Macroscopic and Microscopic Analyses of Color Changes of Wood Pressure Steam-Dried Above Atmospheric Pressure
Keywords:Drying, steam, yellow poplar, silver maple, red oak, white oak, southern pine, extractives
AbstractYellow 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.
Hillis, W. E. 1971. Distribution, properties and formation of some wood extractives. Wood Sci. Technol.5:272-289.nKeith, C. T., and C. I. Chang. 1978. Properties of heat-darkened wood. 1. Hygroscopic properties. Report No. OPX 213E, Eastern For. Prod. Lab., Ottawa, Ontario, Canada. 20 pp.nMcGinnes, E. A., Jr., and P. K. Melcarek. 1976. Equipment for studying the color characteristics of wood at the cellular level. Wood Sci.9(1):46-50.nMcMillen, J. W., and E. M. Wengert. 1978. Drying eastern hardwoods. U.S. Dep. Agric., Agric. Handb. No. 528, p. 56.nNelson, N. D., R. R. Meaglin, and H. E. Wahlgren. 1969. Relationships of black walnut wood color to soil properties and site. Wood Fiber1(1):29-37.nPanshin, A. J., and C. de Zeeuw. 1980. Textbook of wood technology. Structure, identification, uses, and properties of commercial woods of the United States. McGraw Hill Book Co., New York. 722 pp.nPhelps, J. E., and E. A. McGinnes, Jr. 1980. Color of black walnut—macroscopic and microscopic studies. Pages 169-192 in Proceedings of the Natural Variations of Wood Properties Working Party, IUFRO Conference, Division 5, Oxford, England.nRosen, H. N. 1981. Drying of lumber in superheated steam above atmospheric pressure. In Amer. Inst. Chem. Eng. Symp. Ser. 77(207):32-37.nRosen, H. N., R. E. Bodkin, and K. D. Gaddis. 1982. Pressure steam drying of lumber. For. Prod. J. (in press).nSchneider, A. 1973. Investigations on the convection drying of lumber at extremely high temperatures. Part II. Drying degrade, changes in sorption, colour, and strength of pine sapwood and beechwood at drying temperatures from 110 to 180°C. Holz Roh-Werkst.31:198-206.n
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.