The ring crush resistance of paper and paperboard is the maximum compressive force that a test piece will sustain without being crushed, the test piece being in the form of a cylinder, standing on one end, and the force being applied to the other end under specified conditions. This method applies to papers and paperboards with a thickness of not less than 0.15 mm and not more than 0.49 mm.
It is primarily intended for corrugated media, liner and other papers and boards for use in the manufacture of packaging cases and boxes.
The test piece is placed in a holder containing as annular groove so that it forms a cylinder with a horizontal base.
It is then subjected to a uniformly increasing force in a testing machine until crushing occurs.