A New Method for Long Term Preservation of Wood By Chemical Modification

The process which is the subject of this paper is based on the use of copper formate. When the reaction between copper formate and wood is complete, the copper is believed to be involved in a cross-linking between adjacent cellulose molecules. The resulting product should be virtually permanently fixed in the wood. A maximum of 0.8 percent copper based on OD weight of treated wood is sufficient for prolonged protection. In this process, wood is subjected to a vacuum with dilute aqueous copper formate sucked into the treating vessel. Then the pressure is applied. The solution is drawn off and the impregnated wood is autoclaved or otherwise heated to bind the copper with the cellulose. Six panels treated with this process were immersed in the ocean at Miami Beach along with 60 panels treated with creosote (retention 5-20 pounds per cu. ft.) and two untreated control panels. The controls were destroyed in four months; the creosoted panels were heavily damaged in 18 months, while the copper formate treated panels after 2-1/2 years of immersion showed insignificant damage by marine borers. Further tests showed that resistance to terrestrial agents of copper formate treated wood was also excellent. Generally, long term protection for wood well in excess of 20 years can be achieved even under extreme conditions of exposure.

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