Making and Knowing
A minimal edition of BnF Ms Fr 640 in English Translation

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A cast of lead or tin

Because you want to cast tin very thinly, if your medal, plant or other thing you want to mold is thin and fine, make sure to include more tin, much more than lead, namely less than the fourth part of lead for three of tin. And moreover, one only puts lead in as an alloy. Contrarily, if you want to mold something strong and thick, put a lot more lead in than tin. And for the one and the other you can put in a little looking—glass tin, but only a very little, with a little resin, when you want to cast. Since then, when molding with pure new lead, I put in two ounces of pure tin for every pound of lead. And when molding with pure tin, I put in two ounces of pure lead for every pound of tin. I made some plants and snakes as if they were real.

at left bottom margin of folio 110v

I cast tin when it was nearly red, and the same thing with lead, which however had not remained in the fire for too long, because it becomes brittle and burns up.