INNOVATIVE METHODOLOGIES TO REMOVE STAINS FROM STONE SURFACES BASED ON NATURAL PRODUCTS

Participation of the authors at the National Smart Cities project (SCN 00520) was focused on proposing ecological innovative materials to restore stone cultural heritage. The shift from synthetic to natural compounds is a general trend, especially in the field of cultural heritage where the use of the former ones resulted in dangers for environment and restorer's health. Looking at this aim we paid our attention to two natural proteins, lactoferrin and ovotransferrin, identified and tested for the removal of iron-based stains on marble surfaces ensuring a safe cleaning method able to reduce professional diseases and pollution. The two proteins, of which is well known the ‘in vivo’ high affinity for iron, were firstly extracted in our lab from their natural matrices. The protein extracts were then gelled using a common cellulose pulp. The obtained gels were spread on the iron-stained surfaces and, once their action fulfilled, promptly removed. Comparative surface analysis by XPS of marble samples (a: white; b: long-time rusted and c: 'b' treated with gelledproteins) shows the complexing reactivity of both proteins. Their efficacy, visually confirmed by the spectrocolorimetric analysis, is discussed in the light of the curve fitting results of all the detailed spectra.