Bronze cultural relics are an important part of Chinese traditional historical and cultural heritage. With the rapid development of ultrafast lasers in recent years, picosecond lasers have gradually been used in laser precision processing due to their controllability, reliability and low cost. With the increase of laser power, the laser ablation effect will occur[1].The contaminant on the surface of bronze cultural relics are thinner compared to that on other type of cultural heritage and need more accurate cleaning method needs to be used for removing contaminants without damaging the substrate of bronze relics. In 2013, Zhang Xiaotong et al. used wet laser cleaning technology to perform laser cleaning on the gilt bronze statues provided by Hebei Cultural Protection Center. They changed the power density, conducted preliminary trials of bronze cleaning [2]. In 2018, Shen Yijia et al. used agar gel and laser combined method to protect the bronze cultural relics from laser damage[3].
Cleaning of naturally formed pollutants and man-made adhesive materials on the surface of ceramic cultural relics is very important to the restoration and protection of ceramic cultural relics. With the rapid development of laser technology, laser cleaning has been successfully applied in the field of cultural relics cleaning due to its advantages of selectivity, controllability and high stability in the past two decades. In this manuscript, laser cleaning of virous pollutants on the surface of ceramic relics using a nanosecond fiber laser has been investigated experimentally. Cleaning parameters such as laser power, scanning speed and cleaning time have been changed to optimize the cleaning effect with different pollutants. The components of pollutants were analyzed by fluorescence spectrometer, while the morphologic changes of samples before and after cleaning were observed by a confocal microscope. The optimal cleaning parameters are obtained with virous pollutants respectively and it can provide effective support to the protection of ceramic relics.
Laser damage threshold is one of the most important parameters for optical materials used in ultrafast laser system and the related application system. We have investigated experimentally laser damage threshold on the surface of gold sample induced by femtosecond laser pulses using a so called ablation diameter regression technique. More than one ablation regime, which has logarithmic relationship between the ablated diameter and the laser fluence, has been found. Correspondently, laser damage threshold for gold sample is almost one order of magnitude in difference, from 1.55 J/cm2 to 12.01 J/cm2 . In our opinion, accurate calibration of the damage threshold for optical components should be done with laser fluence close to the damage threshold.
The ceramics is easily broken due to various reasons. These reasons include unearthed excavation, careless operation and so on. When the ceramics is broken in pieces, the antique restorers take advantage of the adhesive to stick these fragments together to exhibit the beauty of original cultural relics. Therefore, the removal of adhesives such as adhesives on the cross-section of ceramic samples is a very important link in the restoration and protection of cultural relics and has important significance. In ancient times, the way of restoring these ceramics is so inappropriate and unreasonable that the adhesive is left among the cross section of these pieces. It becomes a problem for the following antique restorers. In order to solve this problem, we select a piece of the ceramics that possess above characteristics by utilizing laser to clean the left adhesive on the cross section tentatively. To better explore the optimized cleaning parameters relatively, we have made standard samples of adhesive to get better cleaning effect. These results will provide the reference value to our following study.
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