ISO/FDIS 787-24

General methods of test for pigments and extenders — Part 24: Photometric methods for determining the relative tinting strength of coloured pigments and the relative scattering power of white pigments

The method specified provide an instrumental alternative to those described in ISO 787/16 and ISO 787/17. Equal masses of a coloured material are separately dispersed in the same mass of the same white pigment paste. The reflectivity of each dispersion is measured photometrically. From the corresponding values of K/S the relative tinting strength is given. For measurement of the relative scattering power equal masses of a white test material and an agreed reference pigment are separately dispersed in the same mass of the same black pigment paste. The reflectivity of each dispersion is measured photometrically at 550 nm. From the corresponding values of K/S the relative scattering power is given.

Méthodes générales d’essai des pigments et matières de charge — Partie 24: Méthodes photométriques pour la détermination du pouvoir colorant relatif des pigments colorés et du pouvoir diffusant relatif des pigments blancs

General Information

• Status: Not Published
• ICS: 87.060.10 - Pigments and extenders
• Technical Committee: ISO/TC 256 - Pigments, dyestuffs and extenders
• Drafting Committee: ISO/TC 256/WG 3 - General test methods for colorants and extenders
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 25-Jun-2026
• Completion Date: 25-Jun-2026

Relations

• Consolidates: FprEN ISO 787-24 - General methods of test for pigments and extenders - Part 24: Photometric methods for determining the relative tinting strength of coloured pigments and the relative scattering power of white pigments (ISO/FDIS 787-24:2026)
• Effective Date: 12-Feb-2026
• Consolidates: ISO/IEC 19075-7:2021 - Information technology — Guidance for the use of database language SQL — Part 7: Polymorphic table functions
• Effective Date: 11-Nov-2023
• Revises: ISO 787-24:1985 - General methods of test for pigments and extenders — Part 24: Determination of relative tinting strength of coloured pigments and relative scattering power of white pigments — Photometric methods
• Effective Date: 28-Oct-2023

Overview

ISO/FDIS 787-24 specifies standardized photometric methods for determining the relative tinting strength of coloured pigments and the relative scattering power of white pigments. Developed by the International Organization for Standardization (ISO), this document provides clear, instrumental alternatives to the visual methods described in ISO 787-16 and ISO 787-17. By utilizing photometric analysis, the standard delivers greater accuracy and repeatability in measuring pigment performance, supporting quality control and product consistency in industries that utilize pigments and extenders.

The standard covers procedures for dispersing pigments in defined resin pastes, measuring reflectivity using photometric equipment, and calculating relative tinting strength or scattering power based on the Kubelka-Munk theory.

Key Topics

• Photometric Testing Methods

  • Instrumental techniques replace subjective visual assessment
  • Use of spectrophotometers and colorimeters for accurate reflectivity measurements

• Determining Relative Tinting Strength

  • Coloured pigments are compared by dispersing equal masses in a white pigment paste
  • The reflectivity of each dispersion is measured and the relative tinting strength is calculated

• Determining Relative Scattering Power

  • White pigments are compared by dispersing equal masses in a black pigment paste
  • Photometric measurement at 550 nm or using a Y-filter determines the relative scattering power

• Standardized Sample Preparation

  • Detailed requirements for materials, including alkyd resin composition and properties for titanium dioxide and carbon black pastes
  • Use of calibrated equipment such as triple-roll mills and automatic mullers

• Calculation Methods

  • Application of the Kubelka-Munk equation (K/S values) for result expression
  • Inclusion of up-to-date terminology and reference criteria according to the latest ISO standards

Applications

ISO/FDIS 787-24 is extensively used in sectors where pigment quality and performance are critical, such as:

• Paints and Coatings: Ensures color consistency and opacity in decorative, automotive, and industrial finishes
• Plastics Manufacturing: Provides objective data to adjust formulations for colored and white polymers
• Printing Inks: Supports reproducibility in print media through standardized pigment strength comparisons
• Quality Control Laboratories: Offers reliable procedures for ongoing pigment and extender verification
• Pigment and Extender Production: Assists manufacturers in benchmarking new products against reference materials

By standardizing photometric methods, the document helps organizations minimize variability, meet regulatory requirements, and ensure customer satisfaction by delivering products with predictable and stable color properties.

Related Standards

ISO/FDIS 787-24 is part of the broader ISO 787 series, which addresses general methods of test for pigments and extenders. Other relevant standards include:

• ISO 787-16: Visual comparison of tinting strength of colored pigments
• ISO 787-17: Comparison of relative scattering power of white pigments by visual means
• ISO 591-1: Titanium dioxide pigments for paints - Specifications and test methods
• ISO 15528: Sampling of paints, varnishes, and raw materials
• ISO 18314-2 and ISO 18314-3: Analytical colorimetry-Kubelka-Munk equation applications and special indices

Through alignment with these documents, ISO/FDIS 787-24 ensures a comprehensive approach to pigment evaluation, supporting international trade, regulatory compliance, and technical interoperability.

Keywords: ISO 787-24, photometric methods, relative tinting strength, scattering power, pigments, extenders, Kubelka-Munk, reflectivity, color measurement, pigment testing, standardization, quality control.

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/TC 256
General methods of test for
Secretariat: DIN
pigments and extenders —
Voting begins on:
2026-06-25
Part 24:
Photometric methods for
Voting terminates on:
2026-08-20
determining the relative tinting
strength of coloured pigments and
the relative scattering power of
white pigments
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 SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 256
General methods of test for
Secretariat: DIN
pigments and extenders —
Voting begins on:
Part 24:
Photometric methods for
Voting terminates on:
determining the relative tinting
strength of coloured pigments and
the relative scattering power of
white pigments
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 SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
3.1 Terms related to coloured and black pigments .2
3.2 Terms related to white pigments .2
3.3 Terms related to reflectivity .3
3.4 Terms related to reflectance factor .3
4 Principle . 3
4.1 General .3
4.2 Coloured and black pigments .3
4.3 White pigments . .4
5 Materials and equipment . 4
6 Apparatus . 5
7 Sampling . 6
8 Procedure . 6
8.1 Determination of relative tinting strength .6
8.1.1 Test pigment dispersion . .6
8.1.2 Reference pigment dispersion .7
8.1.3 Preparation of test films .7
8.1.4 Measurement of ϱ or R .7
∞ ∞
8.2 Determination of relative scattering power .7
8.2.1 General .7
8.2.2 Test pigment dispersion . .7
8.2.3 Reference pigment dispersion .8
8.2.4 Preparation of test films .8
8.2.5 Measurement of ϱ or R .8
∞ ∞
9 Expression of results . 8
10 Test report . 8
Annex A (informative) Reflectivity and Kubelka-Munk analysis .10
Bibliography .11

iii
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 ” has been replaced by “C “ as symbol for relative tinting strength;
r rel
— 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 ” for the characteristic and to “203 to 215” for the requirement, and ISO 18314-3 has been added as a
Y
test method (Clause 5, Table 2);
2 2
— the requirement for “specific surface area (BET)” has been changed to “25 m /g to 33 m /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);

iv
— 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.

v
FINAL DRAFT International Standard ISO/FDIS 787-24:2026(en)
General methods of test for pigments and extenders —
Part 24:
Photometric methods for determining the relative tinting
strength of coloured pigments and the relative scattering
power of white pigments
1 Scope
This document specifies photometric methods of test for comparing in the visible spectrum:
a) the tinting strength of two similar coloured pigments dispersed in an alkyd resin without a drier;
b) 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
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.
ISO 591-1, Titanium dioxide pigments for paints — Part 1: Specifications and methods of test
ISO 787-2, General methods of test for pigments and extenders — Part 2: Determination of matter volatile at
105 °C
ISO 787-9, General methods of test for pigments and extenders — Part 9: Determination of pH value of an
aqueous suspension
ISO 787-10, General methods of test for pigments and extenders — Part 10: Determination of density —
Pyknometer method
ISO 3219 (all parts), Rheology
ISO 2114, Plastics (polyester resins) and paints and varnishes (binders) — Determination of partial acid value
and total acid value
ISO 4629 (all parts), Binders for paints and varnishes — Determination of hydroxyl value
ISO 4652, Rubber compounding ingredients — Carbon black — Determination of specific surface area by
nitrogen adsorption methods — Single-point procedures
ISO 6209, Rubber compounding ingredients — Carbon black — Determination of solvent-extractable material
ISO 9277, Determination of the specific surface area of solids by gas adsorption — BET method
ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling

ISO 18314-2, Analytical colorimetry — Part 2: Saunderson correction, solutions of the Kubelka-Munk equation,
tinting strength, depth of shade and hiding power
ISO 18314-3, Analytical colorimetry — Part 3: Special indices
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 Terms related to coloured and black pigments
3.1.1
tinting strength
colour strength
measure of the ability of a colourant to colour other materials because of its absorptive power
[SOURCE: ISO 18451-1:2019, 3.122]
3.1.2
spectral absorption coefficient
K(λ)
fraction of the diffusely incident spectral radiant flux of wavelength λ that is absorbed in an elementary
layer within a material, divided by the thickness of the layer (Kubelka-Munk analysis)
Note 1 to entry: K(λ) is a measure of the tinting strength (3.1.1) of coloured pigments in a material.
3.1.3
absorption index
K (λ)
p
spectral absorption coefficient (3.1.2) of the pigmented binder divided by the pigment concentration C :
m
K 

K  

p
C
m
where C is the pigment concentration, for example, expressed as the ratio by mass of pigment to binder
m
3.1.4
relative tinting strength
relative colour strength
C
rel
percentage ratio of the tinting strength (3.1.1) of the colourant under test related to the tinting strength
(3.1.1) of a reference colourant
[SOURCE: ISO 18451-1:2019, 3.105, modified — the symbol C has been added.]
rel
3.2 Terms related to white pigments
3.2.1
scattering power
ability of a pigmented medium to partly diffuse the incident light

3.2.2
spectral scattering coefficient
S(λ)
net transfer of spectral radiant flux of wavelength λ in the outward direction from an elementary layer
within a body of material illuminated from outside, divided by the product of the thickness of the layer and
the difference between the magnitude of the flux in the two directions through the layer (Kubelka-Munk
analysis)
Note 1 to entry: S(λ) is a measure of the scattering power (3.2.1) of white pigments in a material and is expressed in
units of reciprocal film thickness.
3.2.3
scattering index
S (λ)
p
spectral scattering coefficient (3.2.2) of the pigmented binder divided by the pigment concentration C :
m
S 

S  

p
C
m
3.2.4
relative scattering power
percentage ratio of the scattering power of the white pigment under test to the scattering power of a
reference white pigment
[SOURCE: ISO 18451-1:2019, 3.104, modified — in the definition “scattering index” has been replaced twice
by “scattering power”.]
3.3 Terms related to reflectivity
3.3.1
reflectivity
ϱ
∞
reflectance of a paste or a paint film whose thickness is such that any further increase in thickness gives no
further change in reflectance
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ISO /TC 256/WG 3
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Date: 2026-05-11
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Secretariat: DIN
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Date: 2026-06-10 .
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General methods of test for pigments and extenders —
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Part 24:
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Photometric methods for determining the relative tinting strength
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of coloured pigments and the relative scattering power of white
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pigments
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Méthodes générales d'essai des pigments et matières de charge — Partie 24: Méthodes photométriques
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pour déterminer le pouvoir colorant relatif des pigments colorés et le pouvoir diffusant relatif des
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pigments blancs
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FDIS stage
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© ISO 2026
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
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ISO copyright office
from edge: 0.5 cm
CP 401 • Ch. de Blandonnet 8
CH--1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
Formatted: English (United Kingdom)

Formatted: Font: 10 pt
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Formatted: FooterPageRomanNumber, Space After: 0
pt, Line spacing: single
ii © ISO 2025 2026 – All rights reserved
ii
Formatted: Font: Bold
Formatted: HeaderCentered, Left
Contents Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
Foreword . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
3.1 Terms related to coloured and black pigments . 2
3.2 Terms related to white pigments . 3
3.3 Terms related to reflectivity . 3
3.4 Terms related to reflectance factor . 4
4 Principle . 4
4.1 General. 4
4.2 Coloured and black pigments . 4
4.3 White pigments . 4
5 Materials and equipment . 5
6 Apparatus . 6
7 Sampling . 7
8 Procedure . 7
8.1 Determination of relative tinting strength . 7
8.2 Determination of relative scattering power . 8
9 Expression of results . 9
10 Test report . 9
Annex A (informative) Reflectivity and Kubelka-Munk analysis . 11
Bibliography . 12

Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
3.1 For coloured and black pigments. 2
3.2 For white pigments . 2
4 Principle . 3
4.1 General. 3
4.2 Coloured and black pigments . 3
4.3 White pigments . 4
5 Materials and equipment . 4
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6 Apparatus . 5
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7 Sampling . 6
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8 Procedure . 6
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8.1 Determination of relative tinting strength . 6
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8.1.1 Test pigment dispersion . 6
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8.1.2 Reference pigment dispersion . 6
8.1.3 Preparation of test films . 7
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© ISO 2026 – All rights reserved
iii
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8.1.4 Measurement of ϱ or R . 7
∞ ∞
8.2 Determination of relative scattering power . 7
8.2.1 General. 7
8.2.2 Test pigment dispersion . 7
8.2.3 Reference pigment dispersion . 8
8.2.4 Preparation of test films . 8
8.2.5 Measurement of ϱ or R . 8
∞ ∞
9 Expression of results . 8
10 Test report . 8
Annex A (informative) Reflectivity and absorption and scattering coefficients . 9
Annex B (informative) K/S values as a function of measured ϱ or R . 10
∞ ∞
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iv © ISO 2025 2026 – All rights reserved
iv
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Formatted: HeaderCentered, Left
Foreword Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
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).
Formatted: English (United Kingdom)
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.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
Formatted: English (United Kingdom)
constitute an endorsement.
Formatted: Adjust space between Latin and Asian text,
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
Adjust space between Asian text and numbers
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Formatted: Default Paragraph Font
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
Formatted: Default Paragraph Font
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
Formatted: Default Paragraph Font
This document was prepared by Technical Committee ISO/TC 256, Pigments, dyestuffs and extenders, in
Formatted: Default Paragraph Font
collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 298,
Formatted: Adjust space between Latin and Asian text,
Pigments and extenders, in accordance with the Agreement on technical cooperation between ISO and CEN
Adjust space between Asian text and numbers, Tab
(Vienna Agreement).
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
This third edition cancels and replaces the second edition (ISO 787--24:1985), which has been technically
revised.
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Formatted: Default Paragraph Font
The main changes are as follows:
Formatted: Default Paragraph Font
— — the introduction has been deleted;
Formatted: Default Paragraph Font
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— — the normative references have been updated;
Formatted: Default Paragraph Font
— — in Clause 3,Clause 3, the definitions have been updated and, where necessary, aligned with
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ISO 18451--1;
Formatted: Font: 10 pt
— 3.1.33.1.3 “absorbance index” has been changed to “absorption index”;
Formatted: Font: 10 pt
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— subclause 4.14.1 has been added;
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— in 4.24.2, “K ” has been replaced by “C “ as symbol for relative tinting strength; Tab stops: Not at 17.2 cm
r rel
Formatted: Font: 11 pt
— — in 4.24.2 and 8.1.4,8.1.4, the method has been opened to other tinting strength criterion, including a
Formatted: FooterPageRomanNumber, Left, Space
reference to ISO 18314--2;
After: 0 pt, Tab stops: Not at 17.2 cm
© ISO 2026 – All rights reserved
v
Formatted: Font: Bold
Formatted: HeaderCentered
— — the characteristic “nigrometer index value” and its requirement have been changed to “blackness value
M ” for the characteristic and to “203 to 215” for the requirement, and ISO 18314--3 has been added as a
Y Formatted: Default Paragraph Font
test method (Clause 5, Table 2);(Clause 5, Table 2);
Formatted: Default Paragraph Font
2 2
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— — the requirement for “specific surface area (BET)” has been changed to “25 m /g to 33 m /g” for carbon
black pigment (Clause 5, Table 2);(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);(Clause 5, Table 2);
— — ISO 9277 has been added as the test method for the specific surface area (BET) for fumed silica
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(Clause 5, Table 3);(Clause 5, Table 3);
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— — in 6.3,in 6.3, a reference was included which described the possibility of measuring paste films on a
moving carrier without any contact;
— — in 6.4,6.4, additional light sources for the tristimulus colorimeter were included;
— — Annex AAnnex A has been modified and subdivided into by A.1A.1 and A.2;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.
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Any feedback or questions on this document should be directed to the user’s national standards body. A
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complete listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.
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vi © ISO 2025 2026 – All rights reserved
vi
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DRAFT International Standard ISO/DIS 787-24:2025(en)
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General methods of test for pigments and extenders —
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Part 24:
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Photometric methods for determining the relative tinting strength of
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coloured pigments and the relative scattering power of white
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pigments
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1 Scope
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This document specifies photometric methods of test for comparing in the visible spectrum:
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a) a) the tinting strength of two similar coloured pigments dispersed in an alkyd resin without a
drier;
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b) b) the scattering power of two white pigments of the same type dispersed in an alkyd resin
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without a drier.
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This document does not apply to the comparison of coloured pigments that on reduction differ greatly in
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colour.
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2 Normative references
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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, Formatted
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the latest edition of the referenced document (including any amendments) applies.
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ISO 591--1, Titanium dioxide pigments for paints — Part 1: Specifications and methods of test .
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ISO 787--2, General methods of test for pigments and extenders — Part 2: Determination of matter volatile at
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105 °C
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ISO 787--9, General methods of test for pigments and extenders — Part 9: Determination of pH value of an
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aqueous suspension
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ISO 787--10, General methods of test for pigments and extenders — Part 10: Determination of density —
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Pyknometer method
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ISO 3219 (all parts), Rheology .
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ISO 2114, Plastics (polyester resins) and paints and varnishes (binders) — Determination of partial acid value
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and total acid value
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ISO 4629 (all parts), Binders for paints and varnishes — Determination of hydroxyl value
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ISO 4652, Rubber compounding ingredients — Carbon black — Determination of specific surface area by
nitrogen adsorption methods — Single-point procedures
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ISO 6209, Rubber compounding ingredients — Carbon black — Determination of solvent-extractable material
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ISO 9277, Determination of the specific surface area of solids by gas adsorption — BET method
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ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling
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ISO 18314-2, Analytical colorimetry — Part 2: Saunderson correction, solutions of the Kubelka-Munk Formatted
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equation, tinting strength, depth of shade and hiding power
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ISO 18314--3, Analytical colorimetry — Part 3: Special indices .
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3 Terms and definitions
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For the purposes of this document, the following terms and definitions apply. .
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ISO and IEC maintain terminology databases for use in standardization at the following addresses:
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— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp Formatted
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— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
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3.1 Terms related to coloured and black pigments
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3.1.1 3.1.1
tinting strength
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colour strength
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measure of the ability of a colourant to colour other materials because of its absorptive power
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[SOURCE: ISO 18451-1:2019, 3.122]
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3.1.2 3.1.2
spectral absorption coefficient
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K(λ)
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fraction of the diffusely incident spectral radiant flux of wavelength λ that is absorbed in an elementary layer
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within a material, divided by the thickness of the layer (Kubelka-Munk analysis)
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Note 1 to entry: K(λ) is a measure of the tinting strength (3.1.1)(3.1.1) of coloured pigments in a
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material.
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3.1.3 3.1.3
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absorption index
K (λ) Formatted
p
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spectral absorption coefficient (3.1.2)(3.1.2) of the pigmented binder divided by the pigment concentration Cm:
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𝐾𝐾 𝜆𝜆 =
( )
p
𝐶𝐶
m
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𝐾𝐾(𝜆𝜆) Formatted
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𝐾𝐾 (𝜆𝜆) =
p
𝐶𝐶
m Formatted
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where C is the pigment concentration, for example, expressed as the ratio by mass of pigment to binder
m
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3.1.4 3.1.4
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relative tinting strength
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relative colour strength .
C
rel
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percentage ratio of the tinting strength (3.1.1)(3.1.1) of the colourant under test related to the tinting strength
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(3.1.1)(3.1.1) of a reference colourant
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2 © ISO 2025 2026 – All rights reserved
ISO/DISFDIS 787-24:2026(en)
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[SOURCE: ISO 18451-1:2019, 3.105, modified - The— the symbol C has been added.]
rel
3.2 Terms related to white pigments
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3.2.1 3.2.1
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scattering power
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ability of a pigmented medium to partly diffuse the incident light
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numbers
3.2.2 3.2.2
spectral scattering coefficient
S(λ)
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net transfer of spectral radiant flux of wavelength λ in the outward direction from an elementary layer within
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a body of material illuminated from outside, divided by the product of the thickness of the layer and the
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difference between the magnitude of the flux in the two directions through the layer (Kubelka-Munk analysis)
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Note 1 to entry: S(λ) is a measure of the scattering power (3.2.1)(3.2.1) of white pigments in a material
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and is expressed in units of reciprocal film thickness.
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stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.2.3 3.2.3
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
scattering index
Sp(λ) Formatted: TermNum3, Adjust space between Latin
spectral scattering coefficient (3.2.2)(3.2.2) of the pigmented binder divided by the pigment concentration C : and Asian text, Adjust space between Asian text and
m
numbers
𝑆𝑆(𝜆𝜆)
𝑆𝑆 (𝜆𝜆) =     Formatted: Regular Italic, Font: Bold, Not Italic
p
𝐶𝐶
m
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𝑆𝑆(𝜆𝜆)
Lowered by
3.2.4𝑆𝑆 (𝜆𝜆) =
p
𝐶𝐶
m
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3.2.4
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relative scattering power
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percentage ratio of the scattering power of the white pigment under test to the scattering power of a reference
white pigment
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and Asian text, Adjust space between Asian text and
[SOURCE: ISO 18451-1:2019, 3.104, modified – In— in the definition “scattering index” has been replaced
numbers
twice by “scattering power”.]
3.3 3.3 Terms related to reflectivity
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3.3.1 3.3.1
reflectivity Formatted: TermNum3, Adjust space between Latin
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∞
reflectance of a paste or a paint film of suchwhose thickness is such that any further increase in thickness gives numbers
no further change in reflectance
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Note 1 to entry: For Kubelka-Munk analysis, see ISO 18314-2 and Annex A can be referred
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to.Annex A.
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© ISO 2026 – All rights reserved
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3.4 3.4 Terms related to reflectance factor
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3.4.1 3.4.1
reflectance factor Formatted: TermNum3, Adjust space between Latin
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ratio of the radiant flux reflected in the directions within a given cone by a paste or a paint film to that reflected numbers
in the same directions by a perfect reflecting diffuser identically irradiated, when the thickness of the paste or
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the paint film is such that any further increase in thickness gives no further change in the ratio
4 Principle
4.1 General
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The methods of test specified in this document provide an instrumental alternative to those specified in
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ISO 787--16 and ISO 787--17 respectively, avoiding the necessity of visual matching.
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4.2 Coloured and black pigments
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Equal masses of a coloured test pigment p1 and of an agreed
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