SIST EN ISO 14705:2026

• Abstract:

  This document specifies a test method for determining the Vickers and Knoop hardness of monolithic fine ceramics at room temperature.

• Status: Published
• Public Enquiry End Date: 19-Nov-2025
• Publication Date: 20-Oct-2026
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 19-Oct-2026
• Due Date: 24-Dec-2026
• Completion Date: 21-Oct-2026
• Ref Project: EN ISO 14705:2026 - Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for hardness of monolithic ceramics at room temperature (ISO 14705:2026)

• Revised: SIST EN ISO 14705:2021 - Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for hardness of monolithic ceramics at room temperature (ISO 14705:2016)
• Effective Date: 19-Jan-2023

SIST EN ISO 14705:2026 specifies a room-temperature test method for determining the Vickers and Knoop hardness of monolithic fine ceramics. It is the ISO-based document used when a consistent hardness value is needed for advanced ceramics, using either the Vickers or Knoop indentation method.

What does SIST EN ISO 14705:2026 specify?

SIST EN ISO 14705:2026 covers a test method for monolithic fine ceramics at room temperature, with two separate parts for Vickers hardness and Knoop hardness. The document tells users how to prepare the test piece, set up the apparatus, make and assess indentations, calculate hardness, and report the result.

The document is organized into:

• Clause 1 - Scope
• Clause 2 - Normative references
• Clause 3 - Terms and definitions
• Clause 4 - Vickers hardness
• Clause 5 - Knoop hardness
• Bibliography

Clauses 4 and 5 follow the same pattern, so users can apply the same general approach to either hardness scale while respecting the different indenter shape, force range, spacing rules and calculation details.

What are the key requirements of SIST EN ISO 14705:2026?

SIST EN ISO 14705:2026 is built around two indentation methods, and the practical requirements are mostly about keeping the indentation and measurement conditions controlled. The document is explicit about force, surface preparation, optical measurement and when a result has to be rejected.

• Clauses 4.1 and 5.1 - test principle
  A diamond indenter is pressed into the ceramic surface, and hardness is calculated from the indentation size after the force is removed. For Vickers hardness, the two diagonals are measured; for Knoop hardness, only the long diagonal is measured. In practice, this means the lab needs an optical system that can measure tiny indentation dimensions reliably.

• Clauses 4.4 and 5.4 - apparatus and verification
  The testing machine, diamond indenter and diagonal measuring system must be suitable for the chosen method and verified according to the referenced ISO 6507 or ISO 4545 parts. The document also gives measurement-resolution requirements and recommends microscope optics with a numerical aperture in a defined range. This matters because weak optics or poor calibration can change the reported hardness.

• Clauses 4.5 and 5.5 - test piece preparation
  The test surface must be smooth, flat, clean and polished so the diagonal can be measured accurately, and surface-hardness alteration should be minimized. Thermal or chemical etching is not allowed, and residual surface stress should be removed when relevant. For Vickers testing, the piece must also be thick enough relative to indentation size and crack length. In practice, sample preparation is part of the test, not just a pre-step.

• Clauses 4.6 and 5.6 - temperature, force and procedure
  Tests are run at room temperature, with controlled testing at 23 °C ± 5 °C. The document gives preferred test forces and allows other forces in defined ranges when cracking, weak impressions or coarse microstructure make that necessary. The force must be applied smoothly, without shock or vibration, and held for the specified dwell time. This is important for repeatable results on brittle ceramics.

• Clauses 4.6.9 to 4.6.13 and 5.6.9 to 5.6.13 - spacing and validity of indentations
  Indentations must be kept away from edges and from each other, and the document gives spacing rules for each method. Indentations are rejected if they show excessive cracking, pore interference, asymmetry beyond the stated limit, or other signs that the measurement would be unreliable. At least five valid indentations are needed to obtain a mean result.

• Clauses 4.6.14 and 5.6.14 - calculation and expression of results
  Hardness is calculated for each valid indentation, then averaged and accompanied by the standard deviation (SD). Results are expressed with three significant digits. The document also points to hardness-value tables in the relevant ISO 6507 or ISO 4545 parts for flat surfaces.

• Clauses 4.7 and 5.7 - accuracy and uncertainty
  The document warns that small indentations, poor optical contrast, surface finish and local microstructure can increase measurement error. It also notes that higher forces can improve discrimination if the indentation quality remains acceptable. For practical use, this means the best force is not always the lowest or highest one, but the one that gives a clear, measurable indentation without damage.

What terms does SIST EN ISO 14705:2026 define?

• Vickers hardness - The hardness value obtained from the applied force divided by the indentation surface area, using the mean of the two diagonals.
• Vickers indenter - A diamond pyramid with a square base and the defined angle between opposite faces used for Vickers testing.
• Knoop hardness - The hardness value obtained from the applied force divided by the projected indentation area, using the long diagonal.
• Knoop indenter - A diamond pyramid with a rhombic base and the defined edge angles used for Knoop testing.
• HV - The symbol for Vickers hardness, written after the hardness value and followed by the test force designation.
• HK - The symbol for Knoop hardness, written after the hardness value and followed by the test force designation.
• SD - Standard deviation, used to show the scatter of repeated hardness values.

Who uses SIST EN ISO 14705:2026?

SIST EN ISO 14705:2026 is used by laboratories, ceramic manufacturers, quality managers, technical buyers and test houses that need a standardized hardness result for monolithic fine ceramics. It is relevant in product qualification, incoming inspection, process control, comparative material testing and reporting results to customers or certification schemes.

It is also useful when an organization needs to document test conditions carefully, because the standard requires information on surface preparation, test force, temperature, number of valid indentations and any factor that may have affected the result.

What changed in SIST EN ISO 14705:2026 from the previous edition?

SIST EN ISO 14705:2026 is the fourth edition and it cancels and replaces ISO 14705:2016. The document states that it has been technically revised.

The main changes identified in the document are:

• clarification of the required resolution of the diagonal measuring system in clauses 4.4.3 and 5.4.3
• modification of the required measurement accuracy in clauses 4.6.12 and 5.6.12

Which standards are used with SIST EN ISO 14705:2026?

The document relies on these referenced standards:

• ISO 4545-1 - Knoop hardness test method for metallic materials, used as the basis for the Knoop indenter and test method details.
• ISO 4545-2 - Verification and calibration of Knoop testing machines, used for force verification, indenter verification and measuring-device verification.
• ISO 4545-4 - Table of hardness values for Knoop testing, used when hardness values are needed for flat surfaces.
• ISO 6507-1 - Vickers hardness test method for metallic materials, used as the basis for the Vickers indenter and test method details.
• ISO 6507-2 - Verification and calibration of Vickers testing machines, used for force verification, indenter verification and measuring-device verification.

The document also points to ISO 4545-3 and ISO 6507-3 for calibrated reference blocks used in indirect verification, and to ISO 6507-4 for Vickers hardness values on flat surfaces.

What does the SIST EN ISO 14705:2026 document contain?

SIST EN ISO 14705:2026 contains two full test methods, each with a principle, symbols, significance and use, apparatus, test-piece requirements, procedure, accuracy discussion and test-report content. It includes tables for test-force symbols and nominal forces, plus tables for measuring-system resolution.

The document also includes figures showing the Vickers and Knoop indenters, the indentation shapes, acceptable and unacceptable impressions, edge-distance and spacing rules, and crosshair measurement guidance. These figures are there to help users measure the diagonals consistently and decide when an indentation should be rejected.

The text provides calculation formulas for Vickers hardness and Knoop hardness, as well as examples of how to write the hardness result with the force designation. This is useful for test reports, audits and comparison of results between laboratories.

SLOVENSKI STANDARD
01-december-2026
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Preskus trdote za
monolitno keramiko pri sobni temperaturi (ISO 14705:2026)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for
hardness of monolithic ceramics at room temperature (ISO 14705:2026)
Hochleistungskeramik - Prüfverfahren für die Härte von monolithischer Keramik bei
Raumtemperatur (ISO 14705:2026)
Céramiques techniques - Méthode d'essai de dureté des céramiques monolithiques à
température ambiante (ISO 14705:2026)
Ta slovenski standard je istoveten z: EN ISO 14705:2026
ICS:
81.060.30 Sodobna keramika Advanced ceramics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 14705
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2026
EUROPÄISCHE NORM
ICS 81.060.30 Supersedes EN ISO 14705:2021
English Version
Fine ceramics (advanced ceramics, advanced technical
ceramics) - Test method for hardness of monolithic
ceramics at room temperature (ISO 14705:2026)
Céramiques techniques - Méthodes d'essai de dureté Hochleistungskeramik - Prüfverfahren für die Härte
des céramiques monolithiques à température ambiante von monolithischer Keramik bei Raumtemperatur (ISO
(ISO 14705:2026) 14705:2026)
This European Standard was approved by CEN on 2 January 2026.

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 14705:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 14705:2026) has been prepared by Technical Committee ISO/TC 206 "Fine
ceramics" in collaboration with Technical Committee CEN/TC 184 “Advanced technical ceramics” 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 April 2027, and conflicting national standards shall be
withdrawn at the latest by April 2027.
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 14705:2021.
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 14705:2026 has been approved by CEN as EN ISO 14705:2026 without any modification.

International
Standard
ISO 14705
Fourth edition
Fine ceramics (advanced ceramics,
2026-09
advanced technical ceramics) —
Test method for hardness of
monolithic ceramics at room
temperature
Céramiques techniques — Méthodes d’essai de dureté des
céramiques monolithiques à température ambiante
Reference number
ISO 14705:2026(en) © ISO 2026
ISO 14705:2026(en)
© ISO 2026
All rights reserved.
This ISO publication is protected by copyright and is owned by ISO and/or its licensors.
The content of this ISO publication is provided under licence, not sold. Use is subject to the applicable licence terms issued by ISO,
an ISO member body, or an authorized third-party distributor.
Except as required for implementation or expressly permitted by a separate licence, no part of this ISO publication may be
reproduced, distributed, modified, used, or made available in any form or by any means – electronic or mechanical, including
photocopying, scanning, recording, or posting on internal or external digital platforms.
Any use beyond the scope of the granted rights is prohibited and may result in legal action.
ISO copyright office
CP 401 • CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 14705:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Vickers hardness . 2
4.1 Principle .2
4.2 Symbols, abbreviated terms and designations .2
4.3 Significance and use .4
4.4 Apparatus .4
4.5 Test pieces .5
4.6 Procedure .5
4.7 Accuracy and uncertainties .8
4.8 Test report .8
5 Knoop hardness .12
5.1 Principle . 12
5.2 Symbols, abbreviated terms and designations . 12
5.3 Significance and use .14
5.4 Apparatus .14
5.5 Test pieces . . 15
5.6 Procedure . 15
5.7 Accuracy and uncertainty .16
5.8 Test report .17
Bibliography .21

iii
ISO 14705:2026(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 206, Fine ceramics, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 184, Advanced technical
ceramics, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna
Agreement).
This fourth edition cancels and replaces the third edition (ISO 14705:2016), which has been technically
revised.
The main changes are as follows:
— clarification of the required resolution of the diagonal measuring system (4.4.3 and 5.4.3);
— modification of the required measurement accuracy (4.6.12 and 5.6.12).
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 14705:2026(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for hardness of monolithic ceramics
at room temperature
1 Scope
This document specifies a test method for determining the Vickers and Knoop hardness of monolithic fine
ceramics at room temperature.
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 4545-1, Metallic materials — Knoop hardness test — Part 1: Test method
ISO 4545-2, Metallic materials — Knoop hardness test — Part 2: Verification and calibration of testing machines
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 6507-2, Metallic materials — Vickers hardness test — Part 2: Verification and calibration of testing machines
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
Vickers hardness
value obtained by dividing the applied force by the projected area of the indentation, calculated from the
arithmetic mean of the measured diagonals of the indentations, assuming that the indentation is a permanent
imprint of the undeformed indenter
Note 1 to entry: Vickers hardness may be expressed either
a) with units of GPa, obtained by dividing the applied force in N by the projected area of the indentation in mm ,
or
b) as a dimensionless Vickers hardness number, obtained by dividing the applied force in N by a scaling
factor corresponding to the standard gravity (9,806 65 m/s ) and by the projected area of the
indentation in mm .
Note 2 to entry: The scaling factor ensures that the resulting dimensionless value is numerically identical to legacy
calculations historically expressed in kgf/mm .

ISO 14705:2026(en)
3.2
Vickers indenter
indenter in the shape of a right-angle pyramid with a square base and an angle between opposite faces of
136°
Note 1 to entry: See Table 1 and Figure 1.
3.3
Knoop hardness
value obtained by dividing the applied force by the projected area of the indentation, calculated from the
measured long diagonal of the indentation, assuming that the indentation is a permanent imprint of the
undeformed indenter
Note 1 to entry: The Knoop hardness may be expressed either
a) with units of GPa, obtained by dividing the applied force in N by the projected area of the indentation in mm ,
or
b) as a dimensionless Knoop hardness number, obtained by dividing the applied force in N by a scaling
factor corresponding to the standard gravity (9,806 65 m/s ) and by the projected area of the
indentation in mm .
Note 2 to entry: The scaling factor ensures that the resulting dimensionless value is numerically identical to legacy
calculations historically expressed in kgf/mm .
3.4
Knoop indenter
indenter in the shape of a rhombic-based pyramid with the two angles between the opposite edges at 172,5°
and 130°
Note 1 to entry: See Table 3 and Figure 6.
4 Vickers hardness
4.1 Principle
Forcing a diamond indenter in the form of a right-angle pyramid with a square base, and with a specified
angle between opposite faces at the vertex into the surface of a test piece and measuring the length of the
diagonals of the indentation left in the surface after removal of the test force, F. See Figure 1 and Figure 2.
4.2 Symbols, abbreviated terms and designations
4.2.1 See Table 1, Figure 1 and Figure 2.
4.2.2 The Vickers hardness is expressed either as a physical unit of pressure (GPa) or as a conventional,
dimensionless hardness number.
When using SI unit (GPa), the hardness value is denoted by the unit symbol GPa, followed by the designation
HV and a value representing the exact test force in Newtons (N)
EXAMPLE 1 15,0 GPa HV 9,807 N represents a Vickers hardness of 15,0 GPa, determined with a test force of 9,807 N.
When using the dimensionless Vickers hardness number, the value is denoted by the symbol HV, preceded by the
hardness value and followed by a force indicator number representing the nominal test force (see Table 2).
EXAMPLE 2 1 500 HV 1 represents a Vickers hardness number of 1 500, determined with a test force indicator of 1
(corresponding to a nominal test force of 9,807 N).

ISO 14705:2026(en)
Table 1 — Symbols, abbreviated terms and designations for Vickers hardness testing
Symbol or
abbreviated Designation
term
α Angle between the opposite faces at the vertex of the pyramidal indenter (136° ± 0,5°)
F Test force, in newtons
d Arithmetic mean, in millimetres, of the two diagonals, d and d
1 2
HV Vickers hardness
Test force
Constant
Surfaceareaofindentation
a) Units of GPa
136
2F sin
F
 0,001  0,001854
d d
b) Hardness number (no units specified)

136 136
2F sin 2F sin
1 F
2 2
   0,10197  0,1891
22 2
g
d d d
c Arithmetic mean of the half of the two median crack lengths, 2c and 2c
1 2
SD Standard deviation
HV HV

n

n 1
where
HV

n
HV is the arithmetic mean of the Vickers hardness  ;
n
HV is the HV obtained from nth indentation;
n
n is the number of indentations.
NOTE The scaling constant 0,10197 , where g is the acceleration of gravity is a historical mathematical
g 9,80665
wrapper ensuring that the resulting hardness number remains numerically identical to legacy engineering records previously
calculated in kgf/mm .
Table 2 — Hardness symbols and the nominal values of test forces, F, for Vickers hardness testing
Test force, F
Hardness symbol
(nominal value)
HV 0,5 4,903 N
HV 1 9,807 N
HV 2 19,61 N
HV 3 29,42 N
HV 5 49,03 N
HV 10 98,07 N
HV 20 196,1 N
==
ISO 14705:2026(en)
Figure 1 — Vickers indenter (diamond pyramid)
Figure 2 — Vickers indentation
4.3 Significance and use
Vickers indentation diagonal lengths are approximately 2,8 times shorter than the long diagonal of Knoop
indentations, and the indentation depth is approximately 1,5 times deeper than Knoop indentations made
at the same force. Vickers indentations are influenced less by the specimen surface flatness, parallelism of
the diamond axis to the test piece surface normal, and surface finish than Knoop indentations, but these
parameters should be considered, nonetheless. Vickers indentations are much more likely to cause cracks in
fine ceramics than Knoop indentations. Conversion between hardness scales shall not be made.
Vickers indentations on metallic materials are mainly formed by the plastic deformation. However, Vickers
indentations on fine ceramics are formed by micro-cracking and micro-fracture, besides plastic deformation.
This difference shall be noted for comparing the hardness of metals and ceramics.
4.4 Apparatus
4.4.1 Testing machine, capable of applying a predetermined test force in the range of 4,903 N to 98,07 N,
preferably 9,807 N, in accordance with ISO 6507-2. Verification of the test force shall be carried out in
accordance with ISO 6507-2.
ISO 14705:2026(en)
4.4.2 Diamond indenter, in the shape of a right-angle pyramid with a square base, in accordance with
ISO 6507-1 and ISO 6507-2. Verification of the indenter shall be carried out in accordance with ISO 6507-2.
4.4.3 Diagonal measuring system. Magnifications should be provided so that the diagonal can be
enlarged to greater than 25 % but less than 75 % of the maximum possible optical field of view as many
objective lenses are nonlinear towards the edge of the field of view.
The resolution required of the diagonal measuring system depends on the size of the smallest indentation
to be measured and shall be in accordance with Table 3. In determining the resolution of the measuring
system, the resolution of the microscope optics, the digital resolution of the measuring scale and the step-
size of any stage movement, where applicable, should be taken into account.
Table 3 — Resolution of the measuring system
Diagonal length, d
Resolution of the measuring sys-
Maximum permissible error
tem
mm
d < 0,050 0,000 25 mm 0,000 5 mm
0,050 ≤ d 0,5 % of d 1 % of d
A numerical aperture (NA) between 0,60 and 0,95 for the objective lens for the microscope is recommended.
NOTE 1 The apparent length of a Vickers indentation increases as the resolving power and NA of a lens increases.
The range of NA specified by this test method corresponds to 40 to 100× objective lenses. The higher power lenses can
have higher resolution, but the contrast between the indentation tips and the polished surface can be lower.
Verification of the measuring device shall be carried out in accordance with ISO 6507-2.
NOTE 2 Indirect verification can be carried out by means of standardized blocks calibrated in accordance with
ISO 6507-3, following ISO 6507-2, or other approved and traceable ceramic standard reference blocks.
4.5 Test pieces
4.5.1 The test shall be carried out on a surface which is smooth, flat and free from foreign matter. The
test piece shall be polished to permit accurate measurement of the diagonal lengths of the indentation.
Preparation shall be carried out in such a way that any alteration of the surface hardness is minimized.
Surfaces shall not be thermally or chemically etched. If applicable, residual surface stresses shall be removed
by suitable polishing or annealing procedures.
4.5.2 The thickness of the test piece shall be at least 1,5 times the diagonal of the indentation, d, at least
2 times the crack length, c, and at least 0,5 mm, whichever is greater. No indentation damage shall be visible
at the back of the test piece upon completion of the test.
4.6 Procedure
4.6.1 In general, the test shall be carried out at room temperature within the limits of 10 °C to 35 °C. Tests
carried out under controlled conditions shall be made at a temperature of 23 °C ± 5 °C.
4.6.2 The test force shall be 9,807 N. In cases where significant chipping or lateral crack-spalling occurs
or where the impression is too faint, the test forces within the range 4,903 N to 196,1 N, listed in Table 2,
may be used. Other instances where a heavier load may be required are where the grain structure is very
coarse and the indentation area at lower loads can contact only a few grains of the material (e.g. a multiphase
material).
4.6.3 The following items shall be confirmed before the test.
a) Check the zero of the measuring system.

ISO 14705:2026(en)
b) Check the measuring system using a calibrated scale or certified indentation in a test block.
c) Check the operation of the loading system by performing a test on a certified test block.
d) Check the condition of the indenter by examining the indentation made in the test block. Replace the
indenter, if necessary, by taking into account the conditions given in 4.6.10.
e) A test block with high hardness has to be used in order to obtain impressions in the same size range as
expected during tests on ceramics.
4.6.4 The indenter shall be cleaned prior to and during the test series, as ceramic powders or fragments
from the ceramic test piece can adhere to the diamond indenter.
4.6.5 The test piece shall be placed on a rigid support. The support surface shall be clean and free from
foreign matter. The test piece shall lie firmly on the support, so that displacement cannot occur during the
test.
4.6.6 Carefully adjust the illumination and focusing conditions, in order to obtain the optimum view and
clarity of the indentation. Both indentation tips shall be in focus at the same time. Do not change the focus
when measuring the distance from tip to tip.
4.6.7 Bring the indenter into contact with the test surface and apply the test force in a direction
perpendicular to the surface, without shock or vibration, until the applied force attains the specified value.
The time from the initial application of the force until the full test force is reached shall not be less than 1 s
nor greater than 5 s. The duration of application of the constant maximum test force shall be 15 s.
4.6.8 Throughout the test, the apparatus shall be protected from shock or vibration.
4.6.9 The distance between the centre of any
...