Experimental investigation on cleaning of corroded ancient coins using a Nd:YAG laser

Huazhong Zhu; Jian Lu; Xiaowu Ni; Zhonghua Shen

doi:10.1117/12.2268329

12 May 2017 Experimental investigation on cleaning of corroded ancient coins using a Nd:YAG laser

Huazhong Zhu, Jian Lu, Xiaowu Ni, Zhonghua Shen

Proceedings Volume 10173, Fourth International Symposium on Laser Interaction with Matter; 101730F (2017) https://doi.org/10.1117/12.2268329
Event: 4th International Symposium on Laser Interaction with Matter, 2016, Chengdu, China

Abstract

The objective of the work reported is to study experimentally on the removal of corrosion layer from the ancient coins using laser beam as the conservation tool. With the use of Q-switched Nd:YAG laser radiation at 1064 nm, dry laser cleaning, steam laser cleaning and chemical-assisted laser cleaning were used to find out a more suitable and efficient laser treatment for corrosion removal. Cleaning tests were performed on ancient Chinese coins. Experimental results shows that the dry laser cleaning was not successful at removing all types of corrosion crust. It was possible to remove the outer thicker layer of the corrosion products (typically known as patina), but failed on the thinner layer of cuprite. The steam laser cleaning could decrease the initial removal threshold and improve the removal efficiency especially for the oxidation with powdery structure. As for chemical-assisted laser treatment, the cleaning results demonstrate that the combination of laser and chemical reagent could provide a considerable improvement in corrosion removal compared with the conventional laser treatments. Most of the corrosion contaminant was stripped, even the cuprite layer. Moreover, no secondary pollution was formed on the cleaned surface. X-ray fluorescence was applied to determine the variation of composition of surface layer and bulk metal before and after the coins cleaned. It shows that all of the three laser treatments were efficient to reduce the chlorine concentration on the surface of the coins more than 75%.

Citation Download Citation

Huazhong Zhu, Jian Lu, Xiaowu Ni, and Zhonghua Shen "Experimental investigation on cleaning of corroded ancient coins using a Nd:YAG laser", Proc. SPIE 10173, Fourth International Symposium on Laser Interaction with Matter, 101730F (12 May 2017); https://doi.org/10.1117/12.2268329

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