SKIN. A delicate mem brane prepared from the large intestine of the ox, and used as the fabric for court-plaster, etc., but chiefly by gold-beaters. The outer or peritoneal membrane is used for this purpose. The intestine is first subjected to a partial putrefaction, by which the adhesion of the membranes is suffi ciently diminished to enable them to be sepa rated; the separated membrane is then further cleaned from adhering muscular fibres, dried, beaten, and pressed between paper, besides being treated with alum, isinglass, and white of egg, the object of which is to obtain the pure con tinuous membrane free from grease and impuri ties, and thus prevent weakening by putrefactive przicesses. When thus prepared, gold-beater's skin may be beaten continuously for several months with a. twelve-pound hammer without material injury. The intestines of 500 oxen are required to furnish the 900 leaves that form one packet, or mold, as it is technically called. The manufac ture is extremely offensive. Chlorine has been introduced both as a disinfectant and to assist in the separation of the membrane.
The process by which gold is hammered into thin leaves. The use of gold leaf for gilding is a very ancient art, having been practiced by the Egyptians and Greeks many centuries before the Christian Era, and gold used for this purpose is usually alloyed with silver or copper, according to the color re quired. The consumption of gold leaf by dentists is also general, as the material in this form is extensively used for fillings. As gold leaf is not sold by weight, but by superficial measure, and as increasing the quantity of alloy diminishes the malleability, there is but little temptation to use the baser metals as an adulteration. The gold is first cast into oblong ingots about three fourths of an inch wide, and weighing two ounces. The ingot is flattened out into a ribbon of about of an inch in thickness by passing it be tween polished steel rollers. This is annealed or
softened by heat, and then cut into pieces one inch square; 150 of these are placed between leaves of vellum or tough paper, each piece of gold in the centre of a square leaf, another placed above, and so on till the pile of 150 is formed. This pile, called a cutch, is inclosed in a double parchment case, placed upon a marble block, and beaten with a 16-pound hammer. The elasticity of the packet considerably lightens the labor of beating, by causing the hammer to rebound with each blow.
The beating is continued until the inch pieces are spread out to four-inch squares; they are then taken out and cut into four pieces. The squares thus produced are now placed between gold-beater's skin instead of vellum, made into piles, and inclosed in a parchment case, and beaten as before, but with a light hammer. An other quartering and beating produces 2400 leaves, having an area of about 190 times that of the ribbon, or a thickness of about of an inch. An ounce of gold is thus extended to a surface of about 100 square feet. A still greater degree of thinness may be obtained, but not profitably. A thinness has been attained of 367,500 leaves to the square inch, and a grain of gold is thus made to cover 52 square inches. After the last beating, the leaves are taken up with wooden pincers, placed on a cushion, blown out flat, and their ragged edges cut away, by which they are reduced to squares of three and one-quarter inches. Twenty-five of these are placed between the leaves of a paper-book, previously rubbed with red chalk to prevent adhesion of the gold, and are sold in this form. Attempts have been made to apply machinery to gold-beat ing, hut its application is very limited; and most of the gold leaf is still beaten by hand.