IMITATIONS OF GEMS. 17*3
fraction
of light. He accomplished the task so for that in many instances,
either all three, or one or the other of his objects, were attained.
The strass is composed of silex (quartz, flint, or pure sand), potash,
borax, red lead, and sometimes arsenic. To 300 parts of silex add 96
parts potash, 27 parts borax (prepared from the boracic acid), and 514
parts of white lead, and 1 part arsenic; or according to another
method, mix 7 ounces and 24 grains of quartz with 10 ounces and 7 1/2 drachms
red lead, 3 ounces and 6 drachms pure pearlashes, 3 27/30 drachms
borax, and 12 grains arsenic. The mixture is put into a covered Hessian
crucible, and kept at a great heat in a pottery furnace for
twenty-four hours. The longer the mass is kept in a fluid state the
harder and clearer it will be when turned out and cooled. This
discolored strass is used by the lapidaries for imitating the" diamond,
rock-crystal, and white topaz.
For
imitating the colored gems various colored ingredients are employed.
To obtain that intensity-of color approaching nearest to the original
gem, it is experience alone which can guide the manufacturer. In order
to imitate the uniform and intense colors, the strass coloring
ingredients are to be of the finest powder, and very intimately mixed;
the mass is then to be exposed to a very great heat, and in that state
left for nearly thirty hours, so that the cooling may be gradual.
Numerous establishments in Germany and France are now engaged in the
manufacture of the strass and colored pastes, each of which possesses
secrets, acquired by experience, for producing these articles iu the
greatest perfection.
A. Artificial Topaz. Take of perfectly
white strass one ounce and six drachms, glass of antimony thirty-seven
grains, and cassius purple one grain; or add to six ounces of strass
half a drachm of crocus martis.
B. Artificial Ruby. This may be obtained, from the pre-
Flickr
Stumbleupon
Scribd
