prEN 646

• Abstract:

  This document describes procedures for the testing of dyed paper and board intended to come into contact with foodstuffs. Some procedures depending on the foreseeable use of the material are given.; Visual evaluation against a grey scale provides grading of the bleeding.; For samples having significant different sides, a migration can occur from one glass fibre to the other and could lead to wrong interpretation of the fastness of one side. It is advisable to check these samples using large sampling procedure to prevent cross contamination of the glass fibre during the migration procedure. The procedure is described in Annex A. If lower limit of detection is required, this procedure could also be used.

• Status: Not Published
• Publication Date: 11-Jan-2028
• ICS: 67.250 - Materials and articles in contact with foodstuffs
• ICS: 85.060 - Paper and board
• Technical Committee: CEN/TC 172 - Pulp, paper and board
• Drafting Committee: CEN/TC 172/WG 3 - Analytical methods for the assessment of paper and board in contact with foodstuffs
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 06-Aug-2026
• Due Date: 18-Nov-2026
• Completion Date: 06-Aug-2026
• Ref Project: oSIST prEN 646:2026 - Paper and board intended to come into contact with foodstuffs - Determination of colour fastness of dyed paper and board

• Revises: EN 646:2018 - Paper and board intended to come into contact with foodstuffs - Determination of colour fastness of dyed paper and board
• Effective Date: 08-Oct-2025

Overview

prEN 646:2026, titled Paper and board intended to come into contact with foodstuffs - Determination of colour fastness of dyed paper and board, is a draft European standard developed by CEN. This standard specifies test procedures for assessing the colour fastness (or bleeding) of dyed paper and board intended for use with foodstuffs. Visual evaluation against a grey scale is used to determine the extent of dye migration under conditions simulating various types of food contact. This is critical for ensuring the safety and quality of food packaging, as unwanted dye transfer can pose health risks or affect food integrity.

Key Topics

• Scope of Testing: prEN 646 covers dyed paper and board materials that are intended to have direct contact with food. The standard addresses different foreseeable use scenarios, offering customized test procedures to reflect real-life conditions.

• Test Principle: The test involves placing the sample in contact with glass fibre papers saturated with test fluids, then applying specified pressure and temperature. The degree of colour transfer (bleeding) is evaluated visually using a recognized grey scale.

• Evaluation Criteria: Results are graded by comparing the stained glass fibre paper against the grey scale for staining (as per EN ISO 105-A03).

• Sample Variability: For papers or boards that differ significantly on either side, the risk of cross-contamination is considered. The standard provides a large sampling procedure (detailed in Annex A) to minimize misinterpretation and improve accuracy.

• Test Fluids and Conditions: Test fluids include distilled or deionised water, diluted acetic acid, alkaline salt solution, and specific vegetable oils. Test conditions reflect different durations and temperatures relevant to possible food contact scenarios (short-term, long-term, hot contact).

• Reporting and Precision: The standard outlines strict reporting requirements, ensuring transparency and reproducibility across laboratories. Annex B provides precision data compiled from interlaboratory studies.

Applications

prEN 646 is a critical reference for:

• Food Packaging Manufacturers: Ensuring that coloured papers and boards used for direct food contact do not release dyes into food under expected conditions.
• Quality Assurance and Compliance: Providing a reliable method for demonstrating compliance with European food safety regulations, including those referenced by EU Regulation No 10/2011.
• Testing Laboratories: Standardizing test methods to achieve consistent and internationally recognized results across routine quality control, product development, and batch release.
• Regulatory Authorities: Offering a benchmark for market surveillance, approval, and control of food contact materials, particularly for packaging containing dyes or coloured layers.

The standard supports safe market placement of food packaging components, reduces risk of contamination, and underpins customer confidence in packaging safety.

Related Standards

Organizations and professionals working with prEN 646 should also consider the following standards:

• EN ISO 105-A03 - Textiles - Tests for colour fastness - Part A03: Grey scale for assessing staining
• EN ISO 186 - Paper and board - Sampling to determine average quality
• EN ISO 3696 - Water for analytical laboratory use - Specification and test methods
• EN ISO 4787 - Laboratory glass and plastic ware - Volumetric instruments - Methods for testing of capacity and for use
• ISO 6588-2 - Paper, board and pulps - Determination of pH of aqueous extracts - Part 2: Hot extraction
• Commission Regulation (EU) No 10/2011 - On plastic materials and articles intended to come into contact with food

By aligning with these standards, industry stakeholders can ensure robust, harmonized approaches to the safety and quality of paper and board food contact materials.

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Keywords: prEN 646, colour fastness, dyed paper, board, food contact materials, food packaging, dye migration, grey scale assessment, CEN standard, food safety.

SLOVENSKI STANDARD
01-julij-2026
Papir, karton in lepenka, namenjeni za stik z živili - Ugotavljanje obstojnosti barve
v obarvanem papirju, kartonu in lepenki
Paper and board intended to come into contact with foodstuffs - Determination of colour
fastness of dyed paper and board
Papier und Pappe vorgesehen für den Kontakt mit Lebensmitteln - Bestimmung der
Farbechtheit von gefärbtem Papier und Pappe
Papiers et cartons destinés à entrer en contact avec les denrées alimentaires -
Détermination de la solidité de la couleur des papiers et cartons colorés
Ta slovenski standard je istoveten z: prEN 646
ICS:
67.250 Materiali in predmeti v stiku z Materials and articles in
živili contact with foodstuffs
85.060 Papir, karton in lepenka Paper and board
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2026
ICS 67.250; 85.060 Will supersede EN 646:2018
English Version
Paper and board intended to come into contact with
foodstuffs - Determination of colour fastness of dyed paper
and board
Papiers et cartons destinés à entrer en contact avec les Papier und Pappe vorgesehen für den Kontakt mit
denrées alimentaires - Détermination de la solidité de Lebensmitteln - Bestimmung der Farbechtheit von
la couleur des papiers et cartons colorés gefärbtem Papier und Pappe
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 172.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 646:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Principle . 4
5 Materials and equipment . 5
5.1 General. 5
5.2 Unstained glass fibre papers of 60 mm × 90 mm . 5
5.3 Glass plates, 60 mm × 90 mm. . 5
5.4 Polyethylene film, uncoloured and transparent. . 5
5.5 Weight, having a mass of 1 kg. . 5
5.6 Grey scale . 5
5.7 Drying cupboard . 5
5.8 Kettle . 5
5.9 Cotton gloves . 5
5.10 Adjacent glass rods . 5
6 Reagents . 5
6.1 Distilled or deionised water . 5
6.2 Aqueous acetic acid, 3,0 % (m/V). . 5
6.3 Alkaline salt solution, see Table 1, composition of the alkaline salt with a pH value of
8,6 ± 0,1. . 5
6.4 Castor oil or sunflower oil, with specification of vegetable oil that should be as defined in
Regulation (EU) No 10/2011 [1]. . 6
7 Sampling . 6
8 Preparation of test pieces . 6
9 Procedure . 6
10 Test conditions . 7
11 Evaluation . 7
12 Test Report . 8
Annex A (normative) Determination of colour fastness of dyed paper and board on large samples
............................................................................................................................................................................... 9
Annex B (informative) Precision data . 10
Bibliography . 13
European foreword
This document (prEN 646:2026) has been prepared by Technical Committee CEN/TC 172 “Pulp, paper
and board”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 646:2018.
This document includes the following significant technical changes with respect to EN 646:2018:
a) Update of materials and equipment (Clause 5);
b) modification of the type of oil which can be used (6.4);
c) precision in evaluating the staining (Clause 11);
d) addition of an Annex on precision data (Annex B);
e) revision of Annex A;
f) editorial changes.
1 Scope
This document describes procedures for the testing of dyed paper and board intended to come into
contact with foodstuffs. Some procedures depending on the foreseeable use of the material are given.
Visual evaluation against a grey scale provides grading of the bleeding.
For samples having significant different sides, a migration can occur from one glass fibre to the other and
could lead to wrong interpretation of the fastness of one side. It is advisable to check these samples using
large sampling procedure to prevent cross contamination of the glass fibre during the migration
procedure. The procedure is described in Annex A. If lower limit of detection is required, this procedure
could also be used.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 105-A03, Textiles — Tests for colour fastness — Part A03: Grey scale for assessing
staining (ISO 105-A03)
EN ISO 186, Paper and board — Sampling to determine average quality (ISO 186)
EN ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696)
EN ISO 4787, Laboratory glass and plastic ware — Volumetric instruments — Methods for testing of
capacity and for use (ISO 4787)
ISO 6588-2, Paper, board and pulps — Determination of pH of aqueous extracts — Part 2: Hot extraction
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
colour fastness
lack of transfer of colour from a paper to a non-stained glass-fibre paper, saturated with a test fluid and
evaluated visually for staining against a grey scale
4 Principle
A sample is brought into contact with glass fibre papers which have been saturated with a test fluid and
placed unde
...