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Experimental study on the effect of wavelength and fluence in the laser cleaning of silvering in late Roman coins (Mid 3rd / 4th century AD)

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dc.contributor.author Vlachou-Mogire, C en
dc.contributor.author Drakaki, E en
dc.contributor.author Serafetinides, AA en
dc.contributor.author Zergioti, I en
dc.contributor.author Boukos, N en
dc.date.accessioned 2014-03-01T02:51:05Z
dc.date.available 2014-03-01T02:51:05Z
dc.date.issued 2007 en
dc.identifier.issn 0277786X en
dc.identifier.uri http://hdl.handle.net/123456789/35356
dc.subject Laser cleaning en
dc.subject Nd: YAG laser en
dc.subject Roman coins en
dc.subject SEM- EDX analysis en
dc.subject Silver amalgam plating en
dc.subject.other Chemical cleaning en
dc.subject.other Energy dispersive spectroscopy en
dc.subject.other Neodymium lasers en
dc.subject.other Optical microscopy en
dc.subject.other Scanning electron microscopy en
dc.subject.other Silver en
dc.subject.other Wavelength en
dc.subject.other Laser cleaning en
dc.subject.other Quaternary alloys en
dc.subject.other Roman coins en
dc.subject.other Silver amalgam plating en
dc.subject.other Surface cleaning en
dc.title Experimental study on the effect of wavelength and fluence in the laser cleaning of silvering in late Roman coins (Mid 3rd / 4th century AD) en
heal.type conferenceItem en
heal.identifier.primary 10.1117/12.726984 en
heal.identifier.secondary http://dx.doi.org/10.1117/12.726984 en
heal.identifier.secondary 66040W en
heal.publicationDate 2007 en
heal.abstract The political problems in Late Roman Empire caused significant changes in the coin technology. The silver content dropped severely and a new technology, in all the mints operating around the Empire, was introduced. For the production of these coins, copper based quaternary alloys were used and their surface was covered by a silver amalgam plating layer. Hoards of these coins have been recovered in thousands from across the Empire, however, their treatment has been problematic. Both mechanical and chemical cleaning results in the damage or the complete destruction of the thin silver layer. The use of laser technology in the cleaning of works of art has a wide range of applications which includes metallic objects. The main aim of this work was to investigate the use of lasers in the cleaning of the thin silver plating layers found in late Roman coins. The optimisation of laser parameters was achieved through comparative cleaning tests by employing Nd:YAG (532 nm and 266 nm) laser systems. The cleaning results on the plated areas were characterised by optical microscopy, and SEM-EDX analysis. Following a systematic investigation and many cleaning trials on two different wavelengths and fluence values, optimum irradiation parameters were thoroughly demonstrated. Microscopic observations of the cleaned areas evidenced complete removal of the encrustation and high selectivity of the laser cleaning. Neither thermal or mechanical injuries, nor cuprite blackening were observed on the cleaned surfaces at the optimum laser cleaning technique, using 532 nm of the Nd: YAG laser. en
heal.journalName Proceedings of SPIE - The International Society for Optical Engineering en
dc.identifier.doi 10.1117/12.726984 en
dc.identifier.volume 6604 en


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