ASTM D7786-12
(Test Method)Standard Test Method for Determining Enamel Holdout
Standard Test Method for Determining Enamel Holdout
SIGNIFICANCE AND USE
This standard may be used by paint companies and raw material suppliers to assess the interactions of primers and topcoats with respect to their ability to provide good enamel holdout. Primer/topcoat systems with the best enamel holdout will result in desirable gloss in the first coat of topcoat application.
SCOPE
1.1 This standard provides a method for determining the holdout characteristics of a primer and topcoat coating application. A standard topcoat is used to determine the absorption characteristics of a primer. Enamel holdout can be measured as a difference in observed gloss of the topcoat over a primer, relative to the gloss of the same topcoat over a non-porous smooth surface.
1.2 The standard is written in the context that the user will be evaluating the enamel holdout characteristics of a primer. Alternatively, the standard may be used as a method to evaluate the enamel holdout characteristics of primer/topcoat system where the primer is constant and different topcoats are used as test paints.
1.3 This standard may also be used for evaluation of paints other than primers as the first coat. In this alteration the user can test the enamel holdout characteristics of a self primed topcoat, or use of any other type of paint as the primer followed by the use of a standard topcoat.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7786 − 12
StandardTest Method for
Determining Enamel Holdout
This standard is issued under the fixed designation D7786; 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 D1640 Test Methods for Drying, Curing, or Film Formation
of Organic Coatings at Room Temperature
1.1 This standard provides a method for determining the
E177 Practice for Use of the Terms Precision and Bias in
holdout characteristics of a primer and topcoat coating appli-
ASTM Test Methods
cation. A standard topcoat is used to determine the absorption
E691 Practice for Conducting an Interlaboratory Study to
characteristics of a primer. Enamel holdout can be measured as
Determine the Precision of a Test Method
a difference in observed gloss of the topcoat over a primer,
relative to the gloss of the same topcoat over a non-porous
3. Terminology
smooth surface.
3.1 Definitions:
1.2 The standard is written in the context that the user will
3.1.1 enamel holdout, n—the ability of a primer/topcoat
be evaluating the enamel holdout characteristics of a primer.
system to retain gloss of the topcoat relative to gloss of the
Alternatively,thestandardmaybeusedasamethodtoevaluate
topcoat over a non-porous smooth surface.
the enamel holdout characteristics of primer/topcoat system
3.1.2 primer, n—an undercoat of paint applied to prepare a
where the primer is constant and different topcoats are used as
surface for final painting.
test paints.
3.1.3 topcoat, n—a coating, intended as the final coat of a
1.3 This standard may also be used for evaluation of paints
finished system, which has the desired appearance and resis-
other than primers as the first coat. In this alteration the user
tance properties as specified by the end user.
can test the enamel holdout characteristics of a self primed
topcoat,oruseofanyothertypeofpaintastheprimerfollowed
4. Summary of Test Method
by the use of a standard topcoat.
4.1 A substrate, preferably a non-porous smooth drawdown
1.4 The values stated in SI units are to be regarded as
card, is coated using a test primer and allowed to dry. The
standard. No other units of measurement are included in this
primer-coated substrate is then coated with the standard top-
standard.
coat and allowed to dry (primed topcoat).
1.5 This standard does not purport to address all of the
4.2 A non-porous smooth substrate is coated using only the
safety concerns, if any, associated with its use. It is the
standard topcoat and allowed to dry (unprimed topcoat).
responsibility of the user of this standard to establish appro-
4.3 Gloss measurements are taken over the primed topcoat
priate safety and health practices and determine the applica-
and also over the unprimed topcoat. The difference in the gloss
bility of regulatory limitations prior to use.
reading between the primed topcoat system and unprimed
topcoat system is an indication of enamel holdout. Smaller
2. Referenced Documents
differences indicate better enamel holdout.
2.1 ASTM Standards:
D523 Test Method for Specular Gloss 5. Significance and Use
D823 Practices for Producing Films of Uniform Thickness
5.1 This standard may be used by paint companies and raw
of Paint, Varnish, and Related Products on Test Panels
material suppliers to assess the interactions of primers and
topcoats with respect to their ability to provide good enamel
holdout. Primer/topcoat systems with the best enamel holdout
This test method is under the jurisdiction of ASTM Committee D01 on Paint
will result in desirable gloss in the first coat of topcoat
and Related Coatings, Materials, andApplications and is the direct responsibility of
application.
Subcommittee D01.42 on Architectural Coatings.
Current edition approved Feb. 1, 2012. Published February 2012. DOI: 10.1520/
6. Apparatus
D7786–12.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.1 Film Applicator, preferably a drawdown bar, capable of
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
applying wet-film thickness of approximately 0.075 mm (3.0
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. mils).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7786 − 12
6.2 If preferred, brush, roller or spray applicators can be
substituted for the drawdown applicators.
6.3 Gloss Meter capable of measuring 20 and 60°gloss.
7. Reagents and Materials
7.1 Substrate Desired for Testing—The preferred substrate
should have a uniform flat surface to enable paint films to be
applied with the preferred drawdown bar applicator. Unless
otherwiseagreedupon,anon-poroussmoothdrawdowncardis
used. Other commonly used substrates include: gypsum panel,
woodordrawdowncardswithnon-porousandporoussections.
The choice to use an alternative substrate often necessitates the
FIG. 1 Diagram of Perpendicular Drawdown Technique
choice of an alternate applicator such as brush, roller or spray.
topcoat that has been applied. This environment and dry time
7.2 Standard Paints—The topcoat will be a mutually agreed
should be the same as in step 9.1.4. Report the environmental
upon standard topcoat. Unless otherwise agreed, use a com-
condition (°C, %RH) and dry time interval.
mercially available latex topcoat which yields a gloss between
40 and 55 when applied in accordance with 9.2.
9.3 Gloss measurement:
9.3.1 Measure the gloss of the topcoat on both the primer/
8. Hazards
topcoat card and the unprimed card. Refer to Test Method
8.1 The user of this test method should refer to appropriate
D523 for the procedure and information related to measuring
MSDS for hazards associated with handling and disposal of
gloss.
paint samples or other laboratory items used as specified in this
9.3.2 Record the average of three readings from each chart.
standard.
Ifthe60°glossoftheunprimedtopcoatisgreaterthan80gloss
units, use the 20° gloss reading; otherwise use the 60° gloss
9. Procedure
reading.
9.1 Application of primer (or other primary coating) and
10. Calculation or Interpretation of Results
topcoat.
9.1.1 Apply the primer onto the selected substrate using the
10.1 Variable Definitions:
film applicator across the full length of the drawdown card or
Enamel Holdout (%retained) = 100*G /G
P U
alternative substrate. Refer to Practices D823, for the proce-
Enamel Holdout (%difference) = 100*(G –G )/G
U P U
dure and information related to the application of films with
Enamel Holdout (difference) = G –G
U P
uniform thickness.
where:
9.1.2 Allow the primer to dry in a controlled environment
G = Gloss of primed topcoat
for an appropriate period of time for the primer that has been
P
G = Gloss of unprimed topcoat
applied. Refer to Test Methods D1640 for the procedure and
U
information related to drying, curing, or film formation of
10.2 Users may choose which calculation to use for report-
organic coatings at room temperature. Report the environmen-
ing enamel holdout, though percent retained is the preferred
tal condition (°C, %RH) and dry time interval.
method.
9.1.3 Using a film applicator capable of applying a wet film
11. Report
thickness of approximately 0.075 mm (3 mils), apply the
standar
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