Application of photocatalyst into the building materials and components is rather newly developed technology. One of the advantageous features by applying this photocatalyst would be the capability of self-cleaning or self-desoiling on the surface of materials. This paper introduces the results of the outdoor exposure test and the laboratory tests for the various exterior finishing materials treated with photocatalyst. On the basis of the results obtained from both outdoor exposure (already reported as in AIJ Trans. No.564, 2003) and laboratory analysis, the following conclusion could be made at present; Rather high correlation between the water contact angle of outdoor exposed specimen and the color (value) difference could be recognized, the higher hydrophilic nature shows the more desoiling nature under the water contact angle less than 70 degrees, and water contact angle would be one of the key factor for evaluating self-cleaning effect.
