European Journal of Wood and Wood Products

, Volume 69, Issue 2, pp 239–246 | Cite as

The influence of material properties on the amount of twist of spruce wood during kiln drying

  • A. StražeEmail author
  • R. Kliger
  • M. Johansson
  • Ž. Gorišek
Originals Originalarbeiten


The development of twist in Norway spruce boards (Picea abies Karst.) during normal temperature kiln drying was researched. Tangentially oriented boards were sawn from diametrical radial planks, from which the basic wood properties, i.e. linear shrinkage and grain angle, were determined. The unrestrained boards were kiln dried using a selected drying schedule. During the controlled drying process the moisture content (MC) and twist of the boards were measured. Twist was generally induced by the shrinkage of wood below the fibre saturation point, and increased in proportional to the decrease in MC. The earlier appearance of twist, with regard to MC and drying time, was confirmed in the case of boards sawn from the central part of logs. The final twist amounted to between 10 and 20°/m in the case of boards close to the pith, and decreased to less than 4°/m in the case of boards sawn at a radius of 70 mm from the centre of the logs. Ring curvature had the highest impact on the final twist of the dried boards, followed by grain angle and tangential shrinkage.


Moisture Content Wood Density Radial Position Ring Curvature Juvenile Wood 
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Einfluss der Materialeigenschaften auf die Verdrehungen von Fichtenholz bei der technischen Trocknung


Untersucht wurde die Entwicklung der Verdrehung von Fichtenholz während der technischen Trocknung unter üblichen Temperaturen. Kernbohlen wurden in Bretter mit tangentialem Jahrringverlauf aufgetrennt und deren Eigenschaften, d. h. lineares Schwindmaß und Faserabweichung, wurden bestimmt. Die Proben wurden unbehindert gelagert und mit einem ausgewählten Trocknungsprogramm getrocknet. Während des Trocknungsverlaufes wurden die Holzfeuchte (MC) und die Verdrehung der Bretter gemessen. Die Verdrehung wurde im Allgemeinen durch Schwinden des Holzes unterhalb Fasersättigung verursacht und sie nahm mit abnehmender Holzfeuchte proportional zu. Die Bretter aus dem marknahen Bereich verdrehten sich früher, d. h. bei hoher Holzfeuchte und kürzerer Trocknungszeit. Am Ende betrug die Verdrehung bei marknahen Brettern 10–20°/m, während Bretter mit einem Markabstand von 70 mm nur eine Verdrehung von 4°/m aufwiesen. Den größten Einfluss auf die endgültige Verdrehung der getrockneten Bretter hatte der vom Markabstand abhängige Jahrringverlauf gefolgt von der Faserabweichung und dem tangentialen Schwindmaß.


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • A. Straže
    • 1
    Email author
  • R. Kliger
    • 2
  • M. Johansson
    • 3
  • Ž. Gorišek
    • 1
  1. 1.Biotechnical Faculty, Department of Wood Science and TechnologyUniversity of LjubljanaLjubljanaSlovenia
  2. 2.Department of Structural Engineering, Steel and Timber StructuresChalmers University of TechnologyGöteborgSweden
  3. 3.School of EngineeringLinnaeus UniversityVaxjoSweden

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