OBJECTIONS TO ELECTRO-GILDING. 131 



battery rather weak, the gold will be light-coloured ; so that every 

 variety of shade may be imparted. A very rich dead gild may be 

 made by adding ammoniuret of gold to the solution just as the 

 articles are being put in. 



Colouring of Gilding. A defective coloured gilding may be im- 

 proved by the same method as that adopted in the old process to 

 colour gilding or gold, namely, by the help of the following mix- 

 ture: 



3 parts Nitrate of Potash 



1J Alum 



11 Sulphate of Zinc 



1^- Common Salt. 



These ingredients are put into a small quantity of water, to form a 

 sort of paste, which is put upon the articles to be coloured : they are 

 then placed upon an iron plate over a clear fire, so that they will 

 attain nearly to a black heat, when they are suddenly plunged into 

 cold water : this gives them a beautiful high colour. Different hues 

 may be had by a variation in the mixture. 



To dissolve Gold from Gilt Articles. Before regilding articles 

 which are partly covered with gold, or when the gilding is imper- 

 fect, and the articles require regildiug, the gold should be removed 

 from them by putting them into strong nitric acid ; and when the 

 articles have been placed in the acid, by adding some common salt, 

 not in solution, but in crystals. By this method gold may be dis- 

 solved from any metal, even from iron, without injuring it in the 

 least. After coming out of the acid, the articles must be polished. 

 The best method, however, is to brush off the gold as described for 

 silver (page 113), which gives the polish at the same time. 



Objections to Electro-gilding. Objections have also been made to 

 the application of electro-gilding to the arts, of the same kind as 

 those urged against electro-plating ; but the now almost universal 

 adoption of this process by gilders, because of the perfection to 

 which the articles are brought, forms the best answer we can give 

 to such objections. However, let us take a hasty glance at the old 

 process and its consequences, that we may be enabled to judge of 

 the comparative merits of both methods. 



Before the introduction of electio-deposition, the only method of 

 gilding was by forming an amalgam of gold and mercury, which, at 

 the consistence of a thin paste, was brushed upon the articles over 

 a strong heat; the mercury being gradually dissipated, the gold 

 remained fixed upon the articles. This procsss is most pernicious, 

 and destructive to human life : the mercury, volatilized by the 

 heat, insinuates itself into the bodies of the workmen, not withstand- 



