UV filtering materials

According to technical data sheets (new) UV protection films absorb
up to 99.5% of UV below 380nm. One supplier claims that UV
transmission will rise by 1-2% within 8 to 9 years. Further data is
not available. Many museums use their UV protection films on windows
for more than 10 or even 20 years believing that there is still full
optimum uv protection. Has somebody actually measured UV levels of
"old" UV protection films after 10 or more years of use? What would
ba a safe timeframe for the use of such a product considering that
UV absorption should still be effective (e.g. in Europe). We would
appreciate any comment.

Joachim Huber
Prevart GmbH
Oberseenerstrasse 93
CH-8405 Winterthur
+41 52 233 12 54
Fax: +41 52 233 12 57


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                  Conservation DistList Instance 19:5
                  Distributed: Saturday, July 9, 2005
                        Message Id: cdl-19-5-024
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