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

correct me if im wrong but....I have heard that its a myth about burning the plant with ripples in reflectors. it just diffuses the light in a bad way

nah its ment to be tight but i got it best i could
but the pros say tighter the better

The flatter you can make your reflective material the better it will work. Any unevenness and ripples and crinkles will cause a reduction in the percentage of light rays that are equally reflected, diffused, and that will reduce its efficiency and it can, if using HID lighting, cause hot spots.

That is one reason why flat white paint makes such a good option for a reflective material It not only has a high reflective capability but it is extremely easy to apply and have as flat of a surface as is possible. Someone can use a reflective material that will reflect a higher percentage of light rays and by applying it poorly end up with a lower percentage of reflection than flat white paint will give you.

Also while Mylar is very good as a reflective material it can easily be damaged, especially if someone tries to save a few dollars and cuts a few corners and purchases the thinner Mylar. Keeping it clean so it retains its high reflectivity can be a problem in that just washing it can damage it especially if it is not applied as flat as is possible and just washing it can change a well applied sheet of Mylar into a poorly applied sheet of Mylar.

A better option that Mylar is Foylon.It is a more durable version of Mylar that is made of spun polyester fabric and reinforced with foil laminate. Foylon is resistant to most solutions, won't tear or fade, and can be wiped or washed clean. It costs more but will outlast Mylar by a long-shot and in the end be a better value in that you will not have to replace it nearly ass soon.

You already purchased it and you already applied it so now all you can do is live with the results.

If you have very little minor wrinkling and are using CFL’s I would say you have little reason to be all that concerned since CFL’s do not put out a lot of light and they do not put out a lot of heat, both of which will be reflected, but if you are using HID lighting you may likely end up with hot spots.

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The flatter you can make your reflective material the better it will work. Any unevenness and ripples and crinkles will cause a reduction in the percentage of light rays that are equally reflected, diffused, and that will reduce its efficiency and it can, if using HID lighting, cause hot spots.

That is one reason why flat white paint makes such a good option for a reflective material It not only has a high reflective capability but it is extremely easy to apply and have as flat of a surface as is possible. Someone can use a reflective material that will reflect a higher percentage of light rays and by applying it poorly end up with a lower percentage of reflection than flat white paint will give you.

Also while Mylar is very good as a reflective material it can easily be damaged, especially if someone tries to save a few dollars and cuts a few corners and purchases the thinner Mylar. Keeping it clean so it retains its high reflectivity can be a problem in that just washing it can damage it especially if it is not applied as flat as is possible and just washing it can change a well applied sheet of Mylar into a poorly applied sheet of Mylar.

A better option that Mylar is Foylon.It is a more durable version of Mylar that is made of spun polyester fabric and reinforced with foil laminate. Foylon is resistant to most solutions, won't tear or fade, and can be wiped or washed clean. It costs more but will outlast Mylar by a long-shot and in the end be a better value in that you will not have to replace it nearly ass soon.

You already purchased it and you already applied it so now all you can do is live with the results.

If you have very little minor wrinkling and are using CFL’s I would say you have little reason to be all that concerned since CFL’s do not put out a lot of light and they do not put out a lot of heat, both of which will be reflected, but if you are using HID lighting you may likely end up with hot spots.


now that is a answer
a good one
rep for you
thanks for going to all the effort

The flatter the surface, the better. That is correct. But diffusion is indirect reflection over an area.

Hot spots would be caused by reflection that is superior and/or highly concentrated(both would help). Crinkles will not cause hot spots. They increase diffusion.

When forming large lens (like waves, possibly) it's possible to concentrate enough of the light source creating hot spots with specular reflectivity.

White paint varies widely from less than 50% to 90% reflectivity in the visible spectrum.

The surface is not flat. If you think so, I suppose it's deceptively flat. The surface, if zoomed in, would look like craters and hills, with little blobs of crap everywhere.

Comparing apples with rotten oranges again!

The best white surfaces are usually enamels, from the research I've done. Enamels typically have a much flatter & smooth surface than any paint brush will get you.

If you can't get that a powder coat is the next best.

Regular paint with a brush or roller... far less.

The thinner the material the more chance light will transmit through it.

Mylar has a microscopic layer of aluminum on it. Depending on the thickness it could be transmitting lots of light(up to 80% at the thinest levels). The thicker the better! Not only will you ensure near perfect reflectivity but you get a more durable product.

Or 3M makes this stuff called ESR(Google:"3M ESR"). It's nearly 100% reflective(I've seen it used as a benchmark of real world 'perfect' reflectivity, at least for the visible spectrum). This is an exceptionally fine mirror finish.

Well, that's mostly true. The lower intensity light source the higher reflective quality desired.

For hot spots to occur the intensity(I) would have to be sufficient enough to create a concentrated effect.

I = lumens / distance(feet) ^ 2

Hanging additional aluminum(regardless of form) from the hood of HID would probably be bad, as heat wouldn't escape as easily. You could basically create an oven! Heat travels up. So you're really creating a nice environment for heat to get trapped.

However, if you place it on the walls, where the distance to it and back to the plants is more than a couple feet.... There's an impossibility of enough intensity remaining to cause any harm. Even for a 1000W(140,000 lumens) HPS at 2 feet it'll decay to 35000 lumens(25%). And this is assuming a completely directional output towards the reflector surface(highly unlikely).

If you're worried about over intensity I'd suggest white paint.

For example, take a laser, and shine it near the ceiling, but on the wall of a white room. See the even smooth glow it projects on the ceiling(you'd need a powerful laser to even see this).

Now try this with aluminum foil, for instance. See the far more intense reflective point? You don't really need a powerful laser to see this!

It's as simple as that.

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mine is not perfectly flat and when the fan blows it moves it anyway.. if you think about it. flowing mylar would be better than steady mylar because it bounces the light all over the place. no? it seems to work for me.
my plants dont seem to be suffering

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