A bubble squeeze is a segment that is introduced into a firing schedule to assist in the removal of air bubbles trapped between glass layers.
When glass reaches a temperature of between 1100 F (600 C) and 1300 F (700 C) it slowly becomes soft enough to move around. At this temperature introducing a bubble squeeze segment into the fusing schedule can minimize any trapped air bubbles that may be present between glass layers.
A slow firing segment from 1100 F (600 (c) to about 1240 F (670 C) held at 1240 F for a set period of time will allow air bubbles to hopefully escape from between layers of glass.