Some Effects of Bacterial Action on Rotary-Cut Southern Pine Veneer

The U.S. Forest Products Laboratory observed differences in veneer quality from disks of southern pine depending upon the storage history of the pine disks. A study was carried out to determine the effect of storage in an environment favorable to bacteria development upon the cutting characteristics, microstructure, and physical properties. Small clear disks of southern pine were stored for 6 months in warm water to promote the development of bacteria. They were then rotary cut to veneer 1/2 inch in thickness, as were matched disks that had been stored at 35?F. Microscopical examination showed the sapwood in disks stored in warm water had been attacked by bacteria, removing the parenchyma in the rays and resin ducts. Wood from the disks stored in warm water was generally more permeable and absorptive to water in the longitudinal and radial directions than wood from the disks stored at 35?F. There was no evidence of a significant reduction in flexibility, toughness, or specific gravity as a result of the bacterial infection. The disks stored at 35?F. lost less water in cutting than the disks stored in warm water, further indicating the latter had higher permeability. Loads developed on the roller bar were significantly higher when cutting the disks stored at 35?F. These higher loads were reflected in thinner veneer, which was weaker in tension perpendicular to the grain than the veneer cut from disks stored in warm water. Roughness was generally similar for veneer cut from disks stored in warm water and from disks stored at 35?F.

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