What pigment could be used for ship maintenance, art, agriculture, medicine, and cosmetics? In the Greco-Roman world, the multi-use ocher pigment called Miltos filled all these roles. The powerful fiery hue of the pigment livened up classical wall paintings. And it was also used mark sheep…and stain tardy Assembly attendants in ancient Athens.

This wide variety of applications has led scientists to wonder why it was used so prolifically. One possible explanation is that miltos had different geochemical and microbiological properties depending on where it was mined, leading to a variety of possible forms, each ideal for a different purpose. It’s also worth noting that ocher (also spelled ochre) has been used by humans for hundreds of thousands of years.

Origin of Ocher and its Use

Ocher is a type of earth-based pigment composed primarily of iron oxides. Although it is commonly thought of as being red, yellow ocher is also found. Yellow ocher can be made red by causing changes to the hydration and oxidation of its minerals.

Three different ochre pigments. (Marco Almbauer/ CC BY SA 3.0 )

Blombos Cave in South Africa is the location of a 100,000-year-old archaeological site that shows signs of ocher being used a pigment. It also appears that the inhabitants etched abstract designs into pieces of ocher, creating some of the oldest artwork. This represents some of the earliest evidence for the use of ocher as a pigment by humans, though it also has been suggested that it was in use even earlier, possibly 300,000 years ago.

Miltos in Classical Antiquity

By classical times, a type of red ochre had come to be called miltos. Miltos in the ancient world came primarily from three locations, the Greek islands of Kea and Lemnos, and Cappadocia in modern Turkey. Miltos was also considered to have different uses depending on the source from which it was derived. Miltos from Kea was supposed to be effective in maintaining ships, for example. There was also some miltos that had medicinal purposes. Some forms of miltos were even used as fertilizer.

Black-figure terracotta vessel depicting an ancient Greek ship. On the bow, the apotropaic ophthalmos (eye) and the ram (shaped as a wild boar). Some types of miltos were said to be effective in maintaining ships. ( CC0)

This prolific application of miltos has fascinated archaeologists and historians who have wondered why it had so many uses. A recent study suggests that it might have had to do with the differing geochemistry and microbiology of each location where miltos is found.

A team led by University of Glasgow scientist, Effie Photos-Jones, investigated the properties of samples from Kea and Lemnos, but not from Turkey. They found interesting differences.

Miltos from Kea, for example, was found to be high in lead content. The lead in the Kean miltos could potentially disrupt the build-up of slime from micro-organisms on seafaring vessels. This is important because this slime can allow larger organisms, such as barnacles, to grow on the outside of a ship, resulting in the fouling of the ship’s hull. This can cause the ship to not move as fast, among other things. In this way, applying lead-rich miltos paint to the hull of a ship could inhibit biotic growth, preventing fouling. This may have been why miltos from Kea was prized in Athens since it could be used in the maintenance of ships.

Miltos samples from Kea and Lemnos. ( Photos-Jones et al. )

Miltos from Lemnos was found to have traces of titanium dioxide - an effective anti-bacterial agent. This may explain why miltos was also used to treat wounds and diseases. It could inhibit the growth of bacterial infections.

Additionally, it was found that some miltos has microbial communities which are connected to the fixing of nitrogen in soils in which iron plays a major role. The presence of these microbial communities would allow for miltos to be used as a fertilizer, explaining its use in agriculture.

In addition to naturally occurring miltos, there is also evidence that “fake” (or artificial) miltos could be produced by heating up yellow ocher so that it obtained a red color. This fake miltos was considered inferior, though it was still used as a pigment. One of the reasons that it was inferior may have been because the heating killed any pre-existing microbial communities that gave it unique properties.

An ancient Roman wall painting using yellow ocher. ( Public Domain )

Miltos, Red Ocher, and Human Evolution

Miltos is important not just because of its role in classical antiquity, but also because of its role in the history of the human species under the more general name, red ocher. Red ocher has been used for almost all human history and prehistory. The use of ocher as pigment represents one of the earliest technological advances of the human species. Also, the prolific use of miltos in the ancient world shows that the substance has been used to advance human civilization on many fronts; including art , cosmetics, medicine, agriculture, and ship-building.

This pivotal role of red ocher in the early technological development of the human species makes miltos not just wonder dust for the ancient Mediterranean world but for the entire human race as well.

Top Image: Roman Painting - Villa dei Misteri, Pompeii, Italy. Miltos was used for yellow and sometimes red in many Greco-Roman paintings. Source: Public Domain

By Caleb Strom