Paint opacity class ratings let you understand how well a paint hides the colour or surface underneath. In technical paint testing, this is measured as contrast ratio, also called hiding power.
Choosing a paint with a high opacity class can reduce the number of coats needed over dark colours, patchy plaster, lime plaster repairs or uneven base coats.
How Opacity is Tested
Under EN 13300, opacity is graded from Class 1 to Class 4. The test uses ISO 6504-3, which measures contrast ratio at a fixed spreading rate.
This means the paint is tested for how well it hides the surface it’s being applied to when applied at the stated paint coverage rate.
Opacity Classes
- Class 1 - Highest hiding power. Covers at least 99.5% of the contrast beneath it.
- Class 2 - Very good hiding power. Covers at least 98% and under 99.5% of the contrast beneath it.
- Class 3 - Moderate hiding power. Covers at least 95% and under 98% of the contrast beneath it.
- Class 4 - Lowest hiding power. Covers less than 95% of the contrast beneath it.
EU Ecolabel uses opacity as part of its performance requirements. Certified paints must meet minimum spreading rates while still achieving 98% hiding power. That means a paint must have a minimum opacity class of 2 to gain the certification.
That’s an important part of the certification because a lower impact paint should still cover properly. If poor opacity means extra coats, the job uses more paint, more packaging, more transport and creates more leftover waste, increasing its environmental impact.
