What is compatible glass?
In the world of glass fusing, two glasses are “compatible” if they can be fused together and have no undue stresses in the finished piece that will lead to fracturing. Glass, like most materials, expands when heated and contracts when cooled. The viscosity (resistance to flow) characteristics of a glass are equally as important. Together, these two properties determine whether one glass will “fit” another. If two glasses that do not expand or contract similarly are fused together, unwanted stresses will develop in the glass. The greater the difference in contraction or expansion of the fused glasses, the greater these stresses become. If the stresses are too great, the two pieces will break apart upon cooling. Expansion affects the compatibility predominantly in the lower temperature rangebelow the strain point. Viscosity properties affect compatibility predominantly in the middle temperature rangefrom the strain to the annealing point.
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 in expansion. The fact that a glass company is making a variety of glass products does not mean that they will be compatible amongst each other. The Thermal expansion of a particular glass can be changed by the addition of metallic oxides, which give the glass its different colors. Specific compositions need to be mixed for each color of glass to be compatible with each other.
