@ jawbrodt
Maybe it should be clarified that foil MAY cause hotspots IF no tproperly layed. Meaning there should be as few as possible creases and wrinkles.
I think this is a fair statement...
Pure...
I used to think that same way, myself, until I thought about it a little futher. Let's just say that it was POSSIBLE,...... Being that some guys run 1000 watt HID's very close, with air-cooled reflectors, they are getting intensities well over the 10,000 range, , and that's direct light. For that light to be bounced off the side, then reflected back to the plants, inevitable, the distance from the plants, is going to be increased, which drastically reduces intensity. That, combined with foil's 70% reflectivity(laying flat), is going to knock down intensity to at least 50%, which is a high estimate, compared to what the main colas are receiving, directly. So, in order for you plants to be burned, if it is indeed even possible, the foil would have to be placed very close to the light, then positioned in a way that creates a strong 'lens effect', focusing light, and at least tripling it's intensity. I find it really hard to believe that could be done, even purposely, with a material with such poor reflectivity. IF it could be done, I believe that it could only be done with the most extreme of setups,(1000 watt HPS/MH running at 10" from the colas) and even then, I have my doubts. The light itself, would be more intense than an configuration of foil, could ever produce. No, I've never seen this proved, but, I've never seen a case of 'foil burn' either. But, I'm going to stick with my logic, til I see some real proof, that this is even possible. Knowing how the inverse square law works, combined with the losses from foils reflectivity, the numbers just don't add up, unless some geeks at MIT are experimenting with focusing designs, using foil, and have come up with some unusual configuration that gives it the boost required.
