A fusers favorite Wissmach frits are made from clean-crushed and screened Wissmach sheet glass. Frits may be used in hot glass work such as pate de verre cast molds, flameworking, kiln-casting, and other techniques with these versatile little grains. Great for jewelry and projects Reactive blue fine frit, packaged in a wide-mouth 1 lb jar. 96 COE. In glass fusing, we call glass "reactive" when the metals in one glass react with the metals in another and as a result, create a fine line where the two colors meet.