ISO 12625-7:2021

Overview

ISO 12625-7:2021 - Tissue paper and tissue products - Part 7: Determination of optical properties - Measurement of brightness and colour with D65/10° (outdoor daylight) - defines standardized laboratory methods for measuring the optical properties of tissue products under outdoor daylight conditions. The standard prescribes how to prepare single‑ply and multi‑ply test pieces, the required instrumentation and calibration, and the procedures to determine D65 brightness and CIELAB colour (D65/10°) values. It clarifies differences with indoor daylight measurements (C/2°) addressed in ISO 12625-15.

Key topics and technical requirements

• Scope and definitions: intrinsic diffuse radiance factor, reflectance factor, D65 brightness, tristimulus values, and CIELAB Lab* (D65/10°).
• Instrumentation: use of a reflectometer or spectrophotometer meeting ISO 2469 geometry/spectral requirements; filter or abridged spectrophotometer adjustments to achieve the D65 UV content.
• Calibration: mandatory photometric calibration with ISO 4094‑issued non‑fluorescent standards and UV adjustment using a fluorescent reference standard (per ISO 11475). Working standards (opal plates, fluorescent tablets, black cavity) are specified.
• Sampling and conditioning: sampling rules (ISO 186) and standard atmosphere for conditioning (ISO 187) to ensure reproducible results.
• Test piece preparation: instructions for single‑ply and multi‑ply pads to obtain intrinsic diffuse radiance factor R∞ where applicable.
• Measurement procedure: step‑by‑step for D65 brightness (blue reflectance factor, effective wavelength ~457 nm, half‑bandwidth 44 nm) and colour measurement (D65/10° using CIE 1964 10° observer).
• Data handling: calculation of brightness and L*, a*, b* values, reporting of means and dispersion, and required test report content.
• Precision: informative annex with repeatability and reproducibility data.

Applications and who uses it

ISO 12625-7:2021 is used for:

• Quality control and acceptance testing in tissue paper manufacturing and converting.
• Product specification and supplier compliance verification for retailers and brand owners.
• R&D and formulation work involving whitening agents, dyes, or optical brighteners.
• Independent testing laboratories and accreditation bodies to produce comparable, traceable results.
• Instrument manufacturers to ensure device compliance with D65/10° measurement conditions.

Keywords: ISO 12625-7:2021, tissue paper, optical properties, D65/10°, brightness measurement, colour measurement, reflectometer, spectrophotometer, calibration.

Related standards

• ISO 12625 series (Parts 15, 16)
• ISO 2469 (diffuse radiance factor / instrument geometry)
• ISO 11475 (CIE whiteness, D65/10°)
• ISO/CIE 11664‑4 (CIELAB)
• ISO 186 (sampling) and ISO 187 (conditioning)
• ISO 4094 (reference standards)