SIST EN ISO 3668:2002

SLOVENSKI STANDARD
SIST EN ISO 3668:2002
01-september-2002
Barve in laki - Vizualna primerjava barve premaza (ISO 3668:1998)
Paints and varnishes - Visual comparison of the colour of paints (ISO 3668:1998)
Beschichtungsstoffe - Visueller Vergleich der Farbe von Beschichtungen
(Farbabmusterung) (ISO 3668:1998)
Peintures et vernis - Comparaison visuelle de la couleur des peintures (ISO 3668:1998)
Ta slovenski standard je istoveten z: EN ISO 3668:2001
ICS:
87.040 Barve in laki Paints and varnishes
SIST EN ISO 3668:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 3668:2002

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SIST EN ISO 3668:2002
EUROPEAN STANDARD
EN ISO 3668
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2001
ICS 87.040
English version
Paints and varnishes - Visual comparison of the colour of paints
(ISO 3668:1998)
Peintures et vernis - Comparaison visuelle de la couleur Beschichtungsstoffe - Visueller Vergleich der Farbe von
des peintures (ISO 3668:1998) Beschichtungen (Farbabmusterung) (ISO 3668:1998)
This European Standard was approved by CEN on 7 March 2001.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 3668:2001 E
worldwide for CEN national Members.

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SIST EN ISO 3668:2002
Page 2
EN ISO 3668:2001
Foreword
The text of the International Standard from Technical Committee ISO/TC 35 "Paints and varnishes" of the
International Organization for Standardization (ISO) has been taken over as an European Standard by
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 November 2001, and conflicting national standards shall be
withdrawn at the latest by November 2001.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark,
Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal,
Spain, Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of the International Standard ISO 3668:1998 has been approved by CEN as a European Standard
without any modification.
NOTE: Normative references to International Standards are listed in annex ZA (normative).

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SIST EN ISO 3668:2002
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EN ISO 3668:2001
Annex ZA
(normative)
Normative references to international publications
with their relevant European publications
This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of
the publication referred to applies (including amendments).
NOTE Where an International Publication has been modified by common modifications, indicated by (mod.), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
ISO 1512 1991 Paints and varnishes - Sampling of products in liquid or EN 21512 1994
paste form
ISO 1513 1992 Paints and varnishes - Examination and preparation of EN ISO 1513 1994
samples for testing
ISO 1514 1993 Paints and varnishes - Standard panels for testing EN ISO 1514 1997
ISO 2808 1997 Paints and varnishes - Determination of film thickness EN ISO 2808 1999
ISO 3270 1984 Paints and varnishes and their raw materials - EN 23270 1991
Temperatures and humidities for conditioning and
testing

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SIST EN ISO 3668:2002

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SIST EN ISO 3668:2002
INTERNATIONAL ISO
STANDARD 3668
Second edition
1998-08-01
Paints and varnishes — Visual comparison
of the colour of paints
Peintures et vernis — Comparaison visuelle de la couleur des peintures
A
Reference number
ISO 3668:1998(E)

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SIST EN ISO 3668:2002
ISO 3668:1998(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.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 3668 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 3668:1976),
which has been technically revised.
Annexes A and B form an integral part of this International Standard.
Annex C is for information only.
©  ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii

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SIST EN ISO 3668:2002
©
INTERNATIONAL STANDARD  ISO ISO 3668:1998(E)
Paints and varnishes — Visual comparison of the colour
of paints
1  Scope
This International Standard is one of a series of standards dealing with the sampling and testing of paints, varnishes
and related products.
It specifies a method for the visual comparison of the colour of films of paints or related products against a standard
(either a reference standard or a freshly prepared standard) using either natural daylight or artificial light sources in
a standard booth.
It is not applicable to coatings containing special-effect pigments, e.g. metallics, without previous agreement on all
details of illuminating and viewing conditions.
2  Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 1512:1991, Paints and varnishes — Sampling of products in liquid or paste form.
ISO 1513:1992, Paints and varnishes — Examination and preparation of samples for testing.
ISO 1514:1993, Paints and varnishes — Standard panels for testing.
ISO 2808:1997, Paints and varnishes — Determination of film thickness.
ISO 3270:1984, Paints and varnishes and their raw materials — Temperatures and humidities for conditioning and
testing.
1)
ISO 7724-1:— , Paints and varnishes — Colorimetry — Part 1: Principles.
2)
ISO 7724-2:— , Paints and varnishes — Colorimetry — Part 2: Colour measurement.
3)
ISO 7724-3:— , Paints and varnishes — Colorimetry — Part 3: Calculation of colour differences by CIELAB.
CIE Publication No. 51:1981, A method for assessing the quality of daylight simulators for colorimetry.
CIE Publication No. 15.2:1986, Colorimetry.

1) To be published. (Revision of ISO 7724-1:1984)
2) To be published. (Revision of ISO 7724-2:1984)
3) To be published. (Revision of ISO 7724-3:1984)
1

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SIST EN ISO 3668:2002
©
ISO
ISO 3668:1998(E)
3  Principle
The colours of the paint films to be compared are observed under specified illumination and viewing conditions,
either in natural daylight or in artificial light, using a colour-matching booth in the latter case. For the expression of
colour difference components (hue, chroma and lightness), a procedure is described, i.e. description using a
particular rating scheme. Assessment of metamerism is also taken into account.
4  Required supplementary information
For any particular application, the test method specified in this International Standard needs to be completed by
supplementary information. The items of supplementary information are given in annex A.
5  Illumination for colour matching
5.1  General
For routine colour matching, either natural or artificial daylight may be used. The quality of natural daylight is
variable, and observers' judgements are likely to be affected by nearby coloured objects. For reference purposes
therefore, closely controlled artificial illumination in a colour-matching booth shall be used. The observer shall wear
clothing of a neutral colour, and no strongly coloured surfaces, other than the panels under test, shall be permitted
in the field of view.
5.2  Natural daylight illumination
Diffuse daylight, preferably from a partially cloudy north sky in the northern hemisphere and a partially cloudy south
sky in the southern hemisphere, and not reflected from any strongly coloured object such as a red brick wall or
green tree, shall be used. Illumination shall be uniform over the area in which test panels are displayed and at a
level of at least 2 000 lx. Direct sunlight shall be avoided.
5.3  Artificial illumination by means of a colour-matching booth
The colour-matching booth shall be an enclosure from which external light is excluded and which is illuminated by a
light source giving a spectral power distribution falling on the test panel, approximating to that of CIE standard
illuminant D65 or CIE standard illuminant A.
Where a light source having a different spectral distribution is used, it shall be agreed by the interested parties.
The quality of simulation of daylight shall be assessed by the method described in CIE Publication No. 51. The
spectral distribution of the illuminant shall be in category BC (CIELAB) or better.
The level of illumination at the colour-matching position shall be between 1 000 lx and 4 000 lx, a figure towards the
upper end of the range being desirable for dark colours.
The interior of the colour-matching booth for general use shall be painted a matt neutral grey (the amount of * and
a
* shall be less than 1,0) with a lightness * of about 45 to 55. However, when mainly light colours and near-white
b L
colours are to be compared, the interior of the booth may be painted so as to have a lightness * of about 65 or
L
higher in order to give a lower brightness contrast with the colour to be examined; when mainly dark colours are to
be compared, the interior of the booth may be painted matt black with a lightness * of about 25.
L
NOTE — L*, a* and b* refer to the CIELAB system (see ISO 7724-1).
To ensure an appropriate surrounding field for colour comparison, the table surface in the booth shall be covered by
a neutral grey panel, its luminance factor being chosen to be similar to that of the samples to be compared.
2

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SIST EN ISO 3668:2002
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ISO
ISO 3668:1998(E)
A diffusing screen shall normally be used to avoid the reflection of an image of the lamp from the test panel. The
spectral distribution properties of the light source shall include the spectral transmission of the screen.
The manufacturer of the light source shall disclose the number of running hours during which the product can be
expected to conform to this International Standard.
6  Observer
Observers shall have normal colour vision and shall be selected carefully because a significant proportion of people
have defective colour vision. An Ishihara test will reveal severe defects but
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