ASTM D2805-96a

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: D 2805 – 96a
Standard Test Method for
Hiding Power of Paints by Reflectometry
This standard is issued under the fixed designation D 2805; 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 (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Using equations derived from Kubelka-Munk turbid media theory (1-4) (see Annex A1), the
reflectance of a coating can be predicted for any film thickness from measurements made at only one.
On this basis several rapid and accurate test methods (5, 6) have been developed for determining
hiding power. In the past such test methods have been considered difficult due to complexities,
apparent and actual, in the treatment of data. The present test method has been simplified in this
respect, primarily by adapting it fully for computer calculations.
Although the use of broad-band reflectometry makes this test method theoretically valid only for
nonchromatic (white or gray) colors, good agreement has been obtained with chromatic paints as well.
This is undoubtedly because the experimental measurements are made fairly close to the hiding power
end point so that the Kubelka-Munk extrapolation and thus any associated error is relatively small.
This test method is therefore recommended without restriction as to color.
1. Scope E 284 Terminology Relating to Appearance
E 1247 Test Method for Identifying Fluorescence in Object-
1.1 This test method covers the determination, without
Color Specimens by Spectrophotometry
reference to a material paint standard, of the hiding power of
E 1331 Test Method for Reflectance Factor and Color by
air dry coatings with Y tristimulus values greater than 15 %.
Spectrophotometry Using Hemispherical Geometry
With appropriate modification, it can also be used to test
E 1347 Test Method for Color and Color Difference Mea-
baking finishes.
surement by Tristimulus (Filter) Colorimetry
1.2 This standard does not purport to address all of the
E 1349 Test Method for Reflectance Factor and Color by
safety concerns, if any, associated with its use. It is the
Spectrophotometry Using Bi-Directional Geometry
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3. Terminology
bility of regulatory limitations prior to use.
3.1 Definitions—For definitions used in this test method,
2. Referenced Documents see Terminology E 284.
3.2 Definitions of Terms Specific to This Standard:
2.1 ASTM Standards:
3.2.1 contrast ratio—the ratio of the reflectance of a film on
D 344 Test Method for Relative Hiding Power of Paints by
a black substrate to that of an identical film on a white
the Visual Evaluation of Brushouts
substrate.
D 1475 Test Method for Density of Paint, Varnish, Lacquer,
3.2.1.1 C —the contrast ratio with a white substrate of
W
and Related Products
reflectance W.
D 3924 Specification for Standard Environment for Condi-
tioning and Testing Paint, Varnish, Lacquer, and Related Thus: C 5 R /R
W 0 W
Materials
3.2.1.2 C—the contrast ratio with a white substrate for
which W = 0.80.
This test method is under the jurisdiction of ASTM Committee D-1 on Paint
and Related Coatings, Materials, and Applications and is the direct responsibility of Thus: C 5 R /R
0 0.80
Subcommittee D01.26 on Optical Properties.
Current edition approved Dec. 10, 1996. Published February 1997. Originally
3.2.2 reflectance—the daylight luminous diffuse reflectance
published as D 2805 – 69 T. Last previous edition D 2805 – 96.
The boldface numbers in parentheses refer to the list of references at the end of factor (specular reflection excluded). Also referred to in this
this standard.
test method as the Y-tristimulus value. This value may be
Annual Book of ASTM Standards, Vol 06.01.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 2805 – 96a
expressed as a percent or a decimal fraction, the latter being 6.1.1 Black Glass Panels, minimum size 200 by 200 mm,
preferred and usually required for mathematical calculations. and approximately 6-mm thick.
6.1.2 Black and White Paper Charts —The surface shall be
3.2.2.1 reflectivity, R —the reflectance of film thick enough
‘
smooth and level, and impervious to paint liquids. The black
to have the same reflectance over both a black and a white
substrate. area shall have a maximum reflectance of 1 % and the white
area a minimum reflectance of 78 %. The white area shall be
3.2.2.2 R —the reflectance of a film on a black surface with
non-fluorescent, as observed visually under ultra-violet illumi-
a reflectance of 1 % or less, which is effectively zero for the
nation, or determined in accordance with Test Method E 1247.
purpose of this test.
6.2 Balance, accurate to 0.1 mg.
3.2.2.3 W—the reflectance of a white substrate.
6.3 Glass Slides—Round or square plates of thickness
3.2.2.4 R —the reflectance of a film applied on a white
W
similar to that used for microscope specimen slides, with a
substrate of reflectance W.
minimum area of 40 cm .
3.2.2.5 R —the reflectance of a film applied on a sub-
0.80
6.4 Reflectance-Measuring Instrument —One that allows
strate having a reflectance of 80 %, which is the standard
only diffusely reflected, radiant flux to be incident upon the
white-substrate reflectance in paint technology.
measuring element. It shall employ a photometric system,
3.2.3 scattering coeffıcient, S—the ability of a material to
including source, filters, and receptor, that provides a response
internally scatter and thereby reflect light; expressed in this test
closely similar to the product of the spectral luminous effi-
method in the same units as spreading rate.
ciency function of the CIE standard observer and source C.It
3.2.4 spreading rate, H—film area per unit volume of
shall provide readings to at least the third decimal place and
coating, in this test method expressed in square metres per litre
2 permit estimation to the fourth.
(m /L). It is also frequently expressed in square feet per gallon
2 6.5 Template, with a film area approximately 100 cm
(ft /gal).
determined to the nearest tenth. Record the exact value on Line
3.2.4.1 spreading rate, H —an experimentally determined
X
C of the worksheet shown in Fig. 1.
value of H.
6.6 Doctor Blade Film Applicators, width 150 mm, clear-
3.2.4.2 spreading rate, H —value of H at a specified
C
ances 50, 75, 100, 125, 150, 175, and 200 μm.
contrast ratio C.
NOTE 2—With doctor blades made in the United States, estimate 25
3.2.4.3 hiding power, H —the spreading rate at the con-
0.98
mm/in. and 25 μm/mil. Bird-type applicators are usually marked with their
trast ratio C = 0.98.
half clearance.
NOTE 1—It should be emphasized that a contrast ratio of 0.98 does not
6.7 Computer and Software, for solving the relevant
represent visually complete hiding, nor does it indicate that the same
Kubelka-Munk equations.
contrast ratio holds at every wavelength.
7. Procedure
4. Summary of Test Method
7.1 General Instructions:
4.1 The reflectivity R of the coating is determined from
‘
7.1.1 Film Application—Make drawdowns manually with a
reflectance measurements on black and white hiding power
smooth uniform motion, at the rate of about 6 cm/s. Hold paper
charts.
charts flat by a vacuum plate or other suitable device while
4.2 The scattering coefficient S of the coating is determined
making drawdowns.
from R , and the reflectance R and spreading rate H of a film
‘ 0 X
7.1.2 Reflectance Measurements—Measure the reflectance
applied on black glass.
of each test area at a minimum of three locations, reading or
4.3 The hiding power, H of the coating is calculated
0.98
estimating to four decimal places and calculating mean values
from the reflectivity R and the scattering coefficient S.
‘
to the same. Place charts over a white surface and black glass
4.4 As an optional procedure the contrast ratio C at a
over a black surface while measurements are being made.
specified spreading rate H is calculated from R and S.
C ‘
5. Significance and Use
The sole source of manufacturer of the black Carrara glass known to the
committee at this time is The Leneta Co., 15 Whitney Rd., Mahwah, NJ 07430. If
5.1 This is a precise instrumental method giving results
you are aware of alternative suppliers, please provide this information to ASTM
having an absolute physical significance without reference to a
Headquarters. Your comments will receive careful consideration at a meeting of the
comparison paint. It should be used when maximum precision 1
responsible technical committee, which you may attend.
and minimum subjectivity are required, as in testing specifica- The sole source of manufacturer of the charts known to the committee at this
time is the Leneta Co., 15 Whitney Rd., Mahwah, NJ 07430. If you are aware of
tion coatings or evaluating the hiding efficiency of pigments.
alternative suppliers, please provide this information to ASTM Headquarters. Your
5.2 Hiding power Test Method D 344 is visual instead of
comments will receive careful consideration at a meeting of the responsible
instrumental, and gives results that are relative to a material
technical committee, which you may attend.
Conforming with Test Methods E 1331, E 1347, or E 1349. Other methods for
standard instead of absolute. It is less precise than Test Method
measuring the CIE-Y tristimulus value (specular reflection excluded) are permis-
D 2805 but more closely aligned with practical painting
sible.
procedures. 7
The sole source of supply of the template known to the committee at this time
is Paul Gardner Co., 316 N. E. First St., Pompano Beach, FL 33061. If you are aware
of alternative suppliers, please provide this information to ASTM Headquarters.
6. Apparatus and Materials
Your comments will receive careful consideration at a meeting of the responsible
6.1 Substrates: technical committee, which you may attend.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 2805 – 96a
FIG. 1 Work Sheet Form
7.1.3 Record Keeping—Record all data on a copy of the calculate the nonvolatile content of the paint as a
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