1good, for the cupels made from them, since they
are not sufficiently dry,
frequently crack and break in the fire and absorb the metals. If ashes of
beech or similar wood are not to be had, the assayer makes little balls of such
ashes as he can get, after they have been cleared of impurities in the manner
before described, and puts them in a baker's or potter's oven to burn, and from
these the cupels are made, because the fire consumes whatever fat or damp
there may be. As to all kinds of ashes, the older they are the better, for it is
necessary that they should have the greatest possible dryness. For this
reason ashes obtained from burned bones, especially from the bones of the
heads of animals, are the most suitable for cupels, as are also those ashes
obtained from the horns of deer and the spines of fishes. Lastly, some take the
ashes which are obtained from burnt scrapings of leather, when the tanners
scrape the hides to clear them from hair. Some prefer to use compounds,
that one being recommended which has one and a half parts of ashes from the
bones of animals or the spines of fishes, and one part of beech ashes, and half a
part of ashes of burnt hide scrapings. From this mixture good cupels are
made, though far better ones are obtained from equal portions of ashes of
burnt hide scrapings, ashes of the bones of heads of sheep and calves, and
ashes of deer horns. But the best of all are produced from deer horns alone,
burnt to powder; this kind, by reason of its extreme dryness, absorbs metals
least of all. Assayers of our own day, however, generally make the
cupels from beech ashes. These ashes, after being prepared in the
manner just described, are first of all sprinkled with beer or water, to make
them stick together, and are then ground in a small mortar. They are ground
again after being mixed with the ashes obtained from the skulls of beasts or from
the spines of fishes; the more the ashes are ground the better they are.
Some rub bricks and sprinkle the dust so obtained, after sifting it, into the
beech ashes, for dust of this kind does not allow the hearth-lead to absorb
the gold or silver by eating away the cupels. Others, to guard against the
same thing, moisten the cupels with white of egg after they have been made,
and when they have been dried in the sun, again crush them; especially if they
want to assay in it an ore or copper which contains iron. Some moisten the
ashes again and again with cow's milk, and dry them, and grind them in a
small mortar, and then mould the cupels. In the works in which silver
is separated from copper, they make cupels from two parts of the ashes of
the crucible of the cupellation furnace, for these ashes are very dry, and from
one part of bone-ash. Cupels which have been made in these ways also
need to be placed in the sun or in a furnace; afterward, in whatever way
they have been made, they must be kept a long time in dry places, for the
older they are, the dryer and better they are.
frequently crack and break in the fire and absorb the metals. If ashes of
beech or similar wood are not to be had, the assayer makes little balls of such
ashes as he can get, after they have been cleared of impurities in the manner
before described, and puts them in a baker's or potter's oven to burn, and from
these the cupels are made, because the fire consumes whatever fat or damp
there may be. As to all kinds of ashes, the older they are the better, for it is
necessary that they should have the greatest possible dryness. For this
reason ashes obtained from burned bones, especially from the bones of the
heads of animals, are the most suitable for cupels, as are also those ashes
obtained from the horns of deer and the spines of fishes. Lastly, some take the
ashes which are obtained from burnt scrapings of leather, when the tanners
scrape the hides to clear them from hair. Some prefer to use compounds,
that one being recommended which has one and a half parts of ashes from the
bones of animals or the spines of fishes, and one part of beech ashes, and half a
part of ashes of burnt hide scrapings. From this mixture good cupels are
made, though far better ones are obtained from equal portions of ashes of
burnt hide scrapings, ashes of the bones of heads of sheep and calves, and
ashes of deer horns. But the best of all are produced from deer horns alone,
burnt to powder; this kind, by reason of its extreme dryness, absorbs metals
least of all. Assayers of our own day, however, generally make the
cupels from beech ashes. These ashes, after being prepared in the
manner just described, are first of all sprinkled with beer or water, to make
them stick together, and are then ground in a small mortar. They are ground
again after being mixed with the ashes obtained from the skulls of beasts or from
the spines of fishes; the more the ashes are ground the better they are.
Some rub bricks and sprinkle the dust so obtained, after sifting it, into the
beech ashes, for dust of this kind does not allow the hearth-lead to absorb
the gold or silver by eating away the cupels. Others, to guard against the
same thing, moisten the cupels with white of egg after they have been made,
and when they have been dried in the sun, again crush them; especially if they
want to assay in it an ore or copper which contains iron. Some moisten the
ashes again and again with cow's milk, and dry them, and grind them in a
small mortar, and then mould the cupels. In the works in which silver
is separated from copper, they make cupels from two parts of the ashes of
the crucible of the cupellation furnace, for these ashes are very dry, and from
one part of bone-ash. Cupels which have been made in these ways also
need to be placed in the sun or in a furnace; afterward, in whatever way
they have been made, they must be kept a long time in dry places, for the
older they are, the dryer and better they are.
Not only potters, but also the assayers themselves, make scorifiers
and triangular crucibles. They make them out of fatty clay, which is
dry5, and neither hard nor soft. With this clay they mix the dust of old
broken crucibles, or of burnt and worn bricks; then they knead with a
pestle the clay thus mixed with dust, and then dry it. As to these crucibles,
and triangular crucibles. They make them out of fatty clay, which is
dry5, and neither hard nor soft. With this clay they mix the dust of old
broken crucibles, or of burnt and worn bricks; then they knead with a
pestle the clay thus mixed with dust, and then dry it. As to these crucibles,