Bismuth59 ore, free from every kind
of silver, is smelted by various
methods. First a small pit is dug in the dry ground; into this pulverised
charcoal is thrown and tamped in, and then it is dried with burning charcoal.
Afterward, thick dry pieces of beech wood are placed over the pit, and the
bismuth ore is thrown on it. As soon as the kindled wood burns, the heated
ore drips with bismuth, which runs down into the pit, from which when cooled
the cakes are removed. Because pieces of burnt wood, or often charcoal
and occasionally slag, drop into the bismuth which collects in the pit, and
make it impure, it is put back into another kind of crucible to be melted,
so that pure cakes may be made. There are some who, bearing these things
in mind, dig a pit on a sloping place and below it put a forehearth, into
which the bismuth continually flows, and thus remains clean; then they
take it out with ladles and pour it into iron pans lined inside with lute, and
make cakes of it. They cover such pits with flat stones, whose joints are
besmeared with a lute of mixed dust and crushed charcoal, lest the joints
should absorb the molten bismuth. Another method is to put the ore in
troughs made of fir-wood and placed on sloping ground; they place small
firewood over it, kindling it when a gentle wind blows, and thus the ore is
heated. In this manner the bismuth melts and runs down from the troughs
into a pit below, while there remains slag, or stones, which are of a yellow
colour, as is also the wood laid across the pit. These are also sold.
methods. First a small pit is dug in the dry ground; into this pulverised
charcoal is thrown and tamped in, and then it is dried with burning charcoal.
Afterward, thick dry pieces of beech wood are placed over the pit, and the
bismuth ore is thrown on it. As soon as the kindled wood burns, the heated
ore drips with bismuth, which runs down into the pit, from which when cooled
the cakes are removed. Because pieces of burnt wood, or often charcoal
and occasionally slag, drop into the bismuth which collects in the pit, and
make it impure, it is put back into another kind of crucible to be melted,
so that pure cakes may be made. There are some who, bearing these things
in mind, dig a pit on a sloping place and below it put a forehearth, into
which the bismuth continually flows, and thus remains clean; then they
take it out with ladles and pour it into iron pans lined inside with lute, and
make cakes of it. They cover such pits with flat stones, whose joints are
besmeared with a lute of mixed dust and crushed charcoal, lest the joints
should absorb the molten bismuth. Another method is to put the ore in
troughs made of fir-wood and placed on sloping ground; they place small
firewood over it, kindling it when a gentle wind blows, and thus the ore is
heated. In this manner the bismuth melts and runs down from the troughs
into a pit below, while there remains slag, or stones, which are of a yellow
colour, as is also the wood laid across the pit. These are also sold.