and fixed by Fufion on d'lffeunt vitreous Bodies: i^lj 



filver formed part of their compofition ; but, when exaftly 

 followed, nothing fatisfatSlory was obtained. C. Miiaiid^. 

 whom I have already had occafion to mention, has tound 

 means to make as beautiful paintings on glafs as the antients^ 

 by empiovmg muriate of fiber, oxide of zinc, white argil,' 

 and yellow oxide of iron, 1 hefe colours are applied oa 

 glafs merely p )unded, and witliout a flux. The oxide of 

 iron bri'.igi the vellow to that colour which it ought to have 

 after baking, and contributes with the argil and oxide of zinc 

 to deco.ypofe the i.iuriate of, filver without deoxidating the; 

 filvcr. Alter the bakins, there remains a duil which has not 

 penetrated into the glat's, and- which is eafily removed. 



This vellow, wi^en employed thicker, gives darker fliades, 

 and produces a rulfot.- 



Blues. 



It is well known that thefe are obtained fiom the. oxide of 

 cobalt. Ail chenilfts are acquainted with the preparation of 

 them. Thofe of Sevres, which are juftly efteemed for their 

 beauty, are indebted for it only to the care employed in ma- 

 nufadiuring them, and to the quality of the porcelain, which 

 appears more proper for receiving them in proportion to the 

 degree of heat it can bear. 



1 remarked rel'petting the oxide of cobalt a fadl which 

 is perhaps not known to chemilis: it is volatile in a violent 

 lieat : it is to this property we muft afcribe the blueifli tint 

 always affumed by white in the neighbourhood of the blue. 

 I have placed exprefsly on purpofe, in the fame cafe, a white 

 piece clofe to a l)lne one, and found that the fide of the white 

 piece next the blue became evidently blueifli. 



The blue of hard porcelain, dcltined for what is called the 

 ground for a great heat [les fo7ids au graml feu), is fufed. 

 with feld-fpar; that of foft porcelain has for its flux filex, 

 potafli, and lead: it is not volati'izcd like the preceding, but 

 the heat it experiences is very inferior to that of hard porce- 

 lain. 



Thefe colours, when previoufly fufed, do not change at all 

 in the application. 



Blues on giafs exhibit the fame phaenomena as thofe on 

 oft pjrcelain. 



Greens. 



The greens emploved in painting are made with green oxide 

 of copper, or, fomctimcs, with a mixture of yclhuv or blue. 

 Thcv mull be prcvioully fufed with their flux, othcrwifc th«y 

 will become black; biu after this firll fulion they no longer 



B3 They 



|h?ngt 



