Terracotta policrome scultures examined bifore and after their conservation work: contributions from non- invasive in situ analytical techniques

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Esperienze innovative e conferme nei trattamenti a base di ossalati solubili su superfici lapidee e leghe metalliche: intervento e monitoraggio nel cantiere del portale di Santa Maria delle Grazie a Milano.

The Lombard Direction for Cultural Heritage has promoted in 2006 on the portal of the Church of Santa Maria delle Grazie in Milan, a research and conservation yard with the aim to refine the existent conservative strategies and to develop new ones. The portal is mainly made by Candoglia marble, with a frescoed lunette above and a copper roofing. It presents a compromised state of conservation, mainly due to chemical attack by Milan atmosphere and to particulate deposition on the surface. On the basis of preliminary diagnostic studies and tests in situ, the employ of inorganic consolidant treatments has been chosen, and so ammonium oxalate has been applied on stone and sodium oxalate on copper roofing. Actually the monitoring of surfaces is in progress, in order detect the decay progression and define a conservative plan that allows to stop decay with as light as possible works