The conservation and restoration project for the entire collection of property from the frigate Nuestra Señora de la Mercedes – established as one of the cornerstones of the plan of action following the return of said cultural property to Spain – is a huge challenge for those who work in the field of heritage. While any intervention on items found underwater is always particularly complex, in the case of the items making up this historical collection, it was its sheer size – over 14 tons of mainly gold and silver coins – that made it even more special.
Once the collection had been transported and stored, the aim of every action has been to preserve it by minimising the development of degradation processes by controlling the main risk factors. At the same time, and in order to prepare an initial diagnosis of the condition of the recovered material, the first studies and analyses were conducted on both the liquid the material contained as well as any corrosive products and other deposits found on the surface of the metal.
After examining these preliminary studies – and once the first treatment tests had been carried out – a technical committee of experts from various institutions, specialising in metallic materials of underwater origin, met at ARQUA (the National Museum of Underwater Archaeology) in March 2013 in order to establish the strategies and methods of action to be implemented.
The main intervention goals established at this meeting were to ensure the stabilisation of the entire historical collection, as well as recovering its legibility and its correct interpretation via the application of specific treatments according to the pathologies shown by the different groups of items.
Thus, the main treatments examined were: removing the concretions, deposits and unstable elements that were not part of the original pieces; consolidating groups of items at risk of disintegrating; inhibiting active corrosion; and the application of a protective layer and preventive conservation measures against external agents. These must always be carried out as outlined by the current conservation and restoration criteria adopted by the Spanish legal system such as: minimal intervention; the use of proven and fully justified treatments; and respect for the material history and the nature of the items.
Once the intervention has been concluded, all the information gathered during the process will be compiled in a corresponding technical report. This will then establish a line of research so that this find can be approached as a global project for scientific study and the conservation of underwater cultural heritage will be available to society as a whole.
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