DSS-Co.01.04 — Chemical Attack Spots (cleaner/acid/alkali on sputtered stacks)

Localized appearance changes (spots, rings, blooms) on a sputtered low-E / multilayer functional coating caused by chemical interaction (e.g., acidic brick wash, alkaline cleaners, aggressive solvents). On exposed coated faces (#1 or #4, as applicable), these present as sheen/colour/density shifts or matte “burns” without chip-flank fracture morphology. On cavity faces (#2/#3), similar signatures are between panes and therefore not addressable in place; classification is driven by location/condition. Under VIS, coating appearance on worked surfaces is treated as an appearance cue; acceptance for coated faces is handled explicitly in the coatings note of §6 (coating anomalies on the worked surface are not permitted at acceptance).

• Discrete spots or halos with altered sheen/colour; strongest in raking light/oblique sweep; may exhibit a faint ring at the perimeter.
• Patchy mottle from cleaner pooling, drips, or wipe paths; often correlates with application patterning.
• Persists after Non-Invasive Reveal (clean & dry); if removal occurs, the cue was a face film/residue (R-family), not a coating change.

Surface-catch class (MSRT):

• Expect SC-0 (none) for purely optical coating changes; SC-1 (slight) is possible if subtle micro-texture is present within the spot. Perform one light, non-marring pass only; on coated faces prefer a polymer stylus or rely on visual cues to avoid coating disturbance. MSRT supports classification only, not acceptance.

Reveal / lighting / geometry:

• Complete Non-Invasive Reveal (clean & dry; no blades/chemicals) before evaluation. Inspect at 12 / 36 / 72 in, normal incidence + oblique sweep (~60°-120°) with raking light, per VIS.

Location / access:

• Confirm the observation is on the exposed coated face (not in an IGU cavity). Record pane ID and surface numbering (#1-#4; mark laminate-internal if applicable) on forms; note “functional coating present on worked surface? (Y/N/Unknown)”. Use fixed parallax to identify between-pane look-alikes (CAT-5).

• If on exposed coated face (#1/#4):
• CAT-1 - non-tactile spot/halo with SC-0; no edge morphology at acceptance geometry.
• CAT-2 - faint micro-texture within the spot yielding SC-1 (slight).
• CAT-3 - pronounced modeled micro-texture/patch detectable at standard distance, still without chip flanks. (Assign CAT by visibility convention + MSRT outcome; cause is informative only.)
• If on cavity face (#2/#3) or otherwise inaccessible: CAT-5 - out of in-place scope by location; document and refer per project protocol (fabricator/manufacturer/warranty).
• Acceptance split (critical): Even if classified CAT-1...CAT-3, coating anomalies on the worked surface are not permitted at acceptance under the VIS coatings note (§6); treat acceptance as appearance-only at required distances/angles and do not introduce new coating changes.

• For true chemical attack spots on coatings, glass-face relief is typically nil at MSRT (SC-0; occasionally SC-1 if micro-texture is present). Numeric μm depth is not determinative for coating-appearance anomalies; acceptance remains appearance-based.

• vs. Face films/residues (R-family): Residues change with Non-Invasive Reveal; a true coating attack persists after reveal.
• vs. Mechanical scratches (M.01): Scratches show chip flanks/micro-chipping and SC-2 along a line; chemical spots are area-based, boundaryless or haloed, and generally SC-0/SC-1.
• vs. IGU internal haze/volatiles (A.01.01): Internal cues show fixed parallax and map to CAT-5 by location.
• vs. Spandrel/back-paint mottle (Co.04.01): Spandrel mottle is pane-scale system appearance; chemical spots on sputtered stacks are localized coating changes on the worked face.

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique, include raking; add macro frames showing spot/halo without chip flanks or a worked transition edge. Note reveal status and lighting/time.
• MSRT result: Record SC class (expect SC-0; SC-1 if micro-texture). One pass, non-marring; on coated faces prefer polymer stylus or visual-only.
• Forms: Pane ID; surface numbering; worked surface Y/N; functional coating present on worked surface? (Y/N/Unknown); geometry checklist; photos attached.

Attempting to “blend out” a coating spot can enlarge the anomaly and create a worked region/transition edge, which VIS disallows at acceptance (CAT-0...CAT-4). Confirm reveal, SC class, and location before any action.

• Co.01.04 Chemical Attack Spots (sputtered stack) - Localized spot/halo at #__ verified after Non-Invasive Reveal; MSRT = SC-0/SC-1 (no chip flanks). If on #1/#4, classify CAT-1...CAT-3 by visibility/texture; acceptance note: coating anomalies on the worked surface are not permitted (VIS coatings note). If on #2/#3, CAT-5 by location (between panes); document and refer. Photo set at 12/36/72 in (normal + oblique + raking); surface numbering and coating presence recorded.