GROUND-WOOD PULP. 9 
The screened pulps from the centrifugal and the flat screen were 
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 beruninto 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 
trom 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 
