Abstract

This document specifies procedures for determining the instrumental colour difference (CIELAB ∆E^*_Lab or ∆E₀₀) of an organic coating on a metallic substrate compared to another one used as a reference (usually called reference) and the metamerism depending on the illuminant. When two colour specimens have identical spectral reflectance curves, they are matching under any illuminant irrespective of its spectral characteristics. This is termed a "spectral match". It is also possible for two colour specimens having different spectral reflectance curves to match visually under a given light source but not to match under another light source with different spectral characteristics; such matches are termed "metameric". One quantitative description of metamerism is the so-called "metamerism index". Information on the metamerism index is of limited value where ΔE (instrumental colour difference for a given illuminant) is > 0,5. The metamerism index is not suited for determining the absolute colour difference or colour consistency of a given specimen at change of illuminant. The colour difference under the reference illuminant is to be measured in colour coordinates L*, a* and b*. Excluded from this method are organic coatings producing fluorescence and/or which are multicoloured, pearlescent or metallic. Establishing a reference as well as the magnitude of an acceptable colour difference are not covered by this method. Two methods are given in this document: a) instrumental colour difference measurement using a tristimulus colourimeter; b) instrumental colour difference measurement using a spectrophotometer or equivalent. It is advised that care is taken when measuring e.g. — textured surfaces; — fluorescent coatings; — metameric coatings; — multi-coloured, pearlescent, metallic or special colour effect coatings.

Begin

2023-05-03

WI

00139791

Planned document number

DIN EN 13523-3

Project number

00201193

Responsible national committee

NA 002-00-07 AA - General test methods for coating materials and coatings  

Responsible european committee

CEN/TC 139/WG 9 - Testing of coil coated metals  

draft standard

Coil coated metals - Test methods - Part 3: Colour difference and metamerism - Instrumental comparison; German and English version prEN 13523-3:2023
2023-08
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previous edition(s)

Coil coated metals - Test methods - Part 3: Colour difference and metamerism - Instrumental comparison; German version EN 13523-3:2021
2022-01

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