For the purpose of gilding very thin leaves of gold are required,
so thin, that although gold is expensive, yet gilded articles (as
picture-frames) are very far from being so. To produce this gold-leaf
is the business of the gold-beater. He first obtains the gold in a
state of purity from the refiner, in the form of small grains, which,
mixed with a small quantity of borax and alloy, are put into an
earthen pot called a crucible (coated beforehand with clay to keep
it from cracking), and then placed in a furnace which is raised to
a white heat. The gold, when melted, is poured into an iron mould
made warm and greased in the inside; this when cold forms an “ingot,”
which weighs two ounces, and is three-quarters of an inch square
and not quite half-an-inch thick. This ingot is now sent to the
“flattening mills,” where it is passed between sets of steel rollers
until it is rolled out into a sort of riband an inch wide and about
twelve feet long (at this degree of thinness a square inch will weigh
six-and-a-half grains). It is now cut into 150 pieces, each an inch
square, which are packed between pieces of vellum, four inches each
way, and surrounded by a sort of bag of the same material, the whole
being then subjected to the blows of a heavy iron hammer (weighing
about fourteen pounds) upon a block of solid stone, till the plates
of gold are beaten out nearly as large as the vellum, when they are
taken out and each cut into four pieces. These quarters are treated
as before, using gold-beater’s “skin” instead of vellum (this skin
is prepared from the intestines of the ox, and a set of these,
consisting of several hundreds, is called a “mould”), and the gold
again extended under the hammer to the size of the mould. The process
is repeated in the same manner a third time, after which the leaves
of gold are taken out, cut square on a cushion of leather, lifted
carefully by means of a sort of tongs made of wood, and placed in
the book. They are now between 600 and 700 times thinner than before
the beating commenced, and it would take about 280,000 of these
leaves to make the thickness of an inch. The leaves are from three
to three-and-a-half inches square, and are packed in books of paper
having the surface of the leaves rubbed with red chalk, to prevent
them from adhering to the gold; each book contains twenty-five leaves
of gold.
The different colors of gold-leaf, such as “pale gold,” “deep gold,”
or “red gold,” are produced by a small alloy of copper or silver,
the former giving a deeper and the latter a paler tinge to the pure
gold. A certain amount of alloy is always mixed with the pure metal,
otherwise it would adhere to the mould, and would not work so well.