176 FOREST UTILIZATION WOOD USES AND ECONOMICS 



pockets, or other defects, and should contain large quantities of avail- 

 able cellulose. 



The production of wood for pulp and paper is a most important 

 industry in eastern Canada and constitutes one of the important in- 

 dustries throughout the Northeast, Lake States, and in several sec- 

 tions of the South and Pacific Northwest. The principal requirements 

 for the location of pulpmills are: 



1. A large initial investment, frequently from $200,000 to $1,000,- 



000 or more. 



2. A large and continuous supply of good and reasonably priced 



wood. 



3. A plentiful and reliable source of clean water. 



4. Adequate power to operate the machines in a pulp and paper 



mill. 



5. Accessibility to a good fuel supply. 



6. Adequate and inexpensive transportation facilities for the ship- 



ment of the products to market. 



There are three methods of pulp manufacture as follows: 



1. Groundwood pulp or mechanical pulp, in which the wood 

 fibers are torn apart or reduced by mechanical abrasion. Spruce is 

 best adapted to this method. 



2. Sulphite method. This is the most important of the three chem- 

 ical methods of wood reduction. The wood is generally cut into 2-foot 

 lengths, chipped to small sizes, and reduced to a pulpy mass in large 

 digesters. The pulp is washed and screened and passed over a wet 

 machine or press to form continuous sheets of pulp. The sulphite 

 process is usually considered an acid process since the active pulping 

 chemical is sulphurous acid and its calcium salt calcium bisulphite 

 in aqueous solution. 



3. Sulphate pulp. This is a more recent method of chemical re- 

 duction of wood fibers and is applied chiefly to southern pine as well 

 as hemlock and some other species. Much sulphate pulp is imported 

 from northern European countries to add to our local supplies. Much 

 Kraft paper is produced in the South by this process. After chipping, 

 the wood is digested under pressure in an alkali liquor containing so- 

 dium sulphide and caustic soda. These agents combine to reduce in 

 the cooking process to form pulp which is run through press rolls and 

 formed into bundles. Then after drying it is sent to the paper mill. 



4. Soda Process. This is like the sulphate process an alkali 

 pulping method but is applied chiefly to hardwoods, such as aspen, 



