I use system 96 glass in my skutt kiln. I have been having so much trouble with bubbles. I have followed other blogs about bubbles on how to fix the problem. I have flipped the shelf over. I have increased the soak time to 30 min and 40 min. I have used shelf paper thick and thin. HELP! My bubbles are about a 1/4 inch. Not horrific but, definitely not attractive in my projects.