ASTM D2805-96a(2003)
(Test Method)Standard Test Method for Hiding Power of Paints by Reflectometry
Standard Test Method for Hiding Power of Paints by Reflectometry
SIGNIFICANCE AND USE
This is a precise instrumental method giving results having an absolute physical significance without reference to a comparison paint. It should be used when maximum precision and minimum subjectivity are required, as in testing specification coatings or evaluating the hiding efficiency of pigments.
Hiding power Test Method D 344 is visual instead of instrumental, and gives results that are relative to a material standard instead of absolute. It is less precise than Test Method D 2805 but more closely aligned with practical painting procedures.
SCOPE
1.1 This test method covers the determination, without reference to a material paint standard, of the hiding power of air dry coatings with Y tristimulus values greater than 15%. With appropriate modification, it can also be used to test baking finishes.
1.2 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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Standards Content (Sample)
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Designation: D2805 – 96a (Reapproved 2003)
Standard Test Method for
Hiding Power of Paints by Reflectometry
This standard is issued under the fixed designation D2805; 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.
This standard has been approved for use by agencies of the Department of Defense.
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(whiteorgray)colors,goodagreementhasbeenobtainedwithchromaticpaintsaswell.
Thisisundoubtedlybecausetheexperimentalmeasurementsaremadefairlyclosetothehidingpower
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 D344 Test Method for Relative Hiding Power of Paints by
the Visual Evaluation of Brushouts
1.1 This test method covers the determination, without
D1475 Test Method For Density of Liquid Coatings, Inks,
reference to a material paint standard, of the hiding power of
and Related Products
air dry coatings with Y tristimulus values greater than 15 %.
D3924 Specification for Environment for Conditioning and
With appropriate modification, it can also be used to test
Testing Paint, Varnish, Lacquer, and Related Materials
baking finishes.
E284 Terminology of Appearance
1.2 This standard does not purport to address all of the
E1247 Practice for Detecting Fluorescence in Object-Color
safety concerns, if any, associated with its use. It is the
Specimens by Spectrophotometry
responsibility of the user of this standard to establish appro-
E1331 Test Method for Reflectance Factor and Color by
priate safety and health practices and determine the applica-
Spectrophotometry Using Hemispherical Geometry
bility of regulatory limitations prior to use.
E1347 Test Method for Color and Color-Difference Mea-
2. Referenced Documents
surement by Tristimulus Colorimetry
E1349 Test Method for Reflectance Factor and Color by
2.1 ASTM Standards:
Spectrophotometry Using Bidirectional (45°:0° or 0°:45°)
Geometry
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of
3. Terminology
Subcommittee D01.26 on Optical Properties.
3.1 Definitions—For definitions used in this test method,
Current edition approved May 10, 2003. Published June 2003. Originally
approved in 1969. Last previous edition approved in 1996 as D2805 – 96a. DOI:
see Terminology E284.
10.1520/D2805-96AR03.
3.2 Definitions of Terms Specific to This Standard:
The boldface numbers in parentheses refer to the list of references at the end of
3.2.1 contrast ratio—the ratio of the reflectance of a film on
this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or a black substrate to that of an identical film on a white
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
substrate.
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.
D2805 – 96a (2003)
3.2.1.1 C —the contrast ratio with a white substrate of and minimum subjectivity are required, as in testing specifica-
W
reflectance W. tion coatings or evaluating the hiding efficiency of pigments.
5.2 Hiding power Test Method D344 is visual instead of
Thus: C 5 R /R
W 0 W
instrumental, and gives results that are relative to a material
standard instead of absolute. It is less precise thanTest Method
3.2.1.2 C—the contrast ratio with a white substrate for
D2805 but more closely aligned with practical painting proce-
which W = 0.80.
dures.
Thus: C 5 R /R
0 0.80
6. Apparatus and Materials
3.2.2 reflectance—the daylight luminous diffuse reflectance 6.1 Substrates:
factor (specular reflection excluded). Also referred to in this 6.1.1 Black Glass Panels, minimum size 200 by 200 mm,
test method as the Y-tristimulus value. This value may be and approximately 6-mm thick.
expressed as a percent or a decimal fraction, the latter being 6.1.2 Black and White Paper Charts —The surface shall be
preferred and usually required for mathematical calculations. smooth and level, and impervious to paint liquids. The black
3.2.2.1 reflectivity, R —the reflectance of film thick enough area shall have a maximum reflectance of 1 % and the white
`
to have the same reflectance over both a black and a white area a minimum reflectance of 78 %. The white area shall be
substrate. non-fluorescent, as observed visually under ultra-violet illumi-
3.2.2.2 R —the reflectance of a film on a black surface with nation, or determined in accordance with Practice E1247.
a reflectance of 1 % or less, which is effectively zero for the 6.2 Balance, accurate to 0.1 mg.
purpose of this test. 6.3 Glass Slides—Round or square plates of thickness
3.2.2.3 W—the reflectance of a white substrate. similar to that used for microscope specimen slides, with a
3.2.2.4 R —the reflectance of a film applied on a white minimum area of 40 cm .
W
substrate of reflectance W. 6.4 Reflectance-Measuring Instrument —One that allows
3.2.2.5 R —the reflectance of a film applied on a sub- only diffusely reflected, radiant flux to be incident upon the
0.80
strate having a reflectance of 80 %, which is the standard measuring element. It shall employ a photometric system,
white-substrate reflectance in paint technology. including source, filters, and receptor, that provides a response
3.2.3 scattering coeffıcient, S—the ability of a material to closely similar to the product of the spectral luminous effi-
internallyscatterandtherebyreflectlight;expressedinthistest ciency function of the CIE standard observer and source C.It
method in the same units as spreading rate. shall provide readings to at least the third decimal place and
3.2.4 spreading rate, H—film area per unit volume of permit estimation to the fourth.
7 2
coating, in this test method expressed in square metres per litre 6.5 Template, with a film area approximately 100 cm
(m /L).Itisalsofrequentlyexpressedinsquarefeetpergallon determinedtothenearesttenth.RecordtheexactvalueonLine
(ft /gal). C of the worksheet shown in Fig. 1.
3.2.4.1 spreading rate, H —an experimentally determined 6.6 Doctor Blade Film Applicators, width 150 mm, clear-
X
value of H. ances 50, 75, 100, 125, 150, 175, and 200 µm.
3.2.4.2 spreading rate, H —value of H at a specified
C
NOTE 2—With doctor blades made in the United States, estimate 25
contrast ratio C.
mm/in.and25µm/mil.Bird-typeapplicatorsareusuallymarkedwiththeir
3.2.4.3 hiding power, H —the spreading rate at the con-
half clearance.
0.98
trast ratio C = 0.98.
6.7 Computer and Software, for solving the relevant
NOTE 1—It should be emphasized that a contrast ratio of 0.98 does not
Kubelka-Munk equations.
represent visually complete hiding, nor does it indicate that the same
7. Procedure
contrast ratio holds at every wavelength.
7.1 General Instructions:
4. Summary of Test Method
4.1 The reflectivity R of the coating is determined from
`
The sole source of manufacturer of the black Carrara glass known to the
reflectance measurements on black and white hiding power
committee at this time is The Leneta Co., 15 Whitney Rd., Mahwah, NJ 07430. If
charts.
you are aware of alternative suppliers, please provide this information to ASTM
International Headquarters. Your comments will receive careful consideration at a
4.2 The scattering coefficient S of the coating is determined
meeting of the responsible technical committee, which you may attend.
from R , and the reflectance R and spreading rate H of a film
` 0 X 5
The sole source of manufacturer of the charts known to the committee at this
applied on black glass.
time is the Leneta Co., 15 Whitney Rd., Mahwah, NJ 07430. If you are aware of
4.3 The hiding power, H of the coating is calculated alternative suppliers, please provide this information to ASTM International
0.98
Headquarters.Your comments will receive careful consideration at a meeting of the
from the reflectivity R and the scattering coefficient S.
`
responsible technical committee, which you may attend.
4.4 As an optional procedure the contrast ratio C at a
Conforming with Test Methods E1331, E1347,or E1349. Other methods for
specified spreading rate H is calculated from R and S.
C ` measuring the CIE-Y tristimulus value (specular reflection excluded) are permis-
sible.
5. Significance and Use
The sole source of supply of the template known to the committee at this time
isPaulGardnerCo.,316N.E.FirstSt.,PompanoBeach,FL33061.Ifyouareaware
5.1 This is a precise instrumental method giving results
of alternative suppliers, please provide this information to ASTM International
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 responsible technical committee, which you may attend.
D2805 – 96a (2003)
FIG. 1 Work Sheet Form
7.1.1 Film Application—Make drawdowns manually with a 7.3 Nonvolatile Content, N—Sandwich 0.3 mL of paint
smoothuniformmotion,attherateofabout6cm/s.Holdpaper (dispensed with a 1-mL syringe) between two previously
charts flat by a vacuum plate or other suitable device while weighed slides, squeezing them together so that the paint
maki
...
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