Fusing is a process where 2 or more pieces of glass are heated to above the melting point and fuse together. Air is inherently trapped between the glass and bubbles form as a part of the process. Different types of glass have different expansion and contraction rates so only similarly made glass can be fused together. The trapped air disqualifies this glass from being tempered however it can be laminated for additional safety specifications.
Fused glass is used frequently in horizontal applications such as counter tops or in vertical applications covering a wall. Because of its semi-translucency, it is often backlit intensifying the complexity of its fired beauty.