ASTM D7488-11(2024)

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.
Designation: D7488 − 11 (Reapproved 2024)
Standard Test Method for
Open Time of Latex Paints
This standard is issued under the fixed designation D7488; 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 first coat becoming visible and allowing for repair within the
previously painted area.
1.1 This test method covers a procedure to determine the
length of time a latex paint remains “wet” or “open” enough to
4. Summary of Test Method
allow for brush-in and repair.
4.1 Since environmental conditions such as temperature,
1.2 This standard does not purport to address all of the
humidity and air flow can result in variable results, it is
safety concerns, if any, associated with its use. It is the
recommended that this test method be performed in a constant
responsibility of the user of this standard to establish appro-
temperature / humidity room (23 °C 6 2 °C (73.5 °F 6
priate safety, health, and environmental practices and deter-
3.5 °F)) / 50 % 6 5 % relative humidity. Test paints are applied
mine the applicability of regulatory limitations prior to use.
to the center of a sealed chart with a 76 microns (3 mil) wet
1.3 This international standard was developed in accor-
film thickness. X marks are made immediately. The number of
dance with internationally recognized principles on standard-
X marks will depend on how many can fit on one drawdown
ization established in the Decision on Principles for the
(see Fig. 1). The test paint is then applied in perpendicular
Development of International Standards, Guides and Recom-
sections, brushing each section across the initial painted
mendations issued by the World Trade Organization Technical
section. The perpendicular sections are repeated at agreed upon
Barriers to Trade (TBT) Committee.
time intervals. After drying, wet edge is recorded as the last
time the test paint could be brushed into the initial painted
2. Referenced Documents
2 section without the edges of the first coat being visible. The
2.1 ASTM Standards:
time at which the X marks become visible is also noted.
D3924 Specification for Standard Environment for Condi-
tioning and Testing Paint, Varnish, Lacquer, and Related
5. Significance and Use
Materials
5.1 Latex paints dry very quickly which often causes
D5068 Practice for Preparation of Paint Brushes for Evalu-
ation difficulty in final appearance of painted areas, especially paints
formulated below 100g/L VOC where lower amounts of
D5301 Practice for Physical Characterization of Paint
Brushes solvents are in the formulated latex paint. This method is a
means of determining the time available before a test paint
E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods cannot be worked into a previously painted area.
E691 Practice for Conducting an Interlaboratory Study to
6. Apparatus
Determine the Precision of a Test Method
6.1 Constant Temperature/Humidity Room (23 °C 6 2 °C
3. Terminology
(73.5 °F 6 3.5 °F)) / 50 % 6 5 % relative humidity in
3.1 Definitions:
accordance with Specification D3924.
3.1.1 open time, n—the length of time a coating remains wet
6.2 Contrasting Sealed Chart (that is, black sealed chart for
or open enough to allow for brush-in without the edges of the
white paints or white sealed chart for tinted paints), typically
30 cm by 60 cm (1 ft by 2 ft.).
This test method is under the jurisdiction of ASTM Committee D01 on Paint
6.3 Glass Plate, 30 cm by 60 cm (1 ft by 2 ft) or vacuum
and Related Coatings, Materials, and Applications and is the direct responsibility of
plate.
Subcommittee D01.42 on Architectural Coatings.
Current edition approved Feb. 1, 2024. Published February 2024. Originally 6.3.1 If using a glass plate, tape to secure sealed chart to
approved in 2010. Last previous edition approved in 2016 as D7488 – 11 (2016).
glass plate.
DOI: 10.1520/D7488-11R24.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 6.4 Good Quality Brush, 50 mm (2 in.) wide with straight
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
edge, polyester bristles in accordance with Practice D5301.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 6.5 Timer or Clock to record time intervals.
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D7488 − 11 (2024)
mark, ensure that the X marks are consistent in size down the chart and
throughout your testing.
7.6 Re-wet the brush by dipping it into the test paint.
Remove excess paint by lightly scraping both sides of the brush
across the top edge of the can.
NOTE 2—The objective is to keep the brush wet; but not to add
significantly more paint to the area being tested.
7.7 At agreed upon time intervals between each X mark,
start brushing the first X mark in perpendicular direction to the
initial drawdown using ten strokes back and forth (1 stroke =
1 back and forth motion) to work the brush-applied paint into
the drawdown area. The length of the strokes should be slightly
less than the width of the chart and moving across and pass the
initial drawdown to determine the time elapsed when the edges
of the first coat become visible.
7.8 Repeat 7.6 and 7.7 by moving sequentially down the
chart to each X mark at the agreed upon time interval. (For
example, 2 minute intervals from 8 to 14 minutes.)
7.9 Dry the chart in a horizontal position overnight.
7.10 After drying overnight, observ
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