Effect of natural aging on the chemical composition of norway spruce, fir, and european oak wood.

The chemical composition of a number of naturally aged construction wood samples of spruce, fir and oak was investigated. The content of lignin, polysaccharide, and extractives was determined using wet chemical and chromatographic methods. Differences to non-aged wood samples were found particularly found on oak wood samples with regard to lignin and polysaccharide content as well as to cellulose crystallinity. The composition of wood extractives of aged and non-aged wood samples revealed degradation processes due to oxidation and slight hydrolysis. The investigation showed that the relative content of the structural wood constituents depends on the sample age as well as the conditions they were aged under. The different degradation rates of those structural components may lead to contradictory results regarding their contents at certain degrees of aging. Cellulose crystallinity values are affected by extractives content.