This was the briefest phenomenon and disappeared in a few moments, but the image is burned on my mind as well as my SD disk.So, I'm getting on with my window in spite of being rather daunted by the BBC's MasterCrafts Stained Glass Programme and Sophie Hussain's wonderful work: http://www.facebook.com/album.php?aid=151009&id=339476232559.
I've become more adept at the more complex shapes and am wasting less of the more expensive glass.
I've also learned to mark each piece, especially where they are more or less the same size and configuration, having discovered that turning some pieces (particularly the water glass) means the subtle pattern goes in the wrong direction.
I've also resorted to using the glass saw (to the right of the picture below) for some shapes. I really should get more practice in cutting curves and grozing them accurately, especially concave curves.