ASTM D4442-20

Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials

SIGNIFICANCE AND USE
4.1 Moisture content is one of the most important variables affecting the properties of wood and wood-based 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 the reference (primary) standard for determining moisture content of wood and wood-based materials, which is designed for obtaining the most precise values of moisture content consistent with the needs of the user. It 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 B provides relatively simple procedures of measuring moisture content, but generally with a lower precision than Method A. Representativeness of the specimens to the full-size product, including knots, sapwood, and heartwood, needs to be considered. These methods are not recommended for use with treated wood products impregnated with creosote, petroleum, and their solutions where the volatile non-wood chemicals contained in the specimen introduce greater bias than desired in the results.
SCOPE
1.1 These test methods cover the determination of the moisture content (MC) of wood, veneer, and other wood-based materials, including those that contain adhesives and chemical additives. The test procedures appear in the following order:    
Sections  
Method A—Primary Oven-Drying Method  
5  
Method B—Secondary Oven-Drying Method  
6  
1.2 The primary oven-drying method (Method A) is intended as the sole primary method. It is structured for purposes where the highest accuracy or degree of precision is needed (for example, research or calibration).  
1.3 The secondary oven-drying method (Method B) is intended for the purposes where the primary procedure (Method A) is not desired or justified. Test results in this method are generally less precise than in Method A.  
1.4 For materials that have been chemically treated or impregnated with creosote, petroleum, and their solutions such that the oven-drying procedures introduce greater bias than desired in the results, other methods, such as AWPA A6, are recommended.  
1.5 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 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.

General Information

• Status: Published
• Publication Date: 29-Feb-2020
• ICS: 79.040 - Wood, sawlogs and sawn timber
• ICS: 79.060.01 - Wood-based panels in general
• Technical Committee: D07 - Wood
• Drafting Committee: D07.01 - Fundamental Test Methods and Properties

Relations

• Replaces: ASTM D4442-16 - Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials
• Effective Date: 01-Mar-2020
• Refers: ASTM D9-12 - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 15-Oct-2012
• Refers: ASTM D4933-99(2010) - Standard Guide for Moisture Conditioning of Wood and Wood-Base Materials
• Effective Date: 01-May-2010
• Refers: ASTM D9-09a - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 15-Nov-2009
• Refers: ASTM D9-09ae1 - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 15-Nov-2009
• Refers: ASTM D9-09 - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 01-May-2009
• Refers: ASTM D9-05 - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 01-Dec-2005
• Refers: ASTM D4933-99 - Standard Guide for Moisture Conditioning of Wood and Wood-Base Materials
• Effective Date: 10-Oct-1999
• Refers: ASTM D4933-99(2004) - Standard Guide for Moisture Conditioning of Wood and Wood-Base Materials
• Effective Date: 10-Oct-1999
• Refers: ASTM D9-87(1999) - Standard Terminology Relating to Wood
• Effective Date: 10-Apr-1999
• Refers: ASTM D9-87(1999)e1 - Standard Terminology Relating to Wood
• Effective Date: 10-Apr-1999
• Referred By: ASTM D3501-05a(2018) - Standard Test Methods for Wood-Based Structural Panels in Compression
• Effective Date: 01-Mar-2020
• Referred By: ASTM D7338-14(2023) - Standard Guide for Assessment Of Fungal Growth in Buildings
• Effective Date: 01-Mar-2020
• Referred By: ASTM E2618-13(2019) - Standard Test Method for Measurement of Particulate Emissions and Heating Efficiency of Solid Fuel-Fired Hydronic Heating Appliances
• Effective Date: 01-Mar-2020
• Referred By: ASTM E2957-17 - Standard Test Method for Resistance to Wildfire Penetration of Eaves, Soffits and Other Projections
• Effective Date: 01-Mar-2020

Overview

ASTM D4442-20: Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials specifies precise methodologies to determine the moisture content of wood, veneer, and other wood-based materials, including those containing adhesives or chemical additives. Accurate measurement of moisture content is critical, as it affects the physical and mechanical properties of wood products in research, industrial processing, and quality control applications. This ASTM standard outlines both primary and secondary test methods and addresses circumstances requiring alternative procedures.

Key Topics

• Moisture Content Determination: The standard covers the direct measurement of moisture content using oven-drying and distillation methods, ensuring reliable and reproducible results for wood materials.
• Primary (Method A) and Secondary (Method B) Oven-Drying Methods:
  • Method A - Primary Oven-Drying: Designed for high precision and serves as the reference method, making it optimal for research and calibration purposes.
  • Method B - Secondary Oven-Drying: A simpler, less precise method suitable for general industrial application or when Method A is not feasible.
• Distillation (Method C) and Other Methods (Method D): For chemically treated or creosote-impregnated wood, distillation or alternative recognized techniques may be required.
• Precision, Bias, and Reporting: Guidance is provided on reporting procedures, specimen variability, and the inherent uncertainty and potential sources of bias, especially for materials with volatile compounds or non-wood additives.

Applications

ASTM D4442-20 is an essential standard across various industries where wood or wood-based products are utilized, ensuring material quality and optimizing production processes:

• Wood Manufacturing & Processing: Ensures correct moisture content for dimensional stability, machining, and adhesive performance.
• Construction and Structural Engineering: Used to verify that lumber, veneer, and engineered wood products meet specifications for structural integrity and safety.
• Research & Product Development: Provides highly accurate test conditions necessary for scientific research, material calibration, or comparative studies involving wood characteristics.
• Quality and Regulatory Compliance: Supports manufacturers, researchers, and regulators in meeting both domestic and international guidelines for moisture content in wood products.
• Specialty Applications: Addresses measurement concerns for chemically treated wood, such as utility poles or marine timber, recommending alternative testing for materials containing non-wood chemicals.

Related Standards

Organizations working with ASTM D4442-20 may also need to reference the following documents:

• ASTM D9: Terminology Relating to Wood and Wood-Based Products.
• ASTM D4933: Guide for Moisture Conditioning of Wood and Wood-Based Materials.
• AWPA A6: Standard Method for the Determination of Retention of Oil-Type Preservatives from Small Samples, recommended for treated woods where oven-drying introduces significant bias.

Practical Value

Using ASTM D4442-20 ensures that organizations can:

• Achieve Consistent Quality: By following standardized moisture measurement techniques, manufacturers can optimize processes, reduce rejection rates, and avoid costly product failures due to incorrect moisture levels.
• Enhance Material Performance: Correct moisture content leads to improved performance in end-use, whether in construction, furniture, or specialty wood products.
• Meet Regulatory and Export Requirements: Conformance to recognized international standards facilitates smoother market access and compliance with building codes and trade regulations.
• Minimize Risk: Accurate moisture measurement helps prevent issues such as warping, cracking, adhesive bond failures, and decay associated with excessive or uneven moisture.

Keywords: ASTM D4442-20, moisture content, wood, wood-based materials, oven-drying method, direct measurement, wood moisture testing, wood quality control, moisture content standard, wood industry standards.

Standards Content (Sample)

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: D4442 − 20
Standard Test Methods for
Direct Moisture Content Measurement of Wood and Wood-
Based 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 These test methods cover the determination of the
Barriers to Trade (TBT) Committee.
moisturecontent(MC)ofwood,veneer,andotherwood-based
materials, including those that contain adhesives and chemical
2. Referenced Documents
additives. The test procedures appear in the following order:
2.1 ASTM Standards:
Sections
MethodA—Primary Oven-Drying Method 5 D9Terminology Relating to Wood and Wood-Based Prod-
Method B—Secondary Oven-Drying Method 6
ucts
1.2 The primary oven-drying method (Method A) is in-
D4933Guide for Moisture Conditioning of Wood and
tendedasthesoleprimarymethod.Itisstructuredforpurposes Wood-Based Materials
where the highest accuracy or degree of precision is needed
2.2 Other Standard:
(for example, research or calibration).
AWPAStandardA6Standard Method for the Determination
of Retention of Oil-Type Preservatives from Small
1.3 The secondary oven-drying method (Method B) is
Samples
intended for the purposes where the primary procedure
(Method A) is not desired or justified. Test results in this
3. Terminology
method are generally less precise than in Method A.
3.1 Definitions:
1.4 For materials that have been chemically treated or
3.1.1 For definitions of terms used in this standard, refer to
impregnatedwithcreosote,petroleum,andtheirsolutionssuch
Terminology D9.
that the oven-drying procedures introduce greater bias than
3.1.2 moisture content—amount of water contained in the
desired in the results, other methods, such as AWPA A6, are
wood, usually expressed as a percentage of the mass of the
recommended.
oven-dry wood (in accordance with Terminology D9).
1.5 Units—The values stated in SI units are to be regarded
3.1.2.1 Discussion—The moisture content of wood or other
as standard. The values given in parentheses after SI units are
wood-based materials can be expressed either as a percentage
providedforinformationonlyandarenotconsideredstandard.
of oven-dry mass of the sample (oven-dry basis) or as a
1.6 This standard does not purport to address all of the
percentage of the original mass (wet basis). The methods
safety concerns, if any, associated with its use. It is the
described in this standard refer to the oven-dry basis. Because
responsibility of the user of this standard to establish appro-
oven-dry mass is used, moisture content values may exceed
priate safety, health, and environmental practices and deter-
100%. The term moisture content when used with wood or
mine the applicability of regulatory limitations prior to use.
other wood-based materials can be misleading since they
1.7 This international standard was developed in accor-
frequently contain varying amounts of volatile compounds
dance with internationally recognized principles on standard-
(extractives that are evaporated when determining moisture
ization established in the Decision on Principles for the
content). Definition of the moisture content of wood is further
complicated when determined by a thermal method because of
These test methods are under the jurisdiction of ASTM Committee D07 on
Wood and are the direct responsibility of Subcommittee D07.01 on Fundamental
Test Methods and Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2020. Published April 2020. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1984. Last previous edition approved in 2016 as D4442–16. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D4442-20. the ASTM website.
These test methods replace, in part, Test Methods D2016, for Moisture Content Available from American Wood Protection Association (AWPA), P.O. Box
of Wood, discontinued 1989. 361784, Birmingham, AL 35236-1784, http://www.awpa.com.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
D4442 − 20
thermaldegradation,whichcausesthefinalmoisture-freemass oven (5.1.1) shall be used. Each weighing bottle shall be
to decrease from small but continuous losses. furnished with a stopper to prevent moisture uptake or loss
during handling and weighing of the specimens. The stopper
4. Significance and Use
shallbeassignedandkeptwitheachbottleincaseeachstopper
has a slightly different weight.
4.1 Moisture content is one of the most important variables
5.1.4 Desiccator—A container filled with moisture absorb-
affecting the properties of wood and wood-based materials.
ingmaterial(desiccant)shallbeusedformaintainingmoisture-
The procedures in these test methods are structured to permit
free conditions of weighing bottles and for samples cooling.
the full range of use from fundamental research to industrial
processing. Method A is the reference (primary) standard for
5.2 Test Material—Any conveniently sized wood or wood-
determining moisture content of wood and wood-based
based material can be used, consistent with the use of closed
materials, which is designed for obtaining the most precise
weighing bottles (5.1.3) and the balance readability (5.1.2).
values of moisture content consistent with the needs of the
5.3 Calibration and Standardization—Determination of
user. It provides means of assessing variability contributed by
specimen variability requires a separate measurement of the
the oven or specimen hygroscopicity, or both. In addition,
contribution of variability within the oven.
criteria are described for defining the endpoint in oven-drying.
5.3.1 Determination of Oven Variability—This section per-
Method B provides relatively simple procedures of measuring
mits a separate evaluation of the oven variability from that of
moisture content, but generally with a lower precision than
specimens distributed in the oven.
MethodA.Representativenessofthespecimenstothefull-size
5.3.1.1 Calibration Specimen Selection and
product,includingknots,sapwood,andheartwood,needstobe
Preparation—AsampleofDouglas-firwoodshallbegroundto
considered. These methods are not recommended for use with
sawdust and the fraction contained in a 40/60 mesh screen
treated wood products impregnated with creosote, petroleum,
used. The sample origin or drying history is not critical. The
and their solutions where the volatile non-wood chemicals
sawdustshallbetumbledinaclosedcontaineruntilthoroughly
containedinthespecimenintroducegreaterbiasthandesiredin
mixed. All replicates shall be prepared at the same time from
the results.
thesamebatchofmaterial.Allmaterialshallbetransferredand
storedinvapor-tightweighingbottleswithstoppers(see5.1.3).
5. Method A—Primary Oven-Drying Method
5.3.1.2 Equilibration—The moisture content of the speci-
5.1 Apparatus:
mens is not important if the preparation techniques described
5.1.1 Oven—A forced-convection oven that can be main-
under 5.3.1.1 are used. Equilibration is not required, although
tained at a temperature of 103 6 2°C throughout the drying
it is preferable that the material be as uniform as possible in
chamber for the time required to dry the specimen to the
moisture content.
endpoint shall be used. Ovens shall be vented to allow the
5.3.1.3 Number and Location of Calibration Specimens—
evaporated moisture to escape (see Note 1). For calibration
Each test shall consist of a set of eight replicated specimens.
purposes, the oven shall be furnished with two shelves posi-
These shall be located at third-point positions with respect to
tioned at one third and two thirds of the cavity height.
height, width, and depth of the oven cavity. With this scheme
fourspecimenswillbepositionedoneachoftwoshelvesatone
NOTE 1—The ratio of sample mass to chamber volume and the air
velocity within the oven are not critical if temperature and relative
third and two thirds of the cavity height.
humidity within the oven are constant and uniform. To maintain uniform
5.3.2 Determination of Combined Specimen and Oven
conditions throughout the oven the number of specimens in the oven
Variability—Procedures are the same as 5.3.1.1 – 5.3.1.3
should be limited and they should be well spaced to allow good air
except that the specimens in a set shall be of similar size and
movement around all specimens. When high moisture content specimens
shape in accordance with 5.2 without grinding (see Note 3).
are being dried, more frequent air exchanges are needed.
NOTE 2—For higher precision and smaller bias, the oven should be in
Calculate variability by the equation in 5.5.2.
a controlled climate room that maintains the relative humidity as low as
NOTE3—Thespecimenvariabilitydependsonvariousfactorsincluding
possible. In a room with 70% relative humidity, the same air in an oven
the wood species, the size and the moisture condition of the specimens,
heated to 103°C will have a relative humidity of 1.7%.At a temperature
because varying amounts of volatile compounds are evaporated during
of103°Cand1.7%relativehumidity,theequilibriummoisturecontentof
oven-drying (see Discussion of 3.1.2).
solidwoodisapproximately0.13%,accordingtoGuideD4933Eq.X1.1.
5.3.3 Procedure—Use the primary oven-drying procedure
5.1.2 Balance—Based on a 10g (oven-dry) specimen, the
(5.4).
sensitivity of the balance shall be determined by the desired
precision of weighing:
5.4 Procedure:
Precision of Weighing,% Balance Sensitivity, mg
5.4.1 Specimens to be equilibrated shall be processed as in
Guide D4933.
0.01 1
5.4.2 Store specimens in individual vapor-tight containers
0.05 5
0.1 10
(for example, plastic bags) if any delay could occur between
0.5 50
sampling and weighing.
1.0 100
5.4.3 Weigh each specimen in a closed weighing bottle (see
For other oven-dry mass levels, the sensitivity requirement
5.1.3)usingabalanceconsistentwiththedesiredprecision(see
shall be scaled appropriately.
5.1.2) at room temperature.
5.1.3 Weighing Bottles—Weighing bottles made of a vapor-
tight material that can withstand the drying temperature in the NOTE 4—Be aware that static electricity affects the mass readings.
D4442 − 20
5.4.4 Preheat the oven to a temperature of 103 6 2°C. precision of measurement due to the inability to determine the
5.4.5 Place specimens in the open weighing bottles in the bias of measurement.With this approach, it is possible that the
oven within the volume tested for oven variability (see 5.3.2). reportedvalueofmoisturecontentdeviatesfromthetruevalue
5.4.6 Afterdrying,closetheweighingbottlescontainingthe with greater uncertainty than the determined precision.
5.7.2 Precision—The precision of measurement depends on
dried specimens before taking out of the hot oven and store
them in a desiccator with fresh desiccant until they have many factors including variance in the oven and in the
specimen material, room ambient conditions (see 5.1.1 and
reachedroomtemperature.Weighthespecimensinaccordance
with 5.4.3 (see Note 4). Note 1), sensitivity of the balance (see 5.1.2), the size of the
specimen, etc.
5.4.7 Endpoint—A
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4442 − 16 D4442 − 20
Standard Test Methods for
Direct Moisture Content Measurement of Wood and Wood-
Based 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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 These test methods cover the determination of the moisture content (MC) of wood, veneer, and other wood-based 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: procedures appear in the following order:
Method A—Primary Oven-Drying Method
Method B—Secondary Oven-Drying Method
Method C—Distillation (Secondary) Method
Method D—Other Secondary Methods.
Sections
Method A—Primary Oven-Drying Method 5
Method B—Secondary Oven-Drying Method 6
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. needed (for example, research or calibration).
1.3 The secondary methods (B through D) areoven-drying method (Method B) is intended for special purposes or under
circumstances the purposes where the primary procedure (Method A) is not desired or justified. In these procedures, moisture
content values cannot be reported with an accuracy greater than integer percentage values (that is, lower than in Method A).Test
results in this method are generally less precise than in Method A.
1.4 Distillation (secondary) method is intended for use with For materials that have been chemically treated or impregnated with
creosote, petroleum, and their solutions such that the oven-drying procedures introduce greater errorbias than desired in the
results.results, other methods, such as AWPA A6, are recommended.
1.5 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this The
values given in parentheses after SI units are provided for information only and are not considered standard.
1.6 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.7 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.
2. Referenced Documents
2.1 ASTM Standards:
D9 Terminology Relating to Wood and Wood-Based Products
D4933 Guide for Moisture Conditioning of Wood and Wood-Based Materials
These test methods are under the jurisdiction of ASTM Committee D07 on Wood and are the direct responsibility of Subcommittee D07.01 on Fundamental Test Methods
and Properties.
Current edition approved Nov. 15, 2016March 1, 2020. Published November 2016April 2020. Originally approved in 1984. Last previous edition approved in 20152016
as D4442 – 15.D4442 – 16. DOI: 10.1520/D4442-16.10.1520/D4442-20.
These test methods replace, in part, Test Methods D2016, for Moisture Content of Wood, discontinued 1989.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4442 − 20
2.2 Other Standard:
AWPA Standard A6 Standard Method for the Determination of Retention of Oil-Type Preservatives from Small Samples
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, standard, refer to Terminology D9.
3.1.2 moisture content—the amount of water contained in the wood, usually expressed as a percentage of the mass of the
oven-dry wood (in accordance with Terminology D9).
3.1.2.1 Discussion—
The moisture content of wood or other wood-based materials can be expressed either as a percentage of oven-dry mass of the
sample (oven-dry basis) or as a percentage of the original mass (wet basis). The methods described in this standard refer to the
oven-dry basis. Because oven-dry mass is used, moisture content values may exceed 100 %. The term moisture content when used
with wood or other wood-based materials can be misleading since they frequently contain varying amounts of volatile compounds
(extractives that are evaporated when determining moisture content). Definition of the moisture content of wood is further
complicated when determined by a thermal method because of thermal degradation, which causes the final moisture-free mass to
decrease from small but continuous losses.
4. Significance and Use
4.1 Moisture content is one of the most important variables affecting the properties of wood and wood-based 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 the reference (primary) standard for determining moisture content of wood and wood-based materials, which 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-based materials. Methods B through D are secondary methods to permit B provides relatively simple procedures of
measuring moisture content, but generally with less a lower precision than Method A. Representativeness of the specimens to the
full-size product, including knots, sapwood, and heartwood, needs to be considered. These methods are not recommended for use
with treated wood products impregnated with creosote, petroleum, and their solutions where the volatile non-wood chemicals
contained in the specimen introduce greater bias than desired in the results.
5. Method A—Oven-Drying (Primary) A—Primary Oven-Drying Method
5.1 Apparatus:
5.1.1 Oven—A forced-convection oven that can be maintained at a temperature of 103 6 2°C throughout the drying chamber
for the time required to dry the specimen to the endpoint shall be used. Ovens shall be vented to allow the evaporated moisture
to escape.escape (see Note 1). For calibration purposes, the oven shall be furnished with two shelves positioned at one third and
two thirds of the cavity height.
NOTE 1—The ratio of sample mass to chamber volume and the air velocity within the oven are not critical as long as if temperature and relative
humidity within the oven are constant. Room relative humidity should be less than 70 % relative humidity, at which condition the oven is at 1.7 % relative
humidity. For best precision, drying should be carried out in a constant relative humidity room with the relative humidity as low as possible.constant and
uniform. To maintain uniform conditions throughout the oven the number of specimens in the oven should be limited and they should be well spaced
to allow good air movement around all specimens. When high moisture content specimens are being dried, more frequent air exchanges are needed.
NOTE 2—For higher precision and smaller bias, the oven should be in a controlled climate room that maintains the relative humidity as low as possible.
In a room with 70 % relative humidity, the same air in an oven heated to 103°C will have a relative humidity of 1.7 %. At a temperature of 103°C and
1.7 % relative humidity, the equilibrium moisture content of solid wood is approximately 0.13 %, according to Guide D4933 Eq. X1.1.
5.1.2 Balance—Based on a 10 g (oven-dry) specimen, minimum readabilitythe sensitivity of the balance shall be determined by
the desired reporting level precision of precision:weighing:
Reporting Precision Level, MC, % Minimum Balance Readability, mg
Precision of Weighing, % Balance Sensitivity, mg
0.01 1
0.05 5
0.1 10
0.5 50
1.0 100
For other oven-dry mass levels, the sensitivity requirement shall be scaled appropriately.
Available from American Wood Protection Association (AWPA), P.O. Box 361784, Birmingham, AL 35236-1784, http://www.awpa.com.
D4442 − 20
5.1.3 Weighing Bottles—Weighing bottles made of a vapor-tight material that can withstand the drying temperature in the oven
(5.1.1) shall be used. Each weighing bottle shall be furnished with a stopper to prevent moisture uptake or loss during handling
and weighing of the specimens. The stopper shall be assigned and kept with each bottle in case each stopper has a slightly different
weight.
5.1.4 Desiccator—A container filled with moisture absorbing material (desiccant) shall be used for maintaining moisture-free
conditions of weighing bottles and for samples cooling.
5.2 Test Material—Any conveniently sized wood or wood-based material can be used, consistent with the use of closed
weighing jarsbottles (5.4.75.1.3) and the balance readability (5.1.2).
NOTE 2—If specimens contain any degree of volatilizable material other than water, it may be necessary to either use Method C or run Method A and
C concurrently.
5.3 Calibration and Standardization—Determination of specimen variability requires a separate measurement of the
contribution of variability within the oven.
5.3.1 Determination of Oven Variability—This section permits a separate evaluation of the oven variability from that of
specimens distributed in the oven.
5.3.1.1 Calibration Specimen Selection and Preparation—Douglas-fir A sample of Douglas-fir wood shall be ground to sawdust
and thatthe fraction contained in a 40/60 mesh screen used. The sample origin or drying history is not critical. The sawdust shall
be tumbled in a closed container until thoroughly mixed. All replicates shall be prepared at the same time from the same batch
of material. All material shall be transferred and stored in air-tight weighing jars.vapor-tight weighing bottles with stoppers (see
5.1.3).
5.3.1.2 Equilibration—The moisture content of the specimenspecimens is not important if the preparation techniques described
under 5.3.1.1 are used. Equilibration is not required, although it is preferable that the material be as uniform as possible in moisture
content.
5.3.1.3 Number and Location of Calibration Specimens—Each test shall consist of a set of eight replicated specimens. These
shall be located at third-point positions with respect to height, width, and depth of the oven cavity. With this scheme four
samplesspecimens will be positioned on each of two shelves at one third and two thirds of the cavity height.
5.3.2 Determination of Combined Specimen and Oven 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.the specimens in a set shall be of similar size and shape in accordance with
5.2 without grinding (see Note 3). Calculate variability by the equation in 5.5.2.
NOTE 3—The specimen variability depends on various factors including the wood species, the size and the moisture condition of the specimens, because
varying amounts of volatile compounds are evaporated during oven-drying (see Discussion of 3.1.2).
5.3.3 Procedure—Use the primary oven-drying procedure (5.4).
5.4 Procedure:
5.4.1 Specimens to be equilibrated shall be processed as in Guide D4933.
5.4.2 Store specimens in individual vapor-tight containers (for example, plastic bags) if any delay could occur between sampling
and weighing.
5.4.3 Weigh the specimens each specimen in a closed weighing bottle (see 5.1.3) using a balance consistent with the desired
precision (see 5.1.2).) at room temperature.
NOTE 4—Be aware that static electricity affects the mass readings.
5.4.4 Preheat the oven to a temperature of 103 6 2°C2°C.
5.4.5 Place specimens in the open weighing bottles in the oven within the volume tested for oven precision.variability (see
5.3.2).
5.4.6 After drying, close the weighing bottles containing the dried specimens before taking out of the hot oven and store them
in a desiccator with fresh desiccant until they have reached room temperature. Weigh the specimens in accordance with 5.4.3 (see
Note 4).
5.4.7 Endpoint—Assume that the endpoint has been reached when the mass loss in a 3 h3-h interval is equal to or less than twice
the selected balance sensitivity. For example, given a specimen weight of 10 g and for a balance sensitivity of 1 mg chosen in 5.1.2
to allow reporting to a 0.01 % MC precision, the endpoint is assumed to have been reached when the change in weight is 2 mg
or less in a 3 h period.
NOTE 5—For example, given a specimen weight of 10-g and for a balance sensitivity of 1 mg chosen in 5.1.2 to allow reporting to a 0.01 % MC
precision, the endpoint is assumed to have been reached when the change in weight is 2 mg or less in a 3-h period.
5.4.7 Handling and Weighing Procedures—Dried samples shall be stored in a desiccator with fresh desiccant until they have
reached room temperature. All weighings shall be carried out using closed weighing jars.
5.5 Calculations:
5.5.1 Calculate moisture content as follows:
MC,%5 A 2 B /B 3100 (1)
~ !
D4442 − 20
where:
A = original mass, g, and
B = oven-dry mass, g.
Example—A specimen of wood weighs 56.70 g. After oven-drying, the mass is 52.30 g.
MC, %5 ~56.70 2 52.30!/52.30 3100 (2)
5 4.40/52.30 3100 5 8.4 %
~ !
MC 5 56.70 2 52.30 /52.30 3100 5 8.4 % (2)
~ !
NOTE 3—If wood has been treated with a nonvolatile chemical, or if a wood-based material contains a large amount of non-wood chemicals that cannot
be neglected, and if the mass of the retained chemical(s) is known, the moisture content may be determined as follows:
MC,%5 ~A 2 B!/D 3100 (3)
where:
D = B minus mass of retained chemical in sample.
NOTE 6—If wood has been treated with a nonvolatile chemical, or if a wood-based material contains a large amount of non-wood chemicals that cannot
be neglected, and if the mass of the retained chemical(s) is known, the moisture content may be determined as follows:
MC,%5 ~A 2 B!/D 3100 (3)
where:
D = B minus mass of retained chemical in sample.
D4442 − 20
5.5.2 Calculate variance of the specimens as follows:
2 2 2
S 5 S 2 S (4)
w ow o
where:
S = specimen material variance,
w
S = oven variance (from 5.3.1), and
o
S = oven variance (from 5.3.1), and
o
S = combined specimen and oven variance (5.3.2).
ow
5.6 Report:
5.6.1 Report the following information:
5.6.1.1 Test method used and any deviation from the standard procedures,
5.6.1.2 Balance model and sensitivity,
5.6.1.3 Oven model, type, and variance,
5.6.1.4 Type of material,
5.6.1.5 Description of specimens and their nominal oven-dry mass,
5.6.1.6 Oven variance,Number of specimens,
5.6.1.4 Specimen variance,
5.6.1.5 Balance sensitivity,
5.6.1.7 Oven model and type, Moisture content values including mean value, and
5.6.1.8 Any deviation from the prescribed method.Specimen material variance or standard deviation.
5.6.2 The number of decimal places in moisture content values reported shall not exceed the precision level ((see 5.1.25.7.2).
5.7 Precision and Bias:
5.7.1 PrecisionUncertainty of Measurement—By definition, the accuracyuncertainty of measurement has been set equal to the
determined precision of test measurement, that is, there is no assumed bias of measurement due to the inability to accurately assess
moisture content. determine the bias of measurement. With this approach, it is possible that the actual accuracy will be poorer than
the stated accuracy. At this time, no data are available from which to report typical variances in ovens or from specimen
material.reported value of moisture content deviates from the true value with greater uncertainty than the determined precision.
5.7.2 Precision—The precision of measurement depends on many factors including variance in the oven and in the specimen
material, room ambient conditions (see 5.1.1 and Note 1), sensitivity of the balance (see 5.1.2), the size of the specimen, etc.
5.7.3 Bias—The bias of this test method is unknown because the values are determined solely in terms of this test method itself.
However, the values of moisture content determined in accordance with this test method generally contain some degree of bias by
definition, due to varying amounts of volatile compounds or of non-wood chemicals contained in the material (see Discussion of
3.1.2 and Appendix X1).
6. Method B—Oven-Drying (Secondary) B—Secondary Oven-Drying Method
6.1 Apparatus:
6.1.1 Oven—An oven that can maintain 103 6 2°C near the drying endpoint shall be used.
6.1.2 Balance—The sensitivity shall be a minimum of sufficient to measure within 0.1 % of the nominal oven-dry mass of the
specimen (see 5.1.2).
6.2 Test Material—Any conveniently sized wood or wood-based material can be used,used; however, the balance readability
shall be consistent with the desired precision (see 5.1.2 and 5.3).
NOTE 4—If specimens contain any degree of volatilizable material other than water, it may be necessary to either use Method C, or run Methods B
and C concurrently.
6.3 Calibration and Standardization—No specific tests are required unless greater precision
...