1、 ISO 2017 Paints and varnishes Visual comparison of colour of paints Peintures et vernis Comparaison visuelle de la couleur des peintures INTERNATIONAL STANDARD ISO 3668 Third edition 2017-05 Reference number ISO 3668:2017(E) ISO 3668:2017(E)ii ISO 2017 All rights reserved COPYRIGHT PROTECTED DOCUME
2、NT ISO 2017, Published in Switzerland All rights reserved. Unless otherwise specified, 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 p
3、ermission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO 3668:2017(
4、E)Foreword iv 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Principle 1 5 Illumination for colour matching 2 5.1 General . 2 5.2 Artificial illumination by means of a colour matching booth . 2 6 Observer 2 7 Test panels and reference standards 3 7.1 General . 3 7.2 Reference st
5、andards . 3 7.3 Preparation and coating . . 3 7.4 Drying . 4 8 Procedure for colour comparison 4 8.1 General . 4 8.2 Colour comparison 4 9 Assessment of metamerism 4 10 Test report . 5 Annex A (normative) Colour difference rating scheme 6 Annex B (informative) Metameric matches . 7 Bibliography 8 IS
6、O 2017 All rights reserved iii Contents Page ISO 3668:2017(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 comm
7、ittees. 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
8、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 th
9、e 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
10、. 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 th
11、is document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World
12、Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: w w w . i s o .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 third
13、 edition cancels and replaces the second edition (ISO 3668:1998), which has been technically revised with the following changes: testing using natural daylight has been deleted; CIE illuminant FL 11 has been added as third type of artificial light source; determination of the film thickness has been
14、 deleted because it is irrelevant for the assessment of colour (the paint layer needs to be sufficient in hiding; the hiding power is more important); the normative references have been updated; the supplementary test conditions previously in Annex A have been integrated in the test report.iv ISO 20
15、17 All rights reserved INTERNATIONAL ST ANDARD ISO 3668:2017(E) Paints and varnishes Visual comparison of colour of paints 1 Scope This document 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 fres
16、hly prepared standard) using artificial light sources in a standard booth. It is not applicable to coatings containing special-effect pigments, e.g. metallic, without previous agreement on all details of illuminating and viewing conditions 2 Normative references The following documents are referred
17、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 1514, Paints and varnishes Sta
18、ndard panels for testing ISO 3270, Paints and varnishes and their raw materials Temperatures and humidities for conditioning and testing ISO 11664-2, Colorimetry Part 2: CIE standard illuminants ISO 18314-1, Analytical colorimetry Part 1: Practical colour measurement ISO 23603, Standard method of as
19、sessing the spectral quality of daylight simulators for visual appraisal and measurement of colour CIE 15.3, Colorimetry CIE 51.2, A method for assessing the quality of daylight simulators for colorimetry 3 T erms a nd definiti ons No terms and definitions are listed in this document. ISO and IEC ma
20、intain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at h t t p :/ www .electropedia .org/ ISO Online browsing platform: available at h t t p :/ www .iso .org/ obp 4 Principle The colours of the paint films to be compared are observed und
21、er specified illumination and viewing conditions, using a colour matching booth. For the expression of colour difference components (hue, chroma and lightness) a procedure is described, i.e. description by using a particular rating scheme. Assessment of metamerism is also taken into account. ISO 201
22、7 All rights reserved 1 ISO 3668:2017(E) 5 Illumination for colour matching 5.1 General The quality of natural daylight is variable and observers judgements are likely to be affected by nearby coloured objects. For referee purposes, therefore, closely controlled artificial illumination in a colour-
23、matching booth shall be used. The observer shall wear clothing of a neutral colour and no strongly coloured surfaces, other than panels under test, shall be permitted in the field of view. 5.2 Artificial illuminat ion b y means of a c olou r mat ching booth The colour matching booth shall be an encl
24、osure 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, CIE standard Illuminant A (as specified in ISO 11664-2) or CIE illuminant FL 11 (as specified i
25、n CIE 15.3). 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 CIE method specified in CIE Publication No. 51.2 and ISO 23603. The spectral distribution of the illuminant
26、 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 ma
27、tt neutral grey (the amount of a* and b* should be less than 1,0) with a lightness L* of about 45 to 55. However, when mainly light colours and near white colours are to be compared, the interior of the booth may be painted so as to have a lightness L* of about 65 or higher in order to give a lower
28、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 L* of about 25. NOTE L*, a* and b* refer to the CIELAB System (see ISO 11664-4). To ensure an appropriate surrounding field for colour
29、 comparison, the table surface in the booth shall be covered by a neutral grey panel, its luminance factor being chosen to be the same colour as the light booth. Some diffusing element (e.g. a diffusing screen) shall normally be used to ensure a distribution spread of light and to avoid the reflecti
30、on 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 his product can be expected to conform to this
31、document. 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 to confirm an observers suitability, more sensitive tests, for example the Farnswor
32、th 100 hue test or stricter anomaloscope measurements, are desirable. If an observer wears glasses to correct his or her vision, these shall have uniform spectral transmission throughout the visible spectrum. As colour vision changes significantly with age, it is desirable that observers over 40 yea
33、rs of age are tested using a proper method whereby the observer is requested to choose the best match from a metameric series of colours. For colour comparison work, not only normal colour vision but also colour discrimination ability or experience is important. To avoid eye fatigue effects, pastel
34、or complementary colours shall not be viewed immediately after strong colours. When comparing bright, saturated colours, if a decision cannot be made rapidly, the 2 ISO 2017 All rights reserved ISO 3668:2017(E) observer shall look away for some seconds at the neutral grey of the surrounding field be
35、fore attempting a further comparison. The quality of visual judgements falls off severely if the observer works continuously. Rest periods of several minutes during which no colour matching is attempted shall, therefore, be taken frequently. 7 Test panels and reference standards 7.1 General Both tes
36、t panels and reference colour standards shall be flat and preferably about 150 mm 100 mm in size. Suitable materials for test panels are tinplate, hard aluminium, glazed cardboard, steel or glass, complying with ISO 1514. Panel size and viewing distance shall be chosen so that the panel subtends a f
37、ield of observation having an opening making an angle at the eye of about 10. If larger panels are used, a viewing field corresponding to the 10 observer shall be formed by using a grey mask. Typical viewing distances and sizes for the square openings of the mask are given in Table 1. Table 1 Viewin
38、g distances and opening sizes of masks Viewing distance Opening size cm cm cm 30 5,4 5,4 50 8,7 8,7 70 12,3 12,3 90 15,8 15,8 7.2 Reference standards Only colour standards of satisfactory colour permanence shall be used as reference standards. Wherever possible, the reference standards shall be of t
39、he same size as the test panels and shall have closely similar gloss and surface texture. Store the reference panels at ambient temperature of (23 5) C and not exposed to direct sunlight, preferably in a dark location. Put the panels into contaminant-free paper bags, or equivalent, to protect the su
40、rface of the panels against hits and scratches. 7.3 Preparation and coating Prepare the test panels as specified and, where appropriate, in accordance with ISO 1514. The panel shall be coated by a closely specified or agreed method, because the method of application and film thickness may affect the
41、 colour considerably. If the test panel is to be compared against a standard paint, it shall be coated with the paint or system under test and a similar panel coated with the standard paint or system. The method of application and the applied film thickness shall be as closely as possible identical.
42、 The film thickness applied should preferably be such as to ensure complete hiding of the substrate, in order to eliminate the influence of the substrate. To check that in this case, black and white charts may be used. ISO 2017 All rights reserved 3 ISO 3668:2017(E) 7.4 Drying Dry (or stove) each co
43、ated test panel for the specified time and under the specified conditions and condition in the standard atmosphere as specified in ISO 3270 for a minimum of 16 h with free circulation of air and not exposed to direct sunlight. 8 Procedure for colour comparison 8.1 General For standardized colour com
44、parison, it is necessary to have an observer with normal colour vision, and reproducible illumination viewing conditions. Most paints are required to match a standard in daylight, but the spectral composition of daylight varies considerably. Hence, it is preferred to use artificial daylight for colo
45、ur evaluation, as individual sources are more stable over a limited period than natural daylight and therefore enable more reproducible colour comparisons to be made. Artificial average daylight illumination is represented by CIE standard illuminant D65. Incandescent illumination is additionally use
46、d to check for metamerism. Incandescent illumination is represented by CIE standard illuminant A; alternatively, a fluorescent light source such as CIE illuminant FL 11 may be used as a secondary light source to check for metamerism. The visual assessment of colour differences using the components h
47、ue, chroma and lightness should preferably be performed in accordance with the rating scheme given in Annex A. By agreement between the interested parties, a simplified rating scheme comprising less than six steps may be used. However, in order to avoid confusion the meaning of the individual rating
48、s given in Annex A shall not be changed. 8.2 Colour comparison View the two panels, or the panel and the reference colour standard, in artificial daylight, conforming to CIE Standard Illuminant D65, in the colour-matching booth (5.2). Place the panels side by side, touching and in the same plane, at
49、 a distance of about 500 mm from the eyes. Compare the colour of the paint film prepared from the material under test with that of the reference colour standard or of the film prepared from the standard paint. To improve accuracy of comparison, compare the colours with the positions of the panels reversed from time to time. When, exceptionally, films of widely different levels of gloss are to be compared, the method of viewing shall be agreed between the interested parties. View the panels at an angle of 45 to t
