The art of glass shewing how to make all sorts of glass, crystal and enamel : likewise the making of pearls, precious stones, china and looking-glasses : to which is added, the method of painting on glass and enameling : also how to extract the colours from minerals, metals, herbs and flowers ... : illustrated with proper sculptures / written originally in French, by Mr. H. Blancourt, and now first translated into English ; with an appendix, containing exact instructions for making glass-eyes of all colours.

CHAP. LXXXI. To Calcine Lead.

LEAD is easie to be calcined, because it is so to melt; for this purpose you may make use of the Furnace described in Chap. 52, or in a Kiln: You must put in a good quantity of Lead at a time; for in two or three Days may be calcined several Hun∣dred Weight. The Fire ought to be hot enough to melt Glass, and not hotter; for if it be hotter it will not calcine the Lead. As soon as the Lead is melted, and it yields on top a yellowish Matter; be∣gin to draw forward the calcined part with an Iron fit for the purpose, always spreading it in the inter∣nal Extremity of the Furnaces or Kilns bottom. This Lead being well calcined for the first time, ought to be put again into the Furnace moderately hot to re∣verberate. You must spread it with the Iron, and stir it continually for several Hours, and at this se∣cond calcination it will become Yellow; then searce it through a fine Sieve, and that which does not go through, must be put with other Lead to calcine a∣fresh; always taking care, that the Furnace have just a moderate heat, and be not too hot.

There are several other ways of calcining Lead which we will not mention here, because this we have shewn is the best and most easie, and will di∣spatch a great quantity in a short time. All the Pot∣ters know how to calcine it, because they make use of it in their Glasing.