The Stages of Crizzling
Stage 1: Initial Stage
Presence of alkali on the glass gives the surface a cloudy or hazy appearance. Tiny droplets or fine crystals can form if there is high (above 55%) or low (below 40%) relative humidity. Glass may feel slippery or slimy. Washing will remove alkali from the surface and the glass will look great.
Stage 2: Incipient Crizzling
Similar symptoms to stage one, but the haziness remains after washing. Close examination using low, raking light may reveal very fine cracks which look like tiny silvery lines or shimmering rays.
Stage 3: Full-blown Crizzling
Cracking has progressed, is easily visible with the naked eye, and often takes on a very uniform appearance.
Stage 4: Advanced Crizzling
Cracking is even deeper. Spalling may occur leading to loss of small chips or flakes from the surface.
Stage 5: Fragmentation Stage
The final stage is observed when the crizzling is so deep that the object cannot retain its structural integrity and separates into fragments. This may happen without any outside intervention or by impact or additional strain to the glass such as that experienced with regular handling.