Solvent Seasoning of Tanoak

Freshly sawed 4/4 green random width Lithocarpus densiflorus Rehd. lumber was dried in less than 30 hours by the solvent seasoning method. The investigation was conducted in the laboratory using a stainless steel pilot unit with a capacity of 200 board feet of 6-foot lumber. Preliminary runs showed that the drying rate for tanoak heartwood was much slower than for sapwood. Therefore, the stock was segregated before the seasoning tests. All runs in the study were confined to 4/4 sapwood. Twelve boards were selected for each run, and samples were taken for moisture content. Each board was weighed to obtain the total green weight. The boards were packaged into two 6-board units and the two units placed in a vertical position in the rack of the extractor. The loaded rack contained from 40 to 60 board feet of lumber. The extractor was secured after loading and 60 gallons of acetone were pumped into the bottom of the chamber. The solvent was heated and circulated by a heater and pump. By recording the amount of water removed, the average moisture content of the lumber charge at any time was readily determined. By means of heat and a blower, followed by saturated steam, the solvent picked up by the lumber was removed, condensed, and recovered. After the solvent-removal cycle was completed, the boards were weighed and the moisture content determined. Marked effect was found of board position on the extraction rate to the 10 percent level. Boards placed in a vertical position and sprayed with the solvent required 24 hours for drying. Boards placed in a vertical position but immersed in the solvent required 55 hours. Boards placed in a horizontal position and immersed in the solvent required 160 hours. The effect of solvent temperature on the extraction rate was also noticeable. At 100?F the time required was 66 hours; at 115?F, 52 hours; and, at 130?F only 22 hours. These results were obtained using the vertical position, solvent-sprayed method. The tanoak lumber from nearly all the runs was relatively free of seasoning defects and stresses. This would indicate that water removal is accomplished by means of direct extraction through the thickness and length of the board, which would tend to minimize stresses.

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