Caliper or weighted caliper for evaluating boxes?, Corrugating International, October 2004 (616KB)
TAPPI caliper (T411) is a thickness measurement using a “foot” (area) of a given size applied to a surface at a pressure of 7.3psi (50kPa).1 Using a standard caliper, either motorized or manual, one attempts to accurately and reproducibly measure the thickness of a piece of corrugated board. Previous studies1 clearly demonstrate the connection between foot pressure and measured caliper for a variety of papers. It is easy to observe similar behavior for combined board; increasing the foot pressure when measuring causes the foot to “sink in” further, resulting in lower values for the measured caliper. This is especially noticeable on board which has experienced significant crush in converting operations.