Overview
ISO 2470-2:2008 defines a laboratory method for measuring the D65 brightness (diffuse blue reflectance factor) of white and near-white pulps, papers and boards under outdoor daylight conditions. The standard targets materials that may contain fluorescent whitening agents (FWAs) and specifies instrument, calibration and sampling requirements so that the measured brightness reflects the fluorescent contribution under a CIE standard illuminant D65 (higher UV content than indoor illuminants).
Keywords: ISO 2470-2:2008, D65 brightness, diffuse blue reflectance factor, paper board pulps, fluorescent whitening agents.
Key Topics and Requirements
- Scope: Measurement limited to white and near‑white pulps, papers and boards, particularly fluorescent materials.
- Measurement principle: Diffuse illumination and normal detection in a calibrated reflectometer; results expressed as intrinsic radiance (reflectance) factor (R457,D65).
- Instrument: Reflectometer meeting geometric and photometric specs in ISO 2469, equipped for blue reflectance measurement (filter or diode array). Filter characteristics include an effective wavelength of 457 nm and half‑peak bandwidth of 44 nm (see Annex A).
- UV adjustment: Illumination UV content must be adjusted to match CIE standard illuminant D65 using a fluorescent reference standard (ISO 11475 procedures referenced). Abridged spectrophotometers require a UV‑adjustable filter (example cut‑off 395 nm) and calibration with fluorescent and non‑fluorescent standards.
- Calibration and standards: Use a non‑fluorescent IR3 reference for photometric calibration and a fluorescent reference standard for UV adjustment. Working standards (opal glass, ceramic, fluorescent tablets) and a controlled black cavity are required.
- Sampling & preparation: Follow ISO 186/ISO 7213 for sampling. Prepare pads of at least ten sheets (ISO 3688 for laboratory sheets) and measure top sheet sequentially.
- Expression of results: Report mean D65 brightness and standard deviation to the nearest 0.5% radiance factor (instrument precision may be ≈0.05% but UV adjustment limits resolution).
- Precision: Inter‑laboratory coefficient of variation around 1% for medium fluorescence levels.
Applications
- Quality control and acceptance testing in paper mills, converters and pulp producers.
- Product specification and supplier verification where daylight appearance and fluorescent contribution matter.
- Research and development of whitening agents, coatings and optical brighteners.
- Instrument manufacturers calibrating devices for D65 brightness measurement.
- Comparative testing for tendering and trade where outdoor/ daylight appearance is relevant.
Related Standards
ISO 2470-2:2008 is essential when you need standardized, reproducible measures of paper whiteness as perceived under daylight (D65), particularly to evaluate the effect of fluorescent whitening agents on visual brightness.