DOI Page / Citation link:
https://doi.org/10.11588/diglit.19574#0410
G L A 277
out, it is laid on a table of copper, where it having lain till it has
cooled and come to its confiftence, it is carried on fork* to the
tower of the furnace, where it is fet to anneal for twenty-four
hours.
Formerly the tables were fet into the annealing tower in great
numbers, perhaps an hundred at a time, in a perpendicular Actu-
ation, which was the occafion that thofe fet in firft, bearing in
fome meafure the preffure of all the laff, were bent, and thus ren-
dered unfit for ufe; but a way has been fince found out to remedy
this inconvenience, by feparating them into tens, with an iron
fhiver, which, by dividing the weight, diminifhes it, and by that
means preferves the tables as flat as when they went in.
Glafs, made much harder than any in the common way, may
be made by means of borax, in the following method : Take
four ounces of borax, and an ounce of fine fand ; reduce both
to a fubtile powder, and melt them together in a clofe crucible
fet in a wind furnace, keeping up a ftrong fire for half an hour ;
then take out the crucible, and when cold break it, and there
will be found at the bottom a pure hard Glafs, capable of cutting
common Glafs like a diamond. This experiment, duly varied,
may lead to feveral ufeful improvements in the arts of Glafs,
enamels, and factitious gems; and fhews an expeditious method
of making Glafs without any fixed alcali, which has been gene-
rally thought an effential ingredient in Glafs ; and it is not yet
known, whether, calcined cryftal or other fubftances being added
to this fait inffead of fand, it might not make a Glafs approach-
ing to the nature of a diamond.
Of the different forts of table or windotv Glass. There are
divers forts of this Glafs, made in divers places for the ufe of
building.
Crown Glafs, of which there are two kinds, diftinguifhed by
the places where they are wrought, viz. »
1. RatclifF or Cock-hill crown Glafs, which is the beft and
clearer!, and was firft made at the Old Bear-garden, at the Bank-
fide, Southwark : Of this there are twenty-four tables to the
cafe, the tables being of a circular form, about three feet fix
inches in diameter.
2. Lambeth crown Glafs, which is of a darker colour than the
former, and inclining to green.
French Glafs, called alfo Normandy Glafs, and formerly Lor-
rain Glafs, becaufe made in thofe provinces: At prefent it is
made wholly in the nine Glafs works in France, of which five
are in the forefl of Lyons, and four in the county of Eu ; the
laft at Beaumont, near Rouen. This is of a thinner kind than
©ur crown Glafs, and, when laid on a piece of white paper, ap-
pears
out, it is laid on a table of copper, where it having lain till it has
cooled and come to its confiftence, it is carried on fork* to the
tower of the furnace, where it is fet to anneal for twenty-four
hours.
Formerly the tables were fet into the annealing tower in great
numbers, perhaps an hundred at a time, in a perpendicular Actu-
ation, which was the occafion that thofe fet in firft, bearing in
fome meafure the preffure of all the laff, were bent, and thus ren-
dered unfit for ufe; but a way has been fince found out to remedy
this inconvenience, by feparating them into tens, with an iron
fhiver, which, by dividing the weight, diminifhes it, and by that
means preferves the tables as flat as when they went in.
Glafs, made much harder than any in the common way, may
be made by means of borax, in the following method : Take
four ounces of borax, and an ounce of fine fand ; reduce both
to a fubtile powder, and melt them together in a clofe crucible
fet in a wind furnace, keeping up a ftrong fire for half an hour ;
then take out the crucible, and when cold break it, and there
will be found at the bottom a pure hard Glafs, capable of cutting
common Glafs like a diamond. This experiment, duly varied,
may lead to feveral ufeful improvements in the arts of Glafs,
enamels, and factitious gems; and fhews an expeditious method
of making Glafs without any fixed alcali, which has been gene-
rally thought an effential ingredient in Glafs ; and it is not yet
known, whether, calcined cryftal or other fubftances being added
to this fait inffead of fand, it might not make a Glafs approach-
ing to the nature of a diamond.
Of the different forts of table or windotv Glass. There are
divers forts of this Glafs, made in divers places for the ufe of
building.
Crown Glafs, of which there are two kinds, diftinguifhed by
the places where they are wrought, viz. »
1. RatclifF or Cock-hill crown Glafs, which is the beft and
clearer!, and was firft made at the Old Bear-garden, at the Bank-
fide, Southwark : Of this there are twenty-four tables to the
cafe, the tables being of a circular form, about three feet fix
inches in diameter.
2. Lambeth crown Glafs, which is of a darker colour than the
former, and inclining to green.
French Glafs, called alfo Normandy Glafs, and formerly Lor-
rain Glafs, becaufe made in thofe provinces: At prefent it is
made wholly in the nine Glafs works in France, of which five
are in the forefl of Lyons, and four in the county of Eu ; the
laft at Beaumont, near Rouen. This is of a thinner kind than
©ur crown Glafs, and, when laid on a piece of white paper, ap-
pears