This
treatment also furnishes a means of heating the lumber very rapidly.
It is probably a good way to stop the sap-staining of green lumber, if
it is steamed while green. We have not investigated the other effects
of steaming green gum, however, so we hesitate to recommend it.

Temperatures as high as 210 degrees Fahrenheit were used with no
apparent harm to the material. The best result was obtained with the
temperature of 180 degrees Fahrenheit, after the first preliminary
heating in steam to 200 degrees Fahrenheit. Higher temperatures may be
used with air-dried gum, however.

The best method of humidity control proved to be to reduce the
relative humidity of the air from 100 per cent (saturated steam) very
carefully at first and then more rapidly to 30 per cent in about four
days. If the change is too marked immediately after the steaming
period, checking will invariably result. Under these temperature and
humidity conditions the stock was dried from 15 per cent moisture,
based on the dry wood weight, to 6 per cent in five days' time. The
loss due to checking was about 5 per cent, based on the actual footage
loss, not on commercial grades.

=Final Steaming.=--From time to time during the test runs the material
was resawed to test for case-hardening. The stock dried in five days
showed slight case-hardening, so it was steamed at atmospheric
pressure for 36 minutes near the close of the run, with the result
that when dried off again the stresses were no longer present. The
material from one run was steamed for three hours at atmospheric
pressure and proved very badly case-hardened, but in the reverse
direction. It seems possible that by testing for the amount of
case-hardening one might select a final steaming period which would
eliminate all stresses in the wood.

Kiln-drying of Green Red Gum

The following article was published by the United States Forestry
Service on the kiln-drying of green red gum:

A short time ago fifteen fine, red-gum logs 16 feet long were received
from Sardis, Miss. They were in excellent condition and quite green.

It has been our belief that if the gum could be kiln-dried directly
from the saw, a number of the difficulties in seasoning might be
avoided. Therefore, we have undertaken to find out whether or not such
a thing is feasible. The green logs now at the laboratory are to be
used in this investigation. One run of a preliminary nature has just
been made