Enamels and enamelling; an introduction to the preparation and ...

IX.
SUBSIDIARY MATERIALS.
As is the case in other chemico-technical trades, the manufac-
ture of enamels entails the use of various subsidiary materials
which, although not entering into the composition of the
product, are yet essential for the preparation of the same.
However, in the branch with which we are now concerned,
these subsidiary materials are few in number, and may be
advantageously divided into four classes, viz. : water, fuel,
pickling materials and ammonium carbonate.
Owing to the importance of these materials both in regard
to the item of cost in which respect fuel heads the list and
also to their influence on the resulting enamel, it is necessary
to devote a few words to their consideration.
WATER.
The principal use of water in the enamel industry is as
a vehicle for the various materials during the operation of
grinding ; and
the properties of the water employed may
have a considerable influence on those of the enamel. Thus,
if the water contains organic impurities in suspension, these
will be retained, by the materials to be ground, just
as in a
filter, and as they will be carbonised in the subsequent process
of fusion this may explain why, for example,
some enamel-
makers are unable to produce perfectly white or really
handsome-coloured enamels in delicate shades.
If the impurities present in the water are merely in sus-
pension, the difficulty is easily got over by filtration through