Mylar...Hotspots

Mylar bad, white paint good?

I think the hot spot thing is a myth. I have used aluminum foil and mylar and never had a hot spot. To produce a hot spot would require a parabolic shape and a wrinkle isn't going to give you that not to mention the plant would have to be at the optimum focal point from the parabolic wrinkle to burn just doesn't sound true and I have never experienced this so I call BS

Mylar is probably better than white just because it does reflect more light. I think that a hot spot might occur if your light is way too close to the mylar...but if it was that close to the wall you might burn your house down anyway. So my vote is mylar if you hang it decently enough.