| Yaozhou kiln is located in Huangpu district of Tongchuan city in China’s Shaanxi province.Yaozhou kiln has been around through the Tang,Five dynasty,Song,Jin,Yuan and Ming dynasty.This kiln has been firing for more than 700 years and holds "China’s Northern Celadon Designation".Yaozhou kiln’s celadon is classified by sky-green ware from the Five dynasty,olive-green ware from Song dynasty,and moon-white ware from Jin dynasty.The Five dynasty sky-green ware is "mirror-like bright,paper-like thin and chime-like sound." The olive-green ware of Song dynasty is described as being "as clever as gold,and as exquisite as jade." This celadon created during the Song dynasty is superior to porcelain modified with carving and printing technology.The moon-white ware of Jin dynasty is known to be as smooth as grease,as warm as jade,and as elegant as the moon.Yaozhou celadon has unique charm,which attracts different levels of ancient ceramic researchers.At present,Yaozhou celadon has garnered many accomplishments in respect to firing technology,chemical composition analysis,and coloring mechanism research.This research study uses material physics,chemistry,and chromatic analysis to establish a multi-connected relationship between the outward appearance and microstructure of Yaozhou celadon.This analysis includes a discussion revealing the similarities and differences of celadon belonging to different time periods and different glaze color,as well as establishes a theoretical model using chromaticity(appearance),chemical(composition),and physical structure(phase separation)to be used in the research of Yaozhou celadon.At the same time,the theory of chromaticity is used to analyze the functional relationship between factors that affect color such as firing temperature,coloring elements,glaze thickness,and glaze color.The results of this study are as follows:(1)Photoelectron spectroscopy(XPS)and the Raman spectra were used to show that the peak area of both Fe2+and Fe3+found in the Five dynastysky-green ware were rather large.Not only was the Fe2+ ion content in the glaze layer higher than that of Fe3+,but the Raman spectrum’s Ip value was also higher.In addition,there was a small amount of residual quartz crystal found in the glaze layer,which indicates that the Five dynasty sky-green ware was fired under a strong,reduction atmosphere and high temperature.As a result,the glaze color is blue-green.The black-grey celadon is made of a solid solution of iron and titanium with a high content of mullite,which makes it not as transparent as the body.The solid solution of iron and titanium deepens the color of the body,which leads to a greater absorption of incident light,thus reducing the brightness(L*value)of the celadon.The refractive index of mullite is higher than that of quartz,cristobalite and glass phase,which enhances the diffraction and scattering of incident light and reduces the reflectivity of incident light.Therefore,the transmittance and brightness of the Five dynasty sky-green ware with a black-grey body are lower than celadon with a white body.Secondly,the content of TiO2,CaO and Fe2O3 in celadon samples fluctuated only in a small range,indicating that the raw materials of the Five dynasty black-grey celadon were stable,which is also one of the main reasons for the small change of L*,red and green a*,and yellow and blue b*values.(2)Song dynasty’s olive-green ware in Yaozhou kiln was found to have a weak glaze created from high temperatures.The content of Fe2+ and Fe3+ ions in the glaze layer of celadon samples was relatively low,which indicates a weak-reduction firing atmosphere,and is also the direct cause for the yellowish-green glaze color.The results show that the Ip value of the samples is high,and the difference in Ip values among different samples is small,which indicates that the olive-green ware’s firing temperature is high and the firing technology was both steady and advanced.Song dynasty’s olive-green glaze was found to have a low content of crystals and bubbles,which led to the slight scattering of incident light,and as a result reduced the opacity of the glaze layer.The high content of glass phase in the glaze layer is the main reason for the glaze layer’s strong transmittance.(3)Microstructure analysis shows that the relatively thick glaze layer of Jin dynasty moon-white ware contains more crystals and small,dense bubbles.The refractive index of crystals and bubbles is different from the refractive index of glass phase in the glaze layer,which results in heavy scattering of incident light when it permeates the glaze layer.These characteristics also increase the opacification of the glaze layer and weaken the color rendering effect of the Fe ion,which is an important reason as to why the content of ferric oxide in the moon-white glaze is not low,but the color is still lighter.The fluctuation in the ratio between Fe2+ and Fe3+ ions in the moon-white glaze is minimal,and as a result,the glaze surface values of L*,a*and b*is also minimal,which indicates that the firing technology of this glaze was also rather advanced.(4)According to the calculation results of the discrimination coefficient of calcium glaze found in Song dynasty olive-green ware,Five dynasty sky-green ware and Jin dynasty moon-white ware,all three belong to the calcium glaze series.The microstructure analysis showed that the Five dynasty sky-green glaze and Jin dynasty moon-white glaze are both formed by Bragg scattering(amorphous color structure),which has a certain contribution to the appearance of color.However,the structural color of the moon-white glaze contributes to opacification rather than a blue-green color.The results showed that both the chemical color and amorphous color structure of the Fe element exist in Yaozhou celadon glaze.In addition,there is an obvious reaction in the intermediate layer between the celadon body and the celadon glaze,which can reduce the absorption of incident light in the glaze layer,improve the L*value of the glaze surface,have a better covering effect on the dark,thick body of the celadon,and enhance both the natural look and feel of the glaze color and the feeling associated with the soft external aesthetic.(5)Based on the longitudinal systematic analysis of the different color characteristics of the Five dynastie sky-green ware,Song dynasty olive-green ware and Jin dynasty moon-white ware,the theoretical model of "chromaticity(appearance)chemical(composition)+physical structure(phase separation)" is established using the basis of chromaticity,material physics,chemistry,laboratory science,and technological archaeology,which systematically explains the coloration mechanism of celadon glaze.The differences and similarities in the appearance of celadon glaze were quantitatively analyzed by using L*,a*,b*and other parameters of colorimetry.The chemical composition and phase separation of celadon glaze were analyzed by using their chemical and physical structures,respectively.Celadon’s apparent fundamental characteristics were systematically and comprehensively analyzed from the perspective of ion and structural color.(6)By analyzing the R,G and B values of the three primary colors found in the ancient celadon glaze,it can be concluded that the naming system of the traditional celadon glaze color is rather ambiguous or wrong.Based on the theory of chromatics,there exists a functional relationship between celadon,its firing temperature,Fe2O3 content,and glaze thickness even under different conditions such as firing atmosphere,kiln type and glaze form.The actual experimental results show that there is not only one functional relationship between them,but rather multiple function relationships. |
