DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.19571#0271
THE ARTIST'S ASSISTANT. 257
cation, but in the being fomewhat flower in vitrify-
ing, which makes it require, in proportion, a
greater ftrength of flux and fire; but to compenfate
for this difadvantage, it is clearer in its own colour,
and much freer from heterogeneous tinging bodies,
which injure the colour of the glafs, and frequently
give embarraffments where flints are ufed : the fand
requires no previous preparation for common and
groffer purpofes, efpecially where nitre is ufed,
which burns out the fulphureous matter from any
filth of the nature of animal and vegetable fubftances,
and confequently calcines them to an earth no way
injurious to the glafs; but for nicer purpofes, and
where no nitre is ufed, it is proper to purify, or
cleanfe the fand by wafhing, which may be thusdone ;
pour water upon it, and having flirred them well
about, incline the veffel immediately in fuch a man-
ner, that the water may run off, and carry with it the
filth that will float in it ; by repeating which a few
times, the fand will be freed from all the hetero-
geneous matter that is lighter than itfelf. For coarfe
glafs other kinds of fand, of a fofter texture, are ufed;
as, befides the advantage of being cheaper, they are
more eafily vitriable than flints, and confequently
make a faving in the fluxing bodies, which are to be
added to them.
Flints are the next important article in the fub-
ftances which are ufed for forming the body of glafs;
and were indeed the only kind employed in larger
works, where any better forts of glafs were manufac-
tured, before the ufe of the white fand excluded
them in all places where it is to be conveniently ob-
tained. Since, for the reafons above given, it is 2
more eligible material, unlefs for experiments, or
K k where
cation, but in the being fomewhat flower in vitrify-
ing, which makes it require, in proportion, a
greater ftrength of flux and fire; but to compenfate
for this difadvantage, it is clearer in its own colour,
and much freer from heterogeneous tinging bodies,
which injure the colour of the glafs, and frequently
give embarraffments where flints are ufed : the fand
requires no previous preparation for common and
groffer purpofes, efpecially where nitre is ufed,
which burns out the fulphureous matter from any
filth of the nature of animal and vegetable fubftances,
and confequently calcines them to an earth no way
injurious to the glafs; but for nicer purpofes, and
where no nitre is ufed, it is proper to purify, or
cleanfe the fand by wafhing, which may be thusdone ;
pour water upon it, and having flirred them well
about, incline the veffel immediately in fuch a man-
ner, that the water may run off, and carry with it the
filth that will float in it ; by repeating which a few
times, the fand will be freed from all the hetero-
geneous matter that is lighter than itfelf. For coarfe
glafs other kinds of fand, of a fofter texture, are ufed;
as, befides the advantage of being cheaper, they are
more eafily vitriable than flints, and confequently
make a faving in the fluxing bodies, which are to be
added to them.
Flints are the next important article in the fub-
ftances which are ufed for forming the body of glafs;
and were indeed the only kind employed in larger
works, where any better forts of glafs were manufac-
tured, before the ufe of the white fand excluded
them in all places where it is to be conveniently ob-
tained. Since, for the reafons above given, it is 2
more eligible material, unlefs for experiments, or
K k where