This method is designed to measure the weight percent fines content of paper stock or of pulp samples by means of a single-screen classifier. A modified procedure permits the use of the apparatus to measure the tendency of the fines fraction to be retained by the fiber fraction under graduated turbulent conditions.

 

Samples of paper stock, particularly those taken from the paper machine circulating system, are characterized by having different proportions of particles generally classified as "fibers" and "fines." The proportions of these two components may vary greatly, depending upon the furnish, upon stock preparation, and whether mineral fillers are added to the stock. The greater tendency of the fines fraction to pass through the wire during sheet formation and to be recycled leads to an accumulation of fines in the headbox. The extent of this buildup is an indication of the retention performance of the machine and affects, for example, drainage, felt filling, and saveall loading.

 

To perform adequate testing the sample must be representative of the system from which it is withdrawn. A minimum of five grams oven-dried pulp is needed to perform duplicate testing on each sample.