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Ingredients
Naturally colored glass is composed of 72% silica,
15% soda, 10% lime, and 3% other impurities. Beach sand, the main
ingredient in glass, contains silica and lime, the latter component
coming from crushed shells. There are two steps to producing naturally
colored glass:
(1) melting the ingredients at a relatively low temperature
(circa 750 degrees C) to obtain a white, granular substance (frit)
that could easily be stored for later use;
(2) re-melting the frit
in a far hotter furnace (circa 1150 degrees C), thereby transforming
it into fluid glass.
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Primary ingredients
for Roman glassmaking
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