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BULLETIN 322, U. S. DEPARTMENT OF AGRICULTURE. 



The short fibers or cells are not sufficiently long or correctly pro- 

 portioned and shaped to possess the felting quality on which their 

 value largely depends in paper manufacture; moreover, in distinc- 

 tion from the long bast fiber, they are liquefied, which renders them 

 very undesirable in the manufacture of durable products. 



The separation of the dirt and short fibers from the long true 

 fibers was accomplished in the laboratory, as in practice, by means 

 of a washer, which is a rotating drum covered with 20-mesh wire 

 cloth on the sides and having helical scoops inside connecting with 

 a hollow trunnion. This washer is attached invariably to the beater 

 and by being lowered about one-third its breadth into the circulat- 

 ing stock it removes water, dirt, and short fiber, while fresh water is 

 admitted at the other end of the beater. 



Fig. 3. — Paper-testing machines in a constant-humidity room. 



Obviously, this light beating and washing should be carried to 

 different degrees, depending on the quality of the product desired. 

 For example, a medium grade of fiber board would not require as 

 much washing as one of higher grade and a stock suitable for wrap- 

 ping or sack paper would require a very complete washing. 



After having been washed to the desired degree, the stock is 

 drained from the beater, pressed, weighed, and sampled fo*r a mois- 

 ture determination, in order to calculate the 3 T ield of the washed fiber. 

 It is then returned to the beater, and the long true fiber is reduced 

 to a degree which is suitable for manufacture into a sheet of paper. 



All sheets were made waterleaf on a hand mold 5-| by 10 inches, 

 dried on a steam-heated cylinder at 105° C. under a definite tension, 

 and subsequently given physical tests under constant conditions of 

 temperature and relative humidity. 



To show the effect on the physical constants of a paper caused 

 by drying the wet handmade sheet under different tensions, the re- 



