Mackaveli420
Well-Known Member
Whats more reflective? Regular old tin foil or regular old flat white paint?
More Reflective? Tin Foil Or flat White Paint?
- Thread starter Mackaveli420
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Mackaveli420
Well-Known Member
yea I heard that too.
thx
thx
stilltokin
Well-Known Member
yea a white wall is the safest and good for reflection. Lots of people use mylar but then again it could cause heat spots if it has wrinkles in it. I just use my white walls.
diemdepyro
Well-Known Member
I can not swear which is better but white paint is easier.....much easier.
Mackaveli420
Well-Known Member
what about panda film? is it reflective like paint and is it heat resistant?
smppro
Well-Known Member
foylon, mylar, panda film, white paint, not ever use tin foil, in that order. I use flat white paint, i think it is like 88% reflective where mylar would be like 95%. But paint is cheap, available everywhere. Mylar you have to worry about wrinkling and tearing. A lot of people say that the wrapping paper with the backside that looks like mylar is actually mylar, but i dont know if that true
smppro
Well-Known Member
Sorry thats absolutely wrong, foil has the worst reflective properties, about 50-60%, no where near anything else, especially white paint
stilltokin
Well-Known Member
go for white paint, it wont ever cause fire and with papers like mylar and all that it gets really loud and annoying if the wind from the fan gets behind em. I did that and I couldnt go to sleep coz i could hear it crinkle outside my room
OregonMeds
Well-Known Member
Yep completely wrong. Foil is 50% reflective. The problem with hotspots isn't that it reflects too much light it's that it reflects heat better than it does light.
There is a reason it's only made for cooking and you don't normally see aluminum foil on the shelves for any purpose other than just cooking.
A really good flat white paint is hard to beat. Even mylar that is brand new but not pulled perfectly flat is not as efficient as flat white paint. Dirty mylar is way less effective. And so on.
Behr Ultra Pure White FLAT wall paint is a really good one, or match that with a cheaper brand.
indianaman
New Member
how bout sheets of cut styrofoam? i've heard that works really good if you have enough. fire hazard i think kinda.
TeaTreeOil
Well-Known Member
But heat is light. Plants use *some* UV and IR, afaik! Aluminum does this far better than paint, as you state.
Shiny aluminum foil is between 85-95% reflective(the dull side is ~80%, Wikipedia). Flat white paint is basically the same reflectivity as the dull side(if you get the right paint, and can paint it properly, a skill in itself). Ideally you glue foil to cardboard, or another flat surface. Don't even try fancy shapes(curves,cones). Keep it wide and flat, shiny-side out. You could probably buff the foil surface for better results.
The conventional 'wisdom': "It's a bad reflector.. so use the less reflective side! No, no, no don't use it at all!"
The truth: it's a highly efficient reflector just shy of mylar, and better at reflection than generic white paint. Maybe a reflective paint would be better. The problem is people don't use foil correctly, and it's somewhat difficult to handle.
You really want a back reflector. You can increase directed usable light by 30-40%! Metal/specialty paint seems to be the best choice.
However coating distance surfaces will not help much. At greater distances it just matters less. White paint is great for distances greater than a few inches. Plus it's easier(maybe).
I had one box with aluminum foil just on the top(glued on) reflecting back(1" away or so from light), and another identical box/lights with just white paint. The aluminum foil seemed to promote a more powerful and more balanced light spread and even temperature. I don't know what these 'hot spots' are.... I've only used floros.
EDIT: White enamel paint has 80-85%*. White *POWDER* coat is where you can hit 90%*. Your bucket of white paint is probably well under 85%. Wikipedia lists shiny aluminum foil at 88%.
Also, the shape of the reflector matters more than the material(given aluminum, mylar, or white paint)*!
But sheet aluminum would be a much better idea, it's insanely cheap, mirror-finished, and rigid enough to move around a bit, doesn't crinkle. Sheet aluminum has been used in the lighting industry for decades*.
*Source: Applied Illumination Engineering By Jack L. Lindsey
http://books.google.com/books?id=0d7u9Nr33zIC&pg=PA483&lpg=PA483&dq=aluminum+reflector++comparison&source=web&ots=WyLgL914LS&sig=P35u62EonubVtf7JTA444k0nDeo&hl=en&ei=G9-RSeX0EYmMsAPdk4StCw&sa=X&oi=book_result&resnum=3&ct=result
onenumcat
Well-Known Member
that was the original question. my answer, 'the foil is much, much more reflective than white paint...which is why it creates hot spots and burns your plants.
if you must use foil, I've heard the dull side facing your plants is better than the shiny side.', was correct, thank you very much. he didn't say he wanted to use foil to reflect light on plants. I was correct, but didn't want to have to defend myself alone.
a white surface reflects wave energy and diffuses it(if the surface is rough, like matte paint, while a black surface absorbs light(radiation actually) and converts its energy to heat, thereby radiating heat. a shiny metal, especially a 'silvered' one, reflects much more light than a white surface, but also most of the heat, the surface is smooth. which is why a dulled or burnished(not smooth) silvery metal is way better than a white surface...for reflection...that is why hoods/reflectors, for plant lights, are a dull silvery metal, whatever it's material, not white, and they're sold for redirecting light, only...and for no other purpose. and that is why, when you shop online for a hood, it ain't white inside. or go to the garden store, you will not find paint to be used as a bulb reflector.(however, some shops may sell it to paint a dark surface near your grow, so the dark surface won't absorb the light and produce heat)
I did state that the foil will cause hotspots...hot, as in heat, being the key part of that word...it will burn your plants!
thanks for the good info and the references, but not quite accurate about 'light n heat'. shiny aluminum is great for reflecting light/heat, ie; street lamp, spot light, flachlight, headlight, disco balls, etc. etc, but for the same reason, shitty for plants...it burns them by refocusing the wavelengths to a smaller area, intensifying it. the research I found states, 'Infrared radiation is popularly known as "heat" or sometimes "heat radiation", since many people attribute all radiant heating to infrared light and/or to all infrared radiation to being a result of heating. This is a widespread misconception, since light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared light from the Sun only accounts for 49% of the heating of the Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths'.
http://en.wikipedia.org/wiki/Infrared
'cool'<----------------------------------------------------->'hot'
the sun is 'hot' because it emits radiation.
infrared is 'hot' because the wavelengths are much longer than say >300nm, which is like a purple light(black light). it's wavelengths are short. short wavelengths don't 'penetrate', they're too weak, so aren't absorbed and produce little or no heat. infrared resides at <700nm up to about 3000nm, far beyond red light(which is quite hot and is also the end of visible light for humans @800nm or so). the further you go down the spectrum the cooler 'light' becomes, because it's not actually the 'light' that is hot, but rather the radiation. 'light is a by product of radiation. the rate, and amount, of wavelengths(radiation) being absorbed by a substance, determines how 'hot' it gets. there are other factors also, I'll not get into them...it's quite complex. the 'light' from the sun, in space, is 'cool', as long as it doesn't strike anything that reflects it's energy. if something was actually blacker than black, and there are things like that, some made by man, like dark matter...(or a black hole...which isn't really black at all, lol, the gravity is what pulls light particles in...), it would absorb all particles\wavelengths and give nothing off in return...
http://www.core77.com/blog/materials/new_black_material_is_blacker_than_black_8699.asp
http://www.newscientist.com/article/dn3356-mini-craters-key-to-blackest-ever-black.html
short version is 'white' doesn't absorb most wavelengths, so doesn't convert that radiation to heat. 'black' does do that. reflectivity is determined by the surface also, not only the color. a shiny black surface will reflect light. a shiny surface reflects wavelengths, it cannot 'absorb' wavelengths because the surface is too smooth, much smoother than say, white paint, except for gloss. gloss reflects a lot of wavelengths, in one direction, causing 'hotspots', just like polished metal because the surface is smooth. a 'matte' surface will diffuse light in many more directions than 'glossy' because the surface is not smooth. finally, the heat of light is caused by friction, waves or particles striking a solid or even semi-solid, like air or water.
http://answers.yahoo.com/question/index?qid=20071207101851AA4qBqf
http://potatoland.com/glart/week4/GLART_4_sphere_light_color.java
there are ways to produce heatless light.
here are a few links;
http://scifun.chem.wisc.edu/HOMEEXPTS/Chemilum.html
http://www.sandia.gov/media/NewsRel/NR2002/tungsten.htm
http://www.newton.dep.anl.gov/askasci/eng99/eng99569.htm
TeaTreeOil
Well-Known Member
So why are most high-end reflectors/commercial grow reflectors dimpled anodized aluminum with ~95% reflectivity? And the rest(90%?) are just plane aluminum, sometimes powder coated. The reflectively fairs 85-95% from 200-1000nm except a dip around 800 or so down to 85%. Just look at it! http://www.answers.com/topic/reflectivity
Any thoughts on ideal lux? As for heat, try a fan. In a small grow the reflective efficiency of aluminum (sheet or foil) could be pretty beneficial over alternatives. If you got crafty you could bend some thicker sheets into your own fixtures/reflectors. If you really get excited about it, powder coat!
http://www.4hydroponics.com/lighting/reflectorsSS.asp
"textured aluminum" aka "crinkled up and re-flattened aluminum foil" hmmmm
Here's an interesting article: http://www.usu.edu/cpl/research_spectral10.htm
Final one: http://ioannis.virtualcomposer2000.com/spectroscope/elements.html <-pretty good, but lengthy
Any thoughts on ideal lux? As for heat, try a fan. In a small grow the reflective efficiency of aluminum (sheet or foil) could be pretty beneficial over alternatives. If you got crafty you could bend some thicker sheets into your own fixtures/reflectors. If you really get excited about it, powder coat!
http://www.4hydroponics.com/lighting/reflectorsSS.asp
"textured aluminum" aka "crinkled up and re-flattened aluminum foil" hmmmm
Here's an interesting article: http://www.usu.edu/cpl/research_spectral10.htm
Final one: http://ioannis.virtualcomposer2000.com/spectroscope/elements.html <-pretty good, but lengthy
onenumcat
Well-Known Member
anodized only protects the metal from corrosion, has nothing to do with reflectivity. but you're correct, which was the point I was making, a textured or not shiny aluminum is far superior to a textured white. however, the shiny aluminum is not better than 'glossy white', which ain't to 'hot', lol, either. my hoods are dimples and 'scratched' all over, they've been burnished, the shine has been removed, and more. I'll get a pic up, but the lights are on now and all you'll see is 'white' light. a powder coat is good...if it's white, it reflects light, but it's main purpose, as being textured, is to diffuse light. it doesn't reflect heat, good.
the aluminum will reflect more heat, even non-shiny like mine.
simply, the flatter a reflective surface is, the more light, and heat, it will reflect, in one direction. surfaces, that are white or light colored, and textured, will reflect light in a diffused pattern, covering a larger area, emitting less heat. a pure reflective surface, no color, silvered, reflects in one direction, and heat also, and the metal itself will radiate heat. a textured aluminum, will diffuse light and heat, however it will also radiate heat. no matter what, unless its painted, then the 'surface' isn't aluminum, its paint...aluminum will always be hotter than a painted surface. but is does 'reflect' light better than white paint.