TACHARD1A 



ARSENIC AND RB8IN A hi U.I > I.AI-CA 



now enters the trough an. I. while holding on to a traiuveru bar placed at 

 a convenient position, treads with the bare feet on th* granular lac and 

 presses it against the tides of the trough. As a result the lae is broken 

 into still liner parti.!,-* and the water becomes of a deep claret colour. 

 The coloured water IK run off, a fresh washing given, and repeated till the 

 washings pass off colourless. The washic ..- so desired, are evapo- 



rated down to a thick consistence and compro- I'iiis is lac- 



dye. The resin is now called uxuhed-teed-lac . hut it is sifted into two 

 cnmlities granular and dust ; the hitter is called gaud. When steam 

 machinery is used, the washing is done with revolving cylinders and 

 beaters. 



In some parts of India the seed-lac is now either washed or even boiled 

 in a solution of crude carbonate of soda or of soda and borax, or of crude 

 carbonate of potash, or of borax alone or of alum. After several snob 

 washings it is said to become almost white. Hut in most of the larger 

 factories, especially those concerned in the production of shell-lac, the 

 washing or boiling in alkaline preparations is dispensed with ; the seed-lac 

 is simply repeatedly washed in pure water but not bleached. Indeed, 

 according to some authorities, it is even maintained that bleaching weakens 

 the lac. After being washed, or bleached and washed, to the desired 

 extent, the seed-lac is spread out on special floors and exposed to liuht 

 and air, by which it is thoroughly dried and still further bleached. 



According to the purpose for which intended, the dried washed lac is Addition at 

 now mixed with either or both of the following substances yellow arsenic * 

 (orpiment) and resin. The mixture is then fused either before an open 

 fire or by steam-heating. Steam is practically confined to the European 

 factories. The arsenic is said to make the lac opaque and to impart a rich 

 straw colour to the shell-lac, but its action would appear to be mainly if not 

 entirely mechanical. It is responsible for the opacity and rich straw colour 

 of all the finer qualities of hand-made shell-lac. But the inquiry for a sub- 

 stitute for arsenic has often been made, though not as yet supplied. A 

 yellow colouring material that will fuse into the lac when subjected to the JUquiiMta. 

 temperature that corresponds to 35 Ib. steam power is required. Arsenic 

 is not, however, employed in the preparation of garnet or button lacs, 

 nor other grades where fulness of colour is no disadvantage. 



The object of the resin is to lower the melting-point, a condition essential Object ot 

 for many industries and one known from fairly ancient times (witness 

 Acosta's allusion to it in 1578). Its value, therefore, is fully recognised 

 and a certain amount is not only admissible by the rules of the trade 

 (2 to 5 per cent.) but few of the shell-lacs that are regularly exported can 

 be said to be entirely free from resin. During seasons of high prices the 

 proportion is often, however, raised until it passes from the condition of 

 permissible admixture to what might be called criminal adulteration. 



Lac Fusing. The specially washed and bleached lac, mixed with its Lac 

 required proportions of arsenic and resin, is now (by the hand manufacture) 

 placed within long narrow bags (20 feet by 2 inches). For one quality of 

 lac American drill is necessary, for another a cloth specially made at the 

 Cawnpore cotton mills is preferred, and for a third two bags are required, a**, 

 one within the other. After being charged the bag is arranged in front of 

 a long open fire and so fixed up that it may be twisted the while it is being 

 moved slowly along. The foreman operator sits on a little raised mud 

 platform, on the immediate left of the fire and slightly behind it. With 



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