DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.19574#0406
G L A 373
the frit, called the calcar; a fecond to work the Glafs; and a
third, called the leer, to anneal it. See the article FURNACE.
For the making cryftal Glafs, take of the whiteft tarfo, pound-
ed fmall and fearced as fine as flower, an hundred pounds, to
iixty-five pounds of polverine.
Mix them well together, and put them into the furnace, cal-
led calcar, firft heating it: Keep a moderate fire for an hour,
continually ftirring the materials, that they may incorporate and
calcine together.
Afterwards increafe the fire for five hours; after which take
out the matter, which, being now fufficiently calcined, is called
fait of frit, which is alio called bollito.
Take the frit out of the calcar, lay it up in a dry place, keep
it covered from the duff, and let it lie for three or four months.
To make the Glafs, take of this cryftal frit; fet it in pots
into the furnace, adding to it a proper quantity of manganefe;
(fee MANGANESE) when they are both fufed or melted, caft
the fluor, i. e. the melted matter, into fair water, to purify it
from the fait called fandever, which, if not cleared from it, would
make the cryftal obfcure and cloudy.
This lotion or warning mult be repeated feveral times, till
the cryftal is fully purged.
When this has been done, let it boi] for four, five, or fix days ;
then try whether it has had manganefe enough ; and, if it look
ftill greenifh, add more manganefe, by little and little at a time,
with difcretion; but be fure to take care not to overdofe it, be-
ea-ufe the manganefe inclines it to a blackifh hue.
Then let the metal clarify, till it becomes of a clear and min-
ing colour; which when it comes to, it is fit for blowing, or to
be formed into veffels at pleafure.
There are three principal kinds of Glafies, diflinguifhed by the
form or manner of working them, viz. i. Round Glafs, as thefe
of our veffels, phials, drinking GlafTes, &c. 2. Table or window-
Glafs, of which there are various forts, viz. crown Glafs, jea-
lous Glafs, &c. and plate Glafs or looking Glafs.
The method of working or blowing round Glass. The work-
ing furnace being round has fix bocca's or apertures; at one of
which, called the great bocca, the furnace is heated, and the pots
of frit fet in the furnace; two other fmailer holes, called boccel-
la's, ferving to lade or take out the melted metal, at the end of an
iron to work the Glafs: At the other holes are put in pots of
other fufible ingredients to be prepared, and at lafl emptied into
the lading pot.
There are to be fix pots in each furnace, all made of tobacco-
pipe clay, proper to fuftain not only the heat of the fire, but
B b 3 alfa
the frit, called the calcar; a fecond to work the Glafs; and a
third, called the leer, to anneal it. See the article FURNACE.
For the making cryftal Glafs, take of the whiteft tarfo, pound-
ed fmall and fearced as fine as flower, an hundred pounds, to
iixty-five pounds of polverine.
Mix them well together, and put them into the furnace, cal-
led calcar, firft heating it: Keep a moderate fire for an hour,
continually ftirring the materials, that they may incorporate and
calcine together.
Afterwards increafe the fire for five hours; after which take
out the matter, which, being now fufficiently calcined, is called
fait of frit, which is alio called bollito.
Take the frit out of the calcar, lay it up in a dry place, keep
it covered from the duff, and let it lie for three or four months.
To make the Glafs, take of this cryftal frit; fet it in pots
into the furnace, adding to it a proper quantity of manganefe;
(fee MANGANESE) when they are both fufed or melted, caft
the fluor, i. e. the melted matter, into fair water, to purify it
from the fait called fandever, which, if not cleared from it, would
make the cryftal obfcure and cloudy.
This lotion or warning mult be repeated feveral times, till
the cryftal is fully purged.
When this has been done, let it boi] for four, five, or fix days ;
then try whether it has had manganefe enough ; and, if it look
ftill greenifh, add more manganefe, by little and little at a time,
with difcretion; but be fure to take care not to overdofe it, be-
ea-ufe the manganefe inclines it to a blackifh hue.
Then let the metal clarify, till it becomes of a clear and min-
ing colour; which when it comes to, it is fit for blowing, or to
be formed into veffels at pleafure.
There are three principal kinds of Glafies, diflinguifhed by the
form or manner of working them, viz. i. Round Glafs, as thefe
of our veffels, phials, drinking GlafTes, &c. 2. Table or window-
Glafs, of which there are various forts, viz. crown Glafs, jea-
lous Glafs, &c. and plate Glafs or looking Glafs.
The method of working or blowing round Glass. The work-
ing furnace being round has fix bocca's or apertures; at one of
which, called the great bocca, the furnace is heated, and the pots
of frit fet in the furnace; two other fmailer holes, called boccel-
la's, ferving to lade or take out the melted metal, at the end of an
iron to work the Glafs: At the other holes are put in pots of
other fufible ingredients to be prepared, and at lafl emptied into
the lading pot.
There are to be fix pots in each furnace, all made of tobacco-
pipe clay, proper to fuftain not only the heat of the fire, but
B b 3 alfa