Perspex

This is an enquiry on behalf of Walter Castelijns, head of
conservation, Municipal Archives Rotterdam, the Netherlands, who is
not yet on the DistList.

    For a major exhibition we have mounted posters on water colour
    paper and put them between two 4 mm sheets of perspex (125 cm x
    200 cm), so the posters can be viewed from both sides. We tried
    to create an airtight sandwich by using foam tape S1707 (which
    is reported to be airtight by the manufacturer) to seal all four
    edges.  The top edge was clasped in an aluminium frame and thus
    the sandwiches were suspended from the ceiling. The posters are
    exhibited at room temperature in an unconditioned space
    (relative humidity 45 - 50%). About one week before the posters
    were hung the floor was painted with Oxan floor paint (containing
    60% white spirit). The smell of paint never quite disappeared in
    spite of ventilation.

    A few days after the exhibition opened we noticed that in every
    sandwich both perspex sheets were starting to pull away from the
    object. We tried to straighten them again by removing the air
    but they started to pull away again very quickly. Has anyone
    ever used a similar set up and experienced something like this?
    Does anyone have a suggestion as to how to solve this problem?

    Walter Castelijns
    Municipal Archives Rotterdam,
    Hofdijk 651, 3032 CG Rotterdam
    The Netherlands

Robien van Gulik and
Machteld van der Feltz

                                  ***
                  Conservation DistList Instance 12:74
                 Distributed: Thursday, March 18, 1999
                       Message Id: cdl-12-74-016
                                  ***