neutral density film

Tobias Baskin baskin at BIOSCI.MBP.MISSOURI.EDU
Wed Jun 23 15:21:38 EST 1993


>Date: Wed, 23 Jun 1993 11:55:47 -0500
>To: plant-biology at net.bio.net
>From: cawiah at garnet.berkeley.edu
>Subject: neutral density film

>We are looking for neutral density film to reproducably alter light
>intensity in growth chambers. Folks at Edmund scientific don't sell it, but
>claim it exists. Anybody know where to buy it ?

>MC

Dear MC,
        I don't know about a commercial product sold as neutral density
film, but I do know about lots of do-it-yourself solutions. I once used
bleached paper towels opened up and overlapped for this purpose, and lately
I have been using sheets of Miracloth (cheese cloth works too) and white
xerox paper. Hardware stores and garden supply shops sell black shade cloth
for use in green houses. I think you can buy this by the yard, and anyway,
your green house folks at Cal may have some to spare. Using black or white
substances for this is good because if you use a colored material the
absorption will change the distribution of light energy (not necessarily a
problem, depends on what you want). Most growth chambers I have worked with
have a sheet of clear plexiglass between the plants and the bulbs. If you
really want to keep the spectral output exactly the same (scattering from
white paper changes the spectrum to some extent), then you can take that
piece of plexiglass, put masking tape strips over it in a grid pattern,
spray black paint and then remove the tape. This gives you a bunch of clear
spaces amid opaque regions. You can adjust the amount of attenuation by
controlling the ratio of masked to unmasked areas. 
        Good luck and have fun!
        Tobias Baskin
Tobias I. Baskin   Biological Sciences  Tucker Hall  University of Missouri
Columbia, MO  65211 USA  Tel: 314 - 882 - 0173  FAX 314 - 882 - 0123
e-mail:  Baskin at biosci.mbp.missouri.edu




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