which were previously considered in- 

 capable of being kiln-dried from the 

 green condition. The engineering de- 

 sign of dry kilns has been radically 

 improved. More than 5,000 commer- 

 cial kilns embodying principles devel- 

 oped at the Laboratory are in opera- 

 tion, and new installations so designed 

 by far outnumber all other types. 



It is estimated that improvements 

 in kiln seasoning resulting from the 

 Laboratory's research are already sav- 

 ing American wood users more than 

 $10,000,000 annually, and even larger 

 savings are possible as the findings are 

 more widely applied. Further investi- 

 gations are under way toward the adap- 

 tation of kiln practice to many difficult 

 species and to special sizes, including 

 precut dimension stock. Work has 

 begun on a broad program of research 

 to correlate the more severe conditions 

 of drying with their effects on wood 

 quality, with the aim of setting up 

 higher ranges of speed for the safe kiln 

 seasoning of all species. 



A necessary supplement to seasoning 

 research is the improvement of methods 



of lumber storage and handling. Ail 

 the care expended in the original drying 

 may be wasted because of reabsorption 

 of moisture by the stock while in 

 transit or awaiting sale. Studies of 

 this problem are pointing the way to 

 better protection of lumber at all stages, ^ 

 from the mill yard to the finished^ 

 structure. Special attention is being 

 given to control of moisture content of 

 lumber in closed sheds. 



Chemical seasoning 



The steeping of wood in a salt solu- 

 tion preliminary to drying in the kiln 

 or in the yard offers a new approach to 

 the most difficult seasoning problems. 

 The treatment brings about a state of 

 moisture equilibrium in which the wood 

 dries from the center outward, reversing 

 the usual direction, and in the final dry 

 condition the salts absorbed act in some 

 way to hold the wood against shrinkage 

 and change of shape. By this method 

 large timbers have been dried practi- 

 cally without checking — a result never 

 before attained — and wood of several 



Salt treatments offer new means of seasoning the most difficult wood species. 



M-31514-F 



