What causes crazed glass in a fire incident?

Crazed glass refers to a condition where the glass surface has fine cracks or fractures, which often occur in a fire incident due to rapid temperature changes. When glass is subjected to intense heat, it expands. If it then encounters a rapid cooling effect—such as being doused with water, or when cooler air suddenly contacts the hot surface—it cannot contract at the same rate, leading to stress within the material. This stress can ultimately result in the formation of these tiny cracks, or "crazing," on the surface of the glass.

The phenomenon is particularly notable in fire incidents, where fluctuations in temperature are not only common but often extreme. Therefore, recognizing that rapid cooling is the primary cause of crazed glass helps in understanding the impact that thermal shock can have in post-fire analysis, especially in the context of evaluating evidence and determining the fire's dynamics.