Treatment of European beech with a new wood fire retardant agent based on in situ deposition of calcium oxalate

European beech (Fagus sylvatica L.) was impregnated in a two-step process with aqueous solu-tions of potassium oxalate and calcium chloride succes-sively. These compounds are intended to react in situ to the water-insoluble salt calcium oxalate and the reaction by-product potassium chloride. In order to assess the treatability, the solid uptake after the first impregnation and after the treatment was examined. The fixation of the precipitated salts was measured in leaching tests accord-ing to the European standard EN 84. The reaction to fire of mineralized beech was tested following the standard ISO 11925-2. A weight percentage gain of appr. 35% indicates a sucessful treatment of the beech with the mineralization agents. The weight percentage gain after leaching indi-cates a sufficient fixation of calcium oxalate in the wood. Furthermore, results from flammability tests indicate improved fire resistance due to the mineralization