| What is Fusion? Fusion is the process of heating a material or materials such as glass, so that separate pieces melt and unite together as one. What is compatible glass? Two glasses are compatible if they can first be fused together, and after proper cooling to room temperature, have no undue stresses in the finished piece that will lead to fracturing. The compatibility of a particular glass is a function of both viscosity (resistance to flow) and expansion (change in size as temperature changes). Two different glasses can be compatible if the viscosity and the expansion are the same, or if a strain caused by a mismatch due to viscosity is canceled out by the strain caused by the mismatch expansion. What is annealing? Annealing is the process used to relieve stress in glass during the cooling stage. This is accomplished by maintaining a consistent temperature through the entire body of glass. The glass is held at a temperature just below the temperature at which that specific glass will start to move due to heat. Heat is transmitted very slowly through glass, so the glass has to be held at the annealing temperature any where from one hour to day or weeks. The amount of time depends upon the thickness of glass. The glass is brought down in temperature while maintaining a consistent temperature throughout the body of glass. The thicker the glass the slower it will lose heat from its center. When the kiln cools down faster than that which is required by the thickness of the glass, heat is applied to the top or bottom of the glass to maintain a consistent cooling gradient throughout the body of glass. Stressed caused by incompatibility of glass can not and will not be relieved by annealing, and will remain when cooled. What is hot working? Hot working is the method used to manipulate and form hot molten glass with tools, paddles, blow pipes, and punties (rods to hold, move, and spin the hot glass shape or vessel while it is being worked and reheated). Hot working techniques with fusible glass include: blowing, raking, or feathering with a metal pointed tool, pulling or manipulating outside of the kiln or furnace. The fused glass can also be manipulated within the fusing kiln by opening the kiln and grabbing, pushing, and lifting the hot glass with tools. Kevlar gloves, hoods, and face shields are used as necessary to provide protection from the intense heat. When using a tool to manipulate the glass inside the kiln you should always first turn the kiln off. What other processes are used to make and finish a piece of work? Slumping is done by firing the glass pieces which are placed on top of a mold or shape. By heating the glass to a temperature hot enough for the glass to move, the glass assumes the shape of the mold by slumping (bending) into or over it. Dishes, masks, trays, torsos, light fixtures, and other shapes are created this way. |