I'm still very new to fusing and just had an experience that I hope someone can help me with so I don't repeat it again!  I was making a blank - full fuse using Bullseye 90 COE glass, according to the fusing schedule that came w/ my kiln.  My glass was a clear thin piece, 7x7, topped with a regular 3mm transparent piece of glass 7 1/8 x 7 1/8.  When I looked in my kiln just now, it fused perfectly - except for a nice 2" hole just off center!

Did I get a bubble?  What might have caused it?  This was my first time firing a blank that size - I've only fied two other blanks that were 4" square.  Also, this was my first time reapplying kiln wash because it was cracking before.  I had to lightly sand to try and get it all off before reapplying again.