460 On the Art of Glass-Painting. 



oxide into that of peroxide, in which latter state it tinges glass 

 green. In order to preserve it in the state of protoxide, these 

 receipts prescribe various deoxygenating substances to be 

 stirred into the melted glass, such as smiths' clinkers, tartar, 

 soot, rotten wood, and cinnabar. 



One curious circumstance deserves to be noticed, which is, 

 that glass containing copper when removed from the melting- 

 pot sometimes only exhibits a faint greenish tinge, yet in this 

 state nothing more than simple exposure to a gentle heat is 

 requisite to throw out a brilliant red. This change of colour 

 is very remarkable, as it is obvious that no change of oxy- 

 genation can possibly take place during the rccuisso?i. 



The art of tinging glass by protoxide of copper and flashing 

 it on crown-glass, has of late years been revived by the 

 Tyne Company in England, at Choisy in France*, and in 

 Suabia in Germany, and in 1827 the Academy of Arts at 

 Berlin gave a premium for an imperfect receipt. To what 

 extent modern glass-painters make use of these new glasses 

 I am ignorant ; the specimens that I have seen were so strongly 

 coloured as to be in parts almost opake, but this is a defect 

 which might no doubt be easily remedied f. 



I shall now conclude these observations by a few notices 

 respecting glass tinged by fusion with gold, which, though 

 never brought into general use among glass-painters, has 

 I know been employed in one or two instances, flashed both 

 on crown- and on flint-glass. Not long after the time when 

 the art of making the copper-red glass was lost, Kunckel ap- 

 pears to have discovered that gold melted with flint-glass was 

 capable of imparting to it a beautiful ruby colour. As he 

 derived much profit from the invention, he kept his method 

 secret, and his successors have done the same to the present 

 day. The art, Jiowever, has been practised ever since for the 

 purpose of imitating precious stones, &c., and the glass used 

 to be sold at Birmingham for a high price under the name of 

 JCiv's glass. The rose-coloured scent-bottles, &c., now com- 

 monly made are composed of plain glass flashed or coated 



autres ecrivains a diverses epoques, tlecrivaient ces procedes." (p. 192.) 

 He fixes the restoration of the art in France at about the year 1800, when 

 Brongniart, who had the direction of the Sevres porcelain manufacture, 

 worked with Meraud at the preparation of vitrifiabie colours, p. 194. 

 Among modern artists he particularly mentions Dihl, Schilt, Mortel^gue, 

 Robert, Leclair, Collins, and Willement. — R. T.] 



* Bulletin de la Sociele cr Encouragement pour I' Industrie Nationalc, 1 826. 



•)- Though it is difficult to produce the copper-glass uniformly coloured, 

 it is easy to obtain streaks and patches of a fine transparent red. For this 

 purpose it is sufficient to fuse together 100 parts of crown-glass with one of 

 oxide of copper, putting a lump of tin into the bottom of the crucible. 

 Metallic iron employed in the same way as the tin throws out a bright 

 scarlet, but perfectly opake. 



