Science

Programme "Scientific projects"

Labelling Ancient Coins from Collections in the Numismatic Museum, Athens, and cleaning them with Laser Beams

Physics Department, School of Applied Mathematical and Physical Science, National Technical University of Athens

2009

This study aimed at promoting and advancing contemporary methods of cleaning ancient coins with the use of laser technology, contributing to research on the conservation of ancient metal objects.

The most suitable laser source and the most effective way of its application were found by employing several lasers sources (e.g. Nd:YAG - w - 2w - 3w - 4w, FL Nd:YAG – w, LQS Nd:YAG – w, Er:YAG, ΗF, CO2, GaAlAs, etc.) with different wavelengths and pulse durations in the cleaning procedure, either with direct illumination, with the use of an optical fibre, or with the use of a motorised microtranslation stage.
The research was initially carried out on standard samples and relatively modern coins, and then on small parts of the surface of ancient silver and bronze coins, of different metal alloys and corrosion types, from the collections of the Athens Numismatic Museum.

The results of each application evaluate mainly by optical microscopy, by scanning electron microscopy (SEM), and by X-ray fluorescence (XRF).

The LQS Nd: YAG Laser, at 1064 nm, gave the best (excellent) results in cases of silver coins with a thick layer of corrosion products and deposits (Fig.1-3), as well as with soil deposits.

It also produced very good results with copper alloy coins, removing friable products from surfaces. Other lasers gave also very good results, depending on the characteristics of each coin.

Comparison with traditional cleaning methods showed that the choice of a specific treatment depends on the coin alloy, the type and products of corrosion, and the optical properties of the laser beam.

Final report (in Greek)

PHOTO GALLERY

Coordinator:

Alexandros-Panayiotis Serafetinidis, Professor, Physics Department, School of Applied Mathematical and Physical Science, National Technical University of Athens

Project's Team:

Myrsini Markopoulou, Assistant Professor, National Technical University of Athens

Michalis Kokkoris, Associate Professor, National Technical University of Athens

Roza Vlastou, Professor, National Technical University of Athens

Eleni Drakaki, Research Physicist, National Technical University of Athens

Bernhard Klinkenberg, Independent Consultant, Electrical Engineer

Ioannis Tsilikas, Independent Consultant, Computer Scientist

Despina Evgenidou, Director, Numismatic Museum, Athens

Niki Katsikosta, Conserver, Numismatic Museum, Athens

Elena Kondou, Conserver, Numismatic Museum, Athens

Konstandina Vlachou, Conserver, Numismatic Museum, Athens

Panayiotis Tselekas, Archaeologist, Numismatic Museum, Athens

Andreas Karydas, Physicist, Institute of Nuclear Physics, National Centre of Scientific
Research "Demokritos"

Viki Kandarelou, Physicist, Institute of Nuclear Physics, National Centre of Scientific
Research "Demokritos"

Anastasios Travlos, Physicist, Institute of Materials Science, National Centre of Scientific
Research "Demokritos"

Nikolaos Boukos, Physicist, Institute of Materials Science, National Centre of Scientific
Research "Demokritos"

9, Iroon Polytehniou St.

15870 Zografou Athens

Tel.: +30 210 77 23 032

Fax.: +30 210 77 23 025

e_phys@mail.ntua.gr

www.physics.ntua.gr/index_en.html

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