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GOLDBEATING

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Originally appearing in Volume V12, Page 202 of the 1911 Encyclopedia Britannica.
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GOLDBEATING .—The See also:

art of goldbeating is of See also:great antiquity, being referred to by See also:Homer; and See also:Pliny (N.H. 33. 19) states that 1 oz. of See also:gold was extended to 750 leaves, each See also:leaf being four fingers (about 3 in.) square; such a leaf is three times as thick as the See also:ordinary leaf gold of the See also:present See also:time. In all See also:probability the art originated among the Eastern nations, where the working of gold and the use of gold ornaments have been distinguishing characteristics from the most remote periods. On See also:Egyptian See also:mummy cases specimens of See also:original leaf-See also:gilding are met with, where the gold is so thin that it resembles See also:modern gilding (q.v.). The minimum thickness to which gold can be beaten is not known with certainty. According to See also:Mersenne (1621) I oz. was spread out over 105 sq. ft.; See also:Reaumur (1711) obtained 1462 sq. ft.; other values are 189 sq. ft. and 300 sq. ft. Its malleability is greatly diminished by the presence of other metals, even in very See also:minute quantity. In practice the See also:average degree of tenuity to which the gold is reduced is not nearly so great as the last example quoted above. A " See also:book of gold " containing 25 leaves measuring each 34 in., equal to an See also:area of 264 sq. in., generally weighs from 4 to 5 grains. The gold used by the goldbeater is variously alloyed, according to the See also:colour required. See also:Fine gold is commonly supposed to be incapable of being reduced to thin leaves.

This, however, is not the See also:

case, although its use for ordinary purposes is undesirable on See also:account of its greater cost. It also adheres on one See also:part of a leaf touching another, thus causing a See also:waste of labour by the leaves being spoiled; 'but for See also:work exposed to the See also:weather it is much preferable, as it is more durable, and does not tarnish or See also:change colour. The See also:external gilding on many public buildings, e.g. the See also:Albert Memorial in See also:Kensington Gardens, See also:London, is done with pure gold. The following is a See also:list of the See also:principal classes of leaf recognized and ordinarily prepared by See also:British beaters, with the proportions of alloy per oz. they contain. Name of Leaf. Proportion Proportion Proportion of Gold. of See also:Silver. of See also:Copper. Grains. Grains. Grains. Red . . . . 456-460 ..

20-24 See also:

Pale red . 464 .. 16 Extra deep 456. 12 12 Deep 444 24 12 Citron 440 30 10 Yellow . . 408 72 Pale yellow . 384 96 See also:Lemon . . 36o 120 See also:Green or pale . 312 168 . . See also:White 240 240 The See also:process of goldbeating is as follows: The gold, having been alloyed according to the colour desired, is melted in a crucible at a higher temperature than is simply necessary to fuse it, as its malleability is improved by exposure to a greater See also:heat; sudden cooling does not interfere with its malleability, gold differing in this respect from some other metals. It is then See also:cast into an See also:ingot, and flattened, by See also:rolling between a pair of powerful smooth See also:steel rollers, into a ribbon of 11 in. wide and 10 ft. in length to the oz. After being flattened it is annealed and cut into pieces of about 62 grs. each, or about 75 per oz., and placed between the leaves of a " See also:cutch," which is about a in. thick and 32 in. square, containing about 180 leaves of a tough See also:paper. Formerly fine vellum was used for this purpose, and generally still it is interleaved in the proportion of about one of vellum to six of paper.

The cutch is beaten on for about 20 minutes with a 17-lb See also:

hammer, which rebounds by the See also:elasticity of the skin, and saves the labour of lifting, by which the gold is spread to the See also:size of the cutch; each leaf is then taken out, and cut into four feces, and put between the skins of a " shoder," 42 in. square and in. thick, containing about 720 skins, which have been worn out in the See also:finishing or " See also:mould " process. The shoder requires about two See also:hours' beating upon with a 9-lb hammer. As the gold will spread unequally, the shoder is beaten upon after the larger leaves have reached the edges. The effect of this is that the margins oflarger leaves come out of the edges in a See also:state of dust. This allows time for the smaller leaves to reach the full size of the shoder, thus producing a See also:general evenness of size in the leaves. Each leaf is again cut into four pieces, and placed between the leaves of a " mould,' composed of about 95o of the finest gold-beaters' skins, 5 in. square and a in. thick, the contents of one shoder filling three moulds. The material has now reached the last and most difficult See also:stage of the process; and on the fineness of the skin and See also:judgment of the work-See also:man the perfection and thinness of the leaf of gold depend. During the first See also:hour the hammer is allowed to fall principally upon the centre of the mould. This causes gaping cracks upon the edges of the leaves, the sides of which readily coalesce and unite without leaving any trace of the See also:union after being beaten upon. At the second hour, when the gold is about the 15o,000th part of an See also:inch in thickness, it for the first time permits the transmission of the rays of See also:light. Pure gold, or gold but slightly alloyed, transmits green rays; gold highly alloyed with silver transmits pale See also:violet rays. The mould requires in all about four hours' beating with a 7-lb hammer, when the ordinary thinness for the gold leaf of See also:commerce will be reached.

A single See also:

ounce of gold will at this stage be extended to 75 X4 X4 =1200 leaves, which will See also:trim to squares of about 3; in. each. The finished leaf is then taken out of the mould, and the rough edges are trimmed off by slips of the ratan fixed in parallel grooves of an See also:instrument called a waggon, the leaf being laid upon a leathern See also:cushion. The leaves thus prepared are placed into " books " capable of holding 25 leaves each, which have been rubbed over with red ochre to prevent the gold clinging to the paper. Dentist gold is gold leaf carried no farther than the cutch stage, and should be perfectly pure gold. By the above process also silver is beaten, but not so thin, the inferior value of the See also:metal not rendering it commercially desirable to bestow so much labour upon it. Copper, See also:tin, See also:zinc, See also:palladium, See also:lead, See also:cadmium, See also:platinum and See also:aluminium can be beaten into thin leaves, but not to the same extent as gold or silver. The fine membrane called goldbeater's skin, used for making up the shoder and mould, is the See also:outer coat of the caecum or See also:blind gut of the ox. It is stripped off in lengths about 25 or 30 in., and freed from See also:fat by dipping in a See also:solution of See also:caustic See also:alkali and scraping with a See also:blunt See also:knife. It is afterwards stretched on a See also:frame; two membranes are glued together, treated with a solution of aromatic substances or camphor in See also:isinglass, and subsequently coated with white of See also:egg. Finally they are cut into squares of 5 or 52 in.; and to make up a mould of 95o pieces the gut of about 38o oxen is required, about 22 skins being got from each See also:animal. A skin will endure about 200 beatings in the mould, after which it is See also:fit for use in the shoder alone. The dryness of the cutch, shoder and mould is a See also:matter of extreme delicacy.

They require to be hot-pressed every time they are used, although they may be used daily, to remove the moisture which they acquire from the See also:

atmosphere, except in extremely frosty weather, when they acquire so little moisture that a difficulty arises from their over-dryness, whereby the brilliancy of the gold is diminished, and it spreads very slowly under the hammer. On the contrary, if the cutch or shoder be See also:damp, the gold will become pierced with innumerable microscopic holes; and in the moulds in its more attenuated state it will become reduced to a pulverulent state. This See also:condition is more readily produced in alloyed See also:golds than in fine gold. It is necessary that each skin of the mould should be rubbed over with calcined See also:gypsum each time the mould may be used, in See also:order to pre-vent the See also:adhesion of the gold to the See also:surface of the skin in beating.

End of Article: GOLDBEATING

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