ASTM C609-07(2014)
(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 %.
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. LRV should also give excellent reproducibility when u...
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:C609 −07 (Reapproved 2014)
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 2. Referenced Documents
1.1 This test method covers the measurement of Light 2.1 ASTM Standards:
Reflectance Value (LRV) and visually small color difference C242 Terminology of Ceramic Whitewares and Related
between pieces of glazed or unglazed ceramic tile, using any Products
spectrophotometer that meets the requirements specified in the D2244 Practice for Calculation of Color Tolerances and
test method. LRV and the magnitude and direction of the color Color Differences from Instrumentally Measured Color
difference are expressed numerically, with sufficient accuracy Coordinates
for use in product specification. E259 Practice for Preparation of Pressed Powder White
Reflectance Factor Transfer Standards for Hemispherical
1.2 LRV may be measured for either solid-colored tile or
and Bi-Directional Geometries
tile having a multicolored, speckled, or textured surface. For
E284 Terminology of Appearance
tile that are not solid-colored, an average reading should be
obtained from multiple measurements taken in a pattern
3. Terminology
representative of the overall sample as described in 9.2 of this
3.1 Definitions:
test method. Small color difference between tiles should only
*
3.1.1 color difference, ∆E and ∆E —the vector sum of the
H
be measured for solid-color tiles. Small color difference
* * * *
three component differences ∆L , ∆a , and ∆b for ∆E and
between tile that have a multicolored, speckled, or textured
∆L ,∆a ,∆b for ∆E . The superscript * indicates color
H H H H
surface, are not valid.
difference based on the use of CIELAB color space equations,
1.3 For solid colored tile, a comparison of the test specimen
while the subscript H indicates color difference based on the
and reference specimen should be made under incandescent,
useoftheHunterequations. ∆E isexpressedinunitsofjudds,
H
*
fluorescent and daylight illuminant conditions. The use of
while ∆E is a unit-less value. Either form of the ∆E can be
multiple illuminants allows the color difference measurement
solved for using the equation shown in 10.3. For both the
tobemadewithouttheriskofwronglyacceptingamatchwhen
CIELAB and Hunter equations, the values ∆ L, ∆a, and ∆b are
the tiles being compared are metamers. (See 3.1.4.)
obtained by calculating the component differences as follows:
1.4 The values stated in inch-pound units are to be regarded
∆L 5 L 2 L
t r
as the standard. The values given in parentheses are for
∆a 5 a 2 a
t r
information only.
∆b 5 b 2 b
t r
1.5 This standard does not purport to address all of the
where:
safety concerns, if any, associated with its use. It is the
t = test specimen, and
responsibility of the user of this standard to establish appro-
r = reference specimen.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. The quantity ∆E 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
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 Jan. 1, 2014. Published February 2014. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1967. Last previous edition approved in 2007 as C609 – 07. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C0609-07R14. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C609−07 (2014)
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 (2014)
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
...
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