moulding or casting. This subject is exhaustively treated in the
_Vollständige Anleitung zum Formen und Giessen_, by Eduard Uhlenhuth;
Vienna, A. Hartleben, price 3s. On the subject of paper consult the
_Handbuch der praktischen Papier-Fabrikation_, by Dr. Stanislaus
Mierzinski, three volumes, which is not only the latest, but by far the
most comprehensive, work on the subject with which I am acquainted.
And here I may observe in this connection that if my references have
been chiefly to German works, it is because, in the minor technical
applications of chemistry to the arts, and in preparing intelligible
practical treatises on such subjects, the Germans have been, especially
of late, by far the first nation in Europe.
I may mention that since writing the foregoing passages I purchased,
for a mere trifle, in Florence two carved heads of the fourteenth
century in walnut wood. They had suffered very much from time and
wanton abuse, their noses having been hacked off. I made a mixture of
soft paper-paste and gum-arabic, working the two thoroughly in together
with a knife-blade till the composition was as soft as butter. This
thorough maceration is essential to produce a durable body. With this I
filled up the holes, made new noses, and painted the whole with Vandyke
brown, or brown-black. In a few minutes the restoration was complete,
and the heads which had cost one franc each are now worth at least
thirty francs. I should say that the portions restored are as hard as
the original wood.
It is not always an easy matter to reduce paper to a perfectly soft
paste, such as is called in French _papier-pourri_. A small quantity
can be mashed with a knife-blade and flour-paste or gum. A large
quantity is prepared as follows:--
Take clippings of paper and leave them a long time in water, which
must be occasionally changed. When quite dissolved or soft, bray the
paper in a mortar, and finally boil in very hot water. To give it
consistency, add flour-paste or gum. This makes a very fine cement,
which will receive the most delicate impression. It is invaluable for
all kinds of dry mending.
As I have shown, it can be applied to make or mend defective leaves of
books, to fill up worm-holes in leaves, to repair drawings and pictures
on wood or canvas, and when mixed with any gum which sets hard, to
restore, add to, fill, or imitate woodwork. Under pressure and combined
with different powders it becomes as hard as ebony and fire-proof. Its
extraordinary value and general utility are as yet very far from being
much known.
MENDING STONE-WORK
MOSAICS--CERESA-WORK--PORCELAIN OR CROCKERY MOSAIC
Mending or repairing _stone_, involving its imitations, is a widely
extended branch of technical science, and one which has of late years
called forth much invention. The most widely spread and ancient means
of uniting and repairing this material is mortar, or the mixture of
burned and then slacked lime with water. Lime is made most commonly
from limestone or marble. It improves in quality when carbonate of
lime in organic formation, such as sea-shells, is used; and there are
degrees of excellence in these, from common oyster-shells to others
of a finer kind, such as those with which the brilliantly white and
hard _chunam_ of India is made. In certain places mortar, when well
made, becomes with age as hard as flint. In American towns, where
anthracite coal is burned, it rots away in chimneys under the influence
of sulphurous acid with great rapidity. In the Pacific Islands, where
lime is made from delicate small sea-shells or coral, and mortar is
like a paint or enamel, a missionary has recorded that, when he taught
the natives how to make it, they whitewashed everything, even to the
children, who thus became white people.
The misapplied word _mastic_, which suggests a gum, refers to certain
modifications of mortar into which _oil_ enters; also the oxides of
lead or zinc. “Oil forms with these an insoluble soap, which includes
or binds the other materials, forming, after one month’s drying, a very
hard substance,” which some say is as hard as stone, but which depends
entirely on the quality and combination; for I have seen so-called
_mastic_ applied to coating cheaply built houses, which cracked or
crumbled away like mere plaster of Paris.
To thoroughly amalgamate mastics, it is usual to put their ingredients
into casks which are two-thirds filled, and then revolved by machinery.
The oil is then added. At least two days are required for the process.
The following recipes for mastics are among the best, having been
approved by LEHNER. It may here be remarked, once for all, not only
as regards mastics, but all recipes in this work, that unless the
materials indicated are of the very best quality, and the processes be
most thoroughly carried out, the experimenter cannot expect complete
success. More than this, the experimenter must not be satisfied with a
single trial. If every recipe could be at once executed by every cook,
we should find the most exquisite cookery on every table in Europe.
I once published the correct recipe for making objects of a peculiar
kind of _papier-mâché_ hardened. It was very easy to make. I had seen
specimens of the ware, and I received the recipe from the inventor.
Moreover, a great deal of money had been made by it. However, soon
after I had published it I received an indignant letter from the head
of a large manufacturing house, stating that they had tried my recipe
and utterly failed!
FRENCH MASTIC:--
Quartz or flint sand, parts 300
Powdered quicklime, ” 100
Litharge, ” 50
Linseed-oil, ” 35
PAGET’S MASTIC:--
Flint sand 315
Washed chalk 105
White lead 25
Minium 10
Sugar of lead in solution 45
Linseed-oil 35
The paste or “dough” thus formed should be ground with horizontal
rollers in a mill, such as is used for chocolate, until all the
ingredients are _very_ thoroughly amalgamated.
A VERY GOOD CEMENT FOR MENDING, especially where the objects are
exposed to water, whether they be of stone or earthenware, is made as
follows:--
Powdered glass 40
Washed litharge 40
Linseed-oil varnish 20
The powdered glass is prepared by heating glass red-hot, casting it
into water, grinding and sifting it. This powder is saturated with the
linseed-oil varnish, and heated in a kettle. This cement sets hard in
three days. LEHNER observes that glass-powder serves in such recipes to
resist the action of acids, &c., since it forms in combination on the
surface a glaze of great hardness; that is, the glass and lead form a
chemical combination. Pulverised calcined glass therefore acts not as
an “indifferent” but as a chemical ingredient.
CASEINE, or Cheese, forms the basis of several recipes for mending
stone, as when there are holes in a block or the mortar has given way.
To prepare it for use (LEHNER), we let milk stand in a cool place,
skimming away with the utmost care all the cream. Place this on a
filter, and pour on it rain-water till it is purified from every trace
of lactic acid; then tie it in a cloth, boil it in water, and spread
it on blotting-paper in a warm place, when it will be a horn-like
substance. This will keep for a long time. To prepare it for use, rub
it in a saucer with water.
TO MEND STONE make the following:--
Caseine 12
Slacked lime 50
Fine sand 50
Another recipe:--
Boil new cheese in water till it draws out in threads, stirring in
slacked lime and sifted wood-ashes in the following proportions:--
Cheese 100
Water 200
Slacked lime 25
Wood-ashes 20
This may also be used to close cavities in trees or in wood.
A CHEESE CEMENT FOR STONE, and for many other purposes, is made as
follows. It may be kept for a long time, and is very durable (LEHNER):--
Caseine 200
Calcined lime 40
Camphor 1
This must be closely incorporated and kept well corked. When it is to
be used mix it with water, and apply at once.
The following cement was used by the Romans especially in setting
mosaics. It becomes as hard as marble, and sets with great
rapidity:--To one quart of milk add the white of five eggs, and stir in
powdered quicklime till a paste is formed. This composition may be used
to repair or make _scagliola_, which is fragments of marble or stone
embedded in a hard mass. When it sets, polish the surface with rasps,
and rub down with a rough stone, and finally polish with marble dust,
and then emery or tripoli. Beautiful slabs for tables, columns, floors,
and walls can thus be made. It is valuable for repairing.
CERESA is allied to this. We make a basis of this or any other cement
which will _hold firmly_, and press into the surface powdered glass,
which may be fine or of any degree of coarseness. Coarse grains shine
most brilliantly; fine powder is best adapted to delicate shading.
The effect is best when mosaic stones and gold cubes are sparingly
introduced. To make the gold cubes, take two small panes of window
glass, cover one side of each with varnish or mastic cement, lay
between them gold-leaf, and join them. Very beautiful pictures can be
made in this manner. Nor is it at all necessary that they should be
finely executed for ordinary decoration. All that is needed for this
beautiful and little-known art is the cement, a quantity of glass or
stone of different colours, and a mortar and pestle. The mosaic cubes,
with those of gold, can be bought in London.
Allied to this is an art which I believe I can claim to have invented.
It consists of breaking waste chinaware, crockery, or fictile ware
into small squares or triangles, and setting them as mosaic in
cement. The advantage of it is the cheapness of the material, and the
infinite number of shades of colour which can be selected for it.
Its disadvantage is, that it will not wear as a pavement, but it is
perfectly adapted to walls.
A STRONG, COARSE CEMENT FOR BRICK OR STONE WORK in building is made as
follows:--
Slacked lime 40
Brick-dust 10
Iron filings 10
Ox-blood 8
Water 8
The blood is stirred as it comes from the slaughtered beast with a
broom for ten minutes to break the fibre. It should then be mixed with
the water and kneaded with the powder. Glue may be substituted for the
blood. This cement, if properly made, sets very hard and adhesively.
FOR TILES, BRICKS, OR COMPOSITION:--
Slacked lime 100
Sifted stone-coal ashes 50
Stirred ox-blood 15
It may be observed that many of the cheaper cements can be employed to
form large bricks by combination with broken stone or rubble, gravel,
pebbles, brickbats, &c. Another method, called CONCRETE, is to make
cases of boards, and to form a solid wall by pouring in the mixture,
or ramming it down, according to its hardness. Thus a house is made
entirely in one piece; but its excellence depends entirely on the
quality of the cement employed, and on the care taken in building.
Simple lime mortar, if not of a superior quality, hastily formed, as I
have seen, is very apt to crack and break off. Where hydraulic cement
is cheap and good, houses can be built as firm as granite. A good and
strong cement of this kind can be made as follows:--
Burned lime 10
Caseine 12
Hydraulic cement 30
The proportions may be very much varied in such cements according to
their price, but generally with a satisfactory result.
Fractures or discolorations in marble, as in statuary, are so perfectly
repaired in Florence that the juncture is not perceptible. Even dark
spots are drilled out. The process is to drill a round concave hole,
and cut the piece to be inserted so as to exactly fit as a convex
plug. It is then fastened in with transparent mastic or other clear
cement. It will be seen, on due consideration, that this is extremely
ingenious, because by it alone can a perfectly tight fit be secured.
By turning the plug in the hollow it speedily grinds itself into an
accurate plug; so when the cement is applied it can be reduced to a
minimum--in fact, by this means the line of junction is reduced to its
finest limit.
Where a very strong cement is needed for stone-work, it can be prepared
by mixing a fine cement powder--_e.g._, Portland cement--with liquid
silicate of soda. As it dries almost at once, it must be promptly
applied. It is particularly well adapted for building under water,
since it then becomes extremely hard. Before applying it smear the
stone with pure silicate.
The following is highly commended by LEHNER:--
Mending statues of gypsum or plaster of Paris is allied to stone-work.
The broken edges are washed with water till no more is absorbed and the
surface remains wet. Then stir fresh calcined white plaster of Paris
with much water to a thin paste, and continue to stir this till it is
cold. Then rapidly paint this paste on the broken edges, continuing to
press the two together till they set hard.
It is, says LEHNER, a peculiarity of gypsum that when mixed with _alum_
dissolved in water it takes a much longer time to harden, but is very
much harder in the end. Thus, if we let the powdered gypsum lie for
twenty-four hours in alum-water, dry it, and then calcine it again, the
powder when mixed with water sets to a stone as hard as marble.
Plaster of Paris and alum, combined with the fine powder of calcined
glass, form a very hard and durable cement, of very general utility in
all mending of stone-work.
For an exhaustive work on the subject of not only mending stone-work,
but also of making artificial stone and many cements, as well as
combining and adapting to use paper, cellulose, sawdust and shavings,
gypsum, chalk, glue, &c., including not only ancient but also the
most recent recipes, consult _Die Fabrikation künstlicher plastischer
Massen_, by Johannes Hofer; Leipzig, A. Hartleben, price 4s.
REPAIRING IVORY
Works of art in carved ivory or bone are very valuable when perfect,
yet when broken or defective they may very often be purchased for
a trifle. Yet the process of mending them or restoring the missing
portions is not difficult.
The first thing to consider is the colour. When old ivory has only
acquired a delicate hue, as of Naples yellow, this adds to its
attractiveness; nor are the brownish shadows and marks which gather
in the angles of the reliefs repulsive. These may be left untouched,
and even imitated. But a great deal of old ivory becomes of blackish
bistre, or of a dirty, spotted brown or neutral tint, which has nothing
in common with artistic effect, and suggests, like old slums in cities,
more that is repulsive than picturesque. To clean such pieces, dissolve
rock-alum in rain-water till it is white or forms a full saturation.
Boil this, and keep the ivory in the boiling solution for about an
hour, taking it out from time to time and cleaning it with a soft
brush. Then let it dry in a damp linen or muslin rag; it will then be
cleaned.
Ivory is often bleached by the simple process of damping, or wiping
it with water and then exposing it to the rays of the sun; which
must, however, be frequently repeated. According to LEHNER, the only
perfect and certain process by which any ivory can be cleaned is to
steep the article for some time in ether or benzole, in order to
extract any fatty matter, then to wash it in water, and finally keep
it in super-oxide of hydrogen (_Wasserstoff, super-oxide_) till it is
bleached, after which wash again in water.
TO SUPPLY MISSING PORTIONS.--Take ivory-dust, such as can be bought of
every ivory-turner, sift it to an impalpable powder, or else levigate
or grind it down under water as fine as flour in a mortar. Then combine
this with gum arabic, in alum solution, or the silicate of potash.
Egg-shells, levigated, may be substituted for the ivory-dust, and are
even less likely to turn grey; and very fine white glue or gelatine of
the clearest kind may be substituted for the gum-arabic.
LOUIS EDGAR ANDÉS, in his able work on Ivory, Horn, Mother-of-Pearl,
and Tortoise-shell, explains a process much like that already
described. According to him, take finely powdered bone (or ivory-dust),
combine it with white of eggs, and the result will be an intensely hard
substance, which can be turned or carved like ivory. To perfect this
the mass should be subjected to a heat of from 50° to 60° centigrade,
and then to strong pressure. Gelatine or best glue, with glycerine, is
quite as good as the white of eggs, and it may to advantage be combined
with the latter. Having very thoroughly mixed the composition, take
the broken ivory article, repair the missing portions, and fill the
cavities with the paste. Though not equal to celluloid as an imitation
of new and fresh ivory, this cement is very much like old bone and
ivory, and _after a little experimenting_ the artistic amateur may
succeed in so blending the _binder_ or adhesive with the dust as to
take casts which are almost perfect imitations of the originals. But
let it be observed in this, as in everything, one must not expect
perfect success at a first trial, as too many do.
When the paste is dry, smooth the surface with a sharp cutter, so as to
remove any small projections, and then polish it, first with fine emery
or tripoli, then with a burnisher, finally by hand.
If you have, for example, an old flat plate of ivory, like one of the
fourteenth century now before me, which I bought for a mere trifle
because it was broken, lay it in an exactly fitting box--a strip of tin
in a square will answer--and fill in the vacancy. The missing ornament
on the upper side can be carved, or even supplied from a hardened stamp
or mould of rolled soft bread-crumb. This bread-crumb can be made very
hard by admixture with a very little nitric acid and water. Imitation
meerschaum pipes, which are rather like ivory or bone, are made from
this composition by pressure.
I may here mention that this ivory or bone cement, which is little
known, is admirably adapted to repair broken inlaying. There was
in Florence, in the sixteenth century, an extensive manufacture of
delicate bas-reliefs for small caskets from _lime and rice_, which
greatly resembled bone or ivory. It was extremely durable, probably
from being extremely well worked. Specimens of it bring a high price.
A very slight infusion of Naples yellow, to which a suspicion of
brown, reduced in Chinese white, has been added, gives to the paste an
old-ivory colour. The corners and outlines may be shaded in Vandyke
brown.
Before attempting to glue or mastic fractured ivories, they should
always be washed in the alum solution, else they will often refuse to
adhere.
When there is a little addition of whiting and a little oil, very well
worked into the ivory paste, and it is allowed to dry thoroughly, it
may be cut or carved into any shape.
Ivory or bone when very old becomes brittle or crumbling and falls
to powder, because certain organic substances dry out of it, leaving
chiefly lime as their residue. When the ivories from Nineveh were
brought to the British Museum the celebrated Sir Joseph Hooker
suggested that they should be steeped in gelatine. This effected a
perfect restoration. When a case occurs in which an ivory article, a
bone, or skull is so fragile that it will not bear the slightest touch
without falling to dust, it may often be saved by gently _spraying_ on
it water in which gelatine or glue has been dissolved. As the glue may
be made by boiling old gloves, and as a spray can be easily improvised,
it will be seen that excavators and openers of ancient tombs might
by this means save thousands of curious relics which are allowed to
perish. As it is certainly a species of mending or of restoration, it
is in place in this work. This is especially to be desired as to skulls
of the earliest ages, which are of inestimable value, of which we have
so very few, and of which thousands have perished which might have been
preserved in the manner which I have indicated.
_Sprays_ for spreading perfume or medicated liquids, which can be
adapted to thin liquid glue, may be had of all chemists. But we can
effect the purpose better by taking a tooth-brush, or any brush of
the kind, wetting, and then drawing it over a dull edge of a knife or
a strip of tin. According to J. C. WIEGLEB, a Frenchman in his time
received a very large pension for this invention, which was applied
to spraying pastels. The Romans made a spray, very imperfectly, by
suddenly squeezing or throwing liquids from a sponge.
Ivory handles to knives and forks, when loose, can be best reset by
first pouring in a little strong vinegar. When dry use acidulated glue.
A common recipe for this purpose is the following:--
Resin (colophonium) 20 parts
Sulphur 5 ”
Iron filings 8 ”
Heat, and use while soft.
In repairing ivory it is often necessary to stain it of different
colours. Most of the old works on recipes contain directions for this.
In that of RIS PAQUOT they are given as follows:--
First prepare a mixture of copper filings, rock-alum, and Roman
vitriol. Boil it, let it be for six days, then add a little rock-alum.
The piece of ivory to be dyed is kept in this solution for half
an-hour. _To dye Red._--Boil logwood chips or cochineal in water; when
hot add lead dross (_cendre gravelée_) about 25 grammes, keep it in the
fire till the colour has taken, then add rock-alum. This is strained
through linen, and the ivory to be dyed is put into this liquor.
_Green._--Take one quart of lye made from vine-ashes (_cendre de
sarment_), 7 grammes of powdered verdigris, a handful of common salt,
with a little alum. Boil it to one-half; as soon as it is taken from
the fire place the ivory in it, and leave it till properly coloured.
_Blue._--Dissolve indigo and potash in water, and then mix this with
a quart of vine-ash lye. _Black._--Boil the ivory in the following
composition:--Vinegar, 500 grammes; gall-nuts pulverised, 12 grammes;
nut-shells, 12 grammes. Boil down to one-half. These are all very
strong dyes, which may be used for other substances.
“Ivory can be softened and made almost plastic by soaking in phosphoric
acid. When washed with water, pressed, and dried, it will regain its
former consistency.” Ivory-dust thus treated can be really rendered
plastic. The process requires care.
In the _Magia Naturalis_ of HILDEBRAND, a work of the sixteenth
century, we are told that ivory can be imitated or repaired with a
cement made of powdered egg-shells, gum-arabic in solution, and the
white of eggs. Dry it in the sun.
Allied to ivory is Horn. Deer-horn was frequently used as a material
whence to make a substance which was moulded into many forms. For
this purpose the hardest part of the horns was selected and filed or
powdered, and then boiled in strong potash lye. Thus it became a paste,
which was promptly pressed into moulds. When dry the figures were
carefully polished. Ox-horn can be treated in the same manner. When
cracked, carved horns or powder-flasks can be mended with this paste;
also with mastic and whiting. Horn in a soft state is easily coloured
by mixing with it any dye.[3]
It has been recently complained in a leading review, in an article on
sales of ancient works of art, that imitations of antique works of
ivory are now carried to such perfection that even the learned in such
matters have been deceived. This is perfectly true, and therefore it
is the greater pity that such imitation, which is not necessarily very
expensive, cannot be extended to our great museums, the wealthiest of
which thus far seldom get beyond rough, plain plaster-casts to make
duplicates of ivory-work. The artists in imitation seem to be entirely
in the employ of the people who deliberately sell counterfeits for
genuine relics of antiquity. But, as Martin Luther or some one once
remarked in reference to adapting hymns to popular airs, “There was no
reason why the devil should keep all the good tunes to himself,” so is
there none why duplicates of thousands of exquisite works in ivory,
bone, and horn should not be better known to the world. It is possible
that, to the world at large, there is little _real_ interest in such
works; but interest will come in time with familiarity.
_Apropos_ to ivory, or horn, there is a process of applying an
imitation of them to any kind of surface, which is, when executed with
skill, remarkably effective. It is chiefly executed in Vienna, where
it is applied to leather, plaster of Paris, wood, and wall-paper. With
variations, it is essentially as follows:--