What is the effect of rapidly cooling glass?

When glass is rapidly cooled, a process called thermal shock occurs. This happens because different areas of the glass cool at different rates, leading to a disparity in contraction. As a result, internal stresses can build up, causing the glass to crack or develop crazing, which refers to fine cracks that appear on the surface. This fragility is particularly evident in glassware and glass used in construction, where sudden temperature changes can lead to catastrophic breakage.

The other options do not accurately describe the effect of rapid cooling on glass. For instance, glass does not become more flexible with rapid cooling; instead, it becomes more brittle. Discoloration can occur in glass due to other factors like impurities or exposure to certain chemicals or heat, but it is not a direct result of rapid cooling. Similarly, while thermal resistance can be influenced by various factors in glassmaking, rapid cooling itself does not enhance thermal resistance; rather, it can compromise the structural integrity of the glass.