282 BRONZING. 



inflammable substance, as oil, for instance, will have 

 in some degree, the same effect ; which is owing to 

 their attraction for oxygen. 



The Tinning of Copper. 



Sheets of copper may be tinned in the same man- 

 ner as iron. Copper boilers, saucepans, and other 

 kitchen utensils, are tinned after they are made. 

 They are first scoured ; then made hot ; and the tin 

 rubbed on, as before, with resin. Nothing ought to 

 be used for this purpose but pure grain-tin ; but 

 lead is frequently mixed with the tin, both to adul- 

 terate its quality, and make it lay on more easily; 

 but it is a very pernicious practice, and ought to be 

 severely reprobated. 



To whiten Brass or Copper by boiling. 



Put the brass or copper into a pipkin with some 

 white tartar, alum, and grain-tin, and boil them to- 

 gether. The articles will soon become covered 

 with a coating of tin, which, when well polished, 

 will look like silver. It is in this manner that pins, 

 and many sorts of buttons, are whitened. 



BRONZING. 



Bronzing is colouring plaster, or other busts and 

 figures, with metallic powders, in order to make 

 them appear as if made of copper or other metals. 

 The powders used for this purpose are either fine 

 copper-filings, aurum musivum, or copper precipi- 

 tated from its solution in aqua fortis by iron. Having 

 done over the substance to be bronzed with a dark 

 green colour, the projecting parts are touched with 

 either isinglass size, japanners' gold size, or, in some 

 cases, with drying-oil, or oil-paint ; the powders are 

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