ASTM D358-98
(Specification)Standard Specification for Wood to Be Used as Panels in Weathering Tests of Coatings
Standard Specification for Wood to Be Used as Panels in Weathering Tests of Coatings
SCOPE
1.1 This specification designates woods for weathering tests of exterior solvent-borne or water-borne paints and other materials of similar purpose. Such tests may include either outdoor exposure tests or accelerated laboratory tests. It is the purpose of this specification to minimize the influence of variation of wood of a given species on test results.
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Designation: D 358 – 98
Standard Specification for
Wood to Be Used as Panels in Weathering Tests of
Coatings
This standard is issued under the fixed designation D 358; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope wide surface of the piece are said to be flat-sawn or flat-
grained; those with the rings intersecting at angles between 30°
1.1 This specification designates woods for weathering tests
and 60° are termed bastard-sawn; and those with angles greater
of exterior solvent-borne or water-borne paints and other
than 60° are termed quarter-sawn, edge grain, or vertical grain.
materials of similar purpose. Such tests may include either
3.3 Some industrial processors of wood products may uti-
outdoor exposure tests or accelerated laboratory tests. It is the
lize wood at moisture levels significantly higher than the
purpose of this specification to minimize the influence of
equilibrium moistures cited in this specification. In these
variation of wood of a given species on test results.
specific cases, appropriately higher moisture content panels
1.2 The values stated in inch/pound units are to be regarded
may be prepared for testing of factory applied finishes.
as the standard. The values given in parentheses are for
information only.
WESTERN RED CEDAR
2. Referenced Documents
4. Species
2.1 ASTM Standards:
4.1 The material for test panels shall be western red cedar
D 3924 Specification for Standard Environment for Condi-
(Thuja plicata).
tioning and Testing Paint, Varnish, Lacquers, and Related
Materials
5. Weight per Volume
5.1 When the wood is in equilibrium with air at 60 to 65 %
3. General Considerations
relative humidity and 70 6 1°F (21 6 0.5°C) it shall weigh 22
3.1 A variety of different species should be used for testing
3 3
to23lb/ft (350to370kg/m )orat50 65 %relativehumidity
finishes because of the wide variations in the anatomy and the
and 73.5 6 3.5°F (23 6 2°C), which are specified in
density between wood species. The factors have tremendous
Specification D 3924 as standard conditions for testing paint
influences on finish performance. Latewood band width and
and related coatings, it shall weigh 21.4 to 22.4 lb/ft (343 to
density are especially important to finish performance, and
359 kg/m ).
these parameters vary significantly between wood species.
NOTE 1—The density requirement is to eliminate wood specimens that
Cedar and redwood have relatively low proportions of hard
varygreatlyfromtheaverageforthatspecies.Eithersetofconditionsmay
summerwood distributed in narrow bands and contain extrac-
be used to establish the density.At 60 to 65 % relative humidity wood has
tives that discolor some paint films. Southern pine has a large
a moisture content of approximately 12 % while at 45 to 55 % relative
proportion of hard summerwood in wide bands.
humidity it contains 9 to 10 %. The former is closer to the moisture
3.2 The angle between the growth rings and the surface of
content of wood exposed to most exterior climatic conditions.
the specimen is very critical to finish performance. Commer-
6. Character of Wood
cial practice utilizes the following classification system.
Boards in which growth form an angle of less than 30° with the
6.1 The wood shall be heartwood having edge grain and
shall be free of knots and other defects. The color of the wood
shall be uniform across each panel with no streaks that are
This specification is under the jurisdiction of ASTM Committee D1 on Paint
excessively light or dark. The number of annual growth rings
and Related Coatings, Materials, and Applications and is the direct responsibility
per inch along the radius of the log from which the wood was
D01.42 on Architectural Coatings.
Current edition approved May 10, 1998. Published August 1998. Originally
obtained shall not be less than ten. The surfaces shall be
published as D 358 – 33. Last previous edition D 358 – 93.
Annual Book of ASTM Standards, Vol 06.01.
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D358–98
smoothly planed and sanded thoroughly with 150 grit sandpa- 13. Weight per Volume
per within two weeks of testing.
13.1 When the wood is in equilibrium with air at 60 to 65 %
relative humidity and 70 6 1°F (21 6 0.5°C) it shall weigh 32
7. Thickness of Panels
3 3
to38lb/ft (510to610kg/m )orat50 65 %relativehumidity
7.1 The minimum thicknesses (Note 2) in proportion to
and 73.5 6 3.5°F (23 6 2°C) it shall weigh 31 to 37 lb/ft (500
width (across the grain) shall be as follows:
to 590 kg/m ). (See Note 2.)
Minimum Thickness, in.
Panel Width, in. (mm) (mm)
14. Character of Wood
14.1 The wood shall be free of knots, pitch pockets, and
Less than 3 (less than 75) ⁄8 (10)
3 to 6 (75 to 150) ⁄16 (11)
other defects. The color of the wood shall be uniform across
Over 6 (over 150) ⁄4 (19)
each panel with no streaks that are excessively light or dark.
NOTE 2—Minimum thicknesses in proportion to width (across the
Thenumberofannualgrowthringsperinchalongtheradiusof
grain) do not apply to panels made of clapboard or siding of commercial
the log from which the wood was obtained shall be not less
types, which shall be used as regularly marketed.
than 4 nor more than 12.The surfaces shall be smoothly planed
and sanded thoroughly with 150 grit sandpaper within two
WHITE PINEAND PONDEROSAPINE
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