118 Forest Club Annual 



width, and 11 to 12 feet in height. Most of them are divided 

 into from one to six chambers, and in some cases even more. 



In the matter of construction various materials are used. 

 Many of the old kilns are of wood, but because of the fire danger 

 that continually attends them they are going into disuse. They 

 were easily and cheaply built. Kilns of brick, tile and concrete 

 are extremely serviceable and are easily made air-tight, a neces- 

 sary requirement for conserving the heat. Constructed from 

 either one of these materials they become less susceptible to 

 fire than those of wood, and that is a feature a lumberman must 

 always have in mind. 



The question naturally arises as to why the mill owner goes 

 to the expense of constructing a kiln and then adds to the cost of 

 milling by running the lumber through it. He does so for two 

 reasons, namely, to reduce the weight, and to reduce the moisture 

 content of the lumber. In passing through the kiln the moisture 

 content of Douglas fir is reduced from 30 to approximately 7 per 

 cent, Sitka spruce from 37 to 8 per cent, hemlock from 70 to 10 

 per cent, and western red cedar from 65 to 10 per cent. If re- 

 duced below 10 or 12 per cent the wood generally reabsorbs 

 moisture from the air, thus bringing the moisture content back 

 to the 10 or 12 percentage. The decrease in weight of the various 

 woods is therefore evident. To reduce weight means a decrease 

 in the shipping costs, and this is a big item since much of the 

 lumber is shipped eastward over the mountains where freight 

 rates are high. Moreover, in handling, by reason of the lighter 

 lumber, the expense is further decreased. 



In reducing the moisture content many of the lighter oils 

 contained in the pitch are volatilized. The pitch is then hardened 

 and does not ooze out when the lumber is painted. Kiln-dried 

 wood does not shrink or become deformed after being manufac- 

 tured as does air-dried materials and when dampened it does not 

 have a tendency to absorb enough moisture to increase in weight. 



Of the many different styles and types of dry kilns, the one 

 connected with the sawmill of the Grays Harbor Commercial 

 Company, Cosmopolis, Washington, has been selected for special 

 study. This is located in the well known Grays Harbor country. 

 With the exception of Sunday the mill operates day and night, 

 and has a day capacity of 200,000 feet and a night capacity of 

 100,000 feet. The kiln, however, is never idle; it is busy all the 

 time, Sundays included. A box factory and lath mill are 

 operated in connection with the plant. For boxes spruce is 

 used almost exclusively and for that reason about two-thirds 



