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

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Making diamond points for engraving

These are for sketching what you want to draw on stones and for engraving. When these points are too dull and cannot engrave, it is necessary to rub diamond against diamond; one can rub them with pumice stone powder. It is necessary to strip what you want to engrave on a lead wheel or with a stone or with glass, because the polishing is like varnish or glass and stops the diamond or sapphire from engraving well. This is why it does not engrave easily on horn, which is polished and fat. But when the polish has been taken off, it is easy to engrave.