ASTM C609-90(2000)
(Test Method)Standard Test Method for Measurement of Small Color Differences Between Ceramic Wall or Floor Tile
Standard Test Method for Measurement of Small Color Differences Between Ceramic Wall or Floor Tile
SCOPE
1.1 This test method covers the measurement of a visually small color difference between two pieces of solid-colored, glazed or unglazed ceramic tile, using any photoelectric instrument that meets the requirements specified in the test method. The amount and the direction of the color difference are expressed numerically, with sufficient accuracy for use in product specification.
1.2 This test method should not be used for determining small color differences between tile that have a multicolored, speckled, or textured surface, because the results may not be valid.
1.3 Color difference between specimens found to be metamers (see 3.2), by visual examination, can be accurately evaluated by spectrophotometric measurement only. Therefore, visual color comparison of test specimen and reference specimen should be made under incandescent light and under daylight fluorescent light before any instrumental measurement. If visual color difference under the two light sources is not of the same magnitude, the pair of tile must be considered metamers.
1.4 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:C609–90(Reapproved 2000)
Standard Test Method for
Measurement of Small Color Differences Between Ceramic
Wall or Floor Tile
This standard is issued under the fixed designation C609; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope E259 Practice for Preparation of Pressed Powder White
Reflectance Factor Transfer Standards for Hemispherical
1.1 This test method covers the measurement of a visually
Geometry
small color difference between two pieces of solid-colored,
E284 Terminology of Appearance
glazed or unglazed ceramic tile, using any photoelectric
instrument that meets the requirements specified in the test
3. Terminology
method. The amount and the direction of the color difference
3.1 Definitions:
are expressed numerically, with sufficient accuracy for use in
3.1.1 color difference, DE—the vector sum of the three
product specification.
component differences DL, Da, and Db. It is expressed in units
1.2 This test method should not be used for determining
of judds and may be computed by the equation shown under
small color differences between tile that have a multicolored,
9.7.The values DL, Da, and Db are obtained by calculating the
speckled, or textured surface, because the results may not be
component differences as follows:
valid.
DL 5 L 2 L
1.3 Colordifferencebetweenspecimensfoundtobemetam-
t r
ers (see 3.2), by visual examination, can be accurately evalu-
Da 5 a 2 a
t r
ated by spectrophotometric measurement only. Therefore, vi-
Db 5 b 2 b
t r
sualcolorcomparisonoftestspecimenandreferencespecimen
should be made under incandescent light and under daylight where:
fluorescent light before any instrumental measurement. If t = test specimen, and
r = reference specimen.
visual color difference under the two light sources is not of the
The quantity DE has a positive value and it describes the
same magnitude, the pair of tile must be considered metamers.
magnitudebutnotthedirectionofcolordifferencebetweenthe
1.4 The values stated in inch-pound units are to be regarded
test specimen and the reference specimen. The direction of
as the standard. The values given in parentheses are for
information only. color difference depends upon the algebraic signs of the
components DL, Da, and Db. A positive DL value means that
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the the test specimen is lighter than the reference against which it
is being compared, and a negative DLvalue means that the test
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- specimen is darker. However, the algebraic signs of chroma-
ticity components, Da and Db, do not convey an easily
bility of regulatory limitations prior to use.
visualized difference in color attributes and can best be
2. Referenced Documents
visualized by plotting the corresponding points in the chroma-
2.1 ASTM Standards: ticity plane.
C242 Terminology of Ceramic Whitewares and Related 3.1.2 color space—the colors of opaque specimens such as
Products ceramic tile are described in terms of three color scales L, a,
D2244 Test Method for Calculation of Color Differences and b. Scale L is a measure of lightness, a is a measure of
redness or greenness, and b is a measure of yellowness or
from Instrumentally Measured Color Coordinates
blueness. The units for each of the three scales are so chosen
that they represent equally perceptible color differences. The
interrelation of these color scales is more readily visualized if
This test method is under the jurisdiction of ASTM Committee C-21 on
the scales are represented geometrically as the three mutually
Ceramic Whitewares and Related Products and is the direct responsibility of
Subcommittee C21.06 on Ceramic Tile.
Current edition approved Dec. 28, 1990. Published February 1991. Originally
published as C609–67. Last previous edition C609–86. Illing, A. M., Balinkin, I., “Precision in Measurement of Small Color
Annual Book of ASTM Standards, Vol 15.02. Differences,” American Ceramic Society Bulletin, Vol 44, No. 12, 1965, pp.
Annual Book of ASTM Standards, Vol 06.01. 956–962.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C609
perpendicularaxesofathree-dimensionalcolorspace,withthe enough information, since its magnitude gives a fairly good
L axis in the vertical direction, the positive a axis (redness) to correlation with human opinions about the size of a color
the right, and the positive b axis (yellowness) in a counter- difference.
clockwise direction from the positive a axis (see Fig. 1). 4.4 The DE units of color difference are usually designated
3.1.3 metamers—See Terminology E284. as the National Institute of Standards and Technology (NIST)
3.1.4 reference specimen—any tile for which a match is units of color difference, or simply as “judds.”
desired.
5. Significance and Use
3.1.5 repeatability—the standard deviation of results ob-
5.1 The test method described herein provides instrumental
tained by the same operator using the same instrument in
means as the basis for judging color difference. Magnitude of
successive measurements.
color difference between pairs of ceramic tile can be deter-
3.1.6 reproducibility—the standard deviation of results ob-
mined and expressed in numerical terms.
tained by different operators using the same or different types
5.2 Based on interlaboratory investigation, color difference
of instruments in different laboratories.
DE of plain-colored tile, if determined according to this test
3.1.7 standard—the plaque or other media of established
method, should give excellent reproducibility with a standard
tristimulus value, against which standardization of the instru-
deviation of not more than s= 60.15 judds.
ment is made.
3.1.8 test specimen—any piece of tile whose color differ-
6. Apparatus
ence from a reference specimen is to be evaluated.
6.1 Type of Instrument—Any color-measuring instrument
3.1.9 tile—See Terminology C242.
either of the spectrophotometer or colorimeter type, capable of
yielding data that can be transformed mathematically into the
4. Summary of Test Method
International Commission of Illumination (CIE) tristimulus
4.1 This test method consists of measuring the color of tile
values X, Y,and Z,maybeused.Itmusthaveacolordifference,
specimens with any photoelectric instrument that meets the
DE, repeatability (see 3.1.5) of s= 60.2 judds or less, based
specified requirements. Such instruments should give results
on five independent measurements. The well-known standard
comparable to differences observed by the human eye, and
deviation equation shown as follows is used to calculate the
yield for each color a unique, three-number characterization,
standard deviation.
havingknownrelationshiptothetristimulusvalues X, Y,and Z.
2 ½
s5 (F X 2 X /N (1)
@ ~ ! #
j j j
4.2 Some instruments read out directly in the L, a, and b
At the present time, spectrophotometers of the Hardy and
units which are required by this test method. Data from others
Cary type and colorimeters such as Gardner and Hunter color
must be converted to L, a, and b according to the equations
difference meters, the Color Eye, Colormaster and Chro-
given here, or others provided by the instrument supplier. The
mosorter, may be considered as suitable instruments.
algebraic differences in L, a, and b values, between any two
6.2 Spectral Characteristics—The spectral energy distribu-
specimens, are then used to calculate the color difference, DE.
tion of the light source and the spectral sensitivity of the
4.3 Thecompletedescriptionoftheamountanddirectionof
receptor, if necessary, may have to be modified with properly
a color difference between any two pieces of tile can be given
selectedfilterstoprovideresponsefunctionsapproximatingthe
simply as the three respective differences between the pairs of
tristimulus functions of the CIE standard observer for illumi-
values for L, a, and b. For some purposes, DE alone provides
nant C.
7. Standards
7.1 Primary Standard—The primary standard for reflec-
tancemeasurementisalayeroffreshlypreparedbariumsulfate
(see Practice E259).
7.2 Working Standard—Because of the difficulty of prepar-
ing a primary standard each time and its varia
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