Standardization of the dish method for measuring water vapor transmission

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ConferenceInternational Symposium on Humidity and Moisture, Proceedings: 1963, Washington, D.C., USA
Pages259270; # of pages: 12
Subjectvapor flow; Air and vapour barriers; ecoulement de la vapeur
AbstractDefinite knowledge of moisture movement through a material will often determine its suitability for a given application in buildings, packages or clothing. ASTM standard terminology, and vapor transmission test methods are discussed. These are dish (or cup) methods. The specimen is sealed to the mouth of an impermeable dish containing water or a desiccant, and its rate of vapor transmission is determined by weighing the assembly periodically. Several sources of error are considered, imperfect sealing being the most common. A specimen larger than the dish mouth leads to serious error when the specimen is thick and the mouth small. "Wet-cup" and "dry-cup" tests of the same specimens often yield very different results. This may be confusing, but both values are important, and a way to correlate them is shown. "Hysteresis" may affect the test results for some materials, and it is recommended that wood or paper products be stabilized in a standard atmosphere before testing. A new dish, designed for thin sheets, is described. Its use with a calibrated film promises a simple and dependable means for measuring the vapor pressure in a controlled test space.
Publication date
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedNo
NRC number8838
NPARC number20359014
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Record identifier0eaba071-e1f6-4469-9e38-9eaad0c7223f
Record created2012-07-20
Record modified2016-05-09
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