National foreword

This British Standard is the UK implementation of EN ISO 787‑24:2026. It is identical to ISO 787‑24:2026. It supersedes BS EN ISO 787‑24:1995, which is withdrawn.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 October 2026.

This European Standard was approved by CEN on 21 September 2026.

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, Czechia, 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 foreword

This document (EN ISO 787‑24:2026) has been prepared by Technical Committee ISO/TC 256 "Pigments, dyestuffs and extenders" in collaboration with Technical Committee CEN/TC 298 “Pigments and extenders” 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 April 2027, and conflicting national standards shall be withdrawn at the latest by April 2027.

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 ISO 787‑24:1995.

Any feedback and questions on this document should be directed to the users’ national standards body/national committee. A complete listing of these bodies can be found on the CEN website.

According to the CEN-CENELEC Internal Regulations, the national standards organizations 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.

Endorsement notice

The text of ISO 787‑24:2026 has been approved by CEN as EN ISO 787‑24:2026 without any modification.

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO document should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 256, Pigments, dyestuffs and extenders, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 298, Pigments and extenders, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This third edition cancels and replaces the second edition (ISO 787‑24:1985), which has been technically revised.

The main changes are as follows:

the introduction has been deleted;
the normative references have been updated;
in Clause 3, the definitions have been updated and, where necessary, aligned with ISO 18451‑1;
3.1.3 “absorbance index” has been changed to “absorption index”;
4.1 has been added;
in 4.2, “K_r” has been replaced by “C_rel“ as symbol for relative tinting strength;
in 4.2 and 8.1.4, the method has been opened to other tinting strength criterion, including a reference to ISO 18314‑2;
the characteristic “nigrometer index value” and its requirement have been changed to “blackness value M_Y” for the characteristic and to “203 to 215” for the requirement, and ISO 18314‑3 has been added as a test method (Clause 5, Table 2);
the requirement for “specific surface area (BET)” has been changed to “25 m²/g to 33 m²/g” for carbon black pigment (Clause 5, Table 2);
the requirement for the pH value has been changed to “6 to 9” for carbon black pigment (Clause 5, Table 2);
ISO 9277 has been added as the test method for the specific surface area (BET) for fumed silica (Clause 5, Table 3);
in 6.3, a reference was included which described the possibility of measuring paste films on a moving carrier without any contact;
in 6.4, additional light sources for the tristimulus colorimeter were included;
Annex A has been modified and subdivided into A.1 and A.2;
Annex B has been deleted;
a bibliography has been added.

A list of all parts in the ISO 787 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

1 Scope

This document specifies photometric methods of test for comparing in the visible spectrum:

the tinting strength of two similar coloured pigments dispersed in an alkyd resin without a drier;
the scattering power of two white pigments of the same type dispersed in an alkyd resin without a drier.

This document does not apply to the comparison of coloured pigments that on reduction differ greatly in colour.

2 Normative references

3 Terms and definitions

3.1 Terms related to coloured and black pigments

3.2 Terms related to white pigments

3.3 Terms related to reflectivity

3.4 Terms related to reflectance factor

4 Principle

4.1 General

4.2 Coloured and black pigments

4.3 White pigments

5 Materials and equipment

5.1

5.2

6 Apparatus

6.1 Triple-roll mill.

6.2

6.3

6.4

7 Sampling

8 Procedure

8.1 Determination of relative tinting strength

8.2 Determination of relative scattering power

9 Expression of results

10 Test report

Bibliography