Silk turned up on Sanxingdui’s 3,000-year-old bronze masks

Silk residue has been identified on 94 bronze objects from the sacrificial pits at Sanxingdui, among them a large bronze mask carrying three patches of fabric around its right eyebrow and eye. The finding comes from a paper in the journal Antiquity by Jianbo Guo of the Sichuan Provincial Institute of Cultural Relics and Archaeology and four co-authors. Silk now sits alongside bronze, jade and ivory among the materials the Late Shang people of ancient Shu set aside for ritual burial.

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Sanxingdui lies in Sichuan province in southwestern China, and the pits in question date to the Late Shang period, roughly 1300 to 1046 BCE. The research team examined textile residues on 101 artefacts from Pits K2 to K8. Silk residue appeared on 94 bronzes spread across 28 object categories, and also on gold foil, jade implements and ivory fragments. From the combined evidence the authors argue that silk was used on a large scale at the site, which places ancient Shu inside the wider history of early Chinese silk. Pits K3 and K7 are the two the paper discusses most, and excavations between 2019 and 2022 uncovered six additional pits at the site beyond the original two found in the 1980s.

Electron microscopy and infrared spectroscopy as the silk test

The identification rests on instruments rather than on the eye. According to the Antiquity paper, scanning electron microscopy on three samples showed smooth fibres about 10 micrometres across with triangular cross-sections, a profile that matches natural mulberry silk. Fourier-transform infrared spectroscopy on four archaeological samples, run beside a modern Bombyx mori silk reference, showed the absorption bands that mark a protein-based fibre. The authors then excluded animal hair because of the tight weave and smooth fibre surface seen under the microscope, and optical microscopy supplied the weave structure, density and state of preservation. One Pit K7 sample, K7QS-T-254, had a hollow fibre structure, which the authors attribute to copper mineralisation from the surrounding bronze and not to a different material.

The instrument work covered three samples under the electron microscope and four under infrared analysis. For the wider count of 94 bronzes, the abstract describes a combined case built from fibre traits, colour, weave structure and excavation context.

Red ochre, a red dye and layered cloth on the bronzes

The silk was coloured. Arkeonews, reporting on the study, describes red ochre on the fibres, calcite that may come from a surface coating, and a deep-red organic dye that penetrated the threads; the plant source of the dye was not identified. Most fragments are plain weave, with some evidence of more complex interlacing, and one fragment is an open, gauze-like structure. One bronze ornament carried up to five layers of textile, which the researchers read as deliberate placement. Bronze corrosion has mineralised some fibres, and some fragments are carbonised while others are well preserved.

The central object is mask K3QW:21 from Pit K3, a large bronze mask with three silk areas around the right eyebrow and eye. An animal mask, K3QW:86, also carried residue, as did a circular bronze ornament, two pieces of gold foil, a jade ge blade and an ivory fragment from Pit K8. The paper’s title, Silk and sacrifice at Sanxingdui, frames the textiles as part of the offering system rather than as everyday cloth.

The pits are among the best known in Chinese archaeology. A China Daily fact page records that the 1980s excavations of Pits 1 and 2 produced human face masks with protruding pupils, while Pits 3 to 8, found in 2019 and 2020, have yielded about 500 further artifacts including gold masks, ivory, jade and textiles. CNN reported that a gold mask recovered from the newer pits is more than 3,000 years old and thought to date from the late Shang dynasty, which ended in 1046 BCE, the same horizon as the 3,000-year-old bronze masks now shown to have worn silk.

Protective layer, wrapping or offering, still undecided

The authors say the silk could have been a protective layer, a wrapping or covering, or an offering, and they acknowledge the study cannot settle which function applied in every case. The origin of the cloth is unestablished too. Spindle whorls and other textile tools found at Sanxingdui may point to local production, but the paper stops short of saying the silk was made there. The team also speculated that silk could have carried writing; none was identified on the fragments studied.

Two numbers frame what remains unresolved: instrument results exist for three electron-microscope samples and four infrared samples, against 101 objects in the full set, and the plant behind the red dye is still unnamed. Lu Yang of Northwest University’s School of Cultural Heritage is the paper’s corresponding author. The other co-authors are Ruochen Ge of the same school, Qiutong Cai of the Sanxingdui Museum and Jingyu Tian of Yunnan University’s School of History and Archives, so the identification carries the names of the institute that excavated the pits and the museum that holds the finds.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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