GOLD BEATEBS' SKIX. 



GOLD BEATING. 



The general properties of the solutions of gold are, protosulphate of 

 iron preoipitates meullic gold from the chloride ; protoaitrato of mer- 

 cury givc * black precipitate, and so does the protocUoride of tin ; but 

 a mixture of UM proto- and per-chloride, as already noticed, given a 

 purple precipitate. Hydrosulphurio acid throws down black sulphuret 

 of gold ; ammonia, at already noticed, throws down a yellowish-brown 

 precipitate of "'rHiniHrg gold, which an excess of the alkali re-din- 

 solves. Many of the metaU, phosphorus, and charcoal, precipitate 

 metallic gold, as also do oxalic acid and tartrate of potash, when heated. 

 UOLD-BEATK1W SKIN. The preparation of the delicate mem- 

 brane known by this name forme part of ail exceedingly dirty and 

 dimgreeablei class of manufactures called by the French " boyauderie," 

 from the word "boyau," intestine. The strings for violins, turps, and 

 guitars [CATGUT STHINUH], gold-beaters' skin, and some other valuable 

 articles of a membranous character, are made from the intestines of 

 animals not (except in a few cases) from the whole thickness of the 

 intestine, but from a very thin membrane which covers it either on 

 the interior or the exterior. It is from the large intestine of the ox 

 that gold-beaters' skin is prepared. This intestine is composed of 

 three coats or sheathings ; the mucous membrane on the inside, the 

 peritoneal membrane on the outside, and the muscular membrane 

 between them. The peritoneal membrane is the one required for 

 the purpose. In the first place, the intestine is freed from all 

 greasiaess by soaking, scraping, and washing; it U then turned inside 

 out, and put into a tub. The tub contains a strong alkaline liquor, in 

 which the intestine is allowed to steep for several hours ; and at the 

 expiration of that time the mucous membrane has become so far 

 loosened as to be easily removed. The alkaline liquor employed, called 

 " eau-de- Javelle," removes all trace of fetid odour. The peritoneal 

 membrane is afterwards carefully removed, and stretched out to dry. 

 It is next steeped in a weak solution of potash, and carefully scraped. 

 After this it is stretched out on a frame, with that surface under- 

 most which had adhered to the muscular membrane ; another mem- 

 brane, placed the contrary way uppermost, is laid upon it, and the two 

 are easily made to unite firmly. The membrane is then moistened 

 successively with different liquids, of which one is a solution of alum, 

 one a solution of isinglass, and another a layer of white of egg. 

 Beating, drying, and pressing are also among the processes to which 

 the membrane is subjected ; each manufacturer appearing to have his 

 own peculiar mode of proceeding. 



A packet of skins properly prepared for gold-beating is rather a 

 costly piece of apparatus; but it will bear a surprising amount of 

 beating without injury. The skins may be used for several months 

 without become thinner or weaker. They acquire, however, by 

 degrees a greasinese of surface which temporarily unfits them for their 

 office ; this greasiness is removed by interleaving them with pieces of 

 clean white paper, and hammering them for a considerable time, 

 whereby the greasiness is removed from the skin to the paper. 



The unhealthiness of this manufacture lias been deemed in France 

 so serious as to engage the attention both of medical men and of 

 the legislature. H. Parent Duchatelet states that the odour arising 

 from the putrefactive fermentation of the substances used, is more 

 loathsome than any other process incident to manufactures ; and that 

 the effect of the exhalation on the health of the inhabitants who lived 

 near the boyauderies was such as to lead the French government, 

 towards the end of the last century, to prevent the boyaudiers from 

 continuing to carry on the manufacture in the faubourg where they 

 had congregated, and where a street was named after them, the Rue de 

 la Boyauderie. They left that spot, and established themselves near 

 Montfaucon ; but here they formed a new centre for disease and 

 infection. At length, in or about 1820, the Council of Health offered 

 a prize for the discovery of any mode for separating the peritoneal 

 membrane without subjecting the intestine to the putrefactive action. 

 M. Labarreriue obtained the prize, by showing how chlorine could be 

 employed )x>th to fumigate the workshops, and to loosen the mem- 

 branes one from another without allowing the offensive odour to escape. 

 In 1810 the different manufactories of France were ranged in classes 

 according to the unhcalthiness of the employment* ; and the boyauderies 

 were placed at the head of the list of " Etablissements Insalubres : " 

 they were subjected to rather strict regulations in relation to the 

 position and general arrangements of the buildings ; afld these rules 

 are still acted on in cases where the new method is not adopted. 



This manufacture is also carried on in England. Before the removal 

 of the cattle market from Smithfield to Pentonville, and the pulling 

 down of houses to form Victoria Street, most of the English v..ii.n> 

 in this disagreeable trade congregated in and near Cow Cross. A 

 or group of 800 pieces of gold-beaters' skin, is valued at no less than 

 lOt, for gold-beating purposes. 



GOLD BEATING. This is a process whereby gold is brought to 

 the state of very fine leaves, for use in various kinds of gilding. The 

 remarkable ductility of gold a quality possessed by it in a greater 

 degree than by any other known substance is here taken advantage 

 of to the fullest extent, as a means of limiting the quantity of this costly 

 material required in gilding. So far is the attenuation carried, that a 

 hundred square inches of nearly pure gold can be purchased for about 

 sixpence. 



It is by a combine*! process of rolling and hammering that the 

 attenuation of the gold is produced. The metal is melted in a small 



crucible by the heat of a wind furnace ; and is cast into an iron ingot- 

 mould, so as to form an oblong flat bar about three-quarters of an uu-h 

 in width, and weighing two ounces : a little borax is used to facilitate 

 the melting of the gold, and the ingot- mould is greased on the insida 

 to prevent the adhesion of the gold to it. The ingot, when removed 

 from the mould, is immersed in hot ashes, whereby the gold it both 

 annealed and freed from grease. When cold, it is ready to undergo 

 the process of reduction in thickness, and proportionate extension in 

 length and breadth. Formerly, in France, the ingot was beaten out to 

 the state of a thin riband, by the use of a forgiug-hammer about three 

 pounds weight ; but the French gold-beaters now carry this hammer- 

 ing only to such an extent as to reduce the ingot to the state of a 

 plate about one-sixth of an inch in thickness, and then finish by the 

 use of the rolling, flatting, or lnininiing mill. In England this 

 forging is dispensed with, and the reduction of the gold to the state of 

 a riband U effected by means of the mill. This mill consists of' two 

 rollers made of polished steel, perfectly cylindrical in form, and adjusted 

 with very great nicety ; it must so act as to reduce the gold equally in 

 every part, or else the further thinning could not be pro]wriy carried 

 on. The milling is continued until the ingot of two ounces U spread 

 out to a surface of 860 square inches, with a thickness of rather more 

 than 1-SOiiOi of an inch. 



This thin riband of gold is then consigned to the hands of the gold- 

 beater. The hammering does not take place on the gold itself ; but 

 thin membranes are interposed between the hammer and the gold. 

 These membranes are of three kinds : an outside covering of common 

 parchment ; a set of leaves made of very fine and smooth calf-skin 

 vellum ; and another set made of the gold-beaters' skin described in 

 the last article. The riband of gold is cut up into small pieces, each 

 measuring exactly an inch square ; and a hundred and fifty of these 

 are interleaved with an equal number of leaves of vellum, about four 

 inches square ; each piece of gold being placed on the middle of a leaf 

 of vellum. Over this packet of vellum-leaves is drawn a parchnit-nt 

 case, open at both ends ; and over this another parchment case at right 

 angles to the former ; so that the vellum and gold are enclosed i 

 on all sides. The entire packet thus prepared is beaten. This beating 

 is effected on a smooth block of marble; strongly imbedded be; 

 and bounded on three sides by a raised ledge of oak wood ; the front 

 edge is open, and has a leathern flap attached to it, which serves as a 

 kind of apron for catching fragments of gold that may fall off in the 

 subsequent operations. The hammers employed are very ponderous, 

 weighing about sixteen, twelve, and ten pounds respectively; the 

 heaviest is used first, and the others are brought into use as the gold 

 becomes thinner. 



The packet of interleaved vellum and gold is laid on the stone, and 

 the workman beats with regular and heavy blows, on the middle of 

 the upper side ; there is a spring or elasticity of the packet which 

 enables the hammer to rise easily after each blow ; otherwise the work 

 would be too laborious for any man continuously. The beater turns 

 the packet over from time to time, to equalise the action among the 

 leaves; and he occasionally bends the packet to and fro, to destroy any 

 slight adhesion between the gold and the vellum : he also 01 

 at intervals, to see how the operation is proceeding. The beating 

 is continued until each little inch-square piece of gold has 1 

 expanded nearly to the size of the vellum-leaves ; and in order that 

 the whole of the hundred and fifty pieces may be equally acted on, 

 the packet is occasionally opened, and the inner pieces placed near the 

 outside, to receive more action from the hammer. 



When this degree of attenuation has been reached, the use of the 

 vellum-leaves ceases, and that of the gold-beaters' skin commences. 

 The packet is opened, and each piece of gold, being taken out and 

 placed on a kind of cushion, is cut into four pieces with a peculiar 

 smooth-edged knife. 



The pieces of gold, now increased in number from a hundred and 

 fifty to six hundred, are interleaved with an equal number of pieces of 

 the prepared gold-beaters' skin. The packet thus prepared is en 

 in parchment, and beaten in the same way as before, but with a 

 smaller hammer. The pieces of gold become by degrees ex] 

 until they attain nearly the size of the skin-leaves. The pack i -I is 

 again opened, the leaves of gold are again cut into four each, and the 

 quarters are again interleaved with gold-beaters' skin. The cutting is, 

 in this second instance., effected by the smooth edge of a strip of cane, 

 since the thin gold would be liable to adhere to a steel knife. As the 

 pieces of gold, now two thousand four hundred in number, would l>o 

 too numerous to be beaten in one packet, they are divided into three 

 parcels of eight hundred each, and each packet is interleaved with 

 gold-beaters' skin, enveloped in parchment, and beaten in the same 

 way as before. A third time these leaves expand nearly to the size of 

 the skin-leaves ; and by this expansion the necessary degree of tl. 

 is attained. By the three beatings and the two quarterings, the gold 

 is expanded to an area nearly two In I greater than it 



presented when in the form of a riband. The attenuation may lie 

 rendered more intelligible by stating that one hundred square feet of 

 the leaf-gold weigli no more than an ounce a result nearly as 

 surprising as anything presented in the mechanical arts. Gold can I >c 

 beaten to a much greater degree of thinness than that ordinarily used; 

 but the waste occasioned by broken leaves, and the additional nicety 

 and labour required, more than counterbalance the advantage!. 



