Imitations and Reconstruction 211
"strass,"
derived from a man named Strass of Strassburg, capital of the province
of Alsace-jjorraine, Germany, who invented one of the several formula?
and processes employed to create the brilliant, heavily
lead-impregnated glass so enormously used in the counterfeiting of
gems. While the many prescriptions for the strass composition vary in
constituents and proportions, a fair sample of these mixtures is as
follows:
Pure powdered quartz...........38.2
Red lead ...................... 53.3
Potassium carbonate ........... 7.8
The
ingredients are pulverised, mixed, and heated in a crucible with a
temperature raised gradually until the compound fuses, with great care.
It is maintained at that point for about thirty hours and then slowly
decreased. The factors in securing a result that will fulfil all
requirements are the thoroughness of the previous mixing, the
regularity of the temperature, the duration of the fusion, and the
slowness of cooling. The clear paste is cut for imitation diamonds,
while for the coloured gems the hue desired is imparted by the solution
of metallic oxides and other substances; manganese oxide
