THE DRY KILN AND CONSERVATION 



BY E. W. TREEN, B. S. F. 



DURING these days when conservation of our natural 

 resources, particuhirly our forest resources, is 

 preached right and left, it seems to the writer that 

 not enough stress is put on the subject of conservation for 

 the benefit of the present generation. This is not inferred 

 as a detriment to our future generations, but as a direct 

 aid to production for their benefit in the future. 



Forest conservation seems to be mainly dependent, 

 according to the writer's jioint of view, on three things, 

 namely, reforestation ; protection from external agencies, 

 as fire, ruthless lumbering, etc., and closer utilization of 

 our present cut. This article deals with a phase of the 

 last of the three, a phase which is not very familiar to 

 the public at large, the dry kiln as a phase of utilization. 



The dry kiln is the only practical means we have at 

 present of drying lumber fast enough to insure the wood- 

 working industries a profit in the shortest possible time 

 after the raw material is obtained. Kiln-drying is really 

 the first step toward the finished product after the rough 

 lumber stage is passed. The condition of the kiln output 

 is in direct proportion to the good or bad condition of 

 the finished product. By this is meant that if badly 

 dried lumber starts through the processes of manufac- 

 ture, all results of these processes will be damaged to 

 the same extent. 



A mere mention of a few important industries depend- 

 ent on kiln-dried lumber will bear out the magnitude of 

 the subject. First of all, is the manufacture of furniture, 

 in which the United States holds a very high place in the 

 world's market. Then we may mention the manufacture 

 of flooring, auto bodies, toy production, and several other 

 related industries. To provide for the wants of these in- 

 dustries, several standard dry kilns are on the market, 

 most of which will give good results if properly handled. 

 The Forest Products Laboratory at Madison, Wisconsin, 

 is doing yeoman service in experimental work in the dry 

 kiln line, but the results of these investigations do not 

 reach nearly as many of our people as they should. 



The basic principles of successfwl dry kiln operation 

 have been mentioned time and again, namely, control of 

 circulation, hinnidity, and temperature. It is not the 

 writer's idea to discuss these princi])les again, but to men- 

 tion a few different phases, which he has seen in his 

 travels as a dry kiln engineer, trying to show that these 

 cardinal points are more often discussed than applied. 



First and foremost is the man who operates the dry 

 kiln, the dry kiln engineer, for, if he understands his 

 business he is an engineer in the highest sense of the 

 .word. When the Forest Service employs highly technical 

 men in dry kiln investigation, and practically all our for- 

 estry colleges are giving courses in drv kiln engineering, 

 it is a pretty good indication that there is more to the 

 game than simply turning steam into a brick building, 

 and leaving the lumber therein to work out its own salva- 

 tion. As a profession dry kiln engineering offers more 



opportunity for successful research, in the writer's esti- 

 mation, than most of the engineering professions. Here 

 are the prime requisites of the successful dry kiln engi- 

 neer : He must know wood in all its phases, as to species, 

 wood structure, working qualities, sensitiveness to out- 

 side agencies, as heat, moisture, etc. ; he must have a 

 thorough knowledge of thermo-dynamics, and a knowl- 

 edge of how the different species are affected by the 

 different heat agencies. 



To assume we have the man suitable for the job, here 

 is one reason why this man is not getting the success he 

 should be getting. It is the interference of those higher 

 up in the business. As an example may be stated the 

 case of the dry kiln engineer at many of our large furni- 

 ture factories here in Michigan. The superintendent 

 complains to him that 6/4 red gum on being worked, 

 shows a deal of warping and signs of checking. This 

 gum contained thirty per cent of moisture when placed in 

 the kiln, and the operator knows that it will take at least 

 fifteen days to dry it effectively. But the shop foreman 

 wants it rushed through in ten. The operator does as he 

 is told, although he knows what the result will be, and he 

 is blamed when the results are seen. To insure success, 

 the operator must be absolute master of his kilns, and, 

 within reason, should be troubled by no outside interfer- 

 ence. If many employers would think of this a little 

 more, many "unexplainable" dry kiln defects might be 

 remedied. We realize that the superintendent wants his 

 jjroduct on the market as quickly as possible, which is 

 very easy to understand, but the effective working of 

 the parts will insure the success of the whole. 



Too often, also, a man is picked from the working 

 force of the factory, to operate the dry kilns, a man who 

 knows part of the process, but does not know, or does 

 not care to know, other essential parts. The engineer is 

 often picked to have charge of the dry kiln operation. 

 Oh, yes, he understands his boiler capacity in fine shape, 

 can furnish all the steam and spray required, keep his 

 valves and pi])ing in first class shape, but does he know 

 the wood he is drying ? Too often, no ! As long as the 

 temperature doesn't run too high, he thinks there is no 

 cause for worry, and all the time the lumber is shrinking, 

 warping and checking, until it comes out looking as if a 

 tornado had been through it. This state of affairs can 

 be remedied. If the employer doesn't want to pay the 

 salary required by a first class operator, at least he can 

 select a man who is interested in his job, and is willing 

 to learn. Results have shown this is a surely wise policy. 



The testing of the lumber is also too often neglected. 

 From the writer's experience he has found that the gen- 

 eral practice is to test the lumber for moisture content 

 and shrinkage after it is supposed to be dry. At least 

 four tests should be made to insure a perfect drying 

 schedule, i. e., just before the charge is placed in the 

 kiln, after the steaming period, at least once during the 



