Composition of Enamel . 405 
tains a little calcined borax or glass of borax, though you 
may employ it also with that flux alone. 
But the flux which, according to my experiments, gives 
to cobalt blue the greatest splendour and beauty, is that 
composed of white glass, (which contains no metallic 
calx,) of borax, nitre, and diaphoretic antimony well 
washed. When this glass is made for the purpose of 
being employed as a flux for blue, you may add less of 
the white oxyd of antimony : a sixth of the whole will 
be sufficient, 
Violet . 
Black calx of manganese, employed with saline 
fluxes, gives a very beautiful violet. By varying the 
fluxes, the shade of the colour may also be varied : it is 
very fixed as long as it retains its oxygen. The oxyd of 
manganese may produce different colours; but for that 
purpose it will be necessary that we should be able to 
fix its oxygen in it in different proportions. How to 
effect this, as far as I know, has never yet been disco- 
vered. 
These are all the colours obtained from metals. From 
this it is evident that something still remains to be disco- 
vered. We do not know what might be produced by 
the oxyds of platina, tungsten, molybdena, and nickel ; 
all these oxyds are still to be tried; each of them must 
produce a colour, and perhaps red, which is obtain- 
ed neither directly nor with facility from any of the 
metallic substances formerly known and hitherto em 
ployed. 
General Remarks. 
Those who paint on enamel, on earthen- ware, porce- 
lain, &c. must regulate the fusibility of the colours by 
the most tender of those employed, as for example, the 
