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 901⁄2 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.