ASTM D4442-92(1997)e1
(Test Method)Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Base Materials
Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Base Materials
SCOPE
1.1 These test methods cover the determination of the moisture content ( MC ) of solid wood, veneer, and other wood-base materials, including those that contain adhesives and chemical additives. The test methods below describe primary (A) and secondary (B through D) procedures to measure moisture content:
General Information
Relations
Standards Content (Sample)
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e1
Designation: D 4442 – 92 (Reapproved 1997)
Standard Test Methods for
Direct Moisture Content Measurement of Wood and
Wood-Base Materials
This standard is issued under the fixed designation D 4442; 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.
e NOTE—Section 9, Keywords, was added editorially in March 1997.
1. Scope 2. Referenced Documents
1.1 These test methods cover the determination of the 2.1 ASTM Standards:
moisture content (MC) of solid wood, veneer, and other D 9 Terminology Relating to Wood
wood-base materials, including those that contain adhesives D 4933 Guide for Moisure Conditioning of Wood and
and chemical additives. The test methods below describe Wood-Base Materials
primary (A) and secondary (B through D) procedures to
3. Terminology
measure moisture content:
3.1 Definition:
Method A—Primary Oven-Drying Method
Method B—Secondary Oven-Drying Method
3.1.1 moisture content—the amount of water contained in
Method C—Distillation (Secondary) Method
the wood, usually expressed as a percentage of the mass of the
Method D—Other Secondary Methods.
oven-dry wood (in accordance with Terminology D 9).
1.2 The primary oven-drying method (Method A) is in-
3.1.1.1 Discussion—The moisture content of wood or other
tended as the sole primary method. It is structured for research
wood-based materials can be expressed on either as a percent-
purposes where the highest accuracy or degree of precision is
age of oven-dry mass of the sample (oven-dry basis) or as a
needed.
percentage of initial mass (wet basis). The methods described
1.3 The secondary methods (B through D) are intended for
in this standard refer to the oven-dry basis. Because oven-dry
special purposes or under circumstances where the primary
mass is used, moisture content values may exceed 100 %. The
procedure is not desired or justified. In these procedures,
term moisture content when used with wood-based materials
moisture content values cannot be reported with an accuracy
can be misleading since untreated wood frequently contains
greater than integer percentage values. However, a greater
varying amounts of volatile compounds (extractives which are
level of accuracy may be reported if the appropriate primary
evaporated when determining moisture content). Definition of
procedures are used.
the moisture content of wood is further complicated when
1.4 Distillation (secondary) method is intended for use with
determined by a thermal method because of thermal degrada-
materials that have been chemically treated or impregnated
tion, which causes the final moisture-free mass to decrease
such that the oven-drying procedures introduce greater error
from small but continuous losses.
than desired in the results.
1.5 This standard does not purport to address all of the 4. Significance and Use
safety concerns, if any, associated with its use. It is the
4.1 Moisture content is one of the most important variables
responsibility of the user of this standard to establish appro-
affecting the properties of wood and wood-base materials. The
priate safety and health practices and determine the applica-
procedures in these test methods are structured to permit the
bility of regulatory limitations prior to use.
full range of use from fundamental research to industrial
processing. Method A is designed for obtaining the most
precise values of moisture content consistent with the needs of
the user. It also provides means of assessing variability
These test methods are under the jurisdiction of ASTM Committee D-7 on
contributed by the oven or specimen hygroscopicity, or both. In
Wood and are the direct responsibility of Subcommittee D07.01 on Fundamental
addition, criteria are described for defining the endpoint in
Test Methods and Properties.
Current edition approved Feb. 15, 1992. Published April 1992. Originally
oven-drying. Method A is the reference (primary) standard for
published as D 4442 – 84. Last previous edition D 4442 – 84.
These test methods replace, in part, Test Methods D 2016, for Moisture Content
of Wood, discontinued 1989.
Annual Book of ASTM Standards, Vol 04.10.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4442
determining moisture content of wood and wood-base materi- and depth of the oven cavity. With this scheme four samples
als. Methods B through D are secondary methods to permit will be positioned on each of two shelves at one third and two
relatively simple procedures of measuring moisture content, thirds of the cavity height.
but with less precision than Method A. However, greater 5.3.2 Determination of Combined Specimen and Oven
precision may be obtained with supporting data by using the Variability—Procedures are the same as 5.3.1.1-5.3.1.3 except
appropriate procedures in Method A. that specimens of any origin and size or shape can be used.
Calculate variability by the equation in 5.5.2.
5. Method A—Oven-Drying (Primary)
5.3.3 Procedure—Use the primary oven-drying procedure
5.1 Apparatus:
(5.4).
5.1.1 Oven—A forced-convection oven that can be main-
5.4 Procedure:
tained at a temperature of 103 6 2°C throughout the drying
5.4.1 Specimens to be equilibrated shall be processed as in
chamber for the time required to dry the specimen to the
Guide D 4933.
endpoint shall be used. Ovens shall be vented to allow the
5.4.2 Store specimens in individual vapor-tight containers if
evaporated moisture to escape.
any delay could occur between sampling and weighing.
NOTE 1—The ratio of sample mass to chamber volume and the air 5.4.3 Weigh the specimens using a balance consistent with
velocity within the oven are not critical as long as temperature and relative
the desired precision (see 5.1.2).
humidity within the oven are constant. Room relative humidity should be
5.4.4 Place specimens in the oven within the volume tested
less than 70 % relative humidity, at which condition the oven is at 1.7 %
for oven precision.
relative humidity. For best precision, drying should be carried out in a
5.4.5 Endpoint—Assume that the endpoint has been
constant relative humidity room with the relative humidity as low as
reached when the mass loss in a 3-h interval is equal to or less
possible.
than twice the selected balance sensitivity. For example, with a
5.1.2 Balance—Based on a 10-g (oven-dry) specimen,
10-g (oven-dry) specimen, the balance sensitivity for 0.01 %
minimum readability of the balance shall be determined by the
MC precision is 0.1 mg (see 5.1.2), therefore, dry to 0.2 mg or
desired reporting level of precision:
less mass loss in a 3-h period.
Reporting Precision Level, MC, % Minimum Balance Readability, mg
5.4.6 Handling and Weighing Procedures—Dried samples
shall be stored in a desiccator with fresh desiccant until they
0.01 1
0.05 5
have reached room temperature. All weighings shall be carried
0.1 10
out using closed weighing jars.
0.5 50
5.5 Calculations:
1.0 100
5.5.1 Calculate moisture content as follows:
For other oven-dry mass levels, the sensitivity requirement
MC,% 5 A 2 B /B 3 100 (1)
~ !
shall be scaled appropriately.
5.2 Test Material—Any conveniently sized wood or wood-
where:
based material can be used, consistent with the use of closed
A = original mass, g, and
weighing jars (5.4.6) and the balance readability (5.1.2).
B = oven-dry mass, g.
NOTE 2—If specimens contain any degree of volatilizable material Example—A specimen of wood weighs 56.70 g. After oven-
other than water, it may be necessary to either use Method C or run
drying, the mass is 52.30 g.
Method A and C concurrently.
MC,% 5 ~56.70 2 52.30!/52.30 3 100 (2)
5.3 Calibration and Standardization—Determination of
5 ~4.40/52.30! 3 100 5 8.4 % (2)
specimen variability requires a separate measurement of the
NOTE 3—If wood has been treated with a nonvolatile chemical and if
contribution of variability within the oven.
the mass of the retained chemical is known, the moisture content may be
5.3.1 Determination of Oven Variability—This section per-
determined as follows:
mits a separate evaluation of the oven variability from that of
MC,% 5 ~A 2 B!/D 3 100 (3)
specimens distributed in the oven.
5.3.1.1 Specimen Selection and Preparation—Douglas-fir
shall be ground to sawdust and that fraction contained in a
40/60 mesh screen used. The sample origin or drying history is
where:
D = B minus mass of retained chemical in sample.
not critical. The sawdust shall be tumbled in a closed container
until thoroughly mixed. All replicates shall be prepared at the
5.5.2 Calculate variance of the specimens as follows:
same time from the same batch of material. All material shall
2 2 ½
S 5 S 2 S (4)
~ !
w ow o
be transferred and stored in air-tight weighing jars.
5.3.1.2 Equilibration—The moisture content of the speci-
where:
men is not important if the preparation techniques described
S = specimen material variance,
w
under 5.3.1.1 are used. Equilibration is not required, although
S = oven variance (from 5.3.1), and
o
it is preferable that the material be as uniform as possible in S = combined specimen and oven variance (5.3.2).
ow
moisture content. 5.6 Report—Report the following information: nominal
5.3.1.3 Number and Location of Specimens—Each test shall oven-dry mass, type of material, oven variance, specimen
consist of a set of eight replicated specimens. These shall be variance, balance sensitivity, oven model and type, and any
located at third-point positions with respect to height, width, deviation from the prescribed method. The number of decimal
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4442
NOTE 6—If wood has been treated with a nonvolatile chemical and if
places reported shall not exceed the precision level (5.1.2).
the mass of the retained chemical is known, the moisture content may be
5.7 Precision and Bias:
determined as follows:
5.7.1 Precision of Measurement—By definition, the accu-
racy of measurement has been set equal to the determined
MC,% 5 ~A 2 B!/D 3 100 (7)
precision of test measurement, that is, there is no assumed bias
where:
of measurement due to the inability to accurately assess
D = B minus the mass of retained chemical in sample.
moisture content. With this approach the actual accuracy may
be poorer than the stated accuracy. At this time, no data are 6.6 Report—Report the following information: Mean, stan-
dard deviation, number of specimens, and any deviation from
available from which to report typical variances in ovens or
from specimen material. the method. Moisture content values shall be integer only (see
6.7.1).
6. Method B—Oven-Drying (Secondary)
6.7 Precision and Bias:
6.1 Apparatus:
6.7.1 The precision is assumed to be no greater than6 1%
6.1.1 Oven—An oven that can maintain 103 6 2°C near the
moisture content for any measurement unless the appropriate
drying endpoint shall be used.
procedures in Section 5 are used.
6.1.2 Balance—The sensitivity shall be a minimum of
6.7.2 No bias calculations may be made from this proce-
0.1 % of the nominal oven-dry mass of the specimen (see
dure.
5.1.2).
6.2 Test Material—Any conveniently sized wood or wood-
7. Method C—Distillation
based material can be used, however, the balance readability
7.1 Apparatus:
shall be consistent with the desired precision (see 5.1.2 and
7.1.1 Extraction Flask—A 500-mL flask and thimble
5.3).
holder, as shown in Fig. 1. The flask and holder may be
NOTE 4—If specimens contain any degree of volatilizable material
combined in one unit.
other than water, it may be necessary to either use Method C, or run
7.1.2 Condenser—A water-cooler condenser of the cold-
Methods B and C concurrently.
finger type, as shown in Fig. 1, or of the straight-tube, Liebig
6.3 Calibration and Standardization—No specific tests are
type.
required unless greater precision than integer moisture content
7.1.3 Water Trap—A glass tube preferably having an inside
values are desired. See 6.7.
diameter of 9 to 10 mm and sealed at one end. If a trap with
6.4 Procedure:
stopcock is used, the stopcock shall be securely fastened in
6.4.1 Specimens to be equilibrated shall be processed as in
place. The graduated portion of the tube shall have a capacity
Guide D 4933.
of 10 mL. The smallest graduation should be not greater than
6.4.2 Store specimens in individual vaportight containers or
0.1 mL with the major divisions marked 1 to 10. The water trap
wrapping if any delay could occur between sampling and
should be chemically clean so that the shape of the meniscus at
weighing.
the end of the test is the same as at the beginning. (The trap
6.4.3 Weigh the specimens using a balance consistent with
may be coated with a silicone resin to give a uniform meniscus.
the desired precision (see 6.1.2).
To coat the trap, first clean it with sulfuric acid-chromic acid
6.4.4 Endpoint—Assume that the endpoint has been
mixture. Rinse the clean trap with a silicone resin and, after
reached when no appreciable change is noted in final mass
draining for a few minutes, bake for1hat approximately
readings made at approximately 4-h intervals.
200°C.)
NOTE 5—As a guide, an air-dry solid wood specimen about 50 by 100
7.1.4 Extraction Cup—Either a Wiley siphon cup of suit-
mm in cross section and 25 mm along the grain will usually attain
able size or a basket made of approximately 45 mesh, stainless
“constant mass” within 24 h when dried in a forced convection oven using
steel gauze and having the approximate dimensions of 42 mm
this procedure.
in outside diameter and 127 mm in length. The siphon cup is
6.4.5 Handling and Weighing Procedures—Dried samples
recommended for borings from heavily treated piling. When a
shall be weighed as soon as possible to minimize moisture
siphon cup is used, the loss of wood particles should be
uptake.
prevented either by placing a conical screen at the bottom of
6.5 Calculation of Moisture Content:
the siphon cup or by putting the chips or borings in a wire
6.5.1 Calculate moisture content as follows:
gauze basket which is then placed inside the siphon cup.
MC,% 5 ~A 2 B!/B 3 100 (5)
7.1.5 Hot Plate:
7.1.6 Weighing Bottle—The weighing bottle shall have a
where:
gr
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