Lighting policy

Since the ICOM-CC triennial meeting in Lyon in 1999 discussion among
museum professionals about light levels in museums is gradually
shifting from light level (unit = lux) to the probably more adequate
light dose (unit = luxhours). Lighting standards in museums have
therefore to be reconsidered.

In our understanding this means that based on current practice
during a period of 3 month at a light level of 300lx with an average
museum opening time of 8 hours, six days a week (576 hours) there
would be a light dose of approximately 172,800 luxhours. Is the
assumption, drawn from prevailing literature, correct that (in a
range of 50 to 500lx) the degradation can be considered more or less
as a linear function of the light level. Therefore at a light level
of 400lx this would mean that the same potential of degradation is
reached after 432 hours or 9 weeks.

We are aware that the definition of light degradation is very
complex and specific to the spectrum emitted by the light source as
well as other environmental factors and the material of the museum
object itself. Nevertheless, in daily museum practice museum staff
need certain guidelines that help to consider (and insist on) light
policies. The new policy would also widen the possibilities in
architectural and exhibition design as well as access for visually
impaired and elderly people allowing for example a special view for
elderly people at a higher light level or a gradual shift over the
year.

As we think it's important that the new recommendations should be
communicated consistently right from the beginning, we wonder if
there is really no potential for interaction at higher lux levels,
inducing an accelerating effect or if this effect can be neglected
at the light levels concerned. Are there museums/research scientists
who have already developed recommendations and explanations for
luxhours? For what timeframe are these recommendations set (i.e. If
an object travels to exhibitions, for how long afterwards will it
have to rest before another set of the recommended luxhours will be
allowed?) We are aware that this question on first sight seems
straightforward and easy to answer, but we keep being puzzled by all
the implications we think are still unsolved when trying to actually
implement a luxhour regime. Any comments are most welcome,

Joachim Huber / Karin von Lerber
Prevart GmbH - Konzepte fur die Kulturgutererhaltung
Oberseenerstrasse 93
CH-8405 Winterthur
+41 52 233 12 54
Fax: +41 52 233 12 57


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                  Conservation DistList Instance 18:24
               Distributed: Wednesday, November 24, 2004
                       Message Id: cdl-18-24-012
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