1374 A NATIONAL PLAN FOR AMERICAN FORESTRY 



In the case of a highly variable material such as wood, it is quite 

 obvious that selection is the key to refinement, but in the case of 

 lumber the basis of selection has never been adequately developed. 

 Use requirements are met at present largely on the basis of the species 

 and rather arbitrary grades determined by the occurrence of knots 

 and the like. But a species possessiong high average shock-resisting 

 properties, for example, has been proved by tests to yield substantial 

 proportions of material no higher in shock resistance than species of 

 much lower rating. The same applies to all the other properties of 

 wood. For any assurance of getting qualities required, the consumer 

 has had to rely heavily on the reputation of the supplier and of the 

 locality of growth. In the noncompetitive era for lumber such prac- 

 tice may have sufficed, but it can hardly be expected to serve for the 

 future. Research has established that the specific gravity test, which 

 can be readily applied, is a good working index of many strength 

 properties and a sound basis for classifying material of any species 

 into high, low, and intermediate groups. New values will be realized 

 as wood of low density is sent to those that want low density and 

 wood of high density to those that want high density, rather than a 

 mixture of all kinds to all users. 



Experiments are under way to develop a strictly portable instru- 

 ment for getting an instantaneous measure of the hardness of wood 

 as an index of specific gravity. Such an instrument in the hands of 

 a commercial grader will pave the way for radical improvements in 

 selection to meet use requirements. Within the last 2 years an in- 

 stantaneous tester for moisture content has been developed from 

 fundamental work on the physics of wood. This instrument, now 

 being sold by several makers, has led to marked improvements in 

 providing consumers with properly seasoned lumber. Its further 

 adaptation, together with a fuller development of moisture-content 

 specifications, holds promise of removing many complaints against 

 lumber. 



Other reliable commercial tests are needed to measure and select 

 for decay resistance, freedom from swelling and shrinking tendencies, 

 toughness, resistance to abrasion, and many more properties in which 

 wood exhibits a great variation. Aside from selective tests, science 

 needs to provide ways of evaluating all the properties of wood so as 

 to suit it more exactly to the purposes intended. The facts recently 

 established as to the characteristic defects of the important softwood 

 species need to be taken into account in the fuller development of 

 use grades. 



SEASONING 



Poor seasoning has been the cause of much dissatisfaction with 

 lumber and has resulted in heavy loss of markets. Great advance 

 in recent years has been made as a result of research, but many prob- 

 lems still remain to be solved before seasoning is put on a basis that 

 permits lumber to compete to its best advantage. Both artificial 

 seasoning in dry kilns and natural seasoning in the open air are 

 involved. 



The need for kiln-drying arises from two main requirements. One 

 is economic to reduce freight costs, to reduce the quantities of lum- 

 ber held and hence the investment, to reduce seasoning losses, and 

 to fill orders on short notice. The other is physical the necessity 



