Photographic light box works

We have several photographic light box works in our collection here
at Auckland Art Gallery that I would welcome advice on. A typical
design consists of a photographic transparency such as a Cibatrans
print on polyester film sandwiched between two pieces of Perspex
e.g. 2mm in front and 4mm thickness behind.  This is held in the
front of a metal box containing fluorescent strip lights, the actual
design varying with each one depending on the artist. When switched
on they make a striking display--but from a conservation point of
view, the combination of colour photograph with heat and lots of
light is not a happy one.

All the works are showing problems with the photographic
transparency cockling and sagging in-between the Perspex. This
distortion is not especially noticeable when the work is illuminated
but in some cases there are mottled patterns caused where the two
surfaces touch. Some modifications have been attempted in the past
with clamping the Perspex more tightly together but this seems to
have made little difference. In one set of works the distortion was
so bad soon after it was acquired that, under suggestion of the
artist, the transparencies were reprinted and laminated to Perspex
and a matte PVC film was put over the top using water based acrylic
adhesive. So far these works look good, although I do worry that as
Perspex expands more than polyester with heat there may be problems
with adhesion in the future.

Have other institutions experienced similar problems with cockling
of transparencies in light boxes? Any good solutions? I'm not
considering laminating existing transparencies but this might be an
option if at some point they can be reprinted.

There is also the problem of light fading and setting reasonable
guidelines for how long they can be displayed.  Do other
institutions have a policy on this type of work? As with other
modern photos in most cases we don't know the actual type of
photographic process or support used to get an accurate life
estimate (an issue we are trying to tackle at the acquisition stage
but meeting resistance).

I would welcome any input from fellow conservators on how to best
prolong the life of these works.

Becky Cameron
Conservator, Paper
Auckland Art Gallery Toi o Tamaki
Auckland
New Zealand


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                  Conservation DistList Instance 21:14
                   Distributed: Tuesday, July 3, 2007
                       Message Id: cdl-21-14-014
                                  ***