THE SUITABILITY OF AMERICAN WOODS FOR PAPER PULP 19 
was very satisfactory. With jack pine and pond pine the screen- 
ings ran from 3 to 6 per cent — which, however, is not prohibitive. 
Northern white pine, sugar pine, limber pine, and pinon are all 
capable of manufacture into mechanical pulp of excellent quality. 
In the sulphite process, however, penetration by the cooking liquors 
is very slow and the results are unsatisfactory. All the pines reduce 
readily under the alkaline processes and produce pulp that may be 
bleached, although the product is less satisfactory than the standard 
bleached sulphite pulps. 
Larches, Douglas fir, southern cypress, and cedars with light- 
colored wood can be pulped by the sulphite process, although with 
-Combination cylinder and Fourdrinier paper machine upon which the paper samples 
were made 
more difficulty than hemlock. The quantities of bleach required are 
high but are within the range of commercial feasibility. None of 
these woods has been satisfactorily reduced by the alkaline proc- 
esses to pulp bleachable with a reasonable quantity of bleach. 
Southern cypress is the most difficult. Redwood and cedars with 
dark-colored wood are very difficult to pulp or to bleach by the 
sulphite process. Consideration of the mechanical processes for 
these woods is not warranted, owing to their dark color. Their light 
weight and consequently the low yields obtained discourage consid- 
eration of them for the alkaline processes, although very satisfactory 
pulps for unbleached wrapping paper can be obtained. 
