The BGD 582-S Opacity Meter is our latest-generation instrument for measuring the hiding power of paints. It uses a 45°/0° optical geometry (45° annular uniform illumination, 0° reception) and complies with ISO 6504-3 and ASTM D2805, among other standards. The instrument measures the reflectance of a coating applied over black and white substrates and automatically calculates the contrast ratio (C = Rb/Rw) of the sample.
Why Opacity Matters
Opacity, or hiding power, is one of the most important properties of a paint. It determines how well a coating covers the colour and pattern of the substrate underneath. A paint with good hiding power achieves a uniform appearance in fewer coats, which saves material, labour and time on the job.
For paint manufacturers, opacity is a key quality and cost parameter. Titanium dioxide and other hiding pigments are among the most expensive raw materials in a formulation. Accurate measurement of hiding power helps formulators find the right balance between performance and cost, verify batch-to-batch consistency and support the coverage claims on the label, for example in m² per litre.
Visual assessment of opacity is subjective and difficult to reproduce. Instrumental measurement of the reflectance over black and white substrates gives objective, traceable figures that can be compared between laboratories, suppliers and customers, in line with international standards such as ISO 6504-3 and ASTM D2805.
Standards
EN ISO 2814: Paints and varnishes – Comparison of contrast ratio (hiding power) of paints of the same type and colour
ISO 6504-3:2019: Paints and varnishes – Determination of hiding power – Part 3: Determination of hiding power of paints for masonry, concrete and interior use
ASTM D2805-11(2023): Standard Test Method for Hiding Power of Paints by Reflectometry
ASTM E97: Standard Test Method for Directional Reflectance Factor, 45-deg 0-deg, of Opaque Specimens by Broad-Band Filter Reflectometry (withdrawn 1991)
DIN 55984: Testing of pigments – Determination of a hiding power value of white and light grey media (Prüfung von Pigmenten; Bestimmung eines Deckvermögenswertes von weißen und hellgrauen Medien) (withdrawn)
BS 3900-D6: Methods of test for paints – Optical tests on paint films – Determination of contrast ratio (opacity) of light-coloured paints at a fixed spreading rate, using polyester film
BS 3900-D7: Methods of test for paints – Optical tests on paint films – Determination of hiding power of white and light-coloured paints by the Kubelka-Munk method (superseded by BS EN ISO 6504-1)
