ASTM_D_4933_-_99_2010.pdf

Designation:D493399(Reapproved 2010)Standard Guide forMoisture Conditioning of Wood and Wood-Based Materials1This standard is issued under the fixed designation D4933;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide covers standard procedures for conditioningand equilibrating wood and wood-based materials to constantmoisture content.The procedures apply to solid wood,wood-based fiber and particulate materials and panels,and woodproducts containing adhesives.They are intended for use inresearch and development activities,testing laboratories,qual-ity control,and for all other classes of producers and users.This guide includes background material on the importance ofmoisture content control,important definitions and technicaldata,possible types of apparatus,procedures,and the impor-tance of conditioning time.Users should recognize that thenecessary degree of precision and bias varies with the inten-tions of the users.Some research and testing,for example,might require very close control of moisture content,whereascontrol in an industrial storage facility might not require suchclose control.This guide offers procedures that include thesedifferent requirements.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 The following safety hazards caveat pertains only to theprocedure section,Section 6,of this guide.This standard doesnot purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of thisstandard to establish appropriate safety and health practicesand determine the applicability of regulatory limitations priorto use.2.Referenced Documents2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based Prod-uctsD4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Based MaterialsE104 Practice for Maintaining Constant Relative Humidityby Means of Aqueous Solutions2.2 ISO Standard:ISO 554 Atmospheres for Conditioning and/or TestingSpecifications33.Terminology3.1 Definitions:3.1.1 The following terms are defined in accordance withTerminology D9.3.1.2 equilibrium moisture contenta moisture content atwhich wood neither gains nor loses moisture to the surroundingair.3.1.2.1 DiscussionEquilibrium moisture content(EMC)generally connotes a moisture content at which a nominalspecies of solid wood will equilibrate.“Nominal”is used in thesense of a“hypothetical average”rather than an actual species.At constant EMC environmental conditions,however,variouswood-base materials can reach different levels of EMC.It ismore appropriate,therefore,to refer to conditioning at speci-fied relative humidity and temperature conditions than to aparticular EMC.Recommendations for conditioning are givenin ISO 554.Nominal values for equilibrium moisture content(EMC)are given in Appendix X1.Caution must be used incalculating or using these values since they represent acompromise between variation with species,and adsorptionand desorption.Also,wood containing high levels of extrac-tives or chemicals may equilibrate at different moisture con-tents.The data in Tables X1.1 and X1.2 were generated fromthe regression equation in X1.1,which is explained in moredetail in Ref(1).43.1.3 moisture contentthe amount of water contained inthe wood,usually expressed as a percentage of the mass of theoven-dry wood.3.2 Definitions of Terms Specific to This Standard:1This guide is under the jurisdiction of ASTM Committee D07 on Wood and isthe direct responsibility of Subcommittee D07.01 on Fundamental Test Methods andProperties.Current edition approved May 1,2010.Published June 2010.Originallyapproved in 1989.Last previous edition approved in 2004 as D4933 99(2004).DOI:10.1520/D4933-99R10.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.1 hysteresisthe equilibrium moisture content(EMC)that wood attains at any given relative humidity and tempera-ture depends upon the direction from which the EMC isapproached.During desorption,the EMC will be higher(sometimes by several percent moisture content)than duringadsorption.The analog of the magnetic hysteresis curve hasbeen used to describe this phenomenon.Furthermore,the EMCduring a portion of t