DSS-E.04.03 — Curtain Wall Runoff Staining (Adjacent Materials Interactions)

Curtain wall runoff staining (adjacent materials interactions) is an appearance change on glass caused by moisture transporting constituents from neighboring materials-sealants, gaskets, metals, masonry, timber, coatings-onto the glass surface during rain/dew/condensation events. It presents as vertical run curtains, bay-repeat streaks, and tone-specific veils (e.g., brown tannins, orange/rust oxides, black bitumen, siloxane halos). Classification is appearance-only per VIS (method-agnostic). Inspect after Non-Invasive Reveal under VIS lighting/geometry; record surface numbering and worked-surface status.

• Bay-to-bay repetition: runs align beneath consistent material interfaces (spandrel sill, parapet cap, masonry copings, signage rails).
• Color cues by source: orange-brown below weathering steel or rusty hardware; tea-brown below timber/tannins; black below bitumen/roof tars; dark grey below zinc/galvanized wash; clear-to-greasy halos adjacent to silicone/EPDM.
• Edge blooms where water dwells at gaskets or sealant laps; joint-intensified bands.

Surface-catch class (MSRT)

• SC-0 where deposits are film-only and lift on reveal.
• SC-1 in zones of long-cycle deposition producing very shallow micro-texture; SC-2 suggests misclassification-check Ch.03.03 mineral etching or M.02 abrasion.
• 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

• Vertical curtains / drip legs tied to particular upstream materials; tonal cast reflects source chemistry; no chip-flank sparkle (not scoring); no fused pits (not hot particle).
• In raking: sheen discontinuities along run edges; sometimes wetting anomalies near elastomers or silicone bleed.

Viewing / lighting

• Evaluate clean & dry at 12 / 36 / 72 in, normal and oblique sweep (~60°-120°); use raking to reveal edge definition, tone, and any interior matte. Record distances/angles in-frame.

Location / access

• Record pane ID and surface numbering (#1-#4; laminate-internal). Typically presents on outboard (#1) faces beneath caps, copings, spandrels, masonry, timber, roofing interfaces. Between-pane mapping by parallax on #2/#3 → CAT-5 by location.

Mechanism cue (context)

• Presence of corroding metals, tannin-rich timber, bitumen/tar, silicones/EPDM, masonry wash above flow paths; staining on frames/sills corroborates source.

Assign CAT by visibility at acceptance geometry and MSRT after a reveal patch. Depth values are indicative-field measurement not required.

• CAT-1 (Benign / non-relief): Tone-specific run curtains comprised of residue only; SC-0; primarily angle/raking visible; lifts on reveal. Indicative relief: 0-10 μm.
• CAT-2 (Light): Persistent toned runs post-reveal with localized SC-1 (incipient micro-texture); limited standard-view impact. Indicative relief: ~10-40 μm.
• CAT-3 (Moderate): Wide-area, bay-repeat staining legible at standard distance with consistent SC-1 inside curtains; indicates long dwell/high frequency. Indicative relief: ~40-120 μm.
• Reclassify when: White/grey crystalline rims or etched halos dominate → Ch.03 Mineral system; linear wipe/iridescence → R.04.01 Detergent/surfactant film; metallic speck/pits → Th.01.02 grinder spark embed.
• 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. E.04.01 recurring drip/run (generic): E.04.03 is used when source chemistry imparts distinctive tone/halo attributable to specific adjacent materials.
• vs. Mineral system (Ch.03): Minerals show crystalline ring/rims and may etch; runoff staining from materials can be chromatic (tannin, oxide, bitumen) and film-dominant-verify with reveal + MSRT.
• vs. Coating anomalies (Co-family): Coating issues are planar/patchy on designated faces, not gravity-driven from upstream materials.
• vs. HVAC/kitchen films (R.04.03/04): Those track air paths and feel oily/tacky; material runoff follows gravity, has source-specific color, and repeats bay-to-bay.

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique; raking macros of run edges, tonal character, and interior matte; context frames showing upstream materials and pane-to-pane repetition. Record distance/angle in-frame.
• MSRT result (substrate): After a small reveal test patch, 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.04.03 Curtain Wall Runoff Staining (Adjacent Materials Interactions) - Toned run curtains beneath [material: weathering steel / timber / bitumen / silicone / masonry] on surface #___; post-reveal test patch shows [SC-0/SC-1]; visible at [12/36/72 in] under VIS geometry. Morphology: bay-repeat vertical runs, source-specific color/halo, no chip-flank sparkle, no pits. Classification: CAT-[1/2/3] by visibility and SC-class; reclassify to Ch.03 if crystalline rims/etch dominate, or to R.04.01 if wipe/iridescence patterns are present; CAT-5 if between-pane or coating-side loss on the surface to be worked. Forms + photo set attached; acceptance per VIS-A §6.