Mirror Room...

Marthacrookshanks said:

Wow, I can't believe grown adults are having this discussion. The true mirrors that reflect the highest volume of light waves visible and non visible have no glass others are coated in quarts, same for lenses that look into space. Any mirror with glass in is only a cheap alternative good for looking at yourself, and people in cas behind you in.
There is a lot of physics involved in explaining why, and unless you have a grasp of it your not going to understand that glass mirrors are not as reflective as you Kerovan are making out. And Certainly not good for using as a growing reflector, which is what the original context the question was asked in.
But the very best reason not to use mirrors in a grow room that no one seems to be saying here is cost. Mirrors v.s Mylar Or Black white sheet is gonna a big difference, and would not do as good a job as mylar or white black sheeting. for the fact that all reflections from a mirror are specular and for it to have an even coverage the light or the plants would have to be constantly moving. This is why its best to use the products that are out there for applying to surfaces in grow rooms.

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Said better than I just tried to. Even dismissing physical laws, the point I was trying to make is that glass covered mirrors are second-rate at reflectivity *compared to using a reflective surface sans glass*, they are pointlessly more expensive, prone to breaking (safety and all that), and suffer greatly at reflecting light when dirty.

If anyone wants to get into a discussion about the specular reflection of any certain material - I'm game. But you first have to define what reflective material you are talking about at the least (and it should probably be in another topic).

HOly Crap.. SOmeone get a farkin light meter & check it so we can move the fark on.

Thank you

I have 2 150 watt security lights I use in my grow room. A lot less heat when the lens cover is on (Clear glass) but I wonder if Im losing lumina?

God, now I need a light tester..

Brick Top said:

You have been correct that it is not the glass itself that absorbs light rays/energy. It is instead the metallic backing behind/under the glass that absorbs a small percentage of light rays.

Light absorption does take place but most people wrongly blame it on the glass itself rather than the metallic backing beneath/behind the glass.

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Brick Top, please define what reflective material in a mirror you are talking about. And then please tell how using that same material without a glass covering, has more or less reflectivity. That is what is being discussed.

I, and most everyone, already know that no material is, nor can be, 100% reflective and that some light is lost in the course of being reflected. That is a given.

Marthacrookshanks said:

The true mirrors that reflect the highest volume of light waves visible and non visible have no glass others are coated in quarts, same for lenses that look into space. Any mirror with glass in is only a cheap alternative good for looking at yourself, and people in cas behind you in.

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In no message claiming mirrors are a good choice for a reflective material for growing mentioned quartz mirrors or dielectric mirrors. That leaves common household types of mirrors as almost certainly being what is being discussed and most of those are metallic backed mirrors.

If you want to bring dielectric mirrors into the discussion then it would be an entirely new ball game ... but they are uber-high tech and used mainly with high powered lasers and fiber optic reflection and not many housewares stores stock those types of mirrors and people do not have those sorts of mirrors hanging on their walls or on medicine cabinets in their homes and I doubt quartz mirrors for looking deep into space are found in homes so people can more closely inspect their zits and ingrown hairs or how closely they shaved that day or how white their teeth look on any given day.

The only mirrors actually being discussed here are those the average person has access to and have in their homes, and not ones that are used at Fermilab or Lawrence Livermore National Laboratory or NASA.

carl.burnette:

Measuring PAR specifically I got a 7% loss through perfectly clean 3/16" glass - one way (directly under).

Oh.. 7% is a fair bit. Perhaps I should keep the lenses off the lights. That will increase the heat directed on the plants.

Although.. with the lenses on I can get the plants closer to the lights (by about 6")

7% decrease in light BUT I get the plants 50% closer.. is that a decent trade? Hmmmm..

I feel an experiment about to start. I have 2 lights in the same cabinet with plants that started the same day & the same strain. I'll keep the one lens open & the other clsoed & we'll see what happens

Yeah you have it right, you lose some radiation in the glass but if it reduces the heat enough that you can get the lights 50% closer - it will be an overall gain. Even getting around 1" closer more than makes up for a 7% loss to a glass covering.

You do lose almost all UV radiation with the glass. Which I only mention because some people go out of their way to add UV radiation into their grows.

Hmm.. Now Im thinking I need more UV.

Oh God.. This is like competing with the Joneses! I want UV light now!... oh.. you got 250 watt HPS well i NEED a 400 now!!!

I guess the bottom line is if your happy with what your producing then just have fun with it.

Haha - yup. The UV debate is another hot topic with growing cannabis that gets debated a lot like this one.

Brick Top definitely got the point across. Use mirrors if you want, but what's the point if flat white paint works better?

Personally I'm a fan of mylar, but everyone has their individual preferences and environment.

As for the glass...well the answer is pretty easy to get at. When I seal my lights with glass to air cool them, the light meter reads lower. Remove the glass and the intensity increases.

TL;DR: Don't use mirrors.

Bricktop knows the deal.

On a related note though, how can I see a wicked infinity image in the mirror if the light loss is even close to the claims made in this thread? I have mirrors on both sides of my bathroom and can see many many generations into an infinity shot. I don't know how many exactly, but im gonna find out as soon as I go home. But a 7% loss in visible light would manifest itself very quickly and make an image fade into nothing.

guy incognito said:

Bricktop knows the deal.

On a related note though, how can I see a wicked infinity image in the mirror if the light loss is even close to the claims made in this thread? I have mirrors on both sides of my bathroom and can see many many generations into an infinity shot. I don't know how many exactly, but im gonna find out as soon as I go home. But a 7% loss in visible light would manifest itself very quickly and make an image fade into nothing.

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You are actually only seeing/perceiving a single reflection not a continuous, infinite, series of reflections continuing on to infinite. Or another way to look at it is, you can't shine a light into a box made of mirrors, close the box (if you could at the speed of light anyway), and carry the light around in the box with it just reflecting from surface to surface for infinite. The light would instead very quickly reflect a very limited number of times, be absorbed, and the energy radiated off as heat.

TaoWolf said:

You are actually only seeing/perceiving a single reflection not a continuous, infinite, series of reflections continuing on to infinite. Or another way to look at it is, you can't shine a light into a box made of mirrors, close the box (if you could at the speed of light anyway), and carry the light around in the box with it just reflecting from surface to surface for infinite. The light would instead very quickly reflect a very limited number of times, be absorbed, and the energy radiated off as heat.

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Yes but if I see 5 of me in the mirror im facing that light has gone back and forth. I see my original reflection, and then I also see light that has gone from light->me->mirror 1->mirror 2->mirror 1->my eye as a second image of me. Then I see light that has gone from light->me->mirror 1->mirror 2->mirror 1->mirror 2->mirror 1->my eye as my third image, and so on. Each generation I see is simply a reflection of another reflection. My point was it has to bounce off both mirrors for each reflection, so the 5th "me" in an infinity reflection has bounced off 11 mirrored surfaces before it hits my eye.

Although the images do get smaller as they appear further and further, so maybe the light is being absorbed but enough is still there to make a smaller image.

Or another way to look at it: at what size percentage is each successive generation of reflection smaller and why do you think they get smaller? Is there an infinite amount of light in play or a decreasing amount of light making up each perceived reflection?

If you could theoretically "see" each reflection as it occurred in real-time, it would indeed become dimmer. Instead we only see one master reflection from any one surface at one given point in time before it is absorbed by the tissue in our eyes and becomes an image in our brains. The amount of light bouncing back and forth does keep decreasing - we just don't perceive it that way.

THIS THREAD WONT DIE!!!


BTW, I use bright white paint. Cleanable, cheap, repairable, washable and it looks nice. Mabye in the future when I need the extra 5-10% light reflection will I look into something.

Dam Bricktop you know your shit, are you a phytsics theacher? Im impressed.

But my drunken mind has doubts.

Your right about how I use scraps an trash to make my box, it only cost 90$ (IM SOOO DAM CHEEP) LOL. I do the best i can with very little money.
I live in bumfuckegypt an the qickest free choices were white an mirrors.
I tried white, an mirror makes it light up alot more, at least to my human eye?

"Metallic mirrors work pretty well, but they have limitations. The most important is that they waste energy, absorbing a small fraction of the light that falls on them."
I wonder how much light white paint absorbs? Id bet it absorbs more than a mirror cause a mirror visibily reflects ALOT more light.

How far does the diffused light off a white wall travel vs a specular reflection of a mirror?
Ill bet the intensity an travel are much better with mirror?
We grow with Hids cause the light is intense an travels?
We dont put difusers under our HID lights cause diffused light is weekend?

IDK? I have no degree in science its just my gut questining the conventional wisdom. Its all based on my crazy ass opinions an observatons, lol.


SCARHOLE

Well i've just checked back in. What have i started!! I hope you guys are all still friends!

We can safely say this subject was thoroughly debated and a conclusion found,

Thank you all for your opinions and facts.

Brick Top for your extensive knowledge, research and time

plus all others, too many to name.

Carl.B keep us updated if you follow your experiment. through.

Not sure why i asked this question, answers i suppose.

I've got some more cRaZy questions to come and a grow journal in the very near future, hope you can all tune in.


I'm looking forward to getting a bit more involved an getting to know you all.

Thanks all

Peace

I wonder how much light white paint absorbs? Id bet it absorbs more than a mirror cause a mirror visibily reflects ALOT more light.

--Not necessarily, specular or diffuse doesn't impact the total amount of light reflected, those terms just describe the behavior of the photons to reflect in a uniform direction (by angle) or a diffused pattern (in multiple directions). For example, the surface of water is specular but it's reflectivity isn't necessarily any different than the total reflectivity of snow, which is diffuse, but both can literally reflect enough light to burn your retinas. With water, you have to be at the right angle of the sun to catch enough of the reflected light to hurt your eyes, otherwise the water will be reflecting very little light into your eyes. But with snow, the reflected light is diffused enough that you can become snow blinded regardless of the angle of the sun. Both are made of the same substance and total reflectivity is going to be around the same... the difference is just in the angles that light reflects off of it.

...Which is why it's important to actually define the reflective material in question and not just say a 'mirror' is more or less reflective than anything else just based upon the fact that mirrors have specular surfaces. Specular vs diffuse is relative to the object being reflected upon. A diffuse surface will more than likely bathe an object in more reflected light than a specular surface which will concentrate that light into a more defined area (at an angle to the light source).

How far does the diffused light off a white wall travel vs a specular reflection of a mirror?

--Again, it depends on the material of both the wall and the mirror (and on-topic, if the mirror is losing some light to glass) as well as the intensity or volume of photons coming from the light source and any material, objects, atmosphere - or anything the light has to travel through as far as distance is concerned.

Ill bet the intensity an travel are much better with mirror?

-- It's relative to the angle you are at in relation to the light source. Higher intensity within a very specific angle, almost none outside of the correct angle. Think of looking towards someone with a signaling mirror off in the distance. The mirror will be highly visible if you get the angle right but not visible from a distance if the angle is not right. Now if that person were wearing white clothing, that would stand out from a distance regardless of the angle because clothing has a very diffuse surface.

We grow with Hids cause the light is intense an travels?

-- All light travels at the same speed and distance barring interference. In comparison to a CFL of the same wattage, HIDs just produce a larger *volume* of photons. A CFL produces a lower volume of photons so the loss of photons to being absorbed or being reflected away from a usable direction is more noticeable.

We dont put difusers under our HID lights cause diffused light is weekend?

-- Not sure what exactly you mean by a diffuser but as far as diffused light being weaker than specular, it's the same as as in your first question.