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The Initial Stage
The main constituents of glass are silica, lime,
and soda. If the glass is surrounded by moisture, the soda and lime
will be dissolved out, turning the glass surface into a water-rich
gel. When the soil dries out for a season, this gel turns into a
paper-thin film of silica that wraps loosely over the vessels
shape. Repeated wetting and drying, year-in and year-out, creates
a crust consisting of dozens of these silica wrappings.
The appearance of the crust depends largely upon
the chemistry of the soil that surrounded the vessel over the centuries.
The higher the acidity of the soil, the more rapidly the weathering
process will occur. In the case of the most common green-tinged
glass, the outer part of the crust often hardens into an enamel-like
shell that covers the entire vessel.
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Cosmetic bottle with enamel-like shell
4th century A.D.
Ht., 5.9 cm
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