Mystery of Centuries-Old 'Maya Blue' Wall Coloring Solved, Say Scientists

One of the mysteries of Mayan art has reportedly been discovered by researchers in Spain.

A team of scientists from the University of Valencia and the Polytechnic University of say they've revealed how people in ancient Mesoamerica created "Maya Blue," a durable pigment used for centuries on paintings and pottery.

The coloring, used by the Mayans and other Mesoamerican cultures to decorate palace walls, sculptures and pieces of pottery, is highly resistant to chemical and biological deterioration --- with centuries-old samples appearing to be virtually unchanged.

Scientists have long known the ingredients used to make Maya Blue include indigo, a plant dye, and a type of clay known as palygorskite. But, how artists combined and "cooked" the ingredients has remained unknown.

The researchers explained they were investigating the secret of the unknown chemical processes that bind the organic to the inorganic component and result in Maya Blue's permanence. That's when they stumbled onto a third --- unexpected --- ingredient.

"We detected a second pigment in the samples, dehydroindigo, which must have formed through oxidation of the indigo when it underwent exposure to the heat that is required to prepare Maya Blue," researcher Antonio Domenech said.

"Indigo is blue and dehydroindigo is yellow," he said, "therefore the presence of both pigments in variable proportions would justify the more or less greenish tone of Maya Blue...It is possible that the Maya knew how to obtain the desired hue by varying the preparation temperature, for example heating the mixture for more or less time or adding more or less wood to the fire."

Mesoamerica is a region and cultural area in the Americas that approximately stretches from central Mexico southward to Belize, Guatemala, El Salvador, Honduras, Nicaragua, and northern Costa Rica.

A number of pre-Columbian societies flourished in the region before the Spanish colonization of the Americas in the 15th and 16th centuries.