DSS-A.03.03 — Adhesive / Chemical Attack from Behind (mirror back-coating)

Localized under-glass staining, bloom, or matting visible through the mirror that originates from adhesives, mounting compounds, cleaners, or chemicals acting on the back-coating/reflective layer (behind the glass). The cue is not on the exposed viewing face and therefore is not addressable in place; classification is location/condition-driven. Identify the product as a mirror/back-coated glass and apply VIS surface-numbering/context rules; acceptance under VIS pertains to the exposed surface only.

The Glass Restoration Standards...

• Under-glass diffuse bloom (whitish/grey) or discolored patches behind the glass adjacent to adhesive points, clip/fastener locations, or at cleaner/solvent contact zones on the back.
• No change after Non-Invasive Reveal of the viewing face; no transition edge or chip-flank morphology on the face.
• May co-exist with edge blackening or spot corrosion elsewhere on the same lite (see A.03.01 / A.03.02 for related back-side phenomena).

Surface-catch class (MSRT):

• On the exposed viewing face, record SC-0 (none). Perform one light, non-marring pass only to support classification; do not abrade. If a face functional coating is present/suspected, prefer a polymer stylus or rely on visual/location cues.

Reveal / lighting / geometry:

• Evaluate clean & dry after a Non-Invasive Reveal; inspect at 12 / 36 / 72 in, normal incidence + oblique sweep (~60°-120°) under raking light per VIS. Back-side attack remains unchanged by reveal.

Location / access:

• Confirm the observation sits behind the glass (back-coating) rather than on the worked face. On forms, record pane ID and product context; acceptance pertains to the exposed surface under evaluation. Use VIS surface-numbering on documentation where applicable.

• CAT-5 - Out of in-place scope when the appearance change arises in the back-coating system (behind the glass). Document and refer per project protocol (fabricator/replace). Face-side MSRT and numeric depth are non-determinative; location controls.
• If any face-side condition is also present (scratches, films, coating rubs), classify that separately under M/Co/R families by CAT; do not let the back-side condition set face acceptance.

Not applicable to the exposed face; deterioration occurs behind the glass. On the viewing face: SC-0 expected; numeric depth (μm) is not used for back-side classification.

• vs. Front-face residues/films (R-series): Face films respond to Non-Invasive Reveal; back-side attack does not.
• vs. Coating anomalies on the worked surface (Co-series): Coating rub/patchiness occurs on the exposed face and is disallowed at acceptance on coated surfaces; back-side attack is behind the glass (location-driven CAT-5).
• vs. IGU between-pane artifacts (A.01 family): IGU conditions show fixed parallax between #2/#3; mirror back-coating attack is behind a back-paint/reflective system, not a cavity condition. Use product context + documentation forms to avoid cross-family mis-ID.

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique, raking; include one macro confirming under-glass character (unchanged by reveal) and one context frame showing proximity to adhesive pads/clips/chemical exposure zones.
• MSRT result (face): SC-0; one pass; non-marring; polymer stylus preferred when any face functional coat is present/suspected.
• Forms: Pane ID; product & context (mirror/back-coated); reveal status; lighting/time; geometry checklist; surface numbering where applicable.

Attempting to “polish out” an under-glass cue creates unnecessary worked regions (visible transition edge) on the face that VIS disallows at acceptance (CAT-0...CAT-4). Keep classification appearance-only for the face unless true face-side damage exists.

• A.03.03 Adhesive / Chemical Attack from Behind (mirror back-coating) - Diffuse bloom/discoloration behind the glass adjacent to adhesive/cleaner contact points; unchanged by Non-Invasive Reveal; MSRT on viewing face = SC-0. Location/condition places cue behind the exposed surface; classified CAT-5 (out of in-place scope) per VIS. Documented at 12/36/72 in with normal + oblique + raking; product context recorded.