DSS-P.02.04 — Ream / Cord / Striae (optical inhomogeneity)

Ream/cord/striae are optical inhomogeneities in float glass arising from localized variations in composition/temperature during forming. They present as streaks, swirls, or ribbons that deflect straight-line reflections and alter transmitted/reflected imagery, most apparent at oblique angles. These are factory optical features rather than local surface-relief defects. VIS treats observation under controlled lighting/geometry separately from post-restoration acceptance; measurement background for heat-treated optical distortion phenomena is cited in VIS as ASTM C1651 (informative).

• Pane-scale streaks or swirls (sometimes gently undulating), visible as bending of straight reflections or faint flow patterns; not bounded by a local “worked” edge.
• Varies with incidence and polarization; reads strongest under raking light with an oblique sweep and may reduce at normal incidence. (Use VIS geometry.)

Surface-catch class (MSRT):

SC-0 (none). Perform one light, non-marring pass per VIS §5.5 to confirm absence of tactile relief; do not abrade or repeat passes. The MSRT is used only to support classification, not acceptance.

Visual signature:

Non-localized optical deflection (straight lines appear bent) or swirled streaks with no transition edge, no chip flanks, and no pits/craters typical of surface damage.

Viewing/lighting:

Evaluate at 12 / 36 / 72 in with normal incidence and oblique sweep (~60°-120°) under raking light; surfaces clean and dry per VIS.

Location/access:

Use surface numbering (#1-#4; laminate-internal) on forms when IGUs/laminates are present.

• Not field damage. When observation confirms SC-0 with pane-scale optical inhomogeneity and no local relief, record: “Processing Feature - Not Surface Damage (outside CAT-1...CAT-4).” VIS separates classification from acceptance and reserves CAT-5 for location/condition out of in-place scope.
• If a similar appearance is confirmed between panes (fixed parallax in an IGU) or otherwise inaccessible, record CAT-5 and refer per project protocol.

Not applicable as a local relief metric. Ream/cord/striae are optical (refractive index/flow) effects from manufacture; no micrometre-scale relief is detected by MSRT (SC-0).

• vs. Roller wave (P.01.01): Roller wave is periodic flatness deviation from heat-treat; ream/cord are flow-pattern streaks/swirls from float-both are SC-0 optical/shape phenomena; see VIS’s C1651 reference for optical distortion context.
• vs. Abrasion fields (M.02): Abrasion shows directional patterning and can escalate to slight/clear catch; ream/cord remain SC-0 with no transition edge.
• vs. Coating rub/patchiness (Co.01/Co.03): Coating anomalies tend to be localized with possible worked boundaries and are disallowed on the worked surface at acceptance; ream/cord are pane-scale and not confined by a perimeter.

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique; include raking usage; capture a straight-line reflection (mullion/string line) to show optical bending.
• MSRT result: Record SC-0 (none); 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 acceptance; factory optical features are governed by product standards/project specs; do not conflate.

Attempting localized “spot-work” to “correct” factory optical streaks can introduce a worked region with a visible transition edge, which VIS disallows at acceptance for CAT-0...CAT-4. Keep classification appearance-only for these features

• P.02.04 Ream/Cord/Striae (Processing Feature) - Pane-scale optical inhomogeneity (streak/swirls) 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.