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Re: osram lumilux -- or - reflecting of hood materials

Scott wrote:

 Aluminum flashing from Home Depot won't reflect better
than good white paint but it will do about as well as Reynolds aluminum


By aluminum flashing I mean aluminum flashing that is painted white in
the factory. It's probably powder paint but I don't actually know what
process they use. Even in direct sunlight it is still pretty good after
30 years or so. Check out the aluminum facia on an older house.
Unpainted aluminum flashing would make a very poor reflector.

Any solvent based paint that cures by something evapourating from it
will not be impervious to moisture. This includes latex, oil base or air
cured polyurethane. If you are using the paint as a difuse reflector
then you really need something that will stay pristine or the
effectiveness will be dramatically reduced. I have my doubts that white
epoxy would contain enough pigment to be highly reflective. The pigment
is trapped in a bed of clear epoxy and it seems to me light would be
trapped in the epoxy coating between the pigment particles.

Epoxy may appear to be expensive because of it's high cost for a given
volume but it is not really. It just doesn't contain any solvents that
will evaporate off anyway. You can do a large hood with about a quart of
epoxy. Each coat of epoxy is like 10 coats of a solvent based paint but
even if you were to put 30 coats of solvent based paint (which would
take weeks to apply and would leak fumes forever) you still would not
have a waterproof barrier. For protection epoxy is the material of
choice. For reflectivity, I think powder painted steel or aluminum would
be the right choice. It's what they use in fluorescent fixtures anyway
and it's cheap. Those reflectors in turret style shoplight fixtures make
for very efficient fixtures. In fact, if there is room it is a good idea
to use those reflectors inside the hood. The people that design fixtures
for a living are not idiots, they know what works the best.