Alterazioni cromatiche di materiali lapidei carbonatici: studio delle macchie indotte dalla coesistenza con materiali ferrosi e metodi innovativi per la loro rimozione

Carbonatic stones artifacts, especially those in outdoor environments, undergo chemical, physical, biological and anthropic degradation or at least alteration. A remarkable aesthetic impact rises from the presence of stains based on metal compounds that can be attributed to extrinsic (metal-stone contact) or intrinsic (oxidation of iron minerals in the stone) factors. The iron staining, especially on light-colored stone, is generally considered to be one of the most difficult problem encountered in the cleaning of porous building materials. Here we present a research starting with a preliminary chemical and morphological characterisation of iron based stains, on carrara marble and travertine, and ending with a cleaning procedure by innovative chemical and biological treatments. We used several analytical methods on both ancient artefacts and simulated samples, in order to individuate the iron compounds that are more frequently found. A natural staining was chosen, i.e. the exposition of marble and travertine in contact with iron on a terrace. The most efficient chemical and biological solution were individuated and optimized