A glossy plastic surface produces a strong specular reflection. Small changes in mould polish, flow, contamination, scratches or measurement angle can shift the reading even when the bulk color is unchanged. The method must state how the specular component is handled.
SCI and SCE answer different questions
SCI includes the specular component and reduces sensitivity to surface-gloss differences, making it useful for monitoring material color. SCE excludes the specular component and is more sensitive to the appearance effect of gloss. Use one defined condition for standards and samples; never compare SCI data with SCE data.
Prepare without changing the surface
- Handle by edges and remove loose dust with the agreed method.
- Do not polish a production sample to remove marks.
- Control orientation on directional films, flow lines or brushed effects.
- Use a fixture so curved parts contact the port consistently.
- Reject readings where the aperture includes an edge, gate or damaged area.
Measure gloss separately when required
A color spectrophotometer is not automatically a glossmeter. If gloss affects acceptance, specify a separate gloss value and geometry suited to the plastic. ASTM D2457 covers specular gloss of plastic films and solid plastics and includes different measurement angles for different gloss ranges. Apply the customer’s nominated method and current standard edition.
Diagnose a mismatch
If SCI passes but SCE or the visual assessment fails, investigate surface replication, mould condition and gloss before changing pigment. If both SCI and SCE move in the same color direction, material formulation or processing is more likely involved. Retain Delta L*, Delta a* and Delta b*, not only total Delta E.
Portable SCI/SCE options include the SD-500 and SD-700 UV. Continue with textured plastics, SCI vs SCE and the complete plastics guide.
Last reviewed 21/09/2026 · Level: Intermediate
Topics
Applications
Related knowledge
Fundamentals
Color Measurement in Plastics: Complete Guide
A complete framework for specifying, measuring and controlling plastic color across raw material, moulding, extrusion and supplier quality workflows.
Technical guide · Read the guide →Measurement Techniques
Gloss and Color Measurement: Why Surface Finish Changes Results
Surface finish can change color readings and visual acceptance. Define the measurement condition, then control color and gloss as separate requirements where needed.
Quick technical guide · Read the guide →SCI & SCE
SCI vs SCE Explained: Specular Included and Excluded
SCI includes specular reflection and generally reduces finish-related color variation; SCE excludes it and is more sensitive to finish.
6 minute guide · Read the guide →45/0 Geometry
d/8° vs 45°/0° Geometry: Choosing the Right Color Measurement
Color is shaped by the way light reaches a surface and the angle from which it is viewed. Measurement geometry defines those conditions for a spectrophotometer, making it…
8 min guide · Read the guide →Measurement Techniques
How Sample Preparation Affects Color Measurement
Sample preparation is part of the measurement method. Control the presentation, orientation, backing and condition that represent the approved product.
Quick technical guide · Read the guide →Measurement Techniques
How to Measure Color on Plastics
Start plastic color measurement by choosing reflectance or transmission. Backing, thickness and orientation then become controlled method conditions.
Quick technical guide · Read the guide →