Ok, As far as hotspots go, its a matter of angles of reflection, If your foil is carefully placed you most likely won't get them, if it is crinkled you might since more light is being reflected to a single point from multiple angles rather than uniformly like you achieve with mylar or Matte/Flat white paint. You will most likely not get hot spots with CFL's or T-5's since they are not putting out as many lumens as MH/HPS blubs, So if you are using those light sources then maybe that is why you have not experienced burns, but many people that have tried aluminum foil on many grow groups reported those results (myself included when I first tried it almost 25 years ago, and that was in the days of incandescent growing with crappy yields). How close your plants are placed to your reflective substance could probably have some bearing on likelihood of hot spots. As far as the aluminum foils reflectivity, that is easy to measure, Take a large box, hang a light in it, line it with foil, then use a light meter to measure the lumens in various locations around the box, then, paint it white, do it again, then line it with mylar and once again check your meter. White paint is better than aluminum foil, Mylar is better than white paint, the only thing aluminum foil would be better than is darkly painted, dirt or bare wood walls. The dollar store mylar that was mentioned is not made for relectivitey but for wrapping gifts so a thinner layer of vaporized metal is applied to the plastic, so you are correct that it does not relect as well and I have not bothered testing it, but i am sure it will perform lower than mylar and probably higher than aluminum foil, but once again with the cavet that I have not tried this meterial out in any of my experiements. And I am not just regurgitating things I have read on forums, I have conducted many of these experments myself, (I am disabled and pretty much a shut in due to a spinal injury so I have the time for research). This has also been amply covered by Jorge Cervantes (who all can agree is probably one of the formost authoritys on cannabis cultivation) in his various works, and I am more prone to accept his findings which were presented with verifiable and impartially conducted research that supports his findings then anything posted by someone on a forum. You do know who Jorge Cervantes is right? This has been debated over and over, what it all boils down to is that yes, aluminum foil will refect light (45-55% refectivity), flat white paint will do it better (roughly 85%) and Mylar even better (around 92% for the quality stuff, not the cheap stuff). For a budget grow, flat white paint is the best option, holds up better and is easier to clean than aluminum foil, can be applied easily, and is WAY cheaper than Mylar. I have great respect for your thread to help the "ghetto grower" but try to give them accurate info. This subject has been debated way to many times and EVERY recognized authority in the field agrees, Aluminium foil is just not a good choice. If you want to contine perpetuating the old wives tale that aluminum foil is great, then feel free and I will feel free to disregard any information you provide in the future as it will be of doubious value at best since you obviously have not taken the time to conduct your own research into the issue. My suspicion is you just cannot conceed being in error, not that you posess irrefutible evidence of your claims. If you are really interested in doing more research into this subject then I suggest you read up a bit on specular reflection and the reflective index of various materials. (and keep in mind, aluminum foil is an ALLOY and not pure aluminum when doing your experiments). I hope you don't think I am trying to attack you personally, I am just trying to put the correct information out there, what you decide to do with it is entirely up to you, but try not to cite stuff as gospel that has already been debunked multiple times. Well anyway, I have weighed in on this enough for now, and if my post was a bit rambling, then I blame it on the weed.... ZeroBuds.
Oh, btw, I forgot to address what I wanted to on reflectivity, but wanted to let someone who can say it far better than I do it so here goes... "The issue with trying to define how much "reflective" a surface is, is that you have to specifically define the wavelength of light or electromagnetic radiation (EMR). Even visible light has a wavelength span of 400-800 nanometers or so. Each wavelength responds differently when passing through into a different medium. Quartz will actually separate out all of the individual wavelengths and create a rainbow. You know this as the prism effect. Your skin might reflect a bit of visible light, but X-rays go right through your skin, where bone has a bit higher reflectance rate for that wavelength--hence why X-rays can help doctors. Then you can take some of the huge satellite dishes that can reflect radio waves. The wavelength of radio waves can be so long that you do not even have to have a solid surface to efficiently reflect the wave. Most very large satellite dishes are made of a mesh of metal instead of a smooth solid surface. If you draw a straight line on a sheet of paper that represents the transition between two media (in our case the wall surface), then you can draw the approach of an incoming light wave. Once it hits the medium (the first line you drew) it will change angles. There will be a defined angle between the ray of light in the first medium and the ray in the second medium. These are called the angle of incidence/angle of reflectance and math can be used to solve them. The angle the light strikes the surface plays a role as to how "reflective" a material is. In case of non-metals (coatings including paint pigments, plastics) the amount of reflected light increases with the increase of the illumination angle. The remaining illuminated light penetrates the material and is absorbed or diffusely scattered dependent on the color. This is why that flat surfaces are better reflectors than most randomly non-flat surfaces since it keeps the angle of incidence high (some non-random surfaces like dimpled 'spectral' aluminum, is quite efficient at reflecting visible light.) To make things further complicated, opaque surfaces like walls, metals etc do not transmit most EMR all the way through the medium. In these cases there is surface reflectance and absorption. Absorption at specific wavelength and reflectance at others is what gives color to the object that we look at. A red object reflects red light and absorbs most/all other visible light. Here again, though, you need to specify what wavelength of light you are dealing with to come up with a "most reflective" surface. Flat white paint appears white to us because it reflects all colors equally well, but since color, including white is a purely human perception, there will be a peak in the overall green light transmission/absorption (since our eyes are most sensitive in the green wavelengths). A magenta paint will absorb green light and reflect a lot of blue and red light. Mirrors and other silvered surfaces, including tin foil, are very good at reflecting visible light without separating out the color, however, people sometimes forget that sunlight, as well as our horticulture lamps, do not only produce visible light, they also produce some UV and also infrared. I think some people also misconstrue the term 'hot spot' as equivalant to 'bright spots'. They are different since they are different wavelenghts of EMR. Since infrared is heat, then we would like a material that reflects the smaller wavelengths of visible light, but not a lot of the longer heat/IR wavelenths. Mylar will reflect IR, but not nearly as much as some materials (the polyester material it is made from does not trap IR like a metalic material will). As with the radio telescope example earlier, there are some materials that efficiently reflect the longer wavelengths of infrared better than others. Most metals, including tin/aluminum foil are quite efficient reflectors of IR, which is why we use it in the kitchen to retain heat within the wrapped product. This is why tin foil leads to 'hot spots'. The bottom line is, yes, tin foil reflects visible light well, but infrared too well to be useful for our purposes. Add that to the fact that it is very difficult to keep it smooth, you lose a lot of it's ability to even reflect the wanted visible light very well (you lose much of the light to scatter rather than direct reflectance). Ideally, we want a material that can reflect visible (and up to UVB) EMR but absorb or allow transmission of IR. Mylar does these things superbly, tin foil, eh, not so much."
Well that all sounds pretty good. But again, I actually USE it, I've USED it before, and have never had a single problem. I have heard again and again how terrible it is, and how my plants are most certainly going to burst in flames from the highly magnified hot spots. Amazing that the actual light, that's a foot away from my plants, doesn't burn them, but somehow the reflection (30% according to everyone on here) of it is truly dangerous. Hot spots may indeed exist, but again, I've personally never seen it, and I only write about what I've seen, not what I've read. Yes I know who Jorge Cervantes is, and how about this, Fuck Jorge Cervantes! I've never seen a single thing that he actually grew. He go's to other people's grows and talks the same old shit everyone else does. Then sells DVD's for HighTimes magazine based on the same old info. I have never seen a single thing he has written or filmed that was at all revolutionary. Foremost authority on cannibus eh? Why doesn't he design his own special products that blows every other company out of the water? Isn't Hightimes the magazine that told everyone how wicked the gen-1 UFO light was? I would say if you sponsored that magazine, they would say whatever you told them to say. And I don't use CFL's or T-8's to flower plants. I have two HID's now (400 and 600w),and will have a third (1000w) probably by the end of the month. I am also building my own light for faster vegging based on my own design and my own research, not because someone else said it would work, but because 'I' think it will work, and 'I' will do my own tests. I have neither inconsistent grows or small yields. I'm as real as it gets. Look through my posts, all I've ever done is try to help people on things I actually know about, and that includes this post. I've only asked one (1) question on here, nobody knew the answer, and then I ended up answering it myself after actually doing my own experiment, not because of someone elses post, or what they had to say. I'm not trashing you, but honestly, you have 4 posts, all directed to me. Did I do something that burns your ass or what? You want to put me in my place? Post some pics of your grow. You're legal right? So there's no problem. And when you take that picture, hold a note in front of your most amazing plant that reads "Fuck You Staci!" Then I'll know you're real.
With you again here staci - we have both used aluminium foil and know it works well - proof of the pudding. And I know that many people think Cervantes is God´s Infallible Vicar on Earth - but to me he is just another dopey Spanish dick - plenty of them, and I live there. At the moment I am getting to read so much garbage, I am saying, come on, let´s see your 2009 grow journal !! Put your money where your mouth is. Zerobuds let´s see yours. Actually, I think we will find that ZERO BUDS is aptly named, that is EXACTLY what he grows. Here is mine - http://forum.grasscity.com/outdoor-grow-journals/280072-cantharis-grow-2009-a-42.html. It will get better as the season goes on. Come to the outdoor growers journal section - look at what Dankohzee, Lots, OldPork and Corto are posting -actual pics of what they are doing this year (and my good self). We are seeing some real plants growing here - not like the zero efforts of the WORDsmiths in absolute beginners - people who offer to advise with your grow but can´t demonstrate their own prowess in any tangible form.
Hahahaha It was the only thing I could find in the root cellar that I could use for scale!! I couldn't bring myself to use an 8-track!! I'll use a 45 from now on!! -Note- if you look at the box on the back shelf it says "Atari Carts 1977-1981" hahahahaha, god I'm getting old!
Not necessary, I'm already silicone enriched!! And self lubricating.... (holy jeez, where is this thread going?)
fucking tighttt!! i likedd this post a lot. since im just starting out the growing procedures and what nots.
My favorite kind. Lifetime oil-less no maintenance needed machine-like.....near mid life...haul ass Da-Kine!!!