Not Stella, but I do about the same thing. I take a skewer when a thin shell has formed on top and basically bash in the whole top of the candle, stopping 1/4" or so before I reach the outer edge; looks like a rabid woodpecker has been at it:cheesy2: Don't wait too long to do this, or it won't work. Since you aren't going all the way to the edge, it doesn't affect the crystallization pattern that you see; only the interior and top are affected. I then hit it lightly with a heat gun to make sure the wax runs down; not too much, though, or you'll melt the outer edge and you don't want that. Sometimes I repeat this process a second time just to make sure. At the end, top off carefully (if needed), pouring only up to the original level to avoid a band of wax with a different pattern from showing on the outside of the jar. Sometimes no top off is required, just depends upon how much wax had to run down to fill in holes; in that case, just lightly smooth the top with a heat gun. This is time consuming, but in the end you don't have any caverns to worry about.