THE FORESTER. 207 



the aluminum-leaf process developed at the laboratory were the only 

 ones to arrive in satisfactory condition. This method has been 

 officially ado])ted by the Army and Navy. 



The experiments study of the conditioning and manufacture of 

 airplane T)ropelIei*s began to yield information of great value. At 

 the completion of the study it will be possible to specify accurately 

 the species of wood and tne manufacturing conditions for the pro- 

 duction of the most efficient propellers for the many kinds of service. 



A number of new and greatly improved formulas for making 

 waterproof glues for plyw'ood manufacture were developed. One 

 of these for casein glue shows about double the water resistance of the 

 available commercial casein glues and is very resistant to molds. 

 The specifications of the Army and Xavy for all glue and glue ingredi- 

 ents were })repared at the laboratory. Much of the work on glues 

 was carried on for the purpose of preparing these specifications. 

 Several conmiercial concerns have adopted the laboratory glues in 

 production. Numerous improvements were discovered in plywood 

 manufacture that have also been successfully adopted in production. 



There were identified 30,863 samples of wood, including some 

 foreign woods, and many microscopic examinations for decay and de- 

 fects were made. Information illustrating defects in wood was col- 

 lected, and an illustrated key for distinguishing true mahogany from 

 so-called mahoganies was prepared for propeller inspectors. Studies 

 were made of the effect of moulds on wagon ancl airplane woods, 

 and of the effect of steam bending on the structure of wood. 



Active work on tlie value of various woods for paper manufacture 

 was discontinued during the war to devote more time to j)ressing war 

 problems. However, a reliable method for determining the tearing 

 strength of paper was developed. A recording density hydrometer 

 was invented which will be oi considerable use in the control of the 

 soda recovery of sulphate and soda pulp mills, acid making in sulphite 

 miUs, mixing in the manufacture of ledger, bank-note, and other 

 fine pa})er, and in the chemical and textile mdustries in general. The 

 value of waste hemlock bark from paper mills as a source of tannin 

 was also demonstrated. Methods for the production of soda and sul- 

 phate pulps suitable for nitrating and for rendering sulphite pulps 

 suitable for this use were developed. 



Shortly after the armistice Avas signed the Salvage Board of the 

 Ordnance Department requested the laboratory to determine the 

 suitability of second-cut cotton linters and hull fibers for paper 

 manufacture. The War Department had on hand at that time a 

 large tonnage of these linters reserved for the manufacture of nitro- 

 cellulose and was seeking the best means of disposing of the surplus. 

 Commercial pulping trials and paper runs made at the laboratory 

 soon demonstrated that second-cut linters and hull shavings can be 

 pulped with decidedly less chemical and bleach consumption than 

 wood, and that they are excellently adapted for the production of 

 high-grade book, writing, blotting, tissue, and other papers. These 

 experiments may well have a far-reaching economic influence on the 

 future of the paper supply of this country. Arrangements have been 

 made for a practical mill trial where the value of this raw material can 

 be demonstrated on a tonnage basis under average mill conditions. 



The laboratory cooperated with the Chemical Warfare Service of 

 the Army in gas defense work and developed an artificially dense 

 wood charcoal pratically the equal of coconut-shell charcoal. A 



