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Fashion of preparing aspaltspat

It is found in earth in Germany, the color of cooked
plaster, made of long filaments, very soft to handle. And because it
is mixed with earth and filth, one pestles it roughly
&one makes little balls, having, for this purpose, soaked it in
sal ammoniac water of such a composition that you were told
above. One places these balls to reheat in the fire of the furnace
of the potters, then one soaks it again in the same
water. The earth and the coarseness and
filth go to the bottom, and the pure aspalt,
which is light & soft and handleable as wet flour, adheres
with the water and goes to the surface, clouding the
water, empty that cloudy part in a separate receptacle.
Having sat, one, one empties the water by tilting, or by taking
it away with a sponge, and thepure aspalt
remains at the bottom. Dry it & employ it in frame, having
been moistened with sal ammoniac water. And try it in the
frame, in which it shrinks when reheated or dried, that is to
say that one needs to reheat it again on a good fire and redden it.
Thus, for medals and flat things, you should use this one, because it is
the most perfect of all for gold, silver, copper,
lead, latten, & tin, for it withstands the fire
& reddens whenever need be, without corrupting. The more it is used,
the b better it is, & it does not spoil. At the beginning
it is white, & being used it becomes grey. However make sure to put
aside the one that served for casting lead & tin &
latten, for gold would sour in it, & would not come
out of it well. And to do this better, you could put it aside to be used
for each metal. 



See Gesnerus, De lapidibus



It endures ten or twelve castings without corrupting, it withstands the
fire & reddens, it is suitable for all metals. It is so
tenacious that should the frame be straked, it holds.





The spat almost does not set, even though it is reheated & is
a kind of plaster. Raw, it breaks easily with the
fingers.


Excellent secret for molding hollow and very delicately infine
gold

Cast with your aforementioned sand your animal and lizard
or other thing with silver billon & it will come out very
neat. E But take heed to mold it hollow, or at least leave a
small hole, in its mouth or in another place. Next,
gild it with fine gold, as uniform as it will be possible
for you, three or four or five times, & until your gold has
the thickness of a piece of paper or something similar,
& all the scales will always show equally. Next, put it in good
aquafortis, which, by this hole, will corrode the billon
& the gold will remain hollow & light &
wonderful.

