Diy hps reflector - Need help
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TeaTreeOil
Well-Known Member
Flat white paint sucks at reflectivity.
Powder coats and enamels of white pigments can offer decent reflectivity, but almost nothing matches aluminum. Nothing! Besides special coatings to further enhance the aluminum reflectance.
If you want long lasting(1/4th century) high-reflective walls, the best, buy aluminum lighting sheet, commercial reflectors are made out of this stuff, it's basically aluminum sheet metal(which is not bad itself) coated with enhancing layers of various materials. The gains are usually around 10% over bare aluminum(20% maximally, mostly in UV), and are without a doubt superior to any Mylar/Foylon, which are comparable to aluminum foil(they have no special coatings, and foylon is aluminum foil).
Yea, the only material I'd suggest is sheet metal(aluminum).
Powder coats and enamels of white pigments can offer decent reflectivity, but almost nothing matches aluminum. Nothing! Besides special coatings to further enhance the aluminum reflectance.
If you want long lasting(1/4th century) high-reflective walls, the best, buy aluminum lighting sheet, commercial reflectors are made out of this stuff, it's basically aluminum sheet metal(which is not bad itself) coated with enhancing layers of various materials. The gains are usually around 10% over bare aluminum(20% maximally, mostly in UV), and are without a doubt superior to any Mylar/Foylon, which are comparable to aluminum foil(they have no special coatings, and foylon is aluminum foil).
Yea, the only material I'd suggest is sheet metal(aluminum).
C
chitownsmoking
Guest
use sheet metal and make like a batwing reflector....and flat white paint reflects well but i donno how well on metal. try chrome spraypaint or some shit
TeaTreeOil
Well-Known Member
Flat white paint doesn't compare with metallic reflectors. Aluminum foil is easily 30-40% better than flat white paint at reflectivity.
Aluminum foil reflects radiant heat. Which is light(radiance). And aluminum foil reflects UV worse than visible light, and IR(heat) better than either of those. These percentages are around 80/90/100 respectively(easiest way to remember it). This is why aluminum foil or aluminized Mylar can be used for solar ovens(high IR reflectivity, it's really about 97-98%, not 100%, close enough). And can even be used to help you tan, about 80% minimum UV reflectivity. As getting your skin tanned is all about UV radiation.
Visible light is a narrow gap between UV and IR within the electromagnetic spectrum. It comprises from 400 nm to 700 nm wavelengths(or 300nm range), and the frequency range is 4.3*10^14 to 7.5*10^14. Both within the same orders of magnitude. Now then, IR and UV cover three orders of magnitude each. And aluminum averages 97-98% and 83-84%(give or take) in these, respectively.
http://origins.colorado.edu/uvconf/white_final/node31.html
"Aluminum has the highest intrinsic reflectance of any known material in the UV above 100 nm, but surface oxidation can severely degrade reflectance below 200 nm."
Aluminum's reflectance is intrinsic. The surface of the material is not a major factor for reflectance.
And that is why oxidation is not really a problem, aluminum oxide is a white metal, and most reflectivity lost due to aluminum oxidation affects UV wavelengths below 200 nm the greatest. Otherwise oxidation doesn't cause much of a problem. As aluminum oxide is stronger than steel and it's a requirement for anodizing aluminum.
Compared to flat white paint, which has basically zero UV reflectivity, and far less IR reflectivity... and near-visible IR and near-visible UV are both plant useful.... White paint just absorbs these... aluminum reflects over 80% of them....
Now then, white enamels and powder coats, can offer up to 90% visible reflectance, and special coatings(MgF2) can boost UV reflectivity significantly. They also coat aluminum with magnesium fluoride, though and other 'german'/TiO2/dielectric, and then it becomes solid ~95% reflective from 300 nm to 800nm. The best dielectric/fluorescent coatings can boost this another 3 to 6 percent. As fluorescent coatings glow, resulting in more light out than in.
Aluminum foil reflects radiant heat. Which is light(radiance). And aluminum foil reflects UV worse than visible light, and IR(heat) better than either of those. These percentages are around 80/90/100 respectively(easiest way to remember it). This is why aluminum foil or aluminized Mylar can be used for solar ovens(high IR reflectivity, it's really about 97-98%, not 100%, close enough). And can even be used to help you tan, about 80% minimum UV reflectivity. As getting your skin tanned is all about UV radiation.
Visible light is a narrow gap between UV and IR within the electromagnetic spectrum. It comprises from 400 nm to 700 nm wavelengths(or 300nm range), and the frequency range is 4.3*10^14 to 7.5*10^14. Both within the same orders of magnitude. Now then, IR and UV cover three orders of magnitude each. And aluminum averages 97-98% and 83-84%(give or take) in these, respectively.
http://origins.colorado.edu/uvconf/white_final/node31.html
"Aluminum has the highest intrinsic reflectance of any known material in the UV above 100 nm, but surface oxidation can severely degrade reflectance below 200 nm."
Aluminum's reflectance is intrinsic. The surface of the material is not a major factor for reflectance.
And that is why oxidation is not really a problem, aluminum oxide is a white metal, and most reflectivity lost due to aluminum oxidation affects UV wavelengths below 200 nm the greatest. Otherwise oxidation doesn't cause much of a problem. As aluminum oxide is stronger than steel and it's a requirement for anodizing aluminum.
Compared to flat white paint, which has basically zero UV reflectivity, and far less IR reflectivity... and near-visible IR and near-visible UV are both plant useful.... White paint just absorbs these... aluminum reflects over 80% of them....
Now then, white enamels and powder coats, can offer up to 90% visible reflectance, and special coatings(MgF2) can boost UV reflectivity significantly. They also coat aluminum with magnesium fluoride, though and other 'german'/TiO2/dielectric, and then it becomes solid ~95% reflective from 300 nm to 800nm. The best dielectric/fluorescent coatings can boost this another 3 to 6 percent. As fluorescent coatings glow, resulting in more light out than in.
Okay, you have my attention! It is refreshing to hear from someone who is so outspoken (and influenced by "the beat of a different drum" as well!). I applaud your obvious knowledge on the subject of "Reflectivety". But this also puzzles me a great deal.
Your statements make a great deal of impact and sense; and yet they fly in the face of what I will call "The Collective Wisdome", or, "Common Knowledge".
First of all, let me say that, my "knowledge" on the subject is probably not much better than "common", and that, my "wisdome" (and experience) with this issue stems from shared "collective" experiences (my own, and others as well). In otherwords, I ain't no freakin' expert on reflective surfaces!
Now, that being said - "The Common Knowledge Reflective Index" is something like the following, approximately:
"Proper" Aluminum - - (up to 98%)
Mylar (and similar) - - (92-96%)
Flate White Paint - - - (up to 88%)
Aluminum Foil - - - - - (about 45%)
Perhaps these figures only apply to PAR light (Photosynthecically Active Radiation), I don't know! But for some reason Aluminum Foil is way down on the list. Hell, aluminum foil looks shiny, it's only logical that it would be more reflective than Flate White Paint - yet I have seen it rated poorly, over, and over, again!
I have my own theory, but I would really like to hear your explaination. "Why is Aluminum Foil bad mouthed so often?", and, "Why do most growers have it all wrong?". What gives??? I know the truth is out there! I'm sure that there are hard core scientific papers out there that would put most of us to sleep (bor-r-r-r-ing!). What I would like to hear is a good explaination in "Semi-technical Terms" (something that a reasonably intelligent person could understand and not get lost!).
Maybe we can re-popularize the use of Aluminum Foil in the Grow Room! Let's "Rock-the-Boat" a little bit!
TeaTreeOil
Well-Known Member
Boobs, and pizza. 
Now that I have your attention.
I don't know why, exactly, but it's all FUD. Attacks that assume you're incompetent, a fuck up, and can't do anything right. Then they flip it around for their own side, and assume you're using the 'best product available'(possibly their own?) and using it "perfectly"(as far as any percentile measures are concerned). I call it a apples to rotten oranges comparison. The best of one material versus the worst of another.
They're usually not consistent. I have no idea where they got them from, or from where their source got them. That's great that some Cervantes or whatever said/wrote something that was probably written for him/her. It doesn't make it true.
So obviously the 'measures' are uhm.. skewed. I'm not selling anything. And I'm not buying this 'collective wisdome'.
Aluminum foil is basically double what you posted, T.H.Cammo. And, yea, around 88% is the maximum for flat white paints that I've seen. Mylar(aluminized) is around 91-92%(avg over PAR). Most Al foils are 88% plus or minus 4%(avg over PAR). Standard 'reflective enhanced Al' is around 95-98%. But usually some areas of the spectrum suffer significantly as florescent compounds are used and they shift light into the desired spectrum(kind of like how CFL/fluoro tubes generate light: UV -> Visible). Or how most(flat white, for instance) paint shifts visible light into IR.
I don't think most growers have it all wrong. Very few actually seem to believe this so called "collective wisdome". Most people who have tried both conclude it works fine, and the opinion on reflective Mylar is similar.
The argument that Mylar is somehow superior to Al foil, or foil creates hot spots more than Mylar or Mylar is as good or better than top of the line reflectors, with claims of "up to 98%" reflectivity. But wait... Mylar gets 100% of its reflectivity from aluminum, and the only spectrum 98% reflected by aluminum is infrared aka radiant heat.
Aluminum foil? The very same, well it's typically said to be 97% IR-reflective. With a .03 IR emissivity coefficient.
Clarity or surface smoothness isn't everything, and make a small difference, because the small difference between the surfaces. Doesn't even really matter what side of the foil you use. The difference is minor.
Aluminum is intrinsically good at reflecting most light(UV, visible, IR, etc). From regular foil, reflective Mylar, emergency blankets, soda cans, satellite dishes, that little metal piece that protects your lighter from the heat, all of these are aluminum.
The "common knowledge" asserts, but fails to explain how aluminum foil is not intrinsically aluminum(most conventional foils are 92-99% Al). Do'h.
There are a million wrong answers, but usually only one correct answer.
Now that I have your attention.
I don't know why, exactly, but it's all FUD. Attacks that assume you're incompetent, a fuck up, and can't do anything right. Then they flip it around for their own side, and assume you're using the 'best product available'(possibly their own?) and using it "perfectly"(as far as any percentile measures are concerned). I call it a apples to rotten oranges comparison. The best of one material versus the worst of another.
They're usually not consistent. I have no idea where they got them from, or from where their source got them. That's great that some Cervantes or whatever said/wrote something that was probably written for him/her. It doesn't make it true.
So obviously the 'measures' are uhm.. skewed. I'm not selling anything. And I'm not buying this 'collective wisdome'.
Aluminum foil is basically double what you posted, T.H.Cammo. And, yea, around 88% is the maximum for flat white paints that I've seen. Mylar(aluminized) is around 91-92%(avg over PAR). Most Al foils are 88% plus or minus 4%(avg over PAR). Standard 'reflective enhanced Al' is around 95-98%. But usually some areas of the spectrum suffer significantly as florescent compounds are used and they shift light into the desired spectrum(kind of like how CFL/fluoro tubes generate light: UV -> Visible). Or how most(flat white, for instance) paint shifts visible light into IR.
I don't think most growers have it all wrong. Very few actually seem to believe this so called "collective wisdome". Most people who have tried both conclude it works fine, and the opinion on reflective Mylar is similar.
The argument that Mylar is somehow superior to Al foil, or foil creates hot spots more than Mylar or Mylar is as good or better than top of the line reflectors, with claims of "up to 98%" reflectivity. But wait... Mylar gets 100% of its reflectivity from aluminum, and the only spectrum 98% reflected by aluminum is infrared aka radiant heat.
Aluminum foil? The very same, well it's typically said to be 97% IR-reflective. With a .03 IR emissivity coefficient.
Clarity or surface smoothness isn't everything, and make a small difference, because the small difference between the surfaces. Doesn't even really matter what side of the foil you use. The difference is minor.
Aluminum is intrinsically good at reflecting most light(UV, visible, IR, etc). From regular foil, reflective Mylar, emergency blankets, soda cans, satellite dishes, that little metal piece that protects your lighter from the heat, all of these are aluminum.
The "common knowledge" asserts, but fails to explain how aluminum foil is not intrinsically aluminum(most conventional foils are 92-99% Al). Do'h.
There are a million wrong answers, but usually only one correct answer.
greengiant69
Member
if you can......... 100% reflect use mirrors!
AbsoluteChron
Member
First of all, mirrors have a black backing and are terrible reflectors.
And don't you guys also think that it might be possible that you haven't noticed a huge difference because you are not growing at a scale or consistency to really judge the difference? The yield difference between reasonably performing reflectors cannot really be that much so you may not even notice a 10% difference. One of you guys should set up a series of tests and go from there...
And don't you guys also think that it might be possible that you haven't noticed a huge difference because you are not growing at a scale or consistency to really judge the difference? The yield difference between reasonably performing reflectors cannot really be that much so you may not even notice a 10% difference. One of you guys should set up a series of tests and go from there...
Mr.McNooby
Member
This is the guide I just found before this thread. Should be exactly what you are looking for 
http://www.icmag.com/ic/showthread.php?t=54817
http://www.icmag.com/ic/showthread.php?t=54817