"safe" green light

Ross Koning Koning at ECSUC.CTSTATEU.EDU
Wed Nov 27 16:37:45 EST 1996

At  8:55 AM 11/27/96 -0800, Sandra Mackey wrote:
>In our general plant biology course, students treat lettuce seeds with red
>and far red light for a seed germination experiment.  They are working under
>"safe" green light when adding water for seed imbibition, and while placing
>seeds into the red and far red light boxes.  My green light source is a heavy,
>bulky wooden box with fluorescent bulbs and a green filter.  I would like to
>replace this green light source with a desk lamp and green fluorescent bulbs
>I don't know if the green fluorescent bulbs leak wavelengths of light other
>green.  Can any one tell me if they have successfully use green fluorescent
>bulbs for this experiment?


I'm not sure what you are planning to use, but
I can tell you that "green" is not always safe.
Most fluorescent tubes have phosphors that do
not emit much FR light (730 nm).  The red-
emitting phosphors in older-style tubes were
weak, and a green filter could reasonably eliminate
them.  Modern tubes are enriched in red-emitting
phosphors (I start to worry whether the green filter
is good enough).  I have never seen a green fluorescent
tube, but if it were thoroughly coated inside with ONLY
one phosphor (emitting green) that would be a great
addition to my equipment wish list.  Unfortunately
most "green bulbs" are merely dipped in green laquer
which cracks and peels with heat, time, and abuse...
not so safe any more.  Also, when you say bulb, I am
thinking of incandescent types which are definitely
NOT safe.  The green laquer used on those does NOT
prevent FR light from exposing your project.  *And*
the cracking of the laquer is much more extensive
because of the more-extreme heat generated...and
I have found that the laquer is not always dipped deeply
enough around the base of the bulb.  The big old housing
has some advantages after all.


Ross Koning                 | Koning at ecsu.ctstateu.edu
Biology Department          | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | Phone: 860-465-5327
Willimantic, CT  06226  USA | Fax: 860-465-5213

                Plant Physiology is Phun!

 /\|___/\     //\______COOH   NH-CH2-CH=C-CH2OH  \/OH
|  |  |  |    |  |  ||       //\___     \CH3     /\|/\\/\\COOH
 \/ \/|\/|    \\/ \ /       N  ||  N            |  |
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