UV filtering materials

Joachim Huber <joachim.huber [at] prevart__ch> writes

>... 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). ...

In my experience, UV window films will normally last 7 to 10 years
before they need to be replaced.  Usually there are visible signs of
film failure such as peeling round the edges, haziness or formation
of bubbles, but it is prudent to check with a UV meter every 6-12
months to ensure that the UV level is still below 75
microwatts/lumen.  Remember to check every pane in a multi-pane
window as some pieces of film may deteriorate faster than others.

Dr Barry Knight
Head of Conservation Research
The British Library
96 Euston Road
London NW1 2DB


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                  Conservation DistList Instance 19:7
                  Distributed: Thursday, July 21, 2005
                        Message Id: cdl-19-7-010
                                  ***