Summary
The influence of drying methods on the permeability of red pine and eastern hemlock sapwood was investigated. Permeability was found to be reduced by normal drying procedures to only a small percentage of the green permeability. The reduction was more severe at higher drying temperatures; less severe but still very large at -18° C. Pit aspiration was shown to be responsible for the reduction. Replacing the sap with surfactant solutions and organic liquids and evaporating them revealed that pit aspiration occurred with surfactant solutions having surface tension values of less than 20 dynes/cm and did not occur with organic liquids having surface tension values as high as 44 dynes/cm. It is suggested that a critical factor in pit aspiration is the adhesion of the torus to the pit border, and the failure of the organic liquids to cause pit aspiration is due to their inability to promote adhesion between the torus and pit border.
Zusammenfassung
Der Einfluß verschiedener Trocknungsverfahren auf die Durchlässigkeit des Splintholzes bei Kiefer und Eastern Hemlock wurde untersucht. Es zeigte sich, daß bei Anwendung üblicher Trocknungsverfahren die Durchlässigkeit gegenüber jener des frischen Holzes sehr deutlich vermindert war. Höhere Trocknungstemperaturen setzten die Durchlässigkeit weit stärker herab; bei -18° C war die Verminderung etwas weniger stark, jedoch noch immer beträchtlich. Als Ursache für die Durchlässigkeitsverminderung wurde der Tüpfelverschluß gefunden. Beim Austausch des Zellsaftes gegen oberflächenaktive Lösungen bzw. gegen organische Flüssigkeiten und bei nachfolgender Verdampfung derselben ergab sich, daß die oberflächenaktiven Lösungen mit Oberflächenspannungswerten von höchstens 20 dyn/cm einen Tüpfelverschluß erzeugten, die organischen Lösungen mit Oberflächenspannungswerten bis zu 44 dyn/cm jedoch nicht. Es wird postuliert, daß beim Tüpfelverschluß das Haften des Torus am Tüpfelrand das Kriterium bildet; die Unfähigkeit bestimmter organischer Lösungen, einen Tüpfelverschluß zu bilden, ist darin zu sehen, daß sie die Adhäsion zwischen dem Torus und dem Tüpfelrand nicht zu fördern vermögen.
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Comstock, G.L., Côté, W.A. Factors affecting permeability and pit aspiration in coniferous sapwood. Wood Science and Technology 2, 279–291 (1968). https://doi.org/10.1007/BF00350274
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DOI: https://doi.org/10.1007/BF00350274