Light bleaching

We are considering purchasing a light bleaching unit and would be
very interested in other people's opinions and experiences of the
different types of equipment.  Due to the higher temperature
generated, the metal halide system, as used in plant nurseries, and
described by Roy Perkinson, (Book and Paper Group Annual 20 (2001)
27), has the advantage of lessening bleaching time to between one
and four hours, hence lower risk of softening inks and paper in the
water.  Also costs less than daylight bulb system.  However, metal
halide bulbs, 1000 watts each, generate a considerable amount of
heat which needs to be screened, and conservators need protection
from the brightness.  UV filtres are required to protect the object.
Is there any information on the amount, if any, of ozone generated
by metal halide bulbs?  Any recent research into the long term
effects on paper, printing inks etc., of using metal halide, as
opposed to daylight bulbs?  Any comments on bleaching results, ease
of use, health and safety issues for either method would be welcome.

Alice Rugheimer
Western Art on Paper Conservation
British Museum
Great Russell Street
London WC1B 3DG
England UK


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                  Conservation DistList Instance 17:20
                 Distributed: Thursday, August 14, 2003
                       Message Id: cdl-17-20-014
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