Marlene - I use a HotHead, too. I couldn't get mine to get a reaction from encasing either. I do use it on Ivory but by itself. I make an ivory bead, roll on either a 1/4 or 1/2 sheet of the blue foil, which I lay down with the lighter side facing up. When I put it in the flame, I gingerly burn off the foil but not completely
, using the edges of the flame. That's where you get some neat blue and rust streaks from it. And don't etch a bead made with it - the colors dull.
Here's some examples of what I have done with it on my HotHead: