North American Fruit Explorers mailing list at ibiblio

[Don Yellman <dyellman@earthlink.net>]

Robert:  You are right about plexiglass; it is acrylic not polycarbonate.
You're also right that Lexan is just the GE tradename for its polycarbonate
resin product.  I have the impression that polycarbonates are quite a bit
tougher than the acrylics, which are an older technology.  Glass is still the
best all-around home greenhouse material, tempered glass if hail is a
consideration, but I do think it filters out a fair amount of the uv portion 
of
the spectrum, based on what I have observed with my seedling plants.  Rgds, 
Don
Yellman, Great Falls, VA

"Robert L. Thomasson" wrote:

> >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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