DSS-E.02.01 — Wind-Borne Sand Abrasion (Eolian)

Wind-borne sand abrasion is an appearance change on glass caused by air-entrained mineral particulates (silica, feldspar, grit) scouring exposed faces under sustained winds. It presents as directional frosting/haze, micro-pitting, and fine linear incisions concentrated on windward elevations and edge “blast” zones near frames and corners. Classification is appearance-only per VIS (method-agnostic). Inspect after Non-Invasive Reveal under VIS lighting/geometry; record surface numbering and worked-surface status.

• Matte/frosted fields with grain-aligned directionality (prevailing wind).
• Heavier strike at leading edges, mullion reveals, parapet-level lites, and near grade in arid sites.
• Under raking: uniform scatter from micro-texture, interspersed with fine, shallow incisions; may show height gradient (stronger low, tapering upward).

Surface-catch class (MSRT)

• Commonly SC-1 (fine micro-texture) progressing to SC-2 where micro-pits/incipient incisions are present; SC-0 only at earliest film-only stages.
• 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

• Directional matte (frosted look) with grain-wise streaking; no oily gloss, no wipe arcs.
• Under oblique sweep, sparkle is absent (not chip-flank sparkle) but catch is tactile where incisions/pits exist.

Viewing / lighting

• Evaluate clean & dry at 12 / 36 / 72 in, normal and oblique sweep (~60°-120°); use low-angle raking to reveal directional micro-texture and localized edge blast. Record distances/angles in-frame.

Location / access

• Record pane ID and surface numbering (#1-#4; laminate-internal). Predominant on outboard (#1) faces. Between-pane by parallax on #2/#3 → CAT-5 by location.

Mechanism cue (context)

• Arid/coastal dunes, construction sites with exposed soils, high-wind corridors, sand storms; adjacent abrasive landscaping media or unpaved lots.

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

• CAT-2 (Light): Incipient directional haze; SC-1 (micro-texture), minimal standard-view impact; isolated shallow ticks. Indicative relief: ~10-40 μm.
• CAT-3 (Moderate): Distinct directional frosting legible at standard distance; consistent SC-1 with scattered SC-2 from micro-pits/incisions. Indicative relief: ~40-120 μm.
• CAT-4 (Severe): Wide-area matte/frosted fields and roughened strike zones clearly visible at standard and wide-field views; SC-2 prevalent with micro-pitting. Indicative relief: ~120-300 μm (local maxima can exceed).
• Reclassify when: If fused nodules/peppering or rust-toned dots appear → evaluate Th.01.02 grinder spark embed; if patterns are non-directional milky without catch → consider E.01.02 atmospheric matte; if linear, incised score lines dominate with chip-flank sparkle → evaluate M.01 linear scoring.
• 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. Atmospheric corrosion matte (E.01.02): Atmospheric matte is non-directional and edge/rivulet biased; eolian abrasion is directional with prevailing-wind alignment.
• vs. Residue films (R-family): Residues show wipe geometry, wetting anomalies, or odor; eolian abrasion shows grain-aligned scatter, no wipe arcs, and tactile catch at SC-1/2.
• vs. Mineral etching (Ch.03.03): Mineral etch maps drip/ring halos; eolian abrasion forms broad directional fields and edge blast unrelated to water paths.
• vs. Hot particle (Th.01): Hot particle shows discrete pits/fused nodules (pepper); eolian abrasion shows continuous frost with micro-pitting, not fused beads.

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique; raking macros of directional micro-texture, edge blast, and height gradient; façade context showing ground conditions/wind exposure. Record distance/angle in-frame.
• MSRT result (substrate): After a small reveal test patch, perform one light, non-marring pass; record SC-class (SC-1/SC-2, or SC-0 if truly film-only).
• 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.02.01 Wind-Borne Sand Abrasion - Directional frosting with edge blast on surface #___ (windward); post-reveal test patch shows [SC-1/SC-2]; visible at [12/36/72 in] under VIS geometry. Morphology: grain-aligned scatter, micro-pitting/incisions, no wipe arcs, no fused nodules. Classification: CAT-[2/3/4] by visibility and SC-class; reclassify per notes if peppering/nodules or non-directional matte is observed; CAT-5 if between-pane or coating-side loss on the surface to be worked. Forms + photo set attached; acceptance per VIS-A §6.