Tiny "champagne bubbles" are a common and acceptable occurrence in fused glass. They add charm to hand crafted items. But bigger bubbles can ruin days of work
Keeping that perfectly smooth and glossy piece of glass smooth can be a challenge. The first step is cleanliness. A tiny spec of dust or one fingerprint can spell disaster. A tip from Bullseye Glass Co., which offers many very good tutorials, helped me here. They recommend Spartan Glass Cleaner and lint free cloths. Spartan comes in a condensed form and, when properly diluted, is more economical than its purchase price may seem at first. After cleaning, be careful to touch only the edges of the glass.
My next helpful hint came from Grand Central Glass, a wonderful glass shop in St Petersburg, Florida. They helped me perfect the "bubble squeeze". This is a technique is designed to slow down the fusing to allow bubbles time to escape. I let the glass "soak" at about 1240º for at least 1/2 hour. I also slowly ramp from 1100º to 1300º - about 60º per hour.
The arrangement of the glass can help too. I place the smooth side of the glass up. Several small pieces in the bottom layer, rather than one big piece, are less like to cause bubbles. (I suspect that's why we see so many striped pieces of fused glass.) It's best to avoid trim pieces of glass near the edges of the piece.
When all else fails, smile and accept your work as a unique hand crafted work of art - and tell 'em you meant to have those bubbles!