used a Q-switched Nd:YAG laser, at 1064 nm with pulse duration 5 ns, for the cleaning treatment of silver–copper coins with a fluence of 1.6 J/cm 2, while the number of pulses was depending on the thickness of the corrosion layer. Laser cleaning tests on coins have already been performed with either promising or forbidding results.

This research focuses on evaluating cleaning procedures of metallic coins by an Nd:YAG laser irradiating with 1064 nm.

Often still, it leads to novel findings, further extending the potential of laser in cleaning those objects. However, the large variety of materials used to fabricate the available cultural artifacts is not fully covered, allowing significant space for further investigations. Laser cleaning of cultural heritage objects is not new and already has many practical applications. Most of the contemporary lasers are easy to use and fully parameterized through computer interfaces, offering promising results when used as a cleaning tool of artifacts with cultural value. For low corrosion level on copper alloys, a thin water film on the irradiated area is beneficial. Also, higher level of corrosion and accretions requires higher laser intensity. From this research, it was found that the laser cleaning of copper, silver and aluminum alloys is feasible with Q-switched Nd:YAG at 1064 nm. Finally, the result is evaluated by using microscopic methods. Exploiting this information, laser cleaning of coins is performed with various conditions and parameters. This information along with the composition of the coins’ alloys is fed into an in-house developed program which estimates the penetration depth of the laser beam as well as the laser fluence for which the alloy starts to melt. Coins are studied with analytical methods in order to detect the corrosion products and the accretions. In this work, the laser cleaning of coins is examined. Due to the different behavior of each material, when it is irradiated, studies and experiments are performed in order to find the optimum laser parameters for each case. Laser-based techniques are used more and more frequently for the cleaning of artifacts.

Aa coins artwork