Dirt in paper and paperboard, Test Method TAPPI/ANSI T 437 om-21
This method (1-3) is suited for the visual estimation of dirt in paper or paperboard in terms of equivalent black area. For dirt in pulp, see TAPPI T 213 “Dirt in Pulp.”
This method is a visual inspection method for the evaluation of the Equivalent Black Area (EBA) measurement of dirt in paper and paperboard. An equivalent instrumental method using image analysis for the measurement of dirt in pulp, paper, and paperboard in units of parts per million is given in TAPPI T 563 “Equivalent Black Area (EBA) and count of visible dirt in paper and paperboard by image analysis.” T 537 “Dirt count in paper and paperboard (optical character recognition - OCR)” reports the number of specks of 0.02 mm2 or larger per square meter.