The right mud: Studies in the mud-coating technique of Gambiered Guangdong silk

Gambiered Guangdong silk is a traditional cloth with two-tone colors, deeply rooted in China. Its coating technique has been included in the National Intangible Cultural Heritage List. In the unique coating process of the silk, river mud plays an important role but there has been very little research involving it. To gain insight into the characterization of the special mud, the usable mud with the unusable mud were compared with SEM-EDS and XRD. The results showed that Fe(II) was the main valence state of iron in the usable clay mud (nearly 90\%). Although the iron mineral particles constituted of akaganeite coated on the coated silk surface, akaganeite was not used as the original pigment because of its poor availability. The significant correlation between the Fe(II) content and textile lightness (L*(1)) (r = -0.82, p \textless 0.05), and sterilization test confirmed the role of Fe(II) in the coating process. Meanwhile, given the penetration of FeSO4 into the back side, it suggested that the solid and organic-binding phases of Fe(II) were the main forms of Fe. Moreover, there were no bacteria participating in the 1-h coating process but they importantly maintained the coating availability of the mud. In short, the right mud for coating Gambiered Guangdong silk need enough precipitated Fe(II) which could obtain from bacteria reducing Fe(III). This paper provided the scientific basis for the inheritance of the mud-coating technique of Gambiered Guangdong silk.