TABLE XIV
SPECIFIC GRAVITY, AND SHRINKAGE OF 51 AMERICAN WOODS
(Forest Service Cir. 213)
COMMON NAME OF SPECIES Moisture content Specific gravity oven-dry, based on Shrinkage from green to oven-dry condition
Volume when green Volume when oven-dry In volume Radial Tangential
Per cent

Per cent Per cent Per cent
Hardwoods





Ash, black 77 0.466



white 38 .550 0.640 12.6 4.3 6.4
" 47 .516 .590 11.7

Basswood 110 .315 .374 14.5 6.2 8.4
Beech 61 .556 .669 16.5 4.6 10.5
Birch, yellow 72 .545 .661 17.0 7.9 9.0
Elm, rock 46 .578



slippery 57 .541 .639 15.5 5.1 9.9
white 66 .430



Gum, red 71 .434



Hackberry 50 .504 .576 14.0 4.2 8.9
Hickory, big shellbark 64 .601
17.6 7.4 11.2
" 55 .666
20.9 7.9 14.2
bitternut 65 .624



mockernut 64 .606
16.5 6.9 10.4
" 57 .662
18.9 8.4 11.4
" 48 .666



nutmeg 76 .558



pignut 59 .627
15.0 5.6 9.8
" 54 .667
15.3 6.3 9.5
" 55 .667
16.9 6.8 10.9
" 52 .667
21.2 8.5 13.8
shagbark 65 .608
16.0 6.5 10.2
" 58 .646
18.4 7.9 11.4
" 64 .617



" 60 .653
15.5 6.5 9.7
water 74 .630



Locust, honey 53 .695 .759 8.6

Maple, red 69 .512



sugar 57 .546 .643 14.3 4.9 9.1
" 56 .577



Oak, post 64 .590 .732 16.0 5.7 10.6
red 80 .568 .660 13.1 3.7 8.3
swamp white 74 .637 .792 17.7 5.5 10.6
tanbark 88 .585



white 58 .594 .704 15.8 6.2 8.3
" 62 .603 .696 14.3 4.9 9.0
" 78 .600 .708 16.0 4.8 9.2
yellow 77 .573 .669 14.2 4.5 9.7
" 80 .550



Osage orange 31 .761 .838 8.9

Sycamore 81 .454 .526 13.5 5.0 7.3
Tupelo 121 .475 .545 12.4 4.4 7.9
TABLE XIV (CONT.)
SPECIFIC GRAVITY, AND SHRINKAGE OF 51 AMERICAN WOODS
(Forest Service Cir. 213)
COMMON NAME OF SPECIES Moisture content Specific gravity oven-dry, based on Shrinkage from green to oven-dry condition
Volume when green Volume when oven-dry In volume Radial Tangential
Per cent

Per cent Per cent Per cent
Conifers





Arborvitæ 55 .293 .315 7.0 2.1 4.9
Cedar, incense 80 .363



Cypress, bald 79 .452 .513 11.5 3.8 6.0
Fir, alpine 47 .306 .321 9.0 2.5 7.1
amabilis 117 .383



Douglas 32 .418 .458 10.9 3.7 6.6
white 156 .350 .437 10.2 3.4 7.0
Hemlock (east.) 129 .340 .394 9.2 2.3 5.0
Pine, lodgepole 44 .370 .415 11.3 4.2 7.1
lodgepole 58 .371 .407 10.1 3.6 5.9
longleaf 63 .528 .599 12.8 6.0 7.6
red or Nor 54 .440 .507 11.5 4.5 7.2
shortleaf 52 .447



sugar 123 .360 .386 8.4 2.9 5.6
west yellow 98 .353 .395 9.2 4.1 6.4
" 125 .377 .433 11.5 4.3 7.3
" 93 .391 .435 9.9 3.8 5.8
white 74 .363 .391 7.8 2.2 5.9
Redwood 81 .334



" 69 .366



Spruce, Engelmann 45 .325 .359 10.5 3.7 6.9
" 156 .299 .335 10.3 3.0 6.2
red 31 .396



white 41 .318



Tamarack 52 .491 .558 13.6 3.7 7.4

This weight divided by 62.43 gives the specific gravity per green volume. It is purely a fictitious quantity. To convert this figure into actual density or specific gravity of the dry wood, it is necessary to know the amount of shrinkage in volume. If S is the percentage of shrinkage from the green to the oven-dry condition, based on the green volume; D, the density of the dry wood per cubic foot while green; and d the actual density of oven-dry wood, then

D

----------=d.
1 - .0 S

This relation becomes clearer from the following analysis: Taking V and W as the volume and weight, respectively, when green, and v and w as the corresponding volume and weight when oven-dry, then,



w


W


V - v




V - v



d=--- ; D=---;S=-------×100, ands= -------×100,


v


V


V




v



in which S is the percentage of shrinkage from the green to the oven-dry condition, based on the green volume, and s the same based on the oven-dry volume.

In tables of specific gravity or density of wood it should always be stated whether the dry weight per unit of volume when green or the dry weight per unit of volume when dry is intended, since the shrinkage in volume may vary from 6 to 50 per cent, though in conifers it is usually about 10 per cent, and in hardwoods nearer 15 per cent. ([See Table XIV].)