CONSERVATION TREATMENT OF INLAID OBJECT BY PLASMA

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Many of the inlaid artifacts found at ancient tomb in Japan have inscription like a two famous national treasure swords. As such, they supply a wealth of data for studying history. In recent years, a lot of objects with inscriptions have been unearthed one after another, and most of their inscriptions have been successfully read by removing rust and other dirt with rewarding great results in academic research. The conventional method of scraping off rust The layrs, however, has a risk of distorting the strokes of charactrs somewhat and there by losing data of manufacturing processes.Using hydrogen plasma to remove rust layrs from the surfaces of inlay is an effective method free from such a risk.Rust examples taken off inlays were analyzed by X-ray diffraction, and it was found that the rust teratment with hydrogen plasma and oxygen plasma, the rust examples were examined to find out the optimum comditions of treatment through observation of their change. The results were as follows :H … More igh frequency : 13.56MHz,High frequency output : 2kWTemperature : About 200ﾟCInjection amounts of gases :Nitrogen : 400ml/min, Hydrogen : 400ml/min, Argon : 200ml/minThe mechanism of how rust layrs become friable enough to be scrapped off has also been found. Rust of trivalent metal such as iron hydroxide and magnetite is reduced through reaction with hydrogen plasma, and a resultant change in the volume of the rust layrs, coupled with the effect due to heating under a state of pressure redaution, contributes to the friable of the rust layrs.After treating the rust layrs with plasma, it became possible to uncover the inlays by carefully removing the friable layrs of rust with a bamboo stick while observing them with a stereomicroscope. This method is free from any harm to inlaid lines and consequently best-suited for processing the inlaid inscriptions of excavated artifacts. The method has come tobe established fully as a practical method through a series of experiments, and there are already more than 10 actual examples of its application for conservation treatment. Less