80 
Ohio Biological Survey 
the washing out of certain soluble material that is in the cells of 
wood tissue. 
In testing the absorptive capacity of 69 different kinds of Ohio 
woods it was found that the soft woods absorbed the most water in 
proportion to the weight, and the hard woods the least. The average 
total absorption of 27 kinds of the softer and lighter woods was 94 
per cent of their original weight. The average total absorption of 
ten medium woods was 74 per cent of their original weight. Thirty- 
two hard or heavy woods absorbed 64 per cent of their original 
weight. 
Volume. —It is a well-known fact that dry wood when subjected 
to moisture increases in volume. In some cases it assumes a greater 
size than it had before it \vas seasoned. The expansion is unsteady 
or irregular in most cases. We might think that the woods which 
absorb the most moisture and dry most rapidly would expand and 
shrink to a greater degree than the woods that take up less moisture 
and lose it less rapidly. This is not the case. The soft lighter woods, 
such as willow, white pine, and basswood, expand less than the per¬ 
simmon, oak, and other hard woods. The average increase in volume 
for 69 seasoned woods, tested while each was saturated with moisture 
was 12^ per cent of the original volume. Where the shrinkage of 
wood is irregular the condition known as warping often follows. 
Shrinkage.—When wood loses is moisture, it usually shrinks 
more or less, and with this often follows warping and checking. 
Warping may be caused by irregular shrinkage. If a board dries 
more rapidly on one side than on the other, the shrinkage that follows 
causes the board to bend at the ends and sides. 
Checking depends largely upon the rapidity with which wood 
loses its moisture, and upon the variation in the wood tissue. Hard¬ 
woods are more liable to check than softwoods. Outdoor air drying, 
quarter sawing, steaming, followed by slow drying, painting or oiling 
are among the means used to prevent checking. 
Toughness. —The toughness of wood depends upon various fac¬ 
tors. Among the more important are weight, soundness, freedom 
from knots, soil where grown, rate of growth, and how stored and 
seasoned after cutting. Other things being equal the more rapid 
wood grows the tougher it is. This is why wagon makers and others 
like second growth ash, hickory, and oak. 
