TAPPI T 213 om-15:2015 Edition

This method 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results will differ from those obtained by TAPPI T 246 "Foreign Particulate Matter in Pulp by Transmitted Light" (now withdrawn) in that it is the contrasting color of foreign matter rather than its opaqueness that affects the result.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.

This method provides a test for estimating the amount of dirt in pulp including recycled pulps to help the mill meet its needs for production of fine or other speck-free papers.

The estimated equivalent black area of a gray or colored speck is smaller than its actual area, in inverse proportion to the intensity of its color contrast with its background. Thus, the equivalent black area of a black spot in a nonbleached pulp would be considerably smaller than its actual area because its appearance would not be as pronounced as it would be if it were in a white pulp.