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In order to optimize the gluing performance of wood splints with KPVAC-glues, it is of utmost importance to know the amount of water able to penetrate into the gluable wood splints. Therefore, in this study two techniques to measure the water absorption ability of building materials were applied on a variety of 40 representative tropical and native European wood species. The first method is a common German standard and measures the water absorption coefficient w t . The second is based on the determination of the wettability of surfaces by measuring equilibrium contact angles of liquid water. Using a similar technique, we have concentrated our research on the dynamics (non-equilibrium) of a water drop contact angle. Differences among species are outlined and discussed primarily with respect to wood extractives contents and wood densities. Even though it must be assumed that both techniques are based on equal mathematical relations, a poor correlation was obtained.

An investigation of the water protection capacity of modern paints with low organic solvent content was carried out as part of an European research project. The wider scope of the project was to establish the performance and durability of these new coatings applied to window joinery made from European softwood species. The aim of the moisture studies was to employ well-proven methods to determine the liquid water absorption of the coatings. A range of standard moisture permeability tests, carried out on coating systems applied to pine and spruce substrates, indicated a high correlation between similar data obtained using different techniques at different laboratories. The results showed that permeability of the coatings tested did not depend on the timber substrate, as long as the permeability was expressed in absolute terms and not relative to the absorption of uncoated wood. The results from this study will be used to determine whether laboratory measurements of the moisture transmission properties of a coating can be used to predict outdoor weathering performance.

The influence of some parameters (wood species, binder content, water repellent finish, wood humidity and roughness) on the wetting of MDF was investigated by means of contact angle measurements with selected test liquids (water, glycerol, ethylene glycol and diiodmethane) using the sessile drop method. The investigations show that contact angle measurements are mainly disturbed by the penetration of the liquids into the MDF and by the high roughness of the surface. Therefore, the results have principally qualitative character. They represent the following tendency for the five parameters: the use of water repellent finish, increased wood humidity and increased roughness made wetting less effective with water repellent finish showing by far the biggest effect. MDF made of beech showed predominantly better wetting behaviour than that made of spruce. The influence of the binder content could not be unambiguously ascertained.

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