SIST EN ISO 12571:2022

SLOVENSKI STANDARD
oSIST prEN ISO 12571:2021
01-februar-2021
Higrotermalno obnašanje gradbenih materialov in proizvodov - Ugotavljanje
higroskopnosti (ISO/DIS 12571:2020)
Hygrothermal performance of building materials and products - Determination of
hygroscopic sorption properties (ISO/DIS 12571:2020)
Wärme- und feuchtetechnisches Verhalten von Baustoffen und Bauprodukten -
Bestimmung der hygroskopischen Sorptionseigenschaften (ISO/DIS 12571:2020)
Performance hygrothermique des matériaux et produits pour le bâtiment - Détermination
des propriétés de sorption hygroscopique (ISO/DIS 12571:2020)
Ta slovenski standard je istoveten z: prEN ISO 12571
ICS:
91.100.01 Gradbeni materiali na Construction materials in
splošno general
91.120.30 Zaščita pred vlago Waterproofing
oSIST prEN ISO 12571:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 12571:2021

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oSIST prEN ISO 12571:2021
DRAFT INTERNATIONAL STANDARD
ISO/DIS 12571
ISO/TC 163/SC 1 Secretariat: DIN
Voting begins on: Voting terminates on:
2020-12-23 2021-03-17
Hygrothermal performance of building materials and
products — Determination of hygroscopic sorption
properties
Performance hygrothermique des matériaux et produits pour le bâtiment — Détermination des propriétés
de sorption hygroscopique
ICS: 91.100.01
IMPORTANT — Please use this updated version dated 2020-10-27,
and discard any previous version of this DIS. Table A.1 has been corrected.
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 12571:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020

---------------------- Page: 3 ----------------------
oSIST prEN ISO 12571:2021
ISO/DIS 12571:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

---------------------- Page: 4 ----------------------
oSIST prEN ISO 12571:2021
ISO/DIS 12571:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions, symbols and units . 1
3.1 Terms and definitions . 1
3.2 Symbols and units . 2
4 Principle . 2
4.1 Sorption curve . 2
4.2 Desorption curve . 2
5 Apparatus . 3
5.1 Desiccator method . 3
5.2 Climatic chamber method . 3
6 Test specimens. 3
6.1 Specification of the test specimens . 3
6.2 Number of test specimens . 3
7 Procedure. 3
7.1 Test conditions . 3
7.2 Desiccator method . 4
7.2.1 General. 4
7.2.2 Sorption curve . 4
7.2.3 Desorption curve . 4
7.3 Climatic chamber method . 5
7.3.1 Sorption curve . 5
7.3.2 Desorption curve . 6
8 Calculation and expression of results . 6
8.1 Hygroscopic sorption . 6
8.2 Equilibrium moisture content curves . 6
9 Accuracy of measurement . 7
9.1 Error in moisture content . 7
9.2 Control of environmental conditions . 7
9.2.1 Desiccator method . 7
9.2.2 Climatic chamber method . 7
10 Test report . 8
Annex A (informative) Air relative humidities above saturated solutions in equilibrium .9
Annex B (informative) Preparation of saturated solutions .12
Annex C (informative) Example of the procedure for determining a point on a sorption curve .15
Annex D (informative) Method using a glass jar .16
Bibliography .18
© ISO 2020 – All rights reserved iii

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oSIST prEN ISO 12571:2021
ISO/DIS 12571:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
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 163, Thermal performance and energy use
in the built environment Subcommittee SC 1, Test and measurement methods.
This third edition cancels and replaces the second edition (ISO 12571:2013), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Revision of Table A.1
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 © ISO 2020 – All rights reserved

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oSIST prEN ISO 12571:2021
ISO/DIS 12571:2020(E)

Introduction
The International Organization for Standardization (ISO) draw attention to the fact that it is claimed
that compliance with this document may involve the use of a patent.
ISO take no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO that he/she is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In
this respect, the statement of the holder of this patent right is registered with ISO. Information may be
obtained from the patent database available at www .iso .org/ patents.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights other than those in the patent database. ISO shall not be held responsible for identifying
any or all such patent rights.
© ISO 2020 – All rights reserved v

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oSIST prEN ISO 12571:2021

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oSIST prEN ISO 12571:2021
DRAFT INTERNATIONAL STANDARD ISO/DIS 12571:2020(E)
Hygrothermal performance of building materials and
products — Determination of hygroscopic sorption
properties
1 Scope
This International Standard specifies two alternative methods for determining hygroscopic sorption
properties of porous building materials and products:
a) using desiccators and weighing cups (desiccator method);
b) using a climatic chamber (climatic chamber method).
The desiccator method is the reference method.
This International Standard does not specify the method for sampling.
The methods specified in this International Standard can be used to determine the moisture content of
a sample in equilibrium with air at a specific temperature and humidity.
2 Normative references
The following referenced documents are indispensable for the application 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 9346, Hygrothermal performance of buildings and building materials — Physical quantities for mass
transfer — Vocabulary
ISO 12570, Hygrothermal performance of building materials and products — Determination of moisture
content by drying at elevated temperature
3 Terms and definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 9346 and the following apply.
3.1.1
equilibrium moisture content
moisture content of a porous material in equilibrium with the environment and the relative humidity of
the ambient air, at a specified temperature
3.1.2
moisture content mass by mass
mass of evaporable water divided by mass of dry material
3.1.3
moisture content volume by volume
volume of evaporable water divided by volume of dry material
© ISO 2020 – All rights reserved 1

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oSIST prEN ISO 12571:2021
ISO/DIS 12571:2020(E)

3.1.4
moisture content mass by volume
mass of evaporable water divided by volume of dry material
Note 1 to entry: The mass of water is determined by weighing the specimen before and after drying at the
appropriate drying temperature until constant mass is reached.
3.1.5
sorption curve
curve established at a series of increasing equilibrium relative humidities at a given temperature
3.1.6
desorption curve
curve established at a series of decreasing equilibrium relative humidities at a given temperature
3.2 Symbols and units
Symbol Quantity Unit
m mass of test specimen kg
m mass of dried test specimen kg
0
u moisture content mass by mass kg/kg
3 3
ψ moisture content volume by volume m /m
3
w moisture content mass by volume kg/m
4 Principle
4.1 Sorption curve
The specimen is dried to constant mass. While maintaining a constant temperature, the specimen is
placed consecutively in a series of test environments, with relative humidity increasing in stages. The
moisture content is determined when equilibrium with each environment is reached. Equilibrium with
the environment is established by weighing the specimen until constant mass is reached. A minimum of
four test atmospheres shall be selected in the humidity range under consideration.
After establishing the moisture content at each relative humidity the sorption curve can be drawn.
4.2 Desorption curve
The starting point for desorption is a relative humidity of at least 95 %. This might be the last point
of the sorption curve or might be reached by sorption from a dried test specimen. While maintaining
a constant temperature, the specimen is placed consecutively in a series of test environments, with
relative humidity decreasing in stages. The moisture content is determined when equilibrium with each
environment is reached. Equilibrium with the environment is established by weighing the specimen
until constant mass is reached. A minimum of four test atmospheres shall be selected in the humidity
range under consideration. Finally, the specimen is dried to constant mass.
After establishing the moisture content at each relative humidity the desorption curve can be drawn.
NOTE A defined starting point for desorption has been chosen for better reproducibility.
2 © ISO 2020 – All rights reserved

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oSIST prEN ISO 12571:2021
ISO/DIS 12571:2020(E)

5 Apparatus
5.1 Desiccator method
The test apparatus shall include:
a) weighing cups which do not absorb water and with tight-fitting lids;
b) balance, capable of weighing to an accuracy of ± 0,01 % of the mass of the test specimen;
NOTE If larger weighing cups are used, the weighing accuracy can be determined with respect to the
total mass and the required accuracy of the test results.
c) drying oven, in accordance with ISO 12570;
d) desiccator, capable of maintaining the relative humidity within ± 2 % relative humidity;
e) constant-temperature chamber, capable of maintaining the specified test temperature to an
accuracy of ± 0,5 K.
5.2 Climatic chamber method
The test apparatus shall include:
a) weighing cups which do not absorb water;
b) balance, capable of weighing to an accuracy of ± 0,01 % of the mass of the test specimen;
NOTE If larger weighing cups are used, the weighing accuracy can be determined with respect to the
total mass and the required accuracy of the test results.
c) drying oven, in accordance with ISO 12570;
d) climatic chamber, capable of maintaining the relative humidity within ± 5 % relative humidity
and the temperature within ± 2 K over the whole test area.
6 Test specimens
6.1 Specification of the test specimens
A test specimen shall be representative of the product and have a mass of at least 10 g. Specimens of
3
materials with a dry density less than 300 kg/m shall have an area of at least 100 mm × 100 mm. If it
can be demonstrated from other references that the result will not be affected, a test specimen can be
cut or crushed into smaller pieces to reduce the time to reach equilibrium with the environment.
6.2 Number of test specimens
A minimum of three specimens shall be tested. The procedure in Clause 7 shall be applied to each
specimen.
7 Procedure
7.1 Test conditions
Reference sorption curves shall be established at a temperature of (23 ± 0,5) °C or (27 ± 0,5) °C in tropical
countries. If agreed between the parties, sorption curves can be established at other temperatures for
specific applications.
© ISO 2020 – All rights reserved 3

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oSIST prEN ISO 12571:2021
ISO/DIS 12571:2020(E)

7.2 Desiccator method
7.2.1 General
Make up the appropriate saturated aqueous solution to achieve the necessary relative humidity in the
desiccator.
Standard air relative humidities to be selected for measuring sorption curves are shown in Table 1.
Choose 5 or more conditions that include No.2, No.4 and No.6 in Table 1.
NOTE Annex A gives the air relative humidities of various saturated solutions in equilibrium, and Annex B
describes the preparation of various solutions.
Place the desiccator in the constant-temperature chamber (see Figure 1). The depth of saturated
aqueous solution shall be 30 mm–50 mm.
Table 1 — Standard air relative humidities above saturated solutions in equlibrium
Relative humidity
No. Substance
a
(%)
1 KOH 9 8
2 MgCl ·6H O 33 33
2 2
3 Mg(NO ) ·6H O 53 52
3 2 2
4 NaCl 75 75
5 KCl 85 84
6 KNO 93 93
3
a
Relative humidities in left column correspond to air temperature 23 °C. Relative
humidities in right column correspond to air temperature 27 °C.
7.2.2 Sorption curve
Weigh the weighing cup and lid when empty and dry. Put the test specimen into the weighing cup
without the li
...

SLOVENSKI STANDARD
oSIST prEN ISO 12571:2020
01-december-2020
Higrotermalno obnašanje gradbenih materialov in proizvodov - Ugotavljanje
higroskopnosti (ISO/DIS 12571:2020)
Hygrothermal performance of building materials and products - Determination of
hygroscopic sorption properties (ISO/DIS 12571:2020)
Wärme- und feuchtetechnisches Verhalten von Baustoffen und Bauprodukten -
Bestimmung der hygroskopischen Sorptionseigenschaften (ISO/DIS 12571:2020)
Performance hygrothermique des matériaux et produits pour le bâtiment - Détermination
des propriétés de sorption hygroscopique (ISO/DIS 12571:2020)
Ta slovenski standard je istoveten z: prEN ISO 12571
ICS:
91.100.01 Gradbeni materiali na Construction materials in
splošno general
91.120.30 Zaščita pred vlago Waterproofing
oSIST prEN ISO 12571:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 12571:2020

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oSIST prEN ISO 12571:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 12571
ISO/TC 163/SC 1 Secretariat: DIN
Voting begins on: Voting terminates on:
2020-10-15 2021-01-07
Hygrothermal performance of building materials and
products — Determination of hygroscopic sorption
properties
Projection thermique — Revêtements appliqués par projection thermique — Représentation symbolique
sur les dessins
ICS: 91.100.01
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 12571:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020

---------------------- Page: 3 ----------------------
oSIST prEN ISO 12571:2020
ISO/DIS 12571:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

---------------------- Page: 4 ----------------------
oSIST prEN ISO 12571:2020
ISO/DIS 12571:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions, symbols and units . 1
3.1 Terms and definitions . 1
3.2 Symbols and units . 2
4 Principle . 2
4.1 Sorption curve . 2
4.2 Desorption curve . 2
5 Apparatus . 3
5.1 Desiccator method . 3
5.2 Climatic chamber method . 3
6 Test specimens. 3
6.1 Specification of the test specimens . 3
6.2 Number of test specimens . 3
7 Procedure. 3
7.1 Test conditions . 3
7.2 Desiccator method . 4
7.2.1 General. 4
7.2.2 Sorption curve . 4
7.2.3 Desorption curve . 4
7.3 Climatic chamber method . 5
7.3.1 Sorption curve . 5
7.3.2 Desorption curve . 6
8 Calculation and expression of results . 6
8.1 Hygroscopic sorption . 6
8.2 Equilibrium moisture content curves . 6
9 Accuracy of measurement . 7
9.1 Error in moisture content . 7
9.2 Control of environmental conditions . 7
9.2.1 Desiccator method . 7
9.2.2 Climatic chamber method . 7
10 Test report . 8
Annex A (informative) Air relative humidities above saturated solutions in equilibrium .9
Annex B (informative) Preparation of saturated solutions .12
Annex C (informative) Example of the procedure for determining a point on a sorption curve .15
Annex D (informative) Method using a glass jar .16
Bibliography .18
© ISO 2020 – All rights reserved iii

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oSIST prEN ISO 12571:2020
ISO/DIS 12571:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
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 163, Thermal performance and energy use
in the built environment Subcommittee SC 1, Test and measurement methods.
This third edition cancels and replaces the second edition (ISO 12571:2013), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Revision of Table A.1
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 © ISO 2020 – All rights reserved

---------------------- Page: 6 ----------------------
oSIST prEN ISO 12571:2020
ISO/DIS 12571:2020(E)

Introduction
The International Organization for Standardization (ISO) draw attention to the fact that it is claimed
that compliance with this document may involve the use of a patent.
ISO take no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO that he/she is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In
this respect, the statement of the holder of this patent right is registered with ISO. Information may be
obtained from the patent database available at www .iso .org/ patents.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights other than those in the patent database. ISO shall not be held responsible for identifying
any or all such patent rights.
© ISO 2020 – All rights reserved v

---------------------- Page: 7 ----------------------
oSIST prEN ISO 12571:2020

---------------------- Page: 8 ----------------------
oSIST prEN ISO 12571:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 12571:2020(E)
Hygrothermal performance of building materials and
products — Determination of hygroscopic sorption
properties
1 Scope
This International Standard specifies two alternative methods for determining hygroscopic sorption
properties of porous building materials and products:
a) using desiccators and weighing cups (desiccator method);
b) using a climatic chamber (climatic chamber method).
The desiccator method is the reference method.
This International Standard does not specify the method for sampling.
The methods specified in this International Standard can be used to determine the moisture content of
a sample in equilibrium with air at a specific temperature and humidity.
2 Normative references
The following referenced documents are indispensable for the application 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 9346, Hygrothermal performance of buildings and building materials — Physical quantities for mass
transfer — Vocabulary
ISO 12570, Hygrothermal performance of building materials and products — Determination of moisture
content by drying at elevated temperature
3 Terms and definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 9346 and the following apply.
3.1.1
equilibrium moisture content
moisture content of a porous material in equilibrium with the environment and the relative humidity of
the ambient air, at a specified temperature
3.1.2
moisture content mass by mass
mass of evaporable water divided by mass of dry material
3.1.3
moisture content volume by volume
volume of evaporable water divided by volume of dry material
© ISO 2020 – All rights reserved 1

---------------------- Page: 9 ----------------------
oSIST prEN ISO 12571:2020
ISO/DIS 12571:2020(E)

3.1.4
moisture content mass by volume
mass of evaporable water divided by volume of dry material
Note 1 to entry: The mass of water is determined by weighing the specimen before and after drying at the
appropriate drying temperature until constant mass is reached.
3.1.5
sorption curve
curve established at a series of increasing equilibrium relative humidities at a given temperature
3.1.6
desorption curve
curve established at a series of decreasing equilibrium relative humidities at a given temperature
3.2 Symbols and units
Symbol Quantity Unit
m mass of test specimen kg
m mass of dried test specimen kg
0
u moisture content mass by mass kg/kg
3 3
ψ moisture content volume by volume m /m
3
w moisture content mass by volume kg/m
4 Principle
4.1 Sorption curve
The specimen is dried to constant mass. While maintaining a constant temperature, the specimen is
placed consecutively in a series of test environments, with relative humidity increasing in stages. The
moisture content is determined when equilibrium with each environment is reached. Equilibrium with
the environment is established by weighing the specimen until constant mass is reached. A minimum of
four test atmospheres shall be selected in the humidity range under consideration.
After establishing the moisture content at each relative humidity the sorption curve can be drawn.
4.2 Desorption curve
The starting point for desorption is a relative humidity of at least 95 %. This might be the last point
of the sorption curve or might be reached by sorption from a dried test specimen. While maintaining
a constant temperature, the specimen is placed consecutively in a series of test environments, with
relative humidity decreasing in stages. The moisture content is determined when equilibrium with each
environment is reached. Equilibrium with the environment is established by weighing the specimen
until constant mass is reached. A minimum of four test atmospheres shall be selected in the humidity
range under consideration. Finally, the specimen is dried to constant mass.
After establishing the moisture content at each relative humidity the desorption curve can be drawn.
NOTE A defined starting point for desorption has been chosen for better reproducibility.
2 © ISO 2020 – All rights reserved

---------------------- Page: 10 ----------------------
oSIST prEN ISO 12571:2020
ISO/DIS 12571:2020(E)

5 Apparatus
5.1 Desiccator method
The test apparatus shall include:
a) weighing cups which do not absorb water and with tight-fitting lids;
b) balance, capable of weighing to an accuracy of ± 0,01 % of the mass of the test specimen;
NOTE If larger weighing cups are used, the weighing accuracy can be determined with respect to the
total mass and the required accuracy of the test results.
c) drying oven, in accordance with ISO 12570;
d) desiccator, capable of maintaining the relative humidity within ± 2 % relative humidity;
e) constant-temperature chamber, capable of maintaining the specified test temperature to an
accuracy of ± 0,5 K.
5.2 Climatic chamber method
The test apparatus shall include:
a) weighing cups which do not absorb water;
b) balance, capable of weighing to an accuracy of ± 0,01 % of the mass of the test specimen;
NOTE If larger weighing cups are used, the weighing accuracy can be determined with respect to the
total mass and the required accuracy of the test results.
c) drying oven, in accordance with ISO 12570;
d) climatic chamber, capable of maintaining the relative humidity within ± 5 % relative humidity
and the temperature within ± 2 K over the whole test area.
6 Test specimens
6.1 Specification of the test specimens
A test specimen shall be representative of the product and have a mass of at least 10 g. Specimens of
3
materials with a dry density less than 300 kg/m shall have an area of at least 100 mm × 100 mm. If it
can be demonstrated from other references that the result will not be affected, a test specimen can be
cut or crushed into smaller pieces to reduce the time to reach equilibrium with the environment.
6.2 Number of test specimens
A minimum of three specimens shall be tested. The procedure in Clause 7 shall be applied to each
specimen.
7 Procedure
7.1 Test conditions
Reference sorption curves shall be established at a temperature of (23 ± 0,5) °C or (27 ± 0,5) °C in tropical
countries. If agreed between the parties, sorption curves can be established at other temperatures for
specific applications.
© ISO 2020 – All rights reserved 3

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oSIST prEN ISO 12571:2020
ISO/DIS 12571:2020(E)

7.2 Desiccator method
7.2.1 General
Make up the appropriate saturated aqueous solution to achieve the necessary relative humidity in the
desiccator.
Standard air relative humidities to be selected for measuring sorption curves are shown in Table 1.
Choose 5 or more conditions that include No.2, No.4 and No.6 in Table 1.
NOTE Annex A gives the air relative humidities of various saturated solutions in equilibrium, and Annex B
describes the preparation of various solutions.
Place the desiccator in the constant-temperature chamber (see Figure 1). The depth of saturated
aqueous solution shall be 30 mm–50 mm.
Table 1 — Standard air relative humidities above saturated solutions in equlibrium
Relative humidity
No. Substance
a
(%)
1 KOH 9 8
2 MgCl ·6H O 33 33
2 2
3 Mg(NO ) ·6H O 53 52
3 2 2
4 NaCl 75 75
5 KCl 85 84
6 KNO 93 93
3
a
Relative humidities in left column correspond to air temperature 23 °C. Relative
humidities in right column correspond to air temperature 27 °C.
7.2.2 Sorption curve
Weigh the weighing cup and lid when empty and dry. Put the test specimen into the weighing cup
without the lid and dry it until constant mass in the drying oven at the temperat
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