ISO 18314-2:2023

Overview - ISO 18314-2:2023 (Analytical colorimetry)

ISO 18314-2:2023 defines procedures and calculation methods for quantitative colour measurements of pigmented layers. The standard covers the Saunderson correction for surface effects, solutions to the Kubelka–Munk equation for hiding and transparent layers, methods to calculate tinting strength (including residual colour difference) using multiple criteria, and procedures for determining hiding power. Sample preparation is intentionally excluded and is to be agreed between parties or cited from other standards.

Keywords: ISO 18314-2:2023, analytical colorimetry, Saunderson correction, Kubelka-Munk equation, tinting strength, hiding power, depth of shade, colour measurement.

Key technical topics and requirements

• Saunderson correction
  • Corrects measured reflectance for surface specular effects using Fresnel-derived coefficients.
  • Provided for common geometries (diffuse incidence/0° observation d:0° and 45°:0°).
  • Coefficients depend on binder refractive index; tabulated values and calculation tables are provided in normative annexes.
• Kubelka–Munk solutions
  • Relates absorption (K) and scattering (S) coefficients to measured reflectance for infinitely thick (hiding) and finite (transparent) layers.
  • Two solution methods are specified; Saunderson-corrected reflectances are required as input.
• Tinting strength and residual colour difference
  • Several tinting strength criteria are standardized: value of K/S at the absorption maximum, weighted K/S sum, tristimulus value Y, the smallest of X/Y/Z, and a shade depth parameter (B).
  • Procedures for calculating relative tinting strength and the residual colour difference (e.g. ΔE*) after equalizing criteria are described.
• Hiding power
  • Methods to determine the coating’s ability to obscure substrate colour are given, including practical criteria (example: contrast ratio threshold).
• Metrology
  • Guidance on repeatability and reproducibility is included; normative annexes supply coefficient tables for standard illuminants and observers (D65/10° and C/2°).

Practical applications and users

• Pigment and dye manufacturers: quantify and compare tinting strength and coverage.
• Paint, ink and coatings laboratories: evaluate hiding power, optimize formulations, and perform QC.
• Colour measurement and R&D labs: apply Saunderson corrections and Kubelka–Munk modelling for accurate spectral/colour predictions.
• Procurement, specification writers and standards bodies: use standardized metrics (relative strength, ΔE*, depth of shade) for contracts and reporting.

Related standards

• ISO 18451-1 (terminology referenced for tinting strength and depth of shade)
• Other parts of the ISO 18314 series (see ISO website for the complete list)

This standard is essential for anyone needing reproducible, internationally harmonized methods to correct surface effects, model pigment behaviour with Kubelka–Munk theory, and report tinting and hiding performance.