Cell-Wall Density of Douglas-Fir by Two Optometric Methods

The change in cell-wall density from the water-swollen (1.0 g/cm3) to the oven-dry (1.43 g/cm3) condition is a function of the percent of shrinkage in the cell wall. Cell-wall density obtained opto-metrically by the Dual-Linear measuring micrometer and the dot-grid eyepiece compared favorably with densities reported for mercury porisimeter or picnometric techniques. Both optometric techniques are nondestructive and offer advantages over destructive techniques. Void volumes in the dry cell wall were calculated to be approximately 3.5%, fiber saturation point for extractive-free cell wall about 35%, Average interfibrillar spacing in the water-swollen condition was 20 Å for both earlywood and latewood and in the dry wall: spacing was 4.7 Å for earlywood and 8.3 Å for latewood