Compojtt'ion of Eftamel. f 



fu^hat of potafh produced very nearly the fame effe£t, only 

 jthe mafs was a little whiter : but neither of thefe enamels 

 was worth any thing. I did not try pure foda: I have, 

 however, heard common foda extolled ; but as it contains a 

 great deal of marine ^alt, it muft undoubtedly be on account 

 of this fait that it produces a. good effeft. Pure foda may 

 neverthelefs be tried, either alone or with marine fait; it 

 perhaps might produce no bad effeft with potafh. 



I have tried alfo a mixture of equal parts of lime and argil, 

 to which I added one part of filex, and likewifc without filexj 

 but this mixture did not fupply the place of talcky fand. This 

 fafld is not in general found in grains ; it exhibits itfelf moft 

 commonly under the form of a ftone, fuch as free-ftone ; but 

 fonie oi it is found alfo in grains. 



We fliould be much deceived in making white enamel 

 were we to employ the oxyds of tin and lead feparately, as I 

 have read "a all the authors I could find who treat on the art 

 pf pottery. None of them fay what they ought refpe«9:ing 

 enamel, nor even refpecling the compofition or nature of the 

 eaith proper for bearing an enamel. 



It is ellential that the lead and tin for making the oxyd 

 deftined to produce white enamel, fliould be fufed and mixed 

 together before they are calcined ; and if you wifh that the 

 enamel fliuuld immediately acquire its full whitenefs, it will 

 be requifite that the calcination fliould be complete. 



Bifmuth might perhaps be employed as a fubftitute for 

 the lead, and it is not improbable that it would give a good 

 produ.5t. Bifmuth alfo might be mixed with the lead in the 

 following manner ; viz. one part of lead, one of bifmuth, and 

 pneoftin: or other proportions might be employed; but I 

 have not tried any others. As the oxyd of bifmuth, how- 

 ever, is exceedingly fufible, I think it might be admitted, 

 with great advantage, into certain fluxes. I have not tried 

 what might be produced by the white calx of zinc, nor by 

 that of tin, made by dilTolving i; in the nitric, acid or by de- 

 tonation with nitre. A mixt\ire of lead and tin, detonated 

 with nitre, would be ufeful. Though the while calx of re- 

 gulus of antimony made by nitre, and well waflied, (diapho- 

 retic antimony,) produces a very beautiful white. enamel whea. 



fufed 



