A New Procedure for Measuring Fiber Saturation Points

Twenty-mil-thick across sections of Sitka spruce, slash pine, balsa, and maple were cut from water-logged blocks with a microtome-type milling knife. Microscopical examination showed that the cell walls were not damaged by this cutting. Some of the blocks were in the original green condition; others were water-logged from the air-dry condition. The cross sections were extracted with water, then immersed in a large excess of 3-percent PEG-9000, and agitated at room temperature for 2 days. Following this, an aliquot of the external solution was removed for analysis for PEG-9000. The cross sections were removed and analyzed as described in another, paper referenced here. The fiber saturation point of never-dried wood is slightly higher than that of the once-dried material. The fiber saturation points of different species are roughly independent of bulk density provided the density is greater than about 0.35 gram per cubic centimeter. For species of lower density, the fiber saturation point increases with decreasing density. The fiber saturation point of balsa with a density of 0.25 gram per cubic centimeter is 52 percent.

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