DSS-Ch.03.03 — Mineral Etching (subsurface micro-texture)

Mineral etching is subsurface attack of the glass network produced by persistent mineral films (e.g., hard-water salts with alkaline bias) and wet/dry cycling that chemically dissolves silica at the surface. After a proper Non-Invasive Reveal, etched areas remain as modeled micro-texture (“frost”) that modifies tone/shine and specular clarity. Classification is appearance-only per VIS (method-agnostic). Inspect under VIS lighting/geometry; record surface numbering and worked-surface status on Forms:

Footprints of former deposits/runs/edges that persist after reveal as soft-edged frosted fields; often mirrors drip trains, ring halos, pooling shelves, or sheeting paths.

In raking light the affected zone reads non-directional modeled micro-texture (not a line pattern); specular reflections appear dulled/milky.

May be patchy across exposure gradients (sprinkler throw arcs, sill zones, windward bands).

Surface-catch class (MSRT)

SC-1 (slight) to SC-2 (clear) on etched zones after reveal.

Perform one light, non-marring pass on a representative area; polymer stylus if a coating is suspected. MSRT supports classification only; do not abrade to “force” a response.

Visual signature

Modeled (non-directional) micro-texture confined to prior mineral footprints; no chip-flank sparkle (separates from mechanical scoring), no discrete fused nodules/pits (separates from hot-particle pepper).

Boundaries usually soft/feathered, occasionally ring-accented where drying fronts pinned.

Viewing / lighting

Evaluate clean & dry at 12 / 36 / 72 in, normal incidence and oblique sweep (~60°-120°); use raking light macros to resolve 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/cavity condition, classify CAT-5 by location (out of in-place scope) and refer.

Mechanism cue (context)

History of irrigation overspray, coastal aerosol + dust, HVAC plume drift, alkaline rinse/runoff, and poor maintenance enabling dwell/cycling.

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

CAT-2 (Light): Subtle modeled micro-texture, SC-1; visible primarily in raking at close/standard view; little impact at 36/72 in when clean/dry. Indicative relief: ~10-40 μm.

CAT-3 (Moderate): Clear detect (SC-2); frosted field legible at standard distance; footprint geometry evident (rings/runs/shelves). Indicative relief: ~40-120 μm.

CAT-4 (Severe): Pronounced matte/frosted regions obvious at standard & wide-field views; may appear whitened in strong raking. 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. Mineral deposits (Ch.03.01): Deposits remove fully; etched substrate remains SC-1/SC-2 with modeled micro-texture after true removal.

vs. Mineral staining (Ch.03.02): Staining shows optical veil with substrate SC-0 once truly clean; etching shows substrate SC-class > 0.

vs. Alkaline slurry etch (Ch.02.01/.02): Slurry patterns are often sheeting/splash tied to concrete work; mineral etch commonly follows sprinkler arcs/ring halos with softer boundaries.

vs. Mechanical scoring (M.01): Scoring exhibits directional lineation and chip-flank sparkle; mineral etch is non-directional modeled.

vs. Coating anomalies (Co-family): Coating rub/patchiness can mimic sheen change but lacks substrate relief; on a worked coated surface, such anomalies are not permitted at acceptance (VIS §6.2.e). Confirm coated face.

Photo set (VIS): 12 / 36 / 72 in, normal + oblique; include raking macros resolving micro-texture and boundary; add context frames showing spray lines/sills/mullions or other exposure cues. Record distance/angle in-frame.

MSRT result: One light, non-marring pass on etched field; record SC-class (SC-1/SC-2). 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; classification ≠ acceptance. Coated-face rules apply per VIS §6.2.e.

Ch.03.03 Mineral Etching - Modeled micro-texture within prior mineral footprint on surface #___ with [SC-1/SC-2]; visible at [12/36/72 in] under VIS geometry after Non-Invasive Reveal. Morphology: soft-edged frosted field (rings/runs/shelves), no chip-flank sparkle, no discrete pepper. Classification: CAT-[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 attached; acceptance per VIS-A §6.