spreading, time in press — have been 

 isolated and evaluated, and the result 

 is that by proper observance of these 

 factors all commercial woods can today 

 be glued with animal, vegetable, blood, 

 or casein glue in joints that are stronger 

 than the wood itself. Woodworking 

 industries are applying the findings of 

 research, with corresponding benefit 

 to users, in better products, more eco- 

 nomical service, and reduced waste of 

 wood. 



Problems of far-reaching importance 

 that remain for investigation pertain 

 to the permanent water resistance of 

 glue joints and to fundamental improve- 

 ments in the nature of adhesives. 

 Glues that contain no water are being 

 developed. The active aid of research 

 is needed to make them cheaper, better, 

 and more generally adaptable. 



Veneer and plywood 



Plywood is sheet material made by 

 gluing together thicknesses of veneer 

 with the grain of successive layers at 

 right angles. Present-day utilization 

 trends point to increasing importance 

 of plywood in construction and fabri- 

 cation. Factors in its favor are its 

 strength, the uniformity of its prop- 

 erties, and the large lightweight units 

 in which it can be produced. There is 

 need for a more exact determination of 

 the properties of plywood as they are 

 affected by the kind, quality, and 



M-30142-F 



Mechanical spreading of glue. 



dimensions of veneer, the number of 

 plies, gluing and pressing technique, 

 and other manufacturing variables. 

 A comprehensive investigation of these 

 problems is under way. The sheet 

 material is obtained from the log in the 

 Laboratory's veneer-cutting plant. The 

 veneer is glued up into plywoods of 

 various types and thicknesses, which are 

 tested singly and in structural combina- 

 tions. The tests include determina- 

 tions of strength, resistance to weather- 

 ing, and moisture and heat diffusion, 

 as well as the effectiveness of different 

 glues and gluing methods used in mak- 

 ing the plywood. 



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