This part of EN 13523 specifies procedures for determining the instrumental colour difference (CIELAB) of an organic coating on a metallic substrate.
Establishing a standard as well as the magnitude of an acceptable colour difference are not covered by this method.
Two appropriate methods are given in this part of EN 13523:
a) instrumental colour difference measurement using a tristimulus colorimeter;
b) instrumental colour difference measurement using a spectrophotometer or equivalent.
Care shall be taken when measuring e.g.
- textured surfaces;
- fluorescent coatings;
- metameric coatings;
- multi-coloured, pearlescent, metallic or special colour effect coatings.
In order to determine whether metamerism is present, the metamerism index is determined (see EN 13523-15) and/or a visual examination (see EN 13523-22) is performed with different artificial light sources.