Measures for the maintenance of untreated wood facades

Untreated wood facades often show discoloration after a certain life time. In this study various untreated wood facades were cleaned by high pressure water spray with different parameters. The color of the facade was determined in the CIE L*, a*, b* system and small samples were taken on the surface for electronic microscopy analysis before and after each treatment step. The results show that it is possible, with adjusted parameters and without the pre-treatment with detergents, to obtain a good color homogenization on the facade. Grayed facades become considerably brighter and get back a yellow-red tone. The achieved color is often slightly different from the original color. Inhomogeneous south-facades become more homogenous and their strong red coloration gets reduced. The microscopy investigations show that after the treatment almost all spores, fibers residues and dust particles are removed. The compounds of the middle-lamella have been washed off; cleaned fibers remain on the surface. This leads to a slight woolly surface effect. In future work the durability of this technique will be investigated.