A type of air leak tester, an instrument used to determine the smoothness of a paper surface, in which air at a specified pressure is pumped through a smooth glass column and seeps between a groove in the device's gauge head and the surface of the paper sample. An air-suspended metering float in the glass column moves up or down, the level of the float in the column indicating the rate of airflow and is thus a measure of the paper's smoothness. See also Smoothness.
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