Color Testing for Materials: Measurement Methods, Standards & Instrumentation
Color is one of the most immediately perceived quality attributes of any manufactured product. A paint that shifts from its approved shade, a plastic housing that doesn’t match its reference standard, or a textile that fades inconsistently across a production run — all represent quality failures that erode consumer confidence and generate costly returns. Systematic color testing provides the objective, instrument-based measurements needed to control color quality throughout product development and manufacturing in the coatings, textiles & plastics industry.
The Science of Color Measurement
Human color perception involves three factors — the light source, the object, and the observer — collectively captured in the CIE (Commission Internationale de l’Éclairage) colorimetric framework. The CIE 1976 Lab* (CIELAB) color space is the international standard for expressing color numerically:
- L* — lightness (0 = black, 100 = white)
- a* — red-green axis (positive = red, negative = green)
- b* — yellow-blue axis (positive = yellow, negative = blue)
Color difference (ΔE*) between two specimens is calculated as:
ΔE = √(ΔL² + Δa² + Δb²)**
ΔE* values below 1.0 are generally imperceptible to the human eye under normal viewing conditions; values above 2.0–3.0 represent visible differences that may be commercially unacceptable depending on application.
Instruments for Color Measurement
Spectrophotometers
Spectrophotometers measure the spectral reflectance or transmittance of a sample across the visible wavelength range (typically 360–780nm) at defined wavelength intervals (1nm or 10nm). From the spectral data, colorimetric values (L*, a*, b*, C*, h°) are calculated for any combination of standard illuminant (D65, A, F2) and observer (2° or 10°) functions. Spectrophotometers are the gold standard for color measurement — providing complete spectral information that enables metamerism analysis and virtual color matching.
Colorimeters
Colorimeters measure color using three broadband filtered detectors that approximate the CIE observer functions. They are faster and less expensive than spectrophotometers but provide less information — colorimetric values only, without spectral data. Colorimeters are suitable for production quality control where speed is valued and metamerism risk is low.
Geometry: d/8°, 45°/0°, and Sphere Instruments
Measurement geometry profoundly affects results for textured, metallic, or directional surfaces. The sphere (d/8°) geometry measures color excluding or including specular reflection (SCE vs. SCI modes) and is preferred for matte and textured surfaces. The 45°/0° geometry excludes specular reflection by design and correlates well with human visual assessment of appearance.
Key Color Testing Standards
ASTM D2244 — Color Difference from Instrumental Measurements
ASTM D2244 provides the calculation procedures for expressing color differences between specimens using CIE Lab* and other color difference formulas. It is the primary reference for color tolerance and acceptance criteria across the coatings, textiles & plastics industry.
AATCC 173 — CMC: Calculation of Small Color Differences for Acceptability
The CMC (l:c) color difference formula — standardized in AATCC 173 — is widely used in the textiles industry because it better correlates with visual acceptability than ΔE*ab for small color differences, particularly for saturated or complex hues.
ISO 7724 — Paints and Varnishes: Colorimetry
ISO 7724 (Parts 1–3) specifies instrument requirements, measurement procedures, and calculation methods for colorimetric assessment of paints and coatings — the primary reference for automotive and industrial coatings color quality.
ASTM D1535 — Specifying Color by the Munsell System
The Munsell color system (Hue, Value, Chroma) provides a perceptually uniform color ordering system used for visual color specification and sorting of ceramic glazes, natural materials, and architectural coatings.
Colorfastness Testing
Color retention during use — colorfastness — is a critical quality attribute for materials exposed to light, washing, rubbing, perspiration, and other degrading influences. Key colorfastness tests include:
- AATCC 16 / ISO 105-B02 — Colorfastness to light (xenon arc)
- AATCC 61 / ISO 105-C06 — Colorfastness to laundering
- AATCC 8 / ISO 105-X12 — Colorfastness to crocking (dry and wet rubbing)
- ASTM D4459 — Colorfastness to indoor light for plastics
- SAE J2412 / J2527 — Automotive interior and exterior light exposure
Conclusion
Color testing of materials is a critical quality assurance function that ensures visual consistency, product performance, and regulatory compliance across industries such as automotive, textiles, coatings, and pharmaceuticals. Using standardized instruments like spectrophotometers and colorimeters alongside established systems such as CIE L*a*b* and standards from ASTM, ISO, and SAE, manufacturers can objectively quantify and control color across production batches and supply chains. When integrated into quality management systems, color testing reduces rework, prevents costly rejections, and maintains brand consistency—making it a functional requirement, not merely a cosmetic
Why Choose Infinita Lab for Color Testing of Materials?
Infinita Lab’s color testing laboratory provides spectrophotometric color measurement, ΔE* difference analysis per ASTM D2244, colorfastness testing (AATCC 16, AATCC 61, AATCC 8, ISO 105 series), and multi-angle color characterization for metallic and effect surfaces — supporting quality programs across the coatings, textiles & plastics industry. Our color measurement specialists combine calibrated instrumentation with expert knowledge of color science and industry standards to deliver precise, reproducible color quality data. Visit infinitalab.com to discuss your color testing requirements with Infinita Lab’s team.
Frequently Asked Questions
What is the difference between a colorimeter and a spectrophotometer? A colorimeter measures color using fixed filters and provides L*a*b* or RGB values—suitable for pass/fail quality checks. A spectrophotometer measures the full reflectance spectrum across wavelengths and offers more detailed, accurate data suitable for formulation, research, and standard-compliant testing.
What is the CIE L*a*b* color space and why is it used? CIE L*a*b* is a device-independent color model where L* represents lightness, a* represents the red-green axis, and b* represents the yellow-blue axis. It is widely used because it approximates human visual perception and allows precise, numerical comparison of color differences (ΔE).
What is metamerism and why does it matter in color testing? Metamerism occurs when two samples appear to match under one light source but differ under another. It is particularly relevant in automotive interiors, fashion, and paint matching. Testing under multiple illuminants helps detect and control this phenomenon.
Can color testing detect coating thickness or surface defects? Standard colorimetry does not measure coating thickness directly. However, color variation across a surface can indicate inconsistent coating application, pigment migration, or surface defects—making it a useful indirect screening tool.
What is ΔE and what value is considered acceptable? ΔE (Delta E) quantifies the total color difference between two samples. A ΔE below 1.0 is generally imperceptible to the human eye; values between 1–2 are acceptable for most industrial applications; above 3–5 is typically considered a visible, commercially unacceptable deviation.
