Crazing of acrylic sheeting

Thomas Dixon <ngvcons [at] vicnet__net__au> writes

>About two years ago we discovered that a group of about 20 large
>lithograph prints which had been framed about 3 years before
>exhibited a continuous, translucent, dull white appearance which we
>first feared was mould growth on the window mount. These prints were
>trap mounted with broad areas of mount board at the periphery of the
>prints and the white was only present in the area of the mat where
>it contacted the acrylic sheet.
>
>On disassembly, it became apparent there was no mould, but rather,
>the acrylic was minutely crazed

This is not exactly the same problem, but a museum I worked at
several years ago had a problem with some very expensive vitrines
suddenly cracking and crazing for no apparent reason. On contacting
the suppliers, and were also told "its all a mystery." A polymer
chemist told us to avoid any cleaning solutions on acrylic that were
alkaline pH, as this might cause the problem. After that, we were
much more careful about what the cleaning staff used on the outsides
of the vitrines and it didn't happen again. Although we never really
did confirm that alkaline pH cleaners were the problem, this is
consistent with Mr. Dixon's problem. Perhaps there is a chemist on
the Distlist who can comment further about this.

Jennifer Baker

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                  Conservation DistList Instance 10:54
                 Distributed: Friday, December 6, 1996
                       Message Id: cdl-10-54-008
                                  ***