Exhibition lighting standards

For many years we've used books by Thompson or Stolow as references
for display of works of art.  We touted these as "internationally
accepted standards" and worked hard to meet them ourselves and asked
borrowers to meet them as well.  We specified visible light levels
of 50 or 200 lux depending on the light sensitivity of the items and
u.v. of less than 75 microwatts/lumen.  I have been told this u.v.
standard was set because it is what a common tungsten electric bulb
put out, and also that it was the lowest level the old Crawford
meters which were in common use could measure and there was little
point setting a standard below that which we could read.

I attended the excellent lighting workshop at the AIC conference in
San Diego in 1997 and came away with the impression a new standard
of less than 10 microwatts/lumen had come in because we know that
damage is being done by low levels of u.v., the new digital meters
allow us to measure much lower u.v.levels, and the B&L Optivex
filters economically achieve it with the now common low voltage
MR-16 lamps used widely in museums.  We put this into the lighting
briefs for our new facilities and have begun to incorporate it in
our loan agreements.  I believe we have also begun to see it quoted
in other people's loan agreements.

However, I haven't found a written reference to this new
"internationally accepted standard".  I would like to be able to
refer to a conference or meeting of respected and authoritative
experts who considered the issue and signed off on a new standard,
but I don't think such a thing has happened. Can anyone point me to
a written reference or conference which establish this as an new
industry standard?

We have long had an Elsec 763 meter which, among other things,
measures u.v. to low levels.  We recently purchased a smaller and
more convenient Elsec 764 .  When we tested a new mr-16 lamp housing
in a darkened room with both meters, we found several anomalies in
the figures.  There is considerable reciprocity failure in both
meters as light levels drop below 400 lux and especially at around
50 lux both meters show much higher levels of u.v. than would appear
to actually be the case.  We also find in a series of identical
conditions our two meters read quite differently.

I'd be very grateful for suggestions on how we can measure such low
levels accurately and reproducibly.

Thomas Dixon
Chief Conservator
National Gallery of Victoria


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                  Conservation DistList Instance 15:41
                Distributed: Thursday, December 6, 2001
                       Message Id: cdl-15-41-009
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