Soiling of Wood-Based Materials by Algae and Its Prevention

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For the evaluation of the algal soiling of wood-based materials, a new accelerated test method under outdoor conditions was designed and applied to the different types of sample boards. The test method consisted of exposure with 45 degree inclination facing to the north and mist-spray of water including ammonium phosphate as a nutrient. The species of the algae and their development on the specimens detected within 3 to 5 months were closely correlated with those observed by surveys on the external surfaces of buildings on the current situation. The newly designed test method was assumed to be suit for estimation of the algal growth on external materials within a short period representing the natural soiling.The cultivation method consisting of spraying the algal cells and the nutritional solutions, as well as in a room conditioned at high humidity and sunshine was assumed to be an effective technique to estimate the degree of algal soiling in a laboratory experiment.When the accelated test method was conducted to the different types of external materials, a rapid development of algal soiling was detected on the ssmples which easily absorbed water from these surfaces.