This Part of EN 13523 sepcifies procedures for determining the instrumental colour difference (CIELAB) of an organic coating on a coil coated metal.
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.
Excluded from this method are specimens producing fluorescence, showing significant metamerism, and which are multi-coloured, pearlescent or metallic.
In order to determine whether metamerism is present, the metamerism index is determined (see EN 13523-15) and/or a visual examination (see the document in preparation, WI 00139156, Part 22 of this Standard) is performed with different artificial light sources.