=Weighing.=--Set the base of the scale on a level surface and accurately balance the scale beam. Put the test pieces on the scale pan and note their weight on the lower edge of the beam. Set the indicator point on the horizontal bar at a number corresponding to this weight, which may be found on the cylinder at the top of the table.
Dry the test pieces on the Electric Heater (Fig. 101) 30 to 40 minutes, or on the engine cylinder two or three hours. Weigh them at once and note the weight. Then turn the cylinder up and at the left of it under the small pointer find the number corresponding to this weight. The percentage of moisture lost is found directly under pointer on the horizontal bar first mentioned. The lower portion on the cylinder Table No. II is an extension of the upper portion, and is manipulated in the same manner except that the bottom line of figures is used for the first weight, and the right side of cylinder for second weight. Turn the cylinder down instead of up when using it.
Examples (Test Pieces)
MODEL A. Table No. II, Kiln-dried or Air-dried Lumber:
If first weight is 90-1/2 and the second weight is 87, the cylinder table will show the board from which the test pieces were taken had a moisture content of 3.8 per cent.
MODEL B. Tables No. II and III, Air-dried (also Green and Kiln-dried) Lumber.
If the first weight on lower cylinder is 97 and the second weight is 76, the table will show 21.6 per cent of moisture.
MODEL C. Table III, Green Lumber:
If the first weight is 94 and the second weight is 51, the table shows 45.8 per cent of moisture.
Keep Records of the Moisture Content
=Saw Mills.=--Should test and mark each pile of lumber when first piled in the yard, and later when sold it should be again tested and the two records given to the purchaser.
=Factories.=--Should test and mark the lumber when first received, and if piled in the yard to be kiln-dried later, it should be tested before going into the dry kiln, and again before being removed, and these records placed on file for future reference.
Kiln-dried lumber piled in storage rooms (without any heat) will absorb 7 to 9 per cent of moisture, and even when so stored should be tested for moisture before being manufactured into the finished product.
Never work lumber through the factory that has more than 5 or 6 per cent of moisture or less than 3 per cent.
Dry storage rooms should be provided with heating coils and properly ventilated.
Oak or any other species of wood that shows 25 or 30 per cent of moisture when going into the dry kiln, will take longer to dry than it would if it contained 15 to 20 per cent, therefore the importance of testing before putting into the kiln as well as when taking it out.
The Electric Heater
In Figure 101 is shown the Electric Heater. This heater is especially designed to dry quickly the test pieces for use in connection with the Scalometer (see Fig. 100) without charring them. It may be attached to any electric light socket of 110 volts direct or alternating current.
A metal rack is provided to hold the test pieces vertically on edge.
[Ill.u.s.tration: Fig. 101. The Electric Heater.]
Turn the test pieces over once or twice while drying.
It will require from 20 minutes to one hour to remove all the moisture from the test pieces when placed on this heater, depending on whether they are cut from green, air-dried, or kiln-dried boards.
Test pieces cut from softwoods will dry quicker than those cut from hardwoods.
When the test pieces fail to show any further loss in weight, they are then free from all moisture content.
BIBLIOGRAPHY
AMERICAN BLOWER COMPANY, Detroit, Mich.
IMRE, JAMES E., "The Kiln-drying of Gum," The United States Dept. of Agriculture, Division of Forestry.
NATIONAL DRY KILN COMPANY, Indianapolis, Ind.
PRICHARD, REUBEN P., "The Structure of the Common Woods,"
The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 3.
ROTH, FILIBERT, "Timber," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 10.
STANDARD DRY KILN COMPANY, Indianapolis, Ind.
STURTEVANT COMPANY, B. F., Boston, Ma.s.s.
TIEMAN, H. D., "The Effects of Moisture upon the Strength and Stiffness of Wood," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 70.
TIEMAN, H. D., "Principles of Kiln-drying Lumber," The United States Dept. of Agriculture, Division of Forestry.
TIEMAN, H. D., "The Theory of Drying and its Application, etc.,"
The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 509.
THE UNITED STATES DEPT. OF AGRICULTURE, DIVISION OF FORESTRY, "Check List of the Forest Trees of the United States."
THE UNITED STATES DEPT. OF AGRICULTURE, DIVISION OF FORESTRY, Bulletin No. 37.
VON SCHRENK, HERMAN, "Seasoning of Timbers," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 41.
WAGNER, J. B., "Cooperage," 1910.
GLOSSARY
=Abnormal.= Differing from the usual structure.
=Ac.u.minate.= Tapering at the end.
=Adhesion.= The union of members of different floral whorls.
=Air-seasoning.= The drying of wood in the open air.