UV lamps

This reply is addressed to both Ramona Duncan-Huse and Alexandra
Greathead.

Fluorescence of most substances is produced by long wave UV-A and
part of medium wave UV-B, or wavelengths in the range of 400-300 nm,
but UV-A emission lamps should be used for analysis of organic
materials, as they are the least damaging.

The shorter the wavelength, the higher the energy of the radiation.
In general we can say that organic materials are more damaged by a
combination of shorter wavelength irradiation and longer exposure.

A blue wool fading card was exposed 3 times for 5 hours and a 4th
time for 8 hours (for a total of 23 hours) to the UV light produced
by a 'Black Light Blue' fluorescent lamp (UV-A only). No damage
(fading) was caused by such exposure.

Short wave UV-B lamps (280-325 nm) are used for examining minerals.

If required, I can provide further information.

Flavia Philp
Conservation Officer
The Wallace Collection
London, UK

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                  Conservation DistList Instance 11:28
                Distributed: Tuesday, September 23, 1997
                       Message Id: cdl-11-28-002
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