Water glass

Barbara Appelbaum <aandh [at] mindspring__com>

>I got a question from a colleague not on the list about water glass:
>was it commonly used in restoration, particularly as a coating on
>gilding?  What is its solubility and is there some way to recognize
>it?

Waterglass, also known as "sodium silicate" (Na2SiO3) was commonly
used as an adhesive, and was recommended as such for the repair of
glass in the 19th-20th centuries, e.g. Gaudens, P. and Jackson, A.
"How to mend china and bric-a-brac", Boston: Charles Branford Co.,
1953, p. 105. Waterglass was also used as a binder and flocculant
for ceramic glazes, an additive for concrete, manufacturing paper,
and in fireproofing textiles. The proportions of silica:alkali
(SiO2:Na2O) can vary from 2.5:1 to 4:1, to make a water soluble
"glass", but since the important CaO stabilizer is missing, it
remains soluble in water, and is only effective if it is kept dry.
The only examples that I have seen have been gray and crumbly-- much
like broken up "rock candy".

Stephen Koob
Conservator
The Corning Museum of Glass
One Museum Way
Corning, NY 14830
607-974-8228
Fax: . 607-974-8470


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                  Conservation DistList Instance 14:63
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