Mineral-rich material deposited on exposed glass as mineral-bearing water evaporates. It remains a surface deposit only when controlled removal exposes clean glass with no modeled micro-texture (SC-0).
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Meaning and boundaries
A deposit sits on the surface. Spotting pattern or product response alone does not prove staining or etching; classify etching only when a clean, dry substrate retains modeled micro-texture.
Why it matters in glass restoration
Correct classification determines whether cleaning, deposit removal, polishing, or replacement is appropriate.