Deterioration of acrylic glazing

Caitlin Granowski <caitlin.granowski [at] nga__gov__au> writes

>Over the past 18 months, the National Gallery of Australia has
>noticed a breakdown in some of their acrylic glazing, both old and
>relatively new stock. The breakdown has taken form as a white powder
>and as a waxy deposit, seen both on the work of art and window mat,
>and on the inside of the glazing. This has occurred on
>screen-prints, lithographs and silver gelatine prints.

I have never seen this, but recently I read that certain surfactants
can cause stress cracking in acrylic plastics.  This might explain
the sodium you found also, as many surfactant solutions use sodium
as a cheap way to boost surfactant efficacy.  I read about it in a
book I reviewed for JAIC in the recent Spring 2005 issue, volume 44
number 1.  The book I found this in is given away for free on the
web, and was written by an industrial cleaning company.  The authors
only touch on this problem briefly, but it is quite alarming.  The
authors warn that polycarbonate, nylon, and polymethylmethacrylate
are especially sensitive to damage, even from mild aqueous cleaners.
Stressed polycarbonate apparently is particularly sensitive.  Other
plastics that are *not* as sensitive are polyethylene,
polypropylene, polyvinyl chloride, polystyrene, polyurethane, and
epoxy.  I would look into other sources that deal in-depth with
plastic sensitivity to cleaners.

Thomas J. Braun
Daniels Object Conservation Laboratory
Minnesota Historical Society


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                  Conservation DistList Instance 19:17
                 Distributed: Thursday, October 6, 2005
                       Message Id: cdl-19-17-008
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