!nay 10, 1919 



HARDWOOD RECORD 



19 



Brain Work in Kiln Operation 



The Best of Kilns Will Give Mediocre Results With Poor Opera- 

 tors. The Human Factor is the Most Important Consideration 



By C. V. Sweet 



There is no phase of kiln-drying that stands out more clearly as 

 essential to success or directly responsible for failure than the intelli- 

 gence and attention that is given to the operation of the kiln. Those 

 who have watched with particular interest the progress of the practice 

 of kiln-drying lumber especially under the stress of war conditions, 

 have seen that the greatest difference between success and failure has 

 been in the operation more than in the kilns themselves, whether it has 

 been with airplane stock, green oak vehicle stock, ship timbers, or 

 wooden legs. Poor kilns and good operation have often produced as 

 good results as good kilns and poor operation. But in the long run, 

 the big problems of artificially seasoning lumber will be solved only 

 by a happy combination of the two factors. It takes a good kiln 

 and good operation to obtain really good results. 



It has frequently been brought to the attention of the Forest 

 Products Laboratory of the United States Forest Service at Madison, 

 Wis., that with a given type of dry-kiln, handling similar kinds of 

 stock according to the same recommended schedule, one concern has 

 dried its material with practically no loss while another suffered a 

 loss of 40 to 50 per cent. 



If the art of kiln-drying lumber has come through its recent trials 

 trimmed of some non-essential ideas and benefited by new conceptions, 

 the sum total of our information concerning it has been greatly in- 

 creased. On the other hand, if there is still a vestige of the old 

 notion that "this kind of kiln will dry lumber in half the time and 

 less checking than that kind of kiln," a big load of inertia must 

 still be moved. 



Emphasis on the operation of the dry-kiln means the injection of 

 the human, intelligent, interested element into kiln-drying which is 



too frequently absent in the methods of many concerns. The kind 

 of kiln operation that is possible at the hands of an ex-lumber piler 

 who has become too old to work efficiently anywhere else, or of a 

 man who has grown up with the company and in his later years de- 

 serves an easy job, or of a fireman at the plant who has a few extra 

 hours to fill in — that kind of kiln operation does not enter into this 

 consideration. 



The kiln-drying of lumber, unless it be the drying of air seasoned 

 soft woods, is an art involving special knowledge, skill and good 

 workmanship. Without detracting from the credit of the practical 

 lumbermen, it may be said that the greatest advances in kiln-drying 

 have come in the last few years. This advance, reflected in new 

 methods of seasoning, is the outgrowth of accumulated scientific 

 knowledge of the physical and mechanical properties of wood. The 

 successful dry-kiln operator today has to think of characteristics of 

 wood in terms which are unfamiliar and in many instances distasteful 

 to the older type of practical lumbermen. 



As a matter of fact this conception .of the role of operation in kiln- 

 drying is opposed to a more or less general commercial tendency to 

 make kiln-drying an automatic process from which the element of 

 personal judgment is removed as much as possible, thereby attributing 

 to dry-kUns in themselves whether of one particular design or another 

 some mystic, secret capacity to dry lumber perfectly with the minimum 

 watching by a competent operator. Or often lumber is supposed to be 

 dried successfully by some so-called "patented process." Sad experi- 

 ence shows that it is impossible to put lumber in a dry-kiln like a 

 potato in an oven and take it out all done to a queen's taste. 



It is not uncommon to read in advertisements in trade journals that 

 this or that kind of dry-kiln or process dries lumber without checking, 

 honey-combing, or easehardening. Such a statement is the danger 



Sketches of representative commercial installations of a type of pro- 

 gressive kiln In which the circulation of air is from end to end. Note that 

 in end piUng the "stickers" oppose and obstruct the intended circulation. 



Both end and cross piling are often used in this type of kiln, but cross- 

 piling Is distinctly superior to end piling, from the standpoint of circulation. 

 This Illustrates the lack of attention to a very Important item of kiln 

 drying. 



Sketches of representative commercial installations of a type compart- 

 ment kiln in which the circulation of air is up in the center and down and 

 out at the sides. Cr'oss piling places greatest obstruction to this system 

 of circulation. At one plant the lumber is piled crossuHse and at the other 

 is piled endunse. There is only one of the two methods which can be right. 

 Another illustration of failure to give attention to circulation in the kiln. 



