101r - - - - - [continued]
again quite hard, and then add to it three ℥ of minium, & pound again together & put it in the crucible, which you will cover with an appropriate tile, not too thick, so that heat reverberates better. Then put it on the grill of your furnace, having put a few thick, rounded tiles under it. Next, fill your charcoal furnace to the mouth with charcoal, heaped to the top, and let it light, and always maintain the heat even, without letting the charcoal go down. And to this effect, always ensure that the furnace is heaped to the top & full of charcoal and maintain it like this for one day. The first experiment I made, only a yellow mass emerged, like minium alone when vitrified, & with gold grains, in a mass at the bottom. Try cemented gold together with antimony.
at left top margin
If you need more heat, put tiles on the edge of the mouth of the glowing furnace, lean them one against the other to make the heat reverberate.
Figure at left middle margin
Topaz
The same dose can be observed for all gemstones, which is one part the weight of calcined pebbles with three partsthe weight of minium, pounding all separately in a copper mortar for emeralds, & in an iron mortar to make topazes or amber color, with pestles similar to the mortars. Emerald & topaz are of the same heat, & for an hour & a half, otherwise they could burn. Ruby wants more time & more fire, & colored with gold leaf. I believe that pumice stone or fire—stone for the ruby would be better. See enamels. Also try to mix pieces of colored glass or enamels instead of pebbles. If the mass is not colored enough, pound it further in the iron mortar.
at left middle margin
Slightly burnt tartar mixed in makes beautiful yellow, but not much is needed. Arene also makes it more yellow.
Salt for melting
Mix saltpeter & common salt and melt them together & cast on melted copper or ch in a bain, & it purifies & makes it run marvellously. First, one ought to decrepitate the common salt, that is to say holding it over a good fire until it no longer crackles or, to melt it better, in an four à vent. And throw it neatly on marble, then crush it & grind it very finely, then put it in a crucible on as much saltpeter & let it boil, & mix them together until
at left bottom margin
It cleans & purifies metal well.
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