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

ENAMELS FOK ARTISTIC PURPOSES. 177
In the preparation of all these enamels care should be
taken, when fusing the materials, to prevent the access of re-
ducing gases to the contents of the crucible, by covering the
latter with a close-fitting lid ; otherwise an inferior enamel
will be sure to result.
by-
RECIPES FOR COLOURED ENAMELS.
A good ground for backing coloured enamels is furnished
Sand .8 parts.
Chalk 1 part.
Calcined borax ....... 3 parts.
This mass is particularly suitable for use under pale red,
purple red, and blue, as well as other delicate colours, since
it exerts no injurious influence on the pigmentary substances.
A somewhat refractory mass, also useful for the same
purpose, is obtained from
Quartz meal ....... 60 parts.
Alum .
. 30
Common salt . 35
Minium . . ... . . . . 100
. Magnesia . ,....-.'. . 5 ,,
TRANSLUCENT COLOURED ENAMELS.
For artistic purposes (painting in enamel) use is made of
certain colours, which, for the production of particular shades,
have to be translucent. A few recipes for these, as given by
Deck, the technical director of the Sevres porcelain works, are
appended below.
Flux or Ground Mass.
Soft. Hard.
Quartz 4-5 5-0
Potash 1-5 1-5
Soda 7-0 7'0
Minium .... .
12
3-5 3-Q