Laser-Assisted Method for Cleaning and Analysis of Archaeological Metallic Coins

Abstract

Metal coins discovered during archaeology have artistic and cultural value. Careful cleaning is required for artifact conservation. Metal artifacts must be cleaned to remove corrosion, which can range from tarnishing to a thick crust, in addition to dust, previous coatings, and burial deposits. Cleaning corrosion is still a challenging conservation process, but the advantages of using traditional cleaning methods outweigh the disadvantages. The current study aimed to evaluate the use of a nanosecond infrared Q-switched Nd: YAG pulsed laser for biodeteriogen elimination by laser cleaning and elemental analysis via LIBS analysis on old, corroded coins. The corroded coins used in this study were found in Egyptian burial dirt. Four different varieties of unknown corroded coins were exposed to laser cleaning testing. Throughout the cleaning process, LIBS diagnostics was used to monitor the laser ablation process as it removed various types of corrosion products. The coins were analyzed with a scanning electron microscope equipped with an energy-dispersive X-ray analyzer before and after the laser cleaning to assess the efficacy of the suggested laser setup technique used in this experiment (SEM-EDX). The results show a reduction in the spectral lines of corroded metals (Cu, Ca, and Mg) in the investigated coins after cleaning when compared to the original analyses. However, the surface morphology of each coin changes somewhat due to the presence of CuOx, which was recognized by increasing the strength of O lines, ensuring the viability of utilizing LIBS to identify the unknown coins tested.

Comparative Study between First and Second Harmonics of a Nd:YAG Laser for Cleaning Manifestation Damages That Appeared in Pigments Used on Archaeological Cartonnage

“…Recently, this type of laser has been developed to emit radiation at λ = 532 nm (2ω), λ = 355 nm (3ω), λ = 266 nm (4ω), and λ = 213 nm (5ω) multiples of the fundamental wavelength using nonlinear crystals. It is used for restoration purposes [ 11 ] due to its relatively low cost, its availability and portability, the immediate control of the device, and the flexibility that the device provides in terms of pulses [ 12 , 13 ].…”

Ag and Sn Implications in 3-Polker Coins Forgeries Evidenced by Nondestructive Methods

“…Furthermore, these methods did not allow for a direct correlation to the investigated area microstructure. The SEM-EDX elemental investigation has the advantage of being able to properly choose the investigation site on the artifact surface, allowing us to avoid dirt and corroded spots [20,21]. Another advantage is being able to couple them with high-resolution images of the microstructure.…”