Fusing
Fusing is the process of joining pieces of compatible glass by heating them in a kiln until they become a single piece. It is the basis of fused glass, and is used for plates, tiles, jewellery, panels and sculptural pieces.
The result depends on how high and how long the kiln is heated. At a lower temperature the pieces stick together but keep their shape, called a tack fuse. At a higher temperature they melt into each other, flatten and form a smooth surface, called a full fuse. The temperatures for these stages are typically in the region of 730 to 820°C, depending on the glass.
All of the glass in a fused piece must have the same coefficient of expansion, and it must be annealed carefully, or it will crack as it cools.