Tamil Nadu: Keeladi weavers used indigo to dye clothes, finds new study

CHENNAI: Sangam-age weavers used plant-based pigments such as indigo to dye clothes. That’s what an analysis of the organic compounds found at the Keeladi site has shown, indicating the existence of ancient textile dyeing units.

Through samples collected from pottery sherds, bricks and soil, researchers from Madurai Kamaraj University (MKU) found 14 distinct indigo-related compounds and anthraquinone molecules, which are the chemical basis of some of the oldest known textile dyes.


“Different indigo-related compounds identified at Keeladi suggest the use of the plant-based dye 2,000 years ago,” said professor G Kumaresan, head of the department of genetics, school of biological sciences, MKU.

‘Keeladi, an industrial centre’
The furnace-like structure, incorporating terracotta channels and ceramic vessels, suggests a specialized industrial installation that required controlled heating and careful management of liquids, archaeologists said.

“Anthraquinone-based dyes were previously identified in ancient Egyptian textiles and mummies, Roman fabrics, medieval European cloth, wall paintings, manuscripts, and dyed artefacts across Asia and Europe. Importantly, dye residues on cotton textiles from Indus Valley sites, such as Mohenjo-daro and Harappa, showed evidence of madder-based anthraquinone dyes,” Kumaresan said.

“Besides the archaeological findings, this study gives us the scientific proof that a textile dyeing unit functioned at Keeladi,” Professor K Rajan, academic and research adviser of TN department of archaeology, said.

He said the finding is consistent with the archaeological context, including channels, dyeing vats, artefacts like spindle whorls and bone points, as well as references in Sangam literature describing dyeing process and textile making in ancient TN.

“This shows Keeladi was not merely a residential settlement, but also an industrial centre where knowledge of chemistry, heat control, plant processing, and materials science was applied,” Rajan said.

Ancient genomics research team at Madurai Kamaraj University recently collected samples and processed them. The organic molecules were isolated and analysed using Gas ChromatographyMass Spectrometry (GC-MS), a technique that helps identify chemical compounds preserved in archaeological materials.Among the many organic molecules detected, anthraquinone, also known as anthracenedione, was significant, as it is known to be the chemical basis of some of the oldest known textile dyes.

Closely related molecules, like alizarin, purpurin, emodin, chrysophanol, and rhein, were frequently identified in archaeological textiles and dyed artefacts worldwide.

The most likely plant sources of these dyes include Indian Madder (Rubia species, also known as Chay root), Morinda, or Senna. “MKU genetics team is also working to detect ancient plant DNA traces from the associated soil samples, which may help identify the exact botanical source used at Keeladi,” Kumaresan said.

Notably, botanical surveys conducted by the Botanical Survey of India (BSI) document the natural occurrence of Indian Madder in nearby regions like the Alagar Hills (Madurai) and Piranmalai Hills (Sivaganga), further strengthening the local connection. Researchers said scientific investigations are on to identify the types of textiles or materials that were dyed and unearth the ancient textile technology.