Glasswork - the Scientia Review

Coloring with Metallic
Salts
Minerals and purified metallic salts are commonly
used as pigments to color glass. Natural impurities in the
sands or smoke involved in glassmaking can cause discoloration
in glass, as was often the case with earlier glass. For example,
iron in the sand and sulfur in the smoke of the burning coals
burned to make English “black bottle glass” in the 17 th century
produced a dark hue in the glass. However, nowadays these
impurities are often removed to make clear glass to be colored
only by selected metallic salts. Manganese dioxide and cerium
oxide are commonly used decolorizers, chemicals that precipitate
out, or cause to be deposited in solid form from a liquid, the
impurities.
Black Bottle
Glass from the
17 th Century
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