CompojlUoK of Enamel. t^ 



in equal quantities. The whole muft be gently heated until 

 the yellow colour appear, and the matter is to be employed 

 with the fluxes pointed out for yellows. Yellow of filverj 

 like purple, cannot endure a ftrong heat : a nitric folution 

 of (liver mav be precipitated by the ammoniacal phofphat of 

 foda, and you will obtain a yellow precipitate, which may be 

 nfed to paint in that colour with fluxes, which ought then to 

 be a little harder. 



Befides the methods above mentioned, the baft manner of 

 employing the oxyd of filver is, in my opinion, to employ it 

 pure: in that cafe, you do not paint, but flain. It will be 

 lufficientj then, to lay a light coating on the place which you 

 wifh to ftain yellow, and to heat tlie article gently to give it 

 the colour. You mufl: not employ too llrong a heat : the 

 degree will eafily be found by practice. When the article 

 has been fufiiciently heated, you take it from the fire and 

 feparate the coating of oxyd, which will be found reduced to 

 a regulus : vou will then obferve the place which it occu- 

 pied tinged of a beautiful yellow colour, without thicknefs. 

 It is chieflv on tranfparent glafs that this procefs fuccccds 

 befl:. Very fine filver filings produce the fame effeft : but 

 what feemed to me to fuccced befl in this cafe, was fulphat 

 of filver, well ground up with a little water, that it may be 

 extended very fmooth. From what has been faid, it may rea- 

 dily be feen that this yellow mufl: not be employed like other 

 colours ; that it muft not be applied till the reft have been 

 fufed ; for, as it is exceedingly fufible, and ready to change, 

 it would be injured by the other colours; and as the coating 

 of filver which is reduced muft be removed, the fluxes would 

 fix it, and prevent the poflibility of its being afterwards fepa- 

 rated. Working on glafs is not attended with this inconve- 

 nience, becaufe the filver-yellow is applied on the oppofite 

 fide to that on which the other colours are laid. 

 Gncn. 



Green is obtained dire6lly from the oxyd of copper. All 

 the oxyds of copper are good : they require little flux, which 

 even muft not be too fufible : one part or two of flux will 

 be fufticient for one oxvd. This colour agrees with all the 

 fluxes, the faline as well as the metallic; which tends to vary 



a litlk 



