Effect of negative factors on the use of oak and beech for decorative veneers

The paper summarizes results of an institutional research aimed at the analysis of relationships between the quality of decorative veneers of oak and beech and negative factors decreasing the use of veneers. Effects of factors were assessed in the preparation, storage and protection of a raw material, treatment of logs before slicing and stay-log cutting and in the manufacture of veneers proper. Intensity of spraying was measured, protection of raw material during storage and regimes of hydrothermic preparation were assessed. Qualitative yield was determined in 386 logs of a diameter from 34 to 66 cm comparing four methods of cutting: half-round cutting and two-sized slicing with half-round cuttingand stay-log cutting of ahalf-round log and a whole log. The quality of veneers is also affected by the relative position and quality of cutting tools. Results of the paper consist in conclusions and recommendations for the better and more complete use of oak and beech to obtain quality veneers. The paper sets conditions for storage and protection, raw material preparation and regimes of hydrothermic treatment. Based on the research results we recommend to cut logs of oak of 30 to 40 cm diameter from two opposite sides (two-sided slicing) with the subsequent cutting into two parts. Each of the parts is sliced separately to a residual board. It is suitable logs of oak of 40 to 66 cm diameter to be lengthwise trimmed from two or four faces and then cut into two parts. It is recommended logs of beech of 30 to 44 cm diameter to be stay-log cut without lengthwise division in the whole log and logs over 44 cm diameter to be stay-log cut when divided into two parts. The necessary precondition of a quality veneer with a smooth surface and uniform thickness is keeping the geometry of cutting tools. It is necessary to check regularly determined parameters of a knife and nose bar in relation to a bolt. The nose bar and knife have to be made from a suitable material not causing colouring.