DSS-Ch.05.02 — Reducing Agent Discoloration

Reducing agent discoloration is an appearance change caused by reducing chemicals (e.g., bisulfites/metabisulfites, thiols, ammonia-based reducers/neutralizers, specialty graffiti/bleach neutralizers) contacting glass and dwelling/drying on the surface. Outcomes range from optical tone/contrast shift to very shallow, non-directional micro-texture within wipe or run geometries. Classification is appearance-only per VIS (method-agnostic). Inspect after Non-Invasive Reveal under VIS lighting/geometry; record surface numbering and worked-surface status. Treat fresh/unknown liquids per site safety.

• Wipe-bounded patches with overlap lines or sheeted runs/legs below treatment areas (e.g., after neutralizing oxidizers or cleaning masonry/metal stains).
• Specular: dull or slightly yellow/grey cast versus surrounding glass.
• Raking: very fine modeled micro-texture may appear in stronger events; many remain optical only.

Surface-catch class (MSRT)

• Often SC-0 (optical only).
• SC-1 (slight) can occur where reducers dwelled in heat/sun or were used concentrated; SC-2 is rare.
• Perform one light, non-marring pass on a representative interior area; polymer stylus if a coating is suspected. MSRT supports classification only.

Visual signature

• Footprint-bounded veils with wipe directionality or run legs; interiors non-directional (not linear scoring).
• No chip-flank sparkle (not mechanical); no discrete fused nodules/pits (not hot-particle).

Viewing / lighting

• Evaluate clean & dry at 12 / 36 / 72 in, with normal incidence and oblique sweep (~60°-120°); use raking light macros to confirm presence/absence of micro-texture. Record distances/angles in-frame.

Location / access

• Record pane ID and surface numbering (#1-#4; laminate-internal). If fixed parallax indicates between-pane condition, classify CAT-5 by location (out of in-place scope) and refer.

Mechanism cue (context)

• Evidence of neutralization steps following oxidizer or acid clean-downs; sulfite/amine reducers, ammonia-bearing products, or specialty graffiti neutralizers; notes of sun/heat during dwell.

Assign CAT by appearance + MSRT + morphology (three-part cueing). Depth/relief values are indicative-field measurement not required.

• CAT-1 (Benign / non-relief): Optical tone/contrast shift only, SC-0; visible mainly at certain angles/raking; minimal at standard view. Indicative relief: 0-10 μm (optical).
• CAT-2 (Light): Very shallow modeled micro-texture, SC-1, confined to wipe/run footprint; limited impact at standard view. Indicative relief: ~10-40 μm.
• CAT-3 (Moderate): Broader matte/veil legible at standard distance, SC-1 to SC-2; repeat passes/overlaps evident. Indicative relief: ~40-120 μm.
• CAT-4 (Severe): Uncommon for reducers alone; if pronounced matte fields occur, consider mixed chemistry (alkaline + reducer stack) and re-evaluate under applicable DSS. Indicative relief: ~120-300 μm+.
• CAT-5 (by condition/location): Between-pane/inaccessible by parallax, integrity indicators (active cracks/pane movement), or confirmed functional-coating loss on the surface to be worked → CAT-5.

CAT is appearance-based; acceptance is separate under VIS-A at 12/36/72 in. Do not “probe” with MSRT.

• vs. Bleach/peroxide shadowing (Ch.05.01): Oxidizer shadows are often whiter; reducer discoloration trends neutral/yellow-grey; both may be optical (SC-0) or SC-1 with dwell/heat.
• vs. Degreaser/alkaline burn (Ch.04.03): Alkaline burn shows grainier micro-texture and sheet/run geometries; reducer discoloration frequently softer and less granular.
• vs. Adhesive remover staining (Ch.04.02): Adhesive removers are tied to label/film sites with distinct overlap lines; reducer stains map to neutralization zones after chemical cleaning.
• vs. Mineral staining/etch (Ch.03): Mineral issues reflect spray arcs/rings/runoff and may leave ring halos; reducer stains follow wipe sheets around treated substrates.
• vs. Coating anomalies (Co-family): Coating rub/patchiness shows sheen/color shift without chemical context; on a worked coated surface, any anomaly is not permitted at acceptance (VIS §6.2.e). Confirm coated face.

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique; include raking macros of footprint interiors and overlap/run edges; add context frames (neutralizers/containers, work zone). Record distance/angle in-frame.
• MSRT result: One light, non-marring pass on footprint interior; record SC-class (SC-0/SC-1/SC-2). Polymer stylus if coating is suspected.
• Forms: Pane ID; product family & surface numbering; worked surface Y/N; functional coating present on worked surface? (Y/N/Unknown); reveal status; lighting/time; geometry checklist; photos attached.
• Acceptance split: Post-restoration acceptance per VIS-A §6; classification ≠ acceptance. Coated-face appearance rules apply per VIS §6.2.e.

• Ch.05.02 Reducing Agent Discoloration - Footprint-bounded veil on surface #___ with [SC-0/SC-1/SC-2], visible at [12/36/72 in] under VIS geometry after Non-Invasive Reveal. Morphology: soft wipe/run interior, overlap lines; no chip-flank sparkle, no discrete pepper. Classification: CAT-[1/2/3/4] by relief/visibility; CAT-5 if between-pane, integrity cues, or coating-side loss on the surface to be worked. Forms + photo set completed; acceptance per VIS-A §6 (separate).