Fusing is the process of joining two or more kinds of glass through melting. It is a general term used to describe several techniques for creating flat objects layers of glass. Tack fusing and full fusing are all fusing techniques. The main difference between tack fusing and full fusing is the operational temperature, which lends different results.
Slumping is the technique of imparting shape to the glass. The glass is to deform quickly and visibly underweight and adhere to surfaces once the softening point is reached. At this point, the viscosity and surface tension of the material decrease while fluidity increases, resulting in changes in the shape from the weight of the glass, or in other words, the effect of gravity.