EN 13523-3:2024

Coil coated metals - Test methods - Part 3: Colour difference and metamerism - Instrumental comparison

This document specifies procedures for determining the instrumental colour difference (CIELAB   or  ) 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.

Bandbeschichtete Metalle - Prüfverfahren - Teil 3: Farbabstand und Metamerie - Farbmetrischer Vergleich

Dieses Dokument legt Verfahren zur farbmetrischen Bestimmung des Farbabstandes (CIELAB ΔE_Lab^* oder 〖ΔE〗_00) einer organischen Beschichtung auf einem metallischen Substrat im Vergleich mit einer anderen, die als Referenz verwendet wird (üblicherweise Referenz genannt), und die Metamerie in Abhängigkeit von der Lichtart fest.
Wenn zwei Farbproben identische spektrale Reflexionskurven aufweisen, ist ihre Farbe bei jeder Lichtart unabhängig von deren spektralen Eigenschaften gleich. Dies wird „unbedingt gleich“ genannt. Es ist auch möglich, dass zwei Farbproben, die unterschiedliche spektrale Reflexionskurven aufweisen, unter einer bestimmten Lichtquelle gleich aussehen, jedoch nicht unter einer anderen Lichtquelle mit anderen spektralen Eigenschaften. Dies wird „metamer“ genannt.
Eine quantitative Beschreibung der Metamerie ist der „Metamerie-Index“.
Die Angabe des Metamerie-Index ist von begrenztem Wert, wenn ΔE (der gemessene Farbabstand für eine bestimmte Lichtart) > 0,5 ist. Der Metamerie-Index ist nicht zum Bestimmen des absoluten Farbabstands oder der Farbkonstanz einer bestimmten Probe bei Lichtartwechsel geeignet.
Der Farbabstand unter der Bezugslichtart ist durch die Farbmaßzahlen L*, a* und b* zu messen.
Von diesem Verfahren ausgeschlossen sind fluoreszierende Beschichtungen, mehrfarbige Proben, Proben mit Metallic-Beschichtungen und Proben, die Perlglanzeffekte aufweisen.
Die Festlegung einer Referenz sowie der Größenordnung eines annehmbaren Farbabstandes sind nicht Gegenstand dieses Verfahrens.
Zwei Verfahren sind in diesem Dokument angegeben:
   farbmetrische Messung des Farbabstandes mit einem Dreibereichs-Farbmessgerät;
   farbmetrische Messung des Farbabstandes mit einem Spektralphotometer oder einem gleichwertigen Gerät.
Es wird empfohlen, dass bei z. B. folgenden Messungen besonders sorgfältig gearbeitet wird:
   strukturierte Oberflächen;
   fluoreszierende Beschichtungen;
   Beschichtungen mit Metamerie;
   mehrfarbige Beschichtungen, Beschichtungen mit Perlglanzeffekt, Metallic-Beschichtungen oder Beschichtungen mit besonderem Farbeffekt.

Tôles prélaquées - Méthodes d'essai - Partie 3 : Différence de couleur et métamérisme - Comparaison au moyen d'instruments

Le présent document spécifie les modes opératoires permettant de déterminer, au moyen d’instruments, la différence de couleur (CIELAB   ou  ) d’un revêtement organique sur un subjectile métallique par rapport à un autre revêtement utilisé comme référence (généralement appelé « référence »), ainsi que le métamérisme dépendant de l’illuminant.
Lorsque deux éprouvettes de couleur ont des courbes de réflexion spectrale identiques, les couleurs correspondent quels que soient l’illuminant et ses caractéristiques spectrales ; il s’agit d’un « appariement spectral ». Il se peut aussi que deux éprouvettes de couleur n’ayant pas la même courbe de réflexion spectrale présentent la même couleur sous une source lumineuse donnée, mais pas sous une autre source lumineuse de caractéristiques spectrales différentes ; il s’agit alors d’un « appariement métamérique ».
« L’indice de métamérisme » constitue une description quantitative du métamérisme.
L’indice de métamérisme a une valeur limitée lorsque ΔE (différence de couleur mesurée par des instruments pour un illuminant donné) est > 0,5. L’indice de métamérisme ne permet pas de déterminer la différence de couleur absolue ou la constance de couleur d’une éprouvette donnée si l’illuminant change.
La différence de couleur sous l’illuminant de référence doit être mesurée en coordonnées chromatiques L*, a* et b*.
Cette méthode ne s’applique pas aux revêtements organiques fluorescents et/ou multicolores, nacrés ou métalliques.
Cette méthode n’a pas pour objet d’établir une référence ou de déterminer l’amplitude d’une différence de couleur acceptable.
Deux méthodes sont décrites dans le présent document :
a)   la mesure de la différence de couleur au moyen d’un colorimètre trichromatique ;
b)   la mesure de la différence de couleur au moyen d’un spectrophotomètre ou d’un instrument équivalent.
Il est conseillé de prendre des précautions, par exemple lors de la mesure de :
—   surfaces texturées ;
—   revêtements fluorescents ;
—   revêtements métamères ;
—   revêtements multicolores, nacrés, métalliques ou à effet de couleur spécial.

Prevlečene kovine, ki se navijajo - Preskusne metode - 3. del: Barvna razlika in metamerija - Primerjava z merilnimi instrumenti

Ta dokument določa postopke za ugotavljanje instrumentalne barvne razlike (CIELAB) organske prevleke na kovinski podlagi v primerjavi z drugo prevleko, ki se uporablja kot referenca (običajno se imenuje »referenčna prevleka«), in metamerije glede na vrsto osvetlitve.
Če imata dva barvna vzorca identični krivulji spektralnega odboja, se ujemata pod vsemi osvetlitvami, ne glede na njihove spektralne značilnosti. To je »spektralno ujemanje«. Mogoče je tudi, da se dva barvna vzorca z različnima krivuljama spektralnega odboja ujemata pod določenim virom svetlobe, ne ujemata pa se pod drugim virom svetlobe z drugačnimi spektralnimi značilnostmi; takšna ujemanja so »metamerična«.
Eden od kvantitativnih opisov metamerije je tako imenovani »metamerični indeks«.
Informacije metameričnega indeksa imajo omejeno vrednost, če je ΔE (instrumentalna barvna razlika dane osvetlitve) > 0,5. Metamerični indeks ni primeren za ugotavljanje absolutne barvne razlike ali barvne stalnosti danega vzorca ob spremembi osvetlitve.
Barvna razlika pod referenčno osvetlitvijo se izmeri v barvnih koordinatah L*, a* in b*.
Ta metoda ne zajema organskih prevlek, ki proizvajajo fluorescenco in/ali imajo večbarvni, biserni ali kovinski učinek.
Ta metoda ne zajema določitve reference ali obsega sprejemljive barvne razlike.
V tem dokumentu sta podani dve metodi:
a)   merjenje instrumentalne barvne razlike s triobmočnim kolorimetrom;
b)   merjenje instrumentalne barvne razlike s spektrofotometrom ali podobno napravo.
Svetuje se previdnost pri merjenju npr.
–   teksturiranih površin;
–   fluorescentnih prevlek;
–   metameričnih prevlek;
–   večbarvnih, bisernih ali kovinskih prevlek ali prevlek s posebnim barvnim učinkom.

General Information

• Status: Published
• Publication Date: 23-Apr-2024
• ICS: 25.220.60 - Organic coatings
• Technical Committee: CEN/TC 139 - Paints and varnishes
• Drafting Committee: CEN/TC 139/WG 9 - Testing of coil coated metals
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 24-Apr-2024
• Due Date: 06-Aug-2025
• Completion Date: 24-Apr-2024
• Ref Project: SIST EN 13523-3:2024 - Coil coated metals - Test methods - Part 3: Colour difference and metamerism - Instrumental comparison

Relations

• Replaces: EN 13523-3:2021 - Coil coated metals - Test methods - Part 3: Colour difference and metamerism - Instrumental comparison
• Effective Date: 03-May-2023

Overview

EN 13523-3:2024 is a European standard developed by CEN that specifies test methods for assessing colour difference and metamerism in coil coated metals through instrumental comparison. This standard focuses on determining the instrumental colour difference (using CIELAB or CIEDE2000 formulas) of an organic coating on metallic substrates against a reference coating. It also evaluates metamerism, which describes how colour perception varies under different illuminants.

By establishing consistent and precise methods for colour measurement, EN 13523-3:2024 supports quality control and ensures colour consistency in coil coated metal products used in various industrial and architectural applications.

Key Topics

• Instrumental Colour Difference Measurement
  Measures the colour difference ∆E between a test specimen and a reference using tristimulus colourimeters or spectrophotometers under standardized illuminants.

• Colour Coordinates (L, a, b*)**
  Utilizes the CIELAB colour space where:

  • L* indicates lightness (positive values mean lighter, negative darker than reference)
  • a* and b* refer to colour components (red/green and yellow/blue axes)
    Provides detailed understanding of shifts in hue, chroma, and lightness.

• Metamerism and Metamerism Index
  Defines "metameric" colour matches where specimens appear identical under one light source but differ under another.
  The Metamerism Index quantifies this effect but is limited to cases where the instrumental colour difference ∆E ≤ 0.5.

• Exclusions
  The method excludes organic coatings with fluorescence, multicoloured, pearlescent, or metallic finishes due to their complex colour characteristics.

• Measurement Recommendations
  Advises special care in assessing textured or embossed surfaces and coatings with special effects to ensure accurate colour difference data.

• Instrument Standards and Calibration
  Specifies requirements for using tristimulus colourimeters or spectrophotometers with defined illumination/viewing geometries (e.g., 45°:0° or integrating sphere methods) and a measurement aperture minimum of 10 mm.

Applications

• Quality Control in Coil Coated Metals
  Ensures colour uniformity and consistency in factory-applied organic coatings on metal substrates, critical for building facades, appliances, automotive parts, and consumer products.

• Comparative Colour Analysis
  Facilitates precise and reproducible comparison between production batches or against predefined references to maintain desired aesthetic characteristics.

• Metamerism Assessment
  Evaluates the behaviour of coated metal surfaces under different lighting environments - vital for industries where lighting conditions vary, ensuring end-user satisfaction.

• Material Development and Approval
  Supports R&D and supplier approval processes by providing standardized test methods to assess colour matches and discrepancies objectively.

Related Standards

• EN 13523-0:2021 – General introduction to coil coated metals test methods.
• EN ISO/CIE 11664-4 (CIE 1976 Lab* colour space) – Defines the colour coordinate system used for the assessments.
• EN ISO/CIE 11664-6 (CIEDE2000 colour-difference formula) – Specifies the advanced colour difference calculation method included in the latest standard.
• EN 23270 – Specifies conditioning environments for paint and varnish testing.

Summary

EN 13523-3:2024 provides a vital framework for evaluating colour differences and metamerism in coil coated metals using instrumental techniques. By applying this standard, manufacturers and quality controllers can achieve consistent and reproducible colour assessments, mitigating issues arising from visual mismatches caused by different lighting conditions.

This standard is indispensable for industries requiring high precision in colour appearance and durability of metallic coated products, ensuring enhanced customer satisfaction and compliance with international quality standards.

Keywords: coil coated metals, colour difference measurement, instrumental comparison, metamerism index, CIELAB, CIEDE2000, spectrophotometer, colour consistency, organic coatings, textured coatings, colour quality control, European standard EN 13523-3, colour testing in metals.

Standards Content (Sample)

SLOVENSKI STANDARD
01-september-2024
Nadomešča:
SIST EN 13523-3:2021
Prevlečene kovine, ki se navijajo - Preskusne metode - 3. del: Barvna razlika in
metamerija - Primerjava z merilnimi instrumenti
Coil coated metals - Test methods - Part 3: Colour difference and metamerism -
Instrumental comparison
Bandbeschichtete Metalle - Prüfverfahren - Teil 3: Farbabstand und Metamerie -
Farbmetrischer Vergleich
Tôles prélaquées - Méthodes d'essai - Partie 3 : Différence de couleur et métamérisme -
Comparaison au moyen d'instruments
Ta slovenski standard je istoveten z: EN 13523-3:2024
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
25.220.60 Organske prevleke Organic coatings
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 13523-3
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2024
EUROPÄISCHE NORM
ICS 25.220.60 Supersedes EN 13523-3:2021
English Version
Coil coated metals - Test methods - Part 3: Colour
difference and metamerism - Instrumental comparison
Tôles prélaquées - Méthodes d'essai - Partie 3 : Bandbeschichtete Metalle - Prüfverfahren - Teil 3:
Différence de couleur et métamérisme - Comparaison Farbabstand und Metamerie - Farbmetrischer
au moyen d'instruments Vergleich
This European Standard was approved by CEN on 1 January 2024.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13523-3:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Principle . 6
4.1 Colour coordinates . 6
4.2 Metamerism index . 7
5 Apparatus . 7
6 Sampling . 7
7 Test specimens . 7
8 Procedure . 7
8.1 Calibration . 7
8.2 Measurement . 7
9 Expression of results . 8
10 Accuracy . 9
11 Test report . 10
Bibliography . 11

European foreword
This document (EN 13523-3:2024) has been prepared by Technical Committee CEN/TC 139 “Paints and
varnishes”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2024, and conflicting national standards shall
be withdrawn at the latest by October 2024.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 13523-3:2021.
a) calculating colour differences according to the CIEDE2000 formula has been added;
b) the text has been editorially revised and the normative references have been updated.
The EN 13523 series, Coil coated metals — Test methods, consists of the following parts:
— Part 0: General introduction
— Part 1: Film thickness
— Part 2: Gloss
— Part 3: Colour difference and metamerism — Instrumental comparison
— Part 4: Pencil hardness
— Part 5: Resistance to rapid deformation (impact test)
— Part 6: Adhesion after indentation (cupping test)
— Part 7: Resistance to cracking on bending (T-bend test)
— Part 8: Resistance to salt spray (fog)
— Part 9: Resistance to water immersion
— Part 10: Resistance to fluorescent UV radiation and water condensation
— Part 11: Resistance to solvents (rubbing test)
— Part 12: Resistance to scratching
— Part 13: Resistance to accelerated ageing by the use of heat
— Part 14: Chalking (Helmen method)
— Part 16: Resistance to abrasion
— Part 17: Adhesion of strippable films
— Part 18: Resistance to staining
— Part 19: Panel design and method of atmospheric exposure testing
— Part 20: Foam adhesion
— Part 21: Evaluation of outdoor exposed panels
— Part 22: Colour difference — Visual comparison
— Part 23: Resistance to humid atmospheres containing sulfur dioxide
— Part 24: Resistance to blocking and pressure marking
— Part 25: Resistance to humidity
— Part 26: Resistance to condensation of water
— Part 27: Resistance to humid poultice (Cataplasm test)
— Part 29: Resistance to environmental soiling (Dirt pick-up and striping)
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
1 Scope
*
This document specifies procedures for determining the instrumental colour difference (CIELAB ∆E
Lab
or ∆E ) 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;
— m
...