situ.

Laying Concrete Pavements, — The foundations having
been damped, and the rough stuff gauged, it is carried
in pails and emptied at the top end of the bay. The plas-
terer spreads it with a layer float, and rams it well into
the foundation. When he has laid a stretch the whole
width of the bay, and as far as he can conveniently reach,
he moves back and lays the remaining portions of the
bay in the same way until complete. The rough ^stuff
surface is then made fair, but not smooth, with the gauge
rule. The remainder of the bays are dealt with in rota-
tion. The fine aggregate is then gauged, and laid and
spread until flush with the screeds. The stuff should be
rather above than below the screeds, to allow for subsi-
dence by subsequent ramming, ruling and patting. All
concrete bodies over 2 inches thick should be deposited
in layers. Each layer should be well rammed with an
iron, or hardwood temp, bound with iron. Concrete
gains strength by compression, and consequently its
density, imperviousness, and durability are increased.
Even for 2 inch pavement better results are obtained if
the stuff is deposited in two layers, each layer well
beaten with an iron hand-float. If only 1^ inches thick,
it should be consolidated by being beaten with an iron
float. The surface is next ruled with a floating rule.

HOW TO USE THEM 321

The rule is worked square or edge, and the concrete cut
and beaten in successive short and quick strokes. ,If the
stuff is soft and laid too full, the rule is worked loosely
on edge with a zigzag motion, so as to draw the excess
stuff and water off the surface, and leave the body full
and regular. If there are any hollow places, they are
filled up with stuff, and the rule again applied. In all
cases the surface should be finally straightened by beat-
ing with the rule. This process leaves the surface more
uniform, straight, and solid than by dragging or working
the rule.

Trowelling Concrete. — ^After being ruled, and when,
slightly firm, the surface is beaten with a wood hand-
float, which lays any irregular parts or projecting pieces
of aggregate. The beating or patting is continued until
the ''fat" appears on the surface. It is then trowelled,
or rather ironed, the trowel being worked on the flat of
the blade with a circular motion. , The plasterer, when
trowelling off, should have a hand-float in the other
hand to lean on when reaching to a far off part. The
float is also useful to pat any dry parts. The surface
must be finished with a semi-dry stock^brush to obtain a
uniform grain. A vast amount of care is required in
trowelling off. Perfection can only be attained by prac-
tice; and a clcse observation of the materials, conditions,
and the state of the atmosphere during the progress of
the work. The best effects can only be attained by
acquiring a knack of working the trowel on the flat, and
by knowing when to begin and when to leave off. It is a
tvaste of time, and the cause of an unequal surface, if
the trowelling is begun before the stuff is firm ; but time
and labor will also be lost if the trowelling is left until
the stuff is too stiff, or has nearly set, for then the sur-

m CEMENTS AND CONCRETES

face will be rough and patchy. In either instance the
surface is more or less spoilt, and the ultimate appear-
ance and hardness seriously aflfected.

Grouting, — The use of neat cement for trowelling off
Bhould not be resorted to (this is termed ** grouting"),
and is used when the surface is left till set, or when it
has not been properly patted and trowelled. The ex-
pansion of a strong and weak gauge being unequal, the
result is that the surface peels, or should it adhere, it is
patchy and discolored. Where grouting is unavoidable,
the cement should be gauged with an equal part of fine
aggregate, the aggregate being the same as used for the
topping.

Dusting. — ^Another bad process is that of sprinkling
dry neat cement over a soft surface (this is termed
** dusting"), and is used to absorb the moisture caused^
by sloppy gauging. ' It has drawbacks similar to grout-
ing. If unavoidable, the cement should be mixed with
fine dry aggregate in the same proportion as the topping.
If the stuff were trowelled at the correct time, there
would be no necessity for grouting; and if properly
gauged, no need for dusting. No concrete surface can be
made so solid and hard as when it is finished in one body
and at one time.

Temperature, — It is well known that extreme heat and
cold effect the expansion and contraction of iron. These
extremes have a similar effect on concrete, especially dur-
ing the process of setting and hardening. Equality of
temperature during setting is desirable. Cold and
humid atmosphere retard setting; hot humidity acceler-
ates it. Concrete laid in cold weather stands better
than that laid during hot. Concrete laid in mild damp
weather is better than in either extreme. During high

/
(

HOW TO USE THEM 323

temperatures, the surface, when suflSeiently hard, should
be covered with damp deal saw-dust, old sacks, matSj or
sail-cloth, and saturated at intervals with water. If the
sun's rays are hot, the surface of the work while in
progress should be protected by extending tarpaulin or
sail-cloths above the parts being laid. Concrete surfaces
are further hardened by flooding with water, or where
this is not practical, covering with wet saw-dust or sand
as soon as ^et. Care must be taken that the- saw-dust is
clean and of a light color, as otherwise it will stain the
work.

Non-Slippery Pavements, — Concrete pavements foir
special purposes are rendered non-slippery by mixing Vg
inch lead cubes with the topping stuff. Lead cubes about
y2 inch square laid by hand from 1 inch to 4 inches
apart in the moist concrete surface, have been used for
rendering concrete surfaces non-slippery. Iron and
brass filings are also used for the same purpose, and also
for increasing the wear-resisting of concrete surface.
Roughened, indented, grooved, and matted surfaces are
also used to obtain a better foot-hold on concrete sur-
faces.

Grooved and Roughened Surfaces. — Stables, yards,
&c., are grooved and channeled on the surfaces to pre-
vent animals from slipping, and also to carry off urine
or other liquids to the traps or guUeys. Indented sur-
faces are useful on steep gradient to give a better foot-
hold. Grooves are made with a special wood or iron
tool, which is beaten into the surface as soon as the con-
crete is floated. The grooves for stables are generally
made about 5 inches from centre to centre, and the depth
about % inch. A line is first made at the one end of the
work, and the groover is then laid on this line, and beat-

324 CEMENTS AND CONCRETES

en down with a hammer to the desired depth. Before it
is taken off^ a parallel rule is laid on the surfaoe and
against the groover, which is then taken up and laid
close to the other side of the parallel rule, and beaten
in as before, and so on until the whole surface is done.
The width of the parallel rule is equal to the desired
width between the grooves, less the width of the groover.
Grooves, however long, can be made by moving the tool
along, and against a long parallel rule. After stretch of
grooves have been sunk, the surface is trowelled, and the
indentations made true. It may be necessary to apply
the groover again, and beat or work it forward and back-
ward and further regulate their depth and straightness.
They are then made smooth with a gauging trowel and
finished with adampbrush,thesidesof the grooves being
left smooth to give a free passage for liquids.

Grooves on a surface having a fall should radiate to-
ward the deepest point. A level surface may be made
to carry off the water by the indentation being formed
wider and deeper towards the outlet. Street and other
pavements are sometimes indented with metal rollers to
give a better foot-hold. Platforms and other surfaces are
sometimes made rough or indented by beating the moist
concrete, with a ** stamping-float." The sole has a series
of squares projecting about % inch, each square about
1 inch, and a half inch apart. Concrete surfaces are al-
so roughened or matted by dabbing the surface as soon
as trowelled with a coarse stiff whale-bone brush. Illus-
tration No. 2 shows three designs of grooved surfaces for
carriage drives, conservatories, &c. A plain border, or
one with a single width of the main design, is generally
formed on the sides and ends of the floor. A rough mat-

HOW TO USE THEM 325

ted aurfaee may also be obtain'ed by pressing or beating
a wet coarse sack or matting over the moist concrete.

Stamped Concrete. — Various materials and methods

are used for stamping or indenting concrete surfaces to

, obtain a better foot-held, or to form any desired pattern.

Iron stamps are generally used, but owing to their

weight and rigid nature, are unsuitable for large sec-

FiE. I. FiE- ^ Fig. 3.

tions. Plaster stamps are sometimes used for temporary
purposes, or for small sections and quantities. Stamps
for large concrete surfaces should be composed of a ma-
terial that is easily made to the desired form durable
and lightly flexible.

Expansion Joints. — Compressive or flexible joints are
used to allow for any expansion or contraction that may
take place in a large area of concrete exposed to atmos-
pheric changes. There are various methods in use for

826 CEMENTS AND CONCRETES

the purpose. The first is to set out the area in small
sections, and to lay them in alternate or isolated bays,
thus givi^^time for their expansion before the inter-
mediate bays are laid. This method, by dividing the
area into small sections, is the best for preventing cracks,
because small sections are stronger than large ones ; and
in the event of any subsidence in the foxmdation, the
surface fissures are limited to the immediate joints of
the section. Contraction and expansion is also less in
email bodies than in larger ones.

Another method of forming joints is by cutting with a
wide chisel or a cutting tool before the rough concrete is
set, a corresponding joint being cut in the fine concrete
topping. False joints are made by indenting the top-
ping after it is trowelled. A metal roller is used for
finishing true joints and forming false joints. Frame
strong enough to resist the expansion of the concrete
livould not only increase the density and strength of
concrete paving and blocks, but also effectually prevent
its cracking.

Another method for forming sections in large sur-
faces of pavement of floors to prevent cracks is effected
thus: — ^first set out the size of proposed sections on the
rough or first coat, then with a straight-edge, a wide
chisel, or a cutting tool and a hammer^ cut through- the
rough coat, so as to divide it into sections as set out.
This done, insert wood strips into the cutting, keeping
their top edges about % inch below the screeds or rules
which represent the finished surface. The strips are
made from % to 1% inches wide, 3-16 inch thick, and in
suitable lengths. The width is regulated according to
the thickness of the paving. For instance, for two inch
paving the widths should be 1% inches. This allows

HOW TO USE THEM

327

abont % inches in the rough coat (with % inch play
from the bottom)^ and about % inch in the topping, and
Ys inch for the upper thickness of the topping to cover
the top edges of the strips. After the strips are inserted
the rough coat is beaten up or Inade good to the sides of
the strips, and then the topping is laid and trowelled in
the usual way. The surface joints are then made direct-

•Half Plan op Coach Yard» with
Sbction through Centrb.

NO. a

ly over the strips, with the aid of a straight edge, so as
to form a clean and sharp joint. As already mentioned,
these strips allow for any subsequent contraction or ex-
pansion, thus avoiding zigzag cracks; and in the event of
repairs to underneath pipes, each section can be cut out
and relaid separately without injury to the adjoining
sections. This process of inserting strips in the rough
coat, cutting nearly through the topping, gives the same
results as. if the strips were laid flush with the surface
of the topping, with the advantages that the surface can
be more readily trowelled, and is more pleasing to tho

328 CEMENTS AND CONCRETES

eye, because the strips are not seen. A cutting tool is a
blade of steel about 5 or 6 inches long and 4 inches wide,
with a wood handle at one end. The section of the blade
is well tapered, so as to obtain a sharp cutting edge, and
form a wide top edge to offer a broad surface for the
hammer while being beaten.

Washing Yards.^— Eureka . concrete being of a hard
nature, and having a close and smooth surface, is well
adapted as a flooring for all washing or cleaning pur-
poses. The surface being smooth, it can in turn be read-
ily cleaned. Illustration No. 3 shows the half plan of
washing yard for washing carriages, &c.

Stalle Pavements. — The paving for stables, and other
places for keeping animals, should be jointless, non-ab-
sorbent, hard, and durable. Such paving must not be
slippery, yet smooth enough to be easily washed, the
whole laid to falls, and grooved to give an easy and
ready passage for liquid manure and water when being
washed. No material caii so fully meet these require-
ments as a well-made and well-laid concrete. Granite
sets are hard, but slippery. Bricks are too absorbent;
the urine percolates between the joints and generates
anunonia and other eflfluvia which are detrimental to the
health of the animals. (See Nos. 4 and 5.)

Stables are generally laid with a fall toward the main
channel. The amount of fall varies according to ideas
of the horse owners. The fall adopted by the War office is
1 in 80 from the top of the manger to the main channel,
and 1 to 36 from each side of the stall to the centre groove.
The width of the main channels is usually set out with.
screed rules, which also act as screeds to work from.
Channels are generally formed after the other surface is
finished. Sometimes templates are fixed on the bed of

HOW TO USE THEM

329

the channels, and the space filled in and ruled oflf with a
straight-edge while the whole surface is being formed.
,The thickness of stable paving varies from 2 to 314
inches, according to the class of horse. The thickness of
the stalls is often decreased toward the manger.

The most useful length is 2 feet 6 inches. They can
be cut with a chisel as easy as cutting stone. Special
slabs can be made for circular work, also with rebated
sinking for metal plates, to cover coal-holes, drains, gas
and water taps, &c. Concrete paving slabs are laid in
precisely the same way as natural stone.

diUApt,

S^iiofL <f Channel «| B

iron fraJS^ jS^ef:liot% y* cn»hrtfnv>n J>

-Sections of the various Parts of the Stable Floors
SHOWN ON Illustration

NO. 4. NO. 6.

Concrete Slab Moulds, — Slab moulds are made with
1% inch boards ledged together. On this ground, wood
sides and ends (each being 2^ inches by 2 inches, or 3
inches by 3 inches, according to the desired thickness of
slab) are fixed. One side and end is held in position
with thumb screws, which fit into iron sockets, so that
they can be unscrewed to relieve the slab when set. The
bottom and the sides and ends are lined with strong iron
or zinc plates.

330 CEMENTS AND CONCRETES

Slab Making, — ^Slabs are mostly made by maehinery.
The materials, are 1 part of Portland cement mixed dry
with 21/^ parts of <;rushed granite and slag in equal pro-
portions that have been washed and passed through a ^4
inch sieve. They are thoroughly incorporated together
in a horizontal cylinder worked by machinery, a mini-
mum of water being added, and the mixing cojitinued
until the mass is well gauged. The mould, which has
been previously oiled, is placed on a shaking machine
known as a ** trembler" or ** dither," which gives a rapid
vertical jolting motion to the mould and its contents. A
small portion of **slip," that is, neat cement, is laid
round the angles. The machine is then started, and the
concrete laid on the mould by small shovelfuls at a time,
a man with a trowel spreading it over the mould until
full. The surface is then ruled off. If both sides of the
slabs are required for use, the upper surface is trowelled.
The whole operation of mixing, filling in, and ruling oflE
takes about seven minutes. The filled moulds are re-
moved and allowed to stand for about three days. The
slabs are then taken out, and stacked on edge and air-
dried for ab(mt five days. They are then immersed in
a silicate bath for about seven days, and are afterwards
taken out and stacked in the open air until it is required
for use. They should not be used until three months
old. Paving slabs are also made by hand, by ramming
and beating the moist concrete into the mould with an
iron hand-float. Powerful ramming, trituration, or vio-
lent agitation of the gauged material in the moiild, tend
to consolidate concrete, and it is possible to further in-
crease homogeneity by the use of hydraulic pressure. -

Induration Concrete Slabs. — The surface of concrete
slabs or other work exposed to friction or wear may be

HOW. TO USE THEM 331

hardened by soaking in a silicate solution. Silicate of
soda has a great affinity for the materials of which con-
crete is composed, and by induration causes the surface
to become hard, dense, and non-porous.

The silicate of soda and potash is known as soluble
glass or dissolved flint. The soluble silicate is a clear
viscous substance made from pure flint and caustic soda,
which is digested by heat under pressure indigester. Its
•strength is technically known as 140 degrees, which
shows 1,700 on a hygrometer. When used as a bath for
concrete, it is diluted with water, the proportion vary-
ing from, 6 to 10 parts of water to one of silicate. Con-
crete pavements, laid in situ, may also be hardenied by
washing with silicate solution. They should not be sili-
cated until two days after being laid, to allow the mois-
ture to evaporate and the silicate to penetrate.

Mosaic. — The art of making mosaic is at the present
time scarcely within the province of plasterers, but in
former times many kinds were made in situ or in slabs
by plasterers. The subdivision of labor has to a great
extent caused mosaic-making to be confined to special-
ists. Concrete is still made by plasterers. A brief de-
scription of this and other kinds may prove useful as
well as interesting, especially to plasterers who. are in
the habit of filling tiles and working in concrete. Mosdic
is the art of producing geometrical, floral, or figured de-
signs, by the joining together of hard stones, marbles,
earthenware, glass, or artificial stone, either naturally
or artificially colored. The term ** mosaic'' embraces a
wide range of artistic processes and materials for the
decoration of floors, walls, ceilings. The Egyptians were
experts in mosaic. The Cairo worker as a rule had no
drawings made beforehand, but the mosaic design was

332 CEMENTS AND CONCRETES

constructed by the artist as he arranged the pieces on
the ground. The mosaic pavements of Cairo are of a
slightly different character from those used for wall
decoration, and are generally composed entirely of mar-
ble tesserae (and sometimes red earthenware) of larger
size than the delicate pieces included in wall mosaics.
They are arranged to f orm^eometrical patterns within
a space of about two feet square. Each square slab is
made separately, and the pieces are set, not in plaster/
but in a composition of lime and clay impervious to
water. The clay must be unbumt, just as it comes from
the pit. Saracenic mosaic in Egypt is a combination of
the tesselated method with a large propoi*tion of sectile
mosaic. The Eomans also were great workers in mosaic.
The mosaics of Byzantium and Ravenna consisted of
, cubes of opaque and colored glass.

The general method used here for pavement mosaic is
as follows : The repeated design is traced on stout paper
and small pieces of marble, or more often tile, are
gummed on the paper, following the design of form and
color, one piece at a time (with the smooth face down-
wards) being laid until the design is completed. The
mosaic slabs, which are thus temporarily kept in posi-
tion, are sent to the building and laid where intended.
A rough concrete foundation, which has previously been
made level, is then floated with Portland or Keen's
cement, and the slabs with paper are then damped and
drawn off, and any openings or defects filled up with
small pieces of the same form and color as the design.
The slabs are made in various sizes according to the de-
sign. For instance, a border 12 inches wide may be made
from 3 to 6 inches long. When laying the slabs, it is best
to begin at the centre and work outwards, and any

HOW TO USB THEM 333

cess or deficiency taken oflf or mad^ up in the plain part
of the border at the walls. The tiles are made at pottery-
works in the required sizes and colors. The thickness is
generally about ^ inch and the average surface size
about y^ inch. Females are often employed fixing the
pieces on the paper. The designs of coats of arms, mono-
grams, dates, figures, flowers, and foliage are efEectively
produced by this simple and cheap process.

Concrete Mosaic, — All mosaics are mor^ or less of a
concretive nature, and the trade term of ** concrete mo-
saic" is due to the fact that the matrix used is Portland
or other cement gauged with the marble aggregate, and
laid in most cases in a similar manner as ordinary con-
crete. Concrete mosaic is extensively used for paving
halls, corridors, conservatories, terraces, &c. It is also
used for constructing steps, landings, baths, pedestals,
&c. Slabs and tiles made of this class of mosaic for
paving purposes are slowly but surely proving a for-
midable rival to Italian mosaic encaustic tiles. It can
be made in larger sections, thus facilitating rapidity of
laying. It is more accurate in form, durable, non-slip-
pery, and cheaper. The last reason alone is a favorable
item in this keen age of competition. Where marble has
been scarce, broken tiles, pottery, colored glass, flints,
white spar, &c., have been used as aggregate. If the
marble chips are obtainable as a waste, and near the place
of manufacture, the primary cost is small. If the moulds
are of metal, and made in sections so as to form a series
of moulds in one case, and the casts are pressed by means
of a hydraulic power, the cost of production is reduced
to a minimum. If the casts are polished in large num-
bers by machinery on a revolving table, the total cost is
further reduced. For local purposes they can be made

334 CEMENTS AND CONCRETES

by hand at a medium cost. Slabs are made in almost
any size, but generally from 4 to 6 feet superficial. The
thickness varies from 1 to 1% inches. Tiles are usually
made about 10 inches square and 1 inch thick. The tiles
are generally made with a face of cement and white mar-
ble, or white and black marble chippings. They are
backed up with a cheaper aggregate. Various tints of
the face matrix are obtained by mixing the cement with
metallic ovides. The tiles are made in wood or metal
moulds, ^ith metal strips to form the divisions of form
and color in the design. If the design is fret pattern,
the gauged material is put in between the strips. that
form the band of the fret. When the stuff is nearly set,
the strips are taken out, and the other part nlled in with
another color. Sometimes the band or running designs
are cast in a separate mould, and when set placed in posi-
tion in a larger mould, and the ground filled in, cover-
ing and binding the whole in one tile. Another plan is
to lay a thin coat of cement on the face of the mould,
forming the design with small marble chips by hand, by
pressing the marble into the cement as desired. When
it is firm, it is backed up with the ordinary stuflf, and
when set, they are ground and polished.

Concrete Mosaic Laid 'Hn Situ." — ^Pavements for
haUs, passages, shops, landings, &c., are also done in situ.
A rough concrete foundation is first laid fair to falls
and levels within ^ inch of the finished surface line.
This % inch space is to receive the plastic marble mo-
saic. The main or centre part is generally done first
and the border last. This allows a walking space or
bearing for boards, laid from side to side to work on
when laying the centre. A plank sufficiently strong to
keep one or two crossboardi^ from touching the work is

HOW TO USE THEM 335

laid along each side. On the side planks the erossboards
are laid, and moved about when required. The width of
the border is marked on the floor, and wood sereed rules
laid level to the marks to form a fair joint line for the
border, also as a screed when floating the centre part.
The screed rules are generally fixed with a gauge plaster,
which is quicker than fixing on gauged cement. After
the centre is laid, the plaster should be carefully swept
off, and the concrete well wetted before the border is laid.
The marble and cement is gauged in the proportion of 2
of marble to 1 of cement, and laid flush with screeds,
laying and beating it in position with a long wood hand-
float. The surface is ruled in from screed to screed with
a straight-edge. The surface is then ironed with a lay-
ing trowel until it is smooth and fair. If the marble
does not show, or is not regular, or is insufficient, the
bare parts are filled in with marble by hand. When
marble is scarce, the ^ inch of the top surface is laid in
two coats, the first being composed of cement and a
cheaper aggregate, such as broken stone, tiles, &c., and
gauged in the same proportion as the upper or marble
coat. It is laid about ^ inch thick, and when it is firm,
but not set, the marble coat is laid as before directed.
The first coat saves the marble, and being firm, tends to
keep the marble in the upper coat from sinking. The
top coat is sometimes sprinkled over with fine marble
chips by hand or through a fine sieve, then pressed into
the surface and ironed with a laying trowel. Before
ironing the surface, care should be taken that the chips
are equally distributed, also that their flat surfaces are
uppermost, and that the matrix and chips are perfectly
jsolid and free from ridges and holes. After the centre
is laid abd the screeds removed, the border is laid in a

336 CEMENTS AND CONCRETES

similar way. If there are two or more colors or forms in
the border, the divisions are formed with narrovv screed
rules, and arranged so that as many as practicable can
be laid at the same time. This allows the various parts
to set at one time, and saves waiting for each separate
part to set. The screed rules for circular work or angles
are formed with strong gauged plaster andi;hen oiled.

The marble chips are either broken by hand or in a
stone-breaking machine. The chips vary in size from
1-10 to % inch. The best colors for borders are a black
matrix with white marble or spar chips, or a white
matrix with black marble chips. The white matrix is
obtained by mixing the marble dust (produced when
breaking the marble into chips) with a light colored
Portland cement. The centres can be made in various
tints, but the most general is a warm red, which is ob-
tained by mixing the cement with red oxide. Cement
colored with red oxide should be laid first, as it is liable
to stain other parts of a lighter color. When the centre
and border are laid, the floor is left until the whole is
perfectly set and hard, and it is l^en fit to polish. This
is done by means of a stone polisher, water and marble
dust, or fine slag powder. The stone polisher is a piece
of hard stone from 8 to 12 inches square, and about 3
inches thick, into which an iron ring is inserted and se-
cured with lead. A wooden handle from 4 to 6 feet long,
with an iron hook at one end, is inserted into the ring,
so that the handle is firm on the stone, yet has sufficient
play to be moved freely backwards and forwards. The
polishing should not be attempted until the stuff is thor-
oughly set, because the polishing will destroy the face
of the cement, and cause a vast amount of extra labor in
grinding the surface down until free from holes. Small

HOW TO USE THEM 337

parts of the gauged stuff should be set aside as tests for
determining when the stuflf is set. Concrete mosaic,
where economy is desirable, will make a strong, durable,
and waterproof floor, and an excellent substitute for
higher class mosaics.

A Bulletin (No. 235), prepared by P. S. Wormley for
the U. S. government on cement, mortar, and concrete^
from which I quote at length, contains some excellent in-
formation and instructions on the preparation and the
use of the above materials. This bulletin is intended for
free distribution and may be obtained by making appli-
cation to the U. S. Department of Agriculture, Wash-
ington, D. C. ^

Storing Cement, — In storing cemept care must be ex-
ercised to insure its being kept dry. When no house or
shed is available for the purpose, a rough platform may
be erected clear of the ground, on which the cement may
be placed and so covered as to exclude water. When
properly protected, it often improves with age. Cement
is shipped in barrels or bags, the size and weight of
which usually are given.

Cement Mortar. — Cement mortar is an intimate mix-
ture of cement and sand mixed with sufficient water to
produce a plastic mass. The amount of water will vary
according to the proportion and condition of the sand,
and had best be determined independently in each case.
Sand is used both for the sake of economy and to avoid
cracks due to shrinkage of cement in setting. Where
great strength is required, there should be at least suffi-
cient cement to fill the voids or air spaces in the sand,
and a slight excess is preferable in order to compensate
for any uneven distribution in mixing. Common propor-
tions for Portland cement mortar are 3 parts, sand to 1

338 CEMENTS AND CONCRETES

of cement, and for natural cement mortar, 2 parts sand
to 1 of cement. Unless otherwise stated, materials for
mortar or concrete are considered to be proportioned by
Tolume, the cement being slightly shaken in the measure
used.

A **lean'' mortar is one having only a small propor-
tion of cement, while a **rich'' mixture is one with a
large proportion of cement. **Neat" cement is pure
cement, or that with no admixture of sand. The term
'* aggregate'' is used to designate the coarse materials en-
tering into concrete — ^usually gravel or crushed rock.
The proportion in which the three elements enter into
the mixture is usually expressed by three figures sepa-
rated by dashes— as, for instance, 1-2-5, meaning 1 part
cement, 2 parts sand, and 5 parts aggregate. In the
great majority of cases cement mortar is subjected only
to compression, and for this reason it would seem nat-
ural that, in testing it, to determine its compressive
strength. The tensile strength of cement mortar, how-
ever, is usually determined, and from this its resistance
to compression may be assumed to be from 8 to 12 times
greater. A direct determination of the compressive
strength is a less simple operation, for which reason the
tensile test is in most cases accepted as indicating the
strength of the cement.

Mixing. — In mixing cement mortar it is best to use a
platform of convenient size or a shallow box. First, de-
posit the requisite amount of sand in a uniform layer,
and on top of this spread the cement. These should be
mixed dry with shovels or hoes, until the whole mass ex-
hibits a uniform color. Next, form a crater of the dry
mixture, and into this pour nearly the entire quantity of
water required for the batch. Work the dry material

HOW TO USE THEM 339

from the outside toward the centre, until all the water
is taken up, then turn rapidly with shovels, adding water
at the same time by sprinkling until the desired consist-
ency is attained. It is frequently specified that the mor-
tar shall be turned a certain number of times, but a bet-
ter practice for securing a uniform mixture is to watch
the operation and judge by the eye when the mixing has
been carried far enough. In brick masonry the mis-
take is frequently made of mixing the mortar very wet
and relying upon the bricks to absorb the. excess of
water. It is better, however, to wet the brick thoroughly
and use a stiflf mortar.

Grout. — The term ** grout'' is applied to mortar mixed
with an excess of water, which gives about the consist-
ency of cream. This material is often used to fill the
voids in stone-masonry, and in brick work the inner por-
tions of walls are frequently laid dry and grouted. The
practice in either case is to be condemned, except where
the conditions are unusual, as cement used in this way
will never develop its full strength.

Lime and Cement Mortar. — ^L. C. Sabin finds that in
Portland cement mortar containing three parts sand to
1 of cement, 10 per cent, of the cement may be replaced
by lime in the form of paste without diminishing the
strength of the mortar, and at the same time rendering it
more plastic. In the case of natural cement mortar, lime
may be added to the extent of 20 to 25 per cent, of the
cement with good results. The increased plasticity due
to the addition of lime much facilitates the operation of
laying bricks, and has caused lime and cement mortar to
be largely used.

Cement Mortar for Plastering. — In plastering with
cement, a few precautions must be observed to insure

340 CEMENTS AND CONCRETES

good and permanent results. The surface to receive the
plaster should be rough, perfectly clean, and well satu-
rated with water. A mortar very rich in cement is
rather a drawback than otherwise on account of shrink-
age cracks, which frequently appear. The mortar, con-
sisting of two or three parts sand to one of cement,
should be mixed with as little water as possible and well
worked to produce plasticity. It is essential that the
plaster be kept moist until it has thoroughly hardened.

Materidk for Making Concrete Sand. — In securing
sand for mixing mortar or concrete, if it is possible to
select from several varieties, that sand should be chosen
which is composed of sharp, angular grains, varying in
size from coarse to fine. Such sand is, however, not
always obtainable, nor is it essential for good work. Any
coarse-grained sand which -is fairly clean will answer
the purpose. If gravel, sticks, or leaves be present they
should be removed by screening. The voids in sand vary
from 30 to 40 per cent., according to the variation in
size of grains. A sand with different-sized grains is to
be preferred, because less cement is required to fill the
voids. By mixing coarse and fine sand it is possible to
reduce the voids considerably.

It is customary to use the terms ** river sand," **sea
sand," or **pit sand," according to the source of the
supply. Eiver sand as a rule has rounded grains, but
unless it contains an excess of clay or other impurities, it
is suitable for general purposes. When river sand is of
a light color and fine-grained it answers well for plaster-
ing.

Sea sand may contain the salts found in the ocean.
The tendency of these salts to attract moisture makes it

HOW TO USE THEM 341

advisable to wash sea sand before using it for plastering
or other work which is to be kept perfectly dry.

Pit sand for the most part will be found to have
sharp, angular grains, which make it excellent for mor-
tar or concrete work. Where clay appears in pockets it
is necessary either to remove it, or else see that it is
thoroughly mixed with the sand. The presence of clay in
excess frequently makes it necessary to wash pit sand
before it is suitable for use.

The results of tests made in this laboratory would m-
dicate that the presence of clay, even in considerable
amounts, is a decided benefit to '*lean" mortars, whereas
it does not appreciably affect the strength of a rich
mixture.

Orwvel, — It is important that gravel for use in con-
crete should be clean, in order that the cement may prop-
erly adhere to it, and form a strong and compact mass.
As with sand, it is well to have the pieces vary in size,
thereby reducing the voids to be filled with mortar. The
voids in general range from 35 to 40 per cent.

Crushed Stone, — The best stone for concrete work con-
sists of angular pieces, varying in size and having a
clean, rough surf aee. Some form of strong and durable
rock is to be preferred, such as limestone, trap, or gran-
ite. The total output of the crusher should be used be-
low a maximum size, depending upon the nature of the
work in hand. All material under % inch will act as so
much sand and should be considered as such in propor-
tioning the mixture. Precautions must be taken to in-
sure a uniform distribution of the smaller pieces of stone,
otherwise the concrete will have an excess of fine ma-
terial in some parts and a deficiency in others.

342 CEMENTS AND CONCRETES

Less than 8 per cent, of clay will probably not seri-
ously impair the strength of the concrete, provided the
stones are not coated with it, and may even prove a
benefit in the case of lean mixtures. The voids in crushed
stone depend upon the shape and variation in size of
pieces, rarely falling below 40 per cent., unless much
fine material is present, and in some cases reaching 50
per cent. A mixture of stone and gravel in equal parts
makes an excellent aggregate for concrete.

Stone Versus Gravel, — ^It would appear from tests that
crushed stone makes a somewhat stronger concrete than
gravel, but the latter is very extensively used with uni-
formly good results. This superiority of stone over
gravel for concrete work is attributed to the fact that the
angular pieces of stone interlock more thoroughly than
do the rounded pebbles, and offer a rougher surface to
the cement. A point in favor of gravel concrete is that
it requires less tamping to produce a compact mass than
in the case of crushed stone. Then, too, the proportion
of voids in stone being usually greater than in gravel,
means a slight increase in the cost of concrete.

Cinders, — Cinders concrete is frequently used in con-
nection with expanded metal and other forms of rein-
forcement for floor construction, and for this purpose it
is well adapted on account of its light weight. Its poros-
ity makes it a poor conductor of heat and pemfits the
driving of naik. Only hard and thoroughly burned cin-
ders should be used, and the concrete must be mixed
quite soft so as to require but little tamping and to avoid
crushing the cinders. Cinder concrete is much weaker,
both in tension and compression, than stone or gravel
concrete, and for this reason admits only of light rein-
forcement.

HOW TO USE THEM 343

^iiC^^nrrr^r ■ frrnrrnl Diiscussion: Cofiigpi: oonerete is
the product resulting from an intimate mixture of
cement mortar with an aggregate of crushed stone,
gravel, or similar material. The aggregate is crushed or
scree Qed to the proper size as determined from the char-
acter of the work. In foundation work, stone or gravel
3 inches in size may be used to advantage, whereas in the
case of moulded articles of small sectioflal area, such as
fence posts, hollow building blocks, &c., it is best to use
only such material as will pass a ^ inch screen. An
ideal concrete, from the standpoint of economy, would
be that in which all voids in the aggregate were com-
pletely filled with sand, and all the voids in the sand
completely filled with cement, without any excess. Un-
der these conditions there would be a thoroughly com-
pact mass and no waste of materials.

It is a simple matter to determine the voids in sand
and also in the aggregate, but in mixing concrete the
proportions vary a great deal, depending in each case
upon the nature of the work and the strength desired.
For example, in the construction of beams and floor pan-
els, where maximum strength with minimum weight is
desired, a rich concrete should be used, whereas in mas-
sive foundation work, in which bulk or weight is the
controlling factor, economy would point to a lean mix-
ture. When goodi*tene or gravel is used, the strength of
the concrete depends upon the strength of the mortar em-
ployed in the mixing and th6 proportion of mortar to
aggregate. For a given mortar the concrete will be
strongest when only enough mortar is used to fill the
voids in the aggregate, less strength being obtained by
using either greater or less proportion. In practice it is

344 CEMENTS AND CONCRETES

usual to add a slight excess of mortar over that required
to fill the voids in the aggregate.

It is more accurate to measure cement by weight un-
less the unit employed be the barrel or sack, because
when taken from the original package and measured in
bulk there is a chance of error due to the amount of
shaking the cement receives. As it is less convenient,
however, to weigh the cement, it is more usual to
measure it by volume, but for the reasons stated this
should be done with care.

Proportioning Materials. — For an accurate determina-
tion of the best and most economical proportions where
maximum strength is required, it is well to proceed in
the following way: First, proportion the cement and
sand so that the cement paste will be 100 per cent, in ex-
cess of the voids in sand; next, determine the voids in
the aggregate and allow sufficient mortar to fill all voids,
with an excess of 10 per cent.

To determine roughly the voids in gravel or crushed
stone prepare a water-tight box of convenient size and
fill with the material to be tested, shake well and smooth
off even with the top. Into this pour water until it rises
flush with the surfaxje. The volume of water added,
divided by the volume of the box, measured in the same
units, represents the proportion of voids. The propor-
tion of voids in sand may be more accurately determined
by subtracting the weight of a cubic foot of packed sand
from 165, the weight of a cubic foot of quartz, and divid-
ing the difference by 165 degrees.

The following will serve as an example of proportion-
ing materials : Assume voids in packed sand to measure
38 per cent., and voids in packed stone to measure 48
per cent. Cement paste required per cubic foot of sand^

HOW TO USB THEM 345

0.38 and 1-10 equals 0.42 cubic foot, approximately. By
trial, 1 cubic foot of loose cement, lightly shaken, makes

0.85 cubic foot of cement paste, and requires ^^ or
2 cubic feet of sand, approximately, producing an
amount of mortar equal to 0.85 and 2 (1-0.38) equals
2.09 cubic feet. Mortar required per cubic foot of stone
equals 0.48, and 1-10x0.48 equals 0.528 cubic foot. There-
fore 2.09 cubic feet mortar will require ^ equals
4 cubic feet of stone, approximately. The proportions
are therefore 1 part cement, 2 parts sand, 4 parts stone.
Although such a determination is usually considered un-
necessary in praxjtical work, it may be of sufficient inter-
est to justify giving it.

For general use the following mixtures are recom-
mended : 1 cement, 2 sand, 4 aggregate, for very strong
and impervious; 1 cement, 2^ sand, 5 aggregate, for
ordinary work requiring moderate strength ; 1 cement, 3
sand, 6 aggregate, for work where strength is of minor
importance.

Aggregate Containing Fine Material, — In the case of
gravel containing sand, or crushed stone from which the
small articles have not been removed by screening, the
amount of such fine sand or fine stone should be deter-
mined and due allowance made for it in proportioning
the mortar.

"When mixing an aggregate containing small particles
with mortar, and in reality we have a mortar containing
a larger proportion of sand than was present before the
aggregate was incorporated. It is evident, then, that in
such cases the quality of richness of the mortal should
depend upon the proportion of fine material in the ag-
grtegate.

346 CEMENTS AND CONCRETES

For example, suppose that 1 cubic foot of gravel con-
tains 0.1 cubic foot of sand, and that the voids in gravel ^
with sand screened out measure 40 per cent. For gen-
eral purposes this would suggest a 1-2-5 mixture, but
since each cubic foot contains 0.1 cubic foot sand^ 5
cubic feet gravel will contain 0.5 cubic foot sand, and
the proportions should be changed to 1 part cement, 1^
parts sand, 5 parts gravel.

Mechanical Mixers. — It has been demonstrated that
concrete can be mixed by machinery as well, if not bet-
ter, than by hand. Moreover, if large quantities of con-
crete are required, a mechanical mixer introduces marked *
economy in the cost of construction. None of the various
forms of mechanical mixers will be described here, since
concrete in small quantities, as would be used on the
farm, is more economically mixed by hand.

Mixing by Hand. — In mixing by hand a platform is
constructed as near the work as is practicable, the sand
and aggregate being dumped in piles at the side. If the
work is to be continuous, this platform should be of suf-
ficient size to accommodate two batches, so that one batch
can be mixed as the other m being deposited. The ce-
ment must be kept under cover and well protected from
moisture. A convenient way of measuring the materials
is by means of a bottomless box or frame made to hold
the exact quantities needed for a batch.

A very common and satisfactory method of mixing
concrete is as follows : First measure the sand and ce-
ment required for a batch and mix these into mortar as
described on page 5. Spread out this mortar in a thin
layer and on top of it spread the aggregate, which has
been previously measured and well wetted. The mixing
is ddne by turning with shovels three or more times, as

HOW TO USE THEM 347

may be found necessary to produce a thoroughly uni-
form mixture, water being added if necessary to give
the proper consistency. The mixers, two or four in num-
ber, according to the size of the batch, face each other
and shovel to right and left, forming two piles, after
which the material is turned back into a pile at the cen-
tre. By giving the shovel a slight twist, the material is
scattered in leaving it and the efficiency of the mixing
is much increased.

Consistency of Concrete. — A dry mixture, from which
water can be brought to the surface only by vigorous
tamping, is probably the strongest, but for the sake of
economy, and to insure a dense concrete well filling the
i^oulds a moderately soft mixture is recommended for
ordinary purposes. Where the pieces to be moulded are
thin, and where small reinforcing metal rods are placed
close together or iieiar the surface, a rather wet mixture
may be necessary to insure the moulds being well filled.

Use of Quick-Setting Cement. — In the manufacture
of such articles as pipe, fence posts, and hollow blocks,
a rather large proportion of quick-setting cement is
sometimes used, the object being to reduce the weight
and consequent freight charges by means of a strong
mixture, as well as to make the concrete impervious to
water. The use of a quick-setting cement permits the
moulds to be removed sooner than would be possible with
a slow-setting cement, thus reducing the number of
moulds necessary for a given output. Quick-setting ce-
ments are not recommended for such purposes, however,
as they are usually inferior to those which set slowly.

Coloring Cement Work, — In coloring cement work the
best results are obtained by the use of mineral pig-
ment. The coloring matter, in proportions depending

348 CEMENTS AND CONCRETES

upon the desired shade, should be thoroughly mixed with
the dry cement before making the mortar. By prepar-
ing small specimens of the mortar and noting the color
after drying, the proper proportions may be determined.

For gray or black, use lampblack.

For yellow or buff, use yellow ochre.

For brown, use umber. .

For red, use Venetian red.

For blue, use ultramarine.

Depositing Concrete, — Concrete should be deposited
in layers of from 4 to 8 inches and thoroughly tamped
before it begins to harden. The tamping required -will
depend upon the consistency of the mixture. If mixed
very dry it must be vigorously rammed to produce a
dense mass, but as the proportion of water increases less
tamping will be found necessary. Concrete should not
be dumped in place from a height of more than 4 feet,
unless it is again mixed at the bottom. A wooden in-
cline may be used for greater heights. Rammers for
ordinary concrete work should weigh from 20 to 30
I)ounds and have a face not exceeding 6 inches square.
A smaller face than this is often desirable, but a larger
one will be less effective in consolidating the mass. In
cramped situations special forms must be employed to
suit the particular conditions. When a thickness of
more than one layer is required, as in foundation work,
two or more layers may be worked at the same time, each
layer slightly in advance of the one next above it and
ail being allowed to set together. At the end of a day
there is usually left a layer partially completed which
must be finished the next day. This layer should not be
beveled off, but ..the last batch of concrete should be
tamped behind a vertical board forming a step.

HOW TO USE TIIEM ' 349

To avoid introducing a plane of weakness where fresh,
concrete is deposited upon that which has already set,
certain precautions have to be observed. The surface of
the old work should be clean and wet before fresh ma-
terial is put on, a thin coat of neat cement grout being
sometimes employed to insure a good bond. . The sur-
face of the concrete to receive an additional layer must
not be finished off smoothly, but should offer a rough
surface to bond with the next layer. This may be done
by roughing the surf a<;e while soft with pick and shovel,
or the concrete may be so rammed as to present a rough
and uneven surface. Wooden blocks or scantling are
sometimes embedded several inches in the work and re-
moved before the concrete hardens, thus forming holes
or grooves to be filled by the next layer.

Retempering. — ^As stated before, it is important that
concrete be tamped in^lace before it begins to harden,
and for this reason it is proper to mix only so much at a
time as is required for immediate use. The retempering
of' concrete which has begun to set is a point over which
there is much controversy. From tests made in this
laboratory it would appear that such concrete suffers b]it
little loss of strength if thoroughly mixed with sufficient
wliter to restore normal consistence.

The time required for concrete to set depends upon
the character of the cement, upon the amount and tem-
perature of the water used in mixing, and upon the
temperature of the air. Concrete mixed dry sets more
quickly than if mixed wet, and the time required for
setting decreases as the temperature of the water rises.
Warm air also hastens the setting.

Concrete Exposed to Sea-Water, — Portland cement
concrete is well adapted for work exposed to sea-water,

350 CEMENTS AND CONCRETES

but when used for this purpose it should be mixed with
fresh water. The concrete must be practically imper-
vious, at least on the surfaces, iand to accomplish this
purpose the materials should be carefully proportioned
and thoroughly mixed. It is also of great importance
that the concrete be well compacted by tamping, par-
ticularly on exposed surfaces.

Concrete Work in Freezing Weather, — Although it is
advisable under ordinary conditions to .discontinue ce-
ment work in freezing weather, Portland cement may be
used without serioua difficulty by taking a few simple
precautions. As little water as possible should be used
in mixing, to hasten the setting of the concrete. To
prevent freezing, hot water is frequently used in mixing
mortar or concrete, and with the same object in view salt
is added in amounts depending upon the degree of cold.
A common practice is to add 1 jyund of salt to 18 gal-
lons of water, with the addition of 1 oz, of salt for each
degree below 32° F. Either of the above methods will
give good results, but it should be remembered that the
addition of salt often produces efflorescence. It seems
to be a fairly well-established fact that concrete de-
posited in freezing weather will ultimately develop full
strength, showing no injury due to the low temperature.

Bubble Concrete. — In massive concrete work consider-
able economy may often be introduced by the use odf
large stones in the body of the work, but only in heavy
foundations, retaining walls, and similar structures
should this form of construction be permitted. In plac-
ing these large stones in the work the greatest care must
be exercised to insure each 'being well bedded, and the
concrete must be thoroughly tamped around them. Each

HOW TO USE THEM 351

sbme should be at least 4 inches from its neighbor and
an equal distance from the face of the work.

To Face Concrete. — A coating of mortar one-half
inch in thickness is frequently placed next the form to
prcTcnt the stone or gravel from showing and .to give
a smooth and impervious surface. If in preparing this
mortar finely crushed stone is used instead of sand, the

HO. A.

work will more nearly resemble natural stone. A
common method employed in facing concrete is to pro-
vide a piece of thin sheet metal of convenient length
and about 8 to 10 inches wide. To this pieces of angle
iron are riveted, so that when placed next to the mould
a narrow space is formed in which the cement mortar is
placed after the concrete has been deposited behind it.
(No. 6.) The metal plate is then withdrawn and the

352 CEMENTS AND CONCRETES

concrete well tamped. The concrete and facing mor*
tar must be put in at the same time so that they will
set together. If the concrete is fairly rich, a smooth
surface can usually be produced without a facing of
mortar by working a spade up and down between the
concrete and inner face of the mould, thus forcing the
larger pieces of the aggregate back from the surface.

Wood for Forms, — ^Lumber used in making forms for
concrete should be dressed on one side and both edges.
The expansion and distortion of the wood due to the
absorption of water from the concrete frequently make
it difficult to produce an even surface on the work, and
unless the forms are accurately fitted together more or
less water will find its way out through the cracks,
carrying some of the cement with it. A method some-
times adopted to mii^imize the effect of expansion is to
bevel one edge of ea<;h board, allowing this edge to
crush against the square edge of the adjacent board
when expansion takes place. In the case of a wooden
core or inside mold, expansion must always be taken intc
consideration, for if neglected it may cause cracks or
complete rupture of the concrete. Sharp edges in con-
crete are easily chipped and should be avoided by plac-
ing triangular strips to the comers of moulds. To pre-
vent cement from sticking to the forms they may be
given a coating of soft soap or be lined with paper.
This greatly facilitates their removal and enables them
to be used again with but little scraping. A wire brush
answers best for cleaning the forms. ^

Cancrete Sidewalks. — ^A useful and comparatively
simple application of concrete is in the construction of
sidewalks, for which purpose it has been used with
marked success for a number of years. '

HOW TO USE THEM 353

Excavation and Preparation of Subgrade. — The
ground is excavated to subgrade and well consolidated
by ramming to prepare it for the subfoundation of
stone, gravel or cinders. The depth of excavation will
depend upon the climate and nature of the ground,
being deeper in localities where heavy frosts occur or
where the ground is soft than in climates where there
are no frosts. In the former case the excavation should
be carried to a depth of 12 inches, whereas in the latter
from 4 to 6 inches will be sufficient. No roots of trees
should be left above the subgrade.

The Subfoundation, — The foundation consists of a
layer of loose material, such as broken stone, gravel,
or cinders, spread over the subgrade and well tamped to
secure a firm base for the main foundation of concrete
which is placed on top. It is most important that the
subfoundation be well drained to prevent the accumula-
tion of water, which, upon freezing, would lift and crack
the walk. For this purpose it is well to provide drain
tile at suitable points t6 carry off any water which may
collect under the concrete. An average thickness for
subfoundation is 4 to 6 inches, although in warm cli-
mates, if the ground is firm and well drained, the sub-
foundation may only be 2 to 3 inches thick or omitted
altogether.

The Foundation. — The foundation consists of a layer
of concrete deposited on the subfoundation and carry-
ing a surface layer or wearing kjoat of cement mortar. If
the ground is firm and the subfoundation well rammed
in place and properly drained, great strength will not be
required of the concrete, which may, in such cases, be
mixed in about the proportions 1-3-6, and a depth of only
3 to 4 inches will be required. Portland cement should

354

CEMENTS AND CONCRETES

be used and stone or gravel under 1 inch in size, the con-
crete being mixed of medium consistency, so that
moisture will show on the surface without excessive
tamping.

The Top Dressing or Wearing Surface. — To give a
neat appearance to the finished walk, a top dressing of
cement mortar is spread over the concrete, well worked
in, and brought to a perfectly smooth surface with
straightedge and float. This mortar should be mixed
in the proportion 1 part cement to 2 parts sand, sharp
coarse sand or screenings below one-fourth inch of some
hard, tough rock being used. The practice of making
the concrete of natural cement and the wearing surface
of Portland is not to be commended, owing to a tendency
for the two to separate.

Details of Construction. — ^A cord stretched between
stakes will serve as a guide in excavating, after which
the bottom of the trench is well consolidated by ram-
ming; any loose material below subgrade is then spread
over the bottom of the trench to the desired thickness
and thoroughly compacted. Next, stakes are driven
along the sides of the walk; spaced 4 to 6 feet apart,
and their tops made even with the finished surface of
the walk, which should have a transverse slope
of one-fourth inch, to the foot for drainage. Wooden
strips at least 1^4 inches thick and of a suitable depth
are nailed to these stakes to serve as a mould to concrete.
By carefully adjusting these strips to the exact height of
the stakes they may be used as guides for the straight--
edge in levelling off the concrete and wearing surface.
The subfoundation is well sprinkled to receive the con-
crete, which is deposited in the usual manner, well
tamped behind a board set vertically across the trench.

HOW TO USE THEM 355

and levelled off witli a straightedge as shown in Fig. 7,
leaving one-half to 1 inch for the wearing surface.
Three-eighths inch sand joints are provided at intervals
of 6 to 8 feet to prevent expansion cracks, or, in case of
aettlement, to confine the cracks to these joints. This is
done either hy depositing the concrete in sections, or by
dividing it into such sections with a spade when soft and
filling the joints with sand. The location of each joint
is marked on a wooden frame for future reference.

Care must be exercised to prevent sand or any other
material from being dropped on the concrete, and thus
preventing a proper union with the wearing surface. No
(section should he left partially completed to be finished
with the next batch 4>r left until the next day. Any con-
crete left after the completion of a section should be
mixed with the next batch.

It is of the utmost importance to follow up closely the
concrete work with the top dressing in order that the

356

CEMENTS AND CONCRETES

two may set together. This top dressing should be
worked well over the concrete with a trowel, and levelled
with a straightedge (No. 7) to secure an even surface.
Upon the thoroughness of this operation often depends
the success or failure of the walk, since a good bond be-
tween the wearing surface and concrete base is absolute-
ly essential. The mortar should be mixed rather stiflf.
As soon as the film of water begins to leave the surface,
a wooden float is used, followed up by a plasterer's
trowel, the operation being similar to that of pla^itering
a wall. The floating, though necessary to give a smooth
surface, will, if continued too long, bring a thin layer of
neat cement to the surface and probably cause the walk
to crack.

Jointer used in dividing walk
into sections.

NO. a

The surface is now divided into sections by cutting en-
tirely through, exactly over the joints in the concrete.
This is done with a trowel guided by a straightedge,
after which the edges are rounded off with a special tool
called a jointer, having a thin shallow tongue (No. 8).
These sections may be subdivided in any manner desired
for the sake of appearance.

A special tool called an edger (No. 9) is run round the
outside of the walk next to the mould, giving it a neat
rounded edgie. A toothed roller (No. 10) having small

HOW TO USE THEM 357

projections on its face is frequently used to produce
slight indentations on the surface, adding somewhat to

the appearance of the walk. The completed work must
be protected from the sun and kept moist by sprinkling

for several days. In freezing weather the same precau-
tions should be taken as in other classes of eoncrete
work.

358 CEMENTS AND CONCRETES

Concrete Basement Floors. — ^Basement floors in dwell-
ing houses as a rule require only a moderate degree of
strength, although in cases of very wet basements, where
water pressure from beneath has to be resisted, greater
strength is required than would otherwise be necessary.
The subf oundation should be well drained, sometimes re-
quiring the use of tile for carrying off the water. The
rules given for constructing concrete sidewalks apply
equally well to basement floors. The thickness of the
concrete foundation is usually from 3 to 5 inches, ac-
cording to the strength desired, and for average work a
1-3-6 mixture is suflSciently rich. Expansion joints are
frequently omitted, since the temperature variation is
less than in outside work, but since this omission fre-
quently gives rise to unsightly cracks, their use is recom-
mended in all cases. It will usually be sufficient to
divide a room of moderate size into four equal sections,
separated by ^ inch sand joints. The floor should be
given a slight slope toward the center or one corner, with
provision at the lowest point for carrying off any water
that may accumulate.

Concrete Stable Floors and Driveways. — Concrete
stable floors and driveways are constructed in the same
general way as basement floors and sidewalks, but with
a thicker foundation, on account of the greater strength
required. The foundation may well be 6 inches thick,
,with a 10 inch wearing surface. An objection often
sometimes raised against concrete driveways is that they
become slippery when wet; but this fault is in a great
measure overcome by dividing the wearing surface into
small squares about 4 inches on the side, by means of tri-
angular grooves % of an inch deep. This gives a very

HOW TO USE THEM

359

ueat appearance and furnishes a good foothold for
horses.

Concrete Steps, — Concrete may be advantageously
used in the construction of steps, particularly in damp
places, such as areaways and cellars of houses, and in
the open, where the ground is terraced, concrete steps
and walks can be made exceedingly attractive. Where
the ground is firm it may be cut away as nearly as pos-
sible in the form of steps, with each step left two or
three inches below its finished level. The steps are
formed, beginning at the top, by depositing the con-

Bei&forced concrete BteDi*

NO. 11.

Crete behind vertical boards so placed as to give the nec-
essary thickness to the risers and projecting high enough
to serve as a guide in leveling off the tread. Such steps
may be reinforced where greater strength is desired or
where there is danger of cracking, due to the settlement
of the ground.

Where the nature of the ground will not admit of its
being cut away in the form of steps, the risers are

860 CEMENTS AND CONCRETES

molded between two vertical forms. The front one may
be a smooth board, but the other should be a piece of
thin sheet metal, which is more easily removed after tke
earth has been tamped in behind it. A simple method
of reinforcing steps is to place a % inch steel rod in each
comer, and thread these with l^ inch rods bent to the
shape of the steps, as shown in No. 11, the latter being
placed about 2 feet apart. For this class of work a rich
Portland cement concrete is recommended, with the use
of stone or gravel under ^ inch in size. Steps may be
given a ^ inch wearing surface of cement mortar mixed
in the proportion of 1 part cement to 2 parts sand. This
system, as well as many others, is well adapted for stair-
ways in houses.

Reinforced Concrete Fence Posts. — Comparison of dif-
ferent Post Materials: There is a constantly increasing
demand for some form of fence posts which is not sub-

ject to decay. The life of wooden posts is very limited,
and the scarcity of suitable timber in many localities
has made it imperative to find a substitute. A fence
post, to prove thoroughly satisfactory, must fulfil three
conditions: (1) It must be obtainable cost; (2) it must
possess sufficient strength to meet the demands of gen-
eral farm use; (3) it must not be subject to decay, and
must be able to withstand successfully the effects of
water, frost and fire. Although iron posts of various
designs are frequently used for ornamental purposes,
their adoption for general farm use is prohibited by their
excessive cost. Then, too, iron posts exposed to the
weather are subject to corrosion, to prevent which neces-
sitates repainting from time to time, and this item will
entail considerable expense in cases where a large num-
ber of posts are to be used.

HOW TO USE THEM 361

At the present time the materials which seems most
nearly to meet these requirements is reinforced con-
crete. The idea of constructing fence posts of concrete
reinforced with iron or steel is by no means a new one,
but, on the contrary, such posts have been experimented
with for years, and a great number of patents have been
issued covering many of the possible forms of reinforce-
ment. It is frequently stated that a reinforced con-
crete post can be made and put in the ground for the
same price as a wooden post. Of course this will de^
pend in any locality upon the relative value of wood and
the various materials which go to make up the concrete
post, but in the great majority of cases wood will prove
the cheaper material in regard to first cost. On the
other hand, a concrete post will last indefinitely, its
strength increasing with age, whereas the wooden post
must be replaced at short intervals, probably making it
more expensive in the long run.

In regard to strength, it must be borne in mind that
it is not practicable to make concrete fence posts. as
strong as wooden posts of the same size ; but since wooden
posts, as a rule, are many times stronger than is -neces-
sary, this difference in strength should not condemn the
use of reinforced concrete for this purpose. Moreover,
strength in many cases is of little importance, the fence
being used only as a dividing line, and in such cases
small concrete posts provide ample strength and present
a very uniform and neat appearance. In any case, to
enable concrete posts to withstand the loads they are
called upon to carry, sufficient strength may be secured
by means of reinforcement, and where great strength is
required this may be obtained by using a larger post
with a greater proporticm of metal and well braced, as

I 362 CEMENTS AND CONCRETES

is usual in such cases. In point of durability, concrete
is unsurpassed by any material of construction. It offers
a perfect protection to the metal reinforcement and is
not itself affected by exposure, so that a post constructed
of concrete reinforced with steel will last indefinitely and
require no attention in the way of repairs.

Reinforcement. — ^No , f i)rm of wooden reinforcement,
either on the surface or within the post, can be reconi-
mended. If on the surface, the wood will soon decay^
and if a wooden core is used it will, in all probability,
swell by the absorption of moisture and crack the post.
The use pf galvanized wire is sometimes advocated, but
if the post is properly constructed and a good concrete
used, this precaution against rust will be unnecessary,
since it has been fully demonstrated by repeated tests
that concrete protects steel perfectly from rust. If
plain, smooth wire or rods are used for reinforcement
they should be bent over at the ends or looped to pre-
vent slipping in the concrete. Twisted fence wire may
usually be obtained at a reasonable cost and is very well
suited for this purpose. Barbed wire has been proposed
and is sometimes used, although the barbs make it ex-
tremely difficult to handle. For the sake of economy the
smallest amount of metal consistent with the desired
strength must be used, and this requirement makes it
necessary to place the reinforcement near the surface,
where its strength is utilized Jto greatest advantage, with
only enough concrete on the outside to form a protective
covering. A reinforcing member in each corner of the
post is probably the most efficient arrangement.

Concrete for Fence Posts, — The concrete should be
mixed with Portland cement in about the proportions
1-2^-5, broken stone or gravel under ^ inch- being osed

HOW TO USE THEM 363

In cases where the aggregate .^tains piecea smaller
than y^ inch, less sand may be used, and in some eases
it may he omitted alt(^t;her. A mixture of meditun con-
sifitency is recommended on the ground that it fills the
molds better and with leas tamping than if mixed quite
dry.

Molds for Fence Posts. — Economy points to the use
of a tapering post, vhich, fojtunately, offera no diffi-
culties in the way of molding. All things considered.

wooden molds will be found most suitable. They can
easily and quickly be made in any desired form and size.
Posts may be molded either in a vertical or horizontal
position, the latter being the simpler and better method.
If molded vertically a wet mixture is necessary, requir-
ing a longer time to set, with the consequent delay in
removing the molds. No. 12 shows a simple mold, which
luts been used with satisfactory results in this laboratory.

364 CEMENTS AND CONCRETES

This mold has a capacity of four posts, but larger molds
could easily be made on the same principle. It consists
of two end pieces, (a) carrying lugs, (b) between which
are inserted strips (c). The several parte are held to-
gether with hooka and eyes, as shown in No. 12. To pre-
vent any bulging of the side strips they are braced, as
illustrated. Dressed lumber at least 1 inch thick, and
preferably 1^ inches, should be used. In No. 12 the

post measures 6 by 6 inches at the bottom, 6 by 3 at the
top, and 7 feet in length, having two parallel sides. If
it is desired to have the posts square at both ends the
mold must be arranged as in No. 13. This latter form
of post is not as strong as the former, but requires leas
concrete in ite construction. Great care in tamping is
necessary to insure the comers of the mold being well

HOW TO USE THEM 365

filled, and if this detail is not carefully watched, the
metal, being exposed in places, will be subject to rust.

Attaching Fence Wires to Posts. — Various devices have
been suggested for attaching fence wires to the posts, the
object of each being to secure a simple and permanent
■fastener or one admitting of easy renewal at any time.
Probably nothing will answer the purpose better than a
long staple or bent wire well embedded in the concrete,
being twisted or bent at the end to prevent extraction.
Qalvanized metal must be used for fasteners, since they

D«U1I tbowlng iMtbod of It'
taching vlra to peat
NO. 14.

are not protected by the concrete. A piece of small flex-
ible wire, about two inches in length, threading the staple
and twisted several times with a pair of pliers, holds the
line wire in position. (No. 14.)

Molding and Curing Posts. — For the proper method of
mixing concrete see previous pages. It is recommended
that only so much concrete be mixed at one time as can
be used before it b^ns to harden; but if an unavoidable
delay prevents the posts being molded until after the

366 CEMENTS AND CONCEETES

concrete has begun to set> it is thought that a thorough
regauging with sufficient water to restore normal con-
sistency will prevent any appreciable loss of strength,
though the concrete may have been standing one or two
hours. In using a mold similar to those illustrated in
Nos. 12 and 13 it is necessary to provide- a perfectly
smooth and even platform of a size depending upon the
number of posts to be molded. A cement floor if accessi-
ble may be used to advantage. ' The molds when in place
are given a thin coating of soft soap, the platform or
cement floor, serving as bottom of mold, being treated in
the same way. About 1% inches, is spread evenly over
the bottom and carefully tamped, so as to reduce it to a
thickness of about 1 inch. A piece of board cut as in
No. 12 will be found useful in leveling oflf the concrete to
the desired thickness r%|ore tamping. On top of this
layer two reinforcing mefiibers are placed about 1 inch
from the sides of the mold. The molds are then filled
and tamped in thin layers to the level of the other two
reinforcing members, the fasteners for fence wires being
inserted during the operation. These reinforcing mem-
bers are adjusted as were the first two, and the remain-
ing 1 inch of concrete tamped and leveled off, thus com-
pleting the post so far as molding is concerned. To avoid
sharp edges, which are easily chipped, triangular strips
may be placed in the bottom of mold along the sides, and
when the molds have been filled and tamped, similar
strips may be inserted on top. The top edges may be
beveled with a trowel or by running an edging tool hav-
ing a triangular projectioji on its bottom along the edges.
Such a tool is shown in No. 15, and can easily be made
of wood or metal. It is not necessary to carry the bevel
below the ground line.

HOW TO USE THEM 367

The ends and sides of the mold may be removed after
twenty-four hours, but the posts should not be handled
for at least one week, during which time they must be
well sprinkled several times daily and protected from sun
and wind. The intermediate ^^trips may be carefully
withdrawn at the end of two or three days, but it is bet-
ter to leave them in place until the posts are removed.
Although a post may be hard and apparently strong
when one week old^ it will not attain its full strength in
that length of time, and must be handled with the utmost
care to prevent injury. Carelessness in handling green'
posts frequently results in the formation of fine cracks,
which though unnoticed at the time, give evidence of
their presence later in the failure of the posts.

Tool lued for l)eTeliiig edgcsof
posts.

NO. 16.

Posts should be allowed to cure for at least sixty days
before being placed in the ground, and for this purpose
it is recommended that when moved from the molding
platform they be placed upon a smooth bed of moist sand
and protected from the sun until thoroughly cured. Dur-
ing this period they should receive a thorough drench-
ing at least once a day.

368 CEMENTS AND CONCEETES

The life of the molds will depend upon the care with
which they are handled. A coating of mineral oil or
sheUac may be used instead of soap to prevent the cement
from sticking to the forms. As soon as the molds are
removed they should be cleaned with a wire^ brush before
being used again.

The cost of reinforced concrete fence posts depends
in each case upon the cost of labor and materials, and
must necessarily vary in diflferent localities. An esti-
mate in any particular case can, be made as follows: One
cubic yard of concrete will make twenty posts measuring
6 inches by 6 inches at the bottom, 6 inches by 3 inches
at the top, and 7 feet long, and if mixed in the propor-
tions 1-2^-5, requires approximately :

1.16 barrels of cement, at $2 $2.32

0.44 cubic yard of sand, at 75 cts ; .33

0.88 cubic yard of gravel, at 75 cts. 66

Materials for 1 cubic yard cement $3.21

Concrete for one post 17

28 feet of 0.16 inch steel wire, at 3 cts a pound 06

Total cost of concrete and metal for 1 post 23

To this must be added the cost of mixing concrete,
molding and handling posts, and the costs of molds, an
addition which should not in any case exceed 7 cents,
making a total of 30 cents per post.

Concrete Building Blocks, — Concrete building blocks,
or cement blocks, as they are frequently called, are more
extensively used now than ever before. These blocks
are molded hollow primarily to reduce their cost, but
this hoUow construction serves other useful purposes at
the same time. The fundamental principles governing

HOW TO USE THEM 369

ordinary concrete work, so far as proportioning and
mixing materials is concerned, apply equally well to the
manufacture of building blocks, and it should be borne
in mind that strength and durability can not be obtained
by the use of any machine unless the cement, sand, and
aggregate are of good qualify, properly proportioned
and well mixed. The aggregate for blocks of ordinary
size should be crushed stone or gravel not larger than
% inch. One of the chief causes of complaint against
the concrete building block is its porosity, but this defect
is in a great measure due to the fact that in an endeavor
to economize too little cement is frequently used. It is
not unusual to give the blocks a facing of cement mor-
tar consisting of about 2 parts sand to 1 of cement, while
the body of the block is composed of a concrete of suffi-
cient strength, though not impervious. This outside
layer of mortar adds practically nothing to the strength
of the block, and is used simply to give a uniform sur-
face and to render the f £tce of the wall more clearly im-
pervious to water.

It would not be practicable as a rule to attempt the
manufacture of concrete blocks without one of the many
forms of molding machines designed for the purpose, noi
would it be economical to purchase such a machine un-
less a sufficient number of blocks were required to juistify
such an outlay. Blocks in almost any desired shape and
size, with either plain or ornamental faces, may be ob-
tained on the market^ and in the great majority of cases
it is best to buy them from some reliable firm. Among
the advantages claimed for hollow concrete block con-
struction may be mentioned the following :

(1) Hollow block construction introduces a saving of
material over brick or stone masonry.

370 CEMENTS AND CONCRETES

(2) The cost of laying concrete blocks is less than for
brick work. This is due to the fact that the blocks, being
larger, require a much smaller number of joints and
less mortar, and, being hollow, are of less weight than
solid brick work.

(3) A wall constructed of good concrete blocks is as
strong or stronger than a brick wall of equal thickness.

(4) Concrete blocks, being easily molded to any de-
sired f oi'm, will prove to be a far more economical build-
ing material than stone, which has to be dressed to
shape.

(5) Experience has proved concrete to be a most ex-
cellent fire resisting material.

(6) Concrete blocks, being hollow, tend to prevent
sudden changes of temperature within a house, making
it cool in summer and easily heated in winter.

(7) The hollow spaces provide an easy means for
running pipes and electric wires. These spaces may also
be used wholly or in part for heating and ventilating
flues.

Tests of Concrete Fence Posts. — ^In the summer of
1904 a number of reinforced concrete fence posts were
made for experimental purposes, with a view to deter-
mining their adaptability for general use. These posts
were made both with and without reinforcement, and
tested at the age of 90 days. The reinforcement, rang-
ing from 0.27 per cent, to 1.13 per cent., consisted of
four round steel rods, one in each comer of post about
1 inch from surface, the posts having a uniform cross-
section of 6 by 6 inches. The posts were molded in a
horizontal position, as this was found by trial to be more
satisfactory than molding them vertically.

HOW TO USE THEM 371

The concrete was mixed moderately soft, crushed stone
between 1 inch and ^ inch and gravel under % inch
being used as aggregate. River sand, fairly clean and
sharp, was employed with Portland cement. The posts
■were tested as beams, supported at both ends and loaded
at the centre, with spans varying from 4 feet to 5 feet 6
inches. An attempt was made to prevent slipping by
providing the reinforcmg rods with collars and set
screws at the ends, but in every case, with but two ex-
ceptions, the rods slipped under a comparatively light
load, thus showing the necessity for some form of me-
chanical bond. As would be expected, those posts which
were not reinforced possessed very little strength.

[

W<ri ' -^^^ — ^

Method of testing
poeoi mider static loads.

A series of tests was made with gfteet-iron reinforce-
ment, in the form of round and square pipes, embedded
in- the posts, but these posts, though developing consid-
erable strength, proved less economical than those rein-
forced with plain rods, and at the same time were less
simple in construction. The results of these tests, as re-
corded in Table I., do not properly represent the strength
of similar posts in which some form of mechanical bond
16 provided to develop the full strength of the reinforce-
ment.

372

CEMENTS AND CONCRETES

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HOW TO USE THEM

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374 CEMENTS AND CONCRETES

In order to obtain more data on the subject, this in-
vestigation has been supplemented by a second series of
tests, the results of which form the subject matter for
the sections on concrete fence posts and are expressed
numerically in Table II.

In these tests it was decided to make the posts taper-
ing in order to economize material and reduce their
weight. For the concrete, Portland cement, river sand,
and gravel were used in the proportion 1-21^-5, meais-
ured by volume, the gravel being screened below ^^ inch.
Sufficient water was used in mixing to produce a plastic
mass, requiring only a moderate degree of tamping to
bring water to the surface. The posts were molded and
kept under wet burlap for four weeks, and tested at the
end of sixty days. The reinforcing members were placed
in the corners of the posts about 1 inch from the surface,
being looped and bent, as indicated in Table II. These
posts were not designed with a view to developing the
idtitnate compressive strength of the concrete, but where
greater strength is necessary it may be obtained at small
expense by increasing the percentage of reinforcement.
It is important that fairly rich concrete should be used
in all cases to enable the posts to stand exposure and to
prevent chipping.

All of these posts measured 6 by 6 inches at the
bottom and 6 by 3 inches at the top, except Nos. 29,
30, 31, 32, 33, and 34, which were 6 by 6 at the
bottom and 3 by 3 at the top. It will be noticed that the
saving in concrete introduced in the construction of these
posts is accompanied by a marked decrease in strength
as compared with the other posts similarly reinforced.
It would also appear that the twisted wire has a slight

HOW TO USE THEM

375

TA3I.E II. Showing the Strength op Reinforced

Concrete Fence Posts.

No,

•28

.86

B[ind of rein-
forcement.

Draivn steel rods

Twisted fenM wire

Barbed wire

• • • • • vUx/ •••• •••••

• ••••• vtU •••••••••

do...

Drawn steel rods

......do :

Twisted fenes wire

4a
«

o
on

ea «

ea 0
e3 oQ

3*-*

*»

0.08
.08
.08
.08
.08
.08
.19
.19
.19
.19
.19
.06
.06
.06
.06
.06
.06
.13
.13
.13
.13
.06
.06
.06
.06
.06
.06
.06
.06
.13
.13
.13
.13
.08
.19
.19
.06

.06

800

820

640

795

940

740

1140

1170

1020

760

820

825

755

800

815

770

780

1550

1275

1200

1500

980

820

590

745

590

550

560

480

680

840

1280

800

1120

1145

1080

1040

1170

1075

1280-

1885

1950

1945

1925

935

905

940

935

980

975

1920

1670

1830

1955

980

820

740

745

590

640

635

530

1040

1010

1515

1375

Tested by

do..

>
« .

^ s

s •

■d ea
ea »4
oo

a tJ
gca

ea os

218
224
175
217
257
202
311
319
278
207
224
225
206
218
222
210
213
423
348
328
410
268
224
161
203
161
160
153
131
186
229
349
218
impact

a .
OS

•a^

ea
o b

'-'04

M o
ea >.

l§
ea

306
313
295
284
319
293
349
515
532
531
526
255
247
257
255
268
266
524
456
500
534
268
224
202
203
161
175
173
145
284
276
414
875

Form of reinforcement.

.do

4b.

i« »■■■■>■■

376 CEMENTS AND CONCRETES

advantage over the barbed wire as a reiaforeing material,
particularly when two wires are used in each comer of
the post.

As stated before, it ia impracticable to make a rein-
forced concrete fence post as strong as a wooden post of
the same size, and this is more especially true if the post

by Impact.
NO. IT.

has to withstand the force of a sudden blow or impact.
In order to study the behavior of these posts under im-
pact, a number of them were braced, as illustrated in
No. 17, and subjected to the blow of a 50-pound bag of
gravel, suspended from abo^e by a 9-foot rope. The
first blow was delivered by deflecting the bag so as to
give it a vertical drop of 1 foot, and for each successive

HOW TO USE THEM 377

blow the drop was increased 1 foot. None of the posts
showed any signs of failure under the first blow. Posts
Nos. 14 and 20 cracked under the second blow, and failed
under the third. Post No. 6 cracked under the second
blow, which cracked open under the third blow, causing
a momentary deflection of 5 inches. Posts Nos. 7 and 8
eaxsh developed a crack under the second blow, but
showed no further signs of weakness after the fifth blow.

*•..

^--.

'-.

"*«.

I ■■•;.■•••■■■•• -■^■<■■1l..•.■^/<a:■:.a..'J■>?TaJ»^■.■^v:^f.v.■.■.■■v.v w

Second method of testing
posts by impact.

NO. 18.

other than a slight opening of the initial crack. In each
case the only crack developed was at point A. Posts 6,
7, and 8, which cracked biit did not fail under the im-
pact test, were further tested, as indicated in No. 18, by
raising the small end and allowing them to drop from
successive heights at 1, 2, 3 and 4 feet. Under this test
a number of cracks developed, but in no case did the re-
inforcement fail.

Although it might appear from these results that posts
as here described have hardly enough strength to recom-
mend them for general use, it should be remembered that
in many cases fence posts are not subjected to impact.

378

CEMENTS AND CONCRETES

and it may prove more economical to replace from time
to time those which fail in this way than to use wooden
posts, which, being subject to decay, must all be replaced
sooner or later.

Diagram showing the effect of clay on cement mortars.

NO. 19.

Retempering, — Table III. illustrates the effect of re-
tempering Portland cement mortar. The mortars used
consisted of Portland cement and crushed quartzite be-
tween 1 and 2 millimeters in size, mixed in different pro-

HOW TO USE THEM

379

portions. In each case, after the initial or final set had
taken place, sufficient water was added in retempering to

TABLE in. — ^Effect of Ebtemperinq on Cement Mortabs.

Tensile StrenRtb, in Pounds Per
Square Inch.

Treatment of Mortar.

Neat

Cement.

IPart

Oement,

IPart

Sand, b

IPart
Cement,
2 Parts
Sand, c

IPart
Cement,
3 Parts
Sand.d

Mortar made up into briquettes .
immediately after mixing

651
650
673
634
679

624
701
624
581
610

527
493
529
480
492

417

885
421
403
409

Average .'.......

657

628

504

407

Mortar allqwed to take initial
s^t, then broken up and made
into briquettes

671
593
644
633
724

692

670

"654

676

700

589
554
559
534
532

326

349

330.

358

267

Average

653

678

554

326 -.i.

Mortar allowed to take final
set, then broken up and
made into briquettes

455
522
525
558
642

527
569
587
566
568

492
491
497
486
531

364
380
361
315

345

Average

540

563

499

353

a Initial set, 1 hour 42 minutes; final set, 7 hours 15 minutes.
h Initial set, 1 hour 80 minutes* final set. 7 hours 15 minutes,
e Initial set, 2 hours; final set, 7 hours.
d Initial set, 2 hours 20 minutes; final set, 7 hours.

restore normal consistency. The briquettes were tested
at the age of four months.

380 CEMENTS AND CONCRETES

Some Practical Notes. — Spencer B. Newbury, who is
an authority on the subject, says **that the making of
good cement concrete is a comparatively simple matter,
and yet, like most simple operations in engineering, there
is a right way and a wrong way of doing it. Probably
nine-tenths of the concrete work done falls far short of
the strength it might develop, owing to the incorrect pro-
portions, use of too much water, and imperfect mixing.
All authorities are agreed upon the importance of thor-
ough mixing and the use of the minimum quantity of
water in all classes of concrete work. The matter of cor-
rect proportions of cement, sand, broken stones, etc., is
one which requires some thought and calculation, and by
proportioning these ingredients correctly an immense
saving in cost and increase in strength can easily be se-
cured.

The chief object in compounding concrete is to pro-
duce a compact mass, as free as possible from pores or
open spaces ; in short, to imitate solid rock as closely as
possible. Cement is the ** essence of rock" in portable
form, and by its judicious use granular or fragmentary
materials may be bound together into solid blocks of any
desired size and shape, which in strength and wearing
qualities are at least equal to the best stone that comes
from the quarries. Cement is, however, very costly in
comparison with the other ingredients of concrete, and
must not be used wastefully. A little cement, judi-
ciously used, is better than a large quantity thrown in
recklessly, as a little study of the principles involved
will plainly show.

To produce a compact mass from fragmentary ma-
terials, the voids must be filled. Imagine a box holding 1
cubic foot. If this were filled with spheres of uniform

HOW TO USE THEM 381

size, the voids or open spaces would be one-third the total
volume, or 33 1-3 per cent., with spheres of various sizes,
as, for example, from large marble down to fine shot, the
voids would be niueh less, and it would theoretically be
possible, by the use of spheres of graded sizes, from the
largest down to dust of infinite fineness, to fill the box
completely, so that there would be no voids whatever. In
practice it is well known that the use of materials of
varying fineness gives the best concrete, since the voids
are much less than in materials composed of pieces of
uniform size. Hence the common practice of making
concrete with cement, sand and broken stone, instead of
with cement and sand, or cement and stone only. The
sand fills the voids, and if the proportions are correct, a
practically solid mass results. As an example of this,
the writer found the briquettes of cement with three
parts of sand and four parts gravel showed higher ten-
sile strength at 28 days than those made with three parts
sand only.

The following table gives the relative weights of a
given volume of different materials, and also the per-
centage of voids, as determined by the writer. The ma-
terials were shaken down in a* liter measure by giving
one hundred taps on the table, and weighed. In the case
of the broken stone a larger measure was used. The
voids were calculated from the specific gravity.

Comparison of the three diflferent grades of Sandusky
Bay sand shows how greatly the percentage of voids
varies with the proportion of fine and coarse grains pres-
ent. The first is the natural sand, not screened, as
pumped up by the sand sucker from the bottom of the
bay, and contains a large amount of fine gravel. The
second is the same, passed through a 20-mesh screen to

382

CEMENTS AND CONCRETES

remove the coarse particles. It will be seen that this
operation increases the proportion of voids from 32 to
38 per cent. The third is the same sand passing a 20-
mesh and retained on a 30-mesh screen, thus brought to
the fineness of the ** standard sand'' used in cement test-
ing. This shows 40.7 per cent, of voids, owing to the uni-
form size of the grains. The same relation is seen in the

WEIGHT OF UNIT MBASURB AND PBRCBNTAGB OP VOIDS IN

VARIOUS MATERIALS.

Portland cement

Louisville cement

Sandusky Bay sand, not screened

Sandusky Bay sand, through 20-mesh

screen

Sandusky Bay sand, 20-80 mesh (standard

sand)

Gravel, /i to % inch

Gravel, Ji to yV inch

Marblehead broken stone (chiefly about

egg size) *

Percent

of
Voids.

82.3

88.5

40.7
42.4
85.9

47.0

two grades of gravel given in the table, that containing
finer grains showing much the lower percentage of voids.
These figures illustrate the imprudence of screening
any of the materials used in making concrete. The pres-
ence of clay in sand is, however, objectionable, not be-
cause of its fine state of subdivision, but because the
clay coats the sand particles and prevents the adhesion
of the cement. Such sand might be improved by wash-
ing, but probably not by screening. It has been found

HOW TO USB THEM 383

that cement which has been ground to dust with an equal
amount of sand goes much further when used for con-
crete than the same quantity of cement when used in
the ordinary way. This is doubtless owing to the fact
that the sand dust aids in filling the voids. It is also
well known that slaked lime, when added to cement mor-
tar, greatly increases the strength of mixtures poor in
cement.

From the figures given in the above table the compo-
sition of a theoretically perfect concrete may readily be*
calculated. The existence of voids in the cement may be
disregarded, since in the process of hardenmg the cement
sends out crystals in all directions, completely encrusting
the sand particles and practically filling all the voids
i^hich the cement itself contains. Examination of a
well-hardened briquette of cement with 3 p'arts sand,
after breaking, with the aid of a lens, will show this
clearly

Suppose, for example^ we wish to make the best pos-
sible concrete from Portland cement with the sand and
gravel given in the above table. We should, of course,
choose the unscreened sand and gravel as containing
the least proportion of voids. One hundred measures of
gravel would require 35.9 measures of sand. As the
sand ccmtains 32.3 per cent, of voids, we require 32.3
per cent, of 35.9, or 11.6 measures of cement. The pro-
portions would, therefore, be: Cement, 11; sand, 3, and
gravel, 9. It is customary, however, to increase the pro-
portion of mortar (cement and sand) by about 15 or 20
per cent., in order that the coarser materials may be
completely coated with the finer mixture. Making this
aiddition, we find the concrete proportions to be: Cement,
1 ; sand, 2.8 ; gravel, 7. Allowance must also be made in

384 CEMENTS AND CONCRETES

practice for imperfect mixing, since the materials can
never be distributed in a perfectly uniform manner.
Practically, with these materials, a concrete of cement
1, sand 2y2, and gravel 6, would probably give the best
result, and little or no improvement would resuU from
\ increasing the proportion of cement.

A similar calculation shows that the correct propor-
tions for a concrete made of the sand and broken stone
given in the table would be 1 to 3 to 6^. Increasing
the amount of cement and sand by 20 per cent., we have
1 to 3 to 5^. Probably 1 to 2^^ to 5 would be found to
give the best results in practice. The determination of
the voids in the sand, gravel and broken stone used is
of the greatest value in adjusting the proportions of
concrete. ♦

The simplest method of determining this in the case of
gravel and broken stone is to have a metal box made of
1 cubic foot capacity; this is filled with the material to
be tested, well shaken down and struck oflf level. The
box and contents are then weighed. Water is now
poured in until it rises even with the surface, and the
total weight again taken. The difference in the weights
is the weight of the water filling the voids of the ma-
terial. Now 1 cubic foot of water weighs 64 4-10 lbs.,
and from the weight of the water found the percentage
of voids can be simply calculated. For example, in one
experiment the box and broken stone weighed 88 Ihs.
After filling the spaces in the stone with water the
weight was 1171/2 lbs., a difference of 29i^ lbs. The
percentage of voids is, therefore, 29^x100 divided by
62.4 equals 47 per cent.

In the case of sand this method will not answer, as it
is difl&cult to completely fill the voids of the sand by

HOW TO USE THEM 385

adding the water. The voids can, however, be readily
calculated from the weight of a cubic foot and the spe-
cific gravity. The specific gravity of quartz sand is
about 2.65. A cubic foot of sand, free from voids, would
therefore weigh 2.65x62.4 equaling 165.4 lbs. The
weight of a cubic foot of sand, well shaken down, was,
however, found to be only* 112 lbs., a difference of 53.4
lbs. The proportion of voids was, therefore, 53.4x100
divided by 165.4 equals 32.3 per cent. The percentage
in voids in clean natural sand does not vary greatly, and
may be taken as 33 to 35 per cent, for coarse and 35 to
38 per cent, for fine sand.

We have already seen that with the materials above
described, concrete composed of

Cement 1, sand 2^^, gravel 6, or

Cement 1, sand 2^, broken stone 5
by measure, will be practically compact and non-porous,
and that there is no object in increasing the proportion of
cement. Such concrete, if made from Portland cement,
will, however, be rather expensive, requiring about one
barrel of cement (equals 3^/^ cubic feet) for every cubic
yard. This is unnecessarily good for ordinary work, and
will only be required for foundations of engines and
other heavy machinery, in which the best possible result
must be secured regardless of cost. In cheaper concretes
the relative proportions of sand and broken stone should
be the same, as determined by the voids in the coarser
materials, while the proportion of cement may be varied
according to the required conditions of quality and cost.
Most excellent concrete* may be made by using:

Portland cement 1, sand 7, stone or gravel 14.

Here are specimens of these two concretes, taken from
trial blocks laid Oct. 1, 1894, to determine the best pro-

386

CEMENTS AND CONCRETES

portion for the foundation of brick pavement. The
richer of the two, 1-5-10, is certainly good enough for
any purpose, even for engine foundations. A cubic yard
of such concrete requires about ^ barrel of cement ; the
total cost of the cement, sand and stone is about two
dollars per cubic yard. This is no more expensive than
concrete mad6 from Louisville cement with 2 of sand
and 4 of broken stone, and is immensely superior to the
latter in strength.

The following table shows the results obtained in
Germany by R. Dykerhoff in determining the crushing
strength of various concretes. The blocks used were 2^/^
inches square, and were tested aftei;* one day in air €uid
27 days in water.

Proportions by Measure.

X ,

Strength xmder OompresBion.

Portland
Cement.

Sand.

Grayel.

Pounds per Square Inch.

• •

2125

2747

2387

• •

978

••

1888

1632

1515

• •

1058

1278

1204

These figures prove the statement already made, that
mixtures of cement and sand are strengthened, rather
than Weakened, by the addition of a suitable quantity
of gravel. It will be noticed that the mixture — cement 1,

. HOW TO USE THEM 387

sand 2, gravel 5 — ^is actually stronger than cement 1,
sand^ 2, without gravel. The same is shown in the mix-
tures 1 to 3 and 1 to 4.

In estimating the amount of material required to pro-
duce a given volume of concrete, it may be stated that
when very strongly rammed into place the volum<3 of
concrete obtained from correct proportions of the ma-
terials will be about 10 per cent, more the volume 1 cubic
foot cement, 2^ cubic feet sand, and 5 cubic feet stone,
and will therefore yield about 5^^ cubic feet concrete.

Another Concrete Stairway and Steps, — A good stair-
case is one of the essential features in a building. The
safety and convenience of persons using a staircase are
not only affected by the due proportions and arrange-
ments of the steps, but by the strength and fire-resisting
properties of the materials employed, and the manner of
construction. The wells are in many cases too small,
out of proportion to the structure, which necessitates
dangerous winders, tiring high risers, narrow treads, or
insuffieient headway. Some architects when designing a
staircase pay little attention to the practicability of con-
struction. What may seem easy in theory or on paper
is often fouad impracticable or unnecessarily difiicult
when reduced to actual practice. The errors of omission
and commission are left for the workmen to contend
with and overcome as best they may at the employer's
expense. Happily such cases are few, the majority of
architects supplying figured drawings, which are not
. only a help and guide to the workmen, but also ensure
a practical staircase in due proportion and without un-
necessary expense. Staircases should be spacious, light,
and easy of ascent. It is generally admitted that a 12
inch tread and a 6 inch rise is the most convenient, and

388 CEMENTS AND CONCRETES

that no tread should be less than 8 inches or more than
16 inches, and no rise less than 4^ inches and more than
7 inches. According to Blondel, the rise- should be re-
duced ^ inch for every inch added to the tread, or the
tread reduced by 1 inch to every % inch added to the
riser, taking a 12 inch tread and a 6 inch rise as the
standard. Treads may be increased by means of a nos-
ing, which usually projects from 1 inch to 1^ inches.
Nosing not only gives more available space for the tread,
but also affords some advantage to persons going down
stairs, as the heel cannot strike against the rising. In
setting out a flight of stairs, the tread of the steps are
measured from riser to riser. Where practicable, the
number of steps from landing to landing should be odd,
because when a person begins to ascend with the right
foot first (as most people do) he should end with the
same foot. Rectangular steps are called fliers. Wind-
ers, being narrowed at one end, are always more in-
convenient and dangerous than straight steps, and
should not be used for public buildings or other places
where there is a crowded traffic. Winders are also
more expensive to construct. They are, however, un-
avoidable in circular staircases, also in some instances
in angles, where a quarter or half space landing would
not give the desired rise. Winders should be so made
that the tread 6 inches from the end of the narrow
point should be wide enough to step upon without dan-
ger of slipping. No stairs should be less than -three
feet from the wall to the hand-rail. A width of 3 feet
6 inches will allow two persons to walk- arm in arm up or
down stairs. A width of 4 feet 6 inches is generally nsed;
this gives plenty of space for two persons to pass each
other. No hard and fast rules can be laid down for the

HOW TO USE THEM 389

gize of treads and risers, as they are regulated more
or less by the size of the well and the height from floor
to floor. Too few steps in a flight are as bad as too
many. There should not be less than three. Long
straight flights of steps are tiring and dangerous. The
straight line of length should be broken by landings,
so that there may not be more than eleven continuous
steps. Landings give ease in ascending and safety
when descending. No landing should be less in length
than the width of the staircase. The staircases in the
pre-Elizabethan style were usually plain, dark and in
long narrow flights; but with the Elizabethan archi-
tecture came in a more commodious, light and decora-
tive style. Wood stairs are often enriched with plaster
work, the soffits being panelled with plaster, and the
strings adorned with composition or plaster enrich-
ments. Stone stairs are also frequently enriched with
^plaster mouldings in the angles of the sofiits and walls.
External steps and landings are usually made with a
fall of ^/4 iiich to the foot to allow rain to fall oflf.

Cast Concrete Stairs. — Concrete is now fast super-
seding stone, wood and iron for staircase construction,
where strength, durability and economy and fire-resist-
ing, properties are required. Cast concrete stairs were
first ii^troduced nearly sixty years ago. The stairs
were cast in single steps, or in treads or risers, and
fised in the same way as natural stone. Square and
spandrel steps, risers and treads are cast in wood
moulds; circular steps and curtails in plaster moulds.
Spandrel steps should have the wall or ''taiP' end
formed square, and about 4^ inches deep, to give a
better bed and bond in the wall. A good mixture is 3
parts of granite or slag chippihgs and 1 of Portland

390 CEMENTS AND CONCRETES

cement, gauged stiflf, and well rammed into the moulds.
When set they are removed from the moulds, air dried,
and placed in water or a silicate bath, and treaded in
ia similar way to that described for slabs. For long
steps pieces of T iron, or iron pipes, are sometimes in-
serted in the centre of the concrete while being cast
The iron is not actually required to strengthen con-
crete properly made, but is used to give a temporary
strength to the cast while it is green, so as to allow
more freedom and security in handling the cast when
it is being taken from the mould and moved about till
permanently fixed. Landings are cast in a similar way,
but unless very small, they are best done in situ. I
have made landings up to 40 feet superficial, but owing
to the cost of transit, hoisting and fixing they were
not profitable.

Tests of Steps, — The following examples show the
strength of concrete steps: In Germany, when con-
structing a concrete stair, with square steps 3 feet 4
inches long, and 6-inch tread, and 6i^-inch rise, and
one end set 8 inches into the walls, four steps were sub-
mitted for trial, and 5,940 lbs. weight of iron were
gradually piled on them. The steps showed no signs
of fracture, but no more weight could be put on be-
cause the masonry began to yield. The load was left
on three days, and the steps remained unaffected. Al-
though numerous tests have been made- of concrete
floors and blocks, few have been made for concrete
steps. The following may be given as a reliable one:
The steps were about 6 feet long, 11-inch tread and
6-inch rise. Every step was tested in the presence of
the foreman concreter and author. The steps were
supported at both ends, and weighed with a distribu*

HOW TO USE THEM 391

tive load. The majority, which were matured by age,
passed the specification standard.

Concrete Stairs Formed ^Hn Situ.*^ — Concrete stairs
are an outcome of stairs built with cast concrete steps.
Stairs formed in situ were introduced in 1867. The
idea was suggested by the use of reverse moulds for
fibrous plaster work, and in the formation of concrete
dormer windows made in situ on some mansions. The
step landings and the wall bond, being a monolith
structure, were to a certain degree self-supporting.
They tend to strengthen instead of to weaken the
walls. Architects generally supply drawings of the
intended staircase, but as there is often a diflfer-
ence in the size of the details of the actual work and
the drawings, it is necessary that the workman should
have a practical knowledge of setting out the ''height'^
and *'go" for the pitch board, to suit the landings and
the well of the staircase, and ensure the necessary head-
room.

Setting Out Stairs. — ^A correct method of setting out
the framing for concrete stairs is of primary import-
ance. The height of a stair is the length of a per-
pendicular line drawn from the upper of a floor to
that of the one immediately above it. The **go'' is
the length of a horizontal line drawn along the centre
line of the flight of steps or stair space. The exact
height and widths should be taken on a rod, which
should afterwards be used for setting out the work.
Never work without this rod, as it is quicker and more
accurate than measuring with a 2-foot rule. There are
various ways of getting the dimensions of treads and
rises. The following is a simple one and answers for most
purposes. The height and go are taken and suitably

392 CEMENTS AND CONCRETES

divided. For example, if the height from floor line t6
floor line is 9 feet 3 inches, and it is proposed to
make each rise 6 inehies high, reduce the weight to
inches, which would be 111; divide by the proposed
height of each step — 6 inches — ^the quotient will be 18,
giving the same quotient 6 and 3-18. If there are
intermediate landings, or half spaces, their dimensions
must be allowed for. The size of the tread is obtained
by dividing the '*go'' by the number of steps. The
quotient will be the width of the tread. Great care
should be taken in setting out the rods and pitch,
boards. It is better to measure thrice than to cut twice..
When the string line is marked on the wall, a chase
ab6ut 4^/^ inches deep is cut into the wall. It is not
necessarj'^ to cut the chase straight at the sofilt line, as
it is apt to cut into a half, or rather a whole brick,
and leave the ends loose. The irregular line of chase
below the soflSt line can be made solid during the pro-
cess of filling in the steps. The chase should be cut
as the work proceeds. Not more than one flight at a
time should be cut, to avoid weakening the walL In
some instances a brick course in sand is left by the
bricklayers. The bricks are then taken out as the
work proceeds.

Nosings and Risers. — ^Nosing mouldings should -be
strong and bold. A simple but well-defined moulding^
not only gives greater strength, but is more in keep-
ing with its purpose than one with numerous or small
members. Nosing and riser moulds are best formed
in two parts,. the nosing moulds being one part and the
riser board the other. To cut them out of the solid
would not only be expensive, but also cumbrous to fix.
They can be run at most saw and moulding milkk

HOW TO USE THEM

393

They should be run in lengths and then cut and mitred
on the job. Illustration No. 20 shows various forms
of nosing. Fig. 1 is a simple nosing for common work.
Fig. 2 may be used for school stairs, etc. Figs. 3 and
4 are well adapted for a good class of work. It will be
seen that the lower edges of the riser boards are
splayed. This is to admit the shoe of the running
mould; also a trowel to work close up to face of the

Fig. U rig. £ Fig. a. Tig. 4*

••«»

Sections 'o» NojsiNa

IdOULDS WITH KiSER BOARDS.
NO. 20.

concrete riser when running and trowelling off the
treads. The dotted lines indicate the line of tread.
Nosing moulds are cut in the centre of the section, and
afterwards the two parts are held in position with
screws while the steps are being filled in. This allows
the upper part to be unscrewed and taken off when the
stu£f is nearly set, thus allowing more freedom to
trowel the surface of the tread ; also to make a better
joint while the stuff is green, and at the part that is
cast and the part to be trowelled. The joint in the
nosing mould leaves a thin seam which is easily cleaned
off, whereas the joint of the tread and nosing is not
only seen more, but is also more difficult to make good

394 CEMENTS AND CONCRETES

Illustration No. 21 shows the mould and joint end
screws for fixing same.

Framing Staircases. — The wood framing for con-
crete staira differs from and is partly the reverse to
that used for wood staira. The nosings are formed the
reverse of the moulding, and the whole framing is so
constructed that it forms a mould to cast all the steps
and landings, from fioor, iu monolithic form, or one
piece. When the positions of half spaces or other

landings are set out on the walls, strong planks are
fixed on edges so as to give fixing joints for the car-
riage and outer strings. The strings are then fixed
to act as guides for fixing the centring, risers and nos-
ing moulds. Where practicable, the outer string should
be so arranged in the fixing that it can be taken off
after the concrete is firm without disturbing the cen-
tring. This allows the returned ends of the steps to
be cleared off while the work is green. The carriage
boards are fixed from landing to landing. Ulustra-
tion No. 22 shows the forms and positions of the vari-

HOW TO USE THEM

396 CEMENTS AND CONCRETES

ous parts, with their names. Bullnoses or curtails and
circular parts of nosings are formed in plaster moulds,
which are run with several reverse running moulds. -

Staircases between walls are more simple than open
staircases; therefore they are more easy to frame up.
The string boards are cut to the reverse of that used
for wood stairs. A string is cut for each wall. The
riser boards aire then fixed to the wall strings. The
centring for the soffits is fixed independently, the
boards being laid on fillets which are nailed on each
wall. For short flights of steps or common stairs, such
as for cjeliars, etc., stijing boards may be dispensed with.
The positions and sizes of the risers, treads, soffits and
landings are first set out and marked on the walls.
Riser fillets are then nailed on the walls, taking care
to keep each fillet in a line with the riser mark, and
to allow for the thickness of the riser boards which
are subsequently nailed on the iilner sides of the fillets.
Riser boards for winders are generally hung on long
fillets and then nailed on the walls. Long fillets ex-
tending upwards enable the work t6 be easier and more
strongly fixed, as they cover more brick joints than if
cut to the exact height of the riser.

Centring for Landings cmd Soffits. — ^Centring for
landings and the soffits of stairs should be made strong
and true. The timber should be well seasoned, to pre-
vent warping or shrinkage. The outer angles of land-
ings should be supported by strong wood props, not
only to carry another prop for the landing above. All
centrings should be made perfectly rigid, to stand Ute
weight of the concrete and the ramming. Great care
should be taken that the timber framing is securely
supported, as any deflection - will not only throw the

HOW TO USE THEM 397

work out of level, but will also tend to crack the con-
crete. The principal props should be cut about ^
inch shorter than the exact height. They are placed
on a solid bed, the %-inch space at top beiag made
up with two wedges, the thin ends being inserted in
opposite directions and gently driven home ftom each
side until the exact height is obtained. If it is dif-
ficult to get the top of the prop, the wedges can be
inserted at the bottom. The use of the wedges will
be seen when the centring is struck. If there are
winders in the stairs, the centring for the soffit will be
more or less circle on circle. This form of centring
is done by lathing, with 1-inch boards, cut to a taper,
the surface being made fair with a gauged lime and
hair. Rough l^^-inch boards are used for the centring.
This should be close- jointed. Open joints or sappy
timber act as a sieve, and allow liquid cement to drip
through, thus robbing the concrete of its strength.

Waterproof Centring.9 — The following is a method
that has been used with marked success for the sof-
fits of stairs, landings and the ceilings of floors. The
initial cost of preparing is small, and is repaid with
interest by the decreased cost of setting and' the in-
creased strength and solidity. For ordinary work,
such as warehouses, etc., it is very suitable, as a fin-
ished surface is formed, and no setting required. It
seeBof&r strange that, when casting concrete work out of
a wood or a plaster mould, the mould is seasoned, and
every precaution taken, not only to stop suction, but
also to prevent the escape of liquid cement ; but when
casting a large surface in situ (where every precau-
tion should be taken to obtain the maximum of
strength), any kind of centring (which is a mould)

398 CEMENTS AND CONCRETES

is thought good enough, if only sufficiently strong to
carry the concrete till set. I am aware that many-
workers in concrete think that an ' open or porous
centring is a benefit instead of a defect, simply be-
cause it affords an escape for excess of water. But
why have excess of water at all? There is no gain
in time or strength, but a direct loss in both points.
The excess water descends through the concrete by
force of direct gravitation, and always carries a cer-
tain amount of liquid cement with it to the centring,
leaving the aggregate more or less bare, and the body
of the concrete weak. A part of the liquid cement
also oozes through the joints, and crevices, which leaves
the skin of the concrete bare and broken. There is
no reason or excuse for excess water, and it is simply
the result of ignorant or careless gauging, which is not
only a waste of time, water and cement, but a- loss in
the ultimate strength, and the cause of cracks. Porous
centring is also a dirty process. The overhead drip.
drip, is neither good for the workmen nor the material
underneath.

The process of forming the rough centring boards
watertight is simple and expeditious, being done by
laying the rough board surface with a thin coat of
gauged plaster ; and when the centring has been struck
the plaster will come with the boards, leaving the con-
crete with a fair face. The ramming forces a certain
amount of water to the lower surface or centring, and
this is so close and fine that it takles an exact impress
of it ; consequently the truer and smoother the centring
the truer and smoother the concrete surface. The film
of water indurates the skin of the concrete and prevents
surface or water cracks. It will be noticed when filling

HOW TO USB THEM 399

in dry or porous plaster moulds that the concrete cast
produced has' a surface either friable when newly cast,
or when dry the surface is full of small water lines,
like a map, or a broken spider's web. This is owing
to the suction caused by the porous nature of the mould
and the water escaping through the weak or open parts
leaving corresponding lines on the concrete surface.
These defects are obviated by using waterproof cen-
tring.

Where fineness of finish is not required, such as ware-
house floors, the surface can be made sufficiently fair
and smooth when filling in the concrete without sub-
sequent setting. The plaster is laid on the centring,
and made fair and smooth, and then the surface is
saturated with water to correct the suction; or the
surface, if dry, may be brushed over with a thin soap
solution to prevent adhesion. On this surface a coat
of neat cement about Ys inch is laid, and on this the
concrete is placed. The two unite in one body, and
when set, and the centring struck, the plaster sheet
comes with the boards, leaving a smooth surface. This
surface can be made in color by lime washing, which
will also give more light, or a finished white surface
can be obtained by substituting parian or other white
cement for the neat Portland cement. The concrete
must not be laid until the white cement is firm, not set,
otherwise the concrete will force its way in thin or
soft parts and disfigure the surface. I have success-
fully used this method for obtaining a finished sur-
face when encasing iron girders with concrete for fire-
proof purposes.

Staircase Materials, — ^With regard to the materials
for a concrete staircase, no one who intends to con-

400 CEMENTS AND CONCRETES

struct them substantially, fireproof and economically,
can afford to use common substances, when by judi-
cious selection and for a trifling additional first cost a
combination of materials can be obtained, which, if
not (strictly speaking) fireproof, is at least the most
incombustible constructive compound known. This is
a quality of the most vital importance in modem house
construction. Portland cement and slag cement are
the best known matrices. The finer Portland cement
is ground, the greater its heat-resisting powers. Slag
cement is lighter than Portland cement, and its fire-
resisting properties exceed those of both gypsum and
Portland cement. But as its manufacture is as yet
somewhat limited, and its strength not uniform, ex-
ceptional care must be exercised in testing its general
qualities before using it for staircases. Broken slag,
firebricks, clinkers and pottery ware are the best ag-
gregates,, being practically fireproof. All should be
clean, and in various graduating sizes, from that of a
pin's head to that of a walnut, for roughing out with.
The topping should be the same as that described for
Eureka paving.

Filling in Stairs, — ^Before gauging the materials,
sweep out all dust in the interior of the framing and
the wall chase and then wet the latter, and oil the
woodwork. If the wood of the nosing moulds and
risers is sappy or open grained, the long lengths, be-
fore being cut and fixed, should be made smooth and
indurated by coating with a solution of hot paraffin
wax. The smoother and less absorbent the surface of
the wood, the more readily and cleaner will the mould
leave the cast work. Parafl5n also renders the wood
damp-proof, thus preventing swelling or warping. For

HOW TO USE THEM 401

ordinarj'- purposes one or two coats of paraflSn oil will
be found sufficient. This should be done two or three
hours before the steps are filled in, so as to allow the
•oil to partly dry in and stop the pores of the wood*
If the wood absorbs all the oil, and has a dry sur-
face, brush the surface again with paraffin, using a
semi-dry brush. This should be done as the work pro-
ceeds. If the surface is over wet, the oil mixes with
the cement, thus causing a more or . less rough sur-
, face. Soap solution may Be safely used for rough
concrete, or where a rough surface is left to be sub-
sequently set. In the latter case the surface must be
well wetted with water and scrubbed before the final
coat is applied. Soap solution may also be used for
rough framing, such as soffit boards, but soap should
not be used for fine concrete or a finished surface,
as it leaves a film of grease which has a tendency to
prevent the cement adhering when clearing up or mak-
ing good the finished surface. As the work of filling
proceeds, the surface should be brushed over with a
slip, that is, neat cement, to fill up all angles, and
obtain a surface free from *' bulbs" and ragged ar-
rises.

The coarse concrete for roughing out the stairs is
composed of 1 part of Portland cement and 3 parts of
coarse fireproof aggregate. These materials must be
gauged stiff and laid in small portions of about a pail-
ful at a time, taking care to thoroughly consolidate
by ramming and beating with a wooden mallet„ using
a wooden punner or punch to get into the angles and
. deep parts. When the first layer, which may be about
3 inches thick, is rammed, another layer is deposited
and rammed, and so on until the rough stuff is within

402 CEMENTS AND CONCRETES

Yo inch of the line of tread. It must not be omitted to
l)rush the strings, treads and nosing moulds with slip
as the work proceeds. This is most effectually done
by the aid of a tool-brush. Care must be exercised
when ramming stairs with mallets or punches that the
mallet or other implement used is not too large or too
heavy, for it would most likely cause the framing to
bulge out, and the form of the work would be irre-
trievably spoilt. During the operation of ramming
some of the water and a part of the constituent of the
cement is forced upwards, and leaves a thin, smooth,
clayey film on the surface, which prevents the adhesion
of the next layer. For this reason the successive lay-
ers should be deposited before the previous one is set,
and the topping should be laid while the coarse con-
crete is yet green. Too much stress cannot be laid upon
the importance of topping the rough coat while it is
green. This is one of the secrets of success of solid
and strong work, so no more rough stuff should be laid
than can be topped before the rough is set.

The fine stuff for the topping is the same as for
Eureka paving, viz., 1 part of cement to 2 parts of fine
aggregate, gauged firm and plastic. The tread is made
level and fair by means of a running mould so formed
that it bears on the nosing moulds above and below the
tread. The mould has a metal plate or *'shoe" fixed
so as to run and form the tread. The shoe projects
so that it will work under the riser board close up to
the concrete riser. Illustration No. 23 shows a sec-
tion of steps with the mould in position; also a sec-
tion of the nosing mould and soffit boards and car-
riage. The end of the slipper next to the wall is cut
i|hort to allow the mould to run close up to the wall. A

HOW TO USE THEM 403

section of a T iron is ahown as sometimes used as an in-
temal support. Iron is ased for long steps, or wher«
stairs are intended for heavy trafBc. Iron helps to sup*

—Suctions op Fbami"" O" Soppit op Stair, Rism
fuD Noser Moold, with Concretx akp Tbbad Rob-

MINO MOOLD IN EOStTIOH.

Ma St.

port the concrete until set; it is placed in alternate
steps, or in every third or fourth step, according to the
length of step. Ordinary sized steps require no iron,

404 CBMiJNTS AND CONCRETES

unless as a support for the concrete while green, and
during the process of making.

Finishing Stairs. — ^When the treads are firm after
being run, the upper part of the, nosing moulds are
removed, the surface and joists trowelled off. The ad-
vantages of having the nosing mould in two parts will
thus be seen, as it allows the joint at this most notice-
able part to be neatly cleaned off while the work is
green. The lower part of the mould will support the
concrete nosing during the finishing of the tread and
until the concrete is set. If the work is done with a
nosing mould in one piec^, which necessitates its being
left on until the concrete is set, the joint has then to be
filed down and stopped, and however well done, has a
patchy appearance. When the treads are finished, and
the work set, but not dry, the riser and string boards
are taken off, the joints made good, and the returned
end of the steps cleaned off. If the stuff has been
properly gauged and rammed, there should be little
or no making good required, but it is important that
if necessary it should be done while the work is green.
A thin layer of neat cement will not adhere on a dense
and dry body of concrete. The only way to obtain
perfect cohesion is to cut the damaged surface out to
a depth of not less than ^ inch, then thoroughly wet
it, brush the surface with liquid cement, and fill it in
with gauged cement. No traffic should be allowed on
the treads during the process of setting and harden-
ing. The work is further protected and hardened by
covering with sacks kept wet for several days by fre-
quent watering. Where there are several flights of
stairs to construct, there should not be less than three
B^ts of strings and riser boards, which will enable the

HOW TO USE THEM 405

carpienter to fix one setjvhile the plasterers are filling
in and cleaning off the others,

Non-Slippery Steps, — Incessant traffic tends to make
the treads of steps more or less slippery. In order to
obviate this, the surface is indented with a concrete
roller, similar to that used for some kinds of paving.
Another way is to form three or four V-shaped grooves
from 1 inch to 2 inches apart on the treads while the
ieoncrete is moist. Another way is to insert leaden
cubes about 1 inch square from 2 to 3 inches apart
in the surface of the treads. Well-seasoned, hard
wooden blocks, about the same size as the lead and
fixed in a similar way, keeping the end grain vertical,
are also usee! for this purpose. India rubber and cork
cubes may also be used.

Striking Centrings. — This should not be attempted
until all the other work, with the exception of finishing
the soffits, is done. It will be understood that the
framing can be arranged so that the string and riser
boards can be taken off without disturbing the soffit
centring, which is kept up as long as possible. The
lime for striking centring greatly depends upon the
class of cement used, the manner of gauging and lay-
ing the concrete, and the temperature; but generally
speaking, centring should not be struck for at least
ten days. A stair between the walls can be struck
much sooner than one having only one bearing by which
its own weight is carried. I have seen a stair, with
steps projecting 3 feet 6 inches from the wall, cleared
of all supports in five days from the time of filling
in; but this was with good cement, gauged 1 part to 2
of aggregate, and in warm weath^, and the stair was
strengthened with T iron.

406 CEMENTS AND CONCRETES

The centring and framing for a flight of stairs should,
where practicable, be independent of other stairs above
or below, so that they can be struck in due rotation.
The wedges of the main props should be gradually
withdrawn. This tends to avoid the sudden jar which
otherwise often happens when the centring is too sud-
denly struck. The sudden removal of centring and
the inflexible nature of concrete are the cause of body
cracks. The damage caused by the sudden jar may
not be seen at the time, but it will be eventually devel-
oped by the force of expansion, which always finds out
the weak spots.

Concrete cmd Iron. — Iron pipes, bars and T pieces
are sometimes used with concrete stairs where the steps
are long, or where landings have little support from
walls. They help to carry the dead weight until the
mass is thoroughly set, and also prevent sudden de-
flection if the centring is struck too soon. When iron
pipes are used for steps they should go right into the
wall chase. , Iron T pieces are used for long landings.
Care must he taken^ that, if the iron is used, no part
should be left exposed. It must be embedded in the
concrete to protect it from oxidization and the effects
of fire. When iron girders, etc., are partly exposed,
they should be. painted. Iron bars or pipes are occa-
sionally used to strengthen the outer strings of spandrel
stairs. The iron is laid in the moist concrete
near and along the string, having the ends projecting
into the walls or landings. Angle irons are often used
for unsupported concrete angles. Iron pipes, bars or
joists are used as integral supports for landings and
floors having unsupported ends.

The tensile strength of bar iron is materially in-

HOW TO USE THEM 407

,j ,

creased by twisting. A bar % inch square with three
twists per foot will gain about 50 per cent, in tensile
strength when embedded in concrete, and give a corre-
sponding strength to the concrete. A combination of
iron and concrete is of special service where space is
limited. For instance, if a beam or landing requires
a certain thickness to carry a given weight, and it is
inconvenient or difficult to obtain that thickness, the
requisite degree of strength with a reduced thicknesis
may be obtained by the combination of both materials.
This gives the combined iron and concrete a useful ad-
vantage over stone. It is important to secure the full
strength of the iron, and that none be lost or neutral-
ized. In order to obtain the full strength the iron
should be judiciously placed. Thus, a piece of iron
surrounded by twenty times its sectional area of con-
crete would increase the weight-sustaining power of the
iron in the centre and would have its strength in-
creased about twice. If the same quantity of iron was
placed in several pieces, so as to throw as much tensile
strain on the iron as possible, the strength would be
increased nearly four times. In order that none of the
strength be lost or neutralized, the iron should be
placed near the lower surface ; if fixed higher, they are
nearer the axis of neutral stress, and are correspond-
ingly less effective. The use of iron in concrete is in-
valuable for many constructive purposes, but for gen-
eral work, unless as a temporary aid and in a few ex-
ceptional cases, it is unnecessary. For all other things
being equal, the huge board of reserve strength in good
concrete is alone sufficient to sustain as great if not
a greater weight than that sustained by natural stone.
No other artificial compound exceeds the strength of the

408 CEMENTS AND CONCRETES

natural substance, as does artificial stone composed of
Portland cement concrete.

Setting Concrete Soffits, — The soffits of stairs and
landings, if neat cement has been used on a water-
proof centring, as already described, only require a lit-
tle stopping and coloring, but for work done on rough
centring a setting coat has to be laid. This is usually
done with neat Portland cement, though it is frequently
gauged with lime putty to make it work more freely.
The surface should be well roughened and wetted, to
give a key and obtain perfect cohesion. It requires
great care and time to make a good and true surface
with Portland cement on a body of concrete, espe-
cially if the concrete is dry, which is generally the
case where there are several flights of steps in a staiiv
case, and the setting of the soffits and landings are
left to the last part of the work. I have obtained
equally good results by using Parian or other white
cements for setting the soffits of staircases. When
using white cements for this purpose it is better to
brush the concrete surface with liquid cement before
laying the gauged cement. The laying trowel should
follow the brush, or at least before the liquid cement
dries in. This not only secures better cohesion, but
tends to prevent the setting coat peeling when trowel-,
ling it off. Soffits are sometimes set with gauged pirt-
ty. This is like putting a beggar on horseback, and
the work is never satisfactory.

Fibroid Concrete. — ^As already mentioned, canvas
and other fibrous materials may be advantageously
used with Portland cement for several purposes. Can-
vas forms a good ground for a setting coat on concrete
surfaces. It gives a uniform and strong key, prevents

HOW TO USE THEM 409

surface cracks, and the final coat from peeling. Coarse
canvas cut to convenient sizes is used. It is laid on
the centring, and held in position with tacks, or with
the same kind of cemebt as intended for the final coat.
The canvas is then brushed with liquid cement, and
then the concrete is laid while the canvas is moist, so
that the whole will form one compact body. When the
centring is struck, the fibrous concrete surface is rough-
ened with a sharp and fine drag, so as to raise the
fibre of the canvas, thus giving a fine, regular and
istrong key. This surface requires less material for the
final coat than the ordinary concrete surface. If tacks
are used they must be extracted before the final coat is
laid, to avoid discoloration. The rough concrete and
the white surface coat may also be done in one opera-
tion. The centring is made fair and smooth, and then
oiled with chalk oil. The white cement is gauged stiff
and laid on the centring. Coarse canvas is then laid
on and well brushed with liquid cement. When this
is firm (but not set) the surface is again brushed,
and then the concrete is laid. The concrete is deposited
in two or more layers. The first must not be too thick,
taking care that it is well rammed or pressed on the
moist canvas surface without disturbing the white ce-
ment. After the centring is struck any defects on
the surface are made good. The surface may be then
left white, or painted, or polished as required.

Polished Soffits, — Soffits, landings and strings of con-
crete stairs that are finished in white cement may be
polished. The material may be tinted, or left in its
natural white or creamy color. Polished cement work
is always bright, and has a lustre like marble. Be-
ing durable and easily cleaned, it is more sanitary and

/
410 CEMENTS AND CONCKETBS

cheaper than paint. The polishing is done the same
way as described for ** white work."

Cancrete Staircases and Fibrous Plaster. — ^Fibrous
plaster is well adapted for concrete surfaces when- an
enriched finish is desirable. I have introduced this
material for decorating the sofiits of steps and land-
ings ; also the strings of concrete stairs. By this method
the soflSts may also be enriched, and strings can be
panelled, or enriched with medallions or foliage, as re-
quired. The soffits may also be enriched with modelled
work done in situ, with some of the white cements, or
with plaster and tow. The strings may be decorated
with hand-wrought gesso. In order to obtain a fixing
or keying substance that will receive nails or screws
to sustain the fibrous plaster, a rough plan of the de-
sign, or rather the fixing points, is set out on the in-
side of the centring before the concrete is laid. On
these plans wood plugs, fillets or concrete fixing blocks
are laid, and held in position with nails, plaster or ce-
ment until the concrete is laid and set. Care must bo
exercised when fixing the plugs or fillets that the
centring will leave freely without disturbing the plugs,
etc.

Dowel Holes. — Cutting dowel holes in concrete to
receive iron or wood balusters is a slow and tedious
process. They are best formed by means of wooden
plugs, which are fixed before treads; the plugs are
driven into the rough concrete before it is set, leaving
them flush with the line of tread, so that when the
topping is laid they will not be in the way. Plugs
are best fixed by the aid of a wooden gauge. The
gauge is made the same thickness as the topping, the
length being equal to the distance between the nosing

HOW TO USB THEM 4U

mould and the riser boards and as wide as will admit
of plug holes and the plugs to be driven thrpugh. The
plugs are made a little larger than the baluster ends
to allow for the lead. The gauge is laid on the rough
concrete, using the returned nosing as a guide, and then
driving the plugs flush with the top of the gauge.
The gauge is then lifted up and laid on the next step,
and so on until the finish. This method is accurate
and saves measuring and marking the position of each
hole on every step. When balusters are fixed on the
ends of the steps, the plugs are fixed on the inside of
the outer string; The plugs are generally left in until
the balusters are ready for fixing. A ready method
for forming *' lewis" holes or other undercut sink-
ings in concrete is performed by casting wedge-shaped
blocks of plaster of the required form and size, and
then laying them in the desired positions while the
concrete is soft. When the concrete is set, the plaster
blocks can then be easily cut out, leading the under-
cut sinking as desired.

Summary of Staircases Constructed ^'in Situ.^^ — ^It
will be seen from the foregoing that the operations em-
ployed in the construction of concrete staircases formed
in situ are: (1) setting out the stairs and landing; (2)
fixing the wood framing; (3) gauging the materials and
filling in; (4) removing the framing; (5) cleaning up
the treads, risers and strings; (6) striking the soffit
centring and finishing the soffits; (7) protecting and
wetting the work until set and hard.

Cast Steps, — Staircases are also constructed with
steps cast separately, and then built in, in the same way
as stone. Illustration No. 24 shows various sections
of steps. Fig. 1 is a spandrel step, which may be used

412

CEMENTS AND CONCRETES

for model dwellings, factories, etc. The tread is grooved
to aflford a good footing and prevent dipping. The
dotted line indicates a square seating or tail-end of the
step, which is embedded in the wall. Fig. 2 is a square
step. Fig. 3 is a step with a moulded and returned

Fig. L

Fig. 2.

Fig. 3.

Fig. 4.

SscTioNs OF Steps.

NO. 24.

nosing. Fig. 4 is a similar step, but having a moulded
sofRt. For cast work these steps must have a square
seating or tail-end, as indicated by the dotted lines on
Fig. 1, so as to bond into the wall.

T&EADs AND Risers.

NO. 25.

Treads and Risers. — ^Stairs between walls are sonae-
times formed with treads and risers. The treads and
risers are cast and built in as the construction of the
work proceeds. Sometimes they are let into chases and
pinned after the walls are built. Illustration No. 25
shows a section of treads and risers.

HOW TO USB THEM

413

Closed Outer Sirin^a.— Staircases are sometimes fin-
ished with a close outer string, which prevents dirt or
wet falling into the well. Illastration No. 26 shows
the section, Fig. 1, sud the elevation, Fig. 2, of a
moulding outer string. The dotted line at A indicates
a dowel hole for the balusters. Outer strings, whether
plain or moulded, are much stronger when formed in

situ. This is best effected by fixing a reverse mould
at each side, then filling in the space from the top. The
top is finished by hand and the aid of a template. The
dowel holes are formed as already described.

Concrete Floors. — It has been mentioned that the
Romans, in the time of Julius Caesar, were in the habit
of eonstrueting their floors and roofs, as well as their
walls, of concrete. According to an article in Archaeolo-
gia, the cementitions agent was pozzolana. The lime

414 CEMENTS AND CONCRETES

was obt ained by burning ' ' traverstine. ' ' The aggregate
usually consisted of broken tufa for walls, of broken
lava for foundations where great strength was re-
quired, and of broken pumice where lightness was es-
sential. The floors were generally constructed of large
slabs of concrete, supported on sleeper brick walls.
The upper surface was finished with a layer of finer
concrete and mosaic. The roofs were made flat, rest-
ing on brick pillars. The first known English patent
fireproof construction was obtained by one Dekins Bull,
in 1633 ; but as at that period patentees were not com-
pelled to disclose what their patents covered, no de-
scription of the materials and methods can be given.
Up to the middle of the eighteenth century fireproof
their great weight and cost, were seldom used. But
towards the close of that century cast-iron girders and
segmental brick arches were gradually coming into use
where strength was essential. Up to a century ago
plaster was largely employed as a floor material. In
floors usually consisted of brick arches, but owing to
1778 Earl Stanhope invented pugging for rendering
wooden floors fireproof. By this process fillets were
paled to the joists at about one-third of the height.
Laths were laid on the fillets and plastered above and
below with a coat of lime and chopped hay. The under
sides of the joists were then lathed and plastered in the
usual way to form the ceiling. About the early part of
the last century wrought iron joists were substituted
for cast iron girders. Fox & Barret's floor, designed
about 1830, was the first in which an attempt was made
to protect the exposed faces of the iron joists with a
fire-resisting material. Hornblower's floor is one of the
earliest for resisting the effects of fire. Iron, bricks

now TO USB THEM 415

and plaster are chiefly used in the French and Ameri-
can systems. For the sake of simplicity and reference,
concrete floors may be divided into three kinds: (1)
*' Joist floors," in which the concrete is laid slid be-
tween the joists; (2) ** Tabular floors," formed with
fireclay tubes or hollow lintels placed between the
joists and covered with concrete; (3) ''Slab floors,"
formed in one piece or slab. Portland cement concrete
laid in situ on and between iron joists is extensively
used for fire-resisting structures. Cast concrete is used
for some parts of tabular floors. Cast concrete blocks
are used for the ceiling surface, and as a support for
the rough concrete floor surface. The blocks are hol-
low, and have male and female dovetails on the sides.
The ceiling surface of the floors and the outer surfaces
of the partitions are finished with a thin setting coat of
gauged putty or Parian. The chief objects of fire-
proof floors are to render each floor capable of resist-
ing the effects of fire, so that firfe cannot be communi-
cated from one floor to another, and by making the
roof flreproof, to prevent the fire from spreading from
one compartment to another; to gain additional
strength, so as to avoid as far as possible lateral thrust
on the walls, and to secure the building from attacks
and effects of both dry rot and damp. There have been
about a hundred patents for fireproof floors during the
past generation, of which about five or six survive.

Plaster Floors, — Plaster concrete, that is, plaster and
broken bricks, or similar aggregates^ also neat plaster,
Tvere at one time used largely for the formation of
floors. The use of plaster floors was common in some
districts, and up to a century ago the rough plaster,
known as ''floor plaster," was in general use where

416 CEMENTS AND CONCRETES

gypsum was found in abundance. Plaster floors were
rarely used on the ground level, because they could not
resist moisture, which caused them to become soft and
retain the damp. They were principally used for up-
per floors. The gauged plaster was laid upon reeds.
These reeds were spread upon the tops of joists, and
over them was laid straw to keep the soft plaster from
percolating through the reeds. The flftors were about
3 inches thick, floated fair, and finished the following
day. "Wood strips were placed aroimd the walls, and
drawn out when the plaster began to set, to allow for
ihe expansion of the plaster. The materials being so
light, the timbers were less in size and number than
those now in use. The joists were in some instances
3^2 inches by 2^ inches, fixed wide apart, and suj^
ported by small beams about 4^ inches by 3^ inchea
The undersides between the joists were made fair by
plastering the reeds, but in the better class of work the
joists were covered with reeds, and held in position with
oak laths, and plastered. Bullock's blood was used to
harden the floors after they were dry. In some in-
stances they were coated with linseed oil to increase
their hardness. SJieir use is now practically super-
seded by Portland' eement concrete.

Joist Concrete Floors. — For this form of floor the
concrete is laid between, over and under the iron joista
Beyond the supervision of the flxing of the centring
and the gauging of the materials, little billed labor ia
required. The rough concrete is laid between and
partly under the iron joists, which are fixed from 3 feet
to 5 feet apart, according to the span and strength of
the joists. The centring is supported, or rather himg^
by the aid of timber laid across the joists and secured

HOW TO USE THEM 417>

by bolts. The materials are generally Portland ce-
ment and gravel, coke-breeze, clinkers and broken
bricks, gauged in the proportion of 1 part of matrix
to 5 of aggregate. Sand equal to one-third of the
bulk should be added. Coke-breeze is weak, light and
elastic, but combustible and porous. A mixture of
gravel and breeze in equal proportions is better than
either alone. The proportion of cement varies accord-
ing to the span and class of aggregate. AH other
things being equal, the strength of concrete is influ-
enced by the strength of the aggregate, so that it
would take a greater proportion of cement to make
coke-breeze concrete equal in strength to a concrete
made with hard aggregate, such as granite, slag or
brick. The upper surface of this class of floor may
be finished with wood, tiles or fine concrete, as re-
quired. Joist concrete floors have been largely used.
This is principally owing to their siipposed cheap-
ness, but it is more than probable that,' in the event
of fire, they would be dear in the end, because the
lower part of the flanges are barely protected from the
effects of flre, as the concrete, being thin at these parts,
and also on a comparatively smooth surface, would
soon crack or scale off, and leave the flahges of the
joists exposed to the ravages of fire. They are also
more or less conductors of sound. Caminus concrete
cement is an excellent material for the construction
of fireproof ceilings and partitions.

Caminus Concrete Cement. — This material is specially
designed to produce a hard and practically indestructi-
ble concrete for the construction of fireproof fioors and
walls. It is manufactured from a waste product, and
all inflammable material, such as coke-breeze, being en-

418 CEMENTS AND CONCRETES

tirely dispensed with, the concrete is thoroughly fire-
resisting. It is lighter and much cheaper than Port-
land cement concrete, and is perfectly free from ex-
pansion and contraction whilst setting. It can be man-
ufactured to set in a few hours, so that the centres
can be struck the day after the floor is laid. It can
be supplied in a ready aggregated condition, so that the
bags may be hoisted direct to the floor where the con-
crete is being laid, and gauged on the floor, tHus sav-
ing a great amount of waste, and also labor in handling,
mixing and laying.

Concrete Floors and Coffered Ceilings. — ^A method
was patented by E. Ransom for decreasing quantity of
material and yet obtaining equal strength in floors. The
floor is divided by a series of beams at right angles
to each other, so as to form a series of coffers in the
ceiling. For instance, for a floor 12 inches thick, the
floor proper would be about 4 inches thick, and beams
about 3 inches thick and 8 inches deep — a rod of twist-
ed iron being placed in the centre of the thickness, and
near the lower surface of the beams. The beams are
generally about 2 feet p inches from centre to centre.
The method of construction is as follows: First, form
a platform or centring; on this a series of core boxes
2 feet 3 inches is placed, 3 inches apart, so as to form
^ 3-inch beam. The core boxes must be tapered and
their upper edges rounded, so that they will draw when
the centring is struck. The size of the core boxes may
be altered to suit the size and requirements of the
floor. With regjard to the iron bars, the inventor says :
^*It is of vital importance for the strength of the struc-
ture that the iron bars be placed no higher in the beam
than calculated for; that the longitudinal, centre of

HOW TO USE THEM 419

these bars should be at the lowest point; and it is ad-
visable that tlie bars curve upwards slightly and uni-
formly each way from the centre to the ends, so that
the ends are from 1 to 3 inches higher th^n the cen-
tres. By preparing the concrete bed on a correspond-
ing curve, the natural sag of the bar, as it is being
handled to its place, gives all the requisite facility to
accomplish this purpose. No crooked or irregular
twisted iron must be used; otherwise, when the strain
comes upon it, it will perforce straighten and lengthen
out, and weaken the structure in so doing. After
placing the iron, the rest of the concrete is tamped in
place, and the whole made to form a monolithic block.
It is of vital importance that no stop be made in the
placing of concrete from the time the beam is begun
until the thickness of the beam is in place and a
'through joint' is made. The web and the thickness
must be one solid piece of homogeneous concrete."

Combined Concrete Floors and Panelled Ceilings, — ^A
combined floor and panelled ceiling may also be formed
in concrete. This is executed as follows: First, form
a level platform or centring, and on this fix the re^
verse plaster mould, run and mitred, according to the
design of the ceiling. The intervening panels are then
made up with framing, and the concrete filled in the
usual way, and when set the centring and reverse
mould are removed, and the ceiling cleared off. If de-
sired, a finely finished and smooth white surface may
be obtained by coating the surface of the moulds and
panels with firmly gauged Parian, or other white ce-^
ment, until about % inch thick, and when this is firm
(but not set), the rough concrete is deposited in layers
and tamped to consolidate the concrete, and unite it

420 CEMENTS AND CONCRETES

with the white cement. The surface may also be fin-
ished with fibrous concrete. The method of doing this,
also for carrying out the above white cement process, is
described in ** Fibrous Concrete."

Concrete and Wood. — Concrete floors finished with
flooring boards require special care to prevent damp or
dry rot. There are various methods in use for fixing
and keeping the flooring boards from contact with the
rough concrete, one way being to fix wood fillets to the
joists by means of wedges or clamps. Another way
is to embed wood fillets or fixing blocks in the rough
concrete, leaving them projecting above the level of the
iron joists, to give a bearing and fixing points to the
flooring boards ; or. fine coke-breeze, concrete or plas-
ter screeds, may be laid at intervals on the rou^
concrete, onto which the boards are nailed. Fixing
blocks, concrete or plaster screeds, are preferable to
wood fillets, as they do not shrink or rot, and will
better resist fire. All these methods leave intervening
spaces between the concrete and the boards, and unless
thoroughly ventilated, they harbor vermin, dirt and
stagnant air. Unless the wood is thoroughly seasoned,
and the boards grooved and tongued, dust and ef-
fluvia will find egress through the joiilts. A portion of
dust and water when sweeping and washing the floors
also finds egress through the joists ; and as the concrete
will not absorb the water, or allow the dust to escape,
they accumulate and become unseen dangers. Thase
sanitary evils may be obviated, or at least reduced to
a minimum, by laying the boards direct on the con-
crete. This not only forms a solid floor with no inter-
spaces, but admits of thin boards being used with as
ipuch if not greater advantage, than a thick board.

HOW TO USE THEM 421

There is no uneven springing between the joists, which
causes friction and opening of the joints, and the whole
thickness is available for wear. There is also less total
depth of floor, consequently less height of building and
general cost. Another important advantage of a solid
floor is that it will resist fire better than one with hol-
low spaces. It is tere that the sponginess and elasticity
of coke-breeze concrete as a top layer is of special
service, and where it may be utilized with advantage^
Owing to its being able to receive and retain nails, the
boards can be nailed at any desired place. Wood
blocks for parquet floors can also be bedded or screwed
on the concrete surface. Flooring boards will lie even
and solid on this surface, and if a thin layer of felt or
slag-wool be spread on the concrete before the boards
are laid, a firm and noiseless floor is obtained. Slag-*
wool is an imperishable non-conductor of heat, cold
and sound, and it will not harbor vermin. If the work
is in humid climate, the coke-breeze surface when dry
should be coated with a solution of tar and pitch, to
prevent atmospheric moisture being absorbed by the
porous coke-breeze.

Concrete Drying. — To prevent dry rot It is of the ut-
most importance that the concrete should be thoroughly
free from moisture before the flooring boards are laid
and fixed. The drying of concrete is a question of
time, which depends upon the amount of water used
for gauging, the thickness and the temperature. It
may take from three days to three weeks or even three
months. The drying can be accelerated by directing
currents of hot air on the lower surface, or by laying
some absorbent material, such as dry sawdust or brick
dust, on the upper surface. As soon as the surface

422 CEMENTS AND CONCRETES

moisture is absorbed, or the dry material has no further
absorbent power, it should be removed to allow the
mass to be air dried. Another way is to lay the floor
in two coats, and to allow one coat to dry before the
other is laid. For instance, if the floor is to be 6
inches thick, the first coat is laid with rough, but
strong concrete, the aggregate being the best available ;
but taking gravel and coke-breeze to be the most
plentiful, it will be best to assimilate and combine the
good qualities of each to equalize their defects by mix-
ing them in equal proportions. If brick is plentiful,
and broken to properly graduated sizes, it will give
better results than gravel or breeze. The mixed ag-
gregate is gauged 5 parts to 1 of cement, and laid 4%
inches thick, and gently but firmly beaten in situ, the
surface being left rough to give a key for the second
coat. The second coat is not laid until the first is
dry, and consists of one part cement to 5 of sifted and
damped coke-breeze, gauged stiff, and laid 1^ inches
thick, beaten in situ, ruled level, and any ridges being
laid fair with a Idng hand-float. The moisture of the
second coat, by reason of the density of the first coat,
will only be absorbed to a small degree, while the
greater portion will be taken up by the atmosphere,
and enable the combined coats to dry sooner tlian if
laid in one. The first coat should be laid as soon
as the roof is on, so as to give all possible time for it
to dry, and the second coat to be laid and dried before
the flooring is laid. When coke-breeze is not avail-
able for the second coat, use soft brick, broken to pass
through a 3-16-inch sieve. The method of laying floors
in two coats is only given as an alternative plan, and
as an example of a process used in some parts. Greater

HOW TO USE THEM 423

strength, as a whole, and more perfect cohesion be-
tween the two coats, is obtained by laying the second
coat as soon as the first is laid, or at least while it is
green.

Concrete Slab Floors. — The term, slab floor, is applied^
to a concrete floor formed in situ, and in one piece or
slab. It must not be confounded with slab pavements,
which are constructed with a number of small cast
slabs. Slab floors are usually made without exterior
iron supports, but in a few instances iron T pieces or
bars have been used as internal supports. Bearing in
mind the lasting properties of the old Roman slab
floors, and the enormous strength of the modern exam-
ples at home, which are unsupported by iron, and are
practically indestructible, it seems strange that they are
not in more general use, and that for some inexplica-
ble reason preference is given to shrinking, rotting
and combustible floors, compose^ of poor iron and tim-
ber instead of the best work and material, which, if a lit-
tle dearer at first, is infinitely superior and vastly
cheaper in the long run. The great sanitary advan-
tages and fire and damp resisting powers of concrete
slab floors are the highest known. The construction of
slab floors is simple, and similar in many respects to,
that already described for stair landings and ordinary
concrete and joist floors. There are several methods
of supporting the floors, the first and most common
being to leave a sand course or to cut a horizont|il chase
in the walls to receive the ends of the floors. The
second is to lay the floors when the walls are floor
high, and build the. higher walls on it when set. This
method, while making sound work, is not always prac-
ticable or convenient, owing to the delay in building

424 CEMENTS AND CONCRETES

.while waiting for the floors to set. The third method
is to build corbelled ledges in the walls, so as to carry
the floors. The centring for slab floors should be per-
fectly rigid, water-tight and slightly cambered towards
the ceiling centre. This camber gives more strength
to the floor, and lessens liability to crack when remov-
ing the centring. If joists are not used, the centring
is supported on wall boards and centre struts. An-
other way which gives great additional strength is to
form the centring level, but having all the edges at the
wall rounded off, so as to form the floor like an in-
verted sink or tray. The horizontal chases in this case
should be made wider than the thickness of the floor to
allow for a thickness of rim. The extra width of chase,
which may be one or two bricks thick, according to the
width of span, is made below the centring or line of
ceiling, the angles being coved by rounding the edges
of centring. The coved rim gives greater strength
with a less thickness of floor. The cove may be left
plain or used for a cove for a plaster cornice, or rough-
ened and used as a bracket for the same purpose. The
expansion of concrete floors having large areas, or
where hot cement has been used, has been known to
disturb the walls, causing cracks and displacement of
brick and stone work. This" may be prevented by
isolating the floor ends, from the- walls. This is done
by forming expansion partitions or linings in the chases,
the linings being composed of slag, felt or wood shav-
ings, straw, reeds or other compressible material. The
chase should be sufficiently deep to allow for a com-
pressible lining about IV2 inches thick, and a fair bed
for the slab floor. Care must be taken to leave a few
half bricks solid at intervals,, say from 3 to 4 feet

HOW TO USE THUM 425

apart, to support the upper walls until the floor is set.
Compressible linings may :hj^4lsed for floors supported
on corbelled ledges; and when the expansion, and in
many eases subsequent contraction, has finally finished,
the linings can be taken out, and the vacant space
filled up with fine concrete, or utilized as a ground key
for cement skirtings. If girder or iron posts are iso-
lated from the walls by means of compressible linings,
the effects of expansion and sound are limited. In
some instances a judicious use of iron may be made.
For instance, large areas may be divided with three or
four rolled iron joists, so as to form shorter spans or
smaller bays. Joists tend to bind the walls together,
and to serve as scaffold bearings for building the upper
parts of walls. They may also be used for hanging
the centring on instead of strutting, or as aids to vhe
strutting. Joists may also be used as integral sup-
ports at unsupported ends of concrete floors. They
should be so fixed that the lower flanges are not less
than 1 inch above the lower surface of the concrete.
The whole strength of iron is brought more fully into
use by fixing it near the lower surface. If fixed near
the centre, or at the axis of neutral stress, a correspond-
ing part of the strength lis comparatively of little
value.

Construction of Slab Floors. — ^Portland cement as a
matrix is indispensable. The unequal nature of gravel
and coke-breeze renders them unfit and unsafe aggre-
gates for this class of work. Broken brick being cheap^
and obtainable in most districts, affords a ready aggre-
gate, and may be used with safety and success. In
ordinary cases of concretje construction, the whole
thickness is usually made with one rate of gauge; but

426 CEMENTS AND CONCEETES

for slab floors covering large areas, and unsupported
by iron or other supports, exceptional strength is re-
quired. Stronger results are obtained by making up
the whole thickness with different rates of gauge. Tak-
ing the usual gauge for floors as from 4 to 5 parts of
aggregate to one of cement, and used for the whole
thickness, it gives an unequal strength, a part of which
is comparatively of little use, especially at the neutral
axis; but if the cement is divided so as to form an
ordinary coat in the centre, and stronger coats at the
upper and lower surfaces at the points of greatest
strain, the upper being compressive and the lower ten-
sive, a better and more accurate arrangement of
strength and allowance for disposition of strains is ob-
tained. The additional strength at the proper places
is obtained not only by the use of additional cement,
but by the method of construction, which enables the
same quantity of cement as gauged for the usual rate
for forming the whole thickness in one coat to
be used more profitably. Take the section of
an iron joist as an example; this gives divided
yet united strength, which sounds paradoxical,
but is true. The flanges sustain the greatest
strains, and the web comparatively little. With con-
crete, the strong coats at the upper and lower surfaces
represent the flanges, and the ordinary coat the web.
As already stated, the increased and profitable dis-
tribution of strength is obtained by the method of con-
struction. For instance, take a slab floor 20 feet by
14 feet and 12 inches thick, without iron joists or other
supports, and intended to carry a safe load of 2^4 cwt.
per superficial foot, in addition to its own weight of say
J. cwt. per square foot. This floor is laid in three coats.

HOW TO USE THEM 427

the first composed of 1 part cement and 2 of fine broken
bricks gauged stiflf, and laid 2 inches thick; the second
composed of 1 part cement and 6 of coarse broken
bricks gauged stiff and laid and rammed 8 inches thick ;
and the third composed of 1 part cement and 2 of fine
broken bricks gauged stiflf and laid 2 inches thick.
If the upper surface is intended for hard f rictional wear
a slight diflference is made in the gauge and materials.
The first coat is composed of 2 parts of cement and 5 of
fine broken bricks gauged stiflf and laid 2 inches thick ;
the second of 1 part cement and 6 of coarse broken
bricks gauged stiflf and laid and rammed till 8 inches
thick ; and the third coat composed of 1 part cement and
2 of fine crushed slag or granite. It will be seen that
this constructive method gives the desired positions of
strength, and the total quantity of cement in the united
gauges is 1 part to 4, ^^^ ^P to 5 parts of aggregate.
The fine broken bricks should be passed through a %-
inch sieve, and the coarse through a 2-inch screen,
taking care that the latter contains a greater quantity
of the smaller pieces than of the larger. It must be
clearly understood that the second coat must be laid
before the first is set ; also that the third is laid before
the second is set, so as to ensure perfect cohesion be-
tween each coat, and the absolute homogeneity of the
whole mass.

Hollow Floors. — Greater lightness in concrete floors is
obtained by the use of concrete tubes. If the tubes are
placed apart and in the centre of the floor thickness,
a hollow homogeneous concrete slab is formed. The
vertical divisions between the tubes connect the upper
and lower coats, as with a web of a joist connecting the
upper and lower flanges. The method of construction

428 CEMENTS AND CONCRETES

is simple and expeditious. For example, for a slab
floor 10 inches thick^ first lay a coat 2 inches thick of
the stronger and finer concrete, as described for the
12-inch slab floor, and when this is firm lay 5 or 6-
inch tubes from wall to wall. Bed the sides with rough
concrete, and lay another row of tubes parallel with the
first row and about 2 inches apart, and so on until the
floor area is covered; then make up interspaces with
rough concrete till level with the upper surfaces of the
tubes, and then cover this with a coat of fine concrete 2
inches thick. Concrete tubes or common earthenware
drain pipes may be used. Half-circle pipes, laid on
their side edges, may be used to save concrete and
weight in joist floors, etc.

Concrete Roofs. — Concrete roofs require special care
to render them watertight. Subsidence in the brick
work of new buildings is often the cause of cracks on
concrete roofs. The roof should have a good camber,
to give greater strength and allow for the fall of wa-
ter to the outer edges. The rough coat should be laid
and well consolidated by ^ramming or beating, and then
left for seven days (the longer the better) before the
topping is added. The upper coat should be strongly
gauged with fine aggregate, as in '* Eureka." If possir
ble, the topping should be laid in one piece. If the
area is too large to be laid and finished in one piece,
the joints of the bays should overlap. This is done
by rebating the screed rules, so as to allow one-half of
topping thickness to go under a part of the rule and
form an underlap or ledge about ^ inch wide, and
when the adjoining bay is laid an overlapped but level
joint is the result. Roofs exposed to the sun's heat
should be kept damp for several days after being laid.

HOW t6 use them 429

as joints are affected by the heat as well as by deflec-
tion of centring or subsidence of walls. Compressible
linings or wood strips should be used round the walls
to counteract any expansiori. AH concrete roofs should
have a cement skirting 6 inches high and 1 inch thick
well keyed into the walls. If linings are not used when
the topping is laid, the topping should be turned up on
the walls, so as to form a., rim, to prevent water get*
ting between the roof tod the walls. Greater heat and
damp-resisting powers are obtained by laying the up-
per surface with l^-inch thick coat of special concrete,
composed of 1 part of Portland cement, % part of
slaked lime and 1 part of firebrick dust. This should
he consolidated with a hand-float, and finished fine and
close with a trowel.

Notes on Concrete. — ^When calculating the strength of
floors, stairs, etc., the following facts should be borne,
in mind : Portland cement, when new, is too hot ; sets
more rapidly and expands more than old cement. The
finest ground cement is the best and strongest. The
time in setting, and in which the maximum strength js
attained, varies according to the age of the cement, the
quantity of water used, and the mode of gauging and
the mean atmospheric temperature. The maximum
strength of a briquette of mature cement is maintained,
while one of new cement ''goes back." A briquette of
matured cement will stand a 'tension strain of 550
pounds per square inch, and a crushing weight of 6,000
pounds per square inch. A briquette of neat cement is
more brittle than one of concrete. Briquettes mature
more rapidly than thick slab floors. The adhesive
strength of Portland cement is about 85 pounds per
square inch. The adhesive strength increases more

430 CEMENTS AND CONCRETES

rapidly than the cohesive. A mass with a surface
large in proportion to its volume sets more rapidly than
a mass with a small area in proportion to its volume.
Masses subject to pressure set more rapidly and attain
greater hardness than masses not so pressed. The
average compressive stri^ngth of concrete is about eight
times its tension strength. The proportion of com-
pressional and tensional strength varies according to
the quality and quantity of the aggregate. The strength
of concrete depends greatly on the proportion of the
matrix and aggregate ; also on the strength of the lat-
ter. As regards bricks, it must be rem.embered that
there is a wide difference between the tensile strength
of hard, well-burnt bricks and soft stocks. No bricks
are so strong as cement, the best kinds being about
one-fourth the strength of neat cement. Taking the
gauge as one part of cement to 4 of broken brick, the
strength of the concrete will be about two-fifths of neat
cement, but for safe and practical calculations it V7ili
be best to take the strength as one-fourth of neat ce-
ment. Square slabs are stronger than rectangular
slabs. Slab floors being homogeneous throughout, the
whole weight is a dead weight, and consequently there
is no thrust on the walls. With regard to the live load
or weight which floors should be constructed to carry,
some difference of opinion exists. Hurst says that for
dwellings l^^ cwt., public buildings ^ cwt. and ware-
houses and factories 2^/2 cwt. are safe calculations.
Others assert that for domestic buildings 1 cwt. per foot
would be ample for all contingencies. An American
authority states 40 lbs. is suflScient for ordinary pur-
poses. The following table shows the results of tests

HOW TO USE THEM

431

of slab floors made without iron. The slabs were sup-
ported all round, and uniformly loaded with bricks.

Test of Slab Floors.

No.

Length
between
Sup-
ports,
feet.

Breadth
between
Sup-
ports,
feet.

Thick-
ness,
feet.

Age in
Days.

Breaking

Weight, in

cwt. per

sq. ft.

Weight of

Slab, in

cwt. per

sq. ft.

Total
Breaking
Weight, in
cwt. per

sq. ft.

14.5

6.75

.54

3.54

((

2.76

3.30

8.88

9.42

13.5

. 7

1.07

1.61

6.75

2.51

8.05

2.8^

8.38

Cast Concrete. — ^Innumerable patents have been ob-
tained for a combination of materials, also moulds for
the construction of artificial stone. Among the many
that may be mentioned is Mr. Ranger's system. He
obtained a patent in 1832 for artificial stone formed
with a lime concrete. The aggregate consisted of
shingle, broken flints, mason's chippings, &c. The in-
ventor stated that the best results were obtained by
using 30 lbs. of an aggregate of a siliceous or other
hard nature, 3 lbs. powdered lime, and 18 ozs. boiling
water. No more of the materials were gauged at the
time than were sufficient to fill one mould, as the boil-
ing water caused the concrete to set very rapidly. This
material, after fifty years' exposure i^ still sound and
shows no sign of decay. No artificial stone equals, far
less excels, the strength and durability, sharpness, and
evenness of Portland cement concrete. This form of
artificial stone is now extensively used as a substitute

432 CEMENTS AND CONCRETES

for natural stone, for window heads, string courses,
sills, columns, copings, keystones, and many other archi-
tectural, constructive, and decorative features. Fig-
ures, animals, bas-reliefs, capitals, panels, can be made
in fine concrete with all the relief, undercut, and fine
detail which distinguishes high-class from inferior
work. Cast work has the advantage over in situ work
that any defect can be detected previous to fixing. The
methods of moulding and casting various works are
given in the following pages.

Concrete Dressings. — Architectural works, especially
large or plain parts, are generally cast in wood moulds.
If there are ornamental parts in the blocks, a combina-
tion of wood and plaster, and sometimes gelatine, is
used for the moulds ; wood for the main or plain parts,
plaster for circular or moulded parts, and gelatine for
undercut parts. The plaster or gelatine, as the case
may be, is screwed on or let into rebated parts of the
wood. Ornamental parts are sometimes cast separately,
and then fixed on the main cast. They may also be
cast separately and laid into the main mould (face
inwards), and the whole is cast together in a somewhat
similar way to that described for ** bedded enrich-
ments" in fibrous plaster cornices. »

Considerable skill and ingenuity has been displayed
in the construction of wood moulds for casting concrete
blocks for architectural purposes. Many methods have
been employed for fixing the sides and ends together,
and also to the bottom of the mould, leaving one or
more parts unfixed to facilitate the release of the cast.
The primitive method is to fix the various parts of the
mould with screws. This is a slow and unreliable
process, as the continual screwing and unscrewing for

HOW TO USE THEM 433

each cast soon wears the serew-holes, and the sides be-
come loose and out of square, causing the casta to get
out of their true form. Hinges, also hooks and eyes,
have been used for the same purpose, but they are
liable to the same defects as the screws when subject
to long use.

Thumbscrews to fit into iron sockets are also used,
but they are too expensive for ordinary work, and are
unsuitable for small moulds. One of the most simple
and reliable methods is the "wedge mould," invented
by an architect. It is easily made, and expeditious in
working. Even after long and constant use, the casts
are always accurate in form and size. The wedges and
the rebated ends allow the various parts to be correct-
ly fixed and held in position'. Illustration No. 27 shows
the method of construction. The various parts are

434 CEMENTS AND CONCRETES

named, and the sketch is self-explanatory. When the
moulds are extra deep, it is necessary to make two or
more sets of tenons and wedges at each angle. When
there are a large number of easts required the mould
ends are strengthened by binding the projecting ends
with hoop iron. This method has been adopted for
easting a lot of blocks. Illustration No. 28 shows two
useful kinds of moulds. Fig. 1 ia a simple form of
mould adapted for plain blocks, caps, lintels, &c. A, A,
are the sides, which are grooved into the ends B, B, and

Fig. a.

held together by the bolts and nuts, C, C, two on each
side. The bolts may be about % inch diameter, with
a good-sized square-head at one end, and a washer and
nut at the other. This, having no bottom, is termed a
bolted frame mould. It should be laid on a bench or
moulding board before the cast is filled in. Fig. 3 is
a section of a combined wood and plaster mould on the
wedge principle, adapted for casting a strong course
moulding. A is a moulding board, 1'/^ inches thick,
formed with two or more boards; a is one of two or
more cross ledges, 1 inch thrck, on which A, the ground,
is nailed. B is a width board, 1 inch thick, which is

HOW TO USB THEM 435

nailed on to A. This gives a point of resistaniee to the
plaster piece G and the side board G. D is a side board
on which E is screwed. E forms the sloping part of
the weathering. F is one of two or more vertical
wedges which hold D E in position. The sockets for
the wedges F are made between the cross ledges, so
that the wedge will project below the ground A. This
allows the wedges to be more easily driven out when
the cast is set. G is the back or plain side board. H
is a fillet, 1% inches square, screwed on to the ground
A. I and J are two folding wedges, or, in other words,
wedges driven in opposite directions. These hold G
in position. Two or more of these folding wedges are
required, according to the length of the mould. The
same remarks apply to the vertical wedges F. The lat-
ter form of wedge is only given as an alternative. The
end pieces are held in position by dropping them into
grooves in a similar way as shown in the previous fig-
ure, with the exception that the grooves are cut in the
sides instead of the ends. K is a gauge rule which is
used for ruling the upper surface of the cast fair. This
may also be done by working a straight-edge longi-
tudinally. The dotted line at L, the concrete, indicates
the wall line. The level part of the weathering up to
this line, or if splayed from the outer member of this
line, must be finished smooth to allow the water to run
freely off. When the cast is set, the wedges are with-
drawn, and the sides and ends released. The cast is
then turned over on its back end or top side on a board,
and then the plaster piece and the wood ground is taken
off. If the cast is green, it should be turned over on
old sacks or wet sawdust, so as to protect the arrises,
and avoid fractures.

436 CEMENTS AND CONCRETES

' niustpation No. 29 shows a method commonly
adopted for constructing moulds for sills and copinga.
Pig. 1 is the section of a mould for a window sill. A
is the moulding board, made with two or more pieces,
each 1% inches thick; a is one of two or more cross
ledges, made with 1 inch stuff, on which A is nailed. B
is the width hoard; made of % inch stuff, nailed on to
A. C is a hloek, ly^ inches thick, which is nailed on
to B. These blocks are placed about a foot apart, or
BO that they will carry the lining D, 1 inch thick. A

Fic. I,— StCTiOK OF Moum V0« Castikg Silu.
Fic. 3.— Section of Moui.R.rOR Casi-iko Coping.

grooTe or an iron tongue E is made in B, and a piece
of thick hoop iron or iron bar is placed loosely in the
groove before the cast is filled in. F is a fixed side,
1^4 inches thick. G is a fillet, l^^ inches square, nailed
on to F, and screwed on to moulding board A. H is a
loose side, I14 inches thick, on which the fillet I is
nailed. J is one of two or more clips, which turn on
a screw, and are used to hold the loose side H in {Ktsi-
tion. These clips are made and used in the same way
as described for fibrous slabs. As compared with
wedges, clips are always in position ready for use, are

HOW TO USE THEM 437

not liable to be Inislaid, and when the fillets are fixed
on to the side pieces, the clips keep the sides from
rising as well as expanding. K is a throating or water
grroov^, which is formed in the concrete L, with a rule
having a rounded edge. Two blocks, dished at the
inner ends, must be fixed one at each end of the mould,
so as to form a stool or bed for the superstructure. The
position and form ot the groove is obtained from sink-
ings cut in the end pieces of the mould. The end pieces
are held in position by grooves cut in the side pieces
in a similar way, as already described, with the excep-
tion that the grooves are cut in the side pieces, instead
of the end pieces. When setting out the mould, an
extra length must be allowed for the side pieces for the
grooves. A part of the upper surface of the cast (be-
ing the part which projects beyond the line of wall)
must be finished fair by hand at the same time as form-
ing the water groove. This must be done while the cast
is green. When the cast is released from the mould,
the iron tongue will be found firmly embedded in the
concrete. Fig. 2 is a section of a wood mould adapted
for casting wall copings. A is the ground of a mould-
ing board, which may be made of 1^-inch stuff, and in
2 or more widths ; a is one of two or more cross ledges,
1 inch thick, on which A is fixed. B, B, are blocks
about ly^ inches thick, placed about 1 foot apart. C,
C, are linings, 1 inch thick, nailed to B, B. D is a
fixed side, 1^4 inches thick. E is a fillet, 1^ inches
square, fixed to D, and then screwed on to A. F is a
loose side, 1^4 inches thick, on which is nailed the fillet
G, 1^ inches square. This strengthens the sides and
affords the fixing point for the clip H. The water
grooves I, I, and the hollowed part in the middle of the

438 CEMENTS AND CONCEETES

concrete J (made to save materials in weight) are
worked from the end pieces of the mould, which are let
into the grooves, as described in the previous diagram.
If the moulds are deep, wood or iron clamps may be
fixed across the sides to keep them in position, as shown
by K. The moulding boards in this and the previous
figures, if strongly made, can be used for a variety of
similar purposes. When introducing cast instead of
run moulded work, I used iron and zinc plates to
strengthen and make more durable plain surfaces on
wood moulds ; but owing to the expense and trouble in
fixing the plates to the woodwork, they were aban-
doned, and by using a better class of wood, and in-
durating the surface of the mould with hot paraffin
wax, sharp and clean casts were more cheaply pro-
duced. Cast-iron nioulds may be used where there is
a Hvge number of casts required. They may also be
advantageously used for stock designs, such as plain
moulded balusters. "Wood moulds are rendered more
durable and impervious to wet by brushing them with
Ixot paraffin wax, and then forcing it into the wood by
ironing with a hot iron. The use of paraffin wax and
oil has already been' described.

Mouldings Cast ^^In Situ," — Casting cornices, cop-
ings, &c., in situ is now frequently employed for con-
crete. The advantages of >,tb,js,. system over shop east
work, are, that the work is readily done, and the cart-
age or moving from the workshops to the building, and
the fixing, are dispensed with. :■ ....

Illustration No. 30 shows the method of constructing
and fixing various kinds of casting moulds for in situ
work.

Fig. 1 shows the section of a cornice, casting mould,

HOW TO USE THEM

440 CEMENTS AND CONCRETES

and supporting bracket. Wood moulds are generally
used for small or plain mouldings, but where the profile
is undercut or of an intricate nature, a plaster mould
is preferable, as it is easier and cheaper to construct a
plaster mould than cut the irons which are necessary
for a wood mould for a special design. Fibrous plaster
moulds may be used for this class of work, but to illus-
trate another method a combined wood and plaster
mould is given. M is a moulding board to strengthen
the plaster profile, and on which it is run. The board
may be made in two or more pieces, each about 1 inch
thick, and in width according to the depth of the mould-
ing, and in length as required, the whole being held
together by cleats H, which are nailed about 3 or 4 feet
apart. Broad-headed nails are then driven in at ran-
dom, leaving the heads projecting, to give a key for
the plaster profile P. The profile is then run with a
reverse running mould. It will be seen that this profile
is undercut, therefore a loose piece L is required to
enable the mould to ''draw off the moulding. The re-
verse mould and loose piece are constructed in the same
way as described under the heading of ** Reverse Mould-
ings.'* It may be here remarked that it is sometimes
useful to have an *'eye'' inserted in the loose piece to
give a better hold for the fingers when taking the|loose
piece off the moulding. The eyes are made by twisting
a piece of strong wire round the handle of a tool bruch,
leaving one end in the form of a ring, and the other
bent outwards so as to form a key. The eyes are fixed
about 3 or 4 feet apart, the fixing being done by cut-
ting a hole in the loose piece and bedding the shank of
the eye with plaster, and then cutting a slot in the
main part of the mould to receive the ring of the eye

HOW TO USE THEM 441

as shown at E. The mould is held in position by the
bracket B, fixed 4 or 5 feet apart. The mould is further
secured by the stay S, the other or inner end of the
stay is fixed on to the main wall. It will be understood
that a plaster mould for this purpose should be dry and
hard, and then well seasoned with linseed oil, or with
a hot solution of parafiin wax. After the mould is fixed
in position it is oiled, and then the concrete C is filled,
in, taking care that the surface of the mould is first
covered with a thin coat of neat cement. The mould
may be oiled with parafiin oil; but if the mould is in-
clined to ** stick," oil it with ''chalk oil," i. e., paraflSii
oil and French chalk, about the consistency of cream.

When the concrete is set, the brackets are removed,
and the mould taken ofP. The mould in this case would
draw in the line of the arrow A. The loose piece is
then taken off. It is here that the use of the eyes will
be found. Before removing the brackets it is advisable
to prop the mould, in case it may drop off and break
the fragile portions of the mould or parts of the cornice.
A heavy mould hanging in this position, especially if
the profile is flat, or in good working order, is apt to
drop, hence the necessity of props. If the mould clings,
or, as more generally called, ''sticks fast," gentle tap-
ping with a heavy hammer will ease or spring it, and
allow it to be taken off. A heavy hammer is more ef-
fective in making the mould spring than a light ham-
mer, as the force required for a light hammer is apt to
injure the mould. This is why a heavy hammer with a
flat head is best for plaster piece moulding.

J^ig. 2 is the section of a string moulding with the
casting mould and bracket. A chase is formed in the
brickwork to allow it to bond, and the joints and the

442 CEMENTS AND CONCRETES

surface of the brickwork are cut out and hacked to give
a further key to the moulding. M is the mould (in this
case made of wood). The profile is drawn without any
undercut parts, so as to allow the mould to draw off in
one piece. B is the bracket, and C is the concrete. The
same directions for casting Fig. 1 apply to this and
the other moulding here shown. A drip member, as
shown at the top member of both cornices, is generally
used for exterior mouldings, to prevent the water run-
ning over the wall surface.

Fig. 3 is the section of a wall coping and the casting
mould. M is the mould, a similar one being used for
the other side. A mould for this purpose is best formed
with flooring boards about 1 inch thick, and fixing them
together as shown. The drip D is readily formed by
sawing an inch bead through the centre, and nailing it
on the bottom. Two forms of brackets, B and B, are
here given. One is cut out of the solid, and the other
made of two pieces of wood nailed together.

Fig. 4 is the section of a casting mould for a saddle-
back coping. R is a quarter-round piece of wood fixed
in the angle of the mould to form a cavetto, which is
sometimes used in copings.' D is an angular-shaped
drip, sometimes used in place of a circular one. T is
part of a template used for forming the saddle-back of
the coping.

Fig. 5 is the section of a mould for a coping -with
splayed or chamfered angles. S is a triangular strip
of wood fixed in the angle and the top of the mould to
form the splays, and D is a circular drip.

Concrete mouldings that are deeply undercut or in-
tricate in profile may be cast in situ by the use of the
** Waste Mould Process."

HOW TO USE THEM 443

Modelling in Fine Concrete, — ^Figures of the human
and animal form, also emblems, trade signs, and build-
ings, are now being made in fine concrete. The work
may be executed in situ, or in the moulding shop, and
then fixed in position. For important works a plaster
model is first made, and placed in position, so as to
judge of the effect before committing it to the perma-
nent material. For this purpose the model is first
modelled in clay, and then it is wa^te-moulded, and a
plaster cast obtained. After the model is approved it
is moulded, and then cast in the fine concrete. The
material is composed of Portland cement, and a light,
but strong, aggregate ; and the cast is made in a similar
way to that described for casting vases. The material
may be colored as required to suit the subject. The
general method of executing figures *'on the round"
in fine concrete or Portland cement is to model the
figure direct in the cement on an iron fi^ame, and then
to fix it in its permanent position. This is effected by
first making a full-sized sketch of the proposed figure,
then setting out on this the form of the necessary iron-
work to serve as frame or skeleton to form an internal
support. This iron frame also forms a core to enable
the figure to be made hollow, and serves as a permanent
support for thin parts and extremities of the figure. .
The quantity, size, and form of the iron frame is regu-
lated by the size, form, and position of the figure. For
instance, if the model of a full-size lion is required, first
make a rectangular frame to suit the feet of the lion
and the base on which the figure stands. The base
frame is made of iron bars, 1% inches wide by ^ inch
thick, fixed on edge. Then set out four leg-irons, and
connect them on the base frame, and then set out one

444 CEMENTS AND CONCRETES

or two body-irons, and connect them with the leg-irons.
After this set out a looped piece to fit the contour of
the neck and head, and fix it to the body-iron. Now
set out the tail-iron. This is best formed with an iron
pipe, and it should be made to screw on to the body-
iron. This allows the tail to be imscrewed when the
model is finished, and screwed on af l;er the model is
fixed in position, thus enabling the model to be more
freely handled, and with less risk of breakage when
moving and fixing in its permanent position.

Having made the frame, place it on a stout modelling
board, keeping the base frame from 1 to 3 inches above
the board, according to the depth of the base ; the frame
being temporarily supported with four pieces of brick
or stone. This is done to allow the base frame to be
enveloped with concrete. This done, fix wood rules, cut
to the depth of the base, on the board, so as to form
a fence on all sides of the base. Then fill in the base
with concrete ; and when this is set, proceed with the
coring out, so as to obtain a hollow model.

In order to decrease the weight of concrete figures
**on the round," and to enable them to be more easily
handled and hoisted when fixing them in their perma-
nent positions, they should be made hollow. This is
effected by making a round skeleton frame with hoop-
iron, or with wire-netting, for the body, neck, and head,
and other thick parts. This metal skeleton must be
built on and securely fixed to the main iron frame. The
whole, or parts of the figure, may also be cored out with
shavings or tow, and held in position with tar bands or
canvas strips, dipped in plaster. Tow is an excellent
material for forming cores. By making up the inner
parts with dry tow, and then dipping tow in plaster toi

HOW TO USB THEM 44S

the outside coat; the core can be made to any desired
shape, and also leave the necessary thickness for the
concrete. To prevent the material slipping down by
its own weight, pieces of iron or wood, in the form of
crosses, are fastened with copper wire or tar rope to
the iron rods, which are used as single supports. These
iron or wood pieces must be fixed in all directions, and
in such a way that the material is held up by them.
For small extremities, such as fingers of human figures,
beaks of birds, fins of fishes, horns and tails of animals,
iron rods should be fixed on the main frame, and the
parts to be covered with cement must be notched or
bound at intervals with copper wire or tar rope. The
distance between the core and the finished face of the
figure is of course the actual thickness of the model.
This thickness may vary from 1 inch to 3 inches, or
even 4 inches at some parts. An actual thickness of 2
inches will be sufficient to give the requisite strength.

When the core is made, cover it with a coat of Port-
land cement and old lime putty, in the proportion of 3
of the former to 1 of the latter, and add sufficient tow
or hair to give tenacity. If there are open spaces in
the skeleton iron work, bridge them over with bits of
tiles and cement. The whole surface, after being coated,
must be well scratched with a nail, to give a key for
the roughing out coat. This scratched coat must be
allowed to set before proceeding with the actual model-
ling. The stuff for roughing out is composed of 2
parts of Portland cement and 1 part of fine aggregate.
Crushed bricks, stone, or pottery ware passed through
a sieve having a Yg inch mesh may be used as aggre-
gates. The finishing stuff is composed of fine sifted
Portland cement. The addition of a -fifth part of old

446 CEMENTS AND CONCRETES

lime putty to the cement makes the stuff more mellow,
and works freer and sweeter. The modelling is done as
described for in situ work. The finishing coat can be
colored to any desired tint, as already described.

Concrete Fountainsjh—'Fme concrete is an excellent
material for the construction of fountains. It is ob-
vious that a vast amount of cutting and consequent
waste of material is involved in the executing of foun-
tains, "on the round," when natural stone ft employed.
Saving of material, and a corresponding reduction in
the cost, is effected by use of a material that can be
easily cast, and is at the same time durable and im-
pervious. These qualities combined are found in arti-
ficial stone composed of fine concrete. Being readily
made in large blocks (any sized basin can be made in
one piece), there is no jointing required, as is the case
with terra cotta, which is another form of artificial
stone. Fountains composed of fine concrete are made
in a similar way to that described for making and cast-
ing vases.

Concrete Tanks. — Concrete tanks to contain water,
and for a variety of manufacturing purposes, are now
largely in use. They are strong and durable, and hav-
ing hard smooth surfaces, they are easily washed and
kept clean. Being impervious to vermin, damp, and
atmospheric influences, tfiey are the coolest and most
sanitary water cisterns that can be used. Cattle troughs
are best made in concrete. Concrete tanks have been
used as water and silicate baths for indurating con-
crete casts, and during their constant use for over a
decade no signs of cracks or damp are visible. They
were made in one piece, varying in size from. 6 feet up
to 18 feet long, 3 feet to 7 feet wide, 2 feet 6 inches to

HOW TO USE THEM 447

4 feet high, and from 3 to 4% inches thick. Some were
cast, but the large ones were made in situ. The method
of construction (for in situ work) being simple and ex-
peditious, the total cost is small. For a tank 9 feet long,
4 feet 6 inches wide, 2 feet 6 inches high, and 3^ inches
thick, first frame up wood sides and ends to the above
length, width, and height, then make inside b<)ards,
the lengths and widths being the same as above, less
the tank thickness, and the heights less the bottom
thickness. The sides and ends are hung by means of
cross battens laid on the upper edges of the outside
framing, and kept in position with inside stays. This
leaves an open and continuous space at the sides, ends,
and bottom. The constructive materials are 1 part of
Portland cement and 2 of fine slag or granite, gauged
stiflf, and laid over the bottom. Next, the open sides
and ends are filled up, taking great care that the whole
mass is thoroughly consolidated by ramming. The
stuff for the sides and ends should be laid in layers
from 6 to 8 inches deep, each layer being well rammed
before the next is laid.

The angles are strengthened by inserting angle irons
during the process of filling in. As soon as the concrete
is set the inner boards are removed, and if the surface
Is smooth or dry, it must be keyed with a coarse drag
or a sharp hand pick. It is then swept and wetted to
cleanse it and stop the suction, so as to ensure perfect
cohesion, and allow the final coat to retain its moisture
during the process of trowelling and the stuff setting.

The finishing coat is composed of neat cement, the
finer groimd the better, as percolation through con-
crete made with a finely ground cement is less liable
than when made with a coarsely ground cement.

448 CEMENTS AND CONCRETES

The final coat is laid about 3/16 inch thick, and pre-
ceded by brushing the surface with liquid cement to
'fill up all crevices, and afford better adhesion between
the surface and the final coat. When the stuff is firm,
it is well trowelled to a fine and close surface. The
outer boards are then removed, and the surface finished
in a similar way.

Concrete Sinks. — Concrete sinks can be made to any
desired size or form. They are cast in wood or plaster
moulds, and are composed of 1 part of Portland cement
to 2 parts of fine crushed granite or other hard aggre-
gate. They are made with rebated holes for traps. The
ordinary size are as follows : 2 feet 6 inches by 1 foot
8 inches ; 2 feet 9 inches by 1 foot 8 inches ; and 3 feet
by 2 feet, all 6 inches deep, and from 2 to 3 inches thick.

Garden Edging. — ^Plain and ornamented edgings are
now made in concrete. They are made in various
lengths. The most useful size is 3 feet long, 6 inches
deep, and 2 inches thick. They can be made to any
curve, and tinted* to any shade.

Concrete Vases.— During the last half-century thou-
sands of vases, composed of fine concrete — commonly
called ** artificial stone" — ^have been used for the dec-
oration of buildings and practical use in gardens, con-
servatories, &c. For vases that are cast in sections the
thickness of large and open parts, such as the *'bod^,'*
are regulated by means of a plaster core, which is
placed in the open mould. The contour of the core
must be so arranged that the cast will draw from the
core, or vice versa. For some forms of vases, the core
must be made in pieces similar to a piece mould. The
method of making, moulding, and casting — ^the latter
by the aid of a template instead of a core

HOW TO USE THEM 449

Concrete Mantel Pieces. — Chimney-pieces of all sizes
and shapes are now extensively made in fine concrete.
They are generally made in wood moulds, plaster
moulds being let in the main mould for ornamental
parts. They are often made in colored concrete.

Colored Concrete, — Concrete casts, also work laid in
situ, can be colored to imitate any natural stone. This
is effected by mixing mineral oxides of the required
color with the cement used for the surface coat. The
color coat should not exceed % inch in thickness, as
oxides are too expensive to use for the entire thickness
of the cast. The quantity of oxide to be added to the
cement depends upon the strength of the oxide. Some
are much stronger than others. Five per cent, of a
strong oxide will impart a close resemblance of the
desired color to the concrete, but a weak oxide will re-
quire from 10 to 15 per cent., and even 20 per cent., to
obtain the same color. Some of the red oxides range
in color from scarlet or Turkey red, gradually deepen-
ing to chocolate. Some oxides contain 95 per cent, of
pure ferric oxide, which is made from copperas, or,
scientifically speaking, sulphate of iron. This is a by-
product, and is frequently evolved from waste acid
liquors at tinplate works, and is obtained in large quan-
tities from South Wales. This kind of oxide is far
more suitable for coloring concrete than ochres and
most of the earthy oxides. Earthy colors, like Venetian
red and umber, soon fade and have a sickly appearance.
The oxides should be intimately mixed with the cement
in a dry state before it is gauged. The mixing is gen-
erally done by hand, but better results are obtained by
the use of grinding machine. It is a safe plan to try
▼atious proportions of color and cement and gauge

450 CEMENTS AND CONCRETES

small parts, and when set and dry select those most
suitable for the desired purpose. All cast work, as soon
as extracted from the moulds, should be examined, and
any blubs stopped and chipped parts or other minor
defects made 'good while the work is moist or green,
using neat cement and colors in the, same proportion
as used for the surface stuflF. Colored surfaces may be
greatly improved by brushing the cast as soon as set
with a solution of the same color as used for the sur-
face coat. A color solution, made by mixing the color
with water and a solution of alum, is very useful for
coloring Portland cement, with or without sand. If this
coloring solution is brushed over the surface while it
is moist or semi-dry, a good standing color can be ob-
tained without mixing color with dry cement. This
method will be found useful for sgraffitto, &c.

A novel and color-saving method, for coloring the
upper surfaces of slabs or other flat casts, is effected
by first filling in the mould in the usual way, then
placing the colored cement in a dry state in a hand
sieve, and then violently shaking or tapping the sides
of the sieve, so as to sprinkle the colored cement uni-
formly over the surface until it is nearly 1/16 inch
thick. The surface is then trowelled in the usual way.
The sprinkling must be done as soon as the main body
of the stuff is ruled off, so as to obtain a homogeneous
body. Another and a novel method which may be ad-
vantageously employed for finishing slab or other large
surfaces in a mould is as follows : A fine finished face
is more readily obtained by using a smoothing knife
(for brevity termed a ** shaver") than by a trowel. A
shaver is a piece of polished steel about 3 inches wide
and % inch thick, the length being regulated according

HOW TO USB THEM 451

to the width of the mould, and allowing about 8 inches
at each end for handles. For instance, for a slab 2 feet
wide, the shaver should be 3 feet long. This allows 2
feet for the surface of the cast, 3 inches to bear on the
rims of the mould, each 1^/^ inches wide ; 8 inches for
the handles, each 4 inches long; and 1 inch for play.
One edge or side is cut to an angle of 45®, so as to
form a cutting edge. The method of filling in, coloring,
and finishing the surface of the slab is as follows : First
fill in the mould with the concrete, ramming and beat-
ing it as already described until the stuff is about 1/16
inch above the mould rims, then clean off the stuff on
the rims with a wood template (rebated to fit the width
of the rims), and lay the shaver flat on the rims, keep-
ing the cutting edge outwards, and then push it for-
ward, keeping it flat on the rims, so as to shave off the
superfluous stuff. This done, sprinkle the colored ce-
ment, with the aid of a sieve, until about 1/16 inch
thick; then clean the rims again, and pass the shaver
forwards and backwards twice or thrice, which will
leave a straight, smooth, and uniform-colored surface.
This method effects a considerable saving in the amoimt
of oxide and of time. The thickness of the coloring
stratum is reduced mechanically to the minimum (about
1/32 inch), which is all sufficient for coloring purposes
where the surface is not subjected to frictional wear.

As already mentioned, bullocks' blood mixed with
cement gives a near resemblance to red brick, but it is
not a desirable material to work with, and the same
effect can be obtained by the use of red oxides. Red
sand, brick, and stone, all finely ground, have been em-
ployed for coloring cement surf aces^ but if too fine or
in large quantities they weaken the surface; and if

452 CEMENTS AND CONCEETES

coarse-grained they possess little coloring effect, be-
cause the particles are liable to show singly, causing a
spotty appearance, or the cement entirely covers the
surface of each particle of sand. Powdered glass, mar-
ble, flint, alabaster, metal filings, and mineral coloring
can be effectively employed for coloring concrete sur-
faces by mixing with the eement used for the surface
coat. The surface is improved by rubbing and stoning,
also polishing, after the work is dry. Other methods
and quantities of colors for coloring Portland cement
surfaces are given.

Fixing Blocks. — Concrete fixing blocks do not shrink,
warp, or rot. Consequently they are superior to wood
fillets, &c. They are principally used in concrete floors,
stair landings, and walls, as bearings and fixing points
for wire-lathing and fibrous plaster Ivork. Floor boards
may also be fixed to them. They are also built into
brick walls for similar purposes, as well as for external
wall tilings. For ceilings, stair sofiits, and landings,
the blocks are laid on the centrings where required,
and perlnanently secured by laying concrete between
and over them. For bearings and fixing flooring boards,
, they are secured flush.

TYPICAL SYSTEMS OF REINFORCED CONCRETE
CONSTRUCTIONS FROM VARIOUS SOURCES.

Of the interesting features of modern civil engineer-
ing, interesting because of their extreme novelty and
successful application, reinforced concrete is probably
most noteworthy because of its unique adaptability.
How striking is the influence of steel reinforcement is
best exemplified by a reference to Fig. 1. There two

HOW TO USE THEM 453

beams are shown designed to carry ordinary floor loads^
the one made entirely of concrete and the other of con-
crete with a sheet of expanded metal imbedded in the
tensile portion of the beam. The saving in mere weight
of concrete alone is apparent; and when we remember
that the adoption of floor beams entirely of concrete
means an increase of thickness of nine inches or as-
suming five to eight floors, an increase in the total
height of the building (with extra cost and heavier
walls, together with heavier foundations to carry them)
of from four to six feet, we «ee that even as regards
initial outlay for materials, the introduction of settle
reinforcement into concrete construction is of import-
ance.

So far as economy in initial cost of materials is con-
cerned, reinforced concrete is undoubtedly cheaper
than either concrete or steel alone. It is not very easy
to demonstrate this economy except by comparative
cost in individual cases, but an approach to a systematic
comparison has been made by Mr. Walter Loring Webb,
as follows: A cubic foot of steel weighs 490 pounds.
Assume as an average price that it can be bought and
placed for 4.5 cents per pound. The steel will therefore
cost $22.05 per cubic foot. On the basis that concrete
may be placed for $6 per cubic yard, the concrete will
cost 22 cents per cubic foot which is 1 per cent of the
cost of the steel. Therefore, on this basis if it is neces-
sary to use as reinforcement an amount of steel whose
volume is in excess of 1 per cent of the additional con-
crete which would do the same work, there is no econ-
omy in the reinforcement, even though the reinforce-
ment is justified on account of the other considerations.
Assimaing 500 pounds per square inch as the working

454

CEMENTS AND CONCRETES

compressive strength of concrete, and 16,000 as the per*
missible stress in steel, it requires 3.125 per cent of steel
to furnish the same compressive stress as concrete. On
the above basis of cost, the compression is evidently
obtained much more cheaply in concrete than in steel
— in fact, at less than one-third of the cost. On the
other hand, even if we allow 50 pounds per square inch
tension in the concrete and 16,000 pounds in the steel,
it requires only 0.21 per cent of steel to furnish the

Fig. I.-^These Beams Are Desi/^ned to Carry the Same

Iioad. The Upper is of Reinforced Concrete^ the

Lower of Plain Concrete.

same strength as the concrete, which shows that, no
matter what may be the variation in the comparative
price, of concrete and steel, steel always furnishes ten-
sion at a far cheaper price than concrete, on the above
basis at less than one-third of the cost. The practical
meaning of this is, on the one hand, that a beam com-
posed wholly of concrete is usually inadvisable, since its
low tensile strength makes it uneconomical, if not actu-
ally impracticable, for it may be readily shown that,
beyond a comparatively short span, a concrete beam
will not support its own weight. On the other hand»

HOW TO USE THEM 455

on account of the cheaper compressive stress furnished
by concrete, an all-ateel beam is not so economical as

Fix. 2.— Tfpes of Steel Reinlbrcinx RAds.

a beam in which the concrete furnishes the compres-
sive stress and the steel furnishes the tensile stress.

Pig. 8,— A Beinforced Cuncrete Pier for Railway

Traffic

456 CEMENTS AM) CONCRETES

signed by using steel I-beams supporting a fire -proof
concrete floor, and, that of a concrete floor having a
similar floor slab but making the beams as T-beams of
reinforced concrete.

A good idea of reinforced concrete construction can
be obtained from Fig. 3, which is an isometrical pro-
jection of a portion of a pier strong enough to carry
the heaviest railway tralRc. The disposition of the
steel work is shown in the piles, the main girders, and
beams; and the manner in which the steel rods run-
ning along the tensile or bottom side of the girders
and beams are bent up over the top of the pile, which
is here the tensile member (the beams being continu-
ous), and then down again to the bottom of the girders
and beams, is most instructive.

Fi;. 4.-— Method of Joining Cohuniw and Floors.

The sections of the steel employed vary in different
systems, being rouiid, flat, square, angle, and tee — Fig,
2. In all cases the simplest section is the best, as it
costs less, and readily allows the concrete to be rammed
into the closest contact with the entire surface of the
armoring. In America the Ransome system is most
extensively used — a system in which a bar of twisted

HOW TO USE THEM 457

steel is employed. Small sections are better than large
ones, for by their use we obtain a more uniform dis-
tribution of stress in the steel; we can also readily
bend and work them into any required shape; and
finally the most economical disposition of material is
obtained, the metal being placed at the maximum dis-
tance from the neutral axis.

. Fig. 6.— The Uonier System.

Expanded metal meshing (Pig. 6) is increasingly em-
ployed, more particularly in the lighter forms of con-
struction. It consists of sheets of metal which have
been mechanically slit and expanded, so as to produce
a. network. This type of reinforcement has many and
obvious advantages. Its mere existence is proof of good
steel, and it forms an excellent key for concrete too
thin to permit reinforcement in the form of rods ; thus
it is very useful for concrete plaster, ceiling, and parti-
tion wall work. A good example of reinforced con-
crete in which expanded metal is used may be found
in the Monier system (Fig. 5). An improvement on

458

CEMENTS AND CONCRETES

this system is the Clinton method (Fig. 11) of using
an electrically welded wire netting in combination with
concrete. Clinton fabric consists of drawn wire of 6
to 10 gauge, which may be made in lengths up to 300
feet. The system is therefore a continuous bond system,
which prevents the entire collapse of a span unless the
weight imposed is sufficient to break all the wires.

Fiff« 67T-£xpanded MeUl.

Columns and Piles. — ^Reinforced columns are made
with either square, rectangular, or circular sections.
They are reinforced with from four to twenty rods, the
diameters of which vary from % to 2^ inches. The
rods are placed as nearly as practicable to the circum-
ference of the column, so as to give the greatest radius
of gyration for the section ; but they are never placed
so near the surface that they have not at least one or
two inches protective covering. The steel so disposed
is al>le to take up the tensile stresses which may be

HOW TO USE THEM 459

induced in the column by eccentric loadrng, lateral
shock, wind pressure, and the pull of belting.

Columns and piles are made in wooden boxes, each
consisting of three permanent sides and a fourth side
■which is temporary and removable. Under the patent
rights of Francois Hennebique the reinforcing is placed

.-Baaaema ayilsa (^ EneUic Cu1iibM>

in these boxes, and adjusted by gauges to within one or
two inches of the sides. The concrete is laid and
rammed, about six inches at a time, with small hand
rammers. The open side of the box is built up by
battens fitting into grooves in the permanent sides, as
the work proceeds ; this enables inspection of the work

460 CEMENTS AND CONCRETES

to be made, and facilitates the placing of the ties at the'
proper positions. The ties are made of roancl wire 3/16

ftg, 8,— Wood CMterinK ondBuBomfr Steel Ban for 60-ftat
nora-Spub

inch diameter and are dropped down over the top of
the steel rods. They arti spaced down two-inch centres

HOW TO USE THEM 461

at the bottom and top, to twelve-ineh centres in the
centre of length of the column, and are Intended to
prevent the steel rods from spreading out under the.
action of longitudinal loads. Fig. 4 shows the method
of joining columns to the floor.

In the Ransome columns as exemplified in a recently
constructed factory building (Pig. 7), the vertical re-
inforcement consists of round rods with the connections
lOade about 12 inches above the floor line; in order that

462 CEMENTS AND CONCBETES

these rods might be continuous the ends were threaded
and connected with sleeve nuts, thereby developing the
full strength of the rods. Horizontal reinforcement
■was also used, consisting of hoops formed by a spiral

Fi^. 10.— Slabs of Concrete Ready for Koof. .

made from % inch diameter soft wire, having a pitch
or spacing of 4 inches in the basement columns, and
gradually increasing to a pitch of 6 inches in the top
story (Fig. 12).

According to Mr. Henry Longcope the first innov^
tion in concrete piles was the sand pile, produced hy

HOW TO USE THEM 463

driving a wooden form in the

ground and withdrawing it, ^

the hole being filled with
molBt sand well rammed. The
next method adopted was to
drive a metal form into the
ground and after withdrawal

to £11 the hole with concrete. ii

This was not successful, as it ^

was open to the serious objec- _

tiou that on withdrawing the S

form, the ground would col- ^

lapse before the concrete could Jj

be inserted. Still another 8

method was introduced, which ■§■

consisted in dropping a cone-
shaped five ton weight a num-
ber oi times from a consider-
a,ble height, in order to form
a hole, which was afterward
filled with concrete. This
' method never passed the ex-
perimental stage. Coining to
more successful systems we
may mention a method of
moulding a pile of concrete,
allowing it to stand, and then
driving it into the ground, a
cap being used to protect the
head.

Of modem systems which
have proven successful, Gil-
bteih's pile must first be re-

CEMENTS AND CONCRETES

HOW TO USE THEM 465

corded. Gilbreth used a molded corrugated taper pile,
cast with core hole the entire length of the i^ile, which is
jetted down by a water jet and finally settled by hammer
blows.

Features which recommended the Gilbreth piles are
the opportunities for complete inspection before driv-
ing and the fact that they save time because they can
be cased while excavation is going on, After bein^
driven they can be loaded immediately. Naturally they
present considerable skin friction. The making of these
piles above the ground surface also does away with the
possibility of their being damaged or squeezed out of
shape by the jar occasioned by driving forms for ad-
joining piles.

Still another method is used by Raymond. * Under
this system piles are usually put in by either of two
methods, the jetting method or the pile core method.
The water jet system is used only where the material
penetrated is sand, quicksand, or soft material that will
dissolve and flow up inside the pile when the water is
forced through the pipe, thus causing the shell to settle
until it comes in contact with the next shell, and so on
until the desired depth has been reached. The shells

. are filled with concrete simultaneously with the sinking
process, and when necessary spreads are attached to
keep the hole in perfect line with the pipe. The ^
inch pipe is left in the centre of the pile and gives it

. greatly increased lateral strength. If desired, the
lateral strength may be further increased by inserting
rods near the outer surface of the concrete. By this

. method, piles of any size up to two feet in diameter at

^ the bottom and four feet at the top can be put through

466 CEMENTS AND CONCRETES

any depth of water and to a suitable penetration in
sand or silt (water sediment).

The pile-»core method is the one most generally used
for foundation work and consists of a collapsible steel
pile core, conical in shape, which is incased in a thin,
tight-fitting metal shell. The core and shell are driven
into the ground by means of a pile driver. The core
is so constructed that when the desired depth has been
reached it is collapsed and loses contact with the shell,
so that it is easily withdrawn, leaving the shell or cas-
ing in the ground, to act as a mold or form for the
concrete. When the form is withdrawn, the shell or
casing is filled with carefully mixed Portland cement
concrete, which is thoroughly tamped during the filling
process.

The simplex system userf another method in which
the driving form consists of a* strong steel tube, the
lower end of which is fitted with powerful tooth jaws,
which close together tightly, with a point capable of
opening automatically to the full diameter of the tube
while being withdrawn. The point of the form closely
resembles the jaws of an alligator. At the same time
the form is being withdrawn, the concrete is deposited.

It is so evident that concrete is vastly superior to
wood in the construction of piles that it is almost su-
perfluous to mention the points of superiority. Con-
crete is not subject to rot or the ravages of the teredo
worm, neither can the piles constructed of concrete be
destroyed by fire, and no cost is attached for repairs.
While it is not possible to give accurate statistics as to
the life of a wooden pile, as it varies so much under
different conditions, yet we know that in some cases
a wooden pile is rendered worthless in a very few years^

HOW TO USE THEM 467

especially ^hen the surrounding material is composed
of rotted vegetation, or where the pile is exposed by
the rise and fall of tides. It is also impossible to state
the exact coat of a concrete pile, as it varies also ac-
cording to conditions. Ordinarily speaking, a concrete
pile will cost from one and one-half times or two times
as much as a wooden pile; but in order to illustrate
where a saving can be made, the following extract is
given from a report on the piles driven at the United
States Naval Academy at Annapolis, Md. :

''The original plans called for 3,200 wooden piles
cut off below low water with a capping of concrete.
Tq get down to the low water level required sheet pil-
ing, shorting and pumping, and the excavating of near-
ly 5,000 cubic yards of earth. By substituting concrete
piles, the work was reduced to driving 850 concrete
piles, excavating 1,000 cubic yards of earth and placing
of 1,000 cubic yards of concrete."

In the work mentioned, the first estimate for wooden
piles placed the cost at $9.50 each, while the estimate
for concrete piles was placed at $20 each, yet the esti-
mate based on the use of wood piles aggregated $52,840^
while the estimate based on the use of concrete piles
was $25,403, or a total saving in favor of concrete of
over $27,000.

In several instances piles have been uncovered to
their full depth, and they were found to be perfectly
sound in every particular. By surrounding the opera-
tion with the safeguards provided, it is almost impos^
sible to make a faulty pile. The concrete is made as
wet as good practice will allow. Constant ramming and
dropping the concrete from a considerable height tend
to the assurance of a solid mass, then the target on

les CEMENTS AND CONCRETES

the ramming line or the introduction of an electric light
into the form shows what is being done at the bottom
of the form.

Floors, Slabs and Roofs. — The system of construction
for floors, slabs, and roofs is determined by the extent
of the work and the nature of the loads to be carried.
If intended for small buildings and offices, the items
can be made before erection (Figs. 9 and 10) ; but in
the case of warehouses, factories, piers, and jetties,
where live loads and vibrator stresses have to be borne,
a monolithic structure is secured by building in molds
directly on the site. For the lighter classes of 'mono-
lithic structure, expanded metal is admirably suitable;
it is also much used for the roofs of reservoirs, and for
thin partitioned walls. The meshing is simply laid
over the ribs or floor beams, which have been already
erected, and the green concrete is applied to the acquired
thickness, being supported from below by suitable sup-
porting work, which is removed as soon as the concrete
has set. In cold storage factories, the floor beams and
ceilings are invariably erected first, the floor being laid
afterward. The ceiling is then solid with the floor
beams on their under side, and the floor is solid with
them on their upper side, the air space between being a
great aid to the maintenance of a low temperature for
refrigeration.

In the Monier floors the reinforcement consists of
round rods varying from ^4 inch to % inch diameter.
The rods are spaced at about six times their diameter,
and are crossed at right angles, being connected by
iron wire bound round them. This artificial method of
securing the rods takes considerable time, and is thus
a somewhat costly process. To produce continuity ol

HOW TO USE THEM 469^

metal/ the different lengths of rods are overlapped foi;
about 8 to 16 inches, and bound with wire.

The Sehluter are similar to the Monier floors, but
the rods are crossed diagonally, and the longitudinal
rods are of the same size as the transverse ones. Tho-
Cottancin floors have their rods interlaced like the;
canes of a chair seat or a basket, 'and the Hyatt floors
have square rods with holes through which small trans-:
verse rods pass. Over fifty systems of reinforcing are
in use, and in most cases the only points of difference
are the shape of the section and the method of attach-
ment and adjustment.

Beams, — It is obvious that, as the span increases, a
limit will soon be reached beyond which it is not eco-
nomical to use plain floor slabs, for their dead weight
becomes of such magnitude as to prohibit their use. We
have thus to resort to a division of the main span by
cross beams resting on columns, and the floor is laid
on these beams, which are arranged to take as much of
the load as to render it possible to reduce the thick-
ness of the floor within reasonable limits. Keinforced
concrete beams are typical of the construction in which
the merits of two component materials are made to
serve a common end ; but in the particular case of steel
and concrete, the actual part played by the steel is
not at all well understood.

Speaking generally, beams do not differ in construc-
tional details from floors. The same reinforcement is
used in both, the only difference being, that as beams
are usually deeper than floors, the shearing stresses be-
come more pronounced, the greater provision has to be
made for them by a liberal use of stirrups or vertical
binding rods. In some systems the reinforcement con-

470 CEMENTS AND CONCRETES

«ists entirely of straight rods, disposed in any part of
the beam where tensile stresses are likely to be called
into play. In others, specially bent rods are joined or
welded to straight rods, disposed and when welding has
to be done it would appear that wrought iron is more
suitable than steel.

It is usual to arrange the dimensions of the beams
SO that the whole of the compressive stresses are taken
by that portion of the concrete on one side of the netf-
tral axis; but in some cases, as with continuous beams
or heavy beams of small depth, a portion of the rein-
forcement is disturbed along compressed portion of the
beam, the steel rods either ^taking up the excess of
compressive stress over that at which the concrete can
be safely worked, or else taking up the tensile stresses
at the places where they occur over the supports. . As
a general rule we may take it that the economical depth
for a reinforced concrete beam, freely supported at
both ends, is one-twentieth the span, and is thus ap-
proximately the same as that of a steel girder of equal
strength. Reinforced concrete beams are now made for
spans up to 100 feet for buildings, and 150 feet for
bridges. But for each class of work beyond this limit,
the weight becomes excessive. Several arched ribs,
for much greater spans have^ however, been success-
fully built.

The beams are made in much the same way as piles
and columns; they can be made in sheds on the site,
or in the actual position they are to occupy when fin-
ished. The ceiling and beams are erected first, the
floor being afterward worked on the top of the beams.
We thus obtain a very perfect monolithic structure in
which any vibration set up by machinery, falling loada^

HOW TO USE THEM 471

etc., will be of much less extent than with any ordinary
type of building, in which there is often a great want
of rigidity, the beams and arches being loose and 8^ble
to vibrate independently of other parts of the struc-
ture.

Ccncrete being as weak in shear as in tensiou, pro-
visioQ is ateo required to take the shearing stresses.
Some American designers have to this end patented
special forms of reinforcement bar, in which each main
tension bar has projecting upward from it ties inclined
at the angle of 45 deg. (Kahn system.) These ex-
tend ^o the top of the bar and take the tensile stresses
arising from the shear. The corresponding compres-
sive stress at right angles to this is carried by the con-
Crete. The system is efficient and on large spans, where
weight must be reduced to a minimum, it has its ad-
vantages.

Thus, in the Ransome system (Fig. 12), the shearing
stresses at the end of a beam are taken up by inclined
reinforcing rods imbedded in the concrete at the junc-
tion of beam with column.

Arches. — Concrete has long had an extensive ap-
plication in the building of arches, but until the in-
troduction of reinforced concrete the arches that could
be economically and safely constructed were limited to
spans of a few feet. The general rule that the line of
resistance fell within the middle third had to be ob-
served for simple concrete arches, as for those in brick-
work and masonry; and the thickness of the arches
at the crown was thus approximately the same whether
built in either of these materials. The introduction of
steel reinforcement, however, made it possible not only
to reduce the thickness of the ring of a given load-

CEMENTS AND CONCRETES

HOW TO USE THEM

carrying capacity, but by suitably providing for nne
tensile stresses to enable arches of much greater span
and smaller rise to be built. Some general types of
arches in reinforced concrete p,re shown in Figs. 13, 14,
15 and 16. Fig. 13 shows an ordinary arch with top
and bottom armature. In many cases where the ten-
sile stresses can safely be carried by the concrete the
top armature can be omitted. In the Melane arches,
shown in Fig. 14, the top and bottom armatures are
connected. by ligatures, and in the Hennebique arches
(Fig. 15) stirrups are used. As a general rule, hinges
should be built at the sti:ingings and the crown, for the
calc.ulations are much simplified, and the line of re-
sistance goes through the hinges; the arches also ad-
just theinselves better to the load and to any slow
temperature changes, and when the centering is struck
the arch can better take its bearings without cracking.
The methods of calculations for arches are as numer-
ous as those for beams, and generally speaking are as
irrational. The Monier system is the one most gen-
erally adopted, and over 400 bridges built on this sys-
tem now exist in Europe. In America expanded metal
and Clinton electrically-welded fabric are often used.
An example of the latter construction will be found in
Pig. 17.

SOME MISCELLANEOUS ITEMS.

Lint els. -^CouGrete lintels and beams are fast super-
seding those made. of stone and wop4» Lintels are
generally cast and then fixed.

474 CEMENTS AND CONCRETES

HOW TO USB THEM 475

Concrete Walls. — ^Many ingenious plans have been
introduced as substitutes for wood framing for retain-
ing concrete while constructing walls and partitions.
The most simple method is as follows : Cast a number
of concrete angle slabs with an L section, and then
place them level in contrary directions, thus [ [,
spaced to the width of the proposed partition or wall
until the desired length of wall is completed, and, fill
the openings with rough concrete. When set, place
another row on this (taking care to break the joints by
overlapping), and so on, until the desired height is
obtained. Concrete for walls formed in situ should be
deposited in layers, taking care that each layer is thor-
oughly rammed and. keyed, as described under the
heading of ** Ramming." A suitable finish for ordi-
nary purposes, for rough walls built in situ, may be
obtained by *' rough trowelling." This is done by
first gauging 1 part of Portland cement, 1 part of old
lime putty, and 2 parts of sand. The adding of lime
renders the stuff more plastic and easy to work, with-
out decreasing the impermeability of the work. This
'4imed cement" is applied with a hand-float, and is
thoroughly worked into the crevices of the concrete,
but leaving no body on the" surface. The surface is
then finished by brushing with a wet stock-brush. The
walls should be well wetted before the stuff is applied.

Strong Booms, — Concrete is frequently employed in
the construction of strong-rooms that are situated
underground, and are rendered damp-proof as well as
burglar-proof, which is useful for the storage of docu-
ments.

Concrete Coffins and Cementation. — The great im-
provements in the manufacture of Portland cement

4tft CEMENTS AND CONCEETES

during the last decade has so cheapened and improved
the quality as to bring it more and more to the front
as one of the most useful and important materials for
a variety of purposes. One of the latest uses found for
it is in the construction of cofi5ns, by the author, whose
invented and registered idea was that such a cofl^,
made of specially prepared metallic concrete, would
be impermeable, and practically indestructible, and
that it would obviate the danger of spreading the
poisons of disease by preventing the escape of noxious
gases. The lid having a strong piece of plate glass
embedded in the concrete, and directly over the face,
enabled the mourners to see the features of the depart-
ed. The edge of the open coffin had a sunk groove,
and the lid a corresponding projection, only smaller,
to allow for a coat of fine cement. When the joints
were bedded and pressed together until the excess ce-
ment oozed out, the coffin was hermetically sealed.
The* coffin should be left uncovered by cement for
identification, and so that friends could view it until
the time of removal to the cemetery. The face could
then be covered with quick-setting cement, which, join-
ing with the other portion of cement, would perma-
nently embalm the body, which would further be pro-
tected by fixing the lid in a similar way. If the prop-
erties of this class of coffin are taken into considera-
tion, the expense will be comparatively less than that of
wood. If expense is not a special consideration, the
coffin can be enriched with armorial bearings or other
devices. The concrete may also be polished like real
granite. One objection was raised as to the weight,
biit the old stone coffins and those of oak lined with
lead were also heavy. Besides, the weight would be

HOW TO USB THEM 477

di^protectioh against body-snatchers, atid bearing in
mind that a coffin is only moved about once in a life-
time, or rather at death, the question of weight is uur
important. Cementation, from a sanitary point of
view, would be equal if not superior to cremation. In
case of an epidemic, the coffins could be cemented at
once, and stacked in the cemetery until graves or vaults
were prepared for them. It may be safely said that it
is a clean, safe, effectual, rapid and sanitary method
of disposing of the dead. If their manufacture should
not cause any great amount of extra employment for
plasterers, the latter can at least make their own cof-
fins, in frosty weather, when most works are stopped,
and they could use them as baths during their life-
time.

Stonette. — Stonette is a composition of Portland ce-
ment and fine aggregate, to imitate any kind of stone,
and so made that it can be carved the same as natural
stone. The Portland cement must be thoroughly air-
slaked, finely sifted, and gauged with the natural ag-
gregate in the proportion of 2 of cement to 7 of ag-
gregate. The aggregate is composed of finely crushed
natural stone, the same as that to be imitated. This
should be passed through a fine sieve. It is necessary,
when imitating some stones, to add a small portion of
oxide to counteract the color of the cement. If a very
white stone is being imitated, the addition of a small
proportion of whiting or French chalk or well-slaked
white limestone, is necessary to obtain the desired
color. The material should be gauged stiff, and then
well rammed into the mould. The carving is best done
while the cast blocks are green.

TUe Fixing, — Tile fixing is in some places a sepa-

478 CEMENTS AND CONCRETES

rate branch of the building trade, but it is generallj
recruited from the ranks of plasterers, and in some
districts it is done by plasterers. As regards the pro-
cess of placing the tiles, it is best to work from the
centre of the space, and if the design be intricate, to
lay out a portion of the pavement according to the
plan, upon a smooth floor, fitting the tiles together
as they are to be laid. Lines being stretched over the
foundation at right angles, the fixing may proceed,
both the tiles and the foundation . being previously
soaked in cold water, to prevent the too rapid dry-
ing of the cement, and to secure better adhesion. The
border should be left until the last. Its position and
that of the tiles are to be obtained from the drawing,
or by measuring the tiles when laid loosely upon the
floor. The cement for fixing should be mixed thin, in
small quantities, and without sand. It is best to float
the tiles to their places, so as to exclude air, and fill
the spaces between them and the foundation. For fix-
ing tiles in grate cheeks, sides and backs of fire-places,
etc., equal parts of sand, plaster and hair mortar'may
be used. These materials are sometimes mixed with
hot glue to the consistency of mortar. The tiles should
be well soaked in warm water. Keen's or other white
cements are used as fixing materials for wall tiles, neat
Portland cement (very often killed) being generally
used for floor work. Tiles may be cut in the follow-
ing manner : Draw a line with a pencil or sharp point
where the break is desired, then placing the tile on a
form board, or embedding it in sand on a flagstone,
tap it moderately with a sharp chisel and a hammer
along the line, up and down, or scratch it with a file.
The tile may then be broken in the hand by a gentle

HOW TO USE THEM 479

blow at the back. The edges, if required, may be
smoothed by grinding or by rubbing with sand and
water on a flat stone. Tiles may also be sawn to any
desired size. Cement should not be allowed to harden
upon the surface of the tile if it can be prevented, as
it is diflBcult to remove it after it has set. Stains op
dirt adhering to tiles may be removed by wetting with
diluted muriatic acid (** spirits of salts''), care being
taken that the acid is all wiped oflf, and, after wash-
ing, the superfluous moisture must be wiped oflf with
a clean, dry cloth. In order to obtain a sound and
straight foundation, which is imperative for good per-
manent tile fixing, the substratum, whether on walls or
floors, should be composed of Portland cement gauged
with strong sand or similar aggregate in proportion
of 1 of the former to 3 of the latter. The surface must
be ruled fair and left rough, so as to form a fair bed
and key for the fixing materials and tiles.

Setting Floor and Wall Tile. — ^As this work properly
belongs to the plasterer, where no regular tile setter is
available, I have thought it proper to publish the fol-
lowing instructions for doing this work, which are
taken from a treatise prepared for the Tile Manufac*
turers of the United States. This treatise, in pamphlet
form, was intended for distribution among buyers and
workers in tiles, and the directions and suggestions
laid down in it are of the best, and quite suited to the
wants of the workingmen:

Foundations, — A good foundation is always neces-
sary, and should be both solid and perfectly level. Tile
should always be laid upon concrete foundation, pre-
pared from the best quality of Portland cement and
clean, sharp sand and gravel, or other hard material.

480 CEMENTS AND CONCRETES

{Cinders should never be used, as they have a tendency
to destroy the life of the cement and cause it to dis-
integrate.) A foundation, however, may also be formed
of brick or hollow tile embedded solidly in and covered
with cement mortar. Concrete should be allowed to
thoroughly harden before laying the floor, and should
be well soaked with water before laying the tile.

Lime mortar should never be mixed with concreting.

Concrete should consist of one part Portland cement,
two , parts clean sharp sand, two parts clean gravel,
and thoroughly mixed with sufficient water to form a
hard, solid mass when well beaten down into a bed,
which should be from 2y2 inches to 3 inches thick. If
the concrete bed can be made over three inches in
thickness, the concrete can then be made of one part
Louisville cement^ one part clean sharp sand, one part
clean gravel and thoroughly mixed with sufficient wa-
ter, as above described.

For Floors. — The surface of the concrete must be
level and finished to within one (1) inch of the fin-
ished floor line, when tile ^^ inch thick is used, which
will leave a space of ^2 iiich for cement mortar, com-
posed of equal parts of the very best quality Portland
cement and clean sharp sand. The distance below
the surface of the finished floor line, however, should
be governed by the thickness >of the tile.

For Wood Floors. ^When tiles are to be laid on wood
flooring in new buildings the joists should be set *ive
inches below the intended finished floor line and spaced
about 12 inches apart and thoroughly bridged, so as to
make a stiff floor, and covered with one-inch boards
not over six inches wide (boards three inches wide
preferred), and thoroughly nailed, and the joints %

HOW TO USE THEM 481

ineli apart to allow for swelling. (See No. 31.) (A
layer of heavy tar paper on top of wood flooring will
protect the boards from the moisture of the concrete,
and will also prevent any moisture from dripping
through to a ceiling below.)

In Old Buildings. — Cleats are nailed to joists five
inches below the intended finished floor line, and short
pieces of boards % inch apart fitted in between the

Flff. ts.

joists upon the cleats and well nailed, and the joists
thoroughly bridged. The comers on the upper edge
of the joists should be chamfered off to a sharp point
(see Fig, 32), as the flat surface of the joists will give
an uneven foundation. When the strength of the
joists will permit, it is best to eut an inch or more oflE

482

CEMENTS AND CONCRETES

the top. (Where joists are too weak, strengthen by
tHoroughly nailing cleats six inches wide full length
of joists.) When the solid wood foundation is thus
prepared, concrete is placed upon it as above directed.
Where Steel Beams and hollow tile arches are used,
frequently very little space is left for preparing a
proper foundation for setting tile, as the rough coating
is usually put in by the hollow tile contractor to pro-
tect his work, but this covering should always conform

ffttfi'

Figr. 33.

to the requirements for a solid tile foundation. Should
this not be the case, the tile contractor should remove
suflScient of the covering to allow him to put down a
foundation that will insure a satisfactory tile floor.
(Cinders, lime, mortar or inferior material must never
be used.)

The tops of iron beams should be from three to four
inches below the finished floor line, to prevent floors,
when finished, showing lines of the beams.

For Hearths. — The foundation for hearths should be
placed upon a brick arch, if possible, to ensure perfect
fire protection, and then covered with concrete in the
same manner as directed for tile floors. If placed
upon a sub-foundation of wood, the concreting should
be at least six inches thick. (See Figs. 34 and 35,)

HOW TO USE THEM

484 CEMENTS AND CONCRETES

For Walls. — When tiles are to be laid on old brick
walls the plaster must be all removed and the mortar
raked out of the joints of the brick work to form a key
for the cement. On new brick walls the points should
not be pointed. When tiles are to be placed on stud-
ding, the studding should be well braced by filling
in between the studding with brick set in mortar to the
height of tile work (see Fig. 36) ; or brick work may be
omitted and extra studding put in and thoroughly

bridged, so as to have as little spring as possible, and
this studding then covered with sheet metal lathing.
(See Fig. 37.) {Tile must never Be placed on wood latk
or on old plaster.) The brick walls must be well wet
with water and then covered with a rough coating
- of cement mortar, composed of one part Portland ce-

HOW TO USE THEM 4SS

ment and two parts clean sharp saiid. When tiles are
placed on metal lathing, hair should he mixed with the
cement mortar to make it adhere more closel7 to the
lath. The cement mortar should be % inch thick, or
Bafiicient to make an even and true surface to within
one (1) inch of the intended finished surface of the
tile, when tile Yi inch thick is used, which will allow

a'space of Yo inch for the cement mortar, composed as
above for rough coating the walls. The face of the
cement foundation should be roughly scratched and
allowed to harden for at least one day before com-
mencing to lay the tile. If any lime is mixed with the
cement mortar for setting the tiles, it should never
exceed 10 per cent., and great care must be nsed to
have the lime well slaked, and made free from all

486 CEMENTS AND CONCRETES

lumps by running through a Qoarse sieve, in order to
guard against ** heaving" or *' swelling/' and thus
loosening or ** lifting" the tiles.

Important — The foundation for both floor and wall
tiling should be thoroughly brushed, to remove all dust
and small particles adhering to it, and then well wet
before putting on the cement mortar. To ensure a
perfect bond it is best to coat the foundation by brush-
ing over it pure cement mixed in water.

Cement — The very best quality of Portland cement
should always be used for setting either floor or wall
tile and for grouting the floors, and the very best
quality of Keene *s Imported Cement for fllling the
joints in the wall tiling.

Sand. — Clean, sharp grit sand, free from all salt,
loam or other matter, and perfectly screened before
mixing with the cement, should always be used.

Mortar. — ^For floors or vitreous tiles, should be com-
posed of equal parts of cement and sand^ and for wall
tiles one (1) part of cement cmd two (2) parts sand.
The mortar should not be too wet, but should be rather
stiff, and should always be used fresh, as mortar, when
allowed to set before using, loses a portion of its
strength.

Soaking. — Tiles must always be thoroughly soaked
in water before setting^ which makes the cement unite
to the tiles.

The Tiles for the Floors are first laid out to ascer-
tain if they are all right and compared with the plan
provided for laying the floors. Strips are then set,
beginning at one end of and in the centre of the room,
and level with the intended finished fioor line. Two
sets of guide strips running parallel about 18 to 30

HOW TO USE THEM 48T

inches ^>art should be set &TSt. (See Fig. 38.) The
mortar is then spread between them for about six to
ten feet at a time, and level with a screed notched at
each end, to allow for the thickness of the tiles. The
- tiles are placed upon the mortar, which must be stiff
enough to prevent the mortar from working up be-

FlE-SS.

tween the joints. The tiles are to be firmly pressed
into the mortar and tamped down with a block and
hammer until they are exactly level with the strips.
When the space between the strips is completed, the
strips on one side of the tile is moved out 18 to SO
inches and placed in proper position for laying an-
other section of tile, using the tiles which have been

488

CEMENTS AND CONCRETES

laid for one end of the screed, and the laying of tU« '
tile continued in the same manner until the floor is
finished. When the cement is sufficiently set, which
should be in about two days, the floor should be well
scrubbed with clean water and a broom, and the joints
thoroughly grouted with pure cement (mixed with
water to the consistency of cream). As soon as this
begins to stiffen, it must be carefully rubbed off with
sawdust or fine shavings and the floor left perfectly
clean.

Ceramics. — The foundation and cement mortar for
ceramics are the same as for plain or vitreous floors,
and the guide strips used in the same manner. The
cement mortar is then spread evenly and the tile sheets
laid carefully on it with the paper side up. After the
batch is covered, the tile setter should commence to
press the tile into the mortar, gently at first, firmly
afterwards, using block and hammer, thus leveling
the tile as correctly as possible. The tile should be
beaten down until the mortar is visible in the joints
through the paper ; however, without breaking it. The
paper is then moistened, and after it is well soaked
and can be easily removed, it is pulled off backwards,
starting from a comer. After removing the paper, the
tile should be sprinkled with white sand before fin-
ishing the beating, so that the tiles will not adhere to
the beater, owing to the paste which is used in mount-
ing them. Corrections of the surface are then made
by leveling it with block and hammer. The filling of
the joints and cleaning of the surface is a delicate op-
eration, as the looks of this work depends largely upon
it. The joints are to be filled with clean Portland
cement mixed with water. This mixture is forced into

HOW TO USE THEM 489

the joints with a flat trowel (not with a broom, which
often scrapes out the joints). After the joints are

filled, the surplus cement ia removed from the sur-
face by drawing a wet piece of canton flannel over it.

This piece of cloth must be washed out frequently with
clean water. After the floor is cleaned, it should be

490 CEMENTS AND CONCRETES

allowed to stand for a. day or two, when the whole
floor IB to be rubbed with aharp sand and a board of
Boft lumber. This treatment, which the last traces of
cement, is preferable to the washing off with an acid
solution, as it will not attack the cement in the joints.
In laying the tile sheets on the cement, care should be
taken to have the widths of joints spaced the same as
the tile on the sheets to prevent the floor having a block
appearance.

The Tiles for the Walls or Wainscoting are first laid
out and compared with the plan provided for setting
them. Guide strips are then placed on the wall paral-
lel and abont two feet apart, the bottom one being bd

HOW fo USE them" m

V. ■ m

arranged as to allow the baise to be set after the body*
is in place. (See Fig. 40.) When a cove base is nsed
it may be necessary to set it* first, but in all cases must
be well supported on the concrete. (See ^ig. 41.) The
strips must be placed plumb and even with the intend-
ed finished wall line. The method of setting wall tile
is governed to some extent by the conditions of the
wall on which they are to he set, and must be decided
by the mechanic at the time, which process he will
use, whether buttering or floating, as equally good
work can be done by either, by following the instruc-
tions, as stated below.

Floating Wall Tile, — The mortar is spread between
the guide strips for about five feet at a time and lev-
elled with a screed notched at each end to allow for
the thickness of the tile. (See Fig. 39.) The tiles aro
placed in position and tamped until they are firmly
united to the cement and lieV^Sl with the strips. When
the space between* the strips is completed, which should
be one side of the room, the strips are removed and
the work continued in the same manner until com-
pleted. When the tiles are all set, the joints must be
carefully washed out and neatly filled with thinly
mixed pure Keene's Cement, and all cement remaining
on the tile carefully wiped off.

Buttering Wall TUesji — The cement mortar is spread
on the back of each tile, and the tile placed on the
wall, and tapped gently until firmly united to the wall
and plumb with the guide strips. When the tiles are
all set, the joints must be carefully washed out and
filled with Keene's Cement, and the tiles cleaned as
directed above.

When fiaitures of any kind are to be placed on the

4»2 CEMENTS AND CONCRETES

tile work^ such as plumbing in bathroom, provisioiL
should be made for them by fastening wood strips on
the wall before the rough or first coating of cement
mortar is put on, the strips to be the same thickness
as the rough coating. The tiles can be placed over
the strips by covering them with cement mortar, and
when thoroughly set, holes can be bored in the tiles for
fastening the fixtures without injuring the tiling.

Hearth cmd Facing Tile are set in the same manner
as for floors and walls.

Cleaning. — It is absolutely necessary to remove with
sawdust, and afterwards with a flannel cloth and wa-
ters, all traces of cement which may have been left on
the surface of the tile, as it is hard to remove after it
is set.

After thoroughly cleaning the floor, it should be
covered with sawdust and boards placed on the floor
for several days where there is walking upon it.

A white scum sometimes appears on the surface of
the tile, caused by the cement. This can generally be
removed by washing frequently with plenty of soap
and water. If this does not remove it, then use a weak
solution of 15 parts muriatic acid and 85 parts wa-
ter, which should only be allowed to remain on the
tile for a few minutes, and then thoroughly washed
off.

Cutting of Tile, — "When it is found necessary to cut
tile the following directions are given :

Toolsjh-The chisels used should be made of the best
tool steel, and should always be sharp. They should
be of small size, the edge not being wider than one-
fourth inch. The hammer should be light, weighing
about six ounces, having a slender handle. After the

HOW TO USB THEM 493

exact shape of the tile has been determined, lines
should be drawn on the surface of the tile with a lead
pencil, giving the exact direction of the cut desired.
This line should be i^oUowed with the chisel, which is
held at right anglejS with the surface, the hammer
giving the chisel shiirp, decisive raps. After the line
has been repeatedly traversed with the chisel, a few
sharp blows against the back of the tile opposite the
mark on the face will break it at the place thus
marked.

To cut glazed or enamel tiles, they should be
scratched on the surface with a tool at the place where
it is desired to break them, and then gently tapped
on the back opposite the scratch.

Caution should be used not to allow any one to
walk upon or carry anything heavy over the floor, or
have any pounding abcait wall work for several days,
or until the tiles are firmly set. Unless these precau-
tions are taken it will be impossible to guarantee a
first-clasi^ job. Tile work is frequently condemned
when the fault lies with the rush of other contractors to
finish their work.

Laying Tile on Wood. — ^A new material called
** Monolith/' manufactured by The Wisconsin Mantel
& Tile Co., that enables the workman to lay tiles on
a wooden floor. There are many places where tile
could be used, but on account of the added weight to
the floor by the use of cement, concrete foundation, it
is impracticable to lay in many places,\but by the use
of Monolith, the only weight that is added is the tile
itself and the Moilolith bed* it is laid in. Both ma-
terials are only five-eighths of an inch in thickness
when laid.

CEMENTS AND CONCRETES

HOW TO USE THEM 495

The illustration, Fig. 42, shows the method of laying
the tile. , The paper to which the small pieces of tiles
are glued is seen on top of tiles. The dark part shows
the patent cement, or Monolith.

I show herewith, at Nos.^3 and 44, twelve designs
for decorative borders of various kinds, and in 45
and 46 I show two designs w^ll suited for vestibules,
store entrances or for hearths in fire-places.

Good Concrete. — In determining the proportions of
the aggregates and cement for a certain piece of work,
it is necessary usually to take samples of the broken
stone (or gravel) and sand which are most available
to the site and make measurements of the percentage
of voids in the stone which must be filled by the sand
and the percentage of voids in the sand which must
be filled by the cement. This is done by taking a
cubic foot box and filling it with broken stone in a
thoroughly wet state. The box is then filled with as
much water as is required to completely fill it, in addi-
tion to the stone, which upon being poured oflf gives
the relation between the volume of the voids and the
volume of the stone. The required amount of local
sand thus determined is then measured out and placed
in the box with the stone in a damp state. Water is
then used to determine the percentage of voids left in
the sand, which gives the approximate amount of
cement required, although an excess of cement is al-
most invariably used. Engineers everywhere diflPer
regarding the best proportion to be used, but in gen-
eral the abovQ test, roughly made, will determine it
well enough. The proportions which are most univer-
sally used are as follows: 1 cement, 2 sand, 4 broken
stone; where extremely strong work is desired. Tests

CEMENTS AND CONCKBTES

HOW TO USE THEM

498 CEMENTS AND CONCRETES

show that a 6-incli thicknesa of 1-2-4 concrete properly
made is waterproof up to about 50 pounds to the square
inch. This, concrete is frequently used for facing
dams. 1-3-6 is the proportion generally used for the
interior of dams and large structures. It is entirely
suitable for large foimdations. 1-4-8 is frequently
used for foundation work, and when properly mixed

FiK. 4E.

makes good concrete, although it is about the limit
of what is considered good work, and would not be
suitable for very important structures. 1-5-10 is equal
to any concrete made with natural cement. It is a
well-known fact that the volume of concrete when
mixed with water is somewhat less than the volume of
the aggregate and cement before mixing. The con-
tractors' rule is that the volume of mixed concrete is

HOW TO USE THEM 499

equal to the volume of the stone plus on0>half to one-
third the volume of sand.

There has been much discussion among engineers
and others as to the amount of water that, should be
added to the aggregates and cement for making the
best concrete, and while it is not the purpose of this
paper to enter into this controversy, it might be said
that the modem tendency is toward wet concrete, The
old way was to add just enough water so that when all

FIk. 4S.

the concrete was in the form and tamped, it would
?how moisture on the surface. The tamping is a very
important part of the operation, and the quality of
the work is dependent upon how well this is super-
intended, as unless it is well and thoroughly done the
concrete is liable to be honeycombed and imperfect,
especially near the forms. With the growth of the

600 CEMENTS AND CONCRETES

use of concrete the old method of putting it in the
forms nearly dry and depe^ding on tamping to con-
solidate it has been more or less abandoned, and the
more modern way is to put the concrete in quite wet,
as less tamping is required and much labor and ex-
pense saved. One of the great objections to this
scheme is that if care is not taken the water will tend
to wash the cement from the stone and sand; in other
words, unmix it. However, it may be said that it
is now generally understood that rather wet concrete
properly handled makes better work. The amount of
water to be added to the aggregates and cement va-
ries from 1 water to 3 cement by measurement to 12
per cent of water by weight. Mr. Carey, of .New-
haven, England, says that 23 gallons water per cubic
yard of cement was the best mixture. Quite frequent-
ly salt water is used in mixing concrete in cold weather
to prevent freezing,, and it seems to have no ill effects
on the resulting mixture.

Reinforced Concrete. — ^Up to the last few years the
use of concrete as a building material was chiefly con-
fined to the construction of foundations, piers, reser-
voir dams and similar purposes, in which the stresses
to be met were almost entirely simple pressures. In-
deed, even fifteen years ago, many engineers looked
askance on the use of concrete for arches, considering
it for this purpose much inferior to brick. Much of
the caution shown in extending the use of this valua-
ble material doubtless arose from the frequency with
which concrete masonry exhibited unsightly cracks,
due largely to the material being allowed to get too
dry while hardening. At the same time, careful ex-
amination has shown that cracks of the same char-

HOW TO USE THEM 501

acter are common in masonry of all kinds, but are
unnoticed, because they follow the regular joints of
the structure; whereas, on the smooth uniform sur-
face of the concrete, cracks of much less significance
are immediately visible.

The plan of reinforcing the material with metal, of
which ' several systems have been introduced during
the last four years, has greatly extended the possible
use of concrete; and it appears that in many cases a
reinforced concrete bridge may compete, even in first
cost, with a steel girder; while as regards upkeep, it
has, of course, many advantages. Small bridge cul-
verts of this material were extensively used by Rus-
sian engineers in building the Manchurian Railway.
For openings of some 7-foot span, flat slabs of con-
crete reinforced with rails were used, the thickness
being 8% inches. A similar system was used for spans
up to 21 feet, •the concrete, however, being thickened
at the center as the span increased, the depth at this
point being 2 feet 61^4 inches for the 21-foot span, and
proportionately less for smaller openings. The thick-
ness at the bearings was, however, the same in all
cases, viz., 8^4 inches. The line was thrown over the
spans as little as seven days after completion. The
concrete consisted of one part cement, two sand and
five broken stone. The system in this case had great
advantages, as stone for masonry was unobtainable,
and could, moreover, only be used for arches, which
would have necessitated the use of higher embank-
ments than were required with the ferro-eoncrete, used
as described. Much larger spans have, of course, been
built than those mentioned. One, of 153-foot span,
carrying four main line tracks, has recently been

502 CEMENTS AND CONCRETES

built for the Lake Shore and Michigan Southern Rail-
road, while Mr. Edwin Thacker, M. Am. Soc. Q. B.,
states he considers the system feasible for spans up
to 500 feet, and has actually got out designs for a
span 300 feet, the cost comparing favorably with that
of a steel bridge.

One great drawback to the extension of the system
lies in the difficulty in proportioning structures thus
built in a thoroughly rational manner. In the case of
steel bridges certain simple assumptions as to the
elasticity and strength of the material suffice. These
assumptions are doubtless not absolutely exact, but are
sufficiently near the truth for practical purposes. The
elastic properties of concrete are, however, very dif-
ferent from those of steel; Hooke's law is not even ap-
proximately correct, and, moreover, the material al-
ways takes a permanent set when first loaded. The
true distribution of the stress and strain on a concrete
beam is thus a much more complicated matter than it is
in the case of a steel joist, in which it is permissible,
within working limits of stress, to assume the accuracy
of Hooke's law. The assumption generally made in
the case of ferro-concrete is that plane sections of a
concrete beam remain plane after bending. This pos-
tulate is, of course, that commonly made in propor-
tioning steel work; and in the latter case, stress being
proportional to strain, the usual formula for the work-
ing strength of beams is readily reduced. In the case
of concrete, however, the stress-strain curve is much
more complex. Nevertheless, M. Considere has shown
that by making experiments on concrete in simple ten-
sion and compression, and plotting the corresponding
stress-strain curves, it is possible to deduce from these

HOW TO USE THEM 503

with fair accuracy the load-deflection curve of a ferro-
concrete beam.

Tliis method, though logical, leads, however, to no '
simple formula for the strength; and in applying this
method the working load of any particular concrete
beam would have to be deduced by the tedious proc-
ess of scaling off the stress-strain curves at a num-
ber of points, and combining the results. A further
question arises as to whether this stress-strain curve
should be the initial stress-strain of the concrete, or
that obtained after repeated loadings. Probably the
latter is the best to choose, but in that case it by no
means follows that the metal reinforcement is free
from initial stresses when the load is applied to the
beam ; and if the metal is subject to initial stress, it is
obvious that similar ones must exist in the concrete.
In fact, M. Considere has shown that this is necessarily
the case in any circumstances, since, if the concrete is
allowed to harden under water, it tends to expand,
and this expansion is resisted by the metal reinforce-
ment. If, on the other hand, the hardening takes
place in air the concrete tends to contract; and this
contraction being again resisted by the metal, a series
of fine hair cracks are produced which, visible at low
loads, are readily detected on the tension side of a
heavily loaded ferro-concrete beam.

In view of the uncertainties introduced by the dif-
ferent factors above mentioned, it is really questionable
whether, after all, the theoretically objectionable for-
mula of M. Hennebique is not as good as any other.
The latter all involve a preliminary calculation of the
position of the neutral axis, which varies with the per-
centage of metal used, and with the type of stress-

504 CEMENTS AND CONCEETES

strain curve assumed for the concrete; and also with
the maximum stress at any particular section. Thus,
in a centrally-loaded beam, its position at the ends is
entirely different from what it is at the centre. M.
Hennebique, on the other hand, makes no attempt to
locate this neutral axis, and simply assumes, that one-
half of his beam resists compression, and that the
stress is uniformly distributed over this half. The
moment of this compression about the centre of the
section equates to half the moment due to the load,
and the other half of the moment due to the load he
equates to the moment about the centre of the section
of the tensile stress on the metal reinforcement. The
working strength of concrete in compression, he takes
as 350 pounds per square inch, and neglects entirely its
strength in tension. The working tensile stress on the
steel reinforcement he takes as 14,000 pounds per
square inch. This method is, of cobrse, totally illogi-
cal, yet many thousand cubic yards of ferro-concrete
have been successfully designed on these lines; and a
comparison of the strength of ferro-concrete beams
as calculated by this formula, and by those of a more
rational type, shows very little difference between the
two for a considerable range of metal to concrete. On

the other hand, it must not be forgotten that formulae
which are non-rational in form are always risky when
applied to extreme conditions.

Concrete being as weak in shear as in tension, pro-
vision is also required to take the shearing stresses.
Some American designers have to this end patented
special forms of reinforcement bar, in which each main
tension bar has projecting upward from the ties in-
clined at an angle of 45 degrees. These extend to the

HOW TO USE THEM 505

top of the bar and take the tensile stresses arising
from the shear. The corresponding compressive stress
at right angles to this is carried by the concrete. The
system is doubtless efficient, and on large spans, where
weight must be reduced to a minimum it may have
some advantage; but in work of ordinary proportions
it seems to be little superior to the Hennebique sys-
tem, in which the necessary strengthening is provid-
ed by stirrups of flat iron bent into a U shape. The
main reinforcing bars rest in these stirrups at the
lower ends. The spacing of the stirrups depends upon
the **web stresses" to be taken, which can easily be
calculated by assuming the reinforced beam to be a
latticed girder, the lower chord of which is represented
by the metal reinforcement, the upper one by the centre
of the compression half of the beam, while the stirrups
represent vertical ties, which may be taken /as con-
nected together at top and bottom by inclined imag-
inary struts. The advantage of this simple method of
reinforcing for shear lies in the possibility of using
common rolled sections -for the whole of the rein-
forcement.

M. Hennebique constructs most of his ferro-concrete
work on the monolithic system, girders, piers, columns
and floors being solidly connected together. It is,
therefore, necessary to provide for the reversed bend-
ing moments over the point of support, which is done
by bending up half of the total reinforcement bars,
so that the ends of the span are close to the upper
surface of the beam, and thus in a position to take
the heavy tensile stresses which ensue at these points
when the monolithic system of construction is fol-
lowed. The exact calculation of the reactions and

506 CEMENTS AND CONCRETES

bending moments here is impracticable, if not actually
impossible; and those engineers who attach much im-
portance to having all structures statically determinate
will doubtless object to the plan, but experience shows
that the advantages gained are very considerable. The
structure then resists as a unit, and in particular its
rigidity is marvelous.

Some comparative tests on this point, made by the
Railway Company, showed that with a ferro-concrete
floor subjected to blows four times as heavy as were
applied to an equivalent' floor constructed of brick
arches on steel joists, the deflection was only one-
seventh as great.

The extreme rigidity attainable with the monolithic
system of construction was also very evident in the
case of the large Hennebique bridge at Purfleet. Since
a structure fails by strain rather than by stress, the
small deformation noted with ferro-concrete are evi-
dent that as an average the material is relatively ht-
tle tried by the loads carried. It must, however, be
admitted that this low average strain is quite com-
patible with extremely severe strain at particular
points ; but it is, of course, the business of the designer,
by suitably disposing his material to avoid these pos-
sible local abnormalities.

Occasionally, doubts have been expressed as to
whether the metallic reinforcement may not suffer from
cArrosion as time goes on. This would be extremely
dangerous if it occurred, since the metal being out of
sight, its loss of strength might remain undetected un-
til, some day, the structure might fall under its ordi-
nary working load. Fortunately, much evidence is
available to the effect that steel or iron thoroughly

HOW TO USE THEM 507

Imbedded in concrete is permanently protected from
rust. Americans, indeed, are so positive on this point
that they have recently constructed a number of reser-
voir dams in ferro-concrete. In some cases these have
been arched, but in others they have been straight.
The cross-section in the latter case is generally a hollow
triangle, the sides of which are connected together by
diaphragm walls from point to point. The dam is also
anchored to its site, though generally the weight pro-
vided is sufficient to make the structure safe against
overturning, quite apart from the help received from
the anchor-bars.

Progress in the use of reinforced concrete has been
somewhat slow in England. The railway engineers, in
view of their enormous responsibilities, have not un-
naturally hesitated to adopt a material in which it was
impossible to calculate the strength with accuracy, and
of which experience as to its reliability was very re-
cent. In the larger cities, moreover, its use has, quite
apart from this, been restricted by the inelastic na-
ture of the building regulations, which have been
reached upon the assumption that finality had been
reached in the matter of building construction. Hence,
permission to erect warehouses and factories in ferro-
concrete has always been difficult — and often impossi-
ble— to obtain, though experience has shown that the
new material is most excellent as a fire-resister. At
the great Baltimore fire it was found that the concrete
exposed to the flames was seldom damaged to a greater
depth than one-half inch, though projecting comers
suffered somewhat more, being rounded off by the
flames to a radius of about two inches, pointing to the
advisability of constructing the concrete with well*

508 CEMENTS AND CONCRETES

rounded comers in the first instance. The only rea-
sonable grounds of objection to any proposed system
of building construction are its dangers from a struc-
tural sanitary or fire-risk point of view. As a result
of much investigation and experiment, the following
conclusions were arrived at for the guidance of the
designer and constructor of reinforced concrete:

1. What drawings and details should be prepared
before work is commenced.

2. The nature of the materials which may be em-
ployed and the standards to which these should com-
ply, i. e.,

(a) the metal in reinforcement,

(b) the matrix,

(d) the gravel, stone, clinker or other aggregate,

(e) water.

3. What are the proportions for concrete to be used
in different cases.

4. How the ingredients for concrete are to be mixed
and deposited on the work.

5. The distances to be allowed between the reinfor-
cing bars and what covering of concrete is necessary.

6. What precautions are necessary in the design and
erection of centring and false work, and how long the
whole or portion of centring and false work should re-
main in position.

7. The rules which should be used in determining
the dimensions of the several parts necessary for secur-
ity, and what safe stresses should be allowed.

8. The supervision necessary and the special mattera
to which it should be directed.

HOW TO USE THEM 509

9. The fire-resisting properties of reinforced con-
crete.

10. Its adaptability for structures where resistance
to liquid pressure is essential, and what special precau-
tions may be advisable under these conditions.

11. What are the necessary conditions for its perma-
nence; resistance to rusting of metal, disintegration of
concrete or effects of vibration.

12. The testing of the materials employed and of the
finished structures.

13. What provisions are desirable in Building Laws
or Government regulations relating to buildings and
other structures so far as these affect the use of rein-
forced concrete.

REINFORCED CONCRETE.

The engineer who is designing a steel structure speei-
iies that tests shall be made at the shops which will give
a clear indication of the character of the materials used.
These tests refer to the ultimate strength, elastic limit,
ultimate elongation and reduction of area. He also in-
spects the construction of his structure, and bad work-
manship is getting more and more rare. If poor work is
sometimes done it can be discovered by careful inspec-
tion, and when the structure is tested on completion noth-
ing unexpected will take place, if its type and design are
based on practical experience. Thus the deflections
which steel structures show under their test loads are
found to be almost identical with those computed for
them and their determination is, therefore, not of great
value.

The measuring and observation of the local deforma-
tions, on the contrary, furnish valuable information on
the distribution of stresses, and enable the engineer to
appreciate the advantages and disadvantages of the vari-
ous types of construction ; but it is very seldom that they
disclose faulty construction or bad material. It can thus
be said that for steel or iron structures the preliminary
tests of the materials used and the inspection of construc-
tion and erection furnish all the necessary assurances.
Quite different is the case with concrete-steel structures,
because laboratory tests tell us only of the quality of the
materials employed, and the most active inspection will
not be able to prevent positively poor workmanship and

510

REINFORCED CONCRETE 511

faulty construction which can destroy the strength of
structures made of the best materials.

In fact, the proportions of the concrete may, in spite
of careful watching, not be in all parts in accordance
with the specifications; the quantity of water used in
mixing must, in order to produce identical results, vary
within a wide range, according to the condition of mois-
ture in the materials and the atmosphere, and it is quite
sure that it wiU be sometimes badly proportioned. If too
much water be added the strength of the concrete, and
especially its coefficient of elasticity, will be decreased to
a degree which may be considerable; if too little water
be added the adhesion of the concrete to the reinforcing
metal will not be sufficient. The thoroughness of the
tamping has a still greater influence on the strength of
the work. To the faults of execution, faults of design
may be added. The latter must especially be guarded
against in a new type of construction, the theory of
which is not yet fully established.

Whatever the results of the tests of the materials may
be, very little information on the strength of a concrete-
steel structure can be obtained without direct tests of the
structure itself. But observed deformations will furnish
really useful indications only when compared to tiie nor-
mal deformations which, according to the computations,
should have been caused in accordance with the quality
and disposition of the materials. Hitherto no method
has been established to enable the engineer to compute
tbiese normal deformations. However, at one time it was
assumed that reinforced concrete, whatever its deforma-
tion, preserves the coefficient of elasticity as determined
in ordinary tension tests, and at another that the resist-
ance of the concrete in tension can be neglected in rein-
forced members. Sometimes it has also been assumed

512 . CEMEi^TS AND CONCRETES

that the resistance of concrete in tension can be neglected
only when its deformations exceed the elongation which
causes rupture in common tension tests. None of these
assumptions has given results agreeing with the actual
behavior of reinforced concrete. We may conclude that
in reinforced concrete construction certainly some par-
ticular phenomena occur, a knowledge of which is neces-
sary to predict their resistance and deformations.

Concrete in compression is generally not reinforced
and it cannot be expected that -the phenomena mentioned
in the preceding section will be found to be caused by it;
It suffices to recall the well-known law of deformation of
concrete in compression and to make it more precise by
naming the ratio of an infinitely small variation of com-
pression to the variation of length caused by it, the "in-
stantaneous coefficient of elasticity."

When the compression increases, but remains within
an amount which, in general, is nearly a third of the
ultimate strength, the instantaneous coefficient of elas-
ticity decreases, but in a very small degree. When the
stress increases still more the change in the elasticity
gradually increases; it is appreciable for a compressive
stress near one-half the value of the ultimate, and it then
increases so rapidly before failure that the instantaneous
coefficient may fall below one-twentieth of its value un-
der a light stress. This aspect of the deformation is
similar to the one generally observed on all materials.
The simple law which determines the deformation of
concrete in compression thus cannot furnish the explana-
tion of observed irregularities, and it must be looked for
in the phenomena which are produced in tension.

It appears to be evident that the test loads should not
be heavier than the amount required to insure the safety
of the structure. Even smaller loads could, no doubt, be

EEINFORCED CONCRETE 513

employed if a comparison of the computed deformations
and those actually observed is made, as has been proposed
in this chapter, so as to obtain by means of moderate test
loads the coefficient of elasticity, the elastic limit and the
tensile resistance of the concrete of the tested beams. It
is, besides, known that the compressive resistance is al-
most proportional to the tensile resistance and it is con-
sequently evident that a test with a moderate load will
suffice to furnish information on all the properties of the
concrete employed.

To the preliminary tests of the materials to be em-
ployed the direct tests of reinforced concrete structures
must be added to obtain sufficient assurance of safety.

The tests will not show their full usefulness unless
the deformations which should normally be expected be
first computed and then conjpared to the observed defor-
mations. '

The computation of the deformations to be expected
must be based on the knowledge of the laws of defor-
mation of concrete reinforced by metal, and it appears
that above the elastic limit, these laws are different from
the laws which determine the deformations of unrein-
forced concrete.

The deformations of members in flexure appear to be
influenced by the shearing stresses, by. the character of
the surroundings in which the concrete has set and was
kept and by the action of any transverse reinforcing
members.

. The investigation and study of these phenomena is
still more important because the strength of a member
is intimately connected with its deformations.

It is easier to compute the elongations and shorten-
ings which should be expected to take place, under nor-
mal conditions, in a given section than the deflection of

514 CEMENTS AND CONCRETES

a beam, which is the resultant of the deformations of all
of its sections. The measuring of the local deformations
deserves, therefore, to be recommended and at least to
take its place side by side with the measuring of deflec-
tions.

Concretes placed under water and gradually hardened
there show a tendency to swell in all directions, and the
more so the richer their proportions of cement. This
swelling varies from 0.1 to 0.2 per cent, for pure cement
mortar and from 0.02 to 0.05 per cent, for concrete poor
in cement.

When the swelling cannot take place freely, compres-*
sive stresses are developed in the masonry, which may
reach much higher values than the stresses caused
by the shrinking in the air. Experiments were made
which were intended to establish the law of relation be-
tween the deformations, prevented from exceeding cer-
tain limits by external means or metal reinforcing, and
the stresses developed at the same time. An idea of the
importance of these stresses will be formed by the fact
that, in a rectangular prism 2.36 by 0.98 inch, made of
neat cement and reinforced in its axis by an iron rod 0.4
inch diameter, there have been developed, after ten
months in water, internal and opposing stresses of about
2,200 pounds, equivalent to a compressive stress of about
90 pounds per square inch in the concrete and a tensile
stress of about 17,500 pounds per square inch in the
iron. The tension in the iron was measured directly, and
computed as accurately as possible by multiplying the
coefficient of elasticity by the shortening of the rod
caused at the instant when the surrounding cement which
prevented it from taking its natural length was carefully
removed.

The internal stresses caused by the prevention of tlie

REINFORCED CONCRETE 516

swelling of mortar or concrete members by the reinforc-
ing rods are, in general, favorable to their resistance, be-
cause these stresses increase the compressive stresses and
decrease the tensile stresses of the materials which can
resist the former ten times better than the latter. They
have especially the effect of consolidating building joints
and all sections of small resistance to tension by prevent-
ing cracks in them. Obvious advantages result therefrom
for the resistance of masonry kept under water and the
durability of the concrete and its reinforcing metal.

Differences in the swelling of layers of different age
must, however, be guarded against as they cause parallel
stresses in the joints, which seem to be injurious to the
adhesion. But, contrary to what takes place in the case
of shrinking, it is here the oldest masonry in which ten-
sile stresses are caused^ and its resistance being superior
to that of the superimposed masonry the possibly dan-
gerous effect is decreased. However, the author has no
experimental proof as to the dangers due to the different
swelling of parts of masonry. In general an exaggerated
account of the internal stresses should be avoided because
their effects combine according to little-known laws with
the stresses caused by the external forces, and it may be
possible that in some places their actions should be added
together.

It seems, therefore, to be proper not to raise the pro-
portions of cement in concrete above the limits which
insure sufficient impermeability and long life to the sub-
merged concrete. It appears to be of advantage not to
exceed 1,300 to 1,500 pounds of cement to the cubic yard
of concrete, which proportion gives the greatest resis-
tance, except for work exposed to the waves, where rapid-
ity of setting is a necessary condition for successful
work. From all the above considerations it follows that

516 CEMENTS AND CONCRETES

reinforced concrete masonry will give still better results
for hydraulic work than for structures expose^ to the
air, and the success of these has been proved by experi-
ence.

It should be stated that, in the computations of the
resistances of concrete masonry structures in which the
free change of volume is in any way prevented, these
changes should be considered. On this basis the author
recently showed that in the floor of a dock only harmless
stresses could be produced in spite of the fact that this
floor was of a thickness which would have caused exces-
sive stresses if the increase in volume had not strongly
compressed the floor against the foundations of the side
walls.

It is well known that all the materials employed in
masonry show an increase in volume when they absorb
water and a decrease when their moisture is reduced.
The author has found these changes in volume to be
much greater than is given by Busing and Schumann in
their work on cement. A prism of neat cement, not rein-
forced, which was kept in dry air during two years elon-
gated 0.024 per cent, of its length after three weeks of.
immersion in water. A prism of mortar, not reinforced,
containing 730 pounds of cement to the cubic yard of
sand, which was kept fifteen months in water, shortened
0.05 per cent, after being two months in dry air. From
the observations made it appears that contrary to what
has taken place in the changes of volimie due to the
gradual hardening of the cement, the variations in vol-
iime produced by changes in the state of moisture on
iiardened mortar do not increase with the higher pro-
portions of cement. The contrary rather takes place.

There is still another radical difference between the
effects which the two causes of change in volume have

REINFORCED CONCRETE 517

on reinforced concrete members. During the hardening
the mortar possesses at the beginning a very high degree
of plasticity, which gradually decreases. This results in
causing the mortar, which has gradually hardened, to
yield to a large extent to the stresses which the reinforc-
ing rods produce in it. Thus reinforced members which
have set in the open air remain of a greater length than
that which they would have taken freely without re-
straint from the reinforcing. The crystallizations which
take place during the setting are between the artificially
separated molecules, and a decrease in density, elasticity,
and resistance is the result.

The opposite should be caused in reinforced members
which have hardened in water, but the author has not had
the occasion to verify whether an improvement in the
quality of the concrete actually takes place. The effects
of the variations in the hygrometric condition on com-
pletely hardened mortars are very different from those
resulting from gradual hardening. There is a struggle
between the two associated materials, the coefficients of
elasticity of which have arrived at their final values, and
the difference between the length which each material
tries to assume and the one it is compelled to take by
the combination is inversely proportional to its coefficient
of elasticity.

From these considerations it follows that account
should be taken of th^ fact that the difference in the
variations of length which take place in a mortar accord-
ing to whether it is reinforced or not will be considerably
greater during the beginning of the hardening than dur-
ing the following hygrometric changes. Experience has
confirmed this fact. It also follows that the variations
in volume which the hygrometric changes tend to produce
in hardened mortars are smaller than those produced

518 CEMENTS AND CONCEETES

during gradual hardening, since internal stresses, and
especially tensile stresses in the reinforcing rods, may be
caused, which attain 5,500 to 8,500 pounds per square
inch. Contrary to what takes place during the slow
hardening of mortar, the hygrometric variations appear
to be the more dangerous the less rich in cement the mor-
tar is, because its resistance is smaller while the internal
stresses are, at least, as great.

It should be added that these disadvantages are practi-
c;^,lly of no account for masonry always exposed to the air
because the changes in the proportions of moisture in the
air have a very small effect. The question is only of im-
portance for members made in the open air which begin
to harden before being put in water where they finally
remain submerged, as in the case of piles, caissons, etc.
By keeping them moistened until put in place, not only
will the cracks which are often caused, as has been shown
by experience, be prevented, but also the changes in the
internal stresses, which cannot be of any advantage. It
would be both interesting and useful to determine experi-
mentally the results to be obtained by keeping reinforced
concrete members, to be permanently exposed to the air,
as moist as possible by abundant and repeated sprinkling
for several weeks. It is obvious that the final shrinking,
as well as the disadvantages resulting therefrom, would
be decreased.

In concluding attention should be called to a fact
worthy of research. Keinforced concrete members pre-
viously subjected to test loads have shown very little ef-
fect due to changes of the moisture in them. This will
seem probable when it is remembered that the test load
reduces the coefficient of elasticity of the concrete very
considerably.

The first idea which presented itself to engineers to in-

REINFORCED CONCRETE 519

crease the resistance of concrete in compression was to
reinforce it, similarly to tension pieces, by rods laid
longitudinally in the direction of the stress. For purposes
of construction, to keep the rods better in place, the rein-
forcing rods were tied together by a network or a belt of
smaller rods. Some engineers understood that these belts
perform another important role, that they protect the
longitudinal rods from premature flexure and retard the
swelling of the concrete and, hence, its ultimate failure.

It will be seen below that by hooping or completely sur-
rounding the concrete by steel rods a considerably higher
resistance can be obtained, and it is evident that between
this method, supplemented by the addition of longitudi-
nal rods, on one side, and the method of reinforcing by
longitudinal main rods tied together by belts of lighter
material on the other side, there is an intermediate con-
tinuous series of methods of reinforcing. The conclu-
sions reached by this study will enable us to foresee the
effects of these complex combinations, but before making
the synthesis the influence of each element should be in-
vestigated separately. Concrete reinforced by longitu-
dinal rods tied together by netting or belts of dimensions
too small or spaced too far apart to exert noticeable
influence on the resistance of concrete will, therefore, be
treated first.

It was admitted, up to the present time, that the dif-
ferent varieties of stone, mortars, and concrete, when
under compression, always fail by shearing along planes
which are inclined to the direction of the stress. The
recent experiments made in (Jermany by Foeppel and
repeated by Mesnager at the laboratory of TEcole des
Ponts et Chaussees have proved that this mode of failure
is due to the friction exerted on the lower planes of the
test specimens by the plates transmitting the pressure.

520 CEMENTS AND CONCEETES

And it has further been proved that by sufficiently re-
ducing this friction by the introduction of a greased sur-
face, the failure will take place along surfaces which will
be parallel to the direction of the pressure.

It is not clear how longitudinal reinforcing bars, which
are parallel to the lines of rupture, could prevent the
separation of the molecules and increase the resistance of
the concrete, and it seems that the only effect of longi-
tudinal reinforcing in compression members consists in
adding the resistance of the steel to that of the concrete
without strengthening the latter. Experience has shown
that such is the case. The effects of the reinforcing bars
are, however, complicated, for the reasons which follow.

As has been shown, the tendency to shrink which con-
crete shows when hardening in air causes in reinforced
concrete internal stresses of gr^at intensity; tension in
the concrete and compression in the metal. Experiments
made in 1902 at the laboratory of TEcole des Fonts et
Chaussees, according to the program laid out by the
French Commission on Concrete-Steel, have determined
the effect due to the shrinking of large concrete-steel
specimens of the most commonly employed mixture, 420
pounds of Portland cement to the cubic yard of sand and
1-inch gravel in the proportion of 1 :2. Measurement of
the variations in length of the reinforcing bars has shown
that after three months the shrinkiog of the concrete had
compressed the metal, 6,540 pounds per square inch, in
prisms 6.5 feet long of a section about 4x4 inches and
reinforced near the edges by 4 iron wires 14 i^ch in
diameter. The compressive stress in the metal has reached
10,800 to 14,200 pounds per square inch in beams 13.1
feet long having a cross-section about 8x16 inches and re-
inforced near one of the smaller sides by 4 metal rods of
yg-inch diameter placed 1.3 inches from the face. The

EEINFOECED CONCEETE 521

latter specimens were prepared to be tested for bending.

It is superfluous to point out the importance of the
above statement as to the magnitude of the interior
stresses in members of the usual mixtures and of dimen-
sions similar to those met in practice. Neglecting this
kind of stresses, some engineers have made grave mistakes
in the interpretation of bending experiments and have
established incorrect formulas and rules, especially on
the subject of stresses in compression members. They
have assumed that if a certain specimen has undergone a
shortening, i, its reinforcing bars, which had a coefficient
of elasticity E, were compressed to a stress E i, neglecting
the addition which has to be made to the latter stress for
the shrinking of the concrete, if it has hardened in air,
and which usually exceeds it in amount. The above con-
siderations are sufficient to compute the stresses in com-
pression members as long as the elastic limits have not
been surpassed, neither in the concrete nor in the metal ;
but this is only one side of the question.

Without entering into a discussion of the unit stresses
which may be allowed for the various elements of rein-
forced concrete structures, it is evident that the basis of
any computation must be the knowledge of the stresses
which are induced in these elements at the instant at
which, for the first time, there appears any danger for
the one or the other of them. It is, therefore, important
to know the stress caused by the reinforcing steel in a
member in compression at the instant where it begins to
fail by the crushing of the concrete, which takes place a
long time before that of the steel.

A concrete of common quality can stand without
crushing a reduction in length of 0.07 to 0.10 per cent,
and sometimes more. Such a compression will cause a
stress in the metal of 20,000 to 29,000 pounds per square

522 CEMENTS AND CONCRETES

inch, if the coeflficient of elasticity be 29,000,000' pounds.
This stress added to the previous stress of 7,000 to 14,000
pounds, gives a total of 27,000 to 43,000 pounds per
square inch of the metal, which is equal and even su-
perior to the elastic limit of the iron and mild steel which
is usually employed. Therefore, before the crushing of
the concrete, the reinforcing bars are almost always
stressed up to their elastic limit, unless the elastic limit
of the bars be exceptionally high or the concrete excep-
tionally poor.

This stress cannot be appreciably surpassed because a
very great decrease takes place in the value of the coeffi-
cient of elasticity of the metal as soon as the elastic limit
has been exceeded, and the stresses increase, therefore,
with an extreme slowness which is limited by the small
deformations whixjh the concrete can still undergo with-
out crushing.

Whatever the mode of rupture of concrete in compres-
sion, the crushing of the same must be retarded by the
use of reinforcing rods put in planes perpendicular to
the direction of the external pressure and suflSciently
near to each other. The tendency to slide along oblique
planes is, indeed, resisted by reinforcing bars which cut
these planes, whether parallel or perpendicular to the
direction of the pressure. Rupturing along surfaces
parallel to the pressure is directly opposed by transverse
reinforcing.

The idea of using transverse reinforcing is not new,
and, while it may be still older, it is sufficient to mention
that it was experimented upon in 1892 by Koenen and
Wayss. Since then Harel de la Noe has theoretically
explained the advantages of transverse reinforcing and
has made and inspired some very interesting applica-
tions. The transverse reinforcing may consist of a series

REINFORCED CONCRETE 523

of rods placed on diameters, all passing through the cen-
ter of the section, or of a net with rectangular openings,
or of circumferential rods which constitute hoops em-
bedded in the concrete to a depth required to protect the
metal from the action of atmospheric influences.

The author has not made any experiments on the first
system which concentrates the metal around the center
where it is the least useful. He has limited his prelimi-
nary experiments to reinforcing consisting either of cir-
cumferential hoops or of netting wires at right angles
and parallel to the sides of the section. For equal weights
of metal the resistance to crushing was appreciably more
than twice as great for the circumferential reinforcing as
for the wire netting.

Without entering into a theoretical discussion, the
above result can* be explained by a simple observation.
If the external layers of a prism reinforced by rectangu-
lar wire nets are considered the lateral thrust outwards
to which they are subjected by the pressure at their base
will in nowise be resisted by the rods parallel to these
layers or faces, and nothing prevents them from sep-
arating from the central mass simultaneously with the
concrete in which they are embedded. Of course, the
bars at right angles to the faces considered offer a re-
sistance to the outward thrust, but only to such extent
as they adhere to the concrete. This adhesion is propor-
tional to the area of contact, and is zero at the ends and
only increases in intensity as the distance along the bars
increases from the faces, but these faces are just the lay-
ers most exposed to crushing. To remedy this fault the
author has first employed iron rods so connected as to
support each other, and then nets of wires interwoven in
a manner which promised the best results. After all
these arrangements the crushing beginning at the face

524 CEMENTS AND CONCEETES

has gradually spread toward the center and it became ap-
parent why, for equal weights of steel, not more than one-
half of the resistance shown by the hooped concrete was
obtained. It was as a result of the above experiments
that all further investigations were directed to concrete
reinforced by hoop-like rods.

The inner forces acting in solid bodies are often placed
in two different classes. The name, cohesion, is generally
given to the inter-molecular action, and it is known that
it varies in proportion to the distances of the molecules
from each other up to a certain point which is called the
** elastic limit." As a premise nothing is supposed to be
known of the effects produced by cohesion above the elas-
tic limit ; but at the same time it is generally admitted
that friction exerts an action in the interior of bodies
similar to that exerted on their surface.

However, this division, which may appear arbitrary, fe
not generally accepted and the deductions made from it
may be disputed. We will leave the purely theoretical
considerations and will attempt to attain the practical
aim of the engineer, which is to formulate rules which
will enable him to predict the mechanical properties of
the materials. The following method was adopted for
investigation :

A certain number of prisms of concrete of different
qualities and surrounded by hoops of various arrange-
ments and sizes was prepared. Some had, also, longi-
tudinal reinforcing rods. These prisms were submitted
to increasing pressures and the shortenings produced
were measured together with the loads. By a well-
known formula for the thrust of a granular mass, the
resistance was computed which would be offered by a
prism of the same dimensions, reinforced in the same
way if sand without cohesion were put in place of the

REINFOECED CONCRETE 525

concrete. The same co-efficient of friction was assumed
and the same percentage of swelling of cross-section to
decrease of length. This was computed for each observed
deformation. It is evident that the excess of the ob-
served resistance of a concrete prism over the similar
resistance of sand corresponding to the same deforma-
tion can only be attributed to the direct or indirect effects
of the cohesion of the concrete. Without entering into
a discussion on the character of this difference in re-
sistance and without attributing to the name a precise
scientific meaning, we shall call this excess the ''specific
resistance of the concrete.''

From this definition it follows that to determine the
total compressive resistance of a hooped concrete prism
it will suffice to add the specific resistance of the concrete
to the resistance of a prism of sand having the same
hooping and the isame coefficients of friction and trans-
verse swelling. The latter resistance can be computed.
To make use of this arbitrary distinction it must be pos-
sible to predict the specific resistance of the concrete in
hooped members from the resistance of concrete of the
same quality not hooped. It will be seen that this can be
done as far as is required.

CONCRETES, CEMENTS, MOETARS, PLASTERS

AND STUCCO

QUESTIONS

1. Give a description of the lime principally used for

internal plastering.

2. Give a description of those which are known aa

** Hydraulic Limes'' and the properties they pos-
sess.

3. Give a description of *' artificial hydraulic limes"

and how they may be mixed.

4. Give a description of the process termed ''slak*

ing" and how to effect it thoroughly, and what
lime will slake quicker than others.

■I

QUESTIONS
5. Give a description of how the lime should be

''run/'

6. Give a description of the two important purposes

for which sand is used in the composition of
plaster.

7. Give a description of the composition and proper-

ties of sand for the several purposes for which it
is best adapted.

8. Give the general rule for the proportion of sand

to lime in the composition of plaster.

9. Give a description of where sand is obtained, and

what kind should be avoided, and the reason for
doing so.

10. Give a description of river sand, its properties, and

for what class of work it is used.

11. Give a description of the purpose of hair in the

composition of plaster, the kind generally used,
its characteristic qualities, and proper method in
its manipulation.

12. Give a description for what purposes Portland Ce-

ment with a large proportion of sand, may be
utilized.

13. Give the designations of the ''setting cements"

that are generally the stronger.

14. Give a description of ** Roman Cement,'' its

disadvantages, and its utility for certain pur-
poses.

15. Give the names of other ''natural cements" very

similar to Roman, and that are also useful where
quick setting is required.

16. Give a description of "Parian Cement," for what

kind of work it is best adapted, and the qualities
it possesses.

CEMENTS AND CONCRETES

17. Give a description of **Keene's Cement/' its dom-

inant property over other kinds, and the utility
to which it may be adapted.

18. Give a description of ** Martin's Cement," the

properties it possesses, and for what purpose is
it principally utilized.

19. Give a description of some of the advantages de-

rived from the use of ''Robinson's Cement."

20. Give a description of ''Adamant," and the proper-

ties it possesses.

21. Give a description of "Selenitic Cement," the prop-

erties it possesses, and its utility.

22. Give a description of "Plaster of Paris," its pro-

portion to ordinary lime putty, and its utility
for various purposes.

23. For what purpose are pine, cedar and metal laths

used?

24. Describe the defects that are to be avoided in laths,

and the reason for their rejection.

25. Give the description of "Riven Laths."

26. Give the three sizes in which laths may be obtained,

and the terms applicable to each respectively.

27. Give a description where the "thicker" and "thin-

ner" laths should be used respectively, and the
reasons why so described.

28. Give a description of how laths are usually spaced.

29. Give a description of what is meant by "A Bunch

of Laths," what it contains, the number of super-
ficial yards it will cover, and the number of nails
required when nailed to joists 1 ft. from center
to center.

30. Give a description of the lengths of laths.

QUESTIONS

31. Give a description of how laths are best nailed so

as to break joint entirely.

32. Give a description of how **Lap Joints" at the

end of laths should be treated.

33. Give a description of how joists that are thicker

than 2 inches should be treated.

34. Give a description of the qualities possessed by

** Metal Lathing" and why it is now extensively
used.

35. Give a description of the various kinds of ** lath-

ing nails" and the different purposes for which
they are used.

36. Give a description of the purposes for which Port-

land cement is best adapted, and the qualities it
possesses.

37. Give a description of the composition of the cement

for ''rendering." ^

38. Give a description of the plastering operations of

** External Facades in Portland Cement."

39. Give a description of how the key for external plas-

tering on brick work may be obtained.

40. Should fat lime be mixed with Portland cement t

41. Give a description of the term ** Stucco" and to

what it is applied.

42. Give a description of ''common stucco," its com-

position and how employed.

43. Give a description of "rough stucco," how it is
^ utilized and manipulated.

44. Give a description of "Bastard Stucco and Trow-

elled Stucco," their composition and purposes for
which they are adapted and how manipulated.

45. Give a description of the term "Sgraffito," and

how patterns may be obtained.

CEMENTS AND CONCEETES

46. Give a description of **the design for the "Sgraf-

fito."

47. Give a description of ''rough cast," its composi-

tion, qualities, and method of manipulation.

48. Give a description of **Depeter," the qualities it

possesses, and the several methods of manipulat-
ing it.

49. Give a description of **Lime plastering," its corn-

position, and manner of its application.

50. Give a description of what is meant hy ''one-coat

work" in plaster work operations.

51. Give a description of "two-coat work'* in plaster

work operations.

52. Give a description of "three-coat work" in plaster

work operations.

53. Give a description of the several processes in plas-

tering ordinary three-coat work.

54. Give a description of "Gauged stuff," its composi-

tion, the purposes for which it is used, and man-
ner of its manipulation.

55. Give a description of "the white cements," their

composition, and manner of adaptation.

56. Give a description of some of the causes that pro-

duce the cracks often observable in plaster work,

57. Give a description of how the joist lines on ceiluigs

are caused, and how they may be prevented.

58. Give a description of the process termed "Pug-

ging," and the purposes for which it is intended.

59. Give a description of "Mineral Wool," its com-

parison'with ordinary pugging, its qualities, and
purposes for which it is adapted.

QUESTIONS

60. Give a description of **Lime Whiting or White

wash," its composition, and purposes for which
it is adapted.

61. Give a description of '* fibrous plaster," its com-

position, and the adaptability of the qualities it
possesses.

62. Give a description of the methods in which orna-

mental plaster ceilings may be treated.

63. Give details separately of the 17 rules that are

embraced under ''Specification Clauses" and rela-
tive to materials and workmanship.

64. Give a description of the preparation of Bill of

Quantities.

65. Give a description of ** Laths Generally," the meth-

od of manipulating them, and the different kinds
of nails used.

66. Give a description of the *'Hoes and Drags" iksed

by the plasterer, and the purposes for which they
are utilized.

67. Give a description of the article known as **The

Hawk," and for what purpose it is used.

68. Give a description of the ** Mortar Board," and for

what purpose it is used.

69. Give a description of the different kinds of

''Trowels," and the respective purposes for which
they are utilized.

70. Give a description of the different kinds of

"Floats," and the respective purposes for which
they are adapted.

71. Give a description of "Moulds," how they are

made and for what purposes they are utilized.

72. Give a description of "Center-Moulds/' and the

principle upon which they are made.

CEMENTS AND CONCRETES

73. Give a description of the tool termed ' ' The Point-

er/' and for what it is chiefly used.

74. Give a description of the process termed lime burn-

ing or calcination.

/5. Give a description of what is meant by the term
** Mortar/' its composition and the processes
which are adopted in its manipulation.

/6. Give a description of what is meant by **the ad-
hesive strength" of mortar.

77. Give a description of the causes that operate in

the ** hardening of mortar."

78. Give a description of some of the qualities pertain-

ing to ** Mastic," and for what purpose is it some-
times used?

79. Give a description of the various processes in the

manipulation of ''Mastic."

80. Give a description of the composition of ** Scotch

Mastic. ' '

81. Give a description of the composition of ** Common

Mastic. ' '

82. Give a description of the process termed ''Scratch-

ing," the tool employed and method of manipula-
tion.

83. Give a description of the process termed "Render-

ing," and how it should be properly done.

84. Give a description of how to manipulate the wall

and ceiling "screeds."

85. Give a description of the term "Flanking" and

the method of performing the operation.

86. Give a description of the process in "Scouring

coarse stuflf."

87. Give a description of the process termed "keying"

in plaster work, and method of manipulation.

QUESTIONS

88: Give a description of what is termed *'* Setting
Stuff," and method of manipulating it.

S9. Give a deseriptixin of the term *' Scouring setting
stuff," and method of manipulation.

90. Give a description of the processes known as

** Trowelling and brushing setting stuff. '^

91. Give some general remarks on ** Setting," and the

best method of making joints and setting stuff,
where it is inconvenient to lay and finish the
whole surface in one operation.

92. Give a description of ** Common Setting" for walls

and ceilings, and methods of manipulation.

93. Give a description of the process termed ** Skim-

ming," and method of manipulation.

94. Give a\description of the process termed ** Colored

Setting," its composition, and method of manipu-
lation.

95. Give a detailed description of how to set out and

construct Corinthian Entablature^ including the
cornice, enrichments, coffers, modillion blocks,
and paterae.

96. Give a description of the method of setting out and

constructing a mould intended for forming the
moulding and miters in one operation.

97. Give a description of how the fixing of enrichments

should be executed, and what has to be avoided
during the operation.

98. Give a description of how the mitering of enrich-

ments is to be performed, and what should be
done in fixing medallion blocks, dentils or paterae.

99. Give the description of a column trammel, and the

method of its manipulation.

CEMENTS AND CONCRETES

100. Give a description of the method of constructing

plain diminished columns.

101. Give a description of how to set out the flutes of

a diminished column.

102. Give a description of how to construct diminished

fluted columns.

103. Give a description of diminished fluted pilasters,

and the method that should be adopted in their
.construction.

104. Give a description of diminished mouldings, and

the methods that are adopted in their construc-
tion.

105. Give a description of the ** diminished rule meth-

od" for running double diminished mouldings.

106. Give a description of the "top rule method" of

running double diminished mouldings.

107. Give a description of the method of constructing

the plaster work of cupolas.

108. Give a description of templates for running ellip-

tical mouldings, and methods of their manipula-
tion.

109. Give a description of the methods adopted in the

formation of coved ceilings.

110. Give a description of the methods adopted in the

formation of circle mouldings on circular sur-
faces.

111. Give a description of the formation of niches or

recesses in walls, and for what purposes they are
adapted.

112. Give a description of the process termed ''Fresco,*'

and how the plaster is to be prepared for the
ception of the decorative operations.

QUESTIONS

113. Give a description of ** Indian Fresco and Marble

Plaster," the process of its composition and the
purposes for which it is adapted.

114. Give a description of *'Scagliola," its excellent

qualities, durability, and the purposes for which
it is adapted.

115. Give a description of the colors and quantities that

are used for the following marbles, respectively,
namely, Penzance marble, Egyptian Green, Dark
Porphyry and Green Genoa.

116. Give a description of the process of the polishing

of ''Scagliola."

117. Give a description of the process in the manufac-

ture of **Marezzo/' and the purposes for which it
is adapted.

118. Give a description of the method of executing

granite plaster work, and how it is manipulated
in its composition.

119. Give a description of concrete in general and some

of the uses to which it is applied. '

120. Give a description of what the term ''matrix"

is applied to when considering the qualities of
any material.

121. Give a description of what is meant by the term

** Compound Aggregates," and explain the differ-
ence between an inferior and superior aggregate
by an example.

122. Give a description of the ''Voids in Aggregates,"

and what method is used to ascertain the voids.

123. Give a description of the "crushing strength of con-

crete" and upon what it depends.

124. Give a description of the "ramming of concrete"

and the effect that is produced.

CEMENTS AND .CONCRETES

125. Give a description of the thickness of concrete
paving and its relation to the foundations, and to
the amount of traffic on street sidewalks, stable
floors and yards.

126. Give a description of ''Eureka Paving,'' its manip-

ulation, and the purposes for which it is best
adapted.

127. Give a description of the method of preparing the

aggregate for Eureka, and the quantities for the
rough coat and topping.

128. Give a description of the ''levelling and adjust-

ment of the requisite falls'' in the laying of con-
crete pavements and flooring.

129. Give a description of the two parts in the composi-

tion of foundations, and the method of manipula-
tion.

130. Give a description of the "laying concrete paved

ments" and the processes to be employed in order
to leave the surface uniform, straight and solid.

131. Give a description of "trowelling concrete" and

how the best effects may be attained.

132. Give a description of the process termed "grout-

ing," and when it is adopted.

133. Give a description of the methods of composition

of materials that are sometimes adopted for "non-
slippery pavements."

134. Give a description of the preparation of "grooved

and roughened surfaces," that are required for
stables, yards, etc.

135. Give a description of the process employed in col-

oring cement work, and how the best results may-
be obtained, also some of the materials to be used
in producing the color desired.

QUESTIONS

136. Give a description of the method of depositing con-

crete, and what should be avoided in the process.

137. Give a description of the process termed **Retem-

pering/' and the conditions upon which the prop-
er setting of concrete depends.

138. Give a description of how to treat operations in

conci:ete during freezing weather.

139. Give a description of ** Rubble Concrete/' its com-

position and method of manipulation.

140. Give a description of how to face concrete, the

composition employed, and how it is prepared.

141. Give a description of the **top dressing or wearing

surface'' for finished walks, and the method of
mixing the mortar.

142. Give a description of the composition of ''Base-

ment Floors" and the method of their treatment.

143. Give a description of the construction of concrete

stable floors and driveways.

144. Give a description of concrete steps, their manner

of construction, and in what places they may be
advantageously adopted.

145. Give a detailed description of wood framing in

the construction of concrete stairs.

146. Give a description of the materials required for a

concrete staircase, and how to manipulate them
for the several purposes required.

147. Give a description of ** Modelling in Fine Con-

crete" and the several stages in the development
of the process to obtain the proper execution of
the figure or design required.

148. Give a description of how concrete fountains are

constructed, and how a saving of material may
be effected.

CEMENTS AND CONCEETES

149. Give a description of the construction of concrete

tanks, and the manipulation of the materials for
the purposes desired.

150. Give a description of the composition of "concrete

vases/' and the method of manipulating thp ma-
terials.

INDEX

PAOS

MATERIALS :

Limes 2i

Cements 30

Mortars 28

Sand 28

Plasters and laths 31

WORKMANSHIP:

External work 35

Internal work 37

SPECIFICATION CLAUSES:

Materials 42

Workmanship 43

PREPARATION OF BILL OF QUANTITIES:

Materials 46

Workmanship 46

Laths 48

TOOLS AND APPLIANC15S:

Hoes and drags 50

The hawk 52

The mortar board 52

Trowels 52

Floats 52

Moulds 54

The pointer 54

The paddle 55

Stopping and picking out tools. . ^ 55

Mitering rod 55

Scratcher 55

INDEX

pAoa
TOOLS AND APPLIANCES.— Continued.

Hod 55

Sieve 56

Sand screens 56

Mortar beds " , 57

Slack box 57

Lathing 57

Lather's hatchet 58

Nail pocket 58

Cut-off saw 58

PLASTER, LIMB, CEMENTS, SAND, ETC. :

Plaster of Paris 60

Quick and slow setting, plaster 62

Testing 63

French plaster 65

Limes 65

Hydraulic limes 66

Calcination 69

Slaking 70

Mortar 73

Hardening of mortar 78

Magnesia in mortars 82

Effects of salt and frost in mortar. : . . 84

Sugar with cement 86

Sugar in mortar 88

Lime putty 89

Setting stuff 90

Haired putty setting 91

Lime water 91

Hair 91

Fibrous substitutes for hair 92

Sawdust as a substitute for hair 93

Sand 94

Mastic 96

Scotch mastic 96

Conmion mastic 97

Mastic manipulation 97

INDEX

FAGB

PLASTER, LIME, CEMENT, ETC.— Continued:

Hamelein's mastic 97

Mastic cement 98

TERMS AND PROCESSES :

--^hree-coat work 99

^^ First coating 99

^Scratching 100

Rendering 102

Screeds 103

Floating 103

Flanking 106

Scouring coarse stuff Ill

Keying 112

Setting 114

Laying setting stuff 115

Scouring setting stuff 115

Troweling and brushing setting stuff 116

General remarks on setting 117

Common setting 119

Skimming 119

Colored setting 119

Gauged setting 120

Gauged putty set 120

Putty set , 121

Internal angles 121

External angles 121

Skirtings 122

Two coat work 123

One-and-a-half coat work. '. 123

Stucco 124

Old stucco 124

Common stucco 129

Rough stucco 129

Bastard stucco 130

Troweled stucco 130

Colored stucco 131

Method of working cements 131

INDEX

PAOB

TERMS AND PROCESSES.— Continued.

White cement eflSorescence 138

Cornice brackets 139

Cornices 140

Mitring 155

Mitre mould *.../. 156

Fixing enrichments 159

Mitring enrichments 160

Pugging 163

Sound ceilings 164

Cracked plaster work 165

Repairing old plaster 165

Gauged work 168

Joist lines on ceilings. . . , 169

Rough casting 170

VARIOUS METHODS OF RUNNING COR-
NICES, CIRCLES, ELLIPSES AND OTHER

ORNAMENTAL STUCCO WORK :

Diminished colimins 177

Column trammel 180

Constructing plain diminished columns 183

To set out the flutes of diminished columns 183

Constructing diminished fluted columns 185

Forming diminished fluted column by the rim

method 193

Running diminished fluted column by the Col-
lar method 196

Diminished fluted pilasters 200

Pannelled coves 200

Diminished mouldings 204

False screed method 204

Running double diminished mouldings 208

Diminished rule method 208

Top rule method 211

Cupola panels and mouldings 215

Panelled beams 220

INDEX

PAGB

VARIOUS METHODS, ETC.— Continued.

Trammels for elliptical mouldings 220

Templates for elliptical mouldings 224

Plasterer's oval : 228

Coved ceilings 233

Circle mouldings on circular surfaces 233

Forming niches 235

Running an elliptical moulding in situ 240

MISCELLANEOUS MATTERS:

Depeter 243

Sgraffitto : 243

Fresco 251

Fresco secco 255

Indian fresco and marble plaster 256

Scagliolia 260

Artificial marbles 262

Pick's neoplaster 263

Scagliolia manufacture 264

Mixing 270

Colors and quantities 272

Polishing white scagliolia 275

Polishing scagliolia 276

Marezzo 277

Granite finish 282

Granite plastering 283

CEMENTS AND CONCRETES AND HOW TO

USE THEM:

Fine concrete 291

Matrix 293

Aggregate 294

Porous aggregates 295

Compound aggregates 296

Sand and cement 297

Fire-proof aggregates '. 300

Voids in aggregates 302

Crushing strength of concrete 302

INDEX

CEMENT'S AND CONCRETES.— C<Jntinued.

Water for concrete 303

Gauging concrete 305

Ranuning concrete .» 308

Thickness of concrete paving. 1 309

Concrete paving 310

Eureka paving • 312

Eureka aggregate 313

Eureka quantities 314

Levels and falls 315

. Pavement foundations 316

Screeds and sections 318

Laying concrete pavements 320

Troweling concrete 321

Grouting 322

Dusting 322

Temperature • 322

Non-slippery pavements 323

Grooves and roughened surfaces. 323

Stamped concrete 325

Expansion joints 325

Washing yards 328

Stable pavements 328

Concrete slab moulds 329

Slab making 330

Induration concrete slabs 330

Mosaic 331

Concrete mosaic .' 333

Concrete mosaic laid in situ 334

Storing cement 337

Cement mortar 337

Mixing 338

Grout 339

Lime and cement mortar 339

Cement mortar for plastering 339

Materials for making concrete sand 340

Gravel *. . . 341

INDEX

PAGB

CEMENTS AND CONCRETES.— Continued.

Crushed stone 341

Stone versus gravel 342

Cinders 342

Concrete 343

Proportioning materials 344

Aggregate containing fine material 345

Mechanical mixers 346

Mixing by hand 346

Consistency of concrete 347

Use of quick setting cement 347

Coloring cement work 347

Depositing concrete 348

Retempering ^ 349

Concrete exposed to sea- water 349

Concrete work in freezing weather 350

Rubble concrete 350

To face concrete 351

Wood for forms 352

Concrete sidewalks 352

Excavation and preparation of subgrade 353

The subf oundation 353

The foundation , 353

The top dressing or wearing surface 354

Details of construction 384

Concrete basement floors 358

Concrete stable floors and driveways 358

Concrete steps 359

Reinforced concrete fence posts 360

Reinforcement ; 362

Concrete for fence posts 362

Molds for fence posts 363

Attaching fence wire to posts 365

Molding and curing posts 365

Concrete building blocks 368

Tests of concrete fence posts 370

Retempering 378

INDEX

CEMENTS AND CONCRETES.— Continued. '^*"

Some practical notes. 380

Concrete stairway and steps 387

Cast concrete stairs ..... 389

Test of steps 390

Concrete stairs formed in situ 391

Setting out old stairs 391

Nosings and risers 392

Framing staircases 394

Centring for landings and soflSts 396

Waterproof centring 397

Staircase materials 399

Filling in stairs ^ 400

Finishing stairs 404

Non-slippery steps 405

Striking centrings 405

Concrete and iron 406

Setting concrete soffits 408

Fibrous concrete 408

Polished soffits 409

Concrete staircases and fibrous plaster 410

Dowel holes 410

Cast steps 411

Treads and risers 412

Closed outer strings 413

Concrete floors 413

Plaster floors 415

Joist concrete floors ^ . . 416

Caminus concrete cement 417

Concrete floors and coffered ceilings 418

Combined concrete floors and panelled ceilings. 419

Concrete and wood 420

Concrete drying 421

Concrete slab floors 423

Construction of slab floors 425

Hollow floors 427

Concrete roofs 428

790 04\04 C7

34889^ .

INDEX

PAOB

» CEMENTS AND CONCRETES.— Continued.

$1 Notes on concrete 429

a Cast concrete 431

^ Concrete dressing 432

331 Mouldings cast in situ 438

3!)] Modelling in fine concrete 443

392 Concrete fountains 446

331 Concrete tanks 446

^ Concrete sinks ^ 448

397 Garden edging 448

^ Concrete vases . . .♦ 448

Concrete mantel pieces 449

Colored concrete 449

Fixing blocks 452

Typical system of reinforced concrete construc-
tions from various sources 452

Columns and piles 458

Floors, slabs and roofs. .• 468

Beams 469

Arches 471

Lintels 473

Concrete walls 475,

Strong rooms 475

Concrete cofiSns and cementation 475

. Tile fixing 477

Setting floor and wall file 479

Foundations 479

I Lime mortar 480

' Concrete 480

For floors 480

For wood floors 480

In old buildings 481

For hearths 482

For walls 484

Cement 486

Sand 486

Mortar 486

INDEX

CEMENTS AND CONCRETES.— Continued.

Soaking 486

Tiles for floors 486

Ceramics 488

Files for walls and wainscoting 490

Floating wall tile 491

Buttering wall tiles 491

Hearth and facing tile , 492

Cleaning 492

Cutting of tile 492

Tools 492

Laying tile on wood. . . . '. 493

Good concrete 495

Reinforced concrete 500

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