North American Fruit Explorers mailing list at ibiblio

["Robert L. Thomasson" <102073.3346@compuserve.com>]

>1.  Normal window  glass, which is composed of silica, will filter out a
substantial portion of the shorter, ultraviolet waves of the spectrum.
Polycarbonate (plexiglass) and lexan do not, nor does "quartz glass",
which is very expensive and rarely used.  Double pane glass would
presumably be twice as efficient at filtering out uv.<

In the interests of accuracy (but hoping not to start an argument :<)), 
Lexan is just GE's tradename for polycarbonate and polycarbonate is very
definitely not plexiglass, which is another animal altogether.   There also
 seems to be considerable contrary opinions out there on the effect of uv
light on plants.

Here is an interesting site that covers light in greenhouses:

http://www.ofa.org/bulletins/1995%20Bulletins/March%2095/0395mcmahon.htm

 - Bob



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