Mini-Encyclopedia of Papermaking Wet-End
Part Two: Definitions and Concepts
The word "fines" most often means small cellulosic materials that are small enough to pass through a forming fabric. A TAPPI Useful Method defines fines as objects small enough to pass through a conical hole having a minimum diameter of 76 micro-meters. Fiber fines have two main origins. So-called "primary fines" consist of parenchyma cells and other small cells that exist within the wood. Kraft pulping releases them as intact, rod-like objects. By contrast "secondary fines" are produced by refining. A typical secondary fine tends to be ribbon-like. Secondary fines tend to favor strong inter-fiber bonds. Both types of fines tend to hurt drainage. It is worth keeping in mind that none of the preceding definitions deals with recycling of paper. It has been suggested that secondary fines, after they have been recycled, act more like primary fines in terms of their effectiveness at increasing paper strength. Some papermakers also include filler particles and other suspended material in the category of "fines."
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