Macroscopic and Microscopic Analyses of Color Changes of Wood Pressure Steam-Dried Above Atmospheric Pressure


  • E. Allen McGinnes
  • Howard N. Rosen


Drying, steam, yellow poplar, silver maple, red oak, white oak, southern pine, extractives


Yellow poplar, silver maple, red oak, and southern pine heartwood samples were evaluated for color changes occurring as a result of pressure steam-drying above atmospheric pressure. Luminance significantly decreased, purity increased, and dominant wavelength shifted toward the red zone of the spectrum for yellow poplar and silver maple. Luminance significantly decreased, while other color parameters did not significantly change, for red oak wood. Southern pine wood decreased in luminance and increased in purity. Extractives of all woods appeared to have "softened" upon pressure steam-drying and became migratory, moving from the ray tissue system to the surface through the vessel system for the hardwood species. Pressure steam-dried white oak exhibited a drastically modified tyloses system; tyloses were missing from numerous heartwood vessels and those remaining appeared torn or ruptured.


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