Youngs Demonstrative Translation of Scientific Secrets | Page 4

the assistance of mercury with which the gold is amalgamated. The
mercury is evaporated while the gold is fixed by the application of heat,
the whole is then burnished of left mat in the whole or in part,
according as required.
15. GILDING GLASS AND PORCELAIN
Dissolve in boiling linseed oil an equal weight either of copal or amber,
and add as much oil of turpentine as will enable you to apply the
compound or size thus formed as thin as possible to the parts of the
glass intended to be gilt; the glass is to be placed in a stove till it is so
warm as almost to burn the fingers when handled. At this temperature
the size becomes adhesive, and a piece of leaf gold applied in the usual
way will immediately stick. Sweep off the superfluous portions of the
leaf, and when quite cold it may be burnished, taking care to interpose a
piece of india paper between the gold and the burnisher. It sometimes
happens when the varnish is not very good that by repeated washing the
gold wears off; on this account the practice of burning it in is
sometimes had recourse to; for this purpose some gold powder is

ground with borax, and in this state applied to the clean surface of the
glass by a camel hair pencil; when quite dry the glass is put into a stove,
heated to about the temperature of an annealing oven, the gum burns
off; and the borax, by vitrifying, cements the gold with great firmness
to the glass, after which it may be burnished.
The gilding upon porcelain is in like manner fixed by heat and the use
of borax, and this kind of ware, being neither transparent nor liable to
soften, and thus to be injured in its form in a low red heat, is free from
the risk and injury which the finer and more fusible kinds of glass are
apt to sustain from such treatment. Porcelain and other wares may be
platinized, silvered, tinned, or bronzed, in a similar manner.
16. GILDING THE EDGES OF PAPER
The edges of the leaves of books and letter paper are gilded whilst in a
horizontal position in the bookbinder's press or some arrangement of
the same nature, by first applying a composition formed of four parts of
Armenian-bole and one of candied sugar, ground together with water to
a proper consistence, and laid on by a brush with the white of an egg.
This coating, when nearly dry is smoothed by the burnisher, it is then
slightly moistened by a sponge dipped in clean water and squeezed in
the hand; the gold leaf is now taken up on a piece of cotton from the
leathern cushion and applied on the moistened surface; when dry it is to
be burnished by rubbing the burnisher over it repeatedly from end to
end, taking care not to wound the surface by the point.
17. PROFESSOR WORTS' AMALGAM FOR SILVERING
This is the only means yet discovered for silvering iron directly, yet it
is not so lasting as some of the other processes. Take quicksilver and
the metal potassium, equal parts by volume, put them together in a
tumbler, and if both metals be good there will be a brisk ebullition,
which continues until an amalgam of the two is formed, then add as
much quicksilver as there is of the amalgam; let it work till thoroughly
mixed, and it is ready for use. This amalgam you may apply with a
cloth to any metal, even iron, though it be a rusty bar, and you have it
neatly silvered over.
18. FOR COPPERING IRON
This is the latest method, and that now in use. To a solution of sulphate
of copper, add a solution of ferrocyanide of pottasium, so long as a
precipitate continues to be formed. This is allowed to settle, and the

clear liquor being decanted the vessel is filled with water, and when the
precipitate settles the liquor is again decanted, and continue to repeat
these washings until the sulphate of potash is washed quite out; this is
known by adding a little chloride of barium to a small quantity of the
washings, and when there is no white precipitate formed by the test, the
precipitate is sufficiently washed. A solution of cyanide of potassium is
now added to this precipitate until it is dissolved, during which process
the solution becomes warm by the chemical re-action which takes place.
The solution is filtered, and allowed to repose all night. If the solution
of cyanide of potassium that is used is strong, the greater portion of the
ferrocyanide of potassium crystalises in the solution, and may be
collected and preserved for use again. If the solution of cyanide of
potassium