50 BULLETIN 1136, U. S. DEPARTMENT OF AGRICULTURE 
TABLE 3.—Index of general kiln-drying schedules jor various hardwood species, 
to use with lumber up to six quarter inches in thickness 
Hard- Hard- 
Species of wood wear Remarks Species of wood Reet Remarks 
ule ule 
PANS Ts ae EN EE RANE 2 Mahogany--_-__ -___-- 4 
IBasswoods ahi a auian 1 Maple, silver and 
I BX SLE) 04 ips ie ee HN 3 sugar. ! 3 
Bin eer AM) We 1 Oak, red and white__ 6 | Northern highland 
Boxwood___--------_- 5 | Squares or quartered stock. 
stock only. 1B (oye eee BEN ey 7 | Northern lowland 
BUtLELnU ee ae 2 stock. 
@herry; black) 2223222 5 AVON es Goan 7 | Southern highland 
Chestnuiae ssa 2) stock. 
Cottonwood_-________- 2 ADO Ake Nie 8 | Southern lowland 
ED Danka ae Ue Se EE 2 stock. 
Gumired eas eauiGis 2 | See special schedule || Osage orange________- 5 
for sap gum. Persimmon_________-- 5 
Gum, black and tu- 3 Poplar, yellow_____-_-- 1 
pelo. Sycamores seuss ae 5 
ackbernye ee 2 Teak (girdled) -_____- 2 | Burmese: For Java, 
ENTE KORY Ae RE 5 nese teak use next 
EO ivan Ue 4 milder schedule. 
Hop hornbeam (iron- 4 Teak (ungirdled) _____ 3 
woo Walnut, black______-_- 5 
WOCUS Gav RL eS 5 Wallowa Bhasin 2 
IME Yea oo WEY ee 4 
Red gum.—The hardwoods, as a rule, are more plastic when hot 
and moist than the conifers are, and, in consequence, are more easily 
bent. A modification of this fact is taken advantage of in the dry- 
ing of red gum, which at high temperatures seems plastic enough 
to overcome its natural tendency to warp, and dries with no great 
trouble if properly stickered (p. 79). 
GENERAL SOFTWOOD SCHEDULES 
Although the basic principles in the construction and the use of 
both hardwood and softwood schedules are identical, a slight dif- 
ference in the arrangement of the two kinds seems necessary. Be- 
cause of large variations in the initial or “ green ” moisture content 
existing among the several softwoods, each of the general softwood 
schedules is presented in Table 4 in several divisions; the divisions 
of the same schedule differ from one another only in the values of 
moisture content at which the changes in temperature and in humid- 
ity are to be made. 
Further, because of quite wide differences in the drying require- 
ments of various grades and sizes of lumber even in a single species 
of softwood, it has been found desirable, in several instances, to 
make drying recomemndations for individual grades or for special 
sizes, and a number of special schedules have been developed to cover 
unusual needs. In addition, the type of kiln has an important bear- 
ing on the matter. The initial entering-air humidity of 70 per cent, 
given in the softwood schedules, can be maintained only under favor- 
able conditions. With fast-drying woods the humidity of the air 
increases rapidly in its passage through the lumber, and, unless the 
circulation is brisk, air entering the lumber at 70 per cent humidity 
may become almost or quite saturated before it leaves the pile. This 
