Upgrading of wood by application of an oil-heat treatment

The upgrading of spruce (Picea abies L. Karst.) and Scots pine (Pinus sylve stris L.) timber by application of a heat treatment was carried out in an o il-bath at temperatures between 180 degrees C and 220 degrees C without pre ssure and oxygen to improve the resistance against fungi and the dimensiona l stability. In comparison, wood specimens were exposed to the same tempera tures in air atmosphere. The treatment of both wood species resulted in a b etter resistance against Coniophora puteana compared to specimens treated a t the same temperatures in air atmosphere. Resins from the wood were distri buted evenly by the oil-bath surrounding the specimens, resulting in a unif ormly coloured surface compared to wood treated in air atmosphere. In order to achieve the desired upgrading effect, certain changes of mechanical pro perties and colour, however, have to be accepted, but they were less seriou s compared to specimens treated in air atmosphere. In general, the combinat ion of a heat treatment in an oil bath seems to be a promising approach to upgrade wood for outdoor end-uses. Since the oils applied originate from pl ants this method of upgrading wood seems to be satisfying concerning ecolog ical aspects.