DSS-P.02.05 — Draw / Float Swirl (optical patterning)

Pane-scale optical flow patterning-subtle swirls/eddies formed by melt/float-bath flow and composition/temperature variations during manufacture. Presents as low-contrast swirl bands or gentle flow lines that bend straight reflections and modulate sheen, typically strongest at oblique angles/raking light. These are factory optical features, not local surface-relief defects. VIS treats observation under controlled lighting/geometry separately from post-restoration acceptance. For context on optical distortion measurement in heat-treated glass, VIS cites ASTM C1651 informatively.

• Swirled or meandering bands across regions of a lite; no discrete perimeter or worked boundary.
• Angle-dependent visibility-stronger in raking light and oblique sweep (~60°-120°); can diminish at normal incidence. Use VIS §5 geometry.

• Surface-catch class (MSRT): SC-0 (none). Make one light, non-marring pass per VIS §5.5; no tactile interruption because this is optical, not relief. Do not abrade or repeat.
• Visual signature: Pane-scale non-directional swirl/flow appearance; no transition edge, no chip flanks, no pits/craters. See VIS definitions for non-directional variation and directional patterning.
• Viewing/lighting: Inspect at 12 / 36 / 72 in, normal + oblique sweep, under raking light; surfaces clean/dry (non-invasive reveal).
• Location/access: Record surface numbering (#1-#4; laminate-internal) on forms; acceptance pertains to the exposed surface being evaluated.

• Not field damage. If observation confirms SC-0 with pane-scale optical flow and no local relief, record “Processing Feature - Not Surface Damage (outside CAT-1...CAT-4).” VIS keeps classification separate from acceptance; reserve CAT-5 for location/condition out of in-place scope.
• Between-pane look-alike: If fixed parallax demonstrates a cavity condition, record CAT-5 and refer per project protocol.

Not applicable as a local relief metric. Draw/float swirl is an optical (RI/flow) effect from manufacture; no micrometre-scale relief is detected by MSRT (SC-0).

• vs. Ream/Cord/Striae (P.02.04): Striae often appear as linear ribbon/streak patterns; draw/float swirl tends toward curvilinear “eddies.” Both are SC-0 and pane-scale. (Use same VIS geometry.)
• vs. Roller wave (P.01.01): Roller wave is periodic flatness deviation from heat-treat; swirls are non-periodic flow patterns from float. (Optical distortion context: ASTM C1651, informative.)
• vs. Abrasion fields (M.02): Abrasion shows directional/web texture and may escalate to slight/clear catch; swirls remain SC-0 with no worked boundary.
• vs. Coating rub/patchiness (Co.01/Co.03): Coating anomalies are localized, often tied to the worked surface and disallowed at acceptance on coated surfaces; float swirl is pane-scale and not confined by a perimeter.

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique; note raking usage; capture straight-line reflections (mullion/string) bending across the swirl field.
• MSRT result: Record SC-0; one pass only; non-marring.
• Forms: Pane ID; product family and surface numbering; worked surface Y/N; functional coating present on worked surface? (Y/N/Unknown); reveal status; lighting/time; geometry checklist.
• Acceptance split: VIS governs post-restoration appearance; factory optical features are governed by product standards/project specs-do not conflate.

Localized “spot correction” of factory swirl can create a worked region with a visible transition edge-not permitted at VIS acceptance for CAT-0...CAT-4. Keep classification appearance-only unless a true surface defect is present.

• P.02.05 Draw/Float Swirl (Processing Feature) - Pane-scale optical flow patterning observed at VIS geometry; MSRT = SC-0 (no surface relief). No transition edge or fracture morphology. Recorded as manufacturing optical feature; not categorized as surface damage under VIS-DA. If fixed parallax indicates between-pane location, record CAT-5 and refer per project protocol.