Method for liquid treatment of a wood species

A method for treating a wood species with an active ingredient, the method comprising:

• providing the wood species in a container;
• applying pressure, in the container, by providing gaseous carbon dioxide to the container, said container comprising the wood species, at a temperature below the critical point of carbon dioxide to provide a compressed gas;
• further pressurizing the container to reach a prevailing pressure in the container and to provide condensed carbon dioxide;
• providing an active ingredient to the container comprising the wood species, wherein the active ingredient is applied simultaneous as the gaseous carbon dioxide is provided to the container, and wherein the active ingredient is selected from the group consisting of polymers for increasing water resistance, organic and inorganic biocides, aromas, colorants and organic and inorganic salts;
• maintaining the prevailing pressure for a first predetermined period of time while the active ingredient is in the container;
• increasing the temperature in the container to a temperature above the critical point of carbon dioxide at the prevailing pressure to provide carbon dioxide in supercritical form;
• maintaining the temperature in the container at a temperature at or above the critical point of carbon dioxide at the prevailing pressure for a second predetermined period of time, wherein the second period of time occurs after the first period of time;
• and
• thereafter, reducing the pressure in the container to atmospheric to complete the treatment of the wood species and to provide carbon dioxide in gaseous form, wherein the treatment of the wood species results in one or more of:
• the wood species being impregnated with the active ingredient, a compound being extracted from the wood species, the wood species being dyed, or the water resistance of the wood species being increased.