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

Vlachou-Mogire, C; Drakaki, E; Serafetinides, AA; Zergioti, I; Boukos, N

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	https://dspace.lib.ntua.gr/xmlui/handle/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