drying, and under proper safeguards it 

 remains the most economical method 

 for many hardwoods and the bulk of 

 lower grades of softwoods. Long series 

 of tests have shown the common sources 

 of loss and damage in this field and 

 Anoans of bringing them under control. 

 Important factors determined are prop- 

 er exposure of the pile with respect to 

 sun and wind, proper spacing of lumber 

 at different stages of drying, adequate 

 support to prevent warping and bend- 

 ing, and measures to prevent stain and 

 decay, including elevated pile founda- 

 tions and proper yard drainage. 



Kiln-drying 



The development of the lumber dry 

 kiln arose from the need of speeding up 



the seasoning process. Very generally, 

 however, its use has been attended with 

 serious problems and variable results, 

 owing to the lack of precise technique. 

 The Laboratory's kiln-seasoning in- 

 vestigations are centered on underlying 

 physical principles, together with the 

 development of apparatus and methods 

 to perform the drying efficiently. A 

 number of completely equipped experi- 

 mental dry kilns with accurate control 

 of temperature, humidity, and air cir- 

 culation are in constant use to test every 

 desired variation of conditions in the 

 seasoning of sample lots of lumber. 



Substantial accomplishments are 

 shown as a result of the work thus far. 

 Practical methods have been developed 

 for seasoning the principal commercial 

 hardwoods and softwoods, many of 



Wood samples are removed and weighed to determine moisture conditions in walls. 



M-31609-F 





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