Testers or image analyzers count dark specks over a defined area, size them against a chart of standard dots and report the total as equivalent black area in parts per million or square millimeters per square meter. Sources include bark, shives, ink particles, rubber, plastic and rust. Dirt count is a headline spec for market pulp and recycled grades, where deinking performance shows up directly.
Dirt count doubled on the recycled line, mostly toner specks the flotation cells didn't catch.
Also heard as
- dirt
- speck count
Related terms
Shive
Small bundle of fibers that were never separated during pulping, seen as a splinter-like speck in paper.
Furnish
The recipe of pulps, fillers, dyes and chemicals that make up a paper grade's stock.
Light-absorption coefficient
Per-grammage measure of how much light a paper absorbs, written k and given in square meters per kilogram.