UTILIZATION OF DOGWOOD AND PERSIMMON 
23 
draft; others are using kilns in which the humidity, the tempera- 
ture, and the circulation of air can be in some measure controlled. 
Those factories where the control of humidity, temperature, cir- 
culation of air, or all three, is being attempted obtain the best 
results. Complete success is only possible through a thorough 
understanding of the principles of kiln-drying. 
The drying of green wood .to 25 per cent moisture content is 
rather a simple matter; the drying from 25 per cent to 7 per cent 
is somewhat more difficult, but can be done by an operator who has 
a good understanding of the seasoning of wood. 2 
«U# lir "'- 
Fig. 16. — Stacking dogwood blocks in an open-air shed for seasoning 
Experimental work in commercial-sized condenser kilns at the 
Forest Products Laboratory, Madison, Wis., in seasoning solid 
round sticks or stems of perfectly green dogwood up to 3% inches 
in diameter showed that they could be dried without checking in 
65 to 70 days, moisture content being reduced from 85 per cent to 
10 per cent of the oven-dry weight of the wood. In a well-regulated 
condenser kiln green shuttle blocks 2 by 2 by 18 inches can prob- 
ably be dried from the green condition, say, 85 per cent moisture, 
to 7 or 8 per cent in 50 to 60 days. Shuttle blocks 2 by 2 inches 
previously dried to 15 per cent in the air can be kiln-dried to 7 per 
cent in 12 days. 
Wood dried to a low moisture content, such as 7 or 8 per cent, 
because of the high temperatures used may lose to some degree its 
ability to reabsorb moisture. By drying shuttle blocks to 7 per cent 
or lower, therefore, the tendency to subsequent swelling, twisting, 
and warping due to reabsorption is lessened. 
m 2 An excellent manual for the operator who wishes to studv this subject is Kiln Pry- 
ing Handbook, by Rolf Thelen, U. S. Dept. Agr. Bui. 1136. '64 pp. 1923. 
