Drying at Atmospheric Pressure
Present practice of kiln-drying varies tremendously and there is no uniformity or standard method.
Temperatures vary anywhere from 65 to 165 degrees Fahrenheit, or even higher, and inch boards three to six months on the sticks are being dried in from four days to three weeks, and three-inch material in from two to five months.
All methods in use at atmospheric pressure may be classified under the following headings. The kilns may be either progressive or compartment, and preliminary steaming may or may not be used with any one of these methods:
- 1. Dry air heated. This is generally obsolete.
- 2. Moist air.
- a. Ventilated.
- b. Forced draft.
- c. Condensing.
- d. Humidity regulated.
- e. Boiling.
- 3. Superheated steam.