A Decennial Record 47 



iitely undertaken. A special staff of chemists and assistants was 

 gathered together, and the necessary equipment installed. This virtu- 

 ally marks the laboratory's entrance into glue research. 



Within a reasonable time, high class glues of both types, ])lood 

 albumin and casein, had been worked out and made available to the 

 Bureau of Aircraft Production. Regular inspection and test of sam- 

 ples of plywood glued at various plants had been established early in 

 the study and was maintained as an aid to the manufacturers in mak- 

 ing a satisfactory product. Assistance was rendered them, also, by 

 trips of inspection and study at the individual plants. In addition to 

 the glues already mentioned, a special kind of blood albumin glue 

 tissue was invented. This is particularly adapted to the gluing of very 

 thin plywood, such as that used in the experiments on plywood wing 

 covering. In connection Mntli the glue work, special studies of the 

 supplies and quality of the raw materials entering into their manufac- 

 ture were undertaken. Through these, adequate quantities of suitable 

 material became assured. 



Propeller Work 



The effect of moisture upon the properties of wood was well 

 known, and it was generally accepted that the planes and their parts 

 should be manufactured at the moisture content which they would 

 assume in service. There were already in existence certain data show- 

 ing the relation between atmospheric humidity and the moisture in 

 wood, but these were not considered sufficient in view of the import- 

 ance of the matter. Therefore, several series of accelerated tests were 

 made, the results permitting the determining in advance of moisture 

 content tliat will be reached by any species under given atmospheric 

 conditions. 



Closely correlated with this study was an entirely dissimilar one, 

 planned to prevent change in tlie moisture content of propellers espe- 

 cially during storage under humidity conditions different from those 

 of manufacture or use. This investigation concerned itself princi- 

 pally with the various kinds of wood finishes and treatments with sub- 

 stances known to be water-resistant. Tests on many commercial 

 paints and varnishes showed that none of these were sufficiently re- 

 sistant to the passage of moisture through them, and there resulted 



