THE ARTIST'S ASSISTANT. 151
Magnefia is an earth, which, when fluxed with
any vitreous body, produces a broken crimfon, or
foul rofe colour. It is to be had, prepared fit for
ufe, except a more perfeft levigation, from thofe
who fell colours to the glafs-makers. It is ufeful not
only for fome purpofes as a red, but for the ieveral
compofitions for black, purple, and fome browns.
The soodnefs of the ma'-rnefia muft be determined
by the fame means as that of zaffer.
Smalt is, as before mentioned, zaffer vitrified with
proper additions; which are generally fixt alkaline
falts and fands, or calcined flinls, which are fome-
times ufed as a blue in enamel. But being hard, it
requires, for fuch purpofes, to be ufed with a flux,
which increafing the body of glafs in too great a
proportion for the tinge, is apt to dilute the colour
too much, where great force is wanted ; therefore
the ufe of the zaffer itfelf is in moft cafes preferable.
There have neverthelefsbeen, as was above obferved,
fome parcels of fmalt, or vitrified calx of cobalt,
brought from Saxony, which are of an extreme
ftrong body of colour, and will bear any proportion
of flux neceffary to render them as foft as my be re-
quired, without weakening the colour too much, for
any purpofe. Common fmalt, however, ground very
fine, and mixt with a fourth part of its weight of
borax (which is much the moft powerful and kind-
ly flux for zaffer) will run pretty well, and may be
ufed where either a full colour is not demanded,
or where the work will admit of the colours being
laid on thick. The goodnefs of fmalt may be judged
of by its bright and deep colour: and the lefs it in-
clines to the purple the better. In order to judge
of the ftrength of the colour, the fmalt fhould be
reduced
Magnefia is an earth, which, when fluxed with
any vitreous body, produces a broken crimfon, or
foul rofe colour. It is to be had, prepared fit for
ufe, except a more perfeft levigation, from thofe
who fell colours to the glafs-makers. It is ufeful not
only for fome purpofes as a red, but for the ieveral
compofitions for black, purple, and fome browns.
The soodnefs of the ma'-rnefia muft be determined
by the fame means as that of zaffer.
Smalt is, as before mentioned, zaffer vitrified with
proper additions; which are generally fixt alkaline
falts and fands, or calcined flinls, which are fome-
times ufed as a blue in enamel. But being hard, it
requires, for fuch purpofes, to be ufed with a flux,
which increafing the body of glafs in too great a
proportion for the tinge, is apt to dilute the colour
too much, where great force is wanted ; therefore
the ufe of the zaffer itfelf is in moft cafes preferable.
There have neverthelefsbeen, as was above obferved,
fome parcels of fmalt, or vitrified calx of cobalt,
brought from Saxony, which are of an extreme
ftrong body of colour, and will bear any proportion
of flux neceffary to render them as foft as my be re-
quired, without weakening the colour too much, for
any purpofe. Common fmalt, however, ground very
fine, and mixt with a fourth part of its weight of
borax (which is much the moft powerful and kind-
ly flux for zaffer) will run pretty well, and may be
ufed where either a full colour is not demanded,
or where the work will admit of the colours being
laid on thick. The goodnefs of fmalt may be judged
of by its bright and deep colour: and the lefs it in-
clines to the purple the better. In order to judge
of the ftrength of the colour, the fmalt fhould be
reduced