A patterned visual effect that can appear in heat-treated glass under polarized light because the residual stress distribution changes how light passes through the lite.
GlassRenu · Educational illustration
Meaning and boundaries
The visible pattern is not a surface stain, coating discoloration, or proof that the glass is structurally defective.
Why it matters in glass restoration
Correct identification prevents unnecessary polishing and avoids promising removal of a stress-related optical effect.
Related terms
References
- ASTM International — ASTM C1048-25: Heat-Strengthened and Fully Tempered Flat Glass
Publisher’s original source - National Glass Association — Engineering Standards Manual, Tempering Division
Publisher’s original source - National Glass Association — Iridescence in Heat-Treated Architectural Glass
Publisher’s original source