22 BULLETIN 309, U. S. DEPARTMENT OF AGRICULTURE. 
Screened pulp from the four cooks was combined into one beater 
charge, heated to about 40° C, and after being thoroughly mixed 
with bleach liquor to the equivalent of 21 per cent of its bone-dry 
weight of commercial bleaching powder, was pumped to a bleach chest 
to exhaust. When the bleach was practically all consumed and the 
Fig. 12.— Semicommercial rotary pulp boiler. 
color of the stock was found to be satisfactory, it was drained and 
washed free from bleach residues. 
The bleached stock was then beaten with a medium brush for 2\ 
hours, loaded with 25 per cent of clay, sized with a 0.5 per cent resin 
size and 2 per cent of alum, and run through a Jordan refiner and 
then to a 30-inch Fourdrinier paper machine speeded to 90 feet per 
minute. The stock acted very well on the paper machine, giving 
