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

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When lead or tin casts fill with bubbles

If your casted work became porous, it can be repaired with very firm wax, and you can gild or silver it afterwards. If you cast fine, the alloy of one of lead to one lb of tin is good. But if you cast with lead[ligue illegible], indeed you need one lb of lead to two ℥ of tin, because lead is fat and sticky, goes over the alloy. I have cast a very small lizard that way. If you cast something thick, which keep the heat for a long time, it will make bubble if there is not enough tin. Your mold should not be cold, but cool enough that you can hold it without burning your hand, or that you can hold your finger into the cast without burning yourself. Your tin or lead must be like red. Cast your lead first, then cast tin. When you are going to cast, add a piece of resin to your mixture, then a little looking—glass tin. If you add too much lead to your tin, the mixture wouldn’t be fluid enough. To know [the right proportion], If tin cries loudly, it means that there is not too much lead; if tin cries softly, it means that you added too much lead. Be wary

at left middle margin of folio 131v

You can solder with the same matter, then rework it and [remove away all the unwanted thick parts] with a burin.

at left middle margin of folio 131v

Tin is a metal that can[…], makes bubbles and burn, and more capricious to work with than gold and silver.

at left bottom margin of folio 131v

Lead must not be only red, it must be quick, and as liquid as water, which is a sign of its perfect heat. Your mold must be so hot that you couldn’t bear to put your finger into it. Do not open your mold until is has cooled down. Just as for silver and gold, it is a sign of good casting when lead comes out through the vent holes.

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” not to heat your mold too hot because it makes it brittle, it makes bubbles and shrinks tin, and would also break the molded thing. Do not dip you hot mold into water because tin and lead would shrink.