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Palomar T.,CSIC - National Center for Metallurgical Research | Ramirez Barat B.,CSIC - National Center for Metallurgical Research | Garcia E.,Instituto Del Patrimonio Cultural Of Espana Ipce | Cano E.,CSIC - National Center for Metallurgical Research
Journal of Cultural Heritage | Year: 2016

Tarnishing is produced by reaction of silver with gaseous reduced sulphur compounds from atmospheric pollution. It induces the formation of Ag2S crystals which produce a dark appearance. To remove sulphur tarnishing, different mechanical, chemical and electrochemical methods have been traditionally used. To assess the effect of different cleaning treatments on tarnished silver, coupons of pure and sterling silver (92% Ag/8% Cu) were subjected to six cycles of induced tarnishing and cleaning. The cleaning methods evaluated were mechanical (soft abrasives and rubber point mounted on a rotary tool); chemical (chelating and acid solutions) and electrochemical (potentiostatic reductions). Surface morphology, composition, weight, color and luminosity were evaluated by optical microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy and colorimetry. The cleaning impact on tarnished silver depended on the cleaning procedure and the composition of silver. Mechanical treatments restored the original visual appearance of silver although they produced a significant mass loss and a fast re-tarnishing. Chemical cleaning methods were fast; nevertheless the surface appeared completely attacked. Electrochemical cleaning did not yield good result for sterling silver, but was an effective cleaning method for pure silver coupons. © 2015 Elsevier Masson SAS.

As a result of the earthquake on 11 May 2011 the Lorca municipal archaeological museum suffered serious damage to its structure and its exhibits. The lack of preventive measures and the inadequacy of steps taken before the earthquake aggravated the severity of damage. We have assessed the damage to the exhibits and analysed the causes that exacerbated the impact of the seismic movement. We also describe the work carried out by the Institute of Spain's Cultural Heritage (IPCE) to recuperate the collections and detail the measures and general criteria for the prevention and minimization of damage that the museum must implement to reduce the damage to its collections to a minimum during any subsequent earthquakes.

Palomar T.,CSIC - National Center for Metallurgical Research | Ramirez Barat B.,CSIC - National Center for Metallurgical Research | Lafuente D.,CSIC - National Center for Metallurgical Research | Cano E.,CSIC - National Center for Metallurgical Research | And 2 more authors.
Science, Technology and Cultural Heritage - Proceedings of the 2nd International Congress on Science and Technology for the Conservation of Cultural Heritage, 2014 | Year: 2014

Different mechanical, electrochemical and chemical methods have been used for many years to remove sulphur tarnishing from silver artefacts. To evaluate the effects of these methods on the metal, silver coupons have been subjected to 6 cycles of tarnishing and cleaning. The cleaning methods evaluated have been mechanical (soft abrasives and polishing); electrochemical (potentiostatic reductions) and chemical (chelating and acid solutions). The abrasives left a smooth surface, since the chemical and the electrochemical methods left a rough texture. The thiourea-acid solutions removed a similar percentage of silver than mechanical methods, while the mass of silver cleaned with electrochemical treatments remained constant. The thiourea-acid solutions and the potentiostatic reductions were the most effective tarnishing cleaning methods; although the samples cleaned by a potentiostatic reduction presented a yellowish color and the residues from thiourea acid solution can act as points of re-tarnishing. © 2014 Taylor & Francis Group, London.

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