4. (M. Gersdorff.) Copper, 50 parts; nickel and zinc, of each 25 parts.
Very white and malleable, and takes a high polish. Recommended as a
general substitute for silver.
5. (Gersdorff.) Copper, 60 parts; nickel and zinc, of each 20 parts. For
castings, as bells, candlesticks, &c.
6. (Gersdorff.) Copper, 60 parts; nickel, 25 parts; zinc, 20 parts. For
rolling and wire. Very tough and malleable.
7. (Sample made from the ore of Hilburghausen.) Copper, 40-1/2 parts;
nickel, 31-1/2 parts; iron, 2-1/2 parts; zinc, 25-1/2 parts. Equal to the
best Chinese sample.
8. (Pelouze.) Copper and nickel, equal parts. Recommended by M. Pelouze as
superior to any of the alloys containing zinc.
9. (Pelouze.) Copper, 2 parts; nickel, 1 part. Not so white as the last,
but more malleable.
10. (White Copper from China.)--_a._ Copper, 30 parts; nickel, 36 parts;
zinc, 34 parts.
_b._ (Said to be prepared from native ore.) Copper, 41 parts; nickel, 32
parts; iron, 2-1/2 parts; zinc, 24-1/2 parts. Silvery white, takes a high
polish, very sonorous, malleable both cold and at a dull-red heat, and may
be rolled into leaves or formed into wire.
11. (White metal spoon, sold as 'German Plate.') Copper, 55 parts; nickel,
24 parts; zinc, 16 parts; tin, 3 parts; iron, 2 parts.
_Anal._ This may be briefly described as follows:--_a._ 100 gr. of the
alloy is digested in nitric acid q. s., diluted with a little water. If
the sample is unequally attacked by the acid, and a white external shell
is observed which dissolves more slowly than the internal portion, it is
'plated' on those parts with silver. If this silver shell or casing has a
polished surface on both sides, the article has been 'electro-plated,' if
the contrary is the case, it has most probably been plated in the usual
way.
_b._ The solution being completed, heat is applied to expel the excess of
acid, and the remainder is largely diluted with distilled water; dilute
hydrochloric acid is now dropped in as long as it occasions a precipitate,
and the whole, after being moderately heated for a short time, and cooled,
is thrown upon a small paper filter; the precipitate on the filter is next
washed with distilled water, carefully dried, and ignited in a small
porcelain crucible, the filter itself being separately burnt on the cover
of the crucible, and the ashes added to its contents prior to ignition.
Every 143-1/2 gr. of the resulting fused chloride is equal to 108 gr. of
metallic silver.
_c._ The filtered liquid (see _b_) is next treated with a stream of
sulphuretted hydrogen, and the black precipitate is collected, washed, and
digested in strong nitric acid; when the solution is complete sulphuric
acid is dropped in to precipitate the lead (if any is present); if a
precipitate is formed, the whole is evaporated to dryness, and the excess
of sulphuric acid expelled by a rather strong heat applied towards the
end; the dry mass is now collected on a filter, washed with a mixture of
water and alcohol, dried, and exposed to slight ignition in a porcelain
crucible. Every 152 gr. of the resulting dry sulphate is equal to 104 gr.
of lead.
_d._ The liquor filtered from the sulphate of lead, or (in its absence)
the nitric solution of the precipitate produced by the sulphuretted
hydrogen (see _c_), is next treated with potassa, &c., as described under
the analysis of brass. Every 40 gr. of the dry protoxide thus obtained
represents 32 gr. of pure copper.
_e._ The liquor which was filtered from the precipitate produced by the
sulphuretted hydrogen (see _c_) is boiled until it loses its offensive
odour, and is then precipitated with carbonate of soda, in slight excess,
and again boiled for a few minutes; the precipitate (mixed oxides of
nickel and zinc) is collected, washed, and redissolved in dilute acetic or
nitric acid, in excess; a current of sulphuretted hydrogen is next passed
through the solution, the precipitate collected on a filter, washed,
redissolved in hydrochloric acid, and the solution again treated with
carbonate of soda; the last precipitate (oxide of zinc) is washed, dried,
and gently ignited. Every 40 gr. of this oxide is equivalent to 32 gr. of
metallic zinc.
_f._ The washings of the precipitated oxides and the liquid filtered from
the precipitate occasioned by the sulphuretted hydrogen (see _e_) are
mixed together, pure solution of ammonia added in considerable excess, and
the mixture agitated for some time; the undissolved portion of the
precipitate is then collected on a filter, washed with distilled water,
redissolved in dilute nitric acid, again precipitated with solution of
potassa, and this last precipitate (ferric oxide) washed, dried, ignited,
and weighed. Every 80 gr. represents 50 gr. of metallic iron.
_g._ The ammoniacal solution filtered from the precipitate of sesquioxide
of iron (see _f_) is precipitated with pure solution of potassa, boiled
for a few minutes, and, when cold, thrown on a filter; the precipitate is,
lastly, washed with hot water, dried, ignited, and weighed. Every 37-1/2
gr. of the oxide thus obtained is equal to 29-1/2 gr. of metallic nickel.
_Obs._ The manufacture of nickel or German silver has of late acquired an
importance which is second only to that of silver plate itself. The
superior quality of this alloy, and the graceful patterns which it is
often made to assume in the hands of the accomplished artist cannot fail
to have attracted the admiration of the majority of our readers. The value
of correct information regarding the preparation of this alloy, and of a
ready method of determining the composition of the most improved
commercial samples will, therefore, be fully appreciated by every
metallurgist who wishes to throw his wares into the arena of public
competition. Much that is vended under the name of GERMAN SILVER is little
better than the BRITANNIA METAL or PLATE PEWTER formerly so plentiful in
every establishment in this country. German silver has quite superseded
copper as the basis of 'electro-plated goods.'[332]
[Footnote 332: See ELECTROTYPE.]
The union of the metals in the above formulæ is effected by heat with the
usual precautions. When iron is ordered, it is generally added under the
form of 'tin plate.' See ALLOY, BRASS, BRITANNIA METAL, BRONZE, &c.
=GER'MAN TIN'DER.= See AMADOU.
=GERMINA'TION.= The growth or vegetation of a seed by which a young plant
is produced. The conditions essential to germination are the presence of
warmth, air, and moisture. The most favorable temperature is between 60°
and 85° Fahr., according to the habitat of the respective plants. Below
40° Fahr. most of the more perfect seeds either refuse to vegetate, or
vegetate slowly and feebly; and at or near the freezing-point none of them
undergo this change. At a temperature above 100° Fahr. the young germ is
usually injured, and at about 125°, if it forms, it soon withers and dies.
See MALTING, SEED, &c.
=GERMS.= The 'germ theory of disease' may be briefly stated to be that
which supposes the cause of epidemic and contagious maladies to be due to
the agency of specific, inconceivably small germs,--different germs giving
rise to different diseases.
These disease germs gaining an entrance by means of air, water, or food
into the healthy body, and being possessed of extraordinary powers of
increase and subdivision, are supposed to set up the particular disease,
and at the same time to multiply to an incredible extent by feeding upon
the tissues best suited for their support. Further, they are conceived to
be thrown off into the atmosphere from the body of the patient, whence
they are conveyed as before described into other healthy animal organism,
in which, comporting themselves as in the previous case, they set up a
similar disease. See BACTERIA AS ORIGINATORS OF DISEASE.
=GHEE.= A sort of butter used by the natives of India. _Prep._ Milk is
boiled in large earthen pots for an hour or two, then allowed to cool, a
little curdled milk called 'dhye' being added, in order to make the whole
coagulate. After a lapse of some hours the contents of each to the depth
of 5 or 6 inches are removed and placed in a larger earthenware utensil,
in which they are churned by means of a piece of split bamboo for about
half an hour; then hot water is poured in, and the churning continued for
half an hour longer, after which time the butter is found to be formed.
When this becomes rancid, it is melted in an earthen vessel, and boiled
until all the water has evaporated; after which a little salt or
betel-leaf is put into it, and finally it is poured off into suitable
vessels in which it can be preserved from the air. Bottles are commonly
used for this purpose. See BUTTER.
=GHER'KINS.= _Syn._ GIR'KINS. Small cucumbers adapted for pickling. See
PICKLES.
=GILD'ING.= _Syn._ DORURE, Fr. The art or process of covering the surfaces
of bodies with a thin film of gold, for the purpose of increasing their
durability or improving their appearance. For the sake of brevity we shall
briefly notice the leading varieties of gilding, and their applications,
in alphabetical order.
GILDING, BURNISHED. This is distemper gilding to which a 'face' has been
given with the 'burnisher.' It is chiefly employed for the polished
portions of the frames of pictures and mirrors, the more prominent parts
of statuettes, &c.
GILDING, CHEMICAL. Those varieties in which the film of gold is formed on
the surface through the agency of chemical affinity, in opposition to
mechanical gilding, in which the gold is made to adhere by the
intervention of some glutinous substance.
GILDING, COLD. The articles (copper or brass) to be gilded, after being
softened, annealed, and polished in the usual manner, are rubbed with a
little gilding powder by means of a piece of cork moistened with a
solution of salt in water; after which the work is burnished with a piece
of hematite or polished steel. (See _below_.)
GILDING, DISTEMPER. This is applied to wood, plaster, marble, &c. It is
commonly performed in this country by giving the wood, first, a coating of
good size, and next, several successive coats of size thickened with
finely powdered whiting, Spanish white, or plaster of Paris until a good
face is produced; observing to let each coat become quite dry, and to rub
it perfectly smooth with fine glass paper, before the application of the
following one. When the proper 'face' is obtained, the surface is thinly
and evenly gone over with gold size, and when this is nearly dry, the gold
leaf is applied, and afterwards burnished with an agate or dog's tooth.
The process, as adopted by the Parisian artists, who greatly excel in this
species of gilding, is very complicated, and is divided into at least 17
distinct operations, each of which they declare to be essential to its
excellence.
GILDING, ELECTRO-. See ELECTROTYPE.
GILDING, GRECIAN. In this variety sal-ammoniac and corrosive sublimate,
equal parts, are dissolved in nitric acid, and a solution of gold made
with this menstruum; after slight concentration the liquid is applied to
the surface of silver, which immediately becomes black, but on being
heated exhibits a rich gilded surface.
GILDING, JAPANNER'S. The surface is covered with oil size thinned with
spirits of turpentine, and gold, in powder, is gently dabbed on with a
puff of wash leather. This gives the appearance of 'frosted gold.' A
coating of varnish is next given, followed by exposure to a gentle heat in
the 'stove.'
GILDING, LEAF. This term is commonly applied to the gilding of paper,
vellum, &c., by applying leaf gold to the surface, previously prepared
with a coating of gum water, size, or white of egg. It is usually
burnished with an agate or dog's tooth.
GILDING, MECHANICAL. See CHEMICAL GILDING (_above_).
GILDING, MERCURIAL. See WASH GILDING (_below_).
GILDING, OIL. This species of gilding may be divided into several
operations. The following are the abridged instructions of a Parisian
artist on the subject:--1. The surface is prepared by a coating of white
lead in drying oil.--2. Another coat is given, made with calcined white
lead or massicot, ground in linseed oil and turpentine. 3 or 4 coats of
this mixture are often given, at intervals of at least 23 hours, observing
to carefully smooth off each coat with pumice stone or shave grass before
the application of the following ones.--3. The 'Gold Colour,' or paint, is
next applied. It is usually very adhesive gold size, or the bottom of the
pot or dish in which painters wash their brushes. For this purpose it is
thoroughly ground and strained.--4. When the gold colour becomes partially
dry and sufficiently tenacious, the gold leaf is applied, and pressed on
with a wad of cotton-wool or a soft brush. It is now left for several days
to harden.--5. A coat of spirit varnish is next given, and the object is
cautiously passed over a chafing-dish of charcoal, observing to avoid
stopping the motion of the piece whilst doing so, as the work would then
become discoloured and blistered.--6. The work is 'finished off' with pale
oil varnish. For out-door gilding and common work the varnishing process
is generally omitted. This species of gilding is applied to woodwork,
plaster, metal, &c.
GILDING, VARNISH. This is a mere variety of oil gilding, applied to
equipages, furniture, mirror and picture frames, &c., the surface being
highly varnished and polished before it receives the size or gold colour;
and after the gilding has become quite dry, a coat of spirit varnish,
fumed with the chafing dish as above, is applied, followed by 2, 3, or
more coats of the best copal varnish, at intervals of 3 or 4 days each.
The whole is, lastly, carefully polished with tripoli and water.
GILDING, WASH, AMALGAM G., MERCURIAL G., WATER G. This consists in the
application of a thin coating of amalgam of gold to the metallic surface
(brass, bronze, or copper) to be gilded, and the subsequent volatilisation
of the mercury by heat. It is the usual method of gilding articles of
copper and its alloys, and possesses great beauty and durability when
skilfully executed. The occupation is, however, an unhealthy one, owing to
the continual exposure of the workman to the fumes of mercury. The furnace
invented by M. D'Arcet obviates this evil, as the whole of the volatilised
mercury is carried off, and again condensed for further use. It should,
therefore, be adopted by every water-gilder who studies economy and the
health of those in his employ.
The process of water gilding consists in several distinct operations, and
can only be successfully performed by those who have been schooled in the
art by an apprenticeship to the trade. It would, therefore, be waste of
space to enter into details here. Formulæ for several of the articles
employed for the purpose will be found in the alphabetical places in this
work.
GILDING, WATER. See _above_.
Among the applications of the process of gilding that deserve a separate
notice are the following:--
The gold letters and figures on the covers of BOOKS are thus formed:--Gum
mastic, in fine powder, is dusted over the surface to be gilded; an iron
or brass tool bearing the design upon its face is then heated to a proper
temperature, and gently pressed upon a piece of leaf gold, which slightly
adheres to it; the two are then transferred to the cover, and the tool is
gently pressed on it, by which means the mastic softens and retains the
gold. The loose gold and powdered mastic are then dusted off with a brush.
Gold leaf will adhere to leather without the use of mastic, but not so
firmly as when it is employed.
The edges of the leaves of books and paper are first cut perfectly smooth,
and then washed over with a solution of isinglass in weak spirit, or with
a varnish made of Armenian bole, 4 parts, and powdered sugar-candy, 1
part, mixed up to a proper consistence with strained white of egg. The
coating is allowed to dry, and is then smoothed with a wet rag, after
which the gold leaf is applied and polished with the burnisher.
BRASS BUTTONS, formerly so much in demand, are covered by a rough species
of wash gilding. The buttons are polished in the lathe and thrown into a
pan with a little amalgam of gold, and as much aquafortis diluted with
water as will wet them all over. Here they are well stirred up, until they
assume a silvery appearance, when they are washed with clean water. They
are then submitted to a sufficient heat in a suitable apparatus, until the
mercury is volatilised. The buttons are next cooled, and well tossed and
rubbed about with a painter's brush; and are, lastly, burnished by washing
them well with beer or ale grounds.
Twelve dozen (1 gross) of buttons, of 1 inch in diameter, may be perfectly
gilded on both sides with only 5 gr. of gold. By an Act of Parliament,
which is still unrepealed, this is the smallest quantity of gold permitted
to be used for a gross of buttons of the above size.
GLASS, PORCELAIN, and EARTHENWARE, are gilded by blending powdered gold
with gum-water and a little borax, and applying the mixture by means of a
camel-hair pencil; the article is then heated in an oven or furnace, by
which means the gum is burnt, and the borax, vitrifying, cements the gold
to the surface. It is afterwards polished with a burnisher. Names, dates,
or any fancy device, may thus be permanently and easily fixed on glass,
china, earthenware, &c.
JAPANNED WORK is gilded by the method explained as 'Japanner's gilding'
(_above_).
LEATHER is gilded in the same way as the covers of books. (See _above_.)
For common work, silver leaf, or even tin foil, is applied to the surface,
previously covered with size or white of egg, and after being burnished
down and dried, is washed over with gold-coloured lacquer.
The LETTERS of sign-boards and the ornamental gilding for out-door work
are done by first covering the design with yellow paint, then with oil
gold-size, and when this is nearly dry applying the leaf gold, observing
to shield it properly from the wind, lest it be blown away or become
crumpled before being properly attached. The work is, lastly, varnished.
POLISHED METALS may be gilded by one or other of the methods already
noticed. Articles in silver, copper, brass, and bronze, are usually coated
by the process of wash or water gilding; or, directly, by the application
of gold leaf, as follows:--The piece or article is heated to a bluish
tint, and gold leaf pressed gently and carefully on it with the burnisher;
heat is again applied, and the process repeated with fresh leaves of gold
until the gilding has acquired the proper thickness and tone. The surface
is lastly polished with the burnisher, or is coloured in the usual manner
at the stove. This succeeds with iron, steel, silver, copper and its
alloys, &c. Another method for polished articles in iron and steel, which,
however, is less durable than the preceding, is to apply an ethereal
solution of gold to the surface with a camel-hair pencil. The ether flies
off and leaves the surface coated with gold, which is then polished as
before. In this way, any fancy device or writing may be executed on steel
or iron with extreme facility.
SILKS, SATINS, WOOLLENS, IVORY, BONE, &c., may be readily gilded by
immersing them in a solution of neutral terchloride of gold (1 of the
salt, and 3 to 6 of water), and then exposing them to the action of
hydrogen gas. The latter part of the process may readily be performed by
pouring some dilute sulphuric acid on zinc or iron filings, in a
wide-mouthed bottle, and placing it under a jar or similar vessel,
inverted, at the top of which the articles to be gilded are suspended.
Flowers or other ornamental designs may be produced by painting them on
the surface with a camel-hair pencil dipped in the solution. The design,
after a few minutes' exposure to the hydrogen, shines with all the
splendour of the purest gold, and will not tarnish on exposure to the air,
or in washing.
GILDED THREAD or GOLD THREAD is merely a thread of yellow silk covered
with a very thin flatted wire of gold, by means of a revolving wheel.
WIRE (copper, silver, or brass) is occasionally gilded, in coils, by a
similar process to that adopted for BUTTONS; but more frequently as
follows:--Rods (usually of silver) are covered with gold foil of a
thickness proportionate to the quality of the intended wire, and the
compound bar is then drawn into wire, in the usual way. 100 gr. of gold
was formerly the lowest legal quantity that could be employed for 1 lb. of
silver.
_Patents._ Among the varieties of chemical gilding may be mentioned
1. (Elkington's patent--GERMAN GILDING, Bonnet's GILDING PROCESS.) The
articles to be gilded, after being perfectly cleaned from scale or grease,
and receiving a proper 'face,' are suspended, by means of wires, in the
gilding liquid (boiling hot), and moved about therein for a period varying
from a few seconds to a minute, or longer; the precise time required
depending on the newness and strength of the liquid. When sufficiently
gilded, the articles are withdrawn from the 'solution of gold,' washed in
clean water, and dried; after which they undergo the usual operation of
'colouring,' &c. A dead gold appearance is produced by the application to
the articles of a weak solution of nitrate of mercury previously to the
immersion in the gilding liquor; or the deadening may be given by applying
a solution of the nitrate to the newly gilded surface, and then expelling
the mercury by heat.
The gilding liquor.--Take of fine gold, 5 oz. (troy); nitro-muriatic acid,
52 oz. (avoirdupois); dissolve by heat, and continue the heat until red or
yellow vapours cease to be evolved; decant the clear liquid into a
suitable vessel; add of distilled water, 4 galls.; pure bicarbonate of
potassa, 20 lbs.; and boil for 2 hours. The nitro-muriatic acid is made
with pure nitric acid (sp. gr. 1·45), 21 oz.; pure muriatic acid (sp. gr.
1·15), 17 oz.; and distilled water, 14 oz.
This process, though patented by Mr Elkington in England, was in reality
discovered and first practised by M. Bonnet, a foreigner. Articles thus
gilded do not bear friction and the operations of being put in colour
(_mise en couleur_) so well as those gilded by the mercurial process, or
by the methods of cold or leaf gilding as applied to polished metals.
2. (Talbot's patent.) By this process polished metallic articles are
gilded by simple immersion in a solution of gallic acid in water, ether,
or alcohol, to which a solution of gold has been previously added.
SILVERING and PLATINISING may be effected in the same manner, by using a
solution of either of these metals instead of one of gold.
[asterism] These and other chemical processes have been almost completely
superseded by the certain and economical process of ELECTRO-GILDING. See
ELECTROTYPE.
=Gilding Amalgam.= See AMALGAM.
=Gilding Liquor.= This name has been given to various solutions of gold,
and to other liquids employed in gilding. The former are noticed
elsewhere. Among the latter are the following:
DEADING AQUAFORTIS. From mercury, 1 part; aquafortis (sp. gr. 1·33), 3
parts; dissolve, and add of soft water, 7 parts. Used to produce a
dead-gold effect. It is applied (diluted) to the articles, before
spreading the amalgam over them, in water gilding; or before placing them
in the 'gilding liquor,' in the chemical processes.
MERCURIAL SOLUTION. From mercury, 10 parts, dissolved in aquafortis (sp.
gr. 1·33), 11 parts, and the solution diluted with 25 times its weight of
water. Used to moisten the scratch brush before drawing it over the
amalgam, in mercurial gilding; also to deaden the gilded surface, by
moistening the latter with it, and then exposing the piece to a heat
sufficiently high to drive off the mercury.
GILDER'S PICKLE. From alum and common salt, of each 1 oz.; nitre, 2 oz.;
dissolved in water, 1/2 pint. Used to impart a rich colour to gold
surfaces, especially of trinkets. Its application should not be too long
continued, as it dissolves a small portion of the gold. For common
purposes it is best used largely diluted with water.
VERMEIL, VERMEIL COATING, OR-MOLU C. From annotta and salt of tartar, of
each 1 oz.; dragon's blood, 1/2 oz.; water, 1 quart; simmer down to about
one fourth, add saffron, 20 gr., and when merely tepid, strain through
fine muslin into a bottle. Used to give lustre and fire to distemper
gilding. A little is floated over the surface with a very soft, flat,
camel-hair brush.
=Gilding Metal.= The metal employed as a base for gilding is usually
brass, or a mixture of brass and copper. The following proportions have
been recommended:--
1. Copper, 6 parts; brass, 1 part.
2. Copper, 4 parts; Bristol brass, 1 part.
3. Copper, 13 parts; old Bristol brass, 3 parts; tin, 14 parts.
=Gilding Powder.= _Prep._ 1. Pure gold, 5 dr.; pure copper, 1 dr.; aqua
regia, 10 oz.; dissolve, moisten clean linen rags with the solution, dry
them, and burn them to ashes. The latter contain the gold in a state of
minute division, and must be carefully collected.
2. Grain gold, 1 dr.; rose copper, 15 gr.; aqua regia, 2 fl. oz.; proceed
as last. Used in 'Gold Gilding.'