ASTM D779-03

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 in contact with liquid water. This test method, therefore, measures the combined effect of vapor and liquid transmission (9). For test times up to approximately 30 s, liquid transudation rate is dominant and this test method can be considered to measure this property. As test times exceed 30 s, the influence of vapor-transmission rate increases and this test method cannot be regarded as a valid measure of liquid resistance (sizing).

This test method is of value in cases where paper or a paper container comes into contact with water on one face.

This test method is sometimes not applicable to materials containing large amounts of water-soluble components.

1.1 This test method covers the determination of the time required for water to pass through a specimen of paper. It is based on the dry-indicator method of Carson (1-4) and modifications of it developed by Abrams (5)and Codwise (6-8).

1.2 It is designed for use with materials that require a relatively short time to test (up to approximately 30 s), and has been found useful in testing slack-sized papers.

Note 1—For testing hard-sized paper and paperboard, see TAPPI Test Method T 441.

1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.