I use cigarette lighter, and burn the lense from the inside. All the silicone that leached off the skirt onto the glass instantly turns black, make sure you get the corners good, and just wipe off the glass with a tissue. Dont wipe with fingers or clothing, and residue is hard to remove. Glass is tempered, so heat won't hurt it. Skirt is thick silicone, and it would take good amount of burning to damage it. Mask is good for about a month or two after this defog method. I have not had much success with toothpaste on new masks.