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

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Sand Experiments

X I have tested sand of Th{oulous}e, and after seeing it well recooked two times in a skillet, I passed it through a fine tammy cloth, like the double sieve which apothecaries use, without grinding it further on the porphyry, as I have done other times. I moistened it the sand in infusion with elm root, and in it, I molded a big piece of a portrait of Jesus. I found it unmolded very well without having to tire myself out by hitting it from behind and it molded cleanly on one side of the relief and on the other concave. And [it was] of the thickness of a coin of forty sols. I cast this very hot

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Sand from a mine, well chosen and well reheated, is the most excellent of all without trying to find all other mixtures because it receives all metal. It does not like to be used hot because it bubbles the more finely. For large works, it is not the best because it does not have enough body to sustain it,

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with the material of a frying pan mixed with a knob of . And before that, I had so reheated my molded box frame, now on the flame of my stove, now putting glowing coals beneath it, that it became almost red. I let it cool and cast it. It came out with a quite neat relief on one side & hollow on the other, as much the figure as the letters. It is true that the material was whitish, as though it were metallic, but this was because of the potin. I made another cast with frying pan material, alone in the same sand, but not as reheated. It did not come out well.

Then I molded burned bull’s foot bone, pulverized & strained through a double sieve, and wet with egg white or wine boiled with the root of an elm. I lightly knocked on top of it while molding. While opening the box frame, I found that the figures had come out not at all clean & it left the molds as though they were floury & crumbling. I wet the bone sand more so that it held together well between the figures, and in this way I molded neatly with good come—away. And even though it seemed like the ground bone was lumpy, when casting with frying pan material, it turned out that my figures were quite clean. It is true that I had really really heated up my box frame, it did not admit but one cast. I find that, when a sand is so fine that it gets as heavy as ceruse & even, without finding it arid, thin, sandy & rather spongy, that sic it molds quite neatly but it does not receive metal very well, as if it were porous and sucking up the material. But, being fatty & even, it puffs up & does not receive subtle impressions at all. I believe that the secret of casting well lies in finding a sand that conforms well to the metal, this one for lead, the other for another, because each has its own particular one, so that it be molded easily and keenly. Then let it firm up on its own for a few days if you have the leisure for it. And afterwards let it really heat up again, not instantly nor with a large fire, but little by little, otherwise it will crumble & always have some defects. Finally you must cast copper or latten or other great metals very hot and if possible with a large quantity of material that has a lot more heat than a small quantity. It’s necessary that the box frame be cold & that you cast all in one go. Always lute the opening of your box frame because metal touching fire or metal.

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This bone has to be really crushed in a mortar, it must not be reheated very much, because then it would crumble.

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[or metal] fills with bubbles. Most of all, make sure that the cast is always higher than the molded thing, since the sand swells very often when reheating if the, even in the middle, and therefore with the molded thing remaining higher than the cast, the metal cannot run easily or at all nor enter at all. Also make sure that the mold & the cast are indeed reheated. Also cast in one go & outside of the wind. And if your medal is really thin, when you want to mold it, put a card, or two or three thicknesses of paper, so that the mold will be lower than the cast. Also cast in the place where your medal will be least thick & where the relief is lowest.