SIST EN ISO 20427:2026

SLOVENSKI STANDARD
01-junij-2026
Nadomešča:
SIST EN ISO 20427:2025
Pigmenti in polnila - Postopek disperzije za določanje porazdelitve velikosti delcev
na podlagi sedimentacije suspendiranih pigmentov ali polnil v tekoči fazi (ISO
20427:2026)
Pigments and extenders - Dispersion procedure for sedimentation-based particle sizing
of suspended pigment or extender with liquid sedimentation methods (ISO 20427:2026)
Pigmente und Füllstoffe - Dispergierverfahren zur sedimentativen
Teilchengrößenbestimmung von suspendierten Pigmenten oder Füllstoffen mit
Flüssigsedimentationsverfahren (ISO 20427:2026)
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 20427:2026)
Ta slovenski standard je istoveten z: EN ISO 20427:2026
ICS:
87.060.10 Pigmenti in polnila Pigments and extenders
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 20427
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2026
EUROPÄISCHE NORM
ICS 87.060.10 Supersedes EN ISO 20427:2024
English Version
Pigments and extenders - Dispersion procedure for
sedimentation-based particle sizing of suspended pigment
or extender with liquid sedimentation methods (ISO
20427:2026)
Pigments et matières de charge - Mode opératoire de Pigmente und Füllstoffe - Dispergierverfahren zur
dispersion pour la détermination granulométrique sedimentativen Teilchengrößenbestimmung von
basée sur la sédimentation des pigments ou matières suspendierten Pigmenten oder Füllstoffen mit
de charge en suspension par des méthodes de Flüssigsedimentationsverfahren (ISO 20427:2026)
sédimentation dans un liquide (ISO 20427:2026)
This European Standard was approved by CEN on 30 August 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20427:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 20427:2026) has been prepared by Technical Committee ISO/TC 256
"Pigments, dyestuffs and extenders" in collaboration with Technical Committee CEN/TC 298 “Pigments
and extenders” the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by September 2026, and conflicting national standards
shall be withdrawn at the latest by September 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 20427:2024.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 20427:2026 has been approved by CEN as EN ISO 20427:2026 without any modification.

International
Standard
ISO 20427
Second edition
Pigments and extenders —
2026-03
Dispersion procedure for
sedimentation-based particle sizing
of suspended pigment or extender
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
Reference number
ISO 20427:2026(en) © ISO 2026
ISO 20427:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 20427:2026(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 Principles of wet jet mill dispersion .3
4.3 Principles 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
7 Settings for dispersion . 9
7.1 Procedure of ultrasonic dispersion using a probe-type sonicator .9
7.2 Procedure of ultrasonic dispersion using a bath-type sonicator .9
7.3 Procedure of shaker-based dispersion .10
8 Dispersion procedure . 10
8.1 General .10
8.2 Sampling for dispersion.10
8.3 Reagents .10
8.4 Recommendations for sample preparation.11
9 Sampling .11
10 Measurement and expression of results .11
11 Test report .11
Annex A (normative) Protocol for the determination of energy input .13
Annex B (informative) Limits for ultrasonic dispersion procedure .16
Annex C (informative) Procedures for dispersion of TiO pigments . 17
Annex D (informative) Procedure for dispersion of CaCO with wet jet milling .18
Annex E (informative) Procedure for the dispersion of Fe O with an ultrasonic probe . 19
2 3
Annex F (informative) General procedure for dispersion of pigment or extender .20
Bibliography .23

iii
ISO 20427:2026(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 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 second edition cancels and replaces the first edition (ISO 20427:2023), which has been technically
revised.
The main changes are as follows:
— in 5.5, a note has been added with additional information on the effective particle density;
— in 6.9 the original Tables 1 and Table 2 have been combined in one single table;
— in 6.9, Table 1, row 7, columns 6 to 8, a table footnote has been added explaining the density dependency
of these values;
— in 6.9, Table 1, row 10, column 7, “class cylinder beaker” has been changed to “sedimentation bath”;
— in Clause 10, a note has been added with a mathematical definition of precision;
— 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 F.2 and F.3, notes have been added to explain why a temperature of 40 °C is important, and 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.

iv
International Standard ISO 20427:2026(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, Determination of particle size distribution by centrifugal liquid sedimentation methods — Part 1:
General principles, requirements and guidance
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 20427:2026(en)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in the ISO 18451 series 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 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.
[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 20427:2026(en)
3.5
primary particle
single nano-object with at least one of three external dimensions at the nanoscale (3.1)
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 to 80 kHz or 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 shall 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 Principles 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 works 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 Principles of shaker-based dispersion
The shaker device shall be built like a plate with holders for the high-density polyethylene (HDPE) bottles
in accordance with A.2. 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.
The following aspects should be considered:
— inclusion of grinding beads, high loading;

ISO 20427:2026(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 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 or 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
— the 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, it is challenging to achieve a resolution below 1 µm 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 according to ISO 13317-1 and ISO 13317-3 is included in this
document.
ISO 20427:2026(en)
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
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 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 centrifugal field-flow fractionation, 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 either online detectors or a fraction collector for off-line
analysis, or both. Common detectors used for analysis of the 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 21362.
6 Apparatus
Use standard laboratory apparatus, together with the following.
6.1 Apparatus for ultrasonic dispersion:
a) 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 shall be held as low as possible, around typical room temperature, in order to
maintain conditions for good stability of the dispersing agents.
b) 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, 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 shall 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,

ISO 20427:2026(en)
water is generally recommended, as organic solvents such as acetone, acids, or alcohol can compromise the
sealing components of the apparatus.
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 shows examples of liquid sedimentation-based devices that can be used as measuring instruments,
which are available at the time of publication of this document.
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 20427:2026(en)
Table 1 — Examples of liquid sedimentation-based devices
Type Photo-centrifuge X-ray-centrifuge Analytical X Ray Cuvette Sedimentation X-ray Filed-flow
ultra- sedimentation – balance Cuvette fractional
centrifuge movable cuvette analysis sedimenta- device
tion
Subtype/ Disc centri- Cuvette centri- Disc centrifuge Cuvette cen- ISO 13317-3 ISO 13317-4 ISO 13317-3 ISO 21362
Standard fuge fuge trifuge
Wavelength/ex- 405 nm or Multiple wave- Data to be delivered Multiple 0,138 nm / — 0,071 nm / Optical
−15 −15
citation energy 470 nm or lengths from apparatus wavelengths or 1,442·10 J 2,801·10 J
multiple wave-
650 nm manufacturer xenon light (9 keV) (17,48 keV)
405 nm to lengths are
870 nm available
−1 −1 −1 −1
Acceleration range 600 min to 500 min to 600 min to (Middle of cell) — — — 0 min to
−1 −1 −1 −1
−1
at the bottom 24 000 min 4 000 min 18 000 min 12 000 min
1 000 min to
−1
5 times to
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 Light extinc- X-ray extinction Computational X-ray extinc- Light scattering
versus time versus time and versus time tion or re- versus time detection using tion versus
UV-Vis absorp-
position fractive index a commercial time and
tion
versus time balance space STEP
Refractive
(space- and
index
time-resolved
Fluorescence
extinction
ICP-MS
profiles)
Technology
Sample volume 100 µl to 400 µl 100 µl to 100 µl to 400 µl 350 µl to 80 ml 1 l 0,2 ml to 20 µl to 100 µl
2 000 µl 400 µl 1,6 ml
Sample concen- 0,01 % to 10 % 0,01 % to 20 % 0,1 % to 30 % 0,01 % to 1 % Min. 2,5 % Min. 2,5 % Min. 2 % Dependent on
a a
tration in mass or (volume frac- (volume frac- (mass fraction) (mass fraction) (mass fraction) (mass frac- the samples
a
volume tion) tion) tion)
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 1 1 1
a
This value varies depending on the density since the detection depends on the volume of the substance to be detected.

ISO 20427:2026(en)
Table 1 (continued)
Type Photo-centrifuge X-ray-centrifuge Analytical X Ray Cuvette Sedimentation X-ray Filed-flow
ultra- sedimentation – balance Cuvette fractional
centrifuge movable cuvette analysis sedimenta- device
tion
Subtype/ Disc centri- Cuvette centri- Disc centrifuge Cuvette cen- ISO 13317-3 ISO 13317-4 ISO 13317-3 ISO 21362
Standard fuge fuge trifuge
Sample contain- Disc rotor Disposable or Disc rotor Re-usable cells Glass beaker Sedimentation Cuvette, Flow channel
ment reusable cells bath different
materials
Temperature No 4 °C to 60 °C No 0 °C to 40 °C Yes No No No
control (±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 1 mm to 100 nm 1 mm to 5 µm 1 mm to 40 µm to 10 nm
size 2 nm 200 nm
a
This value varies depending on the density since the detection depends on the volume of the substance to be detected.

ISO 20427:2026(en)
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;
— put the ultrasonic probe and thermometer with short response-time in the water;
— the probe shall be immersed in the same depth as later for dispersion;
— wait for thermal equilibration;
— the start temperature shall be in defined, narrow range (e.g. between 20 °C and 25 °C);
— start ultrasonication.
The temperature shall be kept constant. Cooling is recommended.
The correct energy density shall be used 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, i.e. particles in the nanoscale. 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.
For estimating the limits for ultrasonic dispersion procedure, see Annex B.
7.2 Procedure of ultrasonic dispersion using a bath-type sonicator
The correct energy density shall be used 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;

ISO 20427:2026(en)
— the start temperature shall 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.
For estimating the limits for ultrasonic dispersion procedure, see Annex B.
7.3 Procedure of shaker-based dispersion
Typically, the device specified in 6.3 is used to shake 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 shall be inserted into the bottles. 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.
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 the dispersion
devices. To optimize the operation, it is recommended to find the operation level which achieves stable size
distribution. For appropriate dispersing of the 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 en
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