StonedBlownSkiller
Well-Known Member
ok thx fddi don't think so.
i need help on mirrors asap
- Thread starter Chronhead
- Start date
DawgMountain
Active Member
Bucket color... black absorbs heat more than white. If your black buckets are in direct sunlight, they may add heat to your soil.
Mirrors. The baseball analogy is way off. You don't speed up or slow down light. It's a constant for our general purposes. House mirrors are not perfectly flat. Sometimes you can see this in your reflection. Sometimes a mirror will stretch you wide, sometimes tall. It will "refocus" the light as mentioned above. That being said, when a mirror does this it is because it is no longer perfectly flat. It has taken on a concave or convex shape. That will create the magnifying effect and burn your plants. Better safe than sorry by using Mylar. Even foil can burn your plants cause it's not perfectly flat. Mylar doesn't reflect heat the same way so it's better.
Mirrors. The baseball analogy is way off. You don't speed up or slow down light. It's a constant for our general purposes. House mirrors are not perfectly flat. Sometimes you can see this in your reflection. Sometimes a mirror will stretch you wide, sometimes tall. It will "refocus" the light as mentioned above. That being said, when a mirror does this it is because it is no longer perfectly flat. It has taken on a concave or convex shape. That will create the magnifying effect and burn your plants. Better safe than sorry by using Mylar. Even foil can burn your plants cause it's not perfectly flat. Mylar doesn't reflect heat the same way so it's better.
Spanishfly
Well-Known Member
I used the term NONSENSE earlier, and I use it again here.
What do you mean by AMPLIFIED? (note spelling) Are you saying that the reflected light somehow gets some extra energy from nowhere, in total contradiction of the First Law of Thermodynamics? That is NONSENSE.
No, the reflected light from a back-silvered mirror is just a lttle less intense than the incident light - as I explained in my earlier post. Which I stand by as being totally correct.
Dielectric front-silvered mirrors, as used in telescopes, reflect rather more light, over 99%.
NB, I did teach Physics for many years.
Oh, and I would never use household mirrors myself, far too heavy, expensive and fragile.
Spanishfly
Well-Known Member
No, I have read this so many times, you haven´t experienced it yourself either DawgMountain cos it DOESN´T HAPPEN. No way will a randomly creased or bent piece of aluminium foil bring infra-red (heat) rays to a sharp focus, which would be necessary to cause a hot spot. And Mylar, which is coated in aluminium, obeys just the same laws of reflection as does foil.
golddog
Well-Known Member
That's just how it is.
there are vast differences in the way aluminums can reflect though, and tin-foil is a low grade reflector. For sure silver is a good reflective surface, but it's prohibitively expensive (for what you spend on silver you are better off upping the light output than trying to squeeze 1-4% more reflectivity). There is a reason that high quality reflectors use polished spectral aluminum, and mid grade ones use polished aluminum. I still think it's silly to push tin-foil. Flat white paint has been shown to up PAR ratings more than tin-foil as well, the last figure I heard said some brands of tin foil reflected less than 11% of the par spectrum.
I agree with you on the silly analogies
Also the glass used in mirrors will restrict UV unless it's specially treated, and the glass in home mirrors isn't going to be treated. Keep in mind this is the same if you have a sealed hood, or safety glass in your hood. Anyway, it's also unlikely that it's low iron (optical) glass, so it further is reducing the light output, I think it's a good idea to steer novice growers away from using household mirrors and on to more easily used, and appropriate, materials.
