光纤反射光谱技术无损鉴别天然染料

Nondestructive identification of natural dyes by fiber optic reflectance spectroscopy

通过鉴别古代服饰中的染料能够为纺织品文物的色彩复原和颜色保护提供理论依据。文章采用光纤反射光谱技术获得8种天然染料(红花、苏木、栀子、姜黄、槐米、黄栌、黄檗和靛青)的吸收光谱图,对每一种染料的吸收光谱作出相应的一阶导数图。通过对比明代红纱地绣仙鹤方补袍与染料参考品的吸收光谱图和一阶导数图以鉴别文物使用的天然染料种类。结果表明,明代红纱地绣仙鹤方补袍中的红色纱线由红花和黄檗染制,黄色纱线由槐米染制,蓝色纱线由靛青染制,绿色纱线为槐米和靛青套染获得。

Most of the natural dyes used in ancient times were plant dyes,with rich varieties,and the dyed colors were also very rich.In the Ming Dynasty,the ancients had mastered the basic process of dyeing,and the techniques of direct dyeing and mordant dyeing,as well as single dyeing and mixed dyeing,were also very mature.Various kinds of natural dyes and their dyeing methods were recorded in ancient books such as Heavenly Creations and Compendium of Materia Medica.For example,Heavenly Creations recorded the dyeing methods for colors such as bean green,wood red and purple,while Compendium of Materia Medica recorded that gardenia,turmeric,pagoda tree flower,young fustic and amur-cork tree alone can be used for yellow dyeing.Identifying the dyes in cultural relics can provide a theoretical basis for color recovery and color protection of textile relics,and promote the understanding of clothing quality and color standards at that time.To identify the natural dyes used in mandarin square robe with cranes embroidered on the red yarn ground in the Ming Dynasty,and to identify the botanical origin of the dyes,we used a non-destructive testing method,fiber-optic reflectance spectroscopy,to identify the dyes in the cultural relic.First,eight dyes(safflower,sappanwood,gardenia,turmeric,pagoda tree flower,young fustic,amur-cork tree,and indigo)frequently mentioned in ancient books of the Ming Dynasty were used to prepare reference materials for dyeing silk.Then,the absorption spectra of the dyed silk reference materials were obtained by using FORS technology,and the corresponding first-order derivative eigenvalues were made to obtain the maximum absorption wavelengths and first-order derivative eigenvalue positions in the spectra.Finally,we identified the dyes by comparing the differences in the absorption spectra and first-order derivative eigenvalues obtained from dyed silk reference materials and mandarin square robe with cranes embroidered on the red yarn ground in the Ming Dynasty.We detailed the maximum value of the absorption spectrogram of each dye,and took the first-order derivative of the curve in the spectrogram to obtain the first-order derivative eigenvalue.The maximum visible light absorption wavelength of safflower was located at 521 nm,and the first-order derivative eigenvalues were at 478 nm and 563 nm.The maximum absorption wavelengths of amur-cork tree were located at 346 nm and 429 nm,and the first-order derivative eigenvalues were located near 377 nm and 478 nm.The maximum absorption wavelengths of pagoda tree flower were located at 330 nm and 421 nm,and the first-order derivative eigenvalue was located near 473 nm.The maximum absorption wavelength of visible light of indigo was located near 634 nm,and the first-order derivative eigenvalue was located at 694 nm.By comparing the absorption spectra and first-order derivative diagrams of this cultural relic with those of the dyed silk reference materials,we identified that the red yarn was dyed by amur-cork tree and safflower,the yellow yarn was dyed by pagoda tree flower,the blue yarn was dyed by indigo dyes,and the green yarn was made by mixed dyeing of pagoda tree flower and indigo dyes.The dyeing techniques of the Ming Dynasty were highly sophisticated,with a wide variety of dyes,comprehensive chromatograms,and harmonious color matching,all of which demonstrated the wisdom of the ancient workers and the craftsmanship of the time.This study confirms that the dyes used in this cultural relic are consistent with the dyes of safflower,amur-cork tree,pagoda tree flower,and indigo recorded in ancient books such as Heavenly Creations,which can help to restore the historical appearance,protect the cultural heritage,and promote the research of dyes.