The Mirror Enigma

laserbrn

laserbrn

Well-Known Member
laserbrn said:
Just did it....and no, no it's not. And this is just my crappy bathroom mirror. It's not noticeably dimmer.
Click to expand...

Just for shits and giggle I'll try hooking up my 250w lamp tonight and shining it 1 ft away from my light meter. Then I'll shine my lamp at the mirror from 6" away and measure it from 6" away (total of 12" distance traveled). It certainly has my curiosity up.

I may just rig something up this weekend to test all sorts of surfaces, fuck it.

I've got some extra space and everythign I need. I'll just rig up some plywood and use a lightmeter. I KNOW that it's not the most accurate way, but I don't have anything to measure wavelengths and to determine what spectrums were reflected best.

But it will at least rule out the "it just doesn't reflect light well" line of thinking or confirm it.
 
707Humboldt$born707

707Humboldt$born707

Member
I think it will reflect better than anything but its not going to disperse the light at all

I did read in High Times that mirror dont work for this very reason
 
laserbrn

laserbrn

Well-Known Member
707Humboldt$born707 said:
I think it will reflect better than anything but its not going to disperse the light at all

I did read in High Times that mirror dont work for this very reason
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It should disperse the light at the same angle that it was hit at. I'm thinking that the problem with not dispersing the light is that you'll really just be lighting the bottom of the plants. Not the lower leaves, the actual bottom. It's hard to explain,but if the light hits anywhere on the wall more than half way down the plants it will be reflected down to the ground. But that doesn't answer the question of "What if we used a lot of very small mirrors at various angles"?

Just curious. Obviously painting the wall is easier, haha
 
saycheese

saycheese

Member
luckydog82 said:
Don't get me wrong mirrors are highly reflective or else they wouldn't be mirrors but silver will never be as white as white and flat white releases the light back in all directions unlike a mirror which will reflect the light in 1 direction
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WRONG. please stop saying things as if they are fact. a mirror makes light appear if it is coming from 1 direction but if you hang a cfl and move around yourself then why can you still see the cfl reflected in the mirror. jesus man use some common sense. of course focused light like a laser will do exactly what you are referring to but no one is using focused light to grow otherwise you really would burn your plants.
 
saycheese

saycheese

Member
i have a light meter coming and i will test my light readings on my grow room covered in mylar, white paint and mirrors. you can buy door mirrors from Walmart for $5 each that are 12" x 48". I used a dremel to cut a few up so i don't block my intake or outtake fans. as soon as I can I will provide raw statistics on how well they all worked in my specific application. obviously a large room would be very hard to cover each wall and mirrors would not necessarily be a good choice but its not like mylar doesn;t cost money. if you pay $200 for an hps system why skimp on reflective surfaces. I want no useable light lost and the reason why this has me going is because when I tested mylay and white pain vs a mirror just eyeballing it I noticed a significant difference in the amount of brightness reflected over a large area not just focused
 
AllAboutIt

AllAboutIt

Well-Known Member
all you have to do is take a small mirror get a ray of sun to hit it and you will see that it makes a near "mirror image" :neutral: of the light being reflected directly on the wall (in your case a square) then take a piece of white cardboard or even better mylar... and you will see that it reflects lights evenly and prob lite up the room a bit this is not my cooked up or copied conclusion its FACT, if mirrors were better for reflecting light wouldnt they be used in pro grow ops in europe?... you would have heard via word of mouth that mirrors reflect/disperse light "best". Dont get me wrong thinking outside the box is needed but.... which is better a nickle plated piece of glass or something made by those silly people who fly into space?? :clap:

I know, lets use a magnifying glass and mount it under our lights to get a more intense light shinning on the canopy.....yea thats the ticket!!
 
riddleme

riddleme

Well-Known Member
Wellthe best news is that you are not alone on this issue, it has been beat to death so much by so many that a few simple googl;es like

light wavelengths absorbed by mirror

and

efficiency of mirror reflecting light

brought up several mj forum post lots of ask a scientist, lots of yahoo answers making it difficult to find real or good answers,,,,,,,,,,,,,,,,,,

But I found them :eyesmoke:

from Edmonds a company that selld optics and mirrors

An example of a second surface mirror is a common bathroom mirror. A second surface mirror is usually not preferred over a first surface mirror in most applications due to many inherent characteristics. A second surface mirror suffers from lower reflectivity due to absorption by the glass (especially in the UV and IR). In addition, there are often ghost images due to two reflections (one from the glass, one from the coating) and an increased optical path length since light passes through the glass twice (once to reach the coating and once to reflect back). A second surface mirror does have the advantage of increased protection of the coating. If the coating is very delicate or the environment is harsh, a second surface

link,
http://74.125.155.132/search?q=cache:3Rx-jeuqLm8J:www.edmundoptics.com/technical-support/optics/gratings-and-fibers/mirrors/faq-on-optics-part-2-polarizers/+efficiency+of+mirror+reflecting+light&cd=55&hl=en&ct=clnk&gl=us

this was interesting,,

No, regular mirrors reflect the entire range of visible light. With no tinting to absorb extraneous wavelengths, mirrors will take any wavelength of light and bounce it back off their surface. Just as any "white" object would do. The difference, though, is this: mirrors bounce light back in a very specific pattern.
So if you put a piece of white paper and a mirror next to each other on a table, they certainly won't look the same. The piece of paper will bounce electromagnetic radiation back in a scattered, haphazard fashion, one that our brain perceives as white. The mirror will bounce the exact same range of electromagnetic radiation back off its surface, but will do so in an organized fashion that produces a reflection of the light source, rather than white light. But the simple fact is that neither the mirror nor the paper is absorbing anything along the visible spectrum of electromagnetic radiation. So in terms of how we normally define color, they're both "white."

found here,
http://everything2.com/title/What+color+is+a+mirror%3F

this statement was made in context in a paper about making a better mirror

Ordinary mirrors of silver-coated glass reflect light from different directions, but aren't very efficient because they absorb some of the light as well as reflect it.

link
http://www.photonicsonline.com/article.mvc/3M-Creates-Highly-Efficient-Polymer-Based-Mir-0002?VNETCOOKIE=NO


My own experiment was very simple and did not involve a light meter (so I am curious about other posters test),,,I took a very bright flashlight and shined at a mirror and at a sheet of mylar, the mirror reflected the beam of light back at me and it showed on the opisite wall as a beam.
The mylar simply just lit up no beam was visible on the mylar or the opisite wall and (most notable) the entire sheet of mylar lit up the mirror did not

I would suggest that it is well known that there is a benefit to have UVB in our areas and since mirrors absorb uv rays I would guess that it is the reason that mirrors are considered bad?
 
That 5hit

That 5hit

Well-Known Member
i love mirros they just cost to much
mirros are used in allmost anything you can think of
they do reflect what is exactly in front of them
and they do not disperse light
this is the reason they are used in sat, telescope, lazers, and ever other equipment
the distance of an object in a mirror is twice the distace to the object being reflected
meaning if i stand infront of a mirror that is 5ft away
then the reflection of me is 10ft away from the real me
but this is true for any reflective mat. not just mirrors
mirrors give a cleaner reflection then anything else thats why nasa uses them
the only problems with mirror's are
1 they cost to much
2 they are to heavy
but other then that they re the best
high grade mylar is just a mirror without glass (this statement alone may cause a war)
 
luckydog82

luckydog82

Active Member
riddle me that explains it better than i did thanks for clearing that up who wants to use mirrors anyway risking breaking 1, 7 years bad luck you know i,ve already broke 5 in my life and i'm 1 unlucky fuddermucker lol
 
saycheese

saycheese

Member
riddleme said:
Wellthe best news is that you are not alone on this issue, it has been beat to death so much by so many that a few simple googl;es like

light wavelengths absorbed by mirror

and

efficiency of mirror reflecting light

brought up several mj forum post lots of ask a scientist, lots of yahoo answers making it difficult to find real or good answers,,,,,,,,,,,,,,,,,,

But I found them :eyesmoke:

from Edmonds a company that selld optics and mirrors

An example of a second surface mirror is a common bathroom mirror. A second surface mirror is usually not preferred over a first surface mirror in most applications due to many inherent characteristics. A second surface mirror suffers from lower reflectivity due to absorption by the glass (especially in the UV and IR). In addition, there are often ghost images due to two reflections (one from the glass, one from the coating) and an increased optical path length since light passes through the glass twice (once to reach the coating and once to reflect back). A second surface mirror does have the advantage of increased protection of the coating. If the coating is very delicate or the environment is harsh, a second surface

link,
http://74.125.155.132/search?q=cache:3Rx-jeuqLm8J:www.edmundoptics.com/technical-support/optics/gratings-and-fibers/mirrors/faq-on-optics-part-2-polarizers/+efficiency+of+mirror+reflecting+light&cd=55&hl=en&ct=clnk&gl=us

this was interesting,,

No, regular mirrors reflect the entire range of visible light. With no tinting to absorb extraneous wavelengths, mirrors will take any wavelength of light and bounce it back off their surface. Just as any "white" object would do. The difference, though, is this: mirrors bounce light back in a very specific pattern.
So if you put a piece of white paper and a mirror next to each other on a table, they certainly won't look the same. The piece of paper will bounce electromagnetic radiation back in a scattered, haphazard fashion, one that our brain perceives as white. The mirror will bounce the exact same range of electromagnetic radiation back off its surface, but will do so in an organized fashion that produces a reflection of the light source, rather than white light. But the simple fact is that neither the mirror nor the paper is absorbing anything along the visible spectrum of electromagnetic radiation. So in terms of how we normally define color, they're both "white."

found here,
http://everything2.com/title/What+color+is+a+mirror%3F

this statement was made in context in a paper about making a better mirror

Ordinary mirrors of silver-coated glass reflect light from different directions, but aren't very efficient because they absorb some of the light as well as reflect it.

link
http://www.photonicsonline.com/article.mvc/3M-Creates-Highly-Efficient-Polymer-Based-Mir-0002?VNETCOOKIE=NO


My own experiment was very simple and did not involve a light meter (so I am curious about other posters test),,,I took a very bright flashlight and shined at a mirror and at a sheet of mylar, the mirror reflected the beam of light back at me and it showed on the opisite wall as a beam.
The mylar simply just lit up no beam was visible on the mylar or the opisite wall and (most notable) the entire sheet of mylar lit up the mirror did not

I would suggest that it is well known that there is a benefit to have UVB in our areas and since mirrors absorb uv rays I would guess that it is the reason that mirrors are considered bad?
Click to expand...
excellent post. obviously not verifiable by you or I, it at least explains itself in a logical maner rather than saying absurdities like "mirrors reflect images not light". I am still planning on measuring with a light meter though just to be able to post some raw data. i think my point behind all of this was the argument against mirrors, to me, seemed unfounded and no reasonable explanation could be seen but I simply want everyone to know if mirrors are a possibility for their grow room, then are they actually the best.
 
riddleme

riddleme

Well-Known Member
I would like to add another tidbit of info as I work on TV's (have for 35 years)

for years rear projection (big screen) tv's had very nice glass mirrors in them, high quality (not cheap) used to reflect the light from the tubes to the screen.

In recent years all the rear projections I have run into use a mylar mirror, have not seen glass ones in awhile and these are evil mirrors, I say that because we took one out of a tv that we threw away and aimed it at the sun reflected a very concentrated, very bright beam of sunlight 3 blocks away thru an open garage door that lit it up , hey upon seeing that we pulled it fast figured cops would be called if we kept it up
 
thesmokering

thesmokering

Well-Known Member
saycheese said:
1)"Mirrors reflect coherent images, but this is completely seperate from if they reflect more or less light"
IMAGES ARE LIGHT!!!!!! This makes no sense.
2)Hot spots not only means temperature but a specific point of greater light intensity.
3)Wavelength impossible to measure?
I think not. Just an expensive device. They run about $250-$300. I can't afford one, can you?

Unfortunately you replied with complete opinion which is exactly what I didn't ask for. None of your information had any scientific or statistical data to back up plus you separated images from being light which is just pure ignorance. Hate to sound so hypercritical but I am finding info on these forums to be of utterly useless as no one is willing to spend the money to buy the equipment to find out real answers. I don't have the budget for a wavelength meter but I'm hoping one of you would seeing as how this would be in the best interest of a professional grower.
Click to expand...
When you quote me, dont try to rewrite what I said. You have it wrong, I said what I said, not what you said I said ok? :)

Now, imagine you have a mirror that reflects a picture of a baseball. The INTENSITY of the light is how bright the baseball looks in the mirror. The IMAGE is that you can recognize its a baseball. What is true is that the INTENSITY of light in the reflection is less than the INTENSITY of the light from the baseball picture directly.

The IMAGE is what mirrors are designed for. The INTENSITY is what reflective materials are designed for. Mirrors give you hot spots, just try it with 1000watt hps.

I said that measuring the wavelength is impossible to do at home, like without buying special equipment just using what you have at home, got it?
 
thesmokering

thesmokering

Well-Known Member
I said "Mirrors reflect coherent images, but this is completely seperate from if they reflect more or less light." What the f*** are talking about I said they dont reflect light ?
 
saycheese

saycheese

Member
thesmokering said:
Mirrors reflect coherent images, but this is completely seperate from if they reflect more or less light.
Click to expand...
funny cuz it sounds like your saying mirrors reflect images and that is separate from light... i have poor reading comprehension sure but maybe worse than i may have thought?
 
saycheese

saycheese

Member
actually i did mix up you with another fine chap on grasscity who said roughly the same thing but with different wording. i connected you both as it sounds like you said mirrors reflect images and that is separate from the amount of light. but still the fact is that images ARE light and whether or not mirrors cut down light is not the exact question posed. i absolutely understand mirrors or anything for that matter will affect the intensity or perhaps wavelength but the exact question I posed was are mirrors getting a bad rap for the wrong reasons and are they more reflective than mylar or white paint?
 
laserbrn

laserbrn

Well-Known Member
I still don't think lining your walls with mirrors is going to be better or equivalent for growing than white walls or mylar. It's the matter of reflecting the beams in an orderly fashion versus scattering the light in a completely random fashion. Put up a mirror and on one side of your grow room. Turn off all the lights and put a flashlight in the light hood area and direct it around at the mirror and look at the angles you are getting. Most aren't going to be touching the plants and definitely not near the top! We need the light dispersed evenly and randomly to best deliver that light across the surface area of fan leaves.

I should note that this is mostly applicable to light hood applications. There may be other situations where an open light without something creating the strange angles could utilize mirrors very well.

The answer to the original question is yes mirrors are reflective. There are varying levels of reflectivity in mirrors made of different materials and different methods. They are reflective, but some can be as high as 99.9% reflective. Obviously higher than Mylar.

We aren't trying to get away from the original question, we are trying to delve into the reason or possible reasons it is so commonly believed to be a poor method of utilizing reflectivity to maximize light efficiency for the purpose of Marijuana cultivation.
 
Mr. Good

Mr. Good

Active Member
What about smearing vaseline all over the surface of the mirror?

What about hiring bald guys to line the room walls with?

What about just drawing a picture of a mirror on the wall...using real mirror pieces?

What about Bob?

What about using Wrigleys chewing gum wrappers...?

The mirror is the Walrus, Coo Coo Ca-choo...

Ok thats enough
 
Brick Top

Brick Top

New Member
The deal with using mirrors as a reflective material that I never seem to see mentioned is how mirrors actually work. Light rays would pass through a layer of glass and then strike the reflective material and then pass back through the layer of glass again. Each pass through a layer of glass restricts some light rays and what happens is what is reflected back has lost about 10% of the usable light rays plants need.
 
saycheese

saycheese

Member
Brick Top said:
The deal with using mirrors as a reflective material that I never seem to see mentioned is how mirrors actually work. Light rays would pass through a layer of glass and then strike the reflective material and then pass back through the layer of glass again. Each pass through a layer of glass restricts some light rays and what happens is what is reflected back has lost about 10% of the usable light rays plants need.
Click to expand...
where is the study that provided this info for you?
 
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