oSIST prEN ISO 20427:2025

Pigments and extenders - Dispersion procedure for sedimentation-based particle sizing of suspended pigment or extender with liquid sedimentation methods (ISO/DIS 20427:2025)

This document specifies sample preparation methods to determine the size distribution of separate particles of a single pigment or extender, which is dispersed in a liquid by application of a standardized dispersion procedure, using an ultrasonic device, shaker device or wet jet mill.
The sample preparation methods described are optimized for measurements carried out with a particle sizing technique based on sedimentation. This technique relies on particle migration due to gravitation or centrifugal forces and requires a density contrast between the particles and the liquid phase.

Pigmente und Füllstoffe - Dispergierverfahren zur sedimentativen Teilchengrößenbestimmung von suspendierten Pigmenten oder Füllstoffen mit Flüssigsedimentationsverfahren (ISO/DIS 20427:2025)

Pigments et matières de charge - Mode opératoire de dispersion pour la détermination granulométrique basée sur la sédimentation des pigments ou matières de charge en suspension par des méthodes de sédimentation dans un liquide (ISO/DIS 20427:2025)

Le présent document décrit des méthodes de préparation d’échantillon pour la détermination de la distribution granulométrique de particules séparées d’un pigment ou d’une matière de charge unique, qui est dispersé(e) dans un liquide en appliquant un mode opératoire de dispersion normalisé à l’aide d’un dispositif à ultrasons, d’un agitateur ou d’un broyeur à jets en voie humide.
Les méthodes de préparation d’échantillon décrites sont optimisées pour les mesurages effectués avec une technique de détermination granulométrique basée sur la sédimentation. Cette technique repose sur la migration des particules due à la gravité ou aux forces centrifuges et nécessite un contraste de densité entre les particules et la phase liquide.

Pigmenti in polnila - Postopek disperzije za določanje porazdelitve velikosti delcev na podlagi sedimentacije suspendiranih pigmentov ali polnil v tekoči fazi (ISO/DIS 20427:2025)

General Information

• Status: Not Published
• Public Enquiry End Date: 02-Jul-2025
• ICS: 87.060.10 - Pigments and extenders
• Technical Committee: PIP - Pigments and extenders
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 14-May-2025
• Due Date: 01-Oct-2025
• Completion Date: 18-Jul-2025
• Ref Project: prEN ISO 20427 - Pigments and extenders - Dispersion procedure for sedimentation-based particle sizing of suspended pigment or extender with liquid sedimentation methods (ISO/DIS 20427:2025)

Relations

• Revises: SIST EN ISO 20427:2025 - Pigments and extenders - Dispersion procedure for sedimentation-based particle sizing of suspended pigment or extender with liquid sedimentation methods (ISO 20427:2023)
• Effective Date: 01-Jun-2025

Overview

prEN ISO 20427 (ISO/DIS 20427:2025) is a CEN/ISO draft standard that specifies sample preparation and dispersion procedures for determining particle size distributions of individual pigments and extenders when measured using sedimentation-based liquid particle sizing methods. The document covers standardized dispersion using ultrasonic devices, shaker devices and wet jet mills, and is optimized for sedimentation techniques that rely on gravitational or centrifugal migration of particles and require a density contrast between particles and the liquid phase.

Key topics and requirements

• Scope and objective: Preparation of single-pigment or single-extender suspensions for accurate particle sizing by liquid sedimentation.
• Dispersion principles: Guidance on ultrasonic dispersion (probe and bath), wet jet milling and shaker-based methods, including energy input considerations.
• Sedimentation techniques covered: Stokesian sedimentation, disc-type and cuvette-type centrifuges, gravitation-based methods and related field-flow techniques.
• Apparatus and settings: Specifications and recommended settings for dispersion equipment to ensure reproducible de-agglomeration without altering primary particle size.
• Sample handling: Procedures for sampling, reagents (e.g., laboratory water), sample preparation and recommendations optimized for sedimentation measurements.
• Measurement and reporting: Directions on expressing particle size distributions, measurement results and required content of the test report.
• Annexes: Practical, substance-specific procedures and protocols - including energy input determination (normative Annex A) and informative procedures for common pigments/extenders (TiO2, CaCO3, Fe2O3, carbon black, and a general dispersion procedure).

Applications and users

• Laboratories performing particle size analysis of pigments and extenders for quality control, R&D and material specification.
• Paint, coatings, plastics and inks manufacturers needing reproducible dispersion methods before sedimentation-based sizing.
• Instrument manufacturers and service labs seeking harmonized sample-preparation protocols to ensure comparability of sedimentation results.
• Regulatory and procurement bodies referencing standardized test preparation in specifications or conformity assessments.

Practical value

• Ensures consistency and repeatability in particle size measurement by aligning dispersion energy, equipment choice and sampling practices with sedimentation methods.
• Helps avoid under- or over-dispersion that can bias sedimentation-based size distributions.
• Provides substance-specific guidance (annexes) that reduces development time for lab procedures and improves inter-laboratory comparability.

Related standards

Key normative references in the draft include ISO 13317 (gravitational liquid sedimentation series), ISO 13318 (centrifugal liquid sedimentation), ISO 18451 (pigments terminology) and ISO 3696 (laboratory water). These should be consulted alongside ISO/DIS 20427 for complete test-method workflows.

Keywords: pigments, extenders, dispersion procedure, particle sizing, sedimentation-based, ultrasonic dispersion, wet jet mill, shaker dispersion, ISO/DIS 20427:2025, liquid sedimentation methods.

Standards Content (Sample)

SLOVENSKI STANDARD
01-junij-2025
Pigmenti in polnila - Postopek disperzije za določanje porazdelitve velikosti delcev
na podlagi sedimentacije suspendiranih pigmentov ali polnil v tekoči fazi (ISO/DIS
20427:2025)
Pigments and extenders - Dispersion procedure for sedimentation-based particle sizing
of suspended pigment or extender with liquid sedimentation methods (ISO/DIS
20427:2025)
Pigmente und Füllstoffe - Dispergierverfahren zur sedimentativen
Teilchengrößenbestimmung von suspendierten Pigmenten oder Füllstoffen mit
Flüssigsedimentationsverfahren (ISO/DIS 20427:2025)
Pigments et matières de charge - Mode opératoire de dispersion pour la détermination
granulométrique basée sur la sédimentation des pigments ou matières de charge en
suspension par des méthodes de sédimentation dans un liquide (ISO/DIS 20427:2025)
Ta slovenski standard je istoveten z: prEN ISO 20427
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 20427
ISO/TC 256
Pigments and extenders —
Secretariat: DIN
Dispersion procedure for
Voting begins on:
sedimentation-based particle sizing
2025-05-06
of suspended pigment or extender
Voting terminates on:
with liquid sedimentation methods
2025-07-29
Pigments et matières de charge — Mode opératoire de
dispersion pour la détermination granulométrique basée sur la
sédimentation des pigments ou matières de charge en suspension
par des méthodes de sédimentation dans un liquide
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 is circulated as received from the committee 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 20427:2025(en)
DRAFT
ISO/DIS 20427:2025(en)
International
Standard
ISO/DIS 20427
ISO/TC 256
Pigments and extenders —
Secretariat: DIN
Dispersion procedure for
Voting begins on:
sedimentation-based particle sizing
of suspended pigment or extender
Voting terminates on:
with liquid sedimentation methods
Pigments et matières de charge — Mode opératoire de
dispersion pour la détermination granulométrique basée sur la
sédimentation des pigments ou matières de charge en suspension
par des méthodes de sédimentation dans un liquide
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 is circulated as received from the committee 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 20427:2025(en)
ii
ISO/DIS 20427:2025(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principles of dispersion. 3
4.1 Principles of ultrasonic dispersion .3
4.2 Principle of wet jet mill dispersion . .3
4.3 Principle of shaker-based dispersion .3
5 Principles of sedimentation-based techniques for particle size analysis . 4
5.1 Stokesian sedimentation analysis .4
5.2 Disc-type centrifuges .4
5.3 Cuvette-type centrifuges . .4
5.4 Gravitation-based sedimentation methods .4
5.5 Centrifugal field-flow fractionation method .5
6 Apparatus . 5
6.1 Apparatus for ultrasonic dispersion .5
6.2 Apparatus for wet jet milling dispersion .5
7 Settings for dispersion . 7
7.1 Procedure of ultrasonic dispersion using a probe-type sonicator .7
7.2 Procedure of ultrasonic dispersion using a bath-type sonicator .8
7.3 Procedure of shaker-based dispersion .8
8 Dispersion procedure . 9
8.1 General .9
8.2 Sampling for dispersion.9
8.3 Reagents .9
8.4 Recommendations for sample preparation.10
9 Sampling . 10
10 Measurement and expression of results . 10
11 Test report . 10
Annex A (normative) Protocol for the determination of energy input .12
Annex B (informative) Limits for ultrasonic dispersion procedure .15
Annex C (informative) Procedures for dispersion of TiO pigments .16
Annex D (informative) Procedure for dispersion of CaCO with wet jet milling . 17
Annex E (informative) Procedure for the dispersion of Fe O with an ultrasonic probe .18
2 3
Annex F (informative) Procedure for dispersion of carbon black . 19
Annex G (informative) General procedure for dispersion of pigment or extender .20
Bibliography .23

iii
ISO/DIS 20427:2025(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 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 second edition cancels and replaces the first edition (ISO 20427:2023), which has been technically
revised.
The main changes are as follows:
— in Clause 3 a reference to the vocabulary standards series ISO 18451 has been added;
— in 5.4, paragraph 1, a reference to ISO 13317-5 has been added;
— 5.4, paragraph 2, has been re-written for better comprehensibility and a reference to ISO 13317-4 has
been added;
— in 5.5 a note has been added with additional information on the effective particle density;
— 6.2, the last list item of A.2.2 and the first list item of A.2.3 have been re-written for better comprehensibility;
— in 6.9, Table 1, row 2, column 1, “Subtype” has been added;
— in 6.9, Table 2, row 3, column 5, “Optical” has been deleted;
— in 6.9, Table 2, row 7, columns 2 to 4, the entries have been changed to “2,5 % mass fraction” and a table
footnote has been added explaining the density dependency of these values;
— in 6.9, Table 2, row 9, column 3, “class cylinder beaker” has been changed to “sedimentation bath”;
— in the last paragraph of 7.2 “geometric” has been deleted;
— in the last paragraph of 7.3 the given unit has been changed from “300 W/ml” to “300 W/(ml ×s)”;
— in Clause 10 a note has been added with a mathematical definition of precision;
— to the formula keys of Formulae (A.1), (A.2) and (A.3) an explanation of “dT/dt” has been added;

iv
ISO/DIS 20427:2025(en)
— in the second list item of C.1 and Annex E the distance between the beaker bottom and the ultrasonic
probe has been changed from 5 mm to 10 mm;
— in the third list item of Annex E the unit of the ultrasonic treatment has been changed from “240 W/ml”
to “240 W/(ml × s)”;
— in the third list item of G.2 and G.3 a footnote has been added to explain why a temperature of 40 °C is
important;
— in the last list item of G.2 and G.3 a footnote has been added to explain the influence of the cooling bath
on the sonication power;
— the normative references have been updated.
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 20427:2025(en)
Pigments and extenders — Dispersion procedure for
sedimentation-based particle sizing of suspended pigment or
extender with liquid sedimentation methods
1 Scope
This document specifies sample preparation methods to determine the size distribution of separate particles
of a single pigment or extender, which is dispersed in a liquid by application of a standardized dispersion
procedure, using an ultrasonic device, shaker device or wet jet mill.
The sample preparation methods described are optimized for measurements carried out with a particle
sizing technique based on sedimentation. This technique relies on particle migration due to gravitation or
centrifugal forces and requires a density contrast between the particles and the liquid phase.
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 3696, Water for analytical laboratory use — Specification and test methods
ISO 9276-1, Representation of results of particle size analysis — Part 1: Graphical representation
ISO 13317-1, Determination of particle size distribution by gravitational liquid sedimentation methods — Part
1: General principles, requirements and guidance
ISO 13317-2, Determination of particle size distribution by gravitational liquid sedimentation methods — Part
2: Fixed pipette method
ISO 13317-3, Determination of particle size distribution by gravitational liquid sedimentation methods — Part
3: X-ray gravitational technique
ISO 13317-4, Determination of particle size distribution by gravitational liquid sedimentation methods — Part
4: Balance method
ISO 13317-5, Determination of particle size distribution by gravitational liquid sedimentation methods — Part
5: Photosedimentation techniques
ISO 13318-1:2001, Determination of particle size distribution by centrifugal liquid sedimentation methods —
Part 1: General principles and guidelines
ISO 13318-2, Determination of particle size distribution by centrifugal liquid sedimentation methods — Part 2:
Photocentrifuge method
ISO 13318-3, Determination of particle size distribution by centrifugal liquid sedimentation methods — Part 3:
Centrifugal X-ray method
ISO 18451 (all parts), Pigments, dyestuffs and extenders — Terminology
ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling
ASTM D5965, Standard Test Methods for Density of Coating Powders

ISO/DIS 20427:2025(en)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18451 (all parts) 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
nanoscale
length range from approximately 1 nm to 100 nm
Note 1 to entry: Properties that are not extrapolations from a larger size are predominantly exhibited in this size
range. For such properties, the size limits are considered approximate.
Note 2 to entry: The lower limit in this definition (approximately 1 nm) is introduced to avoid single and small groups
of atoms from being designated as nano-objects or elements of nanostructures, which can be implied by the absence
of a lower limit.
[SOURCE: ISO 80004-1:2023, 3.1.1 — modified, notes 1 and 2 to entry have been added.]
3.2
nanoparticle
nano-object with all external dimensions in the nanoscale (3.1) where the lengths of the longest and the
shortest axes of the nano-object do not differ significantly
Note 1 to entry: If the dimensions differ significantly (typically by more than three times), terms such as nanofibre or
nanoplate may are preferred to the term nanoparticle.
[SOURCE: ISO 80004-1:2023, 3.3.4, modified — "where the lengths of the longest and the shortest axes of the
nano-object do not differ significantly" has been added to the definition.]
3.3
agglomerate
collection of weakly or medium strongly bound particles where the resulting external surface area is similar
to the sum of the surface areas of the individual components
Note 1 to entry: The forces holding an agglomerate together are weak forces, for example van der Waals or simple
physical entanglement.
Note 2 to entry: Agglomerates are also termed secondary particles and the original source particles are termed
primary particles (3.5).
[SOURCE: ISO 80004-1:2023, 3.2.4]
3.4
aggregate
particle comprising strongly bonded or fused particles where the resulting external surface area is
significantly smaller than the sum of surface areas of the individual components
Note 1 to entry: The forces holding an aggregate together are strong forces, for example covalent or ionic bonds, or those
resulting from sintering or complex physical entanglement, or otherwise combined former primary particles (3.5).
Note 2 to entry: Aggregates are also termed secondary particles and the original source particles are termed primary
particles (3.5).
[SOURCE: ISO 80004-1:2023, 3.2.5, modified — "or otherwise combined former primary particles" has been
added to the end of note 1 to entry.]

ISO/DIS 20427:2025(en)
3.5
primary particle
single nano-object with at least one of three external dimensions at the nanoscale
Note 1 to entry: Sometimes, if the primary particle is present in crystalline form, it also contains twinning boundaries.
3.6
spin fluid
inert liquid which is injected into the disc of a disc centrifuge photosedimentometer prior to the sample to
define a certain radius dependent gradient of viscosity for sedimentation
Note 1 to entry: Alkaline conditions minimize agglomeration of dispersed aggregates in most cases.
3.7
wet jet milling
dispersing method of particles in liquid phase using the complex shear force arising from turbulent flow in
the channel and cavitation from the abrupt pressure change
Note 1 to entry: This method is also called high pressure homogenizer method.
4 Principles of dispersion
4.1 Principles of ultrasonic dispersion
A piezo electrical ceramic material is driven by an applied alternating current electrical field to expand and
shrink periodically at an ultrasonic frequency in the range of 15 kHz up to 80 kHz and more. This movement
creates acoustic waves moving through the dispersion, which produce cavitation bubbles. The collapse of
these cavitation bubbles leads locally to strong thermal effects and shear-stress, which are responsible for
the destruction of agglomerates and even aggregates.
Energy density of sonication, temperature and particle volume concentration of the dispersion are critical
parameters of sonication and should be held at recipe values strictly.
In addition to probe-type sonicators ultra sonic (US) baths, inverted cup-horn sonicators and so-called vial-
tweeters also exist. US baths, cup-horn dispersers and vial-tweeters are known as indirect dispersers, where
sound energy is inserted via the wall of the container. Determining the energy input of these dispersers is
[9]
much more difficult than for probe sonication, but contamination is reduced .
4.2 Principle of wet jet mill dispersion
The wet jet milling method is a wet-type milling to disintegrate agglomerates of powder samples in liquid. In
this method, particles suspended in a liquid medium are passed through a narrow channel at high pressure.
Then, the suspension of the particles is enhanced by the complex shear force arising from turbulent flow in
the channel. In addition, the high pressure in the narrow channel induces the cavitation bubbles from the
abrupt pressure change. The burst of the cavitation bubbles then work to disperse powder samples in the
liquid phase, as in the ultra-sonication method. The advantage of this dispersion technique is that it yields
suspensions with low contamination, unlike the ultra-sonic homogenizer method. The pressure range is the
important factor to disperse the powder samples in the liquid phase. Typically, the pressure range is from
[10][11]
80 MPa to 245 MPa .
4.3 Principle of shaker-based dispersion
The shaker device should be built like a plate with holders for the high-density polyethylene (HDPE) bottles
(see Annex B). A successful dispersion is achieved when the plate is shaking vertically from back to front
with a vibration amplitude of minimum 32 mm and a frequency of 660 Hz.
Important aspects are:
— inclusion of grinding beads, high loading;

ISO/DIS 20427:2025(en)
— particle dispersion limitations: agglomerates/aggregates <100 µm in a liquid (viscous medium);
— grinding beads are agitated by rotary, tumbling and/or 2D-vibratory motion of the container/vessel;
— shear and elongational stress on agglomerates at squeezing of liquid between colliding grinding beads
[12][13]
and impulse exchange from collisions of agglomerates with grinding beads .
5 Principles of sedimentation-based techniques for particle size analysis
5.1 Stokesian sedimentation analysis
For all sedimentation-based procedures for particle sizing which are cited in this document, Stokesian
sedimentation analysis of dispersions is used. ISO 13318-1:2001, 4.1 describes in detail the general
procedure and calculations used to approach a particle size distribution of dispersed particles.
5.2 Disc-type centrifuges
The particles settle within an optically clear, rotating disc. When particles approach the outside edge of
the rotating disc, they block/scatter a portion of a light beam or X-ray beam that passes through the disc.
The change in light intensity shall be continuously recorded and converted by the operating software into a
particle size distribution, in accordance with ISO 13318-1.
Instead of detecting the local particle concentration with optical turbidity, X-ray absorption shall be used in
certain instruments with the advantage of direct particle mass dependency, in accordance with ISO 13318-3.
5.3 Cuvette-type centrifuges
The cuvette-type centrifuge is a special analytical centrifuge that instantaneously measures the particle
concentration at one or more radial positions within the rotating sedimentation cuvette.
For instance, space- and time-resolved extinction of the transmitted light across the entire length of the
sample allows the analysis of particle and droplet velocity distributions for creaming and sedimentation
phenomena without the need of any material data. This process additionally performs particle sizing
according to ISO 13318-2.
−1 −1
The centrifugal speed of these instruments is typically between 50 min and 60 000 min . Instruments with
−1
a centrifugal speed below 10 000 min are typically called cuvette centrifuges. Devices which can rotate
−1 −1
above 10 000 min rotation are called ultracentrifuge. For centrifugal speeds greater than 6 000 min , the
detection of particle sizes is limited to 1 µm or below.
5.4 Gravitation-based sedimentation methods
The gravitation-based liquid sedimentation shall be executed using four different techniques: the fixed
pipette method in accordance with ISO 13317-2, the X-ray gravitation-based technique in accordance with
ISO 13317-3, the balance method in accordance with ISO 13317-4 and gravitation-based photosedimentation
in accordance with ISO 13317-5.
Using the balance method in accordance with ISO 13317-4 and the pipette method in accordance with
ISO 13317-2, achieving a resolution below 1 µm is challenging due to the limitations of the detection
mechanisms employed. The X-ray sedimentation on the other hand depends on vibration isolation and
detector quality. It can resolve 100 nm, similar to the photosedimentation.
Therefore, only the liquid X-ray sedimentation in accordance with ISO 13317-1 and ISO 13317-3 is included
in this document.
The concentration of a dispersed sample is measured by the attenuation of an X-ray beam. A stable, narrow,
monochromatic collimated beam of X-rays passes through a suspension of the sample and is detected
at a known distance from the top of the sample cell. The sample cell is filled completely with the sample
suspension for the duration of the analysis. The settling height at which the particle concentration is

ISO/DIS 20427:2025(en)
determined may be reduced during the analysis for the purpose of obtaining a more rapid analysis compared
to an analysis where all measurements are made at the same height value. The cumulative mass percentage of
the sample present at a given sedimentation height is continuously determined. The X-ray signal attenuation
at the known height is compared to the attenuation in the suspending liquid and also to the attenuation in
the homogeneously dispersed sample present in the liquid. The attenuation of the emergent X-ray beam is
proportional to the mass of the powder in the beam.
5.5 Centrifugal field-flow fractionation method
Field-flow fractionation is a flow-based separation methodology. Centrifugal field-flow fractionation (CF3)
is a separation technique that uses a centrifugal field applied perpendicular to a circular channel that spins
around its axis to achieve size separation of particles between the limits of 10 nm and 50 µm. In this method,
separation is governed by a combination of size and effective particle density, indicating that applicable size
range is dependent on and limited by the effective particle density.
NOTE The effective particle density is defined by the particle's hydrodynamic diameter, which depends on the
particle shape. It is only identical to the material density measured with He-Pycnometry if the particles are spherical.
With an increasing degree of aggregation or deviation from a spherical shape, the effective particle density decreases.
In CF3, the mobile phase and analyte flow longitudinally through the channel. The channel is designed to
separate the sample components along its length, resulting in the elution of constituents at different times.
The channel and its large aspect ratio are designed to promote parabolic or near-parabolic laminar flow
between two infinite planes under normal operational conditions. Fractionation is achieved during passage
through the channel, based on the velocity flow profile, after which the mobile phase containing separated
constituents exits to online detectors and/or a fraction collector for off-line analysis. Common detectors
used for analysis of pigment and extender include ultraviolet-visible (UV-Vis) absorbance, fluorescence,
multi-angle light scattering (MALS), dynamic light scattering (DLS) and element detectors such as
the inductively coupled plasma mass spectrometer (ICP-MS). Combinational analysis of the sizing and
concentration evaluation detectors, as well as the size distribution analysis have been performed using this
method according to ISO/TS 21362.
6 Apparatus
Use standard laboratory apparatus, together with the following.
6.1 Apparatus for ultrasonic dispersion
6.1.1 Probe-type sonicator, with at least 100 W power and a frequency of 10 kHz to 100 kHz.
This type of sonicator has been found to be an effective means of dispersing particulate materials in liquid
dispersion from agglomerates into discrete primary particles or/and aggregates. The temperature of the
dispersion during sonication should be held as low as possible, around typical room temperature, in order to
maintain conditions for good stability of the dispersing agents.
6.1.2 Bath-type sonicator, with at least 50 W power and a frequency of 10 kHz to 100 kHz.
6.2 Apparatus for wet jet milling dispersion
The wet jet milling apparatus is designed for dispersing, crushing, emulsifying, and surface-modifying
[14][15]
materials under pressures of up to 245 MPa. It comprises high-voltage and ultra-high-pressure
components. During operation, the powder suspension is pressurized by the intensifier, accelerated through
the nozzle, and dispersed via complex shear forces from turbulent flow and cavitation induced by sudden
pressure changes. The maximum jet pressure is determined by the nozzle diameter, typically ranging from
0,05 mm to 0,15 mm. To prevent clogging, the particle diameter should be smaller than the nozzle diameter,
ideally less than half of it. The apparatus processes at approximately 0,1 l/min and is compatible with
both organic and aqueous solvents. However, water is generally recommended, as organic solvents such as
acetone, acids, or alcohol may compromise the sealing components of the apparatus.

ISO/DIS 20427:2025(en)
WARNING — Ignoring safety precautions and wrong handling or operation can cause serious or
minor injuries and damage to this apparatus or other properties.
WARNING — Do not operate the apparatus with the solvent boiling point exceeded. Blow-off of the
material or solvent caused by bumping or equipment damage caused by high-pressure steam can
injure the body.
See Annex D for an example of a detailed procedure of wet jet milling dispersion, as well as a detailed
description for energy estimation.
1)
6.3 Apparatus for shaker-based dispersion, such as Disperser DAS .
6.4 Analytical balance, accurate to the nearest 0,1 mg.
6.5 Beaker, based on the sonicator size, 50 ml to 300 ml tall-form.
6.6 Magnetic stirring device with stirrer bar
6.7 Syringes, 1 ml, 2 ml, 10 ml and 20 ml or better corresponding pipettes.
6.8 Cooled bath
6.9 Liquid sedimentation-based detection systems for particle size measurement
Table 1 and Table 2 show liquid sedimentation-based device examples for measuring instruments which are
available at the time of publication of this document.
Table 1 — Examples for currently available measuring instruments
Type Photo-centrifuge X-ray-centrifuge Analytical
ultra-centrifuge
Subtype Disc centrifuge Cuvette centrifuge Disc centrifuge Cuvette centrifuge
Wavelength 405 nm or 470 nm or Multiple wave- Data to be delivered Multiple wavelengths or
650 nm lengths from apparatus manu- xenon light
facturer
405 nm to 870 nm
−1 −1 −1
Acceleration range 600 min to 500 min to 600 min to (middle of cell)
−1 −1 −1
at the bottom 24 000 min 4 000 min 18 000 min −1
1 000 min to
5 times to −1
Not preferred: 60 000 min
2 300 times
Rotation speed
earth gravity
(at cell bottom)
Type of detection Light extinction Light extinction X-ray extinction versus Light extinction or
versus time versus time and time refractive index versus
position time
Sample volume 100 µl to 400 µl 100 µl to 2 000 µl 100 µl to 400 µl 350 µl to 400 µl
Typical sample con- 0,01 % to 10 % (vol- 0,01 % to 20 % (vol- 0,1 % to 30 % 0,01 % to 1 %
centration in volume ume fraction) ume fraction) (mass fraction)
Spin fluid volume 10 ml to 20 ml — 10 ml to 40 ml —
Number of samples 1 Up to 12 1 Up to 14
1) Disperser DAS is an example of a suitable product available commercially. This information is given for the convenience
of users of this document and does not constitute an endorsement by ISO of this product.

ISO/DIS 20427:2025(en)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Type Photo-centrifuge X-ray-centrifuge Analytical
ultra-centrifuge
Subtype Disc centrifuge Cuvette centrifuge Disc centrifuge Cuvette centrifuge
Sample containment Disc rotor Disposable or reusa- Disc rotor Re-usable cells
ble cells
Temperature control No 4 °C to 60 °C No 0 °C to 40 °C (±0,5 °C)
(±0,5 °C)
Range of particle 5 µm to 50 nm 500 µm to 50 nm 5 µm to 50 nm 800 nm to 2 nm
size
Table 2 — Examples for currently available measuring instruments
Type X Ray Cuvette sedi- Sedi-balance X-ray Cuvette sedi- CF3
mentation – mova- mentation
ble cuvette
Test methods in
ISO 13317-3 ISO 13317-4 ISO 13317-3 ISO/TS 21362
accordance with
−15
Wavelength / excita- O,138 nm / — 0,071 nm / 2,801·10 J Optical
−15
tion energy 1,442·10 J (9 keV) (17,48 keV)
multiple wavelengths
are available
−1 −1
Acceleration range at — — — 0 min to 12 000 min
the bottom
Not preferred:
Rotation speed
Type of detection X-ray extinction computational X-ray extinction versus Light scattering
versus time detection using a time and space STEP
UV-Vis absorption
commercial balance (space- and time-re-
Refractive index
solved extinction pro-
Fluorescence
files) Technology
ICP-MS
Sample volume 80 ml 1 l 0,2 ml to 1,6 ml 20 µl to 100 µl
a a a
Sample concen- 2,5 % mass fraction 2,5 % mass fraction 2 % mass fraction Dependent on the sam-
tration in mass or ples
volume, min.
Number of samples 1 1 1 1
Sample containment glass beaker sedimentation bath cuvette, different ma- Flow channel
terials
Temperature control Yes No No No
Range of particle 1 mm to 100 nm 1 mm to 5 µm 1 mm to 200 nm 40 µm to 10 nm
size
a
This value varies depending on the density since the detection is depending on the volume of the substance to be detected.
7 Settings for dispersion
7.1 Procedure of ultrasonic dispersion using a probe-type sonicator
Ultrasonic sources other than probe-type ones are not recommended and can lead to wrong results because
of the principal difficulties to calibrate the energy input.
The typical procedure is the following:
— fill beaker with a corresponding amount of water, depending on the size of the beaker;
— place beaker in the insulating foam;

ISO/DIS 20427:2025(en)
— put the ultrasonic probe and thermometer with short response-time in the water;
— the probe should be immersed in the same depth as later for dispersion;
— wait for thermal equilibration;
— the start temperature should be in defined, narrow range (e.g. between 20 °C and 25 °C);
— start ultrasonication.
It is important to keep the temperature constant. Cooling is recommended.
It is important to use the correct energy density to disintegrate the particulate sample. Setting the energy
density too low can lead to remaining agglomerates. If the energy density is too high, the piezo ceramic
sonicator can be destroyed and can contaminate the dispersion with nanoparticles. In addition, a destruction
of the particulate material can occur when using energies which are too high. In some cases, the treated
material can lose its pigmentary or extender properties when energy density treatments are too high.
The energy estimation shall be calculated in accordance with Annex A.
7.2 Procedure of ultrasonic dispersion using a bath-type sonicator
It is important to use the correct energy density to disintegrate the particulate sample. Setting the energy
too low can lead to remaining agglomerates. In addition, a destruction of the particulate material can occur
when using energies which are too high. In some cases, the treated material can lose its pigmentary or
extender properties at energy treatments which are too high.
Carry out an energy density estimation similar to the procedure for a probe-type sonicator specified in
Annex A. Consider the warming of the whole bath together with the beaker. For weak sonicators, enhance
the time of sonication until temperature changes are measurable.
The procedure is similar to the procedure of ultrasonic dispersion using a probe-type sonicator (7.1), except
that the beaker is put into an ultrasonic bath:
— weigh out 0,1 % to 1,0 % (mass fraction), depending on the type of pigment or extender, in a 50 ml to
300 ml tall-form beaker, depending on the size of the ultrasonic bath;
— fill the beaker with a corresponding amount of water, depending on the size of the beaker;
— place the beaker in a cooled bath to prevent heating above 40 °C. the upper limit of the temperature shall
be defined depending on the types of pigments or extenders;
— wait for thermal equilibration;
— the start temperature should be in defined, narrow range (e.g. between 20 °C and 25 °C);
— start ultrasonication.
It is important to always put the dispersion at the same position with the same amount of bath water to
ensure it remains reproducible and to maintain homogenous mixing inside the beaker.
7.3 Procedure of shaker-based dispersion
The typically used device (6.3) shakes small bottles filled with dispersion in a vertical direction. Typically,
between 1 and 30 bottles can be put into a bottle holder. They are fixed between a platform and a stamp
coming from above. During dispersion, the whole platform is shaken oscillatory in a vertical direction.
To enhance the dispersion properties, milling beads should be inserted into the bottles. Typically, the
effectivity of dispersion is correlated to the shaking speed, the volume percent of milling beads and the
particle sizes as well as to the material of the milling beads.

ISO/DIS 20427:2025(en)
The procedure is as follows:
— Take one 15 ml HDPE screw cap bottle and fill in the following dispersion: 12,475 ml dispersion having 5 %
to 20 % of particle volume concentration in aqueous solution together with the particle amount adapted
dispersant e.g. 5 g TiO in 7,475 g H O and 0,025 g hexametaphosphate (HMP) or other polyphosphate;
2 2
— add 28 g ZrO milling particles (0,5 mm);
— put the bottle into a shaker (6.3)
— select energy input to 60 W/(ml × min);
— shake the bottle for 5 min.
If the energy cannot be adjusted, measure energy input per minute and adapt the shaking time to 300 W/
(ml × s). A detailed description for the energy estimation is given in Annex A.
8 Dispersion procedure
8.1 General
The dispersion process is dependent on the operation time, power and dimension of dispersion devices. To
optimize the operation, it is recommended to find the operation level which achieves stable size distribution.
For appropriate dispersing of pigment and extender, the choice of the liquid phase and dispersant are also
critical.
8.2 Sampling for dispersion
Select pigment or extender samples from larger-sized lots at random, in either pelletized or non-pelletized
form, in accordance with ISO 15528. Label and retain samples for storage or further analysis.
8.3 Reagents
Unless stated otherwise, use only reagents of recognized reagent grade.
8.3.1 Water, distilled or deionized, quality 3 in accordance with ISO 3696.
The water shall be free of particles. To ensure this, filtration shall be used (e.g. membrane filter - cut-size
50 nm or smaller). Similar filtration shall also be used for any added additional solvents.
The liquids used shall not solve the particles to be measured.
If no data are available, the water shall be qualified by a blind test particle measurement in accordance with
this document.
8.3.2 Organic solvent, free of nanoparticles when measured in accordance with this document.
If no data are available, the solvent shall be qualified by a blind test particle measurement in accordance
with this document. If used, a blind measurement shall be performed in accordance with this document
using water, solvent and surfactant together in the planned concentrations.
The liquids used shall not solve the particles to be measured.
8.3.3 Surfactant, free of nanoparticles when measured in accordance with this document, in relation to
the surface properties of the pigment or extender particles.
If no data are available, the surfactant shall be qualifie
...