TAPPI T 213 om-21:2021 Edition

This method (1,2) is adapted to the numerical estimation of dirt in pulp and recycled pulp in terms of equivalent black area.
The results will differ from those obtained by TAPPI T 246 Foreign Particulate Matter in Pulp by Transmitted Light (now withdrawn) in that it is the contrasting color of foreign matter rather than its opaqueness that affects the result.
An automated procedure for dirt count can be found in TAPPI T 563 Equivalent Black Area (EBA) and Count of Visible Dirt in Pulp, Paper, and Paperboard by Image Analysis. Both this procedure and T 563 are based on Equivalent Black Area (EBA) measurement.