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?

Water glass is sodium silicate; Na2SiO3.3SiO2 an inorganic binder.
There is also potassium silicate with similar characteristics but
which is somewhat less brittle when hard.

Water glass is highly alkaline and is available usually in 35-38%
syrupy concentration which dilutes with water. Once hardened (by
combining with atmospheric CO2), it is no longer soluble in water
(or anything else with ease), but moisture will turn the normally
water-clear solid, milky. This makes it tricky to use.

It is an excellent adhesive and dried films are heat and flame
resistant and are glass hard. One would need to test any prospective
application to prevent unexpected results. I have gilt over water
glass, but to use it as a top coat, it would need to be protected
with a water-proofing layer. Hope this is helpful,

George Schwartz
ConservArt - Master Frame Makers and Art Conservators
8177 Glades Road #16
Boca Raton, FL 33434
561-482-7292
Fax: 561-482-6787


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                  Conservation DistList Instance 14:63
                   Distributed: Tuesday, May 22, 2001
                       Message Id: cdl-14-63-004
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