Sink-Float Test to Determine Treatability of Douglas-Fir

To conduct the sink-float test, a plug 1/2 inch in diameter by 1/2 inch long is cut from the heartwood of each piece of lumber to be tested. The plugs are dried to constant weight either at room temperature or in an oven at 220?F, then submerged in oil or water under a vacuum of 20 inches of mercury for 6 minutes, and vented slowly to atmospheric pressure. Pieces that sink in 1 minute after the vacuum is broken are classed as permeable. The remaining plugs are then submerged again under vacuum for 20 minutes before venting to atmospheric pressure. Plugs that remain floating 1 minute after venting are classed as largely refractory. The plugs that sink after this second vacuum are classed as intermediate in treatability.

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