A NATIONAL PLAN FOR AMERICAN FORESTRY 1375 



of having lumber drier than can be obtained by air seasoning in 

 regions where the products are used in heated houses. For such 

 regions and purposes lumber must of necessity be kiln-dried even if 

 it is first air-dried. 



Comparatively large and unnecessary losses are still incurred in 

 current kiln-drying processes. Investigations to determine the causes 

 and remedies for such losses have been under way for a number of 

 years. A reasonably satisfactory empirical understanding of the 

 manner in which seasoning defects are brought about and of ways 

 in which they can be avoided or remedied has been obtained. The 

 general effect of variations in the controllable conditions is sufficiently 

 understood to make it possible to draw up reasonably satisfactory 

 drying schedules. For the more common lumber products such 

 schedules have been developed in the Forest Service for about 50 

 important American species, and additional schedules are being 

 worked out. 



An important cause of present poor drying practice lies in inade- 

 quate kilns and equipment. Research on drying schedules has 

 carried with it the development of several new types of kilns and 

 the perfection of control apparatus which have become standard 

 equipment in the industry. As the drying of special forms, shapes, 

 and sizes becomes more common, corresponding progress in drying 

 equipment will have to follow. 



A number of important seasoning problems still remain unsolved. 

 Most of the work hitherto has had to do with lumber and other 

 comparatively thin material. But ties and timbers of most species 

 suffer excessive degrade during seasoning, with a corresponding loss 

 in value. Many special sizes and shapes of dimension stock of various 

 species still require study before satisfactory drying methods can be 

 had. Certain groups of species cannot be satisfactorily seasoned by 

 any known methods. Among these are southern swamp oaks and 

 some of the other southern hardwoods. It becomes necessary, there- 

 fore, to develop some new and radically different method of seasoning 

 which will permit this material to be seasoned in a reasonably satis- 

 factory manner. Experiments now under way give some promise. 

 It is quite within the realm of the possible that new methods may 

 become applicable to all classes of wood products and may revolu- 

 tionize the entire art of seasoning, with tremendous benefit to pro- 

 ducer and consumer alike. 



A large percentage of lumber and other timber products will for 

 many years to come be air seasoned despite any conceivable develop- 

 ments in the kiln-drying processes. Commercial air seasoning is 

 exceedingly variable, has a large rule-of- thumb element, and has 

 been too largely without investigative basis. While it is obviously 

 impossible to vary the conditions to which the stock is exposed, it 

 is possible to control the extent to which these climatic conditions 

 affect the stock by varying such factors as the size and shape of the 

 lumber pile. 



The development of antiseptic chemical dips to minimize stain and 

 decay, particularly during air seasoning, is a matter of immediate 

 practical importance. The extent to which air seasoning loss can be 

 reduced by such means and by proper yard practice varies consid- 

 erably with the type of mill. Large mills can feasibly reduce damage 

 to a negligible point if they so desire ; small mills, on the other hand, 



