Plastic Part Cosmetic Defect – Black Specks | Definition, Causes & Inspection Criteria | Justway

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Plastic Part Cosmetic Defect – Black Specks | Definition, Causes & Inspection Criteria

Last updated on Jul 22, 2026

1. Definition

Black specks refer to black spots or streaks present on molded parts. Any black discoloration visible on the component surface is defined as BS (Black Specks).

2. Visual Characteristics

Typically appear as black dot-like or linear foreign inclusions

Mostly found on the part surface

Negatively impacts cosmetic uniformity

3. Potential Causes

Degraded / Burnt resin

Carbonized resin

Material stagnation residue inside barrel

Contamination from foreign debris

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Inspection Criteria

Observe color and distribution pattern

Verify whether the defect is a foreign contaminant

Distinguish between surface residue and embedded inclusions

Retain photos and defective samples

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