ASTM D779-16(2022)
(Test Method)Standard Test Method for Determining the Water Vapor Resistance of Sheet Materials in Contact with Liquid Water by the Dry Indicator Method
Standard Test Method for Determining the Water Vapor Resistance of Sheet Materials in Contact with Liquid Water by the Dry Indicator Method
SIGNIFICANCE AND USE
5.1 The dry indicator used in this test method is so strongly hygroscopic it will change color in a moderate- to high-humidity atmosphere without contacting liquid water. It will also change when in contact with liquid water.
5.2 This test method is of value for materials that come in contact with water on one face and where it is important to evaluate the length of time for water vapor to pass through the material.
SCOPE
1.1 This test method covers the determination of the time required for water vapor to pass through a sheet membrane in contact with liquid water using the dry-indicator method.
1.2 The method has been used to evaluate water resistive barriers, flexible flashing and other materials used in building construction in order to measure their resistance to water vapor transmission.
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.4 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.
1.5 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
Relations
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: D779 − 16 (Reapproved 2022)
Standard Test Method for
Determining the Water Vapor Resistance of Sheet Materials
in Contact with Liquid Water by the Dry Indicator Method
This standard is issued under the fixed designation D779; 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 D685 Practice for Conditioning Paper and Paper Products
for Testing
1.1 This test method covers the determination of the time
E122 Practice for Calculating Sample Size to Estimate,With
required for water vapor to pass through a sheet membrane in
Specified Precision, the Average for a Characteristic of a
contact with liquid water using the dry-indicator method.
Lot or Process
1.2 The method has been used to evaluate water resistive
E631 Terminology of Building Constructions
barriers, flexible flashing and other materials used in building
construction in order to measure their resistance to water vapor
3. Terminology
transmission.
3.1 Definitions—For definitions of general terms related to
1.3 The values stated in inch-pound units are to be regarded
building construction used in this test method, refer to Termi-
as standard. The values given in parentheses are mathematical
nology E631.
conversions to SI units that are provided for information only
and are not considered standard.
4. Summary of Test Method
1.4 This standard does not purport to address all of the
4.1 This test method consists of bringing one side of the test
safety concerns, if any, associated with its use. It is the
specimen in contact with water and finding the time required
responsibility of the user of this standard to establish appro-
for water vapor to pass through the specimen, as indicated by
priate safety, health, and environmental practices and deter-
the development of color in an indicator powder consisting of
mine the applicability of regulatory limitations prior to use.
a mixture of water-soluble dye, sugar, and starch. The sugar
1.5 This international standard was developed in accor-
serves the two-fold purpose of masking the color of the
dance with internationally recognized principles on standard-
particles of dye as long as they are dry, and of absorbing the
ization established in the Decision on Principles for the
transudedmoistureandholdingitincloseproximitytothedye.
Development of International Standards, Guides and Recom-
The starch increases the stability of the mixture.
mendations issued by the World Trade Organization Technical
4.2 Fivetestsaremadeoneachsideofthetestspecimenand
Barriers to Trade (TBT) Committee.
reported as two separate averages. If the material being tested
is intended to be exposed to water on only one side then five
2. Referenced Documents
tests are to be made on the side specified for water exposure.
2.1 ASTM Standards:
D585 Practice for Sampling and Accepting a Single Lot of
5. Significance and Use
Paper, Paperboard, Fiberboard, and Related Product
3 5.1 The dry indicator used in this test method is so strongly
(Withdrawn 2010)
hygroscopic it will change color in a moderate- to high-
humidity atmosphere without contacting liquid water. It will
This test method is under the jurisdiction of ASTM Committee E06 on
also change when in contact with liquid water.
Performance of Buildings and is the direct responsibility of Subcommittee E06.55
5.2 This test method is of value for materials that come in
on Performance of Building Enclosures.
Current edition approved Oct. 1, 2022. Published October 2022. Originally
contact with water on one face and where it is important to
approved in 1944. Last previous edition approved in 2016 as D779-16. DOI:
evaluate the length of time for water vapor to pass through the
10.1520/D0779-16R22.
material.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on 6. Interferences
the ASTM website.
6.1 This test method is sometimes not applicable to mate-
The last approved version of this historical standard is referenced on
www.astm.org. rials containing large amounts of water-soluble components.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D779 − 16 (2022)
7. Apparatus 8.2 Indicator—The water-transudation indicator is com-
posed of pure, powdered cane sugar (do not use confectioner’s
7.1 Any form of apparatus for applying the test may be used
sugar, which contains starch), pure soluble starch, and methyl
that fulfills the following conditions:
violet dye (Color Index 680). Pass each ingredient separately
7.1.1 Onesurfaceofthespecimeniswetteduniformlyatthe
through a No. 100 screen (39.4 mesh/mm), and completely dry
moment the count of time is begun,
it in a desiccator over a desiccant (see 8.1) before making the
7.1.2 The indicator on the opposite surface is continuously
mixture. When dry, weigh and mix the following proportions
visible,
by weight:
7.1.3 No moisture reaches the indicator except that which
Sugar 45
passes through the specimen from the wetted surface, and
Soluble starch 5
7.1.4 No moisture that does so reach the indicator escapes
Dye 1
from contact with it.
8.2.1 Mix the ingredients by screening repeatedly through a
7.1.5 A float arrangement is one apparatus that fulfills the
No. 60 screen (23.6 mesh/mm) until the mixture is uniform.
requirementsof7.1andismadeofathin-walledaluminumpan
Keep the indicator in a desiccator when it is not being used.
approximately 5 in. (127 mm) in diameter and 1 in. (25.4 mm)
8.3 Water—Distilled or demineralized
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 more
9. Sampling, Test Specimens, and Test Units
water repellent. The watch glass is clamped over the specimen
by means of a wire-frame clamp hinged at one side and
9.1 For acceptance purposes, sample the lot of material in
fastened under a spring at the opposite side. accordance with Practice D585.
7.1.6 Instead of using the float arrangement described in
9.2 When sampling for other purposes, Practice E122 may
7.1.5, it is also permissible to form a boat, by folding up the
be used for an alternative.
edges of the specimen or by dipping the four edges of the
9.3 From each test unit obtained in accordance with 9.1 or
specimen in hot wax, and floating it on the surface of the water.
9.2, cut ten test specimens, free from folds, wrinkles, or other
If the specimen does not easily float on its own it can be
blemishesnotcommonlyinherentinthematerial.Aconvenient
supported by a hollow cylinder having the upper end barely
size is approximately 2.5 in. by 2.5 in. (63 mm by 63 mm).
submerged under the surface of the water in a suitable vessel.
The dry indicator powder is applied to the top surface in 9.4 Use a suitable code designation such as Side I and Side
accordance with Section 12 (with watch glass) or Section 13
II, or when there is an obvious difference between the sides,
(without watch glass) just before floating the specimen on the such as Side I, coated, and Side II, uncoated. The side
water.
designated is that which is to be in contact with the water.
7.2 Shaker and Desiccator Assembly (Fig. 1) for the
10. Preparation of Apparatus
Indicator—Theshakerispreparedfroma10 mLscrew-topvial
10.1 The water on which the specimens are floated should
by cutting away most of the metal of the flat p
...
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