New Clues to Mysterious, Ancient Maya Blue Recipe Revealed (Video)

Maya blue is an intensely blue paint that was once used in Mesoamerica for centuries. It can be found on everything from palace walls to sculptures to pieces of pottery that were created by the ancient Mayans. Yet the recipe to this highly-resistant pigment was lost over the years. Now, though, researchers have discovered new clues that may show exactly how this paint was created.

Why do researchers care about this paint in the first place? The mixture is highly-resistant, lasting for centuries. It could be used to color modern day materials or even to reveal new ways to bind organic and inorganic materials.

The dominant theory surrounding the pigment states that there is a single type of Maya blue that was prepared in a unique way so that the two components--indigo and palygorskite--were bound together within the paint. Indigo is the dye used for denim and is obtained from the Indigofera suffruticosa plant. Palygorskite, in contrast, is a type of clay that is characterized by its crystal structure full of internal channels.

The new study, though, seems to prove that there isn't one rendition of the pigment. Instead of a single type of paint, the new work proposes that there are several different variations of Maya blue.

"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," said Antonia Domenech, a UV researcher, in a press release. "Indigo is blue and dehydroindigo is yellow. It's 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."

By examining Maya blue, the researchers were able to determine that two stages occur when both components are heated to temperatures between 120 and 180 degrees Celsius. During the first stage, water evaporates from the palygorskite and the indigo binds to the clay. Part of the indigo oxidizes and forms dehydroindigo. In the second stage, the dye disperses through the channels of the clay.

The dye itself was used in ritual ceremonies as well as on palaces and buildings. Yet researchers believe that the composition and function of Maya blue could have varied through the centuries. In particular, the scientists recently found pigments that follow the same pattern of a plant dye combined with clay. In the form of greenish balls, they were probably used to plaster and decorate the walls of buildings.

"These materials were certainly not within the reach of the common people but they signal a more 'everyday' use of the pigments that would not have had to be restricted to ritual or ceremonial activities," said Domenech in a press release.

The findings are published in Microporous and Mesoporous Materials.

Want to see a video about Maya blue? Check it out here.