Visible surface damage that can be felt with a light pass of a clean, dry fingernail but remains a clean, isolated, continuous scratch or groove without visible chipping or flecking along its edges.
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Meaning and boundaries
A tactile mark with chip flanks, edge flecking, pits, fused particles, or rough breakout is Category 4. An active crack, inaccessible condition, or non-restorable construction is Category 5.
Why it matters in glass restoration
The tactile catch confirms greater relief than Category 2 and calls for controlled material removal, heat management, distortion control, and documented inspection of the scratch edges.
Related terms
References
- ASTM International — ASTM C1036-25: Standard Specification for Flat Glass
Publisher’s original source - National Institute of Standards and Technology — Fractography of Ceramics and Glasses, 3rd edition
Publisher’s original source - GlassRenu — Visual Inspection Standards for Architectural Glass Damage Assessment and Restoration (VIS-A / VIS-DA)
Publisher’s original source