This is usually expressed in pounds per thousand board feet, a board foot being considered as one-twelfth of a cubic foot.
Wood shrinks greatly in drying from the green to the oven-dry condition.

(See Table XIV.) Consequently a block of wood measuring a cubic foot when green will measure considerably less when oven-dry.

It follows that the density of oven-dry wood does not represent the weight of the dry wood substance in a cubic foot of green wood.

In other words, it is not the weight of a cubic foot of green wood minus the weight of the water which it contains.

Since the latter is often a more convenient figure to use and much easier to obtain than the weight of oven-dry wood, it is commonly expressed in tables of "specific gravity or density of dry wood." |----------------------------------------------------------------------------| | TABLE XIV | |----------------------------------------------------------------------------| | SPECIFIC GRAVITY, AND SHRINKAGE OF 51 AMERICAN WOODS | | (Forest Service Cir.