Problems in Drying Chilean Coigue

Three mature coigue (Nathofagus dombeyi) were sampled and allotted to nine experimental runs of twenty-four 4- by 1-inch boards of 3-foot, 6-inch length, half of them quartered and other half flat-sawn. The two slowest kiln schedules were started at 105?F to 110?F dry bulb temperature and maintained below 125?F until moisture content fell below 30 percent. The 20-day run was given 140?F when the wood reached 60 percent MC, the 9-day run was set at 140?F from the start. Final temperature ranged from 120? to 180?F and wet-bulb depression increased from 4? to 11?F initially to 10? to 30?F at the end. Schedules from the air-dry condition ranged from 120?F dry bulb and 11? to 30?F depression initially to 140?to 170?F and 18? to 45?F at the conclusion. After drying the boards were conditioned to 15 percent MC and given a reconditioning treatment in saturated steam at 212?F for 4 hours and redried to 12 percent to determine final shrinkage. Experimental results indicated little difference in quality or shrinkage between different schedules, but differences were significant between air-dried and kiln-dried material. The drying method had no influence below 20 percent MC. Test results showed tangential shrinkages were 11.4 percent in butt logs and 9.8 percent in top logs; collapse in thickness was greater in the width of boards, the flat-sawn boards shrunk 8.0 percent in width, 9.1 percent in thickness; quartered boards shrunk 5.8 percent in width and 13.3 percent in thickness. For best quality air-drying to 20 to 25 percent with subsequent kiln-drying is recommended.

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