White and Yellow Glass

Addition of an antimony-rich mineral, and an oxidizing atmosphere in the furnace, will produce glass with a white coloration. The reaction between the antimony and the lime from the frit causes a precipitation of minute needles of calcium antimonate. As the antimony increases from 1% to 10%, the white coloration changes from eggshell-fine to creamy-rich.

A brilliant yellow coloration is produced if the mineral added to the glass contains both antimony and lead. Under the right conditions, the lead and antimony precipitate out together, creating needles of lead pyroantimonate. The Romans rarely used yellow glass on its own: instead they included it in polychrome mosaic wares and architectural friezes.

Detail of mosaic glass

Glass and shell mosaic from the courtyard of the Casa del Granduca at Pompeii
First half of 1st century A.D.