ASTM D4442-92(2003)
(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
SIGNIFICANCE AND USE
Moisture content is one of the most important variables affecting the properties of wood and wood-base materials. The procedures in these test methods are structured to permit the 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 contributed by the oven or specimen hygroscopicity, or both. In addition, criteria are described for defining the endpoint in oven-drying. Method A is the reference (primary) standard for determining moisture content of wood and wood-base materials. Methods B through D are secondary methods to permit relatively simple procedures of measuring moisture content, but with less precision than Method A. However, greater precision may be obtained with supporting data by using the appropriate procedures in Method A.
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: Method A-Primary Oven-Drying MethodMethod B-Secondary Oven-Drying MethodMethod C-Distillation (Secondary) MethodMethod D-Other Secondary Methods.
1.2 The primary oven-drying method (Method A) is intended as the sole primary method. It is structured for research purposes where the highest accuracy or degree of precision is needed.
1.3 The secondary methods (B through D) are intended for special purposes or under circumstances where the primary procedure is not desired or justified. In these procedures, moisture content values cannot be reported with an accuracy greater than integer percentage values. However, a greater level of accuracy may be reported if the appropriate primary procedures are used.
1.4 Distillation (secondary) method is intended for use with materials that have been chemically treated or impregnated such that the oven-drying procedures introduce greater error than desired in the results.
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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Designation:D4442–92(Reapproved 2003)
Standard Test Methods for
Direct Moisture Content Measurement of Wood and Wood-
Base Materials
This standard is issued under the fixed designation D4442; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber 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 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 D9 Terminology Relating to Wood
wood-base materials, including those that contain adhesives D4933 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:
MethodA—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 TerminologyD9).
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.
4. Significance and Use
1.5 This standard does not purport to address all of the
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
contributedbytheovenorspecimenhygroscopicity,orboth.In
These test methods are under the jurisdiction of ASTM Committee D07 on
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.
oven-drying. MethodAis the reference (primary) standard for
Current edition approved Feb. 15, 1992. Published April 1992. Originally
published as D4442–84. Last previous edition D4442–84.
These test methods replace, in part, Test Methods D2016, for Moisture Content
of Wood, discontinued 1989. Annual Book of ASTM Standards, Vol 04.10.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959, United States.
D4442–92 (2003)
determining moisture content of wood and wood-base materi- located at third-point positions with respect to height, width,
als. Methods B through D are secondary methods to permit and depth of the oven cavity. With this scheme four samples
relatively simple procedures of measuring moisture content, will be positioned on each of two shelves at one third and two
but with less precision than Method A. However, greater thirds of the cavity height.
precision may be obtained with supporting data by using the
5.3.2 Determination of Combined Specimen and Oven
appropriate procedures in Method A.
Variability—Procedures are the same as 5.3.1.1-5.3.1.3 except
that specimens of any origin and size or shape can be used.
5. Method A—Oven-Drying (Primary)
Calculate variability by the equation in 5.5.2.
5.1 Apparatus: 5.3.3 Procedure—Use the primary oven-drying procedure
5.1.1 Oven—A forced-convection oven that can be main- (5.4).
tained at a temperature of 103 6 2°C throughout the drying
5.4 Procedure:
chamber for the time required to dry the specimen to the
5.4.1 Specimens to be equilibrated shall be processed as in
endpoint shall be used. Ovens shall be vented to allow the
Guide D4933.
evaporated moisture to escape.
5.4.2 Storespecimensinindividualvapor-tightcontainersif
NOTE 1—The ratio of sample mass to chamber volume and the air
any delay could occur between sampling and weighing.
velocitywithintheovenarenotcriticalaslongastemperatureandrelative
5.4.3 Weigh the specimens using a balance consistent with
humidity within the oven are constant. Room relative humidity should be
the desired precision (see 5.1.2).
less than 70% relative humidity, at which condition the oven is at 1.7%
5.4.4 Place specimens in the oven within the volume tested
relative humidity. For best precision, drying should be carried out in a
constant relative humidity room with the relative humidity as low as for oven precision.
possible.
5.4.5 Endpoint—Assume that the endpoint has been
reached when the mass loss in a 3-h interval is equal to or less
5.1.2 Balance—Based on a 10-g (oven-dry) specimen,
thantwicetheselectedbalancesensitivity.Forexample,witha
minimum readability of the balance shall be determined by the
10-g (oven-dry) specimen, the balance sensitivity for 0.01%
desired reporting level of precision:
MC precision is 0.1 mg (see 5.1.2), therefore, dry to 0.2 mg or
Reporting Precision Level, MC,% Minimum Balance Readability, mg
less mass loss in a 3-h period.
0.01 1
5.4.6 Handling and Weighing Procedures—Dried samples
0.05 5
0.1 10 shall be stored in a desiccator with fresh desiccant until they
0.5 50
have reached room temperature.All weighings shall be carried
1.0 100
out using closed weighing jars.
For other oven-dry mass levels, the sensitivity requirement
5.5 Calculations:
shall be scaled appropriately.
5.5.1 Calculate moisture content as follows:
5.2 Test Material—Any conveniently sized wood or wood-
MC,% 5 ~A 2 B!/B 3100 (1)
based material can be used, consistent with the use of closed
weighing jars (5.4.6) and the balance readability (5.1.2).
where:
A = original mass, g, and
NOTE 2—If specimens contain any degree of volatilizable material
other than water, it may be necessary to either use Method C or run B = oven-dry mass, g.
Method A and C concurrently.
Example—A specimen of wood weighs 56.70 g. After oven-
drying, the mass is 52.30 g.
5.3 Calibration and Standardization—Determination of
specimen variability requires a separate measurement of the MC,% 5 ~56.70 252.30!/52.30 3100 (2)
contribution of variability within the oven.
5 ~4.40/52.30! 3100 58.4%
5.3.1 Determination of Oven Variability—This section per-
NOTE 3—If wood has been treated with a nonvolatile chemical and if
mits a separate evaluation of the oven variability from that of
the mass of the retained chemical is known, the moisture content may be
specimens distributed in the oven.
determined as follows:
5.3.1.1 Specimen Selection and Preparation—Douglas-fir
shall be ground to sawdust and that fraction contained in a MC,% 5 ~A 2 B!/D 3100 (3)
40/60meshscreenused.Thesampleoriginordryinghistoryis
notcritical.Thesawdustshallbetumbledinaclosedcontainer
until thoroughly mixed. All replicates shall be prepared at the
where:
same time from the same batch of material. All material shall
D = B minus mass of retained chemical in sample.
be transferred and stored in air-tight weighing jars.
5.5.2 Calculate variance of the specimens as follows:
5.3.1.2 Equilibration—The moisture content of the speci-
2 2 ½
men is not important if the preparation techniques described
S 5 ~S 2 S ! (4)
w ow o
under 5.3.1.1 are used. Equilibration is not required, although
where:
it is preferable that the material be as uniform as possible in
S = specimen material variance,
w
moisture content.
S = oven variance (from 5.3.1), and
o
5.3.1.3 Number and Location of Specimens—Eachtestshall
S = combined specimen and oven variance (5.3.2).
ow
consist of a set of eight replicated specimens. These shall be
D4442–92 (2003)
5.6 Report—Report the following information: nominal
B = oven-dry mass, g.
oven-dry mass, type of material, oven variance, specimen
Example—Aspecimen of wood weighed 56.7 g.After
variance, balance sensitivity, oven model and type, and any
oven-drying, the mass was 52.3 g.
deviation from the prescribed method. The number of decimal
MC,% 5 ~56.7 252.3!/52.3 3100 (6)
places reported shall not exceed the precision level (5.1.2).
5 ~4.4/52.3! 3100 58.4
5.7 Precision and Bias:
Roundto8% ~see 1.3 and 6.7.1!
5.7.1 Precision of Measurement—By definition, the accu-
racy of measurement has been set equal to the determined
NOTE 6—If wood has been treated with a nonvolatile chemical and if
precisionoftestmeasurement,thatis,thereisnoassumedbias
the mass of the retained chemical is known, the moisture content may be
of measurement due to the inability to accurately assess determined as follows:
moisture content. With this approach the actual accuracy may
MC,% 5 ~A 2 B!/D 3100 (7)
be poorer than the stated accuracy. At this time, no data are
where:
available from which to report typical variances in ovens or
D = B minus the mass of retained chemical in sample.
from specimen material.
6.6 Report—Report the following information: Mean, stan-
dard deviation, number of specimens, and any deviation from
6. Method B—Oven-Drying (Secondary)
the method. Moisture content values shall be integer only (see
6.1 Apparatus:
6.7.1).
6.1.1 Oven—Anoventhatcanmaintain103 62°Cnearthe
6.7 Precision and Bias:
drying endpoint shall be used.
6.7.1 The precision is assumed to be no greater than61%
6.1.2 Balance—The sensitivity shall be a minimum of
moisture content for any measurement unless the appropriate
0.1% of the nominal oven-dry mass of the specimen (see
procedures in Section 5 are used.
5.1.2).
6.7.2 No bias calculations may be made from this proce-
6.2 Test Material—Any conveniently sized wood or wood-
dure.
based material can be used, however, the balance readability
7. Method C—Distillation
shall be consistent with the desired precision (see 5.1.2 and
5.3).
7.1 Apparatus:
7.1.1 Extraction Flask—A 500-mL flask and thimble
NOTE 4—If specimens contain any degree of volatilizable material
holder, as shown in Fig. 1. The flask and holder may be
other than water, it may be necessary to either use Method C, or run
combined in one unit.
Methods B and C concurrently.
7.1.2 Condenser—A water-cooler condenser of the cold-
6.3 Calibration and Standardization—No specific tests are
finger type, as shown in Fig. 1, or of the straight-tube, Liebig
required unless greater precision than integer moisture content
type.
values are desired. See 6.7.
7.1.3 Water Trap—Aglass tube preferably having an inside
6.4 Procedure:
diameter of 9 to 10 mm and sealed at one end. If a trap with
6.4.1 Specimens to be equilibrated shall be processed as in
stopcock is used, the stopcock shall be securely fastened in
Guide D4933.
place. The graduated portion of the tube shall have a capacity
6.4.2 Store specimens in individual vaportight containers or
of 10 mL. The smallest graduation should be not greater than
wrapping if any delay could occur between sampling and
0.1mLwiththemajordivisionsmarked1to10.Thewatertrap
weighing.
shouldbechemicallycleansothattheshapeofthemeniscusat
6.4.3 Weigh the specimens using a balance consistent with
the end of the test is the same as at the beginning. (The trap
the desired precision (see 6.1.2).
maybecoatedwithasiliconeresintogiveauniformmeniscus.
6.4.4 Endpoint—Assume that the endpoint has been
To coat the trap, first clean it with sulfuric acid-chromic acid
reached when no appreciable change is noted in final mass
mixture. Rinse the clean trap with a silicone resin and, after
readings made at approximately 4-h intervals.
draining for a few minutes, bake for 1 h at approximately
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
ablesizeorabasketmadeofapproximately45mesh,stainless
“constantmass”within24hwhendriedinaforcedconvectionovenusing
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 3100 (5)
7.1.5 Hot Plate:
7.1.6 Weighing Bottle—The weighing bottle shall have a
where:
ground glass stopper and be of sufficient size to contain the
A = original mass, g, and
wire extraction cup or Wiley siphon described in 7.1.4.
D4442–92 (2003)
7.2.1 Desiccant—Calcium chloride, silica gel, etc.
7.2.2 Toluene—The toluene shall be of the grade known as
industrial pure, boiling within 2°C.
7.3 Preparation of Appa
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