GROUND-WOOD PULP. 9 



The screened pulps from the centrifugal and the flat screen wore, 

 united and run out on an Improved Paper Machinery Co.'s 3-roll 

 hydraulic wet machine. The white water from the wet machine was 

 pumped back to the sliver screen of the grinder by means of a 4-inch 

 centrifugal pump. White water from the felts was run to the sewer, 

 as was also the white water from the felt suction. 



PAPER-MAKING EQUIPMENT. 



Portions of the pulps secured from experimental runs were sent to 

 the Forest Products Laboratory at Madison to be run into paper. The 

 apparatus available for the purpose when the earliest tests were made 

 consisted of a pulp shredder, 12-pound Emerson beater, 2-plate flat 

 screen slotted with 0.012-inch slots, and a 12-inch Fourdrinier paper 

 machine. Later a Noble and Wood's Jordan engine was added to the 

 equipment. This was used only, however, in the preparation for the 

 paper machine of pulps made from miscellaneous woods. The stock 

 which was run on the machine in carrying on series tests to determine 

 the effect of variable grinding conditions on the strength of pulp 

 was not jordaned. 



METHODS EMPLOYED IN EXPERIMENTAL TESTS. 



PREPARATION OF WOOD. 



All of the wood received at the laboratory was stored on skids in 

 the yard and in most cases allowed to season before being used. It 

 was received in several different forms; some cut from very large 

 trees was split before shipping; some was rossed in the woods; but the 

 greater part was in the form of round rough logs varying from 4 to 14 

 inches in diameter. The wood for test was sawed as required into 

 2-foot sections and barked, samples being taken for the determination 

 of moisture and dry weight per cubic foot. The amount desired for 

 the test was weighed and the diameter of each piece was measured. 

 Tests were conducted as soon as possible after the wood was prepared 

 and weighed. 



In some cases it was necessary to remove knots before grinding, 

 especially when the knots were likely to cause dirt in the pulp. This 

 procedure was more often required for jack pine and aspen than for 

 other woods. 



In case the wood was to be treated it was piled in the steamer after 

 having been carefully weighed. Depending on the conditions of the 

 cook, the pressure was maintained constant at the desired value for 

 different lengths of time. Cooks were made at steam pressures of 

 from 5 to 75 pounds per square inch and for different lengths of time, 

 from 1 to 12 hours. In some cases the wood was steamed and the 

 condensation was drawn off as it formed; in others, the wood was 

 immersed in water and boiled at different steam pressures, the 



