DSS-Ch.01.03 — Organic-Acid Residues (avian/biogenic high acidity)

Organic-acid residues (e.g., avian droppings, certain plant/biogenic exudates) can produce localized chemical attack on glass, especially under heat + dwell (sun-exposed façades). Resulting appearance ranges from tone/shine shift to subsurface micro-texture (“frost”) with run/pool edges. Classification is appearance-only per VIS (method-agnostic). Inspect after Non-Invasive Reveal under VIS lighting/geometry; record surface numbering and worked-surface status on Forms: Treat fresh residues as biohazard; document visually per site safety protocols.

• Irregular patches/ovals with feathered margins, sometimes a central thicker pool and thin run-legs below.
• After reveal, a soft haze remains within the former residue footprint; in raking light, affected zones read as modeled micro-texture (non-directional).
• Strongest on sun-heated lites where acid dwell is prolonged; may align with ledge/perch lines or mullion drip paths.

Surface-catch class (MSRT)

• SC-0 if only a faint optical/cleaning shadow remains (no relief).
• SC-1 (slight) to SC-2 (clear) within etched footprints after reveal when micro-texture developed.
• Perform one light, non-marring pass; polymer stylus if a coating is suspected. Do not abrade. MSRT supports classification only.

Visual signature

• Footprint-bounded patch with soft, organic geometry (no letterforms); may show runs/tear-drop legs from gravity.
• No chip-flank sparkle or linear continuity typical of mechanical scoring; no discrete pits/nodules typical of hot-particle peppering.

Viewing / lighting

• Evaluate clean & dry at 12 / 36 / 72 in, using normal incidence and oblique sweep (~60°-120°) with raking light to reveal micro-texture and footprint boundaries. Record distances/angles in-frame.

Location / access

• Record pane ID and surface numbering (#1-#4; laminate-internal). If fixed parallax indicates a between-pane presentation, classify CAT-5 by location and refer.

Mechanism cue (context)

• Nearby perches/ledges/signage; nesting sites; overhead tree canopies; sun-exposed orientations increasing temperature/dwell.

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

• CAT-1 (Benign / non-relief): Sheen/tone shift only, SC-0 after reveal; visible mainly in raking at close/standard view. Indicative relief: 0-10 μm (optical).
• CAT-2 (Light): Subtle etched footprint, SC-1; limited impact at standard view; footprint edges soft. Indicative relief: 10-40 μm.
• CAT-3 (Moderate): Clear detect (SC-2) with modeled micro-texture legible at standard distance; defined pool/run edges. Indicative relief: 40-120 μm.
• CAT-4 (Severe): Pronounced frosted patch over a larger footprint or repeated incidents; distinct at standard & wide-field views. 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 (out of in-place scope).

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

• vs. Muriatic/brick-wash fallout (Ch.01.02): HCl shows gravity-organized sheets/drip trains from construction context; biogenic footprints are localized organic patches with softer edges and perch context.
• vs. Acid-etch graffiti (Ch.01.01): Graffiti presents intentional stroke geometry/drip legs; organic residues lack letterforms and show pool-centered footprints.
• vs. Alkaline cement/mortar etch (Ch.02.01/.02): Alkaline attacks can leave chalky crust/efflorescence and grainy texture; organic acid footprints present smooth modeled micro-texture without alkaline crust.
• vs. Residue films (R-family): Detergent/soot films remove at reveal and read SC-0; persisting SC-1/SC-2 indicates etch.
• vs. Coating anomalies (Co-family): Coating rub/patchiness has sheen/color shift but lacks etch relief; on a worked coated surface, any anomaly is not permitted at acceptance (VIS §6.2.e).

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique; include raking macros resolving footprint interior + edge; add context frames (perch/ledge/tree canopies). Record distance/angle in-frame.
• MSRT result: One light, non-marring pass on a representative area; record SC class (SC-0/1/2). Prefer polymer stylus if a 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 at 12/36/72 in; classification ≠ acceptance. Coated-face appearance rules apply per VIS §6.2.e.

• Ch.01.03 Organic-Acid Residues (avian/biogenic) - Footprint-bounded patch with [SC-0/SC-1/SC-2] on surface #___, visible at [12/36/72 in] under VIS geometry after Non-Invasive Reveal. Morphology: modeled micro-texture within pool/run-edge; no chip-flank sparkle or linear scoring. 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).