12 BULLETIN 1437, U. S. DEPARTMENT OF AGRICULTURE 
In air seasoning red alder special attention should be given to 
the character, number, and placing of the stickers if the degrade is 
to be kept to the minimum. Piles should never be " self-stuck " 
where the lumber is to be left in this condition for any length of 
time. ^ Where the lumber is to be partially or wholly air seasoned, 
the stickers (usually made of Douglas fir) should preferably be 1 
inch, thick and 2 or 3 inches wide and thoroughly seasoned. Too 
much care can not be exercised here, for it seems that under the best 
possible conditions for air seasoning alder will end check to some 
extent. End checking may, however, be reduced to a minimum by 
placing the outer stickers so that they project slightly beyond the 
ends of the boards. (Fig. 4.) This will also tend to prevent the loss 
through splitting likely to occur when there is a considerable over- 
hang at the end of the pile. The distance between stickers should 
not exceed 4 feet, for warping of the lumber often results when they 
are placed farther apart. (Fig. 4.) 
The rate of drying in the air varies, of course, with the season, size 
of stock, and method of piling. To air dry red alder lumber thor- 
oughly to a moisture content of 14 to 18 per cent requires from 6 to 9 
months. 
Although natural-draft kilns, either of the progressive or com-- 
partment type, are generally used in the artificial drying of red alder 
lumber, the fact that other types of kilns are not used more exten- 
sively with this species has no special signficance. Lumbermen of 
the Pacific coast region are possibly more familiar with the natural- 
draft kiln. Then, too, it is the cheapest type to install. The fact 
that a progressive kiln with relatively lower flexibility and accuracy 
of control can be used satisfactorily indicates that red alder is not a 
difficult wood to dry. Operating instruments are in most cases lim- 
ited to temperature recorders. In addition, humidities are occa- 
sionally determined by means of a wet and dry bulb hygrometer. 
The practice in kiln-drying alder is to fiat pile the lumber, leav- 
ing 2 to 4 inch spaces between the boards in a layer. The amount 
of space to leave in any particular case is a matter of judgment and 
depends on the circulation. When the circulation is poor, resulting 
in uneven drying, a flue in the center of the pile is provided. The 
stickers, usually 1 inch thick and iy 2 inches wide, are placed 4 feet 
apart. In the case of thick stock the spacing between the stickers 
may be increased. Where the boards warp, as in the middle of the 
pile shown in Figure 5, closer spacing must be used, and greater 
care must be exercised in the other steps of piling. 
No schedule for drying alder satisfactorily in the shortest length 
of time has ever been worked out. Manufacturers seem to rely 
entirely on the judgment of the kiln operators, with the result that 
schedules used differ widely. 
Green 1-inch stock is dried to a moisture content of 12 to 7 per 
cent in from five to nine days. The initial temperatures used at dif- 
ferent plants vary from 120 to 170° F., with the final temperatures 
ranging from 160 to 200° F. All operators are agreed that a high 
humidity, averaging from 60 to 80 per cent, must be maintained 
throughout the drying. Both green and partially air-seasoned stock 
is steamed at the beginning of the run, also during drying if the 
condition of stock demands. 
