oSIST prEN ISO 787-24:2025

General method of tests for pigments and extenders - Part 24: Determination of relative tinting strength of coloured pigments and relative scattering power of white pigments - Photometric methods (ISO/DIS 787-24:2025)

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.

Allgemeine Prüfverfahren für Pigmente und Füllstoffe - Teil 24: Bestimmung der relativen Farbstärke von Buntpigmenten und des relativen Streuvermögens von Weißpigmenten; Photometrisches Verfahren (ISO/DIS 787-24:2025)

Méthodes générales d_essai des pigments et matières de charge — Partie 24: Détermination du pouvoir colorant relatif des pigments colorés et du pouvoir diffusant relatif des pigments blancs — Méthodes photométriques (ISO/DIS 787-24:2025)

La présente partie de l'ISO 787 décrit des méthodes photométriques d'essai pour comparer dans la partie visible du spectre :
a) le pouvoir colorant de deux pigments colorés similaires (voir note 1) dispersés dans une résine alkyde sans siccatif;
b) le pouvoir diffusant de deux pigments blancs du même type dispersés dans une résine alkyde sans siccatif.
Ces méthodes d'essai fournissent une mesure instrumentale en complément des méthodes respectivement décrites dans les parties 16 et 17 de l'ISO 787, évitant la nécessité d'un contrôle visuel.
NOTES:
1) La présente Norme internationale ne convient pas pour la comparaison de pigments colorés dont la couleur en dégradé présente d'importants écarts.
2) Chaque fois que l'une de ces méthodes générales est applicable pour un pigment donné, il devra simplement être fait référence à la méthode appropriée dans la Norme internationale relative à ce pigment, en indiquant, dans une note, toutes les modifications de dé

Splošne metode preskušanja pigmentov in polnil - 24. del: Določanje relativne barvne jakosti barvnih pigmentov in relativne moči sipanja belih pigmentov - Fotometrijske metode (ISO/DIS 787-24:2025)

General Information

• Status: Not Published
• Public Enquiry End Date: 30-Nov-2025
• ICS: 87.060.10 - Pigments and extenders
• Technical Committee: PIP - Pigments and extenders
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 18-Sep-2025
• Due Date: 05-Feb-2026
• Completion Date: 15-Dec-2025
• Ref Project: prEN ISO 787-24 - 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 (ISO/DIS 787-24:2025)

Relations

• Revises: SIST EN ISO 787-24:1997 - General method of tests for pigments and extenders - Part 24: Determination of relative tinting strength of coloured pigments and relative scattering power of white pigments - Photometric methods (ISO 787-24:1985)
• Effective Date: 01-Nov-2025

Overview

The oSIST prEN ISO 787-24:2025:2025 standard, developed by CEN and harmonized with ISO/DIS 787-24:2025, specifies photometric test methods for evaluating pigments and extenders used in paints, coatings, and related industries. Specifically, this part focuses on the determination of relative tinting strength for coloured pigments and relative scattering power for white pigments. This standardized method provides a precise instrumental alternative to traditional visual comparison techniques detailed in ISO 787-16 and ISO 787-17.

Using photometric measurement techniques, the standard defines procedures for dispersing equal masses of pigments in specified pastes and calculating reflectivity to derive K/S values-an indicator of colour strength and scattering power. This approach ensures more accurate, reliable, and reproducible results, essential for quality control and material specification in pigment manufacturing and application.

Key Topics

• Tinting Strength of Coloured Pigments

  • Measures the ability of a coloured pigment to modify or impart colour to a base material.
  • Equal masses of a test pigment and a reference pigment are dispersed in the same quantity of white pigment paste.
  • Photometric reflectivity data is used to calculate K/S values, representing relative tinting strength.

• Scattering Power of White Pigments

  • Assesses the capacity of a white pigment to scatter light, impacting opacity and brightness.
  • Equal masses of white test and reference pigments are dispersed in black pigment paste for comparison.
  • Reflectivity at 550 nm wavelength is measured photometrically to obtain relative scattering power.

• Photometric Measurement Methods

  • Instrumental detection improves repeatability and objectivity over traditional visual assessments.
  • Utilizes Kubelka-Munk theory for analyzing spectral absorption and scattering coefficients.

• Sample Preparation and Testing

  • Standardizes dispersion techniques in alkyd resin without driers to maintain consistency.
  • Emphasizes precise sample weighing, film preparation, and measurement protocols.

• Updated Definitions and Normative References

  • Incorporates harmonized terminology consistent with ISO 18451-1.
  • References complementary ISO standards related to pigment characterization (e.g., ISO 591-1, ISO 787 series, ISO 18314).

Applications

• Quality Control in Pigment Production
  Manufacturers can use this standard to assess batch-to-batch consistency in pigment tinting strength and scattering power, ensuring product performance and customer satisfaction.

• Paints and Coatings Industry
  Enables formulators to select pigments with appropriate optical properties for specific applications such as coatings, inks, plastics, and textiles.

• Research and Development
  Facilitates the development of new pigment formulations by providing accurate photometric data to compare novel materials against established references.

• Regulatory and Standardization Compliance
  Provides a harmonized method for testing pigments that may be referenced in national and international regulations related to material performance.

• Material Specification
  Helps specifiers and purchasers verify pigment properties to ensure they meet required performance criteria for tinting and opacity.

Related Standards

• ISO 787 Series
  A comprehensive set covering various test methods for pigments and extenders, including volatile matter, pH value, density, fineness, and comparative colorimetric assessments.

• ISO 787-16 and ISO 787-17
  Earlier visual comparison methods for determining tinting strength and lightening power, respectively; photometric methods in oSIST prEN ISO 787-24:2025 serve as instrumental alternatives.

• ISO 18451-1
  Defines terminology relevant to colourants and pigments, ensuring standard language across pigment testing procedures.

• ISO 591-1
  Specifications and test methods for titanium dioxide pigments, a key white pigment used widely in scattering power assessments.

• ISO 18314-3
  Analytical colorimetry methods for special indices such as blackness value, supporting pigment characterization referenced in this standard.

• ISO 9277
  Provides the BET method for determining specific surface area, a parameter affecting pigment performance.

---

Adopting oSIST prEN ISO 787-24:2025:2025 supports accurate, reproducible, and standardized evaluation of pigment optical properties utilizing advanced photometric methods. This ensures reliable quality assurance and consistency in pigment usage across industrial and commercial applications.

Standards Content (Sample)

SLOVENSKI STANDARD
01-november-2025
Splošne metode preskušanja pigmentov in polnil - 24. del: Določanje relativne
barvne jakosti barvnih pigmentov in relativne moči sipanja belih pigmentov -
Fotometrijske metode (ISO/DIS 787-24:2025)
General method of tests for pigments and extenders - Part 24: Determination of relative
tinting strength of coloured pigments and relative scattering power of white pigments -
Photometric methods (ISO/DIS 787-24:2025)
Allgemeine Prüfverfahren für Pigmente und Füllstoffe - Teil 24: Bestimmung der relativen
Farbstärke von Buntpigmenten und des relativen Streuvermögens von Weißpigmenten;
Photometrisches Verfahren (ISO/DIS 787-24:2025)
Méthodes générales d_essai des pigments et matières de charge Partie 24:
Détermination du pouvoir colorant relatif des pigments colorés et du pouvoir diffusant
relatif des pigments blancs Méthodes photométriques (ISO/DIS 787-24:2025)
Ta slovenski standard je istoveten z: prEN ISO 787-24
ICS:
87.060.10 Pigmenti in polnila Pigments and extenders
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 787-24
ISO/TC 256
General methods of test for
Secretariat: DIN
pigments and extenders —
Voting begins on:
Part 24: 2025-09-10
Determination of relative tinting
Voting terminates on:
2025-12-03
strength of coloured pigments and
relative scattering power of white
pigments — Photometric methods
Méthodes générales d'essai des pigments et matières de charge —
Partie 24: Détermination du pouvoir colorant relatif des pigments
colorés et du pouvoir diffusant relatif des pigments blancs —
Méthodes photométriques
ICS: 87.060.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
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.
Reference number
ISO/DIS 787-24:2025(en)
DRAFT
ISO/DIS 787-24:2025(en)
International
Standard
ISO/DIS 787-24
ISO/TC 256
General methods of test for
Secretariat: DIN
pigments and extenders —
Voting begins on:
Part 24:
Determination of relative tinting
Voting terminates on:
strength of coloured pigments and
relative scattering power of white
pigments — Photometric methods
Méthodes générales d'essai des pigments et matières de charge —
Partie 24: Détermination du pouvoir colorant relatif des pigments
colorés et du pouvoir diffusant relatif des pigments blancs —
Méthodes photométriques
ICS: 87.060.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 787-24:2025(en)
ii
ISO/DIS 787-24:2025(en)
Contents Page
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 .4
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 .6
8.1.3 Preparation of test films .6
8.1.4 Measurement of ϱ or R .6
∞ ∞
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 .7
8.2.4 Preparation of test films .7
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
∞ ∞
Bibliography .32

iii
ISO/DIS 787-24:2025(en)
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 documents 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/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.
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 update and, where necessary, aligned with ISO 18451-1;
— in Clause 4.2 and 8.1.4 the method was opened to other tinting strength criterion, including a reference
to ISO 18314-2;
— the notes on the commercial availability of white pigment paste and black pigment paste and the
references to that note have been deleted;
— in Clause 5 former notes 2, 3 and 4 have been included in the main text;
— the headers for the first two columns in Table 1, Table 2 and Table 3 in Clause 5 were added, i.e.
characteristic and requirement;
— the characteristic “nigrometer index value” and its requirement in Clause 5 have been changed to
“blackness value M ” for the characteristic and to “203 to 215” for the requirement, and ISO 18314-3 has
Y
been added as test method for carbon black pigment (Clause 5, Table 2);
— the characteristic “volatile matter content” has been changed to “matter volatile at 105 °C” for carbon
black pigment (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);

iv
ISO/DIS 787-24:2025(en)
— 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 Clause 6.3 a reference was included which described the possibility of measuring paste films on a
moving carrier without any contact;
— in Clause 6.4 other light sources for the tristimulus colorimeter were allowed;
— 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
DRAFT International Standard ISO/DIS 787-24:2025(en)
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
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 is not appropriate for 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 787-16, General methods of test for pigments and extenders — Part 16: Determination of relative tinting
strength (or equivalent colouring value) and colour on reduction of coloured pigments — Visual comparison method
ISO 787-17, General methods of test for pigments and extenders — Part 17: Comparison of lightening power of
white pigments
ISO 787-23, General methods of test for pigments and extenders — Part 23: Determination of density (using a
centrifuge to remove entrained air)
ISO 1524, Paints, varnishes and printing inks — Determination of fineness of grind
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/DIS 787-24:2025(en)
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 18314-3, Analytical colorimetry — Part 3: Special indices
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18451-1 and the following 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 For coloured and black pigments
3.1.1
tinting strength
colour strength
measure of the ability of a colourant (3.19) to colour other materials because of its absorptive power
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 of coloured pigments in a material and is expressed in units
of reciprocal film thickness.
3.1.3
absorbance index
K (λ)
p
spectral absorption coefficient of the pigmented binder divided by the pigment concentration C :
m
K λ
()
K λ = (1)
()
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
percentage ratio of the tinting strength (3.122) of the colourant (3.19) under test related to the tinting
strength of a reference colourant
3.2 For white pigments
3.2.1
scattering power
ability of a pigmented medium to partly diffuse the incident light

ISO/DIS 787-24:2025(en)
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 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 of the pigmented binder divided by the pigment concentration C (see 3.1.3):
m
S λ
()
S ()λ = (3)
p
C
m
3.2.4
relative scattering power
percentage ratio of the scattering index of the white pigment under test to the scattering index of a reference
white pigment
3.3
reflectivity
ϱ
∞
reflectance of a paste or a paint film of such thickness that further increase in thickness gives no further
change in reflectance
*
The reflectivity  corrected according to Formula (A.2), is related to K/S by Formula (5)
∞
*
1−
()
∞
K
= (5)
*
S

∞
Values of K/S as a function of 100 ϱ or 100 R are given in Annex B.
∞ ∞
Note 1 to entry: Kubelka-Munk analysis is strictly applicable only to monochromatic radiation, as indicated in
Formula (1) to Formula (4). In practice, however, correct results are often also obtained if the mean value for wider
wavebands is taken, as is the case when filters are used. Hence, in the subsequent equations the symbol λ is omitted.
Note 2 to entry: In a dispersion containing a coloured or black pigment and a white pigment, K is assumed to be
characteristic of the coloured or black pigment and S of the white pigment.
3.4
reflectance factor
R
∞
ratio of the radiant flux reflected in the directions within a given cone by a paste or a paint film to that
reflected in the same directions by a perfect reflecting diffuser identically irradiated, when the thickness of
the paste or the paint film is such that further increase in thickness gives no further change in the ratio
4 Principle
4.1 General
The methods of test specified in this document provide an instrumental alternative to those specified in
ISO 787-16 and ISO 787-17 respectively, avoiding the necessity of visual matching.

ISO/DIS 787-24:2025(en)
4.2 Coloured and black pigments
Equal masses of a coloured pigment p and of an agreed reference pigment p are separately dispersed in
1 2
the same mass of the same white pigment paste. The reflectivity ϱ or the reflectance factor R of each
∞ ∞
dispersion is measured photometrically at a wavelength giving a minimum value of ϱ or R . From the
∞ ∞
corresponding values of K/S, the relative tinting strength, K , of the test pigment is given by Formula (6)
r
KS/ K
()
p1 p1
K = ×=100 ×100 (6)
r
K
KS/
()
p2
p2
where
K /S is the K/S value corresponding to ϱ or R of the test pigment;
p1 ∞ ∞
K /S is the K/S value corresponding to ϱ or R of the agreed reference pigment.
p2 ∞ ∞
A different tinting strength criterion, i.e. one that is not dependent on the minimal value of ϱ∞ or R∞, may be
used by agreement between the interested parties, but should be stated in the test report (for examples see
ISO 18314-2).
4.3 White pigments
Equal masses of a white test pigment p and of an agreed reference pigment p are separately dispersed
3 4
in the same mass of the same black pigment paste. The reflectivity ϱ or the reflectance factor R of each
∞ ∞
dispersion is measured photometrically at 550 nm or using a Y-filter. From the corresponding values of K/S,
the relative scattering power, S , of the test pigment, is given by Formula (7)
r
KS/ S
()
p4 p3
S = ×=100 ×100 (7)
r
S
KS/
()
p4
p3
where
K/S is the K/S value corresponding to ϱ or R of the test pigment;
p3 ∞ ∞
K/S is the K/S value corresponding to ϱ or R of the agreed reference pigment.
p4 ∞ ∞
5 Materials and equipment
5.1 White pigment paste, with the following composition
— 40 parts by mass of titanium dioxide, Grade R2, complying with the requirements of ISO 591-1;
— 56 parts by mass of alkyd resin (see Table 1);
NOTE The alkyd resin is based on a mixture of 63 % (mass fraction) linseed oil and 23 % (mass fraction) phthalic
anhydride.
— 4 parts by mass of calcium stearate.
Using a spatula, mix well so as to achieve preliminary wetting of the solids.
Then grind on the triple-roll mill (6.1) until the particle size is less than 5 µm when tested on a fineness-
of-grind gauge (see ISO 1524). Store the paste in an airtight container, preferably a collapsible tube with a
screw cap.
Table 1 — Alkyd resin complying with the following requirements
Characteristic Requirement Test method
acid value max. 15 mg KOH/g ISO 2114
viscosity (solvent free) 7 Pa·s to 10 Pa·s ISO 3219 (all parts)
hydroxyl content about 40 mg KOH/g ISO 4629 (all parts)

ISO/DIS 787-24:2025(en)
5.2 Black pigment paste, prepared as follows.
5.2.1 Mix 18,7 parts by mass of carbon black pigment (see Table 2) with 81,3 parts by mass of alkyd resin
(see Table 1 in 5.1) by use of a spatula. Pass the mixture six times through the triple-roll mill (6.1) to achieve
a uniform fine dispersion.
5.2.2 Mix 3,25 g of the intermediate paste prepared as described in 5.2.1 with 91,64 g of alkyd resin
(Table 1 in 5.1) and 5,11 g of fumed silica (see Table 3); pass the mixture once through the triple-roll mill.
NOTE The mixture specified in 5.2.2 is suitable for testing at a pigment volume concentration of 17 %.
Table 2 — Carbon black pigment of the lampblack type complying with the following requirements
Characteristic Requirement Test method
blackness value M 203 to 215 ISO 18314-3
Y
matter volatile at 105 °C about 1 % ISO 787-2
toluene extractable matter max. 0,15 % ISO 6209
2 2
specific surface area (BET) 25 m /g to 33 m /g ISO 4652
pH value 6 to 9 ISO 787-9
Table 3 — Fumed silica complying with the following requirements
Characteristic Requirement Test method
2 2
specific surface area (BET) 175 m /g to 225 m /g ISO 9277
pH value 3,6 to 4,5 ISO 787-9
6 Apparatus
6.1 Triple-roll mill.
6.2 Automatic muller, with ground glass plates, preferably water cooled, of diameter 180 mm to 250 mm
to which a variable but known force of up to about 1 kN may be applied. If the automatic muller does not
have water-cooled plates, take care that·the temperature during the grinding operation does not rise by
-1 -1
more than 10 °C. The driven glass plate should have a speed of rotation of between 70 min and 120 min
and the apparatus should have an arrangement for pre-setting the number of revolutions in multiples of 25.
Pre-condition new muller plates by milling a pigment in a suitable binder (system) for 1 000 revolutions
with a load applied to the plates. Remove the paste and discard.
Before use, check the surface of both plates for freedom from score marks, freedom from polished areas and
for an even opaque appearance.
6.3 Paste film holders, for example a suitable dish, for each test dispersion to support a paste film of
about 250 µm thickness; it may have a spacing ring.
Alternatives are to prepare a drawdown that is sufficiently thick to be completely opaque and to cover this
with a template so that an area corresponding to the sample port of the photometer is exposed, or to prepare
an opaque drawdown on a glass plate and measure through the glass.
The paste film can also be applied to a moving carrier and t
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