mirrors

rossb · #1 02-11-2003, 01:36 AM

I am making a new lighting hood that will contain 2 pendants (175W MH) and 2 VHO 4' tubes. Of course spectral aluminium would be ideal but failing that can you use mirror? I am not too concerned about the weight (it is to be supported both by the tank and it will be suspended from the ceiling). Does mirror work, or is it to cumbersome?

thanks
ross

StirCrazy · #2 02-11-2003, 04:50 AM

mirror is actualy a bad choice for high heat, the coating will seperate and bubble eventualy. also belive it or not they are less reflective than spectral aluminum. This is because the light has to pass throught a layer of glass befor it gets reflected and then has to pass throught the glass again.

Steve

ree-fready · #3 02-11-2003, 05:40 AM

It is not a good idea to use a mirror because it will cause a hot spot in your bulb as well from the light not being deflected by a curved or textured surface. So I`ve been told.

StirCrazy · #4 02-11-2003, 05:47 AM

Quote:

Originally Posted by ree-fready

It is not a good idea to use a mirror because it will cause a hot spot in your bulb as well from the light not being deflected by a curved or textured surface. So I`ve been told.

I have seen a couple people say this now and I am not sure how it could be true, the reflected light energy will be cooler than the bulb its self, while I can see it raising ambiant tempature I can not se it creating a "hot spot" and if you look at any reflector there is no such thing as a reflector that does not reflect any light back onto the bulb.. We try to minamize this but to me this is because we want as much energy to go into the tank as we can get and that light reflected back onto the bulb is waisted light.

I don;t think creating a "Hot spot" is a viable concern, but rather a sales gimic. Infact if you think about it a curved surface would have more of a ability to focus a wider path of light onto a small point of the bulb.. there for a curved surface would have more of a chance of creating a hot spot than a flat surface.

JMHO
Steve

ree-fready · #5 02-11-2003, 05:55 AM

I was also told that it was like a magnifying glass in focus on a particular spot but if the magnifying glass is held at a differant angle and out of focus or not concentrated on the one spot there`s no problem. But this is all second hand and I never tried myself and I stand to be corrected.

StirCrazy · #6 02-11-2003, 12:14 PM

for a magnifying glass to work it has to have a curved surface on both sides, this is what focuses the light. A flat even surface will not focus light.

Steve

rossb · #7 02-11-2003, 06:10 PM

Good point steve ( the mirror surface degradation). I think I will go with the 2' reflectors you get from the hydroponic guys.

ythanks for the advice.

ross