Sources of Variability in Testing Absorptive Rate of Tissue Paper, 2009 TAPPI Engineering, Pulping, Environmental Conference

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It is desirable to measure the rate of liquid absorption of tissue and towel paper products, but test methods currently available do not have an ability to discern repeatable or useful differences between samples. Several recent round-robin testing evaluations by TAPPI and CEN organizations have shown that past methods, such as ASTM D5802-95 or TAPPI T561, are unreliable due to high variability. Several variations of this method were also found to be insufficient. The inability to precisely measure and characterize the absorptive properties of tissue paper has resulted in an abandonment of any definitive test method standard. The evaluations by TAPPI and CEN focused on measuring the variability of various methods, equipment, and procedures, but they had little opportunity to understand why there was such variability. What is needed is an understanding of the mechanisms involved in the physical wicking of the tissues, and how these relate to the tissue absorbent properties. This paper will discuss both hardware and algorithm impacts on variability, and relate them to past round-robin evaluations that showed high variability. It will also highlight some of the fundamental shortcomings of existing techniques and suggest ways in which repeatability can be improved for testing of absorptive rate.