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Reflective surfaces
Hey, guys, lets not get into a flame war over reflective surfaces! I feel
some of the problem is in the way we are measuring the "reflected" light.
What WE see as "white paint" may in fact not reflect either UV or infrared
worth a bucket of warm spit. It is the old thing of humans assuming that our
own eyes are the only things that count. The plants, more specifically, the
chlorophyl in the plants, just do not "see" light the way we do. Now, if we
all take three deep breaths and relax (8*D) perhaps we can disagree
respectfully.
For ordinary purposes, white paint, at least while it is relatively new, is a
pretty good reflector. It scatters the light, and that works pretty darned
well when it comes to lighting aquaria. Aluminum is a better reflector of ALL
wavelengths of the electromagnetic energy we call "light." You may notice
that the Hubble Space Telescope primary and secondary mirrors are coated with
ALUMINUM, not white paint.
OK, I admit that the TELESCOPE needs a different sort of reflectance. It has
to FOCUS light rays from "point sources at infinity" to the Dawes Limit. The
"Light" the telescope is focussing includes both Infrared and Ultra Violet.
The Laws of Physics can be interpreted that all of the light emitted by the
source (tubes, bulbs, halides, etc.) ought to be either directly shining on
our plants or effectively reflected so it shines on our plants. It really
does not matter whether we use Aluminum (Mylar, polished Aluminum, etc.) or
white paint or whatever, so long as the light ends up going into the tank.
Aluminum DOES reflect things better. White paint DOES reflect thing pretty
well.
May I suggest that dust, condensation, or lime deposits on the cover glass is
much more significant than the reflective surfaces we work so hard with?
Also, dust and lime deposits on the fluorescent tubes (in the absence of
cover glass) is also quite significant. It does not take very much dust to
reduce the light by 50%!!
I LIKE aluminum reflectors. Aluminum foil works pretty darned well, and it is
cheap and easy to replace. Paint works pretty darned well, too. You might try
using aluminum foil to experiment with reflector shapes and placement. A
broad foil reflector, gently curved, reflects a lot better than a narrow one,
tightly curved to the tube. I tend to believe George is right as to the
effectiveness of gluing aluminum foil to half of a fluorescent tube. I see
significantly brighter tubes when the aluminum is INSIDE the glass tube. I
get even brighter lights with gently curved (and slightly crinkled) aluminum
foil reflectors. White paint works pretty well, but it depends upon exactly
where the reflector is located.
I hope this will help.