Dirt in pulp – chart method

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.