Quote Originally Posted by John View Post
That's an interesting question. I'm actually trying to get away from the expanding foam + silicone method. It takes a long time for the foam to cure and there's controversy over whether or not GE Silicone II is safe or not. The anecdotal evidence and my own experience is that yes it is safe. However, my next background is going to be clay (yep, the kitty litter method). I've already got pure sodium bentonite kitty litter for it. It's cheap and very quick. You just can't let it dry out completely or it will crack.
I'm actually considering foam for the upper half and clay for the lower half where it will stay moist. I don't have a misting system and I just know that I'll forget and let it dry out up near the lights.