SIST EN ISO 7783:2018

SLOVENSKI STANDARD
01-december-2018
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SIST EN ISO 7783:2012
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Paints and varnishes - Determination of water-vapour transmission properties - Cup
method (ISO 7783:2018)
Beschichtungsstoffe - Bestimmung der Wasserdampfdurchlässigkeit - Schalenverfahren
(ISO 7783:2018)
Peintures et vernis - Détermination des propriétés de transmission de la vapeur d'eau -
Méthode de la coupelle (ISO 7783:2018)
Ta slovenski standard je istoveten z: EN ISO 7783:2018
ICS:
87.040 Barve in laki Paints and varnishes
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 7783
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2018
EUROPÄISCHE NORM
ICS 87.040 Supersedes EN ISO 7783:2011
English Version
Paints and varnishes - Determination of water-vapour
transmission properties - Cup method (ISO 7783:2018)
Peintures et vernis - Détermination des propriétés de Beschichtungsstoffe - Bestimmung der
transmission de la vapeur d'eau - Méthode de la Wasserdampfdurchlässigkeit - Schalenverfahren (ISO
coupelle (ISO 7783:2018) 7783:2018)
This European Standard was approved by CEN on 22 September 2018.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey 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
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7783:2018 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 7783:2018) has been prepared by Technical Committee ISO/TC 35 "Paints and
varnishes" in collaboration with Technical Committee CEN/TC 139 “Paints and varnishes” 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 May 2019, and conflicting national standards shall be
withdrawn at the latest by May 2019.
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 7783:2011.
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, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 7783:2018 has been approved by CEN as EN ISO 7783:2018 without any modification.

INTERNATIONAL ISO
STANDARD 7783
Second edition
2018-10
Paints and varnishes — Determination
of water-vapour transmission
properties — Cup method
Peintures et vernis — Détermination des propriétés de transmission
de la vapeur d'eau — Méthode de la coupelle
Reference number
ISO 7783:2018(E)
©
ISO 2018
ISO 7783:2018(E)
© ISO 2018
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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

ISO 7783:2018(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Apparatus and materials. 3
5.1 Substrate for non-self-supporting coatings . 3
5.2 Test cup . 3
5.3 Ammonium dihydrogen phosphate (NH H PO ) solution for wet-cup method . 4
4 2 4
5.4 Desiccant for dry-cup method . 4
5.5 Sealing material . 4
5.6 Test enclosure . 4
5.7 Balance . 4
6 Preparation for the test . 5
6.1 Sampling of coating material . 5
6.2 Preparation of test pieces . 5
6.2.1 Preparation of non-self-supporting coatings on a porous substrate . 5
6.2.2 Preparation of self-supporting coatings . 5
6.2.3 Conditioning . 5
6.3 Determination of the thickness of the coating. 6
6.3.1 General. 6
6.3.2 Determination of the thickness of the coating by calculation . 6
6.3.3 Determination of the thickness of the coating by optical, mechanical or
other suitable methods . 6
6.4 Preparation of the test assemblies . 6
7 Procedure. 7
8 Expression of results . 7
8.1 Water-vapour transmission rate, V, of self-supporting coatings . 7
8.1.1 Rate of flow of water vapour, G, through the test piece . 7
8.1.2 Water-vapour transmission rate, V, of the coating . 7
8.2 Water-vapour transmission rate, V, of non-self-supporting coatings . 8
8.2.1 General. 8
8.2.2 Rate of flow of water vapour through the substrate, G , and through the
s
substrate plus coating, G . 8
cs
8.2.3 Water-vapour transmission rate, V , of the substrate . 8
s
8.2.4 Water-vapour transmission rate, V , of the substrate plus coating. 9
cs
8.2.5 Water-vapour transmission rate, V, of the coating . 9
8.3 Water-vapour diffusion-equivalent air layer thickness, s . 9
d
8.4 Water-vapour resistance factor, μ .10
9 Precision .10
9.1 Repeatability, (r) .10
9.2 Reproducibility, (R) .10
10 Test report .11
Annex A (informative) Derivation of Formula (8) for the calculation of the water-vapour
diffusion-equivalent air layer thickness, s .12
d
Annex B (normative) Use of molten wax for sealing the test assembly .14
Bibliography .18
ISO 7783:2018(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 35, Paints and varnishes, Subcommittee
SC 9, General test methods for paints and varnishes.
This second edition cancels and replaces the first edition (ISO 7783:2011), of which it constitutes a
minor revision to correct the conversion factor in Formula (3) and to add a reference to ISO 4618 on
paints and varnishes terminology in Clause 3.
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 2018 – All rights reserved

ISO 7783:2018(E)
Introduction
This document is one of a series of standards dealing with the sampling and testing of paints, varnishes
and related products. It describes a method for determining the water-vapour transmission rate of self-
supporting and non-self-supporting coatings.
The water-vapour transmission rate is not necessarily a linear function of film thickness, temperature
or relative-humidity difference. A determination carried out under one set of conditions will not
necessarily be comparable with one carried out under other conditions. Therefore, it is essential that
the conditions of test are chosen to be as close as possible to the conditions of use.
Water-vapour transmission is of greatest interest under conditions of high humidity. For this reason,
the wet-cup method has been adopted as the reference method. By agreement, other procedures and
conditions, like the dry-cup method, may be used.
INTERNATIONAL STANDARD ISO 7783:2018(E)
Paints and varnishes — Determination of water-vapour
transmission properties — Cup method
1 Scope
This document specifies a method for determining the water-vapour transmission properties of
coatings of paints, varnishes and related products.
It supplements ISO 12572. As far as possible, the procedure, the definitions and the calculations
have been taken over from ISO 12572. ISO 12572 can be consulted, if necessary, to obtain a better
understanding of the procedure specified in this document.
Water-vapour transmission rates of more than 680 g/(m ⋅d) (i.e. water-vapour diffusion-equivalent air
layer thicknesses, s , of less than 0,03 m) are not accurately quantified by the test method described in
d
this document.
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 1513, Paints and varnishes — Examination and preparation of test samples
ISO 2808, Paints and varnishes — Determination of film thickness
ISO 3233-1, Paints and varnishes — Determination of the percentage volume of non-volatile matter —
Part 1: Method using a coated test panel to determine non-volatile matter and to determine dry film density
by the Archimedes principle
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 4618, Paints and varnishes — Terms and definitions
ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4618 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
water-vapour transmission rate
V
mass of water vapour that is transmitted over a given period through a given surface area of a test
piece under specified constant conditions of relative humidity at each face of the test piece
Note 1 to entry: It is measured in grams per square metre per day [g/(m ⋅d)].
ISO 7783:2018(E)
Note 2 to entry: A water-vapour transmission rate measured at atmospheric pressure, p, can be converted to the
equivalent value at standard atmospheric pressure, p , by multiplying by p/p . This allows a linear correlation
0 0
with the water-vapour diffusion-equivalent air layer thickness (s ) value (see 3.3) by the factor 20,4.
d
Note 3 to entry: The term “water-vapour transmission” is often incorrectly used for water-vapour
transmission rate.
3.2
rate of flow of water vapour through the test piece
G
mass of water vapour that is transmitted over a given period through a test piece under specified
constant conditions of relative humidity at each face of the test piece
Note 1 to entry: It is measured in grams per hour.
3.3
water-vapour diffusion-equivalent air layer thickness
s
d
thickness of a static air layer that has, under the same conditions of measurement, the same water-
vapour transmission rate as the coating tested
Note 1 to entry: It is measured in metres.
3.4
water-vapour resistance factor
μ
factor that indicates how many times greater the water-vapour resistance of a material is compared
with a layer of static air of the same thickness at the same temperature and pressure
Note 1 to entry: It is dimensionless.
Note 2 to entry: The calculation and use of a water-vapour resistance factor is meaningful only if the water-
vapour transmission rate of a particular material is a constant, i.e. independent of the thickness, which, however,
is normally not the case for coatings.
3.5
test piece
supporting substrate with the coating applied to it
3.6
test piece
coating alone
3.7
wet-cup method
method of measuring water-vapour permeability in which the test piece is sealed to the rim of a cup
containing a saturated aqueous solution of ammonium dihydrogen phosphate
Note 1 to entry: This is the most convenient manner of carrying out determinations of water-vapour permeability
under conditions of high relative humidity (between 93 % and 50 %).
3.8
dry-cup method
method of measuring water-vapour permeability in which the test piece is sealed to the rim of a cup
containing a desiccant
Note 1 to entry: This is the most convenient manner of carrying out determinations of water-vapour permeability
under conditions of low relative humidity (between 50 % and 3 %).
2 © ISO 2018 – All rights reserved

ISO 7783:2018(E)
3.9
test assembly
assembly consisting of a test piece sealed to the rim of a test cup containing saturated ammonium
dihydrogen phosphate solution in contact with undissolved ammonium dihydrogen phosphate crystals
(wet-cup method) or containing desiccant (dry-cup method)
3.10
test area
area of the face of the test piece through which the water vapour flows during the test
Note 1 to entry: It is measured in square metres.
4 Principle
A test assembly consisting of a self-supporting coating, or a non-self-supporting coating on porous
substrate, sealed to the rim of a cup is placed in a test enclosure kept at a specified temperature (e.g.
23 °C) and relative humidity (e.g. 50 %). The relative humidity in the cup is maintained at a constant
level — either at 93 % by means of a saturated salt solution (wet-cup method) or at 3 % by means of a
desiccant (dry-cup method). Because of the difference between the partial pressure of the water vapour
inside the test cup and the partial pressure of the water vapour in the test enclosure, water vapour
diffuses through the coating under test. By weighing the test assembly at suitable time intervals, the
change in mass of the test assembly is followed. From the change in mass and the test area, the water-
vapour transmission rate and the water-vapour diffusion-equivalent air layer thickness are calculated.
5 Apparatus and materials
5.1 Substrate for non-self-supporting coatings
Any homogenous, porous material which has a water-vapour transmission rate above 240 g/(m ⋅d)
is suitable for use as the substrate for non-self-supporting coatings, for instance polyethylene frits,
cellular-concrete discs, glass frits, unglazed ceramic tiles.
When using cellular-concrete substrates, the coating shall be applied on the smooth side.
If the coating system under test does not include a primer and it is necessary to use one before applying
the coating system under test, do so, but the transmission rate of the primed substrate will have to be
determined separately.
5.2 Test cup
Test cups are made of glass, plastic or metal. The test cup used shall be resistant to corrosion under the
conditions of the test.
NOTE For aluminium test cups, a wall thickness of 1 mm has been found to be satisfactory.
The exact surface area of the test piece exposed is defined by the design of the cup. The area of the
2 2
exposed surface shall be at least 50 cm for non-self-supporting coatings and at least 10 cm for self-
supporting coatings.
The cup shall be so designed that an efficient seal is made between it and the test piece, using sealing
material (see 5.5), if necessary.
When the saturated solution (5.3) or desiccant (5.4) has been placed in the cup, the area of the surface
of the saturated solution or desiccant shall be similar to that of the exposed surface of the test piece.
The air gap between the test piece and the surface of the solution or desiccant shall be between 10 mm
and 30 mm.
ISO 7783:2018(E)
5.3 Ammonium dihydrogen phosphate (NH H PO ) solution for wet-cup method
4 2 4
Prepare a saturated solution of ammonium dihydrogen phosphate (analytical grade) in contact with
undissolved crystals, using water of at least grade 3 purity as defined in ISO 3696.
In the wet-cup method, which is the reference method, the relative humidity in a cup containing this
saturated solution will be 93 %. The resulting water vapour pressure difference relative to the test
enclosure, in which the relative humidity is maintained at 50 %, is 1 207 Pa at standard temperature
(23 °C) and pressure (101 325 Pa).
5.4 Desiccant for dry-cup method
The desiccant shall be either dried silica gel in the form of granules passing a 4 mm sieve but retained
on a 1,6 mm sieve, or anhydrous calcium chloride which has been dried at 200 °C.
It shall be possible to complete the test before the efficiency of the desiccant is reduced appreciably.
In the dry-cup method, the relative humidity in the cup shall be 3 %. The resulting water-vapour
pressure difference relative to the test enclosure, in which the relative humidity is maintained at 50 %,
is 1 400 Pa at standard temperature (23 °C) and pressure (101 325 Pa).
5.5 Sealing material
It shall be ensured that the test assembly is fully sealed, with the exception of the test area. The
sealing material shall be impermeable and free from cracks. For sealing, mechanical clamps, wax or
two-component sealing materials have been found suitable. The use of molten wax for sealing the test
assembly is described in Annex B.
The sealing material shall not contain solvents or other volatile constituents which could cause any
change in the coating or lead to weighing errors caused by the evaporation of solvent.
NOTE The most usual way of sealing the cup is to fit the cup with a mechanical clamp or screw device which
can incorporate a sealing ring made of a suitable polymeric material. Mechanical sealing might not be suitable if
the test piece has a rough surface or if it is very fragile. In such cases, the use of molten wax is more satisfactory.
5.6 Test enclosure
The test enclosure shall be of a design such that both the temperature and the relative humidity in the
enclosure can be controlled at the levels required for the test. Thus, for the reference method, the enclosure
shall be capable of maintaining the temperature at (23 ± 2) °C and the relative humidity at (50 ± 5) %
(standard conditions as defined in ISO 3270). To ensure uniform conditions during the test, the air shall
be caused to flow over the outer surface of the test piece at a speed between 0,02 m/s and 0,3 m/s. The
ambient air pressure shall be corrected to standard pressure (101 325 Pa) as described in 8.1.
NOTE Maintaining the air speed at the correct level is the second most important source of error after
preparation of the te
...