The application of X-ray Fluorescence Spectroscopy Analysis in Ancient Ceramics and Bronze Wares

Science and technology are in a stage of continuous progress and development. Archaeology is no longer confined to the traditional level of archaeology, and science and technology are increasingly applied to the study of cultural relics. Inorganic material testing technology is one of the main methods used in the research of ancient ceramics in recent years. It can make up for the deficiencies of traditional archaeology in studying the composition and structure of substances, porcelain-making techniques, etc., and provide necessary methods and means for exploring the development level of ancient ceramic science and technology as well as the development level of ancient social economy and culture. Inorganic material testing techniques include electron probe X-ray microscopy analysis, X-ray photoelectron spectroscopy analysis, X-ray diffraction analysis (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES), etc. According to the difference in dispersion, X-ray fluorescence spectroscopy analysis can be divided into wavelength dispersive X-ray fluorescence spectrometer (WDXRF) and energy dispersive X-ray fluorescence spectrometer (EDXRF). Since energy dispersive X-ray fluorescence spectrometer is frequently used in the study of ancient ceramics, this article will not introduce wavelength dispersive X-ray fluorescence spectrometer (WDXRF) in detail.

I. Applications of X-ray Fluorescence Spectroscopy Analysis

1.Appraisal of cultural relics

The appraisal of cultural relics involves two aspects: the identification of the material and authenticity of the cultural relics. To identify the material of cultural relics, sometimes one can rely on the naked eye to distinguish whether the object is porcelain or pottery, and whether it is platinum or lead. The naked eye can only help researchers determine the material of an object from the surface, and the accuracy rate is not high. To accurately determine the material of cultural relics, one still has to rely on science and technology, and draw conclusions based on the results of testing and analysis. For instance, the Southern Song Dynasty Guanzi banknote plate discovered in Dongzhi, Anhui Province. At that time, some people thought it was made of iron, but after X-ray fluorescence analysis, it was found to be lead. For instance, in the Han Dynasty, some people believed that the three-grade white gold was made of silver, while others thought it was an alloy of tin and lead. Some even deduced that it was tin based on the composition of the alloy. However, after X-ray fluorescence analysis, it was found to be lead. The identification of the authenticity of cultural relics is not merely based on their appearance. The craftsmanship of modern antique-style porcelain is almost indistinguishable from the real thing. X-ray fluorescence spectroscopy analysis can identify the authenticity of an object from its composition, with a relatively high accuracy rate. For instance, there are significant differences in composition between Longquan Kiln celadon porcelain and imitation Longquan Kiln celadon porcelain. The differences in their X-ray fluorescence spectra are quite obvious. Some imitation Longquan kiln celadon porcelain has a higher iron content and a higher aluminum content in the body composition. The proportion of these components cannot be exactly the same as that of ancient times. Therefore, X-ray fluorescence spectroscopy analysis can accurately identify the authenticity of the object.

2. Determination of the age of cultural relics

Cultural relics made of the same material have different compositions and manufacturing techniques in different dynasties. The age of cultural relics can be determined by X-ray fluorescence analysis. For instance, in the case of porcelain, the porcelain of Jingdezhen adopted different formulas in different dynasties, and its composition varied greatly. The composition of the porcelain body of Jingdezhen in the Tang Dynasty was a ratio of high silicon and low aluminum, with the content of SiO2 above 75% and the content of Al2O3 below 20%. During the Song, Yuan and Ming Dynasties, the content of SiO2 decreased by approximately 5% compared to the Tang Dynasty, at around 70%, and the content of Al2O3 was around 20%. By the Qing Dynasty, the content of Al2O3 in porcelain bodies had significantly increased, reaching over 20%. Through X-ray fluorescence analysis, the patterns of porcelain from different dynasties were different, and the age of the objects could be determined based on these patterns. In addition to ceramics, X-ray fluorescence analysis can also determine the age of other objects, such as bronze mirrors. In the Han Dynasty, high-tin and lead-containing bronze mirrors were widely used. In the Tang Dynasty, a large amount of lead was added to bronze mirrors. In the Song Dynasty, the lead content in bronze mirrors was extremely high, reaching over 30%, and zinc began to be added. After the Yuan Dynasty, white bronze mirrors were widely used, and after the middle of the Ming Dynasty, yellow bronze mirrors were adopted. Their ages can be inferred through X-ray fluorescence analysis.

3. Research on the manufacturing process

The X-ray fluorescence analysis technology can be used to obtain the composition of cultural relics, and the production situation of the artifacts at that time can be analyzed from the composition. With a microscope, an intermediate layer can be seen between the glaze layer and the body of Ru porcelain, but this intermediate layer cannot be observed with a scanning electron microscope or a polarizing microscope. Through the synchrotron radiation and energy dispersive X-ray fluorescence scanning analysis of the composition of Ru porcelain from glaze to body, it was found that there is indeed an intermediate layer between the glaze and body, and the concentrations of each element change continuously from glaze to body. Based on this, it can be inferred that the secondary firing process was adopted when firing Ru porcelain. After the body is unglazed, it is then glazed and the glazed body is placed in the kiln for a second firing. During the secondary firing process, the glaze of the porcelain becomes glassy and seeps into the surface of the body, thus forming an intermediate layer between the body and the glaze. Because the glaze in the middle layer of the body and glaze is glassy, the middle layer can be seen under a microscope, but not under a polarizing microscope or a scanning electron microscope.

Ii. Application of EDXRF in Ancient Ceramics

1. Application in the research of manufacturing processes

The composition of cultural relics can be obtained by using X-ray fluorescence analysis technology, while the chemical composition elements of cultural relics can be discovered by using energy scattering X-ray fluorescence spectroscopy analysis. By analyzing the composition, structure and properties of ancient ceramics, it is possible to infer the porcelain-making techniques and the evolution and development of technological processes at that time, providing important clues for a deeper understanding of the production techniques of ancient ceramics and cultural exchanges, etc. The chemical elemental composition of ancient ceramics was analyzed by an energy scattering X-ray fluorescence spectrometer to infer their manufacturing process. For instance, Xiong Yingfei et al. used a Quan-X type energy disperdispersion X-ray fluorescence spectrometer to test the chemical composition of the body and glaze of Yue Kiln celadon from the Tang Dynasty, Five Dynasties, Northern Song Dynasty and Southern Song Dynasty. They found that the body and glaze composition of Yue kiln porcelain conformed to the high silicon and low aluminum characteristics of southern celadon, and contained a certain amount of impurities. The calcium content in the glaze layers of porcelain throughout history was relatively high, all being high-calcium glazes. Moreover, from the Tang Dynasty until the Southern Song Dynasty, the chemical composition of the body of Yue Kiln celadon did not change significantly, while there were some differences in the composition of the glaze. Ling Xue et al. conducted a linear surface analysis of the white porcelain from Gong Kiln in the early Tang Dynasty using the Eagle II μ-Probe energy dispersive X-ray fluorescence spectrometer. They found that the makeup clay used in the early Tang Dynasty white porcelain from Gong Kiln was made of different raw materials. Some were high-alumina clings of kaolin type, while others were low-alumina clings similar to their body materials.

2. Application in the color development mechanism

The types and contents of coloring elements in the glaze layer of ancient ceramics were measured by energy dispersive X-ray fluorescence spectrometer, and the coloring mechanism and its relationship with glaze color were speculated. For instance, Sun Ying et al. conducted line scanning analysis on five samples of "Changsha Kiln" colored porcelain from the Tang and Song Dynasties in China using energy dispersive X-ray fluorescence spectrometry (EDXRF). Based on the measured changes in the content of coloring elements such as copper or iron from the glaze to the body, it can be concluded that these five samples were first glazed on the raw body and then colored on the glaze, with the coloring agent diffusing from top to bottom into the glaze layer. This overglaze dotting decorative method, which results in a gradient distribution of colorant content that is higher on the outside and lower on the inside, is not entirely a typical underglaze painting process but rather a high-temperature overglaze painting process.

3. Application in the protection of cultural relics

Cultural relics are prone to the influence of the external environment during storage. By analyzing the components that cause qualitative changes in cultural relics through an energy dispersive X-ray fluorescence spectrometer and the mechanism of the lesion, corresponding measures can be taken to strengthen the protection of cultural relics. For instance, Li Xiaoxi used the EagleⅢμ-Probe energy dispersible X-ray fluorescence spectrometer to test the chemical composition of the body and soluble salts of the ceramic cultural relics in Shaanxi. It was found that the soluble salts were mainly Nacl and also contained a small amount of Kcl. Through the simulation experiment of NaCl soluble salt lesions, it was concluded that the soluble salts were the main cause of the lesions of the fragile ceramic cultural relics samples. The prevention and control measures for soluble salt diseases were proposed.

The use of X-ray fluorescence spectrometers in archaeological excavations, the protection of cultural relics and artworks and other fields has a history of more than fifty years. But it was not until recently the development of powerful handheld devices that this non-destructive testing technology was fully developed in this field. Because it can be applied to on-site analysis work, handheld X-ray fluorescence spectrometers have also been greatly expanded in the samples that can be detected.

Oil painting

Many pigments used in paintings are carbon-containing organic substances and cannot be detected by X-ray fluorescence, except for the analysis of certain trace elements. However, there are also some pigments (especially modern pigments) that contain inorganic compounds. These inorganic substances usually contain elements such as titanium, lead, mercury, copper and zinc. Qualitative analysis of certain typical elements among them can usually distinguish different pigments.

Photocopied photos

Without additional data support, it is usually very difficult to identify the entire photocopying process. However, X-ray fluorescence spectrometers can be used to provide some supporting evidence for the identification of this process. Perhaps it is difficult to draw some individual conclusions, but the elemental information provided by X-ray fluorescence is of great benefit to the analysis of the entire process.

Ceramic

The elemental composition of clay is usually related to a specific place of origin, which makes handheld X-ray fluorescence spectrometers an important tool for on-site archaeological excavations. The information it provides is of great significance for both the protection of cultural relics and the identification of artworks.

Appraisal of cultural relics

Obsidian

The study of the origin in archaeology is based on the theory that items in the sense of civilization can be traced back to their origin in the geological sense. Obsidian is a rare product produced during volcanic activities and was widely used by the ancients. Usually, its appearance is bright black, but sometimes it also appears red or green. X-ray fluorescence spectrometry and neutron activation analysis have been used to identify 300 to 400 different compositions and origins of obsidian in the Western Hemisphere. Moreover, the X-ray fluorescence spectrometer itself is sufficient to determine the origin of obsidian, so the handheld fluorescence spectrometer is undoubtedly an ideal analytical tool for this application. Under normal circumstances, Zn, Rb, Sr, Y, Zr, Nb, Ti, Mn, Fe and Ba are the key elements for determining the origin of obsidian.

glaze

Like metals, sulfur glass can also be remelted, so there is no absolute connection between the source of the glass and its original place of origin. However, elemental analysis can provide some important information on the details of when, where and how sulfur glass was manufactured, especially when various fluxes are used. Based on the elemental composition information, specific geographical environments and specific historical periods can often be determined. In addition, the identification of colorants, bleaches, light-blocking agents and clarifying agents is all helpful for determining the source. This is of great significance for the protection and preservation of glazed artworks.

Overview

The handheld fluorescence spectrometer adopts the new technology of X-ray tube and patented vacuum technology, which can analyze the elements covered from Mg to U. There is no need to consume expensive gas. The operation software based on the Windows system allows users to adjust the current and voltage, giving users more flexibility and better analysis accuracy, thereby obtaining the best analysis results.

Handheld fluorescence spectrometers are an ideal choice for analyzing materials such as ceramics, photographs, glass, obsidian, bronze, and brass. It can not only meet the precise analysis requirements of the laboratory, but also be used for rapid and accurate analysis on site. Therefore, whether for on-site archaeological evidence or the protection of artworks, it can provide strong technical support.

The significance of elemental analysis for artwork appraisal and archaeological excavation

For the origin and structural identification of some unearthed objects from archaeological excavations and historical relics, it is first necessary to understand their elemental composition. Especially when identifying whether certain artworks are genuine or counterfeits, elemental analysis is often of great significance. Therefore, recently, elemental analysis has also been increasingly applied in the protection of cultural relics.

Iii. Conclusion

With the development of science and technology, inorganic material testing technology has been continuously applied in the research of ancient ceramics and archaeology. Promoting the development of inorganic material testing technology is of extremely important significance for advancing archaeological research in our country. In recent years, X-ray fluorescence spectrometry analysis and energy dispersive X-ray fluorescence spectrometers have been widely applied in the research of ancient ceramics and even archaeology. Especially the energy dispersive X-ray fluorescence spectrometer (EDXRF), with its non-destructive analysis feature, is highly favored by researchers. Although there are still some deficiencies, with the advancement of technology, the shortcomings of inorganic testing technology can also be improved and it will be more deeply applied to the research of ancient ceramics.