Rule of Halves
This rule is important to know for successful glass cutting. A score is more likely to run properly when there are equal amounts of glass on either side of it. This is particularly important for cutting strips of glass.
Devitrification ("devit") is the growth of crystalline structures within or on the surface of glass. ("Vitri" = glass; "devitrification" = the process of becoming un-glasslike). Devit can result from firing too slowly through the devitrification range of temperatures. It can also result from firing contaminants like oils and fingerprints onto glass and thus seeding the growth of crystals.