Abstract: A device for pressure treatment of wood elements comprises a pressure chamber for accommodating the wood elements which are to be treated. The pressure chamber also accommodates a pressure medium which surrounds the wood elements on more than one side and, at least before the pressurization, a secondary medium in the form of a fluid. When the pressure medium is pressurized, the wood elements are subjected to a multilateral pressure, whereby they are permanently compressed. Furthermore, the pressure chamber is provided with elements for controlling the quantity of secondary medium which penetrates into the wood during the treatment. These elements may include evacuating valves or casings which surround the wood elements and which are impenetrable to the secondary medium.

Abstract: The pressure medium used in the pressure chamber of a hydrostatic press is degassified in a degassing tank prior to delivery to the pressure chamber so as to improve the resistance of the pressure cylinder, or the liner inside of the pressure cylinder, to fatigue. The degassified pressure medium can be a mixture of recirculated pressure medium recovered after passage through the die extrusion hole and new pressure medium, such as castor oil.