What is ISO 6504‑3 - Paints and varnishes about?
ISO 6504‑3 is part 3 of a multi-series of international standards on paints and varnishes which covers the determination of hiding power of paints for masonry, concrete and interior use.
ISO 6504‑3 specifies methods for determining the hiding power given by paint coats of white or light colours of tristimulus values Y and Y10 greater than 25, applied to a black and white chart, or to a colourless transparent foil. In the latter case the tristimulus values Y and Y10 are measured over black and white panels. Subsequently, the hiding power is calculated from these tristimulus values.
ISO 6504‑3 also specifies a simple method for calculating the spreading rate for paints with a volatile matter content with low evaporation speed, e.g. coatings for interior walls and ceilings as specified in EN 13300.
Who is ISO 6504‑3 - Paints and varnishes for?
ISO 6504‑3 on paints and varnishes is useful for: 
- Paints and varnishes manufacturers
Why should you use ISO 6504‑3 - Paints and varnishes?
Two techniques are available for substrate preparation and measurement when determining the hiding power of paints for masonry and concrete:
- Application to colourless, transparent foil, the coated foil being subsequently placed in turn over black and white panels
- Direct application to black and white charts
The spreading rate is important for the determination of the hiding power ratio. The spreading rate can be either determined according to ISO 3233-3 or according to another simplified method described in the standards applicable to coating materials for interior walls and ceilings as specified in EN 13300.
The methods are based on the observation that hiding power is an approximately linear function of reciprocal spreading rate, over a restricted coating thickness range which also corresponds to that used for normal application of white or light-coloured paints. It is thus possible to interpolate graphically or by computation, with satisfactory accuracy, between results obtained with coatings of different thicknesses.
What’s changed since the last update?
BS EN ISO 6504‑3:2019 supersedes BS EN ISO 6504‑3:2007, which is withdrawn.
BS EN ISO 6504‑3:2019 includes some technical changes with respect to BS EN ISO 6504‑3:2007. These are:
- A definition for light-coloured paint has been added
- A new method (method C), which is suitable for waterborne coating materials only, has been introduced
- The determination of the mass per unit area of the dry coating and the determination of the practical spreading rate have been deleted (ISO 3233-3 can be used instead)
- The reference to a fixed spreading rate has been deleted from the foreword, scope and test report (it had already been deleted from the procedure in the previous edition)
- The historic precision values for methods A and B have been deleted from the normative part and information on a new
