THE IMPORTANCE OF STONE CHOICE AND PROCESSING OF THE STONE SURFACE DUE TO GRAFFITI

Sa？etak New ventilated stone coverings of main facade of Mining-geology-petroleum engineering and Food-biotechnology faculty in Zagreb has been tinted and disfigured with numerous graffiti drawings. Today fa？ade requires cleaning and restoration with relatively high costs. The reason of this is not best choice of stone and relatively poor protection against of graffiti. When trying to choose the best agent for cleaning and removal of graffiti very interesting results achieved. Test is subjected with two natural stone varieties. One of them is stone veselje unito which fully corresponds that which is on the fa？ade. Natural stone sivac is chosen as a possible potential variety of other fa？ades. The paper presents petrographic and physical features of both varieties. Conducted tests allow better understanding of problems during the selection of the stone and cleaning of both varieties. Both stone varieties are in origin from quarries from island of Bra？. Totally unexpected, due to the nature of pores, stone variety sivac proved to be better choice. This variety, due to smaller and homogeneously distributed pores much better receiving protective coating agents. It is found that from its surface graffiti could be much better, faster and easier cleaned, without the rest of colours. Variety of stone veselje unito sporadically contents pores considerably larger sections. Protective agent as well as colours of paint spray for drawing the graffiti easily enters in the pores of stone because of their size. Colour from the pores and cavities are much harder to clean. Also is found that the colours of graffiti could be better and easier to clean from the surface which is as a consequence of stone cutting with diamond tools