Overview
ISO 2470-1:2016 specifies a standardized method to measure the diffuse blue reflectance factor (commonly called ISO brightness) of white and near‑white pulps, papers and boards under indoor daylight conditions. The measurement is made with a calibrated reflectometer whose ultraviolet (UV) content is adjusted to correspond to CIE illuminant C using a fluorescent reference standard. ISO brightness is reported as a percentage (intrinsic diffuse reflectance factor) and is intended for quality control and specification of paper optical properties.
Key topics and technical requirements
- Property measured: Diffuse blue reflectance factor (ISO brightness) - the intrinsic diffuse radiance/reflectance measured under specified spectral and geometric conditions.
- Instrumentation:
- Reflectometer conforming to ISO 2469 (geometric, spectral and photometric characteristics).
- For filter instruments: UV content of illumination must match CIE illuminant C.
- For abridged spectrophotometers: adjustable UV‑cutoff (e.g., ~395 nm) or equivalent UV‑control system; measurement weighting corresponds to a 457 nm effective wavelength with a 44 nm half‑bandwidth (see Annex A).
- Reference standards & calibration:
- Use non‑fluorescent and fluorescent international reference standards (IR3) for photometric calibration and UV adjustment (Annex B).
- Working standards: opal glass plates, fluorescent tablets, and a calibrated black cavity.
- Sampling and sample preparation:
- Paper/board sampling per ISO 186; pulp sampling per ISO 7213.
- Laboratory sheets for pulps per ISO 3688.
- Conditioning recommended by ISO 187, but avoid high preconditioning temperatures that alter optics.
- Procedure & reporting:
- Measure at least ten test pieces assembled as a pad; record mean intrinsic diffuse reflectance and standard deviation to the nearest 0.05% (or better).
- Limitations:
- Applies only to white and near‑white materials and to instruments adjusted to CIE illuminant C.
- D65 (outdoor daylight) brightness is covered in ISO 2470‑2.
Applications and users
ISO 2470-1 is used for:
- Quality control and incoming/outgoing inspection by paper and board manufacturers.
- Specification and acceptance testing by paper merchants, converters and print houses.
- R&D and formulation work for pulp producers and suppliers of fluorescent whitening agents.
- Independent testing laboratories and certification bodies reporting reproducible ISO brightness values.
Practical uses include product specification, process control, benchmarking bleaching/whitening performance, and assessing the optical contribution of fluorescent whiteners.
Related standards
Keywords: ISO 2470-1:2016, ISO brightness, paper brightness measurement, diffuse blue reflectance factor, CIE illuminant C, reflectometer calibration, fluorescent reference standard, pulp paper board testing.
Open preview (PDF)Paper, board and pulps — Measurement of diffuse blue reflectance factor — Part 1: Indoor daylight conditions (ISO brightness)