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Mylar vs. Aluminum Foil vs. Mirrors

Discussion in 'Indoor Growing' started by Cidly, Jul 7, 2007.


    Cidly Well-Known Member

    Ok guys i am trying to settle a friendly wager. there are three schools of thought here...

    1) Me: Mylar is best for reflective properties and coverage in the grow room.

    2) my buddies idea is to line the grow room with as many mirrors that can be reasonable be fit in the grow room with some coverage lost but due to the perfect reflectivity of the mirror there will still be adequate reflective properties to grow.

    3) another guy says to line the walls with aluminum foil (shiny side out) and that it would work fine.

    anyone care to settle this for us? Thanks ya'll.:joint:

    Gygax1974 Just some idiot

    You would be right. Mirrors absorb light and aluminum foil gets hot and gives off hot spots. I like mylar but I'm not good at hanging it so I went the Panda Plastic route with some Mylar here and there.

    Paola Well-Known Member

    What he said.

    trapper Well-Known Member

    some plant strains have big egos and so they like to watch themselves grow,for those a mirror is best.but the rest i would say mylar.

    mogie Well-Known Member

    LOL yeah mylar

    fdd2blk Well-Known Member


    trapper Well-Known Member

    fdd was i wrong,my brain cant compute scientific stuff like that.

    fdd2blk Well-Known Member

    mylar the was the most reflective.

    potroast Uses the Rollitup profile Staff Member

    Here's the chart of percentages of light reflected from Jorge's latest:

    Foylon 94-95
    Reflective Mylar 90-95
    Flat white paint 85-93
    Semi-gloss white 75-80
    Flat yellow 70-80
    Aluminum Foil 70-75
    Black < 10

    HTH :mrgreen:

    the.fatman.cometh Well-Known Member


    manlookingj Active Member

    I think what happens is the flouresent light is already diffused so it works great with mirrors and mylar, but the HID lights reflect the undifused HID and with the center of the burning bulb there to make some potential trouble. Now I've always thought mirrors was best, prefect reflection, but after going over these post, it's helped me to understand more on this subject. And I took all my mirrors down, I have white walls behind, so that works out, but I have four 4' flouresents and a 400w hps in the middle, and I started noticing spot on a few of my plants, and like I said, after review some post on the subject I promptly tore those mirrors down. Thanks for all the Info here.

    clubtp Member

    Hi, actually polished anodized aluminum is best. Mylar has a specular reflectance. You can get polished aluminum in diffuse or hammertone form which scatters the light around the room instead of a localized light spot. And example is when you shine a flashlight into a mirror, you will get a direct beam of light reflected. You don't want that. Some anodized aluminum which has been bright dipped has a diffuse reflectance of up to 95%! I found some at reflectit.webs.com. It is the same aluminum that is used for solar reflectors and light reflectors in the lighting industry for a reason.

    beigaleh Member

    Without addressing the question of which would be more convenient to use, in which case mylar is the winner, a mirror is obviously more reflective.
    Why is it more reflective? because it reflects waves in the visible spectrum 400~700nm most efficiently, almost at 100%. Mylar is good, but not as good as a mirror.

    We first need to understand that a reflected image is reflected light, and it's only reflected light and nothing but reflected light. (i'm talking about visible light, although a mirror reflects other parts of the spectrum as well).

    A way to demonstrate this is standing between two mirrors. You'll see the light bouncing back and fourth over 40 times for a good mirror right? You'll see yourself about 40 times. (just an arbitrary number).
    This means that the initial light has been able to bounce back and forth 40 times before vanishing, or becoming too dim for us to see!

    So if x is the % of light out of a 1 being 100% that's absorbed by the mirror, we get the equation (1-x) for every bounce off the mirror. for 40 bounces that's (1-x)^40. Let's say after 40 bounces we're left with 5% light (the arbitrary amount of light that is no longer visible).

    With these calculations a mirror reflects about 99% of lights. The number should be pretty close because the differences in input would be logarithmic.
    I don't know what's used to make mirrors, but I think I've heard somewhere it's very thin aluminum with a coating. don't quote me on that.

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