RED ALDER OF THE PACIFIC NORTHWEST 
13 
It takes from 14 to 28 days to kiln-dry green iy 2 to 2 inch stock. 
Stock of this thickness is being successfully dried to a moisture con- 
tent of 12 per cent in 11 days, with temperatures ranging from 
100 c F. at the beginning of drying to 160° F. at the close. A relative 
humidity of 60 to 70 per cent is maintained during the early part 
of the run, dropping to 25 or 30 per cent at the end. Where the 
drying is forced, through the use of high temperatures and low 
humidities, honeycombing is likely to result (especially with thick 
stock), as well as checking, splitting, warping, and cupping. 
Fig. 5.— ALDER LUMBER, END OF KILN-DRYING RUN 
The warping in the center section is due to the use of too few stickers, which should 
not he more than 4 feet apart 
Although the Forest Products Laboratory has worked out drying 
schedules for a number of woods, no schedule based on actual drying 
tests has thus far been developed for red alder. It would seem, how- 
ever, that schedules developed for basswood, yellow poplar, and 
cottonwood could be safely applied to the kiln-drying of alder. All 
are diffuse-porous woods, and there is a marked similarity in essen- 
tial physical characteristics, as is shown in Table 3. It will be noted 
that the comparative shrinkage of red alder, green to oven dried is 
less than that of basswood and cottonwood and more than that of 
yellow poplar. 
Table 3.- 
-Essential properties of red alder, yellow poplar, bassicood, and cotton- 
wood with reference to kiln drying 
Species 
Specific gravity based 
on oven-dry weight 
Weight per cubic foot 
Compara- 
tive shrink- 
Green 
wood 
Oven-dried 
wood 
Air dry 
Kiln dry 
to oven 
dry 
Red alder 
0.37 
.37 
.33 
.37 
0.43 
.42 
.40 
.43 
Pounds 
28 
28 
26 
29 
Pounds 
27 
27 
25 
28 
Per cent 
12.3 
Yellow poplar _ 
11.3 
Basswood 
15.8 
Cottonwood. 
13.8 
