his steaming is usually conducted at atmospheric pressure and
frequently condensed steam is used at temperatures far below 212
degrees Fahrenheit. In a humidity-regulated kiln this preliminary
treatment may be omitted, since nearly saturated conditions can be
maintained and graduated as the drying progresses.

Recently the process of steaming at pressures up to 20 pounds gauge in
a cylinder for short periods of time, varying from 5 to 20 minutes, is
being advocated in the United States. The truck load is run into the
cylinder, steamed, and then taken directly out into the air. It may
subsequently be placed in the dry kiln if further drying is desired.
The self-contained heat of the wood evaporates considerable moisture,
and the sudden drying of the boards causes the shrinkage to be reduced
slightly in some cases. Such short periods of steaming under 20 pounds
pressure do not appear to injure the wood mechanically, although they
do darken the color appreciably, especially of the sapwood of the
species having a light-colored sap, as black walnut (_Juglans nigra_)
and red gum (_Liquidamber styraciflua_). Longer periods of steaming
have been found to weaken the wood. There is a great difference in the
effect on different species, however.

Soaking wood for a long time before drying has been practised, but
experiments indicate that no particularly beneficial results, from the
drying standpoint, are attained thereby. In fact, in some species
containing sugars and allied substances it is probably detrimental
from the shrinkage standpoint. If soaked in boiling water some species
shrink and warp more than if dried without this treatment.

In general, it may be said that, except possibly for short-period
steaming as described above, steaming and soaking hardwoods at
temperatures of 212 degrees Fahrenheit or over should be avoided if
possible.

It is the old saying that wood put into water shortly after it is
felled, and left in water for a year or more, will be perfectly
seasoned after a short subsequent exposure to the air. For this reason
rivermen maintain that timber is made better by rafting. Herzenstein
says: "Floating the timber down rivers helps to wash out the sap, and
hence must be considered as favorable to its preservation, the more so
as it enables it to absorb more preservative."

Wood which has been buried in swamps is eagerly sought after by
carpenters and joiners, because it has lost all tendency to warp and