ASTM_D_779_-_16.pdf

Designation:D77916Standard Test Method forDetermining the Water Vapor Resistance of Sheet Materialsin Contact with Liquid Water by the Dry Indicator Method1This standard is issued under the fixed designation D779;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 test method covers the determination of the timerequired for water vapor to pass through a sheet membrane incontact with liquid water using the dry-indicator method.1.2 The method has been used to evaluate water resistivebarriers,flexible flashing and other materials used in buildingconstruction in order to measure their resistance to water vaportransmission.1.3 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D585 Practice for Sampling and Accepting a Single Lot ofPaper,Paperboard,Fiberboard,and Related Product(Withdrawn 2010)3D685 Practice for Conditioning Paper and Paper Productsfor TestingE122 Practice for Calculating Sample Size to Estimate,WithSpecified Precision,the Average for a Characteristic of aLot or ProcessE631 Terminology of Building Constructions3.Terminology3.1 DefinitionsFor definitions of general terms related tobuilding construction used in this test method,refer to Termi-nology E631.4.Summary of Test Method4.1 This test method consists of bringing one side of the testspecimen in contact with water and finding the time requiredfor water vapor to pass through the specimen,as indicated bythe development of color in an indicator powder consisting ofa mixture of water-soluble dye,sugar,and starch.The sugarserves the two-fold purpose of masking the color of theparticles of dye as long as they are dry,and of absorbing thetransuded moisture and holding it in close proximity to the dye.The starch increases the stability of the mixture.4.2 Five tests are made on each side of the test specimen andreported as two separate averages.If the material being testedis intended to be exposed to water on only one side then fivetests are to be made on the side specified for water exposure.5.Significance and Use5.1 The dry indicator used in this test method is so stronglyhygroscopic it will change color in a moderate-to high-humidity atmosphere without contacting liquid water.It willalso change when in contact with liquid water.5.2 This test method is of value for materials that come incontact with water on one face and where it is important toevaluate the length of time for water vapor to pass through thematerial.6.Interferences6.1 This test method is sometimes not applicable to mate-rials containing large amounts of water-soluble components.7.Apparatus7.1 Any form of apparatus for applying the test may be usedthat fulfills the following conditions:7.1.1 One surface of the specimen is wetted uniformly at themoment the count of time is begun,7.1.2 The indicator on the opposite surface is continuouslyvisible,1This test method is under the jurisdiction of ASTM Committee E06 onPerformance of Buildings and is the direct responsibility of Subcommittee E06.55on Performance of Building Enclosures.Current edition approved Feb.1,2016.Published March 2016.Originallyapproved in 1944.Last previous edition approved in 2003 as D779-03 which waswithdrawn February 2011 and reinstated in February 2016.DOI:10.1520/D0779-16.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.1.3 No moisture reaches the indicator except that whichpasses through the specimen from the wetted surface,and7.1.4 No moisture that does so reach the indicator escapesfrom contact with it.7.1.5 A float arrangement is one apparatus that fulfills therequirements of 7.1 and is made of a thin-walled aluminum panapproximately 5 in.(127 mm)in diameter and 1 in.(25.4 mm)high,with a hole 2 in.(50.8 mm)in diameter cut in the bottom.The surface is coated with paraffin or beeswax to make it morewater repellent.The watch glass is clamped over the specimenby means of a wire-frame clamp hinged at one side andfast