Mountain plaster is greyer, and that from the region of Albi is whiter. It has to be heated over a closed fire, such as a reverberatory furnace or fours de barbiers. The more freshly heated, the better it is to work with. It should be finely crushed on marble. After preparing your hollow mold of sulfur or another [material] and oiling it and surrounding it with a circle, soak your plaster in water, not too thick, and rub it well with your finger, and if it makes bubbles, throw on more powder of the said plaster and crush it with your finger until +
at left bottom margin of folio 012r
+ it makes no more bubbles. Then once more throw and sprinkle plaster powder on top and leave to set well, then scrape the powder off.