ASTM D2793-99

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Designation:D2793–99
Standard Test Method for
Block Resistance of Organic Coatings on Wood Panel
Substrates
This standard is issued under the fixed designation D 2793; 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.
1. Scope of these painted substrates is formed and subjected to a
specified pressure and temperature for a sufficient time to
1.1 This test method covers the determination of the block
develop any sticking tendencies that exist. The pressure is
resistance of organic coatings on wood and wood-based panel
released and the painted surfaces are examined for any signs of
substrates. Block resistance is the ability of a coating to resist
sticking or pressure mottling. If blocking (forming a block by
sticking to another surface and to resist any change in
panels sticking together) occurs, the material is unsatisfactory.
appearance when it is pressed against that surface for a
If no sticking or damage to the film surface occurs, the material
prolonged period of time.
is satisfactory.
1.2 General methods for determining block resistance are
3.2 When the conditions of production finishing are estab-
outlined in Sections 6 and 7. Variations inherent in user
lishedandknown,themethodofapplication,thesubstrate,film
materials and procedures, however, may dictate adjustments to
thickness, and cure of the film should duplicate these condi-
the general method to improve accuracy. Paragraphs 7.3 and
tions as closely as possible. However, some acceleration of the
7.4 provide guidelines for tailoring the general procedure to a
test may be possible with more severe conditions.
user’s specific application. Paragraph 7.5 offers a rating meth-
odology.
4. Significance and Use
1.3 Test Method D 2091 should be used for the determina-
4.1 Coated wood panel products must be stacked face to
tionofprintresistanceorpressuremottlingoforganiccoatings,
face or face to back during warehousing, packaging, and
particularly lacquers, applied to wood-based case goods such
transportation without the coated finish sticking (blocking) and
as furniture.
becoming damaged. This test method describes a laboratory
1.4 The values stated in inch-pound units are to be regarded
means of evaluating conditions of blocking using factors of
as the standard. The values given in parentheses are for
pressure, heat, time and moisture.
information only.
4.2 Degrees of hardness or degrees of cure of organic
1.5 This standard does not purport to address all of the
coatings, or both, can be evaluated using a blocking test.
safety concerns, if any, associated with its use. It is the
4.3 The rate of volatile loss (drying speed) of organic
responsibility of the user of this standard to establish appro-
coatings can be evaluated using a blocking test.
priate safety and health practices and determine the applica-
4.4 The effectiveness of protective packaging materials (slip
bility of regulatory limitations prior to use.
sheets) for organic coatings on wood substrates can be evalu-
2. Referenced Documents ated using a blocking test.
2.1 ASTM Standards:
5. Apparatus
D 2091 Test Method for Print Resistance of Lacquers
5.1 Hydraulic Press (preferably constant pressure), ca-
3. Summary of Test Method pable of maintaining the agreed upon stacking pressure.
5.2 Rigid Platens, at least 4 in. (100 mm) square, capable of
3.1 The coatings are prepared for testing in a manner
being maintained at the desired test temperature.
duplicating production application and curing conditions as
nearlyaspossibleonthespecifiedwoodsubstrate.Thenastack
6. Test Specimens
6.1 For those cases where the intended use conditions are
This test method is under the jurisdiction of ASTM Committee D-1 on Paint not established or known, the following specifications or some
and Related Coatings, Materials, andApplications and is the direct responsibility of
set of specifications agreed upon between the purchaser and
Subcommittee D01.52 on Factory-Coated Wood Products.
seller apply:
Current edition approved May 10, 1999. Published July 1999. Originally
6.1.1 The test coating shall be applied by spray to a panel.
published as D 2793 – 69. Last previous edition D 2793 – 93a.
Annual Book of ASTM Standards, Vol 06.02.
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D2793
6.1.2 The panel shall be a piece of ⁄4 in. (6.4 mm) smooth this should be compensated for by use of higher platen
two side (S2S) standard hardboard or other thickness and type pressures or by the inclusion of stringer rods in the sample
of wood substrate. stack.
7.4 If the presence of water between substrate surfaces can
6.1.3 The dry film thickness of pigmented coatings shall be
belogicallyanticipatedasaresultofthemanufacturingprocess
1.5 6 0.2 mils (38 6 5 µm), and of clear coatings, shall be 1.2
or storage conditions, include it in the procedure, as blocking
6 0.2 mils (30 6 5 µm) or other agreed upon film thickness.
tendencies may be altered. Systematic coated surface wetting
Cure of the coating shall be as agreed and should be standard-
prior to test such as contact with saturated toweling, or
ized for each coating.
conditioning at elevated relative humidity conditions, can be
NOTE 1—Film thickness can be measured by weight differences before
useful in improving test efficacy.
and after painting, but this requires careful conditioning of the substrate
7.5 At test conclusion, open the press and pick up the stack
under standard temperature and humidity conditions prior to each weigh-
in such a fashion that first the bottom panel, then the next to
ing. Film thickness can also be determined by using an aluminum tab
bottom panel, and eventually all the panels are allowed to free
alongside the test panel and measuring the film thickness with a standard
eddy-current gage or using a steel panel with a magnetic film thickness fall of their own weight. Sample pairs that do not separate via
gage.Alternatively, on smooth surface boards, a draw down bar applicator
free fall will be set aside to be separated by hand. If desired, a
with known film
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