Hands down, white paint. http://forum.grasscity.com/general-indoor-growing/165331-getting-most-your-lights.html
oh god listen to the guy saying to use flat white paint! never use aluminum foil - it creates hot spots! edit: if you do decide to use the foil (though i cant see why - paint is simple and permanent, where foil is expensive and tears), but anyways if you do use it - use the non-shiny side for reflection, as the dull side is alot less likely to create burning hotspots
BULLSHIT - total old wives´ tale - doesn´t do anything of the kind !!! I have been waiting for some fuckwit to come up with this rubbish - it always gets repeated, for some unknown reason. I have used it for ages and NEVER found anything of the kind. Neither have you, odin, cos it DOESN´T happen !! Al foil is a highly reflective material, available anywhere and dead cheap, with no drawbacks to its use whatever.
Here we go again Cantharis! Aluminum foil works very well. The hot spot theory is a bunch of bullshit, I don't care where you heard it, or who wrote it. White paint does work, and mylar works very well and is tougher than aluminum foil, but if you don't have any, use foil, it's fine, it's cheap, and it reflects light very well.
I personally do not use, or suggest the use of aluminum foil for a grow room. It is difficult to apply smoothly and to cover a decent size room would cost as much as reflective mylar, and much more than a gallon of good flat white exterior latex. As for the hot sspots, reflective mylar can produce hot spots is not applied smooth, and wrinkles will direct the light, not reflect it, which is where the hot spot myth came from. It does not create hot spots, it directs the light. In indoor growing, you want a even reflection to increase and maxinise the amount of light a plant will get and increase the area where a plant receives light. It also keeps the light inclosed within a specific area. If used correctly, and applied without wrinkles, aluminum foil can work, however IMHO it is too delicate to apply evenly and smooth. less
I don't know how much aluminum foil costs where you live, but I did a 10'x10' wall for about $3. I had every intention of replacing it with mylar, but it worked so well I just left it. I was very careful when I put it up and didn't wrinkle it at all. It still looks damn near perfect.
¿Qué? Laws of relection apply: angle of incidence = angle of reflection, both rays being in the same plane. Trouble with this sort of thread is people who know no physics start repeating BS they have read, and of which they have no experience.
i tried foil on my grow box (i cant see it doing any harm like hotspots its not a magnifieing glass) the only problem i had was applying it as it wrinkles i took it down cause it looked messy lol and just dug out some flat white paint we had in the garage. if you have the patience to apply foil and are not bothered about it looking messy go for it if you like me and like thinks neat clean and tidy go for paint
I think it depends on the foil. 'Reynolds' brand is a very thick gauge, and I used scissors to cut it since trying to use those little metal teeth on the box just wrinkle it. Dollar store type foil is very very thin, like a piece of paper, and almost plasticy feeling (that's the only way I can describe it). I just took the whole roll out of the box, rolled it out on the floor into the lengths I needed and cut them one at a time, then I put a piece of tape on both sides and carefully placed them on the wall, from bottom to top, one overlapping the next. I finished it by making a duct tape 'frame' around the whole thing. Took 10 min total, and had no wrinkles. If it ever rips, I'll probably replace it with mylar, since it's tougher. But I haven't been to a hydroshop in a good while, and I just found my soil at a local greenhouse, so that cuts out my bi-monthly visits. Besides, hydroshops prices are getting out of hand anymore and I'm avoiding the temptation to blow a few hundred more dollars on things I probably don't need, or could buy elsewhere considerably cheaper.
Granted, it is still reflection, however the reflection is still directed by any creases, wrinkles, or bends in the material used, mylar is no different. To get optimal results, one must create an even reflection of light, any type of wrinkle or bend will waste light. I really do not know where this hot spot thing started, but I do know that the smoother the reflectant the more the lights reflection is optimized. When light is reflected, it will follow the direction in which the surface bends, so even with poorly installed mylar you can lose usable light. I know the laws of physics, shit I have a BA in Technology and 3 AA's all relating to technology, design, and electronics, so I kind of think I had to pass physics to grad w/ a 3.86 gpa. Maybe it was not explained well, but the reflection can be directed to a point where you are actually losing useable light in a room, so the reflections are directed by the bends or wrinkles and are directed to points that do not enhance which is the sole purpose of using reflectants. less
If a small current is applied(no more than 100 volts)the hot spots will be a thing of the past,but you must use a high density plastic wire to apply it.