Painting glass
- Thread starter Miah2bzy
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I had the same question recently. check here for some good ideas:
http://www.marinecolorado.org/forums/showthread.php?25072-Best-paint-for-glass
http://www.marinecolorado.org/forums/showthread.php?25072-Best-paint-for-glass
I would paint a panel and place it behind the tank. I read an article in TFH years ago about painting the glass directly reducing the amount of light reflected into the tank. What the article stated was that with a regular glass panel the outside layer of glass reflects the light but when it's painted the paint absorbs the light.
I bought a sample can of latex paint at Home Depot for $3, was enough to paint the back panel 4 or 5 times with a disposable foam roller kit also from Home Depot, like another $1.50. The foam roller was thin enough and my arms long enough that I painted it in place...I almost didn't get any blue paint on the wall 
SynDen
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I have also read some articles about that, and yes if the back panel is painted it it tends to absorb the light by a significant amount and drops the par value around the back of the tank quite a bit. But that can be avoid by apply the background or paint to another layer and then attaching that to the back. Ill see if I can find the article its on advanced aquarist somewhere.
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Ya it has to do with the fact that if the back glass isn't painted and instead another panel or something is covering the back, or even if nothing is one the back, the light waves pass through the glass and bounce back into the tank, but if it is painted then the light doesn't pass all the way through it and is absorbed and results in a drop in par values. They tested with multiple different colors painted on the back and surprisingly even with blue or white there was still a drop in par
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Here is one of the articles that talk about this, they are testing t5 light in particular here but believe it applies to all light
http://www.advancedaquarist.com/2012/5/equipment
http://www.advancedaquarist.com/2012/5/equipment
I don't have a link...but it does make sense. When light hits the surface of the glass panel inside the tank, one of two things happen, it is either reflected or refracted. A portion of the light hitting that surface on the inside of the tank will be reflected since it it is unpainted, another portion passes through that outer surface, gets refracted, and travels through the glass.
The light that travels through the glass hits the other surface of the glass on the outside of the tank...a portion of that light is reflected back into the tank, and a portion is refracted and allowed to pass completely through the glass. If this surface is painted, you don't get any reflection (or refraction for that matter)...the light is absorbed so you do in fact get less light re-entering the tank. I haven't seen the numbers to see how much of an effect this actually has...overall it's likely a small percentage (and depends on the clarity of the glass), but it makes sense.
Painting an additional panel and putting it on the outside of the tank only absorbs the light that would have passed through the glass completely. So you're not really losing PAR by adding a painted panel on the back of the tank.
Not something I've ever considered before, but pretty interesting overall. As an aside...on my next build I plan on putting together a light box behind the tank This probably won't come together for at least a year tho
The light that travels through the glass hits the other surface of the glass on the outside of the tank...a portion of that light is reflected back into the tank, and a portion is refracted and allowed to pass completely through the glass. If this surface is painted, you don't get any reflection (or refraction for that matter)...the light is absorbed so you do in fact get less light re-entering the tank. I haven't seen the numbers to see how much of an effect this actually has...overall it's likely a small percentage (and depends on the clarity of the glass), but it makes sense.
Painting an additional panel and putting it on the outside of the tank only absorbs the light that would have passed through the glass completely. So you're not really losing PAR by adding a painted panel on the back of the tank.
Not something I've ever considered before, but pretty interesting overall. As an aside...on my next build I plan on putting together a light box behind the tank
This probably won't come together for at least a year tho
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I still dont get how that would reduce the par. From optics theory there is a reflection coefficient anytime the media the light is travelling through changes. Air essentially acts as empty space and does not change the reflection coefficient. If a panel background is the exact same color and shinyness, its reflection and absorbsion would be identical, and therefore the only difference between the two cases is a very small difference in air gap. I can ask some physics professors at mines, but I dont think it would make any difference at all if the panel was coated with the same paint.
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