The Project

The present project focuses on the conservation of gilded bronzes, used since ancient times to craft objects, sculptures and architectural elements, which represent an important and precious part of Cultural Heritage. The preservation and the monitoring of such a unique patrimony against indoor or outdoor corrosion is a very difficult problem, which in the case of precious masterpieces is not solved by current maintenance and protection procedures due to the presence of the gilding.

The main goals of this projects are the development of innovative conservation methodologies for outdoor and indoor gilded copper alloy artworks based on both controlled environmental conditions and non-toxic, side effect-free treatments. Their effectiveness will be assessed using innovative non-invasive diagnostic techniques.

In particular, the research is subdivided as follows:

• Set up of a novel controlled-microclimate open showcase.

• Realization of artificial patinas by accelerated ageing and by chemical and electrochemical techniques.

• Specific inhibitors will be devised and systematically tested on sets of samples including patinated and gilded copper alloys.

• Development of galvanic sensors for monitoring the degradation rates due to gold/bronze coupling, under different conditions of temperature, humidity and atmosphere composition.

• Use of electrochemical techniques, such as linear polarisation resistance (Rp), Electrochemical Impedance Spectroscopy (EIS) and macrocouple current measurements to investigate inhibition efficiency and mechanisms and for the in situ monitoring of samples exposed to the atmosphere.

• Careful characterisation of materials and surfaces, before and after inhibitive treatments. This phase of the project is really important to follow up the evolution of the treatments deterioration and to understand the basic corrosion and inhibition mechanisms.

• Evaluation of the reversibility/re-applicability of protective treatments by exploiting the high selectivity of laser cleaning and other low impact cleaning methods.

The results obtained until now in the framework of this project contributed to the choice of the correct exhibition condition and to the monitoring of the Porta del Paradiso, Early Renaissance gilded bronze masterpiece, crafted by Lorenzo Ghiberti, exposed at the Opera di Santa Maria del Fiore's Museum, in Florence.