of wine, 20 parts; and commercial pure 40 per cent aldehyde, 20 parts.
These liquids are quickly mixed together in the proportion of 200, 50,
and 5 parts, whereupon the mixture is poured on the glass previously
cleaned with soda solution, and the gilding will be effected in a
short time. The gold coating is said to keep intact for years.
II.—Coat the places to be gilded thinly with a saturated borax
solution, lay the gold leaf on this and press down well and uniformly
with cotton-wool. Heat the glass over a spirit flame, until the borax
melts, and allow to cool off. If the glass is to be decorated with gilt
letters or designs, paint the places to be gilded with water-glass
solution of 40° Bé.; lay on the gold leaf, and press down uniformly.
Then heat the object to 86° F., so that it dries a little, sketch the
letters or figures on with a lead pencil, erase the superfluous gold,
and allow the articles to dry completely at a higher temperature.
«Green Gilding.»—This can be obtained conveniently by the galvanic
process, by means of anodes of sheet platinum with the following
composition: Water, 10,000 parts, by weight; sodium phosphate, 200
parts; sodium sulphate, 35 parts; potassium carbonate, 10 parts; 1
ducat gold from gold chloride, potassium cyanide (100 per cent), 20
parts. Dissolve the first three salts in 10,000 parts of cold water and
add, with stirring, the gold chloride and potassium cyanide. Before the
first use boil down the solution thoroughly about one-half, replacing
the evaporating water and filter after cooling, in case a sediment
should appear. To this gold bath very carefully add some silver bath.
The platinum sheets which are to serve as anodes are employed 1 3/4
inches long, 1/3 inch broad, and 1/100 of an inch thick. With these
anodes the gold tone can be somewhat regulated by hanging more or less
deeply into the solution during the gilding. The current should have a
tension of 3 to 4 volts. In the case of batteries three Busen elements
are connected for current tension. It is difficult to produce old gold
on silver, especially if the raised portions are to appear green.
It is most advantageous first to lightly copper the silver goods,
taking the copper off again on the high places by brushing with pumice
stone. After that hang at once in the above gold bath. If the embossed
portions should be too mat, brighten slightly by scratching with a
very fine brass wire brush. In this manner a handsome brown shade is
obtained in the deep places and a green color on the raised portions.
This process requires practice. Since this method will produce only
a very light gilding, a coating of white varnish will protect the
articles from tarnishing.
«Incrusting with Gold.»—The article is first made perfectly bright, and
those places which are to be gilt are covered with a matt consisting
of white lead ground with gum water, made into a paste which can be
applied like a thick paint by means of a pen or brush. Those places
of the metal surface not covered by the paint are coated with asphalt
varnish—a solution of asphaltum in benzine to which oil of turpentine
is added to render it less volatile. After this is done lay the article
in water, so that the white lead paint comes off, and put it into a
gilding bath. By the electric current gold is precipitated on the
bright parts of the metal. When the layer of gold is thick enough lift
the object from the bath, wash, let dry and lay it into a vessel filled
with benzol. The asphalt dissolves in the benzol, and the {579} desired
design appears in gold on the bronze or silver ground. This operation
may also be performed by coating the whole article with asphalt varnish
and executing the design by means of a blunt graver which only takes
away the varnish covering without scratching the metal itself. On the
parts thus bared gold is deposited by the electric current and the
varnish coating is then removed.
«Ivory Gilding.»—I.—The pattern is painted with a fine camel’s-hair
pencil, moistened with gold chloride. Hold the ivory over the mouth
of a bottle in which hydrogen gas is generated (by the action of
dilute sulphuric acid on zinc waste). The hydrogen reduces the auric
chloride in the painted places into metallic gold, and the gold film
precipitated in this manner will quickly obtain a considerable luster.
The gold film is very thin, but durable.
II.—This is especially suitable for monograms. Take gold bronze and
place as much as can be taken up with the point of a knife in a
color-cup, moistening with a few drops of genuine English gold paint.
Coat the raised portions sparingly with gold, using a fine pencil;
next, coat the outer and inner borders of the design. When the work is
done, and if the staining and gilding have been unsuccessful, which
occurs frequently at the outset, lay the work for 5 or 10 minutes in
warmed lead water and brush off with pumice stone. By this process
very fine shades are often obtained which cannot be produced by mere
staining. Since the gold readily wears off on the high places of the
work, it is well to lightly coat these portions with a thin shellac
solution before gilding. This will cause the gilding to be more
permanent.
«Mat Gilding.»—To obtain a handsome mat gilding the article, after
having been neatly polished, is passed through a sand-blast, such as is
found in glass-grinding and etching establishments; next, the object
is carefully cleansed of fine sand (if possible, by annealing and
decocting), whereupon it is gilt and subsequently brushed mat with the
brass brush. Where there is no sand-blast, the article is deadened with
the steel wire brush, which will produce a satisfactory result, after
some practice. After that, treatment is as above. The above-mentioned
applies in general only to silver articles. In case of articles
of gold, brass, or tombac, it is better to previously silver them
strongly, since they are too hard for direct treatment with the steel
wire brush, and a really correct mat cannot be attained. The brushes
referred to are, of course, circular brushes for the lathe.
«Dead-Gilding of an Alloy of Copper and Zinc.»—The parts which are to
be deadened must be isolated from those which are to be polished, and
also from those which are to be concealed, and which therefore are not
to be gilded. For this purpose they are coated with a paste made of
Spanish white mixed with water. The articles prepared in this manner
are then attached by means of iron wire to an iron rod and suspended in
a furnace constructed for this process. The floor of this furnace is
covered on four sides with plates of enameled earthenware for receiving
the portions spattered about of the salt mixture given off later.
In the middle is an oven constructed like a cooking stove, on which is
an iron tripod for carrying the deadening pan; this latter is cemented
into a second pan of cast iron, the intervening space being filled up
with stove cement. In the middle of the pan is the bottom or sill,
provided with a thick cast-iron plate, forming the hearth. On all four
sides of the latter are low brick walls, connecting with the floor of
the furnace, and the whole is covered with thick sheet metal. On the
side of the furnace opposite the side arranged for carrying the pans,
is a boiler in which boiling water is kept. On the same side of the
furnace, but outside it, is a large oval tub of a capacity of about 700
or 800 quarts, which is kept filled with water. The upper portions of
the staves of this tub are covered with linen to absorb all parts that
are spattered about.
«Powder for Gilding Metals.»—I.—In a solution of perchloride of gold
soak small pieces of linen which are dried over the solution so that
the drops falling therefrom are saved. When the rags are dry burn them,
carefully gathering the ashes, which ashes, stirred with a little
water, are used for gilding either with pumice stone or with a cork.
For the hollows, use a small piece of soft wood, linden, or poplar.
II.—Dissolve the pure gold or the leaf in nitro-muriatic acid and then
precipitate it by a piece of copper or by a solution of iron sulphate.
The precipitate, if by copper, must be digested with distilled vinegar
and then washed by pouring water over it repeatedly and dried. This
precipitate will be in the form of very fine powder; it works better
and is {580} more easily burnished than gold leaf ground with honey.
«Gilding Pastes.»—I.—A good gilding paste is prepared as follows:
Slowly melt an ounce of pure lard over the fire, add 1/2 a
teaspoonful of juice of squills, and stir up the mixture well,
subsequently adding 10 drops of spirit of sal ammoniac. If the mixture
is not stiff enough after cooling, the firmness may be enhanced by an
admixture of 1/3 to 1/2 ounce of pure melted beef-tallow. A larger
addition of tallow is necessary if the white of an egg is added. After
each addition the mixture should be stirred up well and the white of
egg should be added, not to the warm, but almost cold, mixture.
II.—Alum, 3 parts, by weight; saltpeter, 6 parts; sulphate of zinc,
3 parts; common salt, 3 parts. Mix all into a thick paste, dip the
articles into it, and heat them, until nearly black, on a piece of
sheet iron over a clear coke or charcoal fire; then plunge them into
cold water.
«Red Gilding.»—This is obtained by the use of a mixture of equal parts
of verdigris and powdered tartar, with which the article is coated;
subsequently burning it off on a moderate coal fire. Cool in water, dip
the article in a pickle of tartar, scratch it, and a handsome red shade
will be the result, which has not attacked the gilding in any way.
«Regilding Mat Articles.»—In order to regenerate dead gold trinkets
without having to color them again—which is, as a rule, impossible,
because the gold is too weak to stand a second coloring—it is
advisable to copper these articles over before gilding them. After the
copper has deposited all over, the object, well cleaned and scratched,
is hung in the gilding. By this manipulation much time and vexation is
saved, such as every jeweler will have experienced in gilding mat gold
articles. The article also acquires a faultless new appearance. Here
are two recipes for the preparation of copper baths:
I.—Distilled boiling water, 2,000 parts, by weight; sodium sulphate, 10
parts; potassium cyanide, 15 parts; cupric acetate, 15 parts; sodium
carbonate, 20 parts; ammonia, 12 parts.
II.—Dissolve crystallized verdigris, 20 parts, by weight, and potassium
cyanide, 42 parts, in 1,000 parts of boiling water.
«Silk Gilding.»—This can only be accomplished by the electric process.
The fiber is first rendered conductive by impregnation with silver
nitrate solution and reduction of same with grape sugar and diluted
alkali, or, best of all, with Raschig’s reduction salt. In place of the
silver nitrate, a solution of lead acetate or copper acetate may be
employed. The silk thus impregnated is treated in the solution of an
alkaline sulphide, e. g., sodium sulphide, ammonium sulphide, or else
with hydrogen sulphide, thus producing a conductive coating of metallic
sulphide. Upon this gold can be precipitated by electrodeposition in
the usual way.
«Spot Gilding.»—Gilding in spots, producing a very fine appearance, is
done by putting a thin coat of oil on those parts of the metal where
the gilding is not to appear; the gold will then be deposited in those
spots only where there is no oil, and the oil is easily removed when
the work is finished.
«Gilding Steel.»—Pure gold is dissolved in aqua regia; the solution is
allowed to evaporate until the acid in excess has gone. The precipitate
is placed in clean water, 3 times the quantity of sulphuric acid is
added and the whole left to stand for 24 hours in a well-closed flask,
until the ethereal gold solution floats on top. By moistening polished
steel with the solution a very handsome gilding is obtained. By the
application of designs with any desired varnish the appearance of a
mixture of gold and steel may be imparted to the article.
«Wood Gilding.»—I.—The moldings, ledges, etc., to be gilded are painted
with a strong solution of joiners’ glue, which is left to harden well,
whereupon 8 to 10 coatings of glue mixed with whitening are given.
Each coat must, of course, be thoroughly dry, before commencing the
next. After this has been done, paint with a strong mixture of glue
and minium, and while this is still wet, put on the gold leaflets and
press them down with cotton. To impart the fine gloss, polish with a
burnishing agate after the superfluous gold has been removed.
II.—Proceed as above, but take silver leaf instead of gold leaf,
and after all is thoroughly dry and the superfluous silver has been
removed, apply a coating of good gold lacquer. The effect will be
equally satisfactory.
«Zinc Gilding.»—I.—Gilding by means of zinc contact may be accomplished
with the following formula: Two parts, by weight, of gold chloride;
5 parts, by weight, of potassium cyanide; 10 parts, {581} by weight,
of sulphite of soda; and 60 parts, by weight, of sodium phosphate are
dissolved in 1,000 parts of water. When used the bath must be hot. A
cold bath without the addition of potassium cyanide may also be used
for gilding, and this consists of 7 parts, by weight, of gold chloride;
30 parts, by weight, of yellow prussiate of potash; 30 parts, by
weight, of potash; 30 parts, by weight, of common salt in 1,000 parts
of water.
II.—To gild zinc articles, dissolve 20 parts of gold chloride in 20
parts of distilled water, and 80 parts of potassium cyanide in 80 parts
of water, mix the solutions, stir a few times, filter, and add tartar,
5 parts, and fine chalk, 100 parts. The resulting paste is applied with
a brush. Objects of copper and brass are previously coated with zinc.
This is done in the following manner: Heat a concentrated sal ammoniac
solution to the boiling point with addition of zinc dust and immerse
the thoroughly cleaned objects until a uniform zinc coating has formed.
Or boil the articles in a concentrated caustic soda solution with zinc
dust.
«OXIDIZING PROCESSES:»
«Aluminum Plating.»—I.—To plate iron and other metals with pure
aluminum, deoxidize the pieces with a solution of borax and place them
in an enameling oven, fitted for receiving metallic vapors. Raise
the temperature to 1,832° to 2,732° F. Introduce the aluminum vapors
generated by heating a quantity of the metal on the sand bath. When
the vapors come in contact with the metallic surfaces, the aluminum is
deposited. The vapors that have not been used or are exhausted may be
conducted into a vessel of water.
«To Copper Aluminum», take
II.—Sulphate of copper 30 parts
Cream of tartar 30 parts
Soda 25 parts
Water 1,000 parts
The articles to be coppered are merely dipped in this bath, but they
must be well cleaned previously.
«Antimony Baths.»—I.—By dissolving 15 parts, by weight, of tartar
emetic and 15 parts of prepared tartar in 500 parts of hot water and
adding 45–60 parts of hydrochloric acid and 45–60 parts of powdered
antimony, brass becomes coated in the boiling liquid with beautiful
antimony colors. In this manner it is possible to impart to brass
golden, copper-red, violet, or bluish-gray shades, according to a
shorter or longer stay of the objects in the liquid. These antimony
colors possess a handsome luster, are permanent, and never change in
the air.
II.—Carbonate of soda, 200 parts, by weight; sulphide of antimony, 50
parts; water, 1,000 parts. Heat the whole in a porcelain capsule for
1 hour, keeping constantly in ebullition; next, filter the solution,
which, on cooling, leaves a precipitate, which boil again with the
liquid for one-half hour, whereupon the bath is ready for use.
«To Coat Brass Articles with Antimony Colors.»—Dissolve 15 parts, by
weight, of tartar emetic and 15 parts, by weight, of powdered tartar
in 500 parts, by weight, of hot water and add 50 parts, by weight,
of hydrochloric acid, and 50 parts, by weight, of powdered antimony.
Into this mixture, heated to a boil, the immersed articles become
covered with luster colors, a golden shade appearing at first, which
is succeeded by one of copper red. If the objects remain longer in the
liquid, the color passes into violet and finally into bluish gray.
«Brassing.»—I.—To brass small articles of iron or steel drop them
into a quart of water and 1/2 ounce each of sulphate of copper and
protochloride of tin. Stir the articles in this solution until desired
color is obtained.
II.—Brassing Zinc, Steel, Cast Iron, etc.—Acetate of copper, 100 parts,
by weight; cyanide of potassium, 250 parts; bisulphite of soda, 200
parts; liquid ammonia, 100 parts; protochloride of zinc, 80 parts;
distilled water, 10,000 parts. Dissolve the cyanide of potassium
and the bisulphite of soda. On the other hand, dissolve the ammonia
in three-fourths of the water and the protochloride of zinc in the
remaining water; next, mix the two solutions. This bath is excellent
for brassing zinc and is used cold.
III.—Acetate of copper, 125 parts, by weight; cyanide of potassium, 400
parts; protochloride of zinc, 100 parts; liquid ammonia, 100 parts;
distilled water, 8,000 to 10,000 parts. Proceed as above described.
IV.—Acetate of copper, 150 parts, by weight; carbonate of soda, 1,000
parts; cyanide of potassium, 550 parts; bisulphite of soda, 200 parts;
protochloride of zinc, 100 parts. Proceed as above. This bath serves
for iron, cast iron, and steel, and is used cold. {582}
«Colored Rings on Metal.»—Dissolve 200 parts, by weight, of caustic
potash in 2,000 parts of water and add 50 parts of litharge. Boil
this solution for half an hour, taking care that a little of the
litharge remains undissolved. When cold, pour off the clear fluid; it
is then ready for use. Move the object to and fro in the solution; a
yellow-brown color appears, becoming in turn white, yellow, red, and
finally a beautiful violet and blue. As soon as the desired color is
obtained, remove the article quickly from the solution, rinse in clean
water, and dry in sawdust.
«Green or Gold Color for Brass.»—French articles of brass, both
cast and made of sheet brass, mostly exhibit a golden color, which
is produced by a copper coating. This color is prepared as follows:
Dissolve 50 parts, by weight, of caustic soda and 40 parts of milk
sugar in 1,000 parts of water and boil a quarter of an hour. The
solution finally acquires a dark-yellow color. Now add to the mixture,
which is removed from the fire, 40 parts of concentrated cold blue
vitriol solution. A red precipitate is obtained from the vitriol,
which falls to the bottom at 167° F. Next a wooden sieve, fitted to
the vessel, is put into the liquid with the polished brass articles.
Toward the end of the second minute the golden color is usually dark
enough. The sieve with the articles is taken out and the latter are
washed and dried in sawdust. If they remain in the copper solution they
soon assume a green color, which in a short time passes into yellow and
bluish green, and finally into the iridescent colors. These shades must
be produced slowly at a temperature of 133° to 135° F.
«To Give a Green Color to Gold Jewelry.»—Take verdigris, 120 parts,
by weight; sal ammoniac, 120 parts; nitrate of potassium, 45 parts;
sulphate of zinc, 16 parts. Grind the whole and mix with strong
vinegar. Place on the fire and boil in it the articles to be colored.
«Nickeling by Oxidation.»—I.—Nickeling may be performed on all metals
cold, by means of nickelene by the Mitressey process, without employing
electrical apparatus, and any desired thickness deposited. It is said
to be more solid than nickel.
First Bath.—Clean the objects and take 5 parts, by weight, of American
potash per 25 parts, by weight, of water. If the pieces are quite
rusted, take 2 parts, by weight, of chlorhydric acid per 1 part, by
weight, of water. The bath is employed cold.
Second Bath.—Put 250 parts, by weight, of sulphate of copper in 25,000
parts, by weight, of water. After dissolution add a few drops of
sulphuric acid, drop by drop, stirring the liquid with a wooden stick
until it becomes as clear as spring water.
Take out the pieces thus cleaned and place them in what is called the
copper bath, attaching to them leaves of zinc; they will assume a red
tint. Then pass them into the nickeling bath, which is thus composed:
By weight
Cream of tartar 20 parts
Sal ammoniac, in powder 10 parts
Kitchen salt 5 parts
Oxychlorhydrate of tin 20 parts
Sulphate of nickel, single 30 parts
Sulphate of nickel, double 50 parts
Remove the pieces from the bath in a few minutes and rub them with fine
sand on a moist rag. Brilliancy will thus be obtained. To improve the
appearance, apply a brass wire brush. The nickeling is said to be more
solid and beautiful than that obtained by the electrical method.
Brilliancy may be also imparted by means of a piece of buff glued on
a wooden wheel and smeared with English red stuff. This will give a
glazed appearance.
II.—Prepare a bath of neutral zinc chloride and a neutral solution
of a nickel salt. The objects are immersed in the bath with small
pieces of zinc and kept boiling for some time. This process has given
satisfactory results. It is easy to prepare the zinc chloride by
dissolving it in hydrochloric acid, as well as a saturated solution
of ammoniacal nickel sulphate in the proportion of two volumes of the
latter to one of the zinc chloride. The objects should be boiled for 15
minutes in the bath. Nickel salt may also be employed, preferably in
the state of chloride.
«Pickling Solutions.»—Oxidized copper, brass, and German silver
articles must be cleansed by acid solutions. In the case of brass
alloys, this process, through which the object acquires a dull yellow
surface, is known as dipping or yellowing. The treatment consists
of {583} several successive operations. The article is first boiled
in a lye composed of 1 part caustic soda and 10 parts water, or in
a solution of potash or soda or in limewater; small objects may be
placed in alcohol or benzine. When all the grease has been removed,
the article is well rinsed with water, and is then ready for the next
pickling. It is first plunged into a mixture of 1 part sulphuric acid
and 10 parts water, and allowed to remain in it till it acquires a
reddish tinge. It is then immersed in 40° Bé. nitric acid, for the
purpose of removing the red tinge, and then for a few seconds into
a bath of 1 part nitric acid, 1.25 parts sulphuric acid of 66° Bé.,
0.01 part common salt, and 0.02 parts lampblack. The article must then
be immediately and carefully washed with water till no trace of acid
remains. It is then ready for galvanizing or drying in bran or beech
sawdust. When articles united with soft solder are pickled in nitric
acid, the solder receives a gray-black color.
«Palladiumizing Watch Movements.»—Palladium is successfully employed
for coating parts of timepieces and other pieces of metals to preserve
them against oxidation. To prepare a palladium bath use the following
ingredients: Chloride of palladium, 10 parts, by weight; phosphate
of ammonia, 100 parts; phosphate of soda, 300 parts; benzoic acid, 8
parts; water, 2,000 parts.
«Metal Browning by Oxidation.»—The article ought first to be cleaned
with either nitric acid or muriatic acid, then immersed in an acid
affecting the metal and dried in a warm place. A light coating is thus
formed. For a second coating acetic or formic acid is used preferably
for aluminum, nickel, and copper; but for iron and steel, muriatic or
nitric acid. After cleaning, the article is placed in a solution of
tannin or gallic acid, and is then dried in a warm place as before.
The second coating is of a yellowish-brown color. On placing it near
the fire, the color can be deepened until it becomes completely black;
care must be taken to withdraw it when the desired shade is produced.
Instead of the acids employed for the first coating, ammonia may be
used.
«Silvering by Oxidation.»—The oxidizing of silver darkens it, and gives
an antique appearance that is highly prized.