Tag Archives: dye

Archaeologists Discover Indigo Dye Residues on 34,000-Year-Old Grinding Tool in Georgia

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Researchers from CA ‘Foscari University have discovered Indigotin, a blue secondary compound also known as indigo, on a non-nanoparticle ground stone tool unearthed from the Zuziana Cave at the foot of the Caucasus in Georgia. Indigotin forms through reactions with atmospheric oxygen and natural glycoside precursors from leaves of the Isatis Tinctoria. This indicates that the plant was deliberately processed as far back as 34,000 years ago, despite its non-educational applications.

Five pebbles from Zugiana Cave, Georgia. Image credit: Longo et al., doi: 10.1371/journal.pone.0321262.

Modern humans first appeared in archaeological records approximately 300,000 years ago in Africa.

Much of the evidence regarding their cognitive and technical skills is derived from the limited existence of stone artifacts and the remains of animals, as these endure far longer in the archaeological record compared to plant materials.

As a result, Paleolithic narratives predominantly emphasize animal hunting and the production of stone tools.

The so-called “majority,” particularly plants that lack significant mentions, especially those increasingly shown to be utilized for food, cordage, weaving, and medicine, create incomplete accounts.

This underscores the need to identify and illustrate the roles of plants in an array of activities, many of which may still be undiscovered.

“It’s not solely about viewing plants as food resources; that’s common. We emphasize their involvement in complex processes. It possibly involves transforming perishable materials for use at various stages of Homo sapiens 34,000 years ago.”

“While the identification of elusive plant residues not typically highlighted in traditional research continually improves, our multi-analytical approach unveils fresh perspectives on the technical and cultural sophistication of Upper Paleolithic tools, designed to skillfully exploit the vast resources of plants and fully acknowledge their significance.”

In their investigation, researchers examined stone tools dating back 34,000 years, discovered in Zugiana Cave, Georgia.

They identified signs of mechanical processing of soft, wet materials consistent with plant matter such as leaves.

Employing an array of microscopic techniques (both optical and confocal), blue residues (occasionally fibrous) alongside starch grains were unexpectedly revealed.

These residues were particularly prevalent in the areas of the tools that displayed significant wear.

To ascertain the blue residues’ nature, scientists used advanced microscopy techniques, specifically Raman and FTIR spectroscopy.

These analyses confirmed the existence of indigotin chromophores in several samples.

“Once the molecules responsible for the blue coloration were identified, new questions arose. How and why were these residues associated with the tool’s working surface?” the author remarked.

They subsequently investigated the porosity of the stone, a crucial factor for trapping and retaining biological residues.

Both microscopic fragments of the archaeological tool and larger samples of experimental replicas underwent analysis using Micro-CT tomography.

This analysis confirmed the presence of pores capable of holding trace biological remnants.

Consequently, the team devised a series of replication experiments.

Initially, raw rock materials resembling those used by prehistoric inhabitants of Zuziana were sourced.

The pebbles were collected by Nino Jakeli from the Nikrisi River, located just beneath the cave.

Following this, controlled experiments were conducted, mechanically treating a range of plants, including fiber sources (such as bast fiber) and potentially indigotin-yielding species.

“We employed a rigorous approach to pollution control and biomolecular analysis to provide insights into contemporary human behaviors and the technical and ecological knowledge likely prioritized during the Upper Paleolithic era,” the researchers stated.

“Whether this plant remains serve medicinal purposes or have other uses presents a new perspective on the intriguing potential for diverse plant utilization.”

Survey results have been published online in the journal PLOS 1.

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L. Longo et al. 2025. Direct evidence of treatment of Isatis Tinctoria L., non-nutritional factories, 32-34,000 years ago. PLOS 1 20(5): E0321262; doi: 10.1371/journal.pone.0321262

Source: www.sci.news

For centuries, the Iron Age site functioned as a purple dye factory

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Stoneware with purple dye residue found at Tel Shiqmona, Israel

Maria Bukin/Shalvi et al. , 2025, Plos One, CC-By 4.0

For centuries, modern Israeli coastal settlements have been home to industrial scale production from marine snails of purple dye, one of the most precious commodities in the ancient world.

Known as Tyrian Purple, it was particularly sought to color wool fabrics, and was highly regarded by wealthy and powerful people in Iron Age Mediterranean society. However, up until now, direct evidence of large-scale production sites has been sparse.

From 1100 BC to about 900 BC, Tel Shiqmona was a small Phoenician fishing village, producing small scale purple dyes. Later, when the Kingdom of Israel began to expand, the site said it had “transformed from a fishing village into a fortified purple dye production centre. Golan Charvy At the University of Chicago.

During archaeological research at the site, Sharvi and his colleagues discovered the remains of dye-dyed debris used to treat the material. 176 artifacts related to the production of purple dyes were collected, including 135 purple dye items.

The dye secretes mucus to protect itself and to kill prey. “The secretion is initially a slightly greenish fluid that oxidizes upon exposure to air and gradually turns purple,” says Sharvi. “However, to convert it into a real dye (something that chemically binds to textiles), it must be processed into solution through a complex series of chemical steps.”

Researchers argue that Tel Shiqmona is the only site in the world with clear evidence of the large-scale production of purple dyes in specialized facilities for a long time.

However, there is no historical record linking the site to the dye, and little is known about the actual process used to manufacture it, Shalvi says.

After the Kingdom of Israel fell around 720 BC, the scale of dye production fell until the Assyrians took over the site and increased the process again. When the Babylonians conquered the area around 600 BC, dye production at Tel Shiqmona was abandoned.

“It was most industrial sites in the Iron Age, and there was no monumental architecture or any particular beauty or elegance,” says Sharvi. “I think it’s a very smelly place, especially in modern noses, as the production process has produced a terrible smell. I imagine wool fleece dyed in various shades that are dry on the outside and inside of the building.

Purple dyes have captivated people all over the world, he says, and it has been the subject of extensive research. “The relationship with elite classes and religious rituals has grown in cultural, symbolic and economic significance, far beyond its function as mere colour.”

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Source: www.newscientist.com

Dye used to visualize mouse organs by making them transparent

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The yellow food coloring tartrazine changes the speed at which light passes through tissue.

University of Texas at Dallas

Massaging common food coloring into the skin of a live mouse makes the animal’s tissue transparent, allowing researchers to see its blood vessels and organs working — a technique that may one day help doctors peer deeper into our bodies to diagnose diseases.

It’s not easy to see the internal environment of a live animal. If the animal is dead, we can get a better look by sectioning the tissue or using chemicals to remove proteins and fats. In live animals, some things can be seen with a scan or endoscopy, but to see live tissue, you often have to cut it up.

now, Wu Zhihao Researchers at the University of Texas at Dallas have been able to make mouse tissue transparent by rubbing the skin of live mice with the food dye tartrazine, also known as E102 or Yellow 5. When the skin absorbs the dye molecules, it changes the tissue’s refractive index – the speed at which light passes through the skin.

The dye allowed visualization of organs in living mice.

Zhihao Ou et al. 2024

The mice then became transparent, enabling the researchers to watch peristalsis, the muscular contractions that move food through the digestive tract, and to view blood vessels on the surface of the mouse brain.

To understand how this technology works, Oh says, think of carbonated water. Light passing through the liquid changes direction each time it goes from the water to the air bubbles and back again, Oh says. That means the light scatters in all directions and doesn’t penetrate the liquid as easily as it does flat air or water. Biological tissue behaves in a similar way because it contains not only a lot of water, but also other molecules like lipids and proteins, which typically have a higher refractive index than water.

Adding the dye brings the refractive index of water closer to that of lipids and other molecules in the tissue, scattering light less, “which means you can see deeper and probe deeper,” Ou says.

The dye can be washed off and does not appear to harm the rats.

The study gets to the heart of one of the biggest problems in microscopy, Christopher Rowlands “If you tried to see more than a millimetre away from the surface of the tissue, you couldn’t. It wasn’t possible before, and now all of a sudden you can,” he says. “Before you could only see a millimetre, now you can see a centimetre away, and that centimetre makes a huge difference in many applications.”

Rowlands says that tartrazine could potentially be toxic in large amounts if applied to the skin, but neurobiologists routinely stick probes and lenses into the brain and remove parts of the cortex, so using a dye that’s widely accepted as safe for ingestion on the skin would probably be less harmful, he says.

But while the technique makes skin more transparent, it won’t give doctors complete visibility inside a person’s body. “It’s not like Harry Potter’s invisibility cloak,” Rowlands says. “It will make the skin look more glassy than it should.” Even if the effect were to happen throughout the body, Rowlands says, doctors would still be able to see bones and specialized structures inside cells called organelles.

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Source: www.newscientist.com

Greek Island of Aegina reveals ancient workshop where 3,600-year-old purple dye was made

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Coloured dyes were essential commodities in the Mediterranean region during the Late Bronze Age.

Berger and his colleagues unearthed a purple dye factory at site K10 (marked in red) outside Colonna, Aegina, during the Bronze Age. Image courtesy of Berger others., doi: 10.1371/journal.pone.0304340.

of The small island of Aegina It is located in the middle of the Saronic Gulf, between Attica, the Peloponnese and the central Aegean Sea.

The island has played an important role in the cultural history of the Aegean for thousands of years.

From the Neolithic to the Byzantine period (6th millennium BC to the 10th century AD), Aegina's main settlement was located on a small, well-protected promontory on the northwest coast called Cape Colonna.

During the 2nd millennium BC, this densely built and heavily fortified settlement reached the height of its economic prosperity and culture.

Representative monuments, outstanding finds and rich tombs indicate an economically stable and complex social system integrated into inter-regional trade networks and emerging cultures in the Middle and Late Bronze Age Aegean.

in New paper In the journal PLoS OneDr. Lydia Berger from the Université Paris-Lodron de Salzburg and her colleagues describe the remains of a 16th century BC purple dye workshop at Aegina Colonna.

The existence of this workshop is inferred from three main pieces of evidence: purple pigment preserved on pottery shards believed to be remnants of dye containers, dyeing tools such as grinding stones and waste pits, and crushed shells of marine snails harvested for the pigment.

Analysis of the chemical composition of shells and pigments indicates that the workshop mainly produces Mediterranean snails. Murex striped dye (Hexagonal column trunk).

Excavations at the site also uncovered numerous burnt bones of young mammals, mainly piglets and lambs.

Archaeologists hypothesize that these may be the remains of animals that were ritually sacrificed as sacred offerings to protect the dye-producing areas. This practice is known from other cultural sites, but the exact relationship of these bones to dye production is not yet entirely clear.

The site provides valuable insight into the tools and processes of Mycenaean purple dye production.

Further investigations may reveal more information about the scale of dye production at Aegina Colonna, details of procedures at the site, and the use of this dye in regional trade.

“The discovery for the first time of a remarkably large amount of well-preserved pigment, a large amount of crushed mollusc shells and several functional installations allows detailed insights into the production of purple dye on the Greek island of Aegina around 3,600 years ago,” the researchers said.

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L. Burger others2024. More than just a colour: Archaeological, analytical and procedural aspects of Late Bronze Age purple dye production at Cape Colonna, Aegina. PLoS One 19(6):e0304340;doi:10.1371/journal.pone.0304340

Source: www.sci.news