DSS-E.03.04 — Avian Residue Acid Shadow

Avian residue acid shadow is an appearance change on glass produced by bird droppings (mixture of uric acid/urates, water, organics) that deposit as discrete splats and may bleach or dull the underlying glass after removal, leaving a color/shine “shadow.” High dwell time, sun/heat, and repeated incidents increase the likelihood of near-surface alteration. Classification is appearance-only per VIS (method-agnostic). Inspect after Non-Invasive Reveal under VIS lighting/geometry; record surface numbering and worked-surface status.

• Discrete splats (10-50+ mm) with radial feathering and white urate crust; occasionally mixed brown/green organics.
• Run-legs from the splat on sloped panes or after dew; edge pooling at micro-texture inside the splat area.
• After residue lift: pale “ghost” or shadow area (reduced gloss, slight color shift).

Surface-catch class (MSRT)

• SC-0 for fresh/dry crust (residue on top).
• SC-1 localized if long dwell + heat produced very shallow micro-texture or trapped grit; SC-2 is atypical-if present after true residue lift, reassess for Ch.01 (acid attack) or Ch.03.03 (mineral etching).
• Perform one light, non-marring pass on a small revealed test patch (substrate). Use a polymer stylus if a functional coating is suspected. MSRT supports classification only.

Visual signature

• White crystalline/opaque urate crust with radial feathers and splat edge ring; may show brown/green organic center.
• Post-lift shadow: subtle loss of specular “snap” or color/shine change confined to the splat footprint.
• No chip-flank sparkle, no fused nodules.

Viewing / lighting

• Evaluate clean & dry at 12 / 36 / 72 in, normal incidence and oblique sweep (~60°-120°); use raking macros to show splat geometry, edge ring, and post-lift shadow boundary. Record distances/angles in-frame.

Location / access

• Record pane ID and surface numbering (#1-#4; laminate-internal). Common on outboard (#1) horizontal/near-horizontal surfaces (canopies, sills, skylights), signage ledges. Between-pane by parallax on #2/#3 → CAT-5 by location.

Mechanism cue (context)

• Avian perches above (sign letters, mullion caps), nesting/roost zones, overhangs; repetition beneath common perch points; co-evidence on frames/sills.

Assign CAT by visibility at acceptance geometry and MSRT after a true residue lift test on a contained patch. Depth values are indicative-field measurement not required.

• CAT-1 (Benign / non-relief): Discrete splat residues that fully lift on reveal; SC-0; visible mainly at angle/raking. Indicative relief: 0-10 μm (optical film/crust only).
• CAT-2 (Light): Post-lift shadow (minor gloss/tone change) with localized SC-1; limited standard-view impact. Indicative relief: ~10-40 μm (incipient near-surface change).
• CAT-3 (Moderate): Multiple/overlapping splat shadows legible at standard distance, scattered SC-1; indicates long dwell, heat exposure, or repeated incidents. Indicative relief: ~40-120 μm
• Reclassify when: After true residue removal, if modeled matte persists with SC-1/2 beyond the splat footprint → consider Ch.01 (acid attack); if crystalline ring/etch halo consistent with hard-water dominates → Ch.03.03; if linear abrasion from cleaning attempts remains → M.02 abrasion fields.
• CAT-5 (by condition/location): Between-pane/inaccessible by parallax, integrity indicators, 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 abrade to “force” a response during classification.

• vs. Mineral staining/etch (Ch.03): Minerals present white/grey crystalline rings with run mapping; avian shows distinct splat morphology with urate crust and radial feathering.
• vs. Organic sap (E.03.03): Sap is amber/tacky with stringers; avian is white/grey crust with organic center and splat geometry.
• vs. Detergent/surfactant film (R.04.01): Detergent shows wipe streaks/iridescence; avian shows radial splash, ring, and localized post-lift shadow.
• vs. Atmospheric matte (E.01.02): Atmospheric is global/non-directional; avian is localized to splat footprints under perches.

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique; raking macros of splat edge, feathering, post-lift shadow boundary; context frames showing perch/nesting features above. Record distance/angle in-frame.
• MSRT result (substrate): After a small reveal test patch and true residue lift, perform one light, non-marring pass; record SC-class (SC-0/SC-1/SC-2).
• 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 when the worked surface is a factory functional coating.

• E.03.04 Avian Residue Acid Shadow - Discrete splat with urate crust on surface #___ beneath [perch/letter/cap]; post-reveal test patch shows [SC-0 residue / SC-1 shadow]; visible at [12/36/72 in] under VIS geometry. Morphology: radial feathering, edge ring, localized post-lift shadow, no chip-flank sparkle, no pits. Classification: CAT-[1/2/3] by visibility and SC-class; reclassify per notes if broader acid etch or mineral halos dominate; CAT-5 if between-pane or coating-side loss on the surface to be worked. Forms + photo set attached; acceptance per VIS-A §6.