I tried the hoof of an ox, quite burned, pulverized and very well crushed on porphyry, until it is fine enough to slip through your fingers without being felt. On its own, it makes a very clean mold. But because on its own it is very dry and lean, it demands to be well wet and humidified, with a thick broth with elm root.
Dross of Iron, very burned ox hoof, and felt, all burn well in a closed fire. All three ground very finely on porphyry mold very neatly in lead, without any need to reheat it much, and by casting in a box mold either hot or cold.
Felt on its own provides a very clean mold if wet, and comes off easily. And also makes the other two come off easily
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These sands can only undergo one cast
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A fat sand which sticks together neatly, makes bubbles.
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A fat metal needs lean sand.