FOREST PRODUCTS LABORATORY. 1 7 



In treating operations, the cost of the preservative, such as creosote, 

 zinc chloride, or sodium fluoride, amounts to a high percentage of the 

 total cost. Furthermore, the ultimate success of any treatment is 

 largely dependent upon the preservative used. Much information has 

 already been obtained concerning the preservatives now in common 

 use, but there is need for a great deal of further study with the object 

 of developing new preservatives which will either be cheaper or more 

 effective than present preservatives or will have properties fitting 

 them for wider use or for special purposes. The value of a preservative 

 is not considered 'established until it has had a thorough trial under 

 actual service conditions. 



GLUES FOR PLYWOOD. 



In connection with the manufacture of plywood, studies have been 

 made of animal glues, such as those made from hide, bone, and other 

 products; and standard methods of testing have been developed. A 

 suitable "standard glue" for aircraft work and high-class joint work in 

 general has been selected and samples made available to manufacturers 

 and users. This is the glue adopted as standard by Army and Navy 

 aircraft bureaus. 



The development of water-resistant glues of several types, including 

 casein glues and blood-albumin glues, has been progressing for several 

 years, and a number of high-grade glues have been perfected. Tests 

 and experiments are being carried forward to improve these glues still 

 more, especially in their resistance to moisture. 



LAMINATED AND BUILT-UP PARTS. 



One of the lines of investigation to be taken up recently is the deter- 

 mination of possibilities and best practices in the design and construction 

 of structural members built up of small pieces glued together. These 

 investigations were carried out intensively on aircraft parts, such as 

 wing beams and struts, when the success of the aircraft program was 

 threatened by a sudden shortage of suitable material in the required 

 sizes. The knowledge gained is being applied to extensive investigations 

 of the use of laminated and built-up construction in the various wood- 

 using industries for the manufacture of such articles as shoe lasts, hat 

 blocks, bowling pins, wagon bolsters, and wheel hubs. 



The Laboratory has done considerable work on the moisture resistance 

 of various wood coatings, and a very efficient aluminum leaf coating has 

 been developed which affords protection against moisture over long 

 periods of storage. Tests are now in progress on the durability of these 

 coatings. Other work on wood finishes is contemplated. 



