ISO 19613:2026

• Abstract:

  This document specifies a method for measurement of the viscosity of a ceramic slurry using a rotational viscometer. The method only involves rotations with a monotonic angle variation. This document does not apply to measurements using an oscillating rotation. Ceramic slurry is used in ceramic processes such as dip coating, spray coating, screen printing, slip casting, tape casting, spray drying and polishing. This document does not apply to dispersion of fillers in molten thermoplastic polymers.

• Status: Published
• Publication Date: 09-Sep-2026
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206/WG 2 - Powders
• Current Stage: 6060 - International Standard published
• Start Date: 10-Sep-2026
• Due Date: 13-Nov-2026
• Completion Date: 10-Sep-2026

• Revises: ISO 19613:2018 - Fine ceramics (advanced ceramics, advanced technical ceramics) — Measurement of viscosity of ceramic slurry by use of a rotational viscometer
• Effective Date: 18-Nov-2023

ISO 19613:2026 is an International Standard from ISO for measuring the viscosity of ceramic slurry with a rotational viscometer. It specifies how to measure slurry behavior under monotonic rotation, and it is written for users comparing ceramic slurries in production, development, and quality control. The document is especially relevant when slurry performance matters in dip coating, spray coating, screen printing, slip casting, tape casting, spray drying, or polishing.

What does ISO 19613:2026 specify?

ISO 19613:2026 specifies a method for measuring the viscosity of ceramic slurry using a rotational viscometer with monotonic angle variation. It excludes oscillating rotation, and it excludes dispersion of fillers in molten thermoplastic polymers.

The document is organized around the measurement principle, apparatus, calibration, measurement conditions, sample pretreatment, test procedures, result expression, and test reporting. The annexes describe the main measuring geometries and typical shear-rate ranges.

Annex	What it covers
Annex A	Coaxial double cylinder system
Annex B	Cone and plate system
Annex C	Parallel plate system
Annex D	Single cylinder viscometer
Annex E	Typical ranges of shear rate values

What are the key requirements of ISO 19613:2026?

ISO 19613:2026 requires the user to choose a measuring system that matches the slurry behavior and the comparison task. In practice, the document distinguishes between defined-shear-rate systems and the single cylinder viscometer, which gives an apparent viscosity and is useful for quicker comparison between samples.

Apparatus and geometry

Clause 5 states that the measuring system for defined shear rate shall use two rigid, symmetrical, coaxial surfaces, with one rotating and the other at rest. The instrument shall allow torque measurement and defined shear rate for each measurement. The apparatus shall meet the stated accuracy for torque, rotational frequency, and repeatability. This matters because the geometry and instrument performance affect whether results are comparable across samples and laboratories.

Clause 5 also explains the practical differences among the coaxial double cylinder, cone and plate, parallel plate, and single cylinder arrangements. The document warns that parallel plates do not provide homogeneous shear, so the geometry shall be reported and considered when comparing results.

Calibration and temperature control

Clause 6 requires periodic calibration, for example with reference liquids of known viscosity or by checking torque characteristics. Calibration liquids should be in the same viscosity range as the samples. Clause 5.4 requires temperature control and temperature measurement with stated accuracy, and Clause 7.1 states that comparison measurements shall be made at the same temperature. This matters because viscosity is temperature sensitive, so a small temperature difference can change the result.

Choosing measurement conditions

Clause 7 says the shear rate or angular velocity range shall be chosen with the requesting party, and for defined-shear-rate instruments it should match the intended application. Clause 7.3 requires viscosity to be measured at more than four defined shear rates to build a flow curve or viscosity curve, and the selected geometry gap shall be at least ten times the size of the largest particles. This helps avoid misleading results caused by particle size, poor geometry choice, or a range that is too narrow to show the slurry’s behavior.

Preparing the sample

Clause 8 requires conditioning at the measurement temperature before testing. If particles have settled, the slurry shall be dispersed by stirring, mixing, or shaking under controlled temperature conditions. Degassing is effective if bubbles are present, but the document treats it carefully because it can change the sample after preparation. In practice, the user has to prepare the slurry without creating bubbles or altering its structure.

Measurement procedure and fluid behavior

Clause 9 distinguishes between identifying fluid behavior and making control measurements at fixed settings. Clause 9.3 recommends first determining whether the slurry is shear thinning, shear thickening, thixotropic, Newtonian, or otherwise complex, because that choice affects the later control method. For sweeps, the document calls for increasing and then decreasing the shear rate or angular velocity without interruption, with stabilization time reported. This matters because a slurry may not have settled to equilibrium at low shear rate if the waiting time is too short.

Fixed-point testing and repeats

Clause 9.4 is for viscosity measurement at a fixed shear rate or angular velocity. The document requires at least three determinations for a fixed condition, each with a new portion of slurry, and the same parameter set should be used when comparing samples. The container, spindle, and any part in contact with slurry shall be cleaned between samples. In practice, this gives repeatable control data rather than a one-off reading.

Results and reporting

Clause 10 says to record the stabilized viscosity value, the test temperature, and the shear rate or angular velocity used. If the slurry shows different values on increasing and decreasing sweeps, the document provides for averaging and, for thixotropic slurries, recording both directions. Clause 11 lists the report items, including the viscometer type, geometry and spindle, sample identification, preparation details, stabilization time, torque if needed, and the flow or viscosity curve. This supports traceable reporting and comparison across batches.

What terms does ISO 19613:2026 define?

• Shear stress - stress acting on planes parallel to the direction of flow under laminar flow.
• Shear rate - the gradient of laminar flow rate perpendicular to the fluid flow.
• Viscosity - the ratio of shear stress to shear rate, used here as a measure of resistance to flow.
• Newtonian fluid - a fluid in which shear stress is proportional to shear rate, so viscosity remains constant with shear rate.
• Non-Newtonian fluid - a fluid in which shear stress is not proportional to shear rate, so viscosity changes with shear rate.
• Thixotropy - time-dependent behavior where apparent viscosity decreases under constant shear rate and recovers after the shear force is removed.
• Flow curve - a curve showing the relationship between shear rate and shear stress.
• Ceramic slurry - a suspension of grinding frit, clay, or ceramic powders in water or another liquid, including colloidal suspension, slip, and paste.

Who uses ISO 19613:2026?

ISO 19613:2026 is used by laboratories, process engineers, quality control teams, and materials suppliers working with fine ceramics and ceramic slurries. They use it to compare slurry batches, set measurement conditions for production control, and characterize how a slurry behaves during coating, casting, printing, drying, or polishing.

It is also relevant to buyers and technical evaluators who need a shared test method for supplier data. Because the document separates behavior mapping from fixed-point control measurements, it helps users decide whether a slurry is suitable for a specific process window.

What changed in ISO 19613:2026 from the previous edition?

ISO 19613:2026 cancels and replaces ISO 19613:2018. The foreword states that the second edition was technically revised.

The changes named in the document are:

• clarification added to the scope
• an added paragraph in the apparatus section on the use of different geometries
• an added paragraph in the measurement condition section on choosing the shear-rate range
• reorganization of the sample pretreatment section
• rewriting of the measurement procedure section to include identification of the fluid behavior

Which standards are used with ISO 19613:2026?

Standard	How it is used in ISO 19613:2026
ISO 20507	Provides the vocabulary for fine ceramics and is the only normative reference
ISO 2555	Cited in Annex D for LV, RV, and HA/HB single cylinder viscometer classes
ISO 80000-4	Cited in Clause 4 for symbol conventions
JIS Z 8803	Cited with the described measuring geometries in Clause 5

ISO 20507 is the formal reference that supplies shared terminology. The other standards and cited documents support geometry naming, symbols, or instrument classification.

What does the ISO 19613:2026 document contain?

ISO 19613:2026 contains a measurement principle for rotational viscometers, detailed apparatus guidance, calibration advice, measurement conditions, sample pretreatment, and step-by-step procedures for flow curves and fixed-point viscosity measurements. It also contains reporting requirements that make the test result traceable and comparable.

The annexes give practical detail on the coaxial double cylinder, cone and plate, parallel plate, and single cylinder systems, including their geometry and operating characteristics. Annex E adds typical shear-rate ranges for industrial processes such as storage, leveling, mixing, pumping, coating, printing, spraying, extrusion, and injection molding.

International
Standard
ISO 19613
Second edition
Fine ceramics (advanced ceramics,
2026-09
advanced technical ceramics) —
Measurement of viscosity of
ceramic slurry by use of a rotational
viscometer
Céramiques techniques — Mesure de la viscosité des céramiques
en suspension au moyen d'un viscosimètre rotatif
Reference number
© 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
4.1 Rotational viscometer with defined shear rate .3
4.2 Single cylinder viscometer .4
5 Apparatus . 4
5.1 General .4
5.2 Measuring system .4
5.2.1 General .4
5.2.2 Basic capacity of the instrument .4
5.2.3 Installation of rotational viscometer .4
5.3 Single cylinder viscometer. .5
5.3.1 Main body of single cylinder viscometer .5
5.3.2 Spindle .5
5.4 Temperature-control device. .5
5.4.1 Thermostat .5
5.4.2 Thermometer .5
6 Calibration of the rotational viscometer . 5
7 Measurement condition . 6
7.1 Temperature .6
7.2 Shear rate or angular velocity .6
7.3 Selection of geometry and/or spindle .6
8 Pretreatment of the sample . 6
8.1 Conditioning.6
8.2 Mixing .6
8.3 Degassing .7
9 Measurement procedures . 7
9.1 Sample loading . .7
9.2 Container sealing .7
9.3 Determination of a flow or viscosity curve .7
9.3.1 General .7
9.3.2 Measurement with a shear rate or angular velocity sweep . .7
9.3.3 Flow curve .8
9.3.4 Viscosity curve .8
9.4 Viscosity measurements .8
9.4.1 General .8
9.4.2 Measurement at fixed shear rate or angular velocity .8
9.4.3 Repeat and case of several measurements .9
10 Expression of the results . 9
11 Test report . 9
Annex A (informative) Coaxial double cylinder system . 10
Annex B (informative) Cone and plate system .13
Annex C (informative) Parallel plate system . 14
Annex D (informative) Single cylinder viscometer .16
Annex E (informative) Typical ranges of shear rate values . 19
Bibliography .20

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
This second edition cancels and replaces the first edition (ISO 19613:2018), which has been technically
revised.
The main changes are as follows:
— clarification added to the scope;
— paragraph addition in the Apparatus section on the use of different geometries;
— paragraph addition in the Measurement condition on the choice of the shear rate range;
— reorganisation of the Pretreatment of the sample section;
— rewriting the Measurement procedure section to include the identification of the fluid behaviour.
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 19613:2026(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Measurement of viscosity of ceramic slurry by
use of a rotational viscometer
1 Scope
This document specifies a method for measurement of the viscosity of a ceramic slurry using a rotational
viscometer. The method only involves rotations with a monotonic angle variation. This document does not
apply to measurements using an oscillating rotation.
Ceramic slurry is used in ceramic processes such as dip coating, spray coating, screen printing, slip casting,
tape casting, spray drying and polishing. This document does not apply to dispersion of fillers in molten
thermoplastic polymers.
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 20507, Fine ceramics (advanced ceramics, advanced technical ceramics) — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20507 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
shear stress
stress acting on planes parallel to the direction of flow when the fluid is subject to laminar flow
Note 1 to entry: The SI units are Pascal (Pa).
3.2
shear rate
gradient of laminar flow rate perpendicular to the fluid flow
−1
Note 1 to entry: The SI units are s .
3.3
viscosity
ratio of shear stress (3.1) to shear rate (3.2)
Note 1 to entry: This ratio is representative of the internal resistance of the fluid to flow.
Note 2 to entry: The SI unit of viscosity is Pa × s.
Note 3 to entry: mPa × s = 1 cP in terms of c.g.s. units [where 1P = 1 g/(cm × s)].

Note 4 to entry: Viscosity is sometimes called ‘dynamic viscosity’ or ‘shear viscosity’ for clarification. The measured
viscosity is conventionally called ‘apparent viscosity’ since the gradient of shear rate is not identical for all parts of the
spindle.
3.4
Newtonian fluid
fluid in which shear stress is proportional to shear rate
Note 1 to entry: The ratio of shear stress to shear rate is viscosity.
3.5
non-Newtonian fluid
fluid in which shear stress is not proportional to shear rate
Note 1 to entry: The non-Newtonian behaviour can be determined by measuring shear stress using varying shear rate
(or angular velocity). Viscosity of the non-Newtonian fluid changes with the shear rate, in contrast with Newtonian
fluid, which has constant viscosity with the shear rate.
3.6
thixotropy
flow behaviour of fluid that shows time dependence, such that the apparent viscosity decreases with time
for a constant shear rate, and recovers slowly with withdrawal of the shear force
3.7
shear thickening
increase of shear viscosity of fluid when the shear rate (or stress) is increased
3.8
shear thinning
decrease of shear viscosity of fluid when the shear rate (or stress) is increased
3.9
Bingham plastic
linear shear stress/shear rate relationship starting from a finite yield stress value below which the fluid
does not flow
Note 1 to entry: The linear relationship is usually valid on a limited rage of shear rate.
3.10
flow curve
curve showing the relationship between shear rate and shear stress
Note 1 to entry: See Figure 1 a).
3.11
viscosity curve
curve showing the relationship between shear rate (or shear stress) and viscosity
Note 1 to entry: See Figure 1 b).

a) Flow curve b) Viscosity curve
Key

γ shear rate
τ shear stress
η viscosity
1 Bingham plastic
2 shear thickening (dilatant)
3 newtonian
4 shear thinning (pseudoplastic)
5 thixotropy (time dependent)
Figure 1 — Summary of rheological behaviours
3.12
ceramic slurry
suspension of grinding frit, clay or ceramic powders mixed or dispersed in water or other liquid. It includes
colloidal suspension, slip and paste
Note 1 to entry: The category may include low-viscosity colloids with small particles with sizes in the nanometre or
micrometre range, and high-viscosity pastes with inhomogeneous mixtures.
4 Principle
4.1 Rotational viscometer with defined shear rate
The viscosity, η, of a ceramic slurry measured using a rotational viscometer with a defined shear rate is
determined using Formula (1):

  (1)


where
η is the viscosity, in Pa × s;
τ is the shear stress, in Pa;
−1

γ is the shear rate, in s .
NOTE Symbols are in accordance with ISO 80000-4.

4.2 Single cylinder viscometer
A spindle of cylindrical or disk-like shape is driven in the ceramic slurry at a fixed angular velocity. Torque
is developed from the fluid resistance, and it depends on the viscosity of the slurry. Theoretically, shear rate
(or shear stress) cannot be determined, but viscosity can be measured as a function of angular velocity.
NOTE The gradient of shear rate is not identical for all parts of the spindle. Therefore, the measurement result is
conventionally called apparent viscosity because it is not the viscosity determined from the gradient of a known shear
rate.
5 Apparatus
5.1 General
Rotational viscometers have various measuring geometries. Representative rotational viscometers having
a defined shear rate are a coaxial cylinder system (see Annex A), a cone and plate system (see Annex B), and
a parallel plates system (see Annex C). In contrast, single cylinder viscometers without a defined shear rate
(see Annex D) are able to give an apparent viscosity relatively quickly and reproducibly, and to provide a
comparison between samples.
Contrary to coaxial cylinder and cone and plate geometries, the shear is not homogeneous in a parallel plates
system. The nature of geometry shall be reported and taken into consideration when comparing different
sets of results. Rotational viscometer with defined shear rate
5.2 Measuring system
5.2.1 General
The measuring system shall consist of two rigid, symmetrical, coaxial surfaces between which the fluid
whose viscosity is to be measured is placed. One of these surfaces shall rotate while the other remains
at rest. The measuring system shall be such that the shear rate can be defined for each measurement. A
torque-measuring device shall be connected to one of the surfaces, thus permitting determination of the
torque required to overcome the viscous resistance of the fluid. Suitable measuring systems are the coaxial
double cylinder system (see Annex A), cone and plate system (see Annex B), and parallel plate system (see
Annex C), as prescribed by JIS 8803 and ISO 20507. The dimensions of each measuring system are detailed
in Annexes A, B, and C, which are designed to ensure a geometrically similar flow field for all types of
measurement and all common types of basic instrument.
5.2.2 Basic capacity of the instrument
The basic instrument shall be designed to permit alternative rotors and stators to be fitted, for the generation
of a range of defined rotational frequencies (stepwise or continuously variable), and for measuring the
resulting torque, or vice versa (i.e. measurement of the necessary angular velocity to generate a defined
torque). The apparatus shall have a torque-measurement accuracy of 2 % of the full-scale reading. Within
the regular working range of the instrument, the accuracy of rotational-frequency measurement shall be
2 % of the measured value. The repeatability of viscosity measurement shall be ±2 %.
NOTE By using different measuring systems and rotational frequencies, most commercial instruments cover a
−2 3
viscosity range of at least 10 Pa × s to 10 Pa × s.
5.2.3 Installation of rotational viscometer
5.2.3.1 Coaxial double cylinder viscometer
a) The axis of rotation of the viscometer is installed vertically.
b) The surface of the sample is maintained at a lower position than the surface of the thermostat or the top
of the liquid jacket in the outer cylinder.

c) The inner cylinder is placed with its axis coinciding with the axis of the outer cylinder; the distance
from the bottom of the inner cylinder to the bottom of the outer cylinder is more than 5 mm. The upper
surface of the inner cylinder is more than 5 mm below the surface of the sample.
5.2.3.2 Cone and plate viscometer
a) The axis of rotation of the viscometer is installed vertically, and the plate horizontally.
b) The surface of the sample is maintained at a lower position than the surface of the thermostat or the top
of the liquid jacket in cone and plate.
c) The cone is adjusted so its tip lies on the axis of rotation, and the centre of the parallel plate is also
positioned on the axis.
NOTE The tip of the cone can cause friction if it is in contact with the plate. The tip means the imaginary tip of the
cone obtained by extrapolation if the end is cut flat.
5.3 Single cylinder viscometer.
The single cylinder viscometer has two main components relevant to this standard.
5.3.1 Main body of single cylinder viscometer
It is necessary to select the proper model of viscometer for the viscosity to be measured, each model being
suited to a specific range of viscosities. Brookfield provides single cylinder viscometers that are classified
as LV (low viscosity), RV (medium viscosity) and HA/HB (high viscosity), as prescribed in ISO 2555. Other
manufacturers also provide equivalent systems. The suitable uses of cylinder-type viscometers are also
determined by special spindles such as Krebs or vane types. Some single cylinder viscometers do not have a
demarcation point between the body/shaft and spindle to define the amount of rotating surface submersed,
so the shear rate is not fully determined in that case.
5.3.2 Spindle
Do not use spindles that are corroded or show eccentric rotation. Choose the spindle taking into account the
value of viscosity to be measured, based on the model of viscometer and angular velocity. It is preferable to
use the same spindle to compare samples, even when the measured value is outside the spindle’s optimum
range, rather than change spindles and rely on instrument accuracy. For an unknown sample without any
prior information, choose the proper exchangeable spindle that gives a proper magnitude of torque when
tested through the full range of angular velocity.
5.4 Temperature-control device.
5.4.1 Thermostat
The circulation temperature of a constant temperature bath or electric heated wall temperature of a
constant temperature bath shall be maintained within ±0,2 °C for temperatures between 0 and 50 °C. Wider
tolerances (e.g. ±0,4 °C) are often sufficient outside this temperature range. Closer tolerances (e.g. ±0,1 °C)
may be necessary for precise measurements.
5.4.2 Thermometer
The accuracy of the thermometer shall be ±0,2 °C or the apparatus shall contain a device to measure
temperature with equivalent accuracy.
6 Calibration of the rotational viscometer
Viscometers shall be calibrated periodically, e.g. by measuring the torque characteristics or by using
reference liquids of known viscosity (Newtonian fluids). Standard pre-mixed liquids are preferable to

the use of distilled wat
...