Gail,

Ultraviolet energy (UV) is a component of visible light and part of the electromagnetic spectrum. Wherever there is visible light there is also UV, whether it is in direct line with the light source or "bounced". Various materials will absorb or reflect UV light. That is the principal that UV filtering media works on. I have also seen research presented on the use of paint which uses Titantium Dioxide (TiO2) which absorbs UV in gallery situations (TiO2 is essentially the same white stuff that Life Guards wear on their noses).

In measuring the visible light (ft. candles or lux) you have only a very general idea of UV exposure. UV intensity is also dependant on your geographic distance above sea level and on your latitudinal location on the earth - here in Denver at 5,280 feet we get twice the UV that folks in Washington D. C. get, and much of Australia gets tremendous UV exposure compared to the UK). A much more accurate measure is to utilize a UV meter the reads in micro-watts per lumnen.

A UV meter is a very useful tool because the UV filtering media (films and plexi, etc.) do not function forever - there is a definite lifespan to those materials. Unless you can monitor the UV light levels on the objects you will never know when the UV screening media is failing or the actual UV levels that your visible light is emiting.

Cheers!
Dave

David Harvey
Artifacts
2930 South Birch Street
Denver, CO  80222
303-300-5257
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