Considerations on drying frozen spruce wood and effects upon its properties

The aricle presents the results of a research performed in order to establish whether drying lumber from frozen state (in winter) has repercussions upon its properties, compared to drying under the same conditions lumber parts originating from the same log and position within the log section but that were not frozen prior to drying. To this purpose, spruce (Picea abies L.) lumber specimens, 35mm and 55mm thick, cut from the same log, half frozen at-30 degrees C and half unfrozen, were dried under the same conditions in a climate chamber. Some mechanical properties (hardness, bending strength, and modulus elasticity in static bending), as well as workability (expressed by means of the absorbed power and specific resistance to cutting during milling), were determined The results revealed slight differences between the frozen and the unfrozen samples both during the drying process and afterwards. It was noticed that a significant amount of water was removed from wood during the very beginning of the heating phase (thawing). With regards to wood properties after drying, a slight lowering of the mechanical properties and better workability could be established for the initially frozen samples.