ASTM C609-07(2019)
(Test Method)Standard Test Method for Measurement of Light Reflectance Value and Small Color Differences Between Pieces of Ceramic Tile
Standard Test Method for Measurement of Light Reflectance Value and Small Color Differences Between Pieces of Ceramic Tile
SIGNIFICANCE AND USE
5.1 This test method describes the means of determining the LRV of a tile specimen. Certain building codes require the use of materials rated by LRV. Application of this test method provides the means for rating ceramic tile. LRVs reported for ceramic tile should include reference to the observer and illuminant for which the rating is valid.
5.2 LRV is a property dependent on the overall color of a tile specimen. Control of LRV is achieved through control of color and adherence to color specifications will govern the acceptability of a product with respect to LRV. Therefore, a product cannot be judged as having an unacceptable LRV unless the color of the product is found to be unacceptable.
5.3 Mixtures of several tile products are commonly installed on a surface, requiring a means to calculate LRV for a product mix. The rating obtained for an individual tile product can be used to calculate the LRV for a product mix using the following equation:
where: n = number of products included in the mix p1 to n = the proportion of the surface area taken up by each product, the sum of p1 to pn must equal one LRV1 to n = the LRV for each product used For example, a mixture of two products is used on a surface. Two thirds of the surface area is covered by product A with a LRV of 75 %, and one third of the surface is covered by product B with an LRV of 60 % (see Fig. 2). Using the equation, the product mix is found to have an LRV of 70 %.
FIG. 2 Example of a Product Mix Used on a Surface
5.4 The test method described herein provides instrumental means as the basis for judging color difference. Magnitude of color difference between pairs of ceramic tile can be determined and expressed in numerical terms.
5.5 Based on interlaboratory investigation,3 color difference ΔE of plain-colored tile, if determined according to this test method, should give excellent reproducibility with a standard deviation of not more than σ = ±0.15 units....
SCOPE
1.1 This test method covers the measurement of Light Reflectance Value (LRV) and visually small color difference between pieces of glazed or unglazed ceramic tile, using any spectrophotometer that meets the requirements specified in the test method. LRV and the magnitude and direction of the color difference are expressed numerically, with sufficient accuracy for use in product specification.
1.2 LRV may be measured for either solid-colored tile or tile having a multicolored, speckled, or textured surface. For tile that are not solid-colored, an average reading should be obtained from multiple measurements taken in a pattern representative of the overall sample as described in 9.2 of this test method. Small color difference between tiles should only be measured for solid-color tiles. Small color difference between tile that have a multicolored, speckled, or textured surface, are not valid.
1.3 For solid colored tile, a comparison of the test specimen and reference specimen should be made under incandescent, fluorescent and daylight illuminant conditions. The use of multiple illuminants allows the color difference measurement to be made without the risk of wrongly accepting a match when the tiles being compared are metamers. (See 3.1.4.)
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issue...
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Designation:C609 −07 (Reapproved 2019)
Standard Test Method for
Measurement of Light Reflectance Value and Small Color
Differences Between Pieces of Ceramic 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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This test method covers the measurement of Light
Reflectance Value (LRV) and visually small color difference
2. Referenced Documents
between pieces of glazed or unglazed ceramic tile, using any
2.1 ASTM Standards:
spectrophotometer that meets the requirements specified in the
C242 Terminology of Ceramic Whitewares and Related
test method. LRV and the magnitude and direction of the color
Products
difference are expressed numerically, with sufficient accuracy
D2244 Practice for Calculation of Color Tolerances and
for use in product specification.
Color Differences from Instrumentally Measured Color
1.2 LRV may be measured for either solid-colored tile or
Coordinates
tile having a multicolored, speckled, or textured surface. For
E259 Practice for Preparation of Pressed Powder White
tile that are not solid-colored, an average reading should be
Reflectance Factor Transfer Standards for Hemispherical
obtained from multiple measurements taken in a pattern
and Bi-Directional Geometries
representative of the overall sample as described in 9.2 of this
E284 Terminology of Appearance
test method. Small color difference between tiles should only
be measured for solid-color tiles. Small color difference
3. Terminology
between tile that have a multicolored, speckled, or textured
3.1 Definitions:
surface, are not valid.
*
3.1.1 color difference, ∆E and ∆E —the vector sum of the
H
1.3 For solid colored tile, a comparison of the test specimen * * * *
three component differences ∆L , ∆a , and ∆b for ∆E and
and reference specimen should be made under incandescent,
∆L ,∆a ,∆b for ∆E . The superscript * indicates color
H H H H
fluorescent and daylight illuminant conditions. The use of
difference based on the use of CIELAB color space equations,
multiple illuminants allows the color difference measurement
while the subscript H indicates color difference based on the
tobemadewithouttheriskofwronglyacceptingamatchwhen
useoftheHunterequations. ∆E isexpressedinunitsofjudds,
H
the tiles being compared are metamers. (See 3.1.4.) *
while ∆E is a unit-less value. Either form of the ∆E can be
1.4 The values stated in inch-pound units are to be regarded solved for using the equation shown in 10.3. For both the
as the standard. The values given in parentheses are for CIELAB and Hunter equations, the values ∆ L, ∆a, and ∆b are
information only. obtained by calculating the component differences as follows:
1.5 This standard does not purport to address all of the
∆L 5 L 2 L
t r
safety concerns, if any, associated with its use. It is the
∆a 5 a 2 a
t r
responsibility of the user of this standard to establish appro-
∆b 5 b 2 b
t r
priate safety, health, and environmental practices and deter-
where:
mine the applicability of regulatory limitations prior to use.
t = test specimen, and
1.6 This international standard was developed in accor-
r = reference specimen.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
The quantity ∆E has a positive value and it describes the
Development of International Standards, Guides and Recom-
magnitude but not the direction of color difference between the
test specimen and the reference specimen. The direction of
ThistestmethodisunderthejurisdictionofASTMCommitteeC21onCeramic
Whitewares and Related Products and is the direct responsibility of Subcommittee
C21.06 on Ceramic Tile. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Aug. 1, 2019. Published August 2019. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1967. Last previous edition approved in 2014 as C609 – 07 (2014). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/C0609-07R19. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C609−07 (2019)
color difference depends upon the algebraic signs of the 3.1.7 reproducibility—the standard deviation of results ob-
components ∆ L, ∆a, and ∆b. A positive ∆L value means that tained by different operators using the same or different types
the test specimen is lighter than the reference against which it of instruments in different laboratories.
is being compared, and a negative ∆L value means that the test
3.1.8 standard—the plaque or other media of established
specimen is darker. However, the algebraic signs of chroma-
tristimulus value, against which standardization of the instru-
ticity components, ∆ a and ∆b, do not convey an easily
ment is made.
visualized difference in color attributes and can best be
3.1.9 test specimen—any piece of tile whose LRV or color
visualized by plotting the corresponding points in the chroma-
difference from a reference specimen is to be evaluated.
ticity plane.
3.1.10 tile—See Terminology C242.
3.1.2 color space—the colors of opaque specimens such as
3.1.11 spectrophotometric—measurement of the spectral re-
ceramic tile are described in terms of three color scales L, a,
flectance or transmittance curve of a material.
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
4. Summary of Test Method
blueness. The units for each of the three scales are so chosen
that they represent equally perceptible color differences. The
4.1 This test method explains the technique for measuring
interrelation of these color scales is more readily visualized if
the LRV and color of tile specimens with a spectrophotometric
the scales are represented geometrically as the three mutually
instrument that meets the specified requirements. Such instru-
perpendicularaxesofathree-dimensionalcolorspace,withthe
ments should give results comparable to differences observed
L axis in the vertical direction, the positive a axis (redness) to
by the human eye, and yield for each color a unique, three-
the right, and the positive b axis (yellowness) in a counter-
number characterization, having known relationship to the
clockwise direction from the positive a axis (see Fig. 1).
tristimulus values X, Y, and Z.
4.2 Spectrophotometic measurement systems commonly
provide measurement data in a variety of color units and allow
for automatic conversion of data from one color system to
another. Select equations are included in this test method for
*
manual determination of LRVfromY, L or L . Equations are
H
* * *
also provided for calculation of L ,a and b and L ,a and b
H H H
from tristimulus values X,Y, Z.The algebraic differences in L,
a, and b values, between any two specimens, are then used to
calculate the color difference, ∆E. If manual calculations are
required, consult the instrument supplier for conversions not
provided within this test method.
4.3 The complete description of the amount and direction of
a color difference between any two pieces of solid colored tile
canbegivensimplyasthethreerespectivedifferencesbetween
thepairsofvaluesfor L, a,and b.Forsomepurposes, ∆Ealone
providesenoughinformation,sinceitsmagnitudegivesafairly
good correlation with human opinions about the size of a color
difference.
4.4 To protect against approval of a metameric color match,
FIG. 1 Three-Dimensional Color Space
multiple illuminates must be used when evaluating color
difference between solid colored tiles.Atest specimen needs to
prove suitable with respect to a reference specimen under
3.1.3 light reflectance value, (LRV)—the luminance factor
incandescent, fluorescent and daylight illuminant conditions in
Y, of a sample expressed as a percent. Thus, a Y value of 70
order to be judged as acceptable.
wouldequatetoanLRVof70%.TheLRVindicatestheportion
of light cast on a sample that is not absorbed.
5. Significance and Use
3.1.4 metamers—See Terminology E284.
5.1 This test method describes the means of determining the
3.1.5 reference specimen—any tile for which a match is
LRV of a tile specimen. Certain building codes require the use
desired.
of materials rated by LRV. Application of this test method
3.1.6 repeatability—the standard deviation of results ob-
provides the means for rating ceramic tile. LRVs reported for
tained by the same operator using the same instrument in
ceramic tile should include reference to the observer and
successive measurements.
illuminant for which the rating is valid.
Illing, A. M., Balinkin, I., “Precision in Measurement of Small Color
Differences,” American Ceramic Society Bulletin , Vol 44, No. 12, 1965, pp. Billmeyer, F.W. Jr., Saltzman, M., Principles of Color Technology, 2nd Edition,
956–962. John Wiley & Sons, Inc., New York, NY, 1981 p. 78, 85.
C609−07 (2019)
5.2 LRV is a property dependent on the overall color of a illuminant conditions ensure the color differences calculated
tile specimen. Control of LRV is achieved through control of between a test and reference specimen account for the possible
color and adherence to color specifications will govern the occurrence of metamerism.
acceptability of a product with respect to LRV. Therefore, a
6. Apparatus
product cannot be judged as having an unacceptable LRV
unless the color of the product is found to be unacceptable. 6.1 Type of Instrument for LRV Measurement—Any color-
measuring spectrophotometric instrument capable of yielding
5.3 Mixturesofseveraltileproductsarecommonlyinstalled
data that can be transformed mathematically into the Interna-
on a surface, requiring a means to calculate LRV for a product
tional Commission of Illumination (CIE) tristimulus values X,
mix. The rating obtained for an individual tile product can be
Y, and Z, may be used. It must have a color difference, ∆E,
used to calculate the LRV for a product mix using the
repeatability (see 3.1.6)of σ = 60.2 units or less, based on five
following equation:
independent measurements. The well-known standard devia-
LRV 5 p LRV 1p LRV 1….1p LRV (1)
product mix ( 1 1 2 2 n n
tionequationshownasfollowsisusedtocalculatethestandard
where:
deviation.
½
n = number of products included in the mix
σ 5 F X 2 X /N (2)
@ ~ ! #
(j j j
p = the proportion of the surface area taken up by
1ton
6.2 Type of Instrument for Color Measurement—For the
each product, the sum of p to p must equal
1 n
measurement of solid colored tile, the spectrophotometric
one
measurement system must meet all of the requirements for
LRV to n = the LRV for each product used
LRV measurement and be capable of yielding tristimulus
For example, a mixture of two products is used on a surface.
values X, Y, and Z, for daylight, incandescent and fluorescent
Two thirds of the surface area is covered by product A with a
illuminants.
LRV of 75 %, and one third of the surface is covered by
6.3 Instrument Setup—For measurement of LRV and color
product B with an LRV of 60 % (see Fig. 2). Using the
difference, spectrophotometric measurements should be taken
equation, the product mix is found to have an LRV of 70 %.
with specular component included (SCI). If the instrument
being used is not capable of taking SCI measurements, then all
reported measurements must include a notation stating mea-
surement obtained with specular component excluded (SCE).
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 variability, calibrated
pieces of white opaque glass, porcelain enamel plaques, or
glazed ceramic tile are used as working standards and are
usually supplied by the manufacturer of the instrument. The
FIG. 2 Example of a Product Mix Used on a Surface
manufacturer of each type of instrument provides numerical
specifications for the working standards, which have a definite
5.4 The test method described herein provides instrumental
relationship to the CIE values X, Y, and Z.
means as the basis for judging color difference. Magnitude of
color difference between pairs of ceramic tile can be deter-
8. Test Specimens
mined and expressed in numerical terms.
1 1
8.1 Size—The preferred size of test specimens is 4 ⁄4 by 4 ⁄4
5.5 Based on interlaboratory investigation, color difference
in. (108 by 108 mm) because most instruments are equipped
∆E of plain-colored tile, if determined according to this test
with a holder of that size which assures that the identical
method, should give excellent reproducibility with a standard
surface area may be measured repeatedly. Specimens larger
deviation of not more than σ = 60.15 units. LRV should also
may be reduced to that size by cutting. The required sample
give excellent reproducibility when used for solid colored tile
size is dependent on the instrument being used to measure the
based on the relationship between LRV and either the Y
test and reference specimens. Many instruments can be con-
tristimulus or L value. However, LRV reproducibility for
figured to measure a sample using different size viewing
multicolored, speckled, or textured surface tile will be depen-
apertures. The largest area of view capable of being used
dent upon the degree of variation of the tile specimen, and will
without interference from the edges of the tile should be
require a different measurement procedure to minimize the
selected. However, the same aperture size should be used for
impact of the variation.
all measurements involved in a comparison. Tile with surfaces
5.6 The test method requires the use of multiple illuminants
for the determination of color difference between solid-colored
Duncan, A. J., Quality Control and Industrial Statistics, R. D. Irwin, Inc.,
tiles. Evaluation under incandescent, fluorescent and daylight Homewood, IL, 1959, p. 45.
C609−07 (2019)
1/3
smaller than the aperture opening may not be measured with L* 5 116 Y/Y 216 (4)
~ !
n
thistestmethod.Likewise,tilewithinsufficientflatareacannot 1/3 1/3
a* 5 500@~X/X ! 2 ~Y/Y ! #
n n
be tested for color difference.
1/3 1/3
b* 5 500@~Y/Y ! 2 ~Z/Z ! #
n n
8.2 Selection—When the tes
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C609 − 07 (Reapproved 2014) C609 − 07 (Reapproved 2019)
Standard Test Method for
Measurement of Light Reflectance Value and Small Color
Differences Between Pieces of Ceramic 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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the measurement of Light Reflectance Value (LRV) and visually small color difference between
pieces of glazed or unglazed ceramic tile, using any spectrophotometer that meets the requirements specified in the test method.
LRV and the magnitude and direction of the color difference are expressed numerically, with sufficient accuracy for use in product
specification.
1.2 LRV may be measured for either solid-colored tile or tile having a multicolored, speckled, or textured surface. For tile that
are not solid-colored, an average reading should be obtained from multiple measurements taken in a pattern representative of the
overall sample as described in 9.2 of this test method. Small color difference between tiles should only be measured for solid-color
tiles. Small color difference between tile that have a multicolored, speckled, or textured surface, are not valid.
1.3 For solid colored tile, a comparison of the test specimen and reference specimen should be made under incandescent,
fluorescent and daylight illuminant conditions. The use of multiple illuminants allows the color difference measurement to be made
without the risk of wrongly accepting a match when the tiles being compared are metamers. (See 3.1.4.)
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C242 Terminology of Ceramic Whitewares and Related Products
D2244 Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates
E259 Practice for Preparation of Pressed Powder White Reflectance Factor Transfer Standards for Hemispherical and
Bi-Directional Geometries
E284 Terminology of Appearance
3. Terminology
3.1 Definitions:
* * * * *
3.1.1 color difference, ΔE and ΔE —the vector sum of the three component differences ΔL , Δa , and Δb for ΔE and
H
ΔL ,Δa ,Δb for ΔE . The superscript * indicates color difference based on the use of CIELAB color space equations, while the
H H H H
*
subscript H indicates color difference based on the use of the Hunter equations. ΔE is expressed in units of judds, while ΔE is
H
This test method is under the jurisdiction of ASTM Committee C21 on Ceramic Whitewares and Related Products and is the direct responsibility of Subcommittee C21.06
on Ceramic Tile.
Current edition approved Jan. 1, 2014Aug. 1, 2019. Published February 2014August 2019. Originally approved in 1967. Last previous edition approved in 20072014 as
C609 – 07.C609 – 07 (2014). DOI: 10.1520/C0609-07R14.10.1520/C0609-07R19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C609 − 07 (2019)
a unit-less value. Either form of the ΔE can be solved for using the equation shown in 10.3. For both the CIELAB and Hunter
equations, the values Δ L, Δa, and Δb are obtained by calculating the component differences as follows:
ΔL 5 L 2 L
t r
Δa 5 a 2 a
t r
Δb 5 b 2 b
t r
where:
t = test specimen, and
r = reference specimen.
The quantity ΔE has a positive value and it describes the magnitude but not the direction of color difference between the test
specimen and the reference specimen. The direction of color difference depends upon the algebraic signs of the components Δ L,
Δa, and Δb. A positive ΔL value means that the test specimen is lighter than the reference against which it is being compared, and
a negative ΔL value means that the test specimen is darker. However, the algebraic signs of chromaticity components, Δ a and Δb,
do not convey an easily visualized difference in color attributes and can best be visualized by plotting the corresponding points
in the chromaticity plane.
3.1.2 color space—the colors of opaque specimens such as ceramic tile are described in terms of three color scales L, a, 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 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 the scales are represented geometrically as the three mutually perpendicular axes of a
three-dimensional color space, with the L axis in the vertical direction, the positive a axis (redness) to the right, and the positive
b axis (yellowness) in a counterclockwise direction from the positive a axis (see Fig. 1).
FIG. 1 Three-Dimensional Color Space
3.1.3 light reflectance value, (LRV)—the luminance factor Y, of a sample expressed as a percent. Thus, a Y value of 70 would
equate to an LRV of 70%. The LRV indicates the portion of light cast on a sample that is not absorbed.
3.1.4 metamers—See Terminology E284.
3.1.5 reference specimen—any tile for which a match is desired.
3.1.6 repeatability—the standard deviation of results obtained by the same operator using the same instrument in successive
measurements.
3.1.7 reproducibility—the standard deviation of results obtained by different operators using the same or different types of
instruments in different laboratories.
3.1.8 standard—the plaque or other media of established tristimulus value, against which standardization of the instrument is
made.
3.1.9 test specimen—any piece of tile whose LRV or color difference from a reference specimen is to be evaluated.
Illing, A. M., Balinkin, I., “Precision in Measurement of Small Color Differences,” American Ceramic Society Bulletin , Vol 44, No. 12, 1965, pp. 956–962.
C609 − 07 (2019)
3.1.10 tile—See Terminology C242.
3.1.11 spectrophotometric—measurement of the spectral reflectance or transmittance curve of a material.
4. Summary of Test Method
4.1 This test method explains the technique for measuring the LRV and color of tile specimens with a spectrophotometric
instrument that meets the specified requirements. Such instruments should give results comparable to differences observed by the
human eye, and yield for each color a unique, three-number characterization, having known relationship to the tristimulus values
X, Y, and Z.
4.2 Spectrophotometic measurement systems commonly provide measurement data in a variety of color units and allow for
automatic conversion of data from one color system to another. Select equations are included in this test method for manual
* * * *
determination of LRV from Y, L or L . Equations are also provided for calculation of L ,a and b and L , a and b from
H H H H
tristimulus values X, Y, Z. The algebraic differences in L, a, and b values, between any two specimens, are then used to calculate
the color difference, ΔE. If manual calculations are required, consult the instrument supplier for conversions not provided within
this test method.
4.3 The complete description of the amount and direction of a color difference between any two pieces of solid colored tile can
be given simply as the three respective differences between the pairs of values for L, a, and b. For some purposes, ΔE alone
provides enough information, since its magnitude gives a fairly good correlation with human opinions about the size of a color
difference.
4.4 To protect against approval of a metameric color match, multiple illuminates must be used when evaluating color difference
between solid colored tiles. A test specimen needs to prove suitable with respect to a reference specimen under incandescent,
fluorescent and daylight illuminant conditions in order to be judged as acceptable.
5. Significance and Use
5.1 This test method describes the means of determining the LRV of a tile specimen. Certain building codes require the use of
materials rated by LRV. Application of this test method provides the means for rating ceramic tile. LRVs reported for ceramic tile
should include reference to the observer and illuminant for which the rating is valid.
5.2 LRV is a property dependent on the overall color of a tile specimen. Control of LRV is achieved through control of color
and adherence to color specifications will govern the acceptability of a product with respect to LRV. Therefore, a product cannot
be judged as having an unacceptable LRV unless the color of the product is found to be unacceptable.
5.3 Mixtures of several tile products are commonly installed on a surface, requiring a means to calculate LRV for a product mix.
The rating obtained for an individual tile product can be used to calculate the LRV for a product mix using the following equation:
LRV 5 p LRV 1p LRV 1….1p LRV (1)
product mix ( 1 1 2 2 n n
where:
n = number of products included in the mix
p = the proportion of the surface area taken up by each product, the sum of p to p must equal one
1 to n 1 n
LRV to n = the LRV for each product used
For example, a mixture of two products is used on a surface. Two thirds of the surface area is covered by product A with a LRV
of 75 %, and one third of the surface is covered by product B with an LRV of 60 % (see Fig. 2). Using the equation, the product
mix is found to have an LRV of 70 %.
5.4 The test method described herein provides instrumental means as the basis for judging color difference. Magnitude of color
difference between pairs of ceramic tile can be determined and expressed in numerical terms.
5.5 Based on interlaboratory investigation, color difference ΔE of plain-colored tile, if determined according to this test
method, should give excellent reproducibility with a standard deviation of not more than σ = 60.15 units. LRV should also give
excellent reproducibility when used for solid colored tile based on the relationship between LRV and either the Y tristimulus or
L value. However, LRV reproducibility for multicolored, speckled, or textured surface tile will be dependent upon the degree of
variation of the tile specimen, and will require a different measurement procedure to minimize the impact of the variation.
5.6 The test method requires the use of multiple illuminants for the determination of color difference between solid-colored tiles.
Evaluation under incandescent, fluorescent and daylight illuminant conditions ensure the color differences calculated between a test
and reference specimen account for the possible occurrence of metamerism.
Billmeyer, F.W. Jr., Saltzman, M., Principles of Color Technology, 2nd Edition, John Wiley & Sons, Inc., New York, NY, 1981 p. 78, 85.
C609 − 07 (2019)
FIG. 2 Example of a Product Mix Used on a Surface
6. Apparatus
6.1 Type of Instrument for LRV Measurement—Any color-measuring spectrophotometric instrument capable of yielding data
that can be transformed mathematically into the International Commission of Illumination (CIE) tristimulus values X, Y, and Z,
may be used. It must have a color difference, ΔE, repeatability (see 3.1.6) of σ = 60.2 units or less, based on five independent
measurements. The well-known standard deviation equation shown as follows is used to calculate the standard deviation.
½
σ5 F X 2 X /N (2)
@ #
~ !
(j j j
6.2 Type of Instrument for Color Measurement—For the measurement of solid colored tile, the spectrophotometric measurement
system must meet all of the requirements for LRV measurement and be capable of yielding tristimulus values X, Y, and Z, for
daylight, incandescent and fluorescent illuminants.
6.3 Instrument Setup—For measurement of LRV and color difference, spectrophotometric measurements should be taken with
specular component included (SCI). If the instrument being used is not capable of taking SCI measurements, then all reported
measurements must include a notation stating measurement obtained with specular component excluded (SCE).
7. Standards
7.1 Primary Standard—The primary standard for reflectance measurement is a layer of freshly prepared barium sulfate (see
Practice E259).
7.2 Working Standard—Because of the difficulty of preparing a primary standard each time and its variability, calibrated pieces
of white opaque glass, porcelain enamel plaques, or glazed ceramic tile are used as working standards and are usually supplied
by the manufacturer of the instrument. The manufacturer of each type of instrument provides numerical specifications for the
working standards, which have a definite relationship to the CIE values X, Y, and Z.
8. Test Specimens
1 1
8.1 Size—The preferred size of test specimens is 4 ⁄4 by 4 ⁄4 in. (108 by 108 mm) because most instruments are equipped with
a holder of that size which assures that the identical surface area may be measured repeatedly. Specimens larger may be reduced
to that size by cutting. The required sample size is dependent on the instrument being used to measure the test and reference
specimens. Many instruments can be configured to measure a sample using different size viewing apertures. The largest area of
view capable of being used without interference from the edges of the tile should be selected. However, the same aperture size
should be used f
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