Evaluation and comparison of quality of beech wood ( Fagus sylvaticaL.) after vacuum drying and enhigh frequencyHF -drying

The main advantage of the drying of wooden material in vacuum and HF field is the short time of the procedure. For the material and its further use, the quality of the dried wood is however important. The final quality is in this case driven by two properties: moisture content gradients and internal stress resulting in casehardening of wood. Procedures for determination of moisture gradient as described in various standards do not differ significantly, but several quite different methods exist to determine the internal stresses (prong test, standard ENV 14464 (slicing method, EDG method) and Russian standard GOST 11603-73 (B.N. Ugolev's method). Comparison of result achieved by using these methods is difficult. - White comparing wood properties after vacuum drying and HF drying, it can be stated that the material dried in vacuum has lower moisture content gradient and smaller degree of casehardening. One of the main reasons might be the lower temperature and longer time of the drying in comparison to HF drying.