24 BULLETIN 1436, U. S. DEPARTMENT OF AGRICULTURE 
The actual process of kiln-drying should start with a high humid- 
ity and low temperature, and should end with a lower humidity 
and a higher temperature. Steam should be admitted at the be- 
ginning of the run to heat the blocks through and to moisten them 
to some degree so that the moisture in the interior of the blocks will 
move to the surface more rapidly and more easily. Steam may also 
be necessary during the run to reestablish within the blocks the 
uniform flow of moisture which may be broken in the process of 
drying by the tendency of the blocks to caseharden. Adequate 
circulation through the spaces between the blocks and away from the 
blocks is at all times necessary. The now of air within the kiln 
should be studied during a run by tracer currents of smoke. 
In order to understand what is taking place within the blocks 
themselves as the drying proceeds, tests for casehardening and 
checking should be made by sawing open the blocks used for test 
samples. Test should be made periodically to determine the moisture 
content of the blocks. 
The five steps necessary to make a moisture determination are : 
1. Cut a sample from the center of the material. 
2. Immediately after sawing, remove all loose splinters and weigh 
the sample. 
3. Put the sample in an oven maintained at a temperature of 212° 
!F., until constant weight is attained. 
4. Reweigh the sample to obtain the oven-dry weight. 
5. Divide the loss in weight by the oven-dry weight and multiply 
the result by 100 to get the percentage of moisture in the original 
sample. 
(W — D) 
Percentage of moisture = ^ X 100 
Where 
W=Original weight as found under 2 above. 
D =Oven-dry weight as found under 4 above. 
Another method used for determining the amount of moisture 
in chips requires little equipment and only 7 to 10 minutes time. 
A specified weight of wood chips taken from shuttle blocks, 
usually 100 grams, is immersed in kerosene in a flask or retort and 
the mixture is heated. The water in the chips changes to steam 
at 212° F., and goes out through a glass tube in the cork of the 
flask, is condensed by a water jacket surrounding the tube, and 
caught in a measuring glass. The boiling point of kerosene being 
higher than that of water, all the moisture will be driven off the 
chips before the oil vaporizes to any great extent. The oil that 
does go off in the form of vapor is condensed and caught in the 
same graduate with the water. When the evaporation of moisture 
is complete the oil and water are allowed to remain a few minutes 
until the water has all settled to the bottom of the graduate. The 
amount of moisture in the wood chips is then found by a direct 
reading. 
This method has been checked for accuracy with that of weighing 
samples before and after oven-drying, and the variation found to be 
less than 1 per cent. 
One of the big weaknesses in kiln-drying at shuttle factories is 
an inadequate and irregular supply of steam for heating the dry 
kilns. In some factories the steam pressure at night is not main- 
tained, and the continuity of drying is consequently broken. The 
