Mirrors for growing, definitive answer..

Indole8 said:

outflow fan that will run through moist carbon filled container,

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Moisture drastically reduces effectiveness of carbon filters

Also, while your mirror may be flat to the wall, if you mirror all the walls, you will have hotspots

This actually turned into a pretty constructive discussion a much welcome break to other more opinionated threads, great to have everyone's input and critiques on this.

@BarnBuster I've looked over all the links you provided, the only one that stands out was the second one, he claims silver doesn't reflect blue. http://www.thorlabs.com/images/TabImages/Protected_Silver_Reflectance_12deg_800.gif

The chart is in micrometers, the wavelenghts of visible light is from 390 nm to 700nm which is 0.4 to 0.7 micrometers on the chart, as can be seen silver always stays within 98% throughout that region, I'll give some leeway as that's probably some high tech laser mirror, so let's fall back on 95%.

@2Hearts the hotspots could be a concern, but looking at some work done by our astronomer collegues which also use large mirrors in huge reflector telescopes where they need one 25 meter mirror, they don't use one single piece. The larger a mirror gets the harder it is to keep bends and curves out so what they do is use a honecomb pattern of small 12 inch mirrors and they make a huge one out of it. But in general I agree that introducing large mirrors to line walls is very hard to do and hence why it doesn't work for most people. I was suggesting a few small mirrors which don't have hotspots as a means to duplicate the light source.

@ShirkGoldbrick made me lol. You actually bring up a good point with LEDs as I just bought 6 3watts leds with a driver for my aquarium plants and in the process of assembling them. I would assume weed needs same spectrum as do aquarium plants, I got 3 sets of XL-E cool white 6500 and warm white 3500K, and they are indeed very bright. I'm using an LM317 voltage regulator to drive them, since I built the circuit, I can pushit to the limit with proper heatsinkage, but these LEDs get super hot. Even with a heat sink it's around 70C per set, I'm not sure I can contain that in my little box build. Over my aquarium it's fine since the heatsink is right above water, but in an already hot box I'm afraid I'm going to have a runaway effect.

Yes I didn't think of the light off time, that would make sense why the mirror condensates then. This is a pretty big concern, I'm not worried about electical difficulties as I'll be using CFLs and water can drip on the floor as much as it wants but if the mirror has droplets on it they would act as microlenses and could very well burn the plant. So this is something I will have to consider, I would eigher have to control moisture better, or wipe the mirror everyday. But yea I guess this is one of those things where I have to consider the return value as it could compromise the whole deal.

Before growing MJ in a little box, hydroponically, without ever having done gardening in my life, I thought it would be a good idea to practice, so I went to home dopot got some starting soils and right npk food and bought the closest thing that I thought comes to weed, which is hot peppers. I will try to grow one and see how I can manage the whole thing before I dive into more covert weed op.

@Red1966, sorry didn't see yr post, that might be true but I thought that having moisture the terpenes (which are rather large) would stick to the sides better, so maybe that will counter it? Or do you suggest I just do it dry? Also I use the carbon/zeolite that I buy for my aquarium which sits in the aquarium all the time and it's working really well, can I use that one or should I buy some special one?

edit: @ShirkGoldbrick, just reread yr comment, what do you mean by 200watt LED? The LEDs I have now can be pushed to 5w each (as I said I have 6 of them), but right now I'm running them on 1watt and hellishly hot with a decent size sink on it. Were you referring to equivalent wattage that an incandescent would produce as I can't image I should get 36 of those leds and blast them full power, my dad really won't appreciate the housefire as I'm sure you can image.

Also no glass doens't block UV unless it's coated, and do plants even need UV? Not even that led'd don't emmit it, but CFLs are hard pressed for it also.
Another thing about plant prespiration, if it's prespiring that means that's bad right? It's giving off moisture into the air instead of keeping it? Does that mean the ambient moisture has to be raised if that happens?

Someone was quite correct.
Glass does reduce certain light spectrum's.
UV in a broad range by Borosilicate glass. This glass IS used in light hoods and mirrors!!!! It is also used in the second glass layer in some Mercury Vapor and MH bulbs.

(NEVER use a bulb with out that second layer of glass!!!!)

For that reason, if you intend to use MH lighting for the deep blues and UV spectrum it brings to the table in flower. You need to remove your glass from your hood or change to an open reflector for the gains you are looking for...

Doc

BTW,,,Mirrors? Heavy, and some stoner will break the damn thing and cut them selves or their plants to pieces.

Dr. Who said:

... some stoner will break the damn thing and cut them selves or their plants to pieces.

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LOL friend of mine was going to use big heavy plate glass mirrors he got from somewhere and dropped one of them going down the steps into the basement. Glass shards everywhere. He couldn't walk downstairs in bare feet for quite a while and I was always giving him shit about it. Now, that's the first thing I think of when folks start talking
about using them

Ok this is actually science which is pretty nice. There is a couple of answer to your question.

1. All mirrors steal light at least somewhat. It's just a fact. As a kid anyone remember that album with the triangle glass on it used for light testing? Where the beam of light went threw the glass and did a 45 angle and came out the rainbow on the other side. Now this glass has no reflective surface to it but it still bent the light with a enternal reflection. Now how major of light stays inside the glass bouncing back and forth forever as long as it has a source no one knows but some of it stays in there just going crazy.

2 said that to say this.
I would not be worried about stealing light score or any of that other stuff. It's so small that we can measure it with our eyes. What I would be worried about utlizing the effective range of the light. We all know there is a sweet spot distance from the source to the objective. So you are loosong your sweet spot with distance. Not to say it's not good still to have light but its not as effectively doing its job as point A -B. You are now creating A-B-C-D 1-2 EXTRA steps the light has to penetrate to reach the objective. To test this set up 2 or 3 mirrors in a room bounce a laser pointer from one to another and then at a end point (dead point) on a wall. The beam will be more broken up and larger not utilizing its maximum.

Soo will it help, probability. How much? Depends of the source point A measure to point. B then the objective and check the effective distance to that number.

Haha school sometimes it helps.

If you put a mirror in your room it will save you a lot of work. The plants can look at themselves and can figure what is the best way to stand for maximum light absorption. Additionally it will seem to you that you have many more plants in there than you thought, but remember that no matter how many plants you see you will still only get about a pound, max.

@DrWho maybe somewhat, but most likely very minutely. Huge weed growing greenhouses have them over the roof, our plants stand across the other side of the glass on our window sills, and we can get tan and damage our eyes with uv under uncoated glass. But again do plants really need it in the first place? I'd think they would be more prone to use longer wavelengths of infrared rather then anything else, UV is ionizing to a certain extent.

@LiquidJade lol, you mean a prism? It's got totally different mechanics than a normal piece of glass, it makes the light rays diverge based on the wavelength, in any normal glass light would travel out in parallel rays, maintaining original color.

I'm actually considering using mylar at this point, I'm still not convinced that mirrors woudn't offer better light coverage with less light sources, but it is a hassle installing and there are some fogging issues which you guys brought up that might be difficult to deal with. The only problem is I just came from home depot and the guy in the insulation/plumbing department had no idea what it was. I then asked for a general fire blanket but it looked like it was plain aluminum, I passed. This kinda sucks since I can't really paint the box, did anyone mention shower curtains before lol?

Yes that's what it's cal

Indole8 said:

@DrWho maybe somewhat, but most likely very minutely. Huge weed growing greenhouses have them over the roof, our plants stand across the other side of the glass on our window sills, and we can get tan and damage our eyes with uv under uncoated glass. But again do plants really need it in the first place? I'd think they would be more prone to use longer wavelengths of infrared rather then anything else, UV is ionizing to a certain extent.

@LiquidJade lol, you mean a prism? It's got totally different mechanics than a normal piece of glass, it makes the light rays diverge based on the wavelength, in any normal glass light would travel out in parallel rays, maintaining original color.

I'm actually considering using mylar at this point, I'm still not convinced that mirrors woudn't offer better light coverage with less light sources, but it is a hassle installing and there are some fogging issues which you guys brought up that might be difficult to deal with. The only problem is I just came from home depot and the guy in the insulation/plumbing department had no idea what it was. I then asked for a general fire blanket but it looked like it was plain aluminum, I passed. This kinda sucks since I can't really paint the box, did anyone mention shower curtains before lol?

Click to expand...

Yes that's what it's call. Lol I forgot. Yes it is diff but the basics are the same. It's not like the mirrors we are useing are beyond imperfections nor do not have the same basic principles of that. The basics always stay the same.

Indole8 said:

@Red1966, sorry didn't see yr post, that might be true but I thought that having moisture the terpenes (which are rather large) would stick to the sides better, so maybe that will counter it? Or do you suggest I just do it dry? Also I use the carbon/zeolite that I buy for my aquarium which sits in the aquarium all the time and it's working really well, can I use that one or should I buy some special one?


Another thing about plant prespiration, if it's prespiring that means that's bad right? It's giving off moisture into the air instead of keeping it? Does that mean the ambient moisture has to be raised if that happens?

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The moisture fills the pores in the carbon, thus preventing the volatiles that cause odor from becoming entrapped there. Plants need to transpire in order to live and grow. This allows them to bring nutrients up from the roots.

@LiquidJade hehe happens, anyhow a prism is made to bounce/rerfract light in that way, it's how the glass is layered and it has to be made in a special way to do that, it's usually done to disassemble a light ray into a spectrum. For instance when astronomers look at another star, they pass the white light coming from the star through a prism which shows which light bands are emitted, and they can distinguish between hydrogen, helium etc that way. Normal glass doesn't behave like that, so besides being similar in that they're both glass, they act quite differently. Not to say that normal glass doesn't scatter light a little, it does, if you shine light through 1 meter of thick glass, it will lose intensity and probably be more diffuse, but >1mm of glass that's on the mirror is nowhere near enough for that to matter in any case.

Just trying want to disspel any bad reputation and misinformation surrounding mirrors as grow devices. In general I'm almost certain that with bit of effort a system can be set up that utilizes much less power with mirrors, it's just difficult and has to be maintained properly, but in theory you could utilize much more of the single light source by correctly bouncing it at the right angles to get the perfect grow with a single light bulb.

@Red1966 got it, so I'll keep it dry then, just have maybe 6 inches of it loosely packed in a pvc with fiberglass on each side right before it escapes to the outside, should be pretty easy to do.
So it's a good thing then, that they prespire. I see what you mean, the capillary action forces the water up, makes sense. So then what is the right humidity? Should it be right to the point of where they still prespire or can I get away with as little as possible, ie standard room humidity. I live in nyc by the way, right by the ocean, current humidity is at 26% at 57F. It could be much higher in the coming summer months.

QUOTE="Indole8, post: 11510965, member: 900736"]
@ShirkGoldbrick made me lol. You actually bring up a good point with LEDs as I just bought 6 3watts leds with a driver for my aquarium plants and in the process of assembling them. I would assume weed needs same spectrum as do aquarium plants, I got 3 sets of XL-E cool white 6500 and warm white 3500K, and they are indeed very bright. I'm using an LM317 voltage regulator to drive them, since I built the circuit, I can pushit to the limit with proper heatsinkage, but these LEDs get super hot. Even with a heat sink it's around 70C per set, I'm not sure I can contain that in my little box build. Over my aquarium it's fine since the heatsink is right above water, but in an already hot box I'm afraid I'm going to have a runaway effect.

Yes I didn't think of the light off time, that would make sense why the mirror condensates then. This is a pretty big concern, I'm not worried about electical difficulties as I'll be using CFLs and water can drip on the floor as much as it wants but if the mirror has droplets on it they would act as microlenses and could very well burn the plant. So this is something I will have to consider, I would eigher have to control moisture better, or wipe the mirror everyday. But yea I guess this is one of those things where I have to consider the return value as it could compromise the whole deal.

edit: @ShirkGoldbrick, just reread yr comment, what do you mean by 200watt LED? The LEDs I have now can be pushed to 5w each (as I said I have 6 of them), but right now I'm running them on 1watt and hellishly hot with a decent size sink on it. Were you referring to equivalent wattage that an incandescent would produce as I can't image I should get 36 of those leds and blast them full power, my dad really won't appreciate the housefire as I'm sure you can image.

Also no glass doens't block UV unless it's coated, and do plants even need UV? Not even that led'd don't emmit it, but CFLs are hard pressed for it also.
Another thing about plant prespiration, if it's prespiring that means that's bad right? It's giving off moisture into the air instead of keeping it? Does that mean the ambient moisture has to be raised if that happens?[/QUOTE]


Led only draw about 2/3 their rated power. They're more efficient than hid on a small scale grow. You want 70-80 watts per sqft for max yield if you're using co2 bucket, if not then 50watts is fine but even 30 will work. You could diy some too if you want. They'll put out less heat and the plants can almost touch them.

Did I say perspire? I meant transpire. Read a book about growing plants please.

Indole8 said:

So I known this is a repeat of the dozens of other threads with the same title, and to be fair I have read a lot of them before posting this. The problem I have with the answers is most of them give out wrong information.

While I don't really have any experience growing, I did re-read my physics book chapter on reflectivity. So here are a few misconceptions often posted: mirrors don't reflect as much light as say mylar, that is almost always incorrect, if a mirror has a silver back (which most mirrors these days do) they reflect about 95%+ of the light. This can easily be tested by taking a lux metering of the reflected light, you won't notice a difference from that of the source.

Second less obviously wrong answer is that mirrors don't reflect the right spectrum, that is also incorrect, any reference that I read says mirrors reflect the same wavelength (spectrum) that the source emmits. Logically, if it didn't emit the right spectrum as in if it absorbed some part of it, then the reflected part would lack that color, so the light would be bluish or reddish, common experience shows that wrong.

Third one is that glass in the mirror somehow absorbs/stops/changes the light wave, that is also not true. Metal halide lamps and high pressure lamps have pretty thick glass/plastic covers which are made of much lower quality glass then mirror glass, and they don't pose a problem.

And lastly a more valid argument of hot spots, this might be true, but !, this could be easily corrected with proper tilting/positioning with correct angles. You can't just place them on walls, which is how I think most of these erroneous arguments got started, if you don't tilt them the right way, the reflected rays won't bounce in the right direction!

I've read one thread where a guy said his mirror reflected less then a white wall, I guarantee that he measured from the wrong perspective and had the mirror flat against the wall! If you measure in the wrong spot then it will show the rating of the surface it's reflecting, if it's reflecting a part of the grey ceiling for example it will show the luminosity of the cieling, which could be much lower then the light.

So all in all I'd like to to get some decent answers, or at least a more logical scientific explanation as to why it should not be used. To be honest I think even hot spots are a myth, a flat mirror doesn't focus light, the light rays it reflects are parallel to each other, the mirror has to be curved to focus, and in a small mirror lets say a foot by a foot will have an almost perfectly flat surface, and it could be easily tested just by looking at the reflected light on a clean sheet of paper.

I'm not just asking this for theoretical reasons, I'm starting a one plant grow in a wooden box in my apartment, I can't have more then one or two bulbs as I live with my parents and I can't hit the electric bill by anything more then a few dollars. So I need to duplicate the light source, without actually using more power, so right now single light bulb right overhead and two correctly calibrated, tilted mirrors on each top corner is the plan that im charting out. I'd like to get some decent answers to this one without too much guess work.

Click to expand...

Run your box and then tell us how it works.

Indole8 said:

@LiquidJade hehe happens, anyhow a prism is made to bounce/rerfract light in that way, it's how the glass is layered and it has to be made in a special way to do that, it's usually done to disassemble a light ray into a spectrum. For instance when astronomers look at another star, they pass the white light coming from the star through a prism which shows which light bands are emitted, and they can distinguish between hydrogen, helium etc that way. Normal glass doesn't behave like that, so besides being similar in that they're both glass, they act quite differently. Not to say that normal glass doesn't scatter light a little, it does, if you shine light through 1 meter of thick glass, it will lose intensity and probably be more diffuse, but >1mm of glass that's on the mirror is nowhere near enough for that to matter in any case.

Just trying want to disspel any bad reputation and misinformation surrounding mirrors as grow devices. In general I'm almost certain that with bit of effort a system can be set up that utilizes much less power with mirrors, it's just difficult and has to be maintained properly, but in theory you could utilize much more of the single light source by correctly bouncing it at the right angles to get the perfect grow with a single light bulb.

@Red1966 got it, so I'll keep it dry then, just have maybe 6 inches of it loosely packed in a pvc with fiberglass on each side right before it escapes to the outside, should be pretty easy to do.
So it's a good thing then, that they prespire. I see what you mean, the capillary action forces the water up, makes sense. So then what is the right humidity? Should it be right to the point of where they still prespire or can I get away with as little as possible, ie standard room humidity. I live in nyc by the way, right by the ocean, current humidity is at 26% at 57F. It could be much higher in the coming summer months.

Click to expand...

Experiment!
Take a laser pointer shine it threw a window and hold a peace of paper where the laser would shine to if it was a mirror. You WILL get some reflection from the window. Which means it has reflection properties in it.

2. Ever see the iced over glass or glass with imperfections? Again take a laser pointer and shine it into that object. What did you get? The whole object lights up from light bouncing around inside of it.

Now I never said mirrors were bad it's better the nothing down there. But know it's not the purest light source as for A-B.

LiquidJade said:

As a kid anyone remember that album with the triangle glass on it used for light testing? Where the beam of light went threw the glass and did a 45 angle and came out the rainbow on the other side.

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Pink Floyd - Dark Side of the Moon

Wearing one of the several Floyd shirts I own

LiquidJade said:

Experiment!
Take a laser pointer shine it threw a window and hold a peace of paper where the laser would shine to if it was a mirror. You WILL get some reflection from the window. Which means it has reflection properties in it.

2. Ever see the iced over glass or glass with imperfections? Again take a laser pointer and shine it into that object. What did you get? The whole object lights up from light bouncing around inside of it.

Now I never said mirrors were bad it's better the nothing down there. But know it's not the purest light source as for A-B.

Click to expand...

Please, if you're not knowledgeable behind the science of what you say then don't contribute anecdotal evidence.

In order for light to be fully reflected the angle of incidence must be greater than the critical angle.

A parabolic mirror is the only real practical light solution. I recommend using the same plastic that headlights use to prevent condensation. If you place the light between one and two focal points distance the image will be enlarged if I recall correctly. More than this distance and you concentrate the light into a tighter beam. By doing as I say you will in effect spread the light over the canopy with the best reflectivity possible. I'm talking like a kind of bulb reflector.

Doing a whole room you would need to engineer the whole damn thing including all bulbs and mirrors and good luck with that.

budlover13 said:

Pink Floyd - Dark Side of the Moon

Wearing one of the several Floyd shirts I own

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Must be the best band ever!

budman111 said:

Must be the best band ever!

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Definitely among the greatest imo. Zeppelin is right there with them.

ShirkGoldbrick said:

Please, if you're not knowledgeable behind the science of what you say then don't contribute anecdotal evidence.

In order for light to be fully reflected the angle of incidence must be greater than the critical angle.

A parabolic mirror is the only real practical light solution. I recommend using the same plastic that headlights use to prevent condensation. If you place the light between one and two focal points distance the image will be enlarged if I recall correctly. More than this distance and you concentrate the light into a tighter beam. By doing as I say you will in effect spread the light over the canopy with the best reflectivity possible. I'm talking like a kind of bulb reflector.

Doing a whole room you would need to engineer the whole damn thing including all bulbs and mirrors and good luck with that.

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Wow talk about rude.

And please forgive me I'm only a mechanical engineer. I don't know anything...

I recommend you test this about the condensation head light theory... Make a pin hole in the back of the head light to allow air into it. Then put it back in your car. And it WILL condensation because its not the exterior or the material use that prevents condensation but the air lock inside the head light. Ever wonder why when you change a head light sometime it fog up? Cause it's not sealed again... Same applies when there is a crack in the plastic. The head from the bulbs and the cool air being introduced makes water. The same as in the mornings.. called dew....

What you are talking about is reflector therohy. And yes if you place a small image and do that it will become larger. Like a movie projector. Now if you move it back the light becomes dimmer wondering why? Because it's deplaced more. Which means you loose effective light area... This is called lumens. Higher the lumens the brighter the image and the distance between A-B can be increased with LESS light loss in the sweet spot.

Lol so again if you need help with the "enginnering" of cretin things let me know I'll explain it. It's what I do.

"Please, if you're not knowledgeable behind the science of what you say then don't contribute anecdotal evidence. " TY...

Certain* good stuff tho

LiquidJade said:

Wow talk about rude.

And please forgive me I'm only a mechanical engineer. I don't know anything...

I recommend you test this about the condensation head light theory... Make a pin hole in the back of the head light to allow air into it. Then put it back in your car. And it WILL condensation because its not the exterior or the material use that prevents condensation but the air lock inside the head light. Ever wonder why when you change a head light sometime it fog up? Cause it's not sealed again... Same applies when there is a crack in the plastic. The head from the bulbs and the cool air being introduced makes water. The same as in the mornings.. called dew....

What you are talking about is reflector therohy. And yes if you place a small image and do that it will become larger. Like a movie projector. Now if you move it back the light becomes dimmer wondering why? Because it's deplaced more. Which means you loose effective light area... This is called lumens. Higher the lumens the brighter the image and the distance between A-B can be increased with LESS light loss in the sweet spot.

Lol so again if you need help with the "enginnering" of cretin things let me know I'll explain it. It's what I do.

"Please, if you're not knowledgeable behind the science of what you say then don't contribute anecdotal evidence. " TY...

Click to expand...

LiquidJade said:

Wow talk about rude.

And please forgive me I'm only a mechanical engineer. I don't know anything...

I recommend you test this about the condensation head light theory... Make a pin hole in the back of the head light to allow air into it. Then put it back in your car. And it WILL condensation because its not the exterior or the material use that prevents condensation but the air lock inside the head light. Ever wonder why when you change a head light sometime it fog up? Cause it's not sealed again... Same applies when there is a crack in the plastic. The head from the bulbs and the cool air being introduced makes water. The same as in the mornings.. called dew....

What you are talking about is reflector therohy. And yes if you place a small image and do that it will become larger. Like a movie projector. Now if you move it back the light becomes dimmer wondering why? Because it's deplaced more. Which means you loose effective light area... This is called lumens. Higher the lumens the brighter the image and the distance between A-B can be increased with LESS light loss in the sweet spot.

Lol so again if you need help with the "enginnering" of cretin things let me know I'll explain it. It's what I do.

"Please, if you're not knowledgeable behind the science of what you say then don't contribute anecdotal evidence. " TY...

Click to expand...

I apologize for being rude, and you're correct about the headlight being sealed. However I believe that the heat capacity of the thin plastic is so low that it will maintain the temperature of the ambient air and not cool to the point of condensation. If I'm wrong, then applying a spray foam insulation to the back will ensure that it stays warmer for longer and then definitely wont condensate.

If you have a headlight with a hole in it and moist air is allowed to get inside then as soon as you start driving the inside of the fixture will heat up but driving down the road the outside will be air cooled causing condensation. Likewise, once you stop the outside will cool faster as it is exposed to the cooler outdoor air and again will condensate.

I also don't believe we're even on the same page with the application of the mirrors. I know OP or others have thought and or have lined the walls with regular mirrors, and while this would work it would also be a headache to look at and and it's not worth the cost.

Parabolic mirrors around the perimeter would work, but only if the room was designed so that every single light was reflected in a manner in which the light was focused on the plants from every mirror, also avoiding concentrated beams on any small space...like I said, that would be a nightmare to design.

Yes we know that light is lost through reflection. You have the reflectivity of the material itself to take into account and I imagine that is compounded by the inverse square law of HID, CFL type lights (I wont get into LEDs and beam angles). I'm not talking about using a parabolic reflector to channel a flashlight beam into the grow box. I'm talking about reducing wasted light with mirror technology more effectively than it is done with traditional reflectors.

Instead of the traditional reflectors used by most HID lights I believe using one made with headlight reflective material and with the source somewhere between the first and second focal points one could more accurately place wasted light on the canopy in a manner which will not cause hot spots.

I haven't actually punched any numbers into 4fd=r^2 to see what dimensions would be ideal, but I imagine that it could be done in an effective way. This would vary with the planned light source strength in order to focus the most even amount of light over some standard foot dimension that is used in a plant layout in order to focus whatever intensity lightsource at ~70 watts per sqft to get a good balance between sativa and indica varieties.