It is common, in fact, that the corrosion products, dissolved and washed by rain, can reach portions of the nearby stone surfaces. Outdoor bronzes are subjected to continual corrosion and dissolution processes, as well reported in literature : associated with these processes are the coloured stains often observed on stone surfaces of outdoor monuments as the results of leaching from the attached bronze artefacts exposed to rainfall. In this work we have analysed samples from two modern limestone monuments in Rome, the Botticino surfaces of the ‘Vittoriano’ (by G.Sacconi, 1885-1911- Piazza Venezia) and the travertine basement of the ‘Statua dello Studente’ (by A.Cataldi, 1920- University city, La Sapienza), and focussed our investigation on the chemical composition of the copper-stained zones using XPS (X-ray Photoelectron Spectroscopy) as a surface-specific technique.īased on observations reporting on the structure and bonding at the calcite surfaces we have identified copper complexes and mixed calcium/copper carbonates associated with the stains, as well as the chemical state of other elements therein included, and related the compositional changes with differences in chromatic characteristics and sampling locations. In outdoor conditions, such a combination implies the corrosion products of the copper based alloy, directly exposed to rainwater, will be drained off and migrate through the porous surfaces, forming stains of different colours and intensities, finally causing the limestone structures to deteriorate. Similar analysis technique is applicable to evaluation of change in binding before and after oxidative treatment of a thin film surface and to determination of a valence of metallic elements in a transparent conductive film (ITO).Limestone basements holding bronzes or other copper alloys artefacts such as sculptures, decorations and dedicatory inscriptions are frequently met both in modern and ancient monuments. Looking at each peak dividing a spectrum, a location of peak indicates a biding state and an area of peak indicates a ratio of binding. Amount of peak shift is different at each binding and, therefore, C1s and O1s spectra are obtained by combination of multiple peaks (see a red line in Figure 2). PET has a structure in which carbon and oxygen atoms have multiple bindings individually as shown in Figure 1. Shown below is an example of chemical binding analysis of polyethylene terephthalate (PET). X-ray photoelectron spectroscopy (XPS) can analyze a chemical state of element present on a sample surface by utilizing a change in binding energy (a shift of peak in a spectrum) with a change in chemical binding with surrounding elements.