Supplier and customer color disputes usually expose a method mismatch: different standards, specimens, geometry, apertures, settings, conditioning or instruments. A practical quality agreement makes every one of those conditions explicit.
Define the release specimen
State whether acceptance is based on pellets, a standard let-down plaque, a production plaque, film or the finished part. Pellet data can be an incoming screen, but processing may change color, opacity, gloss and texture. Identify which specimen has authority when results disagree.
Write the measurement method
- Approved master and working-standard control.
- Geometry, SCI/SCE condition, aperture and instrument model.
- Illuminant, observer, color space and Delta E formula.
- Sample preparation, backing, thickness, orientation and conditioning.
- Number of parts, locations, readings and averaging rule.
- Calibration, verification and instrument-correlation schedule.
- Report fields, rounding and data-file format.
Establish correlation before launch
Measure a shared set of stable samples spanning the intended color range at each site. Compare instrument averages and individual color components, not only Delta E. Agree how bias will be handled and which reference instrument or laboratory resolves disputes. Recheck after service, instrument replacement or method changes.
Use layered controls
Incoming resin or masterbatch checks provide early warning. In-process plaques or first-off parts catch moulding drift. Final-part checks confirm the delivered appearance. Use trend limits inside the customer tolerance so the process can be corrected before product reaches the rejection boundary.
Define the escalation path
For a borderline or disputed lot, quarantine the material, verify instruments, remeasure retained samples under the written method, exchange spectral data and inspect together under controlled lighting. Avoid reformulating from one unexplained reading. Record concessions and corrective actions so temporary decisions do not become undocumented specifications.
Portable instruments such as the SD-500 and SD-700 UV support production and supplier workflows; the SD-800B and SD-900B suit broader laboratory methods. See writing a supplier specification, master vs working standards and the plastics hub.
Last reviewed 21/09/2026 · Level: Intermediate
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