Abstract
During drying, the low-molecular weight (LMW) sugars and nitrogenous compounds are redistributed and accumulated at the lumber surface. These soluble substances may migrate into coatings and cause discolouration. The aim of the present study was to determine the susceptibility to discolouration of white coatings, applied on kiln- and air-dried lumber surfaces with different content of LMW sugars and nitrogen.
The differences in the discolouration were more distinct between the coatings than between the drying treatments. Planing had no significant effect on the discolouration, which proved that the different content of soluble substances at the original and planed surfaces did not induce significantly different discolouration. The type of drying and the actual contents of soluble substances at the surface, played a minor role in the discolouration process. The discolouration of all five coatings can be characterized as “fading”, due to decreased colour saturation and lightness.
Zusammenfassung
Während des Trocknens werden niedermolekulare Zucker und stickstoffhaltige Verbindungen zur Holzoberfläche transportiert, wo sie sich anreichern. Diese löslichen Substanzen können auch in die Deckanstriche eindiffundieren und dort Verfärbungen verursachen. In der vorliegenden Arbeit wurden weiße Deckanstriche hinsichtlich ihrer Anfälligkeit für Verfärbungen untersucht. Die Farbschichten waren auf luftgetrocknetes und ofengetrocknetes Schnitholz aufgebracht, die unterschiedliche Gehalte an löslichen Zuckern und Stickstoff aufwiesen. Unterschiede in den Verfärbungen waren zwischen den einzelnen Anstrichen auspgeprägter als zwischen den Trocknungsvarianten. Hobeln hatte keinen signifikanten Einfluß auf das Ausmaß der Verfärbungen. Die Art der Trocknung und der gemessene Gehalt an löslichen Substanzen spielt nur eine geringe Rolle. Die Verfärbung an den fünf untersuchten Deckanstrichen kann charakterisiert, werden als “Verblassen”, d.h. einen Verlust an Farbsättigung und Helligkeit.
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Terziev, N., Ekstedt, J. Discolouration of white coatings applied on kiln- and air-dried scots pine lumber. Holz als Roh-und Werkstoff 55, 77–81 (1997). https://doi.org/10.1007/BF02990521
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DOI: https://doi.org/10.1007/BF02990521