DSS-A.02.05 — Interlayer Discoloration / Yellowing (UV/thermal aging; laminated interlayer)

A gradual color shift (amber/yellow/brown) occurring within the laminated interlayer (PVB/ionoplast, etc.) due to UV exposure, thermal load, or aging, observed between the plies. This is a laminate-internal appearance condition (not on an exposed worked face) and is generally not addressable in place; classification is location/condition-driven. Product/spec context for laminated glass is covered by ASTM C1172 and ISO 12543 (normative in VIS). Identify location using VIS surface numbering conventions; mark as laminate-internal (distinct from #1/#4 and IGU #2/#3).

• Diffuse, non-sharp yellowing or browning, often more pronounced near edges/corners or behind opaque frits/spandrels where heat buildup occurs.
• Stable to cleaning and unchanged by Non-Invasive Reveal; no face-side transition edge or chip-flank cues.
• Visibility can increase with back-lighting or oblique viewing. (Apply VIS lighting/geometry.)

Location / access (primary):

• Confirm the phenomenon is laminate-internal (between plies). On forms, record product family (laminated) and surface numbering (#1-#4; tag as laminate-internal). This is not an exposed worked face.

Surface-catch class (MSRT):

• On exposed faces, record SC-0 (none). MSRT is single, non-marring and supports classification only; do not abrade. Prefer a polymer stylus on coated faces or rely on visual/location cues.

Inspection environment / reveal controls:

• Perform Non-Invasive Reveal (clean & dry) before evaluation; persistent color shift after reveal supports internal origin. Avoid blades/abrasives/chemicals prior to classification.

Viewing / lighting:

• VIS geometry: 12 / 36 / 72 in, normal incidence + oblique sweep (~60°-120°) with raking light; add back-lit frames (when safe) to document color cast.

• CAT-5 - Out of in-place scope when discoloration resides within the laminate (not on an exposed worked surface). Document and refer per project protocol (fabricator/manufacturer/warranty).

• Not a face-relief feature. On the exposed face, MSRT records SC-0 (no surface catch). Numeric μm depth ranges apply to face-side defects only.

• vs. External films/residues (R-family): Face films respond to Non-Invasive Reveal; interlayer yellowing does not.
• vs. Edge haze/whitening (A.02.01): Whitening is a milky diffuse edge effect; discoloration is a color cast (amber/brown) without a sharp boundary. Both are laminate-internal (CAT-5 by location).
• vs. Spandrel/back-paint mottle (Co.04): Spandrel anomalies are behind the glass coating system and often show pattern/mottle; interlayer yellowing follows laminate regions and lacks paint-system pinholes/holidays. (Use product context & surface numbering.)
• vs. Low-E color non-uniformity (Co.01.02): Coating color shift occurs on a functional coating surface (face-side; acceptance rules differ). Interlayer yellowing is between plies; classify by location.

• Photo set (VIS): 12 / 36 / 72 in, normal + oblique, raking; include at least one back-lit image (when safe) to show internal color shift.
• Forms: Pane ID; product family & surface numbering (#1-#4; laminate-internal); worked surface Y/N; functional coating present on worked surface? (Y/N/Unknown); reveal status; lighting/time; geometry checklist.
• Context notes: Orientation (cardinal), presence of frit/spandrel/film behind glass, proximity to heat sources; ambient temperature/RH at time of inspection.

Attempting face-side “correction” of a laminate-internal color shift may create an unwanted worked region (visible transition edge) disallowed by VIS acceptance for CAT-0...CAT-4. Keep classification appearance-only and location-based; refer rather than abrade.

• A.02.05 Interlayer Discoloration/Yellowing (laminate-internal) - Diffuse amber/brown color shift between plies; no change after Non-Invasive Reveal; MSRT = SC-0 on exposed faces; documented at 12/36/72 in with normal + oblique under raking (incl. back-lit frame). CAT-5 (laminate-internal; out of in-place scope). Refer per project protocol.