Compojiltan of tlnamel. 5 



the fame proportions as fand : you may even dlminifh the 

 quantity of this matter to 50 per cent, if you are defirous to 

 obtain an enanie) veiy fufible. This will depend alf) on the 

 Caliirie employed ; for that which is moft charged with tin Is 

 the leaft fufib'le. 



When you wifli to have fluxes for the colours, you employ 

 the fame compofitions before mentioned, except that you 

 put little or no tin into the lead. In the latter cafe you 

 niuft generally employ minium. This flux is good for cer- 

 tain colours, but not for all. There are fome which bc- 

 come tamifhed by fluxes, tliat captain the o-xyds of lead. la 

 that cafe, you mull make fluxes without oxyd of lead. Nitre 

 and borax are generally ufed for making this glafs, but yoa 

 add no calx of tin. The following are thofe which I have 

 tried : 



Three parts of filiceous fand, one of chalk, and three of 

 calcined borax, give a matter proper to be ufed as a flux for 

 purples, blues, and other delicate colours. 



Three parts of white or flint glafs, one of calcined boras', 

 a quarter of a part of nitre, one of the white oxyd of anti- 

 mony made with nitre well waflied, give an exceedingly 

 white enamel, which may ferve alfo as a flux for purple, and 

 particularly for blue. 



Sixty parts of enamel fand or lefs, thirty of alum, thirty- 

 five of lea-falt, and a hundred of minium, or any other 

 oxyd of lead, give a white enamel when the fluxes do 

 not predominate too much, and a gelatinous glafs when a 

 great deal of fluxes has been ackled. This glafs is good for 

 red, and the enamel may be applied to all kinds of day ca- 

 pable of fuftaining a ftrong heat. 



It is of great importance to remark, and to know, that the 

 fand employed for enamel mult not be fand which contains 

 only filex : fand of that kind alone is of no ufe. The land 

 proper for this purpofe is that which contains talc with filcx- 

 To make a fand proper tor enamel and the fluxes of colours, 

 &€. there mull be nearly one part of talc and three of fili- 

 ceous fand. 



What appears to me mod efll-ntial in regard to the fuccefs 

 *f enamel, is the choice of i'aud. It is very poflfible to com- 



pofe 



