Ceramic tiled panel

This is in response to Mark Vine's request for an outdoor coating for a
ceramic tile panel.  This reminded me of a request that I received in
1991.  It was not exactly the same but the conservator required an
outdoor durable coating.

We evaluated information on Acryloid B-44, B-48, B-67, B-72 and Butvar
B-98.  I believe the Butvar and the Acryloid B-48 were the only ones
recommended by the manufacturers for exterior use.  We have tested the
B-48 and its main problem seems to be that it is acidic (around pH 4).
It had relatively good resistance to yellowing under our conditions of
aging (dark & fluorescent light aging).  I believe that the conservator
considered using B-44 (exterior durability??) as well.  In our tests,
the B-44 was more neutral than the B-48.  The B-48 was, however, more
resistant to yellowing than the B-44. B-48 is a poly(methyl
methacrylate)/(butyl acrylate) (20-40%) copolymer. B-44 is a poly(methyl
methacrylate) /(ethyl acrylate) (<<50%) copolymer. B-48 is softer than
B-44.

I have no information on solubility or removability after aging.  We
have not tested the Butvar but the manufacturer says that it has good
resistance to sunlight and exterior weathering.  Mr Vine might want to
investigate these further.  If he would like to discuss this further, I
can be reached at the address below.

Jane Down
Conservation Scientist
Canadian Conservation Institute
+1 613 998 3721
Fax: +1 613 998 4721

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                  Conservation DistList Instance 8:81
                   Distributed: Sunday, April 2, 1995
                        Message Id: cdl-8-81-005
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