The comparative response of ring crush test and stfi short span crush test to paper mill process variable changes, Corrugating International, October 2000, Vol. 2(4)

Currently, about half of United States paperboard manufacturers use the Ring Crush Test method and about half use the STFI Short Span Compressive Test method to quantify the edge compression strength of linerboard and corrugating medium. The analysis in this report supports the conclusion that the Ring Crush Test (RCT)and the STFI Short Span Compressive Test (STFI)are not interchangeable test methods. They are measuring different compressive strength properties of the paperboard as affected by paper mill process changes. The difference between the two test methods is as much as 8.7% to 11.0%. Differences of this order can have a significant impact on a mill’s cost structure by causing unnecessary process changes, by supporting otherwise non-justifiable capital expenditures, or by adversely affecting the end use performance of the material.