dose the mylar need to be compleatly flat?

Thank you to anyone hew replys! i recentaly built a grow cab 3 x 2 1/2 x 8ft I have supports i had to go around so the mylar is mostly flat but dose have some slight ripples, around the joints will this cause burn/ hot spot. Do those even excist thank you again for reading and help

This is why i hate mylar i had a room almost perfectly smooth... 4 hours later it looked like crap. Next time i will go with Panda Plastic. Good luck, man... it's an impossible mission. But, yah, the flatter the better.
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When working with mylar i prefer to use velcro. Just cut your piece, apply one half to your stud or wall staple it, put the other half on stick your mylar to it and BAM, do that a few more times and you have mylar that can be readjusted or more easily washed

rotcodnatas said:

When working with mylar i prefer to use velcro. Just cut your piece, apply one half to your stud or wall staple it, put the other half on stick your mylar to it and BAM, do that a few more times and you have mylar that can be readjusted or more easily washed

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good tip!!!

op the Q and A is should i use mylar or not in the room? A yes you should never mind if its perfectly flat or not. i use dimond mylar and that is run through a crimping press http://www.greenshorticulture.co.uk/Growroom-Products-20/-Sheeting-331/Diamond-Grow-Reflective-Sheeting-855.asp

9inch bigbud said:

good tip!!!

op the Q and A is should i use mylar or not in the room? A yes you should never mind if its perfectly flat or not. i use dimond mylar and that is run through a crimping press http://www.greenshorticulture.co.uk/Growroom-Products-20/-Sheeting-331/Diamond-Grow-Reflective-Sheeting-855.asp

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I have been through this same sort of discourse with numerous people on numerous herb growing sites many times.

When using Mylar, as in flat sheet Mylar it does make a difference if it is flat or not. There is a vast ocean of difference between wrinkles and crinkles and sags and lumps and folds and creases and seams and taped tears from a designed systematic patterned surface.

Many times people have said, look at dimpled reflective hoods, they are not smooth and they have a very high degree of reflectivity. Well they are an example of a designed systematic patterned surface just like the material you use.

So it is inaccurate to compare a designed systematic patterned surface to flat sheet Mylar or any other form of reflective material with wrinkles and crinkles and sags and lumps and folds and creases and seams and taped tears and say it is not a problem and that it is just fine.

It has been more than just proven that any reflective material with a random uneven surface can and will produce hot spots. It is way less of a problem for someone using CFL’s than it is for someone using HID lighting but in both cases it will cause an unequal diffusion of light rays and that will mean some area covered by the light rays will receive more light rays than others and that can make a difference in plant growth and productivity regardless of what type of lighting someone uses.

You always want to attempt to provide as optimal of conditions as is possible for your plants and an even reflection/diffusion of light rays is an important part of creating optimal conditions.

It makes a huge difference, actually. If your light even matters by the time it gets back to the plants, that is.

The flatter, the better. Dimpled hoods form concave crevices to create scattering. This is not the same as diffusion.

Diffusion is like smooth fluffy clouds. Scattering is like a fractal, it has well-defined ridges, peaks, and valleys like well-defined clouds.

I offer examples! Attachment 1 is diffusion, an even field decaying over an area. Scattering still focuses(concentrates) the light , and is seen in example two.

Well said.
"Many times people have said, look at dimpled reflective hoods, they are not smooth and they have a very high degree of reflectivity." Wow i cant believe some people would think that, but i guess there are some silly fucks out there

Let me be more concise.

Reflectors are designed to concentrate light.

Lets look at some examples:

Three attachments are provided.

The first is 75% diffuse, and a 25% increase in lux.

The second is 50% diffuse, and 50% increase in lux.

The 3rd is 0% diffuse, and 100% increase in lux(ideal reflector).

The 3rd image is what a good reflector ought to do.

The final image is one example of what wavey mylar might do.

how about just use a mirror is that possible?

No, a mirror will just create a giant hotspot.

Otacon said:

No, a mirror will just create a giant hotspot.

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Wrong.

Where do people get these crazy ideas?

Don't know, sounds logical to me So then, can you use a mirror?

Reflectors(the good ones) are mirrors without the glass. The glass makes a minor difference.

Yes, you can use mirrors.

Otacon said:

Don't know, sounds logical to me So then, can you use a mirror?

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Are mirrors good for reflecting light?

Mirrors waste energy by absorbing only a small fraction of the light that falls on them.
When light, which, like radio waves, is a form of electromagnetic radiation, strikes a metallic mirror the electrons in the metal move just as they do when a radio signal strikes an antenna. Pushing electrons around takes energy, which dims the reflected image.

Metallic mirrors reflect infrared light (heat) and if your mirror has imperfections this will cause hot spots, which can burn plants. Please note hot spots also apply to Mylar and Foil and IMO is not applicable to growers using small amounts of fluorescent lighting.

By using a mirror to reflect your light on a wall, you can test for imperfections, if you see an uneven image, with focused beams (normally located at the edge of the reflected pattern) these are known as hot spots and depending on the wattage of your bulb, may burn your foliage.
Metallic mirrors should not be used as a reflector for your grow room as minimizing light loss is important

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Lets examine some lines of thought.

Trees cause forest fires. Damn those trees! If they weren't there there would be no forest fires ever! Lets not blame the source, lets blame that which propagates the flame.

Isn't that, pretty much, the same as saying foil(trees) causes hot spots(fire)?

Mirrors waste energy by absorbing only a small fraction of the light that falls on them.

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Seriously? That doesn't even make sense. How is energy being wasted if absorbing only a small fraction of the light that falls on them is true? Do you read and think about what you quote? Do you think the guy who wrote that did?

these are known as hot spots and depending on the wattage of your bulb, may burn your foliage

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Almost a fully qualified statement!

Factoring in... bulb type, proximity, angles, light distances traveled ... may burn your foliage.

Well, if you take a mirror, like a hand-held mirror. You can also do it with aluminum foil(shiny side). You can reflect your room's main light(from the ceiling) off the mirror and on to the walls and easily see it(the shape of the mirror, as a light patch). You can not do this with white paint. It certainly will not be a well-defined shape.

Energy is neither created nor destroyed. You can either choose to rapidly accelerate the decay process with diffused surfaces. Or you can choose a highly specular surface, like a mirror or polished metal and not aid the decay process. A diffused light source(omnidirectional) is already creating a diffuse reflection off a mirror surface.

They make these really big pyramid-shaped or cone reflectors, aluminum of course.







http://images.google.com/images?ndsp=20&hl=en&safe=off&client=opera&rls=en&um=1&q=grow+plant+reflector&start=0&sa=N

Just lots and lots of metallic reflectors. Most are smooth & flat.

That middle reflector really reminds me of crinkled aluminum foil.

TeaTreeOil said:

Lets examine some lines of thought.

Trees cause forest fires. Damn those trees! If they weren't there there would be no forest fires ever! Lets not blame the source, lets blame that which propagates the flame.

Isn't that, pretty much, the same as saying foil(trees) causes hot spots(fire)?



Seriously? That doesn't even make sense. How is energy being wasted if absorbing only a small fraction of the light that falls on them is true? Do you read and think about what you quote? Do you think the guy who wrote that did?


Almost a fully qualified statement!

Factoring in... bulb type, proximity, angles, light distances traveled ... may burn your foliage.

Well, if you take a mirror, like a hand-held mirror. You can also do it with aluminum foil(shiny side). You can reflect your room's main light(from the ceiling) off the mirror and on to the walls and easily see it(the shape of the mirror, as a light patch). You can not do this with white paint. It certainly will not be a well-defined shape.

Energy is neither created nor destroyed. You can either choose to rapidly accelerate the decay process with diffused surfaces. Or you can choose a highly specular surface, like a mirror or polished metal and not aid the decay process. A diffused light source(omnidirectional) is already creating a diffuse reflection off a mirror surface.

They make these really big pyramid-shaped or cone reflectors, aluminum of course.

http://images.google.com/images?ndsp=20&hl=en&safe=off&client=opera&rls=en&um=1&q=grow+plant+reflector&start=0&sa=N

Just lots and lots of metallic reflectors. Most are smooth & flat.

That middle reflector really reminds me of crinkled aluminum foil.

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so what are you saying mirrors do not make hot spots in a grow room? or do you recomend using mirrors to line your walls with?


Hot Spot
You can focus the invisible light from an electric heater.
Infrared radiation from an electric heater is just another "color" of light. Though you can't see this light with your eyes, you can focus it with a mirror or a lens and feel the warmth it produces on the back of your hand. From this Snack, you can also learn how parabolic shapes concentrate energy.

• A large concave mirror, 16 inches (40 cm) in diameter (available for about $40 from Sargent-Welch, P.O. Box 1026, Skokie, IL 60076-8026).
• A small electric heater.
• Adult help.

(15 minutes or less)
Place the heater many focal lengths away from the mirror. (The focal length for the recommended mirror is about 1 foot [30 cm], so place the heater about 10 feet [3 m] away.)


(15 minutes or more)
Move your hand around in front of the mirror until you can feel the hot spot. This spot will be close to the mirror's focal point.
Look into the mirror and find the visible image of the heater: This image of the heater is also near the focal point.
Look into the mirror and move around, observing your reflection. Move forward and backward in front of the mirror, and see how your image and the images of the objects around you change.

Move the heater off the axis of the mirror or closer to the mirror. Search around, using the back of one hand as an infraredradiation detector. Find where the infrared radiation from the heater is concentrated. This will be the position of the infrared image of the heater. Locate the visible-light image of the heater with your eyes. Notice that the infrared energy from the heater comes back together at the visible-light image position. Notice also that the image point is not the focal point.
Place your face close to the mirror and talk into the mirror. Keep talking as you move away from the mirror. At one point, your voice will sound much louder. At this point, the sound waves radiating from your mouth bounce off the mirror and are concentrated at your ears. When this happens, the mirror is making a sound image of your voice at the position of your ears.


Every parabolic mirror has a focal point, a place where all parallel light waves, sound waves, or any other form of radiation directed at the mirror along its axis will be concentrated. Infrared radiation is simply light with a wavelength too long for your eyes to see. But your skin can feel infrared radiation as heat. The skin of your cheek and on the back of each of your hands is particularly sensitive to warming by infrared radiation. The parabolic mirror concentrates the infrared radiation coming from a distant heater at its focal point. That's why you feel a hot spot when you put your hand at the mirror's focal point.
When the heater is moved closer to the mirror, the point where its radiation is concentrated, the infrared image of the heater, moves away from the focal point.


Satellite dishes for TV reception operate on this same principle, except that they focus radio waves instead of light waves. The surface of such a reflector doesn't need to be polished like the parabolic mirror because radio waves are much longer than light waves. To a radio wave, the surface of the dish looks very smooth: Its small irregularities don't affect the long radio waves. The very short light waves, on the other hand, are bounced off in all directions by the radio dish's surface roughness, so light waves are not focused. For reasons of economy and weight, the large dishes used to focus the even longer radio waves from astronomical objects (stars, quasars, etc.) sometimes are constructed out of a rather large mesh screen, which appears smooth to the very long waves.
A family of snakes called pit vipers, which includes rattlesnakes, has two or more sensory "pits," which they use like pinhole cameras to image infrared light. The snake can then locate a warm-blooded creature, such as a mouse, by imaging the infrared heat radiated by the mouse. With two pits, the snake even has some depth perception in the infrared.

Conversely, having the light centered on the focal point will evenly distribute the light off the of the parabola. This is the basis behind parabolic reflectors. I like mirrors on my walls because I can easily see the other side of plants. They're flat, though.

TeaTreeOil said:

Conversely, having the light centered on the focal point will evenly distribute the light off the of the parabola. This is the basis behind parabolic reflectors. I like mirrors on my walls because I can easily see the other side of plants. They're flat, though.

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mirrors are not that reflective they are less reflective than white paint. mirrors refect 80% of the light back at the plants flat white paint reflects 90%. why dont you use white pant?

relativeood said:

If you have to ask questions about mirrors, paint, or aluminum foil then you simply ARE NOT USING ENOUGH LIGHT.

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LOL no its making the most of the light you already have! if you are paying for that light you want to use as much of it as you can. if you did not use mylar or somthing to reflect that light back then you are lossing out on possibly 10-20% extra yeild may be more?