DOI Page / Citation link:
https://doi.org/10.11588/diglit.19574#0425
G L A 391
"lifer], but is very troublefome, and the refult fubjecT: to many
faults; but this new ware is made of Glafs alone, and that with
much lefs trouble, and without the reducing it to powder, By
this art veffels of Glafs are changed into veffels of a fort of por-
celain, without altering their form ; and the meaneft Glafs ferves
as well as the beft for that purpofe; our common coarfe green
quart bottles, or the great bell Glafs, with which gardeners cover
their melons, &c. being, by this means, changeable into a beau-
tiful white fort of porcelain ware: And this is to be done in fo
eafy a manner, and at fo fin all expence, that it requires no
more trouble or charge than that of baking a common veffel of
our earthen ware. And, for this reafon, the veffels of this fort
of ware may be afforded extremely cheap. It is very certain
that all porcelain ware is a fubftance in a ftate of femivitrifica-
tion ; and, in order to bring Glafs, which is a wholly vitrified
fubftance, into the condition of porcelain, there requires no more
than to reduce it to a lefs perfectly vitrified ftate.
The queftion which would naturally be ftarted, on this occa-
fion, is, whether it be poffible to reduce Glafs to a lefs vitrified
irate, it having already undergone what is efteemed the laft
•change by fire. But when we confider that the Glafs of antimo-
Jiy, the vitrifications of many of the metals, as the Glafs of lead,
and the counterfeit gems, coloured by the metals, are more or lefs
eafily reduced again, by chemiftry, to metals, &c. the reducing
fand, flints, &c. after they are vitrified, at leaft a little way back
towards their native or priftine ftate, may appear not wholly im-
practicable, and the attempts which Mr. Reamur made on this
occafion, were what gave him the firft hints of the Glafs porce-
lain. The method of making it is this: The Glafs veffels, to
be converted into porcelain, are to be put into a large earthen
veffel, fuch as the common fine earthen difhes are baked in, or
into fufficiently large crucibles; the veffels are to be filled with
a mixture of fine white fand, and of fine gypfum, or plaifter
ftone, burnt into what is called plaifter of Paris ; and all the
interftices are to be filled up with the fame powder, fo that the
Glafs veffels may no where touch either one another, or the fides
of the veffel they are baked in. The veffel is then to be covered
dowi^and luted, and the fire does the reft of the work ; for this
is only to be put into a common potters furnace, and, when it
has flood there the ufual time of the baking the other veffels, it
is to be taken out, and the whole contents will be found no
longer Glafs, but converted into a white opaque fubftance, which
is a ve/y elegant porcelain, and has almoft the properties of
that of China.
GLAUCUS, a fea deity, represented, as Philoftratus fays,
with a long white beard and hair, foft and dropping about his
C c 4 fhoulders;
"lifer], but is very troublefome, and the refult fubjecT: to many
faults; but this new ware is made of Glafs alone, and that with
much lefs trouble, and without the reducing it to powder, By
this art veffels of Glafs are changed into veffels of a fort of por-
celain, without altering their form ; and the meaneft Glafs ferves
as well as the beft for that purpofe; our common coarfe green
quart bottles, or the great bell Glafs, with which gardeners cover
their melons, &c. being, by this means, changeable into a beau-
tiful white fort of porcelain ware: And this is to be done in fo
eafy a manner, and at fo fin all expence, that it requires no
more trouble or charge than that of baking a common veffel of
our earthen ware. And, for this reafon, the veffels of this fort
of ware may be afforded extremely cheap. It is very certain
that all porcelain ware is a fubftance in a ftate of femivitrifica-
tion ; and, in order to bring Glafs, which is a wholly vitrified
fubftance, into the condition of porcelain, there requires no more
than to reduce it to a lefs perfectly vitrified ftate.
The queftion which would naturally be ftarted, on this occa-
fion, is, whether it be poffible to reduce Glafs to a lefs vitrified
irate, it having already undergone what is efteemed the laft
•change by fire. But when we confider that the Glafs of antimo-
Jiy, the vitrifications of many of the metals, as the Glafs of lead,
and the counterfeit gems, coloured by the metals, are more or lefs
eafily reduced again, by chemiftry, to metals, &c. the reducing
fand, flints, &c. after they are vitrified, at leaft a little way back
towards their native or priftine ftate, may appear not wholly im-
practicable, and the attempts which Mr. Reamur made on this
occafion, were what gave him the firft hints of the Glafs porce-
lain. The method of making it is this: The Glafs veffels, to
be converted into porcelain, are to be put into a large earthen
veffel, fuch as the common fine earthen difhes are baked in, or
into fufficiently large crucibles; the veffels are to be filled with
a mixture of fine white fand, and of fine gypfum, or plaifter
ftone, burnt into what is called plaifter of Paris ; and all the
interftices are to be filled up with the fame powder, fo that the
Glafs veffels may no where touch either one another, or the fides
of the veffel they are baked in. The veffel is then to be covered
dowi^and luted, and the fire does the reft of the work ; for this
is only to be put into a common potters furnace, and, when it
has flood there the ufual time of the baking the other veffels, it
is to be taken out, and the whole contents will be found no
longer Glafs, but converted into a white opaque fubftance, which
is a ve/y elegant porcelain, and has almoft the properties of
that of China.
GLAUCUS, a fea deity, represented, as Philoftratus fays,
with a long white beard and hair, foft and dropping about his
C c 4 fhoulders;