108v - - - - - [continued]
thus one mixes it & reducing it into pb small stones, purging it of its impurities. Then one puts it to cook neatly in a pot earthen vessel in the furnace of those who make pots, and one leaves it there until the pots are cooked. Next, one mixes it again with essence of sal ammoniac & one grinds it very well, and one empties the muddy & clean water in a separate vessel. Again, one puts the same essence on top & one grinds & again one puts the muddy water with the other. And one does thusly, until it has passed everything. In this way, one purges & purifies it, & one renders it very fine & handleable. Having taken away the water, by tilting it or with a sponge, one takes the residue and one dries it. Then, moistening it with the above mentionned water, like one does with the other eau sand, one uses it in chassis, where, if it retracts, it is a sign that it has not reheated enough & that one needs to reheat it further. This one is appropriate for molding all metals, and especially gold & silver, and the more it is used the better it is. One needs to set aside the one in which you cast lead or tin, for it would sour the gold you would cast.
Alum de plume should be reheated in a chaulderon crucible covered with a tile in a strong flamme charcoal fire, so that the impurities, which could be there, burns with it which does not burn. This is done either in the goldsmith’s forge, surrounded with bricks, or in a fourneau à vent with foeu de fusion, so that the sable demeure asses long temps crucible remains red for a quarter hour. This is done more to purify it than for anything else. It becomes reddish on the surface & on the inside it remains white & better dried out #
at left middle margin
# After your alum de plume is cooled, pestle it in a mortar, then grind it on the marble, and it will be rendered in very fine wooly filaments, which gives binding to the sand, without getting burned as other things do, which is a fine invention. Pestle it in the mortar, by dragging the pestle, for the flying dust could enter your throat or land on your face, which will give you reason to scratch yourself well. Put a little every time in the mortar, to avoid the flying dust. It is better to grind it thusly, in the mortar, dragging the pestle, than on the marble, car where c it spreads & in the mortar, it collects on all sides. Render it very fine & soft to the touch.
Clay,to make circles around molds, should be very fat & handleable, and serves only to make the surrounding of the molds. Thus, one needs only choose it well fat, and beat very well & moisten it moderately with some water & keep it in a pit or in a terrine and make numerous holes with a stick in it, which fill with water, in order to keep always fresh & soft, so that it is always ready to use when needed.
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