Description

Scope

1.1 This method is used to measure the air resistance of approximately 6.45 sq. cm. (l sq. in.) circular area ofpaper using a pressure differential of 1.22 kPa. The recommended range of the liquid column instrument is from 5 to1800 seconds per 100 mL cylinder displacement. For more impermeable papers the time requirements become soexcessive that other techniques are preferable.

1.2 This method measures the volume of air that passes through the test specimen, along with any possibleleakage of air across the surface; therefore it is unsuitable for paper or paperboards which cannot be securely clamped soas to avoid significant surface and/or edge leakage.

1.3 For a similar method of measuring air resistance that tests paper at a higher pressure (approx. 3 kPa), andhas higher resolution in measuring smaller air volumes, refer to TAPPI T 536. For a method of measuring air permeanceat pressures up to 9.85 kPa, using both smaller and larger test areas, refer to TAPPI T 547.