Mini-Encyclopedia of Papermaking Wet-End Chemistry
Part Two: Definitions and Concepts


Retention is a general term for the process of keeping fine particles and fiber fines within the web of paper as it is being formed. The word also can be used to describe the efficiency of retaining small particles, as in "a high level of retention was achieved on this paper machine." Retention can occur by various mechanisms. The simplest of these is mechanical sieving by the forming fabric. Once a fiber mat begins to form, the mat itself usually can act as a much more effective and finer sieve than the forming fabric. But even then, particles less than about 10 micrometers in size are not effectively retained by sieving. Rather, retention of fine particles requires the action of colloidal forces, including polymeric bridging or a charged patch mechanism. Retention aid chemicals can be effective either by attaching fine particles to fiber fines or fibers or by agglomerating them so that they can be sieved more effectively.

Request from the webmaster: Our goals include brevity and accuracy. Hopefully we have succeeded with the first goal without sacrificing the second. Please let us know right away if you find an error or omition. Also, please indicate points that need a clearer description.


Home page Research opportunities Business opportunities Background information Links to wet-end chemistry E-Mail
This page is maintained by Martin hubbe, Associate Professor of Wood and Paper Science, NC State University, .