Refers to the openness or compactness of the fibers in a paper and is measured by the ability of air to pass through the sheet. The more open a paper is, the greater its porosity.
The degree of compactness of the fibers of the paper. For the explanation of the test to determine the porosity of the surface of paper or board, see Chapter 6.
A measurement of the ability of paper to allow fluids to pass through paper and paperboard, which is an important factor in ink penetration.