ISO 12625-15:2022

Overview

ISO 12625-15:2022 - Tissue paper and tissue products - Part 15: Determination of optical properties - Measurement of brightness and colour with C/2° (indoor daylight) illuminant - specifies instrumental test procedures for measuring the optical appearance of tissue paper under indoor daylight (C/2°) conditions. The standard covers preparation of test pieces (single‑ply and multi‑ply), required apparatus and calibration, measurement of ISO brightness and C/2° colour (CIELAB L, a, b*)**, calculation of results, and reporting requirements. This is the second edition (2022), replacing the 2015 edition.

Key Topics and Requirements

• Scope and purpose: Instrumental determination of brightness and colour as viewed in indoor daylight; distinguishes these measurements from D65/outdoor daylight methods (ISO 12625‑7).
• Instrument geometry and spectral characteristics: Use of a calibrated reflectometer or spectrophotometer meeting ISO 2469 requirements; devices must be capable of blue‑reflectance (brightness) measurement and CIE C/2° colourimetry.
• Calibration and standards:
  • Use of non‑fluorescent reference standards for photometric calibration.
  • Use of fluorescent reference standards to adjust and verify the UV content of illumination so it corresponds to CIE illuminant C.
  • Working standards (opal glass/black cavity) and routine checks.
• Preparation and conditioning: Procedures for sampling (ISO 186), conditioning samples to a standard atmosphere (ISO 187), and preparing single‑ply and multi‑ply test pieces to achieve intrinsic diffuse radiance factor (R∞) where applicable.
• Measurement procedures:
  • Measurement of ISO brightness (blue reflectance at ~457 nm with C illuminant UV content).
  • Measurement of C/2° colour expressed as L*, a*, b* using CIE 1931/2° observer and C illuminant.
• Calculation and reporting: Methods for single values, mean values, dispersion and required test report elements. Annex A provides precision information.

Applications and Who Uses It

• Manufacturers and quality control labs in tissue, toilet paper, kitchen towel and facial tissue production use ISO 12625‑15:2022 to:
  • Verify product appearance, whiteness/brightness, and colour consistency.
  • Control incoming materials (pulp, optical brighteners) and manufacturing processes (bleaching, additives, calendering).
  • Support product specifications, supplier contracts, and compliance testing.
• Instrument manufacturers, test laboratories, R&D teams, and standards bodies rely on the standard for consistent, reproducible optical property measurements.

Related Standards

• ISO 2469 - instrument geometry and diffuse radiance factor
• ISO 2470‑1 / ISO 2470‑2 - blue reflectance factor (ISO and D65 brightness)
• ISO/CIE 11664‑4 - CIELAB (Lab*)
• ISO 12625‑7 and ISO 12625‑16 - alternative optical measurement conditions
• ISO 186, ISO 187 - sampling and conditioning

Keywords: ISO 12625-15:2022, tissue paper, brightness measurement, C/2° illuminant, ISO brightness, CIELAB colour, reflectometer, spectrophotometer, optical properties.