Hi Jim-

Try this one for starters:

This page discusses the penetration of UV light in plastics:
http://www.newton.dep.anl.gov/askasc...9/eng99272.htm

Also for those of you who seriously wish to do your own experiment re UV
penetration into your trailer (or whatever else you can think of) here is a
site that sells UV sensitive beads for cheap...$7 (US). The cheapest UV
meters are around $150 (US).
http://www.stevespanglerscience.com/product/1350

I have no financial interest in any of this BTW. I am thinking that I just
might put up a few posters again...chalk it up to midlife crisis. Not so
sure that the wife will tolerate it though.

Casey