THE ARTIST'S ASSISTANT. 145

lefs, confidering the nicety of the fubjecl, fuch direc-
tions can be given, as will infure fuccefs in the firlt
trials, with regard to feveral of the procelTes, or
even the general operations but whoever will make
themfelves mafters of the principles on which they
depend, which are all along intimated, will eafdybe
able to cor reel; their own errors.

A judgment formed by fome little experience, is
likewife requifite for the preparing well the colours
with certainty. For as different parcels of the fame
fubftance vary frequently in their qualities, with
regard to the degree or proportion, it is neceffary to
make allowance accordingly in the proportion of
the quantities in the mixtures. This cannot be done
till fome little previous trial be made ; and the power
of judging of them be gained by an experimental
acquaintance with them. But as the materials in ge-
neral are very cheap, and the experiments may be
made in the fame fire where aftual bufmefs is done ;
whoever would excel in the art of preparing and
ufing enamels, fhould take a confiderable fcope of
experimental enquiry into the effect of all the various
proportions and commixtures of the fubftances ufecL

Of the Subflances ufed for forming Fluxes.

Minum. or red lead, is ufed as a fluxing body, for
forming the enamel for grounds; as alfo in com-
pounding fluxes for the colours. It requires no pre-
paration for thefe purpofes ; only it is proper it
fhould be pure ; which may be known by the me-
thod before given, page 47. This flux renders the
enamel foft; but producing fome proportion of yel-
low colour, is not fit for all ufes.

Fixt alkaline fait of vegetables, is fometimc ufed
alfo, in forming the mixture for enamel grounds; as

T likewife