DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.19574#0382
other in ufe agairi; becaufe glafles made of that may be afforded
cheaper.
Cryftal requires a foft and white fand, common glafs on*
more rough, hard and grating like a file; fands differ very much
from one another; for fome will melt quickly, and mixing with
the fait immediately be converted into glafs; others again will
endure a flrong fire, but in general there is no fand, but what
may be made into glafs.
To make Frit, you muft have two hundred pounds of tarfo,
prepared as we have fhewn; or fine fand, and mix therewith
about one hundred and thirty pounds of fait, alfo prepared after
the manner elfewhere mentioned. See TARSO.
Care muft be taken to mix the two materials well together;
then put them into the furnace to be calcined, after it has been
well heated to make the Frit.
During the firft hour, the fire muft be moderate, and the
Frit continually {lured with an iron rake, that the material?
may the better incorporate; then the fire muft be increaied to a
very flrong heat for the fpace of five hours, continuing always
flirring the Frit with the rake, which is very r.eceffary to the
preparation of it.
After the fpace of five hours, the Frit, having had fufficient
fire, will be made and reduced to lumps about the bignefs of a
filbert, which, if it be enough, in breaking will be lio^ht and
white without any yellow ; for, if you find any of that, you muft
put it into the furnace again, till it lofe that yellow colour
which it will infallibly do.
By how much the more the materials are ftirred and" cal-
cined in the furnace, they will be fo much the more refined,
and melt more eafily in the pots; after this you take it out of
the furnace, and let it cool; then you lay it on boards in a dry-
place, otherwife the moifture would caufe the fait to melt into
water, and only the tarfo would remain behind, which of itfelf
Would never be made into glafs.
After this you cover it well for fear of dull, for vou muft
take a great deal of care and caution to have a fine cryftal.
The Frit, thus made, ought to be as white as fnow ; but, dur-
ing the time it is making, you muft try whether the quantities
are well proportioned or not, which muft be done by putting
fome of the Frit into a crucible, and afterwards on a clean piece
of glafs; where it may be feen whether it be well made by its
joining together, and being clear; if it be too hard or too foft,
you muft increafe or diminifh the quantity of fait in it; which
thofe experienced in the art, know very well how to do at firft
fight i this being well prepared, and kept in a dry place, will laft
three
cheaper.
Cryftal requires a foft and white fand, common glafs on*
more rough, hard and grating like a file; fands differ very much
from one another; for fome will melt quickly, and mixing with
the fait immediately be converted into glafs; others again will
endure a flrong fire, but in general there is no fand, but what
may be made into glafs.
To make Frit, you muft have two hundred pounds of tarfo,
prepared as we have fhewn; or fine fand, and mix therewith
about one hundred and thirty pounds of fait, alfo prepared after
the manner elfewhere mentioned. See TARSO.
Care muft be taken to mix the two materials well together;
then put them into the furnace to be calcined, after it has been
well heated to make the Frit.
During the firft hour, the fire muft be moderate, and the
Frit continually {lured with an iron rake, that the material?
may the better incorporate; then the fire muft be increaied to a
very flrong heat for the fpace of five hours, continuing always
flirring the Frit with the rake, which is very r.eceffary to the
preparation of it.
After the fpace of five hours, the Frit, having had fufficient
fire, will be made and reduced to lumps about the bignefs of a
filbert, which, if it be enough, in breaking will be lio^ht and
white without any yellow ; for, if you find any of that, you muft
put it into the furnace again, till it lofe that yellow colour
which it will infallibly do.
By how much the more the materials are ftirred and" cal-
cined in the furnace, they will be fo much the more refined,
and melt more eafily in the pots; after this you take it out of
the furnace, and let it cool; then you lay it on boards in a dry-
place, otherwife the moifture would caufe the fait to melt into
water, and only the tarfo would remain behind, which of itfelf
Would never be made into glafs.
After this you cover it well for fear of dull, for vou muft
take a great deal of care and caution to have a fine cryftal.
The Frit, thus made, ought to be as white as fnow ; but, dur-
ing the time it is making, you muft try whether the quantities
are well proportioned or not, which muft be done by putting
fome of the Frit into a crucible, and afterwards on a clean piece
of glafs; where it may be feen whether it be well made by its
joining together, and being clear; if it be too hard or too foft,
you muft increafe or diminifh the quantity of fait in it; which
thofe experienced in the art, know very well how to do at firft
fight i this being well prepared, and kept in a dry place, will laft
three