What is ISO 6504‑1 - Paints and varnishes about ?
ISO 6504‑1 is an international standard on paints and varnishes which covers the determination of hiding power with the Kubelka-Munk method for white and light-coloured paints.
ISO 6504‑1 specifies a method for determining the hiding power (spreading rate necessary to give a hiding power of 98 %) of white or light-coloured paints. It is applicable to paint films having the tristimulus value of Y ≥ 70 and hiding power > 80 %. It is not applicable to fluorescent or metallic paints.
Who is ISO 6504‑1 - Paints and varnishes for ?
ISO 6504‑1 on paints and varnishes is useful for: 
- Paints and varnishes manufacturers
Why should you use ISO 6504‑1 - Paints and varnishes ?
Hiding power of paints is generally defined as the spreading rate required to give a hiding power of 98 %. To determine this by the method specified in ISO 6504-3 would be time-consuming and require considerable extrapolation which often exceeds the limit of linearity of the relationship between hiding power and spreading rate. Therefore, this method for the determination of hiding power, involving the Kubelka-Munk (K-M) equations which relate scattering and absorption coefficients to optical properties, has also been standardized.
ISO 6504-3 specifies a method for determining the hiding power of paints at a fixed spreading rate, by applying paint films to black and white charts and to polyester film respectively. It depends on the observation that there is a linear relationship between hiding power and reciprocal film thickness, at least over a limited range of film thickness.
Where ISO 6504‑1 sets itself apart is that it can provide a spreading rate necessary to give a hiding power of 98 % with relative ease as the Kubelka-Munk (K-M) equations method which relates to scattering and absorption coefficients to optical properties has been standardized.
What’s changed since the last update ?
BS EN ISO 6504‑1:2019 supersedes BS EN ISO 6504‑1:2006 (dual numbered as BS 3900-D7:1983), which is withdrawn.
BS EN ISO 6504‑1:2019 includes some technical changes with respect to BS EN ISO 6504‑1:2006. These are:
- The normative references in Clause 2 have been updated
- Clause 3 for terms and definitions has been added
- Clause 7 for limitations has been added
- The term "contrast ratio" has been changed to "hiding power" throughout the text
- It has been clarified that the reflectance Rg needs to be measured and that the graphs in Annex A and values in Table B.1 are only examples for Rg = 0,80
