# Reflective Materials



## camcam (May 18, 2008)

I know Stoney Bud has already done a post on this (link below) outlining what is the most effective materials to use on the grow room walls but what about mirrors? would mirrors be at the top of the list?


http://www.marijuanapassion.com/forum/showthread.php?t=13851


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## snuggles (May 18, 2008)

Mirrors could be on the list but not too high up on it...mirrors absorb a lot of light also.


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## bud.uncle (May 18, 2008)

no no no

mylar is at the top

flat white emulsion on plasterboard is better than mirrors


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## snuggles (May 18, 2008)

Panda Plastic is my favorite and it gets great reflection grades


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## downtown (May 18, 2008)

mylar!


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## massproducer (May 18, 2008)

Mirrors are bad sources of reflective material because they absorb a lot of the light spectrums, and they absorb heat and create massive hot spots


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## camcam (May 18, 2008)

Ok, mylar is the best stuff so that is what I will get, thanks guys...


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## snuggles (May 18, 2008)

I like Panda Plastic better LOL, for many reasons, less heat from reflection, can be reused and doesn't degrade. It's cheaper and only a one time cost. Also it's right there with mylar in reflective ability it's a no brainer IMO.

And it's lightproof too.


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## Growdude (May 18, 2008)

massproducer said:
			
		

> Mirrors are bad sources of reflective material because they absorb a lot of the light spectrums,


 
This is a common misbelief, mirrors reflect at least 90% of all wavelengths beetween 200nm and 5um, with alluminun as this chart shows.

The reason flat white paint works better is that the light is refracted not reflected.


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## massproducer (May 18, 2008)

It has nothing to do with the Aluminum, if this is what you were taking about, it is about the fact that a normal mirror contains glass, it is the glass that robs the lumens and spectrum.

Unlike snuggles I love my mylar, panda film has its place in my room to create light-proof barriers but for reflection nothing really compares with mylar.


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## GreenMan74 (May 18, 2008)

I'm on the panda bus ~


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## Growdude (May 19, 2008)

massproducer said:
			
		

> It has nothing to do with the Aluminum, if this is what you were taking about, it is about the fact that a normal mirror contains glass, it is the glass that robs the lumens and spectrum.


 
Most "bathroom" mirrors are made with alluminum beetwwen the glass.

Not sure about lumens but all the spectum is reflected.
If any of the spectrum was absorbed you would not be able to see that color, A good example would be a plant, the plant looks green because it absorbs all spectrums exept green, only the green is reflected back to your eyes.


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## massproducer (May 19, 2008)

Mirrors are made to reflect all light visible to the human eye, you have to understand that your plants use light spectrums that are not even visible to the human eye.  The glass decreases lumens and some of the other spectrums.  Now aluminum has great reflective properties, that is what make mylar reflective.  Mylar is basically thin plastic that is sprayed with aluminum, this is a mirror in a sense, but it is a mirror for your plants because it has nothing between the thin layer of aluminum and the light being reflected.

And most mirrors are made by taking glass and spraying aluminum or silver and tin on the back.  Then they paint the back and there you have your mirror.  The aluminum coating is not in the middle, it is in the back.  There are mirrors that coat the front of the subsrate like the ones used in hospital rooms but those are very expensive and are made in an entirely different way.


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## snuggles (May 19, 2008)

A little off topic but not completely. I put a mirror outside and two weeks later it's like a window, meaning I can see through it, what the heck is that? LOL I just wasted 50USD on it for my outside garden and I'm baffled or stoned maybe both.


I actually have a mylar room too, I'm not a total mylar misbeliever. I have 3 rooms at my growhouse though and it costs too much to constantly replace as for reflection it's great, wear and tear I don't like it that's all. Another good thread BTW. Some good friendly arguments already.


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## bombbudpuffa (May 19, 2008)

I use panda and mylar.


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## Brouli (May 19, 2008)

mylar #1        but there is new stuff   that i saw NASA use it but is not commercialy avalible     thay say its way better than averything else.


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## bombbudpuffa (May 19, 2008)

Whats it called Brouli?


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## Brouli (May 19, 2008)

im trying to find the article my men  i will finded do


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## snuggles (May 19, 2008)

Brouli said:
			
		

> mylar #1        but there is new stuff   that i saw NASA use it but is not commercialy avalible     thay say its way better than averything else.



These guys at NASA should be growing some good weed soon...between their cutting edge lights and now their reflective material it should be anyday now. I wonder if anyone ever smuggles any seeds in space.


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## Growdude (May 19, 2008)

The visable spectrum is from 400-700 nm, http://eosweb.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html

as you will see in my first chart the mirror reflects from 200nm - 5um

We know the mirror reflects ultraviolet rays, if you ever went fishing in a boat on a sunny day your face gets burned from the reflection of the rays off the water.

The simple fact here is that  refracted light that is superior to reflected light.


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## snuggles (May 19, 2008)

snuggles said:
			
		

> Mirrors could be on the list but not too high up on it...mirrors absorb a lot of light also.



I'm quoting myself, cause I'm wrong. At least I think I am. I have been looking into it and I get two answers
1. Mirrors absorb light
2. Mirrors don't absorb light 

LOL, anyone here have a 100% correct answer? I always recalled from school, that mirrors absorbed light and reflected it...could be wrong though it's been a while LOL. So now I am even more confused then before. I  know colors absorb light, and there is color in reflections so doesn't some of the light get absorbed? 

One thing I do know is in my Grow Bibles it says mirrors aren't good for grow room reflection, but they can be wrong...we all know that LOL. Best grades go to White Paint, Panda and Mylar in my books.


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## massproducer (May 19, 2008)

Your graph says nothing about mirrors, it is about Aluminum, mirrors are not just made of aluminum, they are made primarily of Glass, it is a fact that glass robs lumens and parts of the light spectrum

Read on the make up of glass and mirrors...Here is a passage from wikipedia:

Most mirrors are designed for visible light; however, mirrors designed for other types of waves or other wavelengths of electromagnetic radiation are also used, especially in optical instruments.

Here is a link so you can read more

http://en.wikipedia.org/wiki/Mirror


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## The Hemp Goddess (May 19, 2008)

I have one room done in mylar and one done in panda film.  Even though mylar is more reflective than panda film, it is harder to use, does not wash well, needs to be hung absolutely smooth with no wrinkles, and is not easy to reuse.  All things considered, I like panda film better.


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## md.apothecary (May 19, 2008)

Ahh the debate continues... 

Mylar VS. Panda

Pros/Cons

Mylar is good reflective material, however has been noted that it does degrade after usage. Also, it MUST be as flat as possible to truely reflect, and you do NOT want to have it free hanging as the light will go through the material. It needs to be placed against a solid surface to stop light from penetrating.

Think of a police interrogation mirror (two way mirror). Believe it or not, if you have more light on either side of the mirror that is the portion that is visible. This is very similar to mylar. 

The last con about Mylar is that it's super flimsy and easily torn, then has to be replaced or patched. lol

Panda is thicker, has no light penetration properties to keep light in the grow area for security and reflective purposes. Uses the "white" reflection concept to throw light back at the plants.

I have a grow room that has mylar on the longest back wall, and I use panda on the front as a security barrier/door. 

My plants ever so slightly tend to lean towards the front (panda) reflective material. NOT enough for a definitive conclusion by any means, but just something to consider.


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## Growdude (May 19, 2008)

massproducer said:
			
		

> Your graph says nothing about mirrors, it is about Aluminum, mirrors are not just made of aluminum, they are made primarily of Glass, it is a fact that glass robs lumens and parts of the light spectrum
> 
> Read on the make up of glass and mirrors...Here is a passage from wikipedia:
> 
> ...


 
You are correct about light absobtion, even if it only 5-10%
http://en.wikipedia.org/wiki/Perfect_mirror

What I wanted to stress was it was the fact that the light is reflected not refracted that made mirrors a bad choice.

But I have learned that there is light absorbtion as well. even if all the spectum is being reflected back.


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## massproducer (May 19, 2008)

But all of the spectrum is not being reflected, glass does not transmitt any UV rays as we know are benefical, and they do very bad with far reds which are not visible to the human eye but are used by plants.  Mirrors are designed for visible light, which is light that is visible to humans, namely red, green and blue.


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## massproducer (May 19, 2008)

"Domestic mirrors are not perfect mirrors as they absorb a significant portion of the light which falls on them"

This si from the link you provided, so where did you come up with 5-10% of the light being absorbed?


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## Growdude (May 19, 2008)

Im not trying to argue with you Mass. and ive learned alot.

And I see your point of the light reflecting off of the silver or alluminum THRU the glass and thats what is limiting the wavelengths what is not clear is what wavelengths it does pass, here is a link that talks about silver or aluminum sprayed on glass that passes from 300-1000nm but whats not clear here is if they were going thru glass. 

http://www.microscopy.fsu.edu/primer/lightandcolor/mirrorsintro.html

Ive been reading about aluminum mirrors will reflect more UV and Infrared vs a silver mirror but they dont say how much is reflected.

One thing that is certain is glass passes enough of the spectrum to grow plants, ex green houses, cool tubes and glass plates for light setups, all work fine.
So its not the glass that makes a mirror a bad choice.
From my reading its losses due to absorbtion and that refracted light is more benifical than reflected light, and the hotspot issue also.

Ive put way to much time and thought into this topic I need a brain break.


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## snuggles (May 19, 2008)

I hear you Growdude LOL. Lights and reflective materials just don't catch with me...they hurt my head.

I just read that UV is reflected too, and now someone is saying it is not. If someone can point me to a good site or a good book on the subject I would be happy. Seems to be so much info and it's all different, who's right and who's wrong and why am I so confused? why do I care LOL?


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## massproducer (May 19, 2008)

i hear ya, i am not trying to argue either but yes it is the glass, see when you use a cool tube are you grow in a greenhouse, both of which I do, it is a trade off, because YES you do loose light, but you gain control over your enviroment so it is a fair trade of.  But to loose light to reflect light makes no sense.

I totally agree with you that yes you can grow plants with light shining through the glass but the reason we are trying to reflect the light in the first place is to improve the efficiency.  I think that is where we were butting heads, I am taking about efficiency but you were just talking in general.

1 last thing is that UVB light is 315 nm - 280 nm, FUV or far light spectrums are at 200 nm - 122 nm, these are all used by plants, but are below 300 nm, and most of it would get absorbed because mirror glass is not made to transmitt this light, as it is not visible to the human eye.

Either way I think we both have raised very good points, as refraction is huge when light shines through glass.

I need to smoke a fatty now...LOL

Peace bro


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