Sorry about the photo - but hopefully you can see at the front and the left side of the black piece the top layer has pulled back.
So I tried this with 3mm black base, pile of silver flakes and 3mm tekta cap (also tried 3mm top and bottom and same result but impossible to take a photo). Both layers of glass were the same size.
This was fired on my normal full fuse schedule.
I was experimenting to see if the silver held up to the heat, which it does very well, but I don't know what happened with the top layer sort of shrinking, it's worse than a dichroic exposed edge, the glass seems to have gravitated to the centre....ant thoughts?
(http://farm9.staticflickr.com/8473/8145870670_d3b5f9283f.jpg) (http://www.flickr.com/photos/paladinglass/8145870670/)
Untitled (http://www.flickr.com/photos/paladinglass/8145870670/) by Jeannette Copeland (http://www.flickr.com/people/paladinglass/), on Flickr
ive had this problem before, i dont konw exactly why it happens but i guessed with mine it was something to do with the inclusions creating a barrier beween the two layers of glass and not allowing them to fuse around the edges, so the top layer then pulls back trying to apply its 6mm rule.
i was working with mica trapping it in the middle and the really interesting thing is that when i later broke my pieces to use the glass again, where the mica had been the black base and clear top had not fused at all.
All i can advise is try and make sure there is a clear boarder around the edges so it can fuse nicely, as this worked on my finished pieces.
sorry if this is a little wittery :)
I believe you need to make the top layer slightly bigger than the base layer, from what I can remember...
I think that qwirkglass's analysis is probably correct - you have a lot of inclusions. Also, was air trapped?
Quote from: Margram on November 01, 2012, 09:57:46 PM
I believe you need to make the top layer slightly bigger than the base layer, from what I can remember...
I agree with this. When I did a course at Warm Glass a year or so ago we were advised to do this, and my dichro pendants have been much better since. The slightly larger (2 - 3 mm) top layer slumps down and covers the edge of the bottom layer. Of course, if it's much larger, or you let it get too hot, you'll get a wider clear rim than you wanted.
Nick