光导纤维反射光谱技术在彩绘文物颜料无损分析鉴定中的应用

文物颜料成分分析鉴定是文物材质分析和文物保护工作的重要内容.利用白行研制的光导纤维反射光谱仪对唐代彩绘陶器和壁画上的颜料成分进行了无损分析鉴定,通过比较彩绘文物颜料和标准颜料的反射光谱曲线的形状以及特征峰或一阶导数峰来完成颜料的鉴定工作.光导纤维反射光谱法鉴定出西安市唐代彩绘文物l.样品墓葬壁画上的深红色颜料是纯度较高的土红;2#样品陶器残片上的绿色颜料为石绿;3#样品陶缸残片上的橙红色和朱红色颜料分别是由大量铅丹和微量土红及大量朱砂和微量土红的混合物所组成.采用x射线荧光分析法进行验证,实验结果表明光导纤维反射光谱技术鉴定彩绘文物颜料成分的结果是准确、可靠的,提供了一种文物颜料无损分析的简捷方法.

Nondestructive Analysis and Identification of Pigments on Colored Relics by Fiber Optic Reflectance Spectroscopy

Identifying pigments on colored relics is an important part of relic analysis and protection.In order to meet the special demands of protecting relics,taking into account the situation in China,we have refitted a domestic instrument to a fiber optics reflectance spectrophotometer with low price and good function to identify pigments without any damage.It consists of a tungsten lamp,a monochromator,an optical fiber,a shielding chamber,a photomultiplier tube,a reading meter,and a high voltage supply source.Through analysis of a great variety of Chinese ancient pigments,we have deduced three reflectance spectrum shapes of pigments,bell-shaped,s-shaped and oblique line-shaped.The blue or green pigments with bell-shaped spectra can be identified by the characteristic reflectance peak.The pigments with s-shaped spectra are usually red,yellow or brown.Although there are no characteristic reflectance peaks on the plots of the reflectance-wavelength,there is a peak in the first derivative(D') here.Then, the related pigments of this sort can be analyzed and identified with their derivative peaks.For the pigments with oblique line-shaped spectra,their reflectance and first derivative spectra are nearly linear and there are no peaks.The related pigments are usually white,black or gray.With our self-made fiber optics reflectance spectrophotometer,we analyzed the composition of pigments on colored pottery figurines and frescoes of Tang dynasty tombs in Xi'an by comparing their reflectance spectroscopic curves and characteristic reflectance peaks or first derivative peaks with those of standard pigments.The deep red pigment in sample 1#,the green pigment in sample 2#,and the orange and deep red pigments in sample 3# have been identified to be hematite with high purity,malachite and the mixtures of cinnabar/red lead and a little hematite,respectively.It has been indicated that the analytical results of relic pigments from this method are accurate and reliable,and verified by XRF analysis.Fiber optics reflectance spectroscopy is a new quick analytical technique to identify pigments on colored relics.