Synthetical tannins and natural extractives of oak, spruce and chestnut have been combined with different fungicides to make the wood more dimensionally stable and more durable. The anti-shrink-efficiency and the improvement of the durability of different synthetical and natural tannins have been evaluated. The results make clear, that an application of the mentioned agents for common use cannot be recommended without further preface. Under "moist" conditions (high relative humidity) none of the tested tannin/preservatives seem suitable for the treatment of beechwood. All the combinations of tannins and preservatives are hygroscopic and poor in fixation and therefore leach quickly. The result of the soil block test too, (approx. 15% weight loss of specimens at relative high loadings of preservatives) is not sufficient to recommend application. Further research has to demonstrate, whether with softwood species better results can be achieved. Furthermore, different concentrations of the most promising agents (tannins and chromium containing salts) have to be tested to determine optimum retentions and toxic values before and after leaching. A considerable improvement of the dimensional properties (ASE 50-75%) was obtained by a treatment with Tannin AKF in ranges of low relative humidities (0-60% RH). Under these dry conditions, however, no fungicides are needed.

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