Maya Blue: Unlocking the Mysteries of an Ancient Pigment

21st Feb 2025

Mexicolore contributor Dean E. Arnold

We are sincerely grateful to Dr. Dean E. Arnold for writing specially for us this intriguing introduction to the mysterious and unique pigment known as Maya Blue. Dr. Arnold has published extensively about the Maya potters and their craft in Ticul, Yucatan from data collected during his twelve visits over a period of 43 years (1965-2008). He is currently Adjunct Curator of Anthropology at the Field Museum and Professor of Anthropology Emeritus at Wheaton College (Illinois).

Maya Blue is a beautiful blue pigment used by the ancient Maya from the Late Preclassic Period (300 BC - 300 AD) up into the Colonial Period (pic 1). It mimics the color of the azure sky and the turquoise of the Caribbean that one sees from the Maya Rivera - that incomparable strip of coastline that stretches along the east side of the Yucatán Peninsula.
Maya Blue was the color of sacrifice for the ancient Maya, and they painted human sacrifices, sculpture, pottery, murals, and codices with it (pic 2). Symbolizing the rain god Chaak, among other meanings, the Maya employed it largely during the Late Classic, Terminal Classic, and Postclassic Periods. After the Spanish Conquest, it occurred on murals in churches and convents, and there is some evidence that it was used up into the 19th century.

Before the modern rush of tourism forced the closure of many parts of archaeological sites, one could still see Maya Blue on the sculpture and murals that still retained its rich blue color unchanged from the time of its creation. One archaeological site that evinces its persistent color is Chichén Itzá, an ancient Maya city on the northern Yucatán Peninsula (pic 3). As visitors walk northward from the great Pyramid of Kukulkan to a sinkhole called the ‘Sacred Well’, they encounter a low pyramidal structure known as the Venus Platform (pic 4). Careful observers will note that the low relief sculpture on it still retains some of its ancient paint. Looking closely, they can see the remains of a blue pigment, still clinging to the crumbling limestone, yet with a richness of color unfaded after a millennium of exposure to the harsh tropical sun, torrential downpours, and hurricanes that have plagued Yucatán for centuries. Although much of the pigment has disappeared because of the erosion of the limestone underneath it, that which remains still retains its bright blue color.

The most prominent uses of Maya Blue at Chichén Itzá lie hidden within the restricted areas of the site. In the 1960s, visitors still had access to some of these areas. One such area was the Temple of the Warriors where the pigment was first discovered (pic 5). As I strolled among the columns outside of this structure, I could see tiny remnants of Maya Blue on the low relief figures. In 1970, I was able to enter the chamber under the Temple and saw the blue on the headdresses on the warrior figures on the columns (pic 6) and on the murals on the wall. It was here that chemist H. E. Merwin first noted the unique characteristics of Maya Blue. Similarly, after the short, but steep a climb to the Upper Temple of the Jaguar located on top of the East wall of the ball court, a mural inside the temple also shows the pigment (pic 7). All of these areas are now closed to visitors, but one can still see Maya Blue on the low relief sculpture in the interior of the Lower Temple of the Jaguar (pic 8).

Apart from its incredible blue color, Maya Blue does not fall into a class of just any blue pigment. Rather, it is unique in the ancient world both physically and chemically. Most pigments usually consist of an organic material derived from a plant, tree, or insect (like cochineal), are made up of an inorganic mineral (or minerals) such as azurite or lapis lazuli, or are inorganic glazes with metallic ions, such as copper, that color them blue or green.
Unlike other ancient pigments, however, Maya Blue is not organic or inorganic. It is a unique human-created chemical hybrid of an inorganic clay mineral, palygorskite (and/or with another clay mineral, sepiolite) and indigo, an ancient dye used throughout Middle and South America before the Spanish Conquest.

Most remarkable about Maya Blue is its unusual characteristics. Maya Blue is quite different from either indigo or the clay mineral to which it binds. Unlike its constituent, indigo, Maya Blue does not fade over time. As anyone who owns blue jeans knows, the indigo dye in them fades with use and repeated washing. By way of contrast, Maya Blue remains vivid even after centuries in one of the world’s most hostile climates, the tropical forests of southern Mexico and Guatemala. Furthermore, solutions of acids and alkalines do not diminish its color. Rather, its color dissipates only with heat over 325 degrees C. unlike indigo.
During the last 60 years, the uniqueness of Maya Blue and especially its unique stability has simulated great interest among chemists and material scientists who have written many hundreds, if not thousands, of pages to explain its unusual properties and discover how the Maya created it.

Their studies have shown that Maya Blue is a unique artificial nano-structured hybrid material probably created by grinding wet palygorskite with the leaves of the indigo plant (Indigofera suffruticosa), or a leachate from them, and then heating the mixture to a temperature of 100-150 degrees C. Now considered the first ever such hybrid pigment in antiquity, its exceptional stability has inspired much research for designing new such materials.
Some analysts have replicated Maya Blue in the laboratory or used the techniques of indigo extraction similar to those used during the Mexican Colonial Period when the dye was commercially produced for export. Making the pigment experimentally in the laboratory or the field, or replicating the historical processes of producing indigo, however, does not mean that the ancient Maya actually used these methods.

Many aspects of Maya Blue, especially how the ancient Maya actually made it, have remained a mystery since it was first discovered in 1931. Research with my Field Museum colleagues, however, has already revealed one solution to this mystery. It began with my discovery of a bowl of copal incense with a blue material on it in the collection in the Field Museum (pic 9).
When I first saw the bowl, I got very excited. When I upended the bowl and removed the copal from it, I noticed splotches of a white and blue material on the underside of the copal. With magnification, it looked like the palygorskite that the modern Maya potters called ‘white earth’ that I knew from forty years of studying pottery making in Ticul, Yucatán. Particularly, it was identical to the ‘white earth’ I knew from the large mine for ‘white earth’ (sak lu’um) in Sacalum, Yucatán.

My interpretation of the role of copal in making Maya Blue came from my observations and research decades previously. I had seen balls of copal incense with blue on them in a display of a reconstructed burial in the site museum at the Maya site of Tikal in Guatemala. Likewise, I had witnessed the burning of copal incense used in contemporary Maya ceremonies at religious sites in highland Guatemala and had seen its use among the contemporary Maya in Yucatán during the Day of the Dead ceremonies (pic 10). I also recalled experimental research with indigo and palygorskite that revealed that heat was necessary to create the pigment, and that very little (.05 -3.0%) indigo was necessary to make the pigment. Critical to these recollections was my memory of a small monograph published in 1969 about Maya Blue found in an Aztec incense burner recovered from the market in the former Aztec capital of Tenochtitlán. The author suggested that the Aztecs might have made the pigment by burning incense.

This bowl was recovered more than a century ago from the Sacred Well, a sinkhole (aka ‘cenote’) at the ancient Maya site of Chichén Itzá (pic 11). From the writings of sixteenth century priest, Diego de Landa, the Sacred Well was the site of offerings to the rain god Chaak and included jade, pottery, and human sacrifices. Edward H. Thompson dredged the Sacred Well from 1896 – 1910, and the vast collection of the objects recovered ended up at the Peabody Museum at Harvard. Published descriptions of these objects revealed that most of the copal offerings had blue on them. Out of the dozens of bowls with copal, the Peabody Museum traded this particular vessel to the Field Museum in 1932 when eminent Maya archaeologist, J. E. S. Thompson, was Curator of Anthropology.
After examining this bowl, I suggested to Field Museum curator Ryan Williams that the white and blue materials on the incense should be analyzed, and he engaged a team of Field Museum scientists to study and test those materials to see if they were palygorskite and indigo. Their analysis of the material on the copal revealed that the Maya Blue retained the structure of palygorskite, and that indigo was also present. Furthermore, the bowl with the copal offering represented remnants from the creation of Maya Blue that had been interrupted by throwing the bowl with its burning contents into the Sacred Cenote as an offering to the rain god, likely as an appeal for rain in response to the devasting droughts of the Terminal Classic and Postclassic Periods.

Although heating a mixture of palygorskite and indigo with copal incense was one way to create Maya Blue, but it probably was not a practical method for preparing a substantial amount of the pigment for painting pottery, murals, and sculpture because, among other reasons, it produced an insufficient amount of the pigment needed for these objects and that required to paint human bodies and their altars for sacrifice. Furthermore, the question remains about how the Maya separated the blue pigment from the copal and palygorskite to use for other these purposes. So, the ancient Maya must have used another method of preparation. But what was it?
Now, I have discovered an additional process of how the ancient Maya made the pigment. The roots of this discovery occurred sixty years ago with my discovery that the modern Maya recognized one of the constituents of Maya Blue, the clay mineral palygorskite, as a cultural category (pic 12). The modern Maya call this material ‘white earth’ (sak lu’um), a white, hard, and rock-like substance that becomes plastic with water. Because of its rock-like quality, this ‘white earth’ must be ground in order to make Maya Blue.

Grinding ‘white earth’, however, is not just a physical process that makes it easier to use, but it is a key procedure to prepare any stable palygorskite-organic hybrid such as Maya Blue. Grinding increases the surface area of the clay so that the indigo molecule and its precursors in its leaves can bind to the clay more completely. In an experiment using methylene blue, Zhang et al. showed that the amount of time used to grind the palygorskite improved the dispersion of its crystal bundles, facilitated the release of the water molecules from its channels, and intensified the interaction between the clay structure and the methylene blue dye. Increased grinding time thus greatly enhanced the formation of a stable organic-inorganic hybrid material. Another experiment by Zhang et al. revealed that grinding wet palygorskite better preserved its structure and improved the stability of the resulting hybrid more than grinding the dry clay.

The necessity of grinding the palygorskite before preparing Maya Blue raises the question about how the Maya did it. What kind of tools did they use? As I thought about this question, I remembered a grater bowl with Maya Blue in the Field Museum’s collection that I discovered during my survey of the objects there (pic 13). In making this bowl, the potter scored thick incisions in the bottom of the bowl, but why? The bowl was obviously used to grind something. But what was it?
One clue about the bowl’s use comes from closely examining the Maya Blue on it. The pigment was not a slip, but rather covers most of the red slip, and is sloppily applied. A second clue comes from a white residue visible in, and along, some of the incisions, and as specks and splotches elsewhere inside the vessel. This white residue appears to be the remains of palygorskite used in preparation of Maya Blue. Because palygorskite is very hard and difficult to grind dry, it appears that it was ground when it was wet because it stuck to the inside of the vessel in and around the incisions.

Heating is critical to create Maya Blue to ensure the stability of its color. Since the vessel is a tripod bowl, the ancient Maya probably placed it over a small fire to heat the mixture of the crushed palygorskite and the extract from the crushed leaves of the indigo plant. Then, after the pigment cooled, it was scraped out, leaving some of the pigment around the interior along with remnants of palygorskite. The presence of Maya Blue in the interior of the bowl and the evidence of horizontal wiping or scraping of the white material and the Maya Blue indicates that its presence in the bowl likely resulted from creating Maya Blue and not the result of decoration by the potter who made it.
This bowl is one of twelve red-slipped Postclassic tripod bowls excavated from El Osario at Chichén Itzá by Edward. H. Thompson in the late 19th century. To evaluate whether these bowls were used to create Maya Blue, they were compared visually to the emptied bowl with copal and Maya Blue that came from the Sacred Cenote. Analysis of the Maya Blue on the copal in this bowl revealed that it was made with palygorskite. When the copal was removed, the interior of the bowl revealed a white substance that was likely the palygorskite used to make the pigment.

In order to determine whether all these twelve bowls from El Osario were used to make Maya Blue, I used three criteria. First, I looked for the presence of Maya Blue on them. Indeed, most of the bowls showed evidence of Maya Blue. Second, like the bowl emptied of its copal mentioned above, I looked for the presence of a white residue on these bowls. This residue probably would be palygorskite. Indeed, a white residue occurred on all of them. On some, it appeared only as splotches that were sometimes exceedingly small (pic 14). Third, I compared the interior walls of each vessel with its interior base by looking for contrasts of color, and the relative amount of the red slip remaining from probable use-wear. All of the bowls without incisions showed a diminished red slip on their internal bases. In all of them, the slip was lighter in color showing some wear, was pitted in some cases, or showed evidence of scratches or stirring marks. The wear and discoloring of the red slip on the interior base of all the bowls revealed evidence of grinding, mixing, and heating. On the three bowls with incisions in their base, the slip was largely gone, with some indication of wear around the grooves. This absence indicates that grinding or stirring occurred in these bowls (pic 15).

Finally, microscopic examination of the twelve bowls using a Leica M80 Microscope revealed tiny carbonized or uncarbonized plant stems both on the interior and exterior bases of ten of them. The interior bases of seven revealed the remains of tiny, carbonized stems of plant materials. The area around the incisions of one bowl showed heavy grinding. A pitted surface with black carbonized material in the pits appeared in four bowls.
The observation of residues and use wear on these twelve bowls revealed various combinations of Maya Blue, probable palygorskite, and tiny carbonized and uncarbonized plant stems. They indicate that the ancient Maya produced their unusual pigment by grinding and mixing wet palygorskite with the leaves of the indigo plant. Further, the lighter color of the interior base, and the removal of some of the red slip on the base of the vessel indicates that mixture probably was heated by burning charcoal or copal under the bowl to stabilize the blue color. These observations corroborate the conclusion from experimental data that the indigo and palygorskite mixture must be heated to achieve its unusual stability. After cooling, the pigment was wiped out to use for other purposes such as painting pottery, sculpture, murals, and human offerings before they were dispatched, a practice described by Diego de Landa in the sixteenth century. Consequently, these observations provide evidence that this method was another way that the ancient Maya used to create Maya Blue.

The link that I surmised between the palygorskite in the bowl from the Sacred Well and the ‘white earth’ from the village of Sacalum led to another research question: From where did the palygorskite in the Maya Blue in the bowl come? I had collected many samples of palygorskite (‘white earth’) from many sites in Yucatán during my twelve trips there since 1965. Clay mineralogist Bruce F. Bohor formerly of the Illinois Geological Survey and more recently from the United States Geological Survey had identified them as palygorskite. Another team of scientists under my direction investigated whether various sources of palygorskite in Yucatán had different compositions, a necessary condition to determine a specific source location. The results of these analyses indicated that the patterning of certain trace elements could indeed reveal whether a sample of palygorskite came from Sacalum, Ticul, or elsewhere.

The next step of investigation looked to discovering whether the palygorskite in the Maya Blue from the Field Museum’s collection matched the known sources of palygorskite. This step involved comparing the trace elements in the pigment with the roughly 180 samples of palygorskite that I and clay mineralogist, Bruce F. Bohor, had collected in Yucatán over a period of 43 years. Field museum staff (curator Gary Feinman, collections manager, Chris Phillip, Laure Dussubieux, the director of the Element Analysis Facility) assisted in selecting samples from the collection that had portions large enough for analysis. In addition, Hector Neff of the IRMES facility at University of California, Long Beach added some samples of Maya Blue from the ancient Maya site of Palenque. The six samples of Maya Blue from the Field Museum’s collection principally came from the Grave of the High Priest (now called El Osario) at Chichén Itzá, a mortuary monument also excavated in the late 19th century by Edward H. Thompson, and from the bowl (described above) recovered from the Sacred Cenote at the site.

The results of the analyses by the Field Museum team and another team from the University of California Long Beach revealed that some of the samples of Maya Blue from the Osario came from the mine of ‘white earth’ (palygorskite) in the town of Sacalum. Samples of the pigment from Palenque were also attributed to Sacalum, to a possible unknown source, and to a location near Ticul used by local potters to mine a tempering material for their pottery. These analyses lay the groundwork for assessing the spread of palygorskite and/or Maya Blue throughout Mesoamerica by means of trade or exchange, even though the transfer of the technology for making the pigment was also likely.
The research on the process of making Maya Blue and its sources continues at the Field Museum. The white material in these bowls will be analyzed by X-ray diffraction to determine if it is palygorskite. Scanning Electronic Microscopy will find out if the white material shows the distinctive fibrous quality of palygorskite. Furthermore, Laser Ablated Mass Spectroscopy will be used to discover the source of this white material by comparing its trace elements with the trace element database of palygorskite samples already collected from known locations in Yucatán.

It is ironic that although the ancient Maya used Maya Blue widely for more than seventeen centuries, modern scientists still have much to learn about it. Archaeologists, for example, have devoted little attention to the pigment. My book Maya Blue: Unlocking the Mystery of an Ancient Pigment, distilled above, aims to help fill this gap. It documents the story of Maya Blue from its original discovery, and summarizes some of the research about its composition, meaning, and creation in a cultural and environmental context. Many others have studied various aspects of the pigment, but this work brings together what I have learned about the pigment, how it was made, how it was used, and how it was spread throughout Mesoamerica from an anthropological perspective.

Our ‘Ode to Maya Blue’:-
In you go, indigo, to make Maya Blue -
Palygorskite clay, and add some water too.
Heat it and the organic parts in this ancient mix
Combine with the inorganic in a pioneering fix.
It’s a special hybrid! In practice what this means -
It lasts! It’s far more stable than the dye in your blue jeans...