Saturday, January 11, 2014

Maya Blue


Used by the ancient -- and Colonial Period -- Maya (and other Mesoamericans), Maya blue is a pigment that is noticeably resistant to deterioration. After numerous studies (beginning in the early 1900s), it is now thought that at least two things went into its making: indigo dye and a kind of clay, either sepiolite or palygorskite. This article will focus on Maya blue's composition, production, resistance and its uses.

Historical Note
Maya blue has been found within the context of the Late Preclassic. However, it is in the Late Classic that increased usage of Maya blue began. During the beginning of the Late Classic, the use of Maya blue appears to have become common in the Usumacinta region, the Puuc region and Guatemala. The ancient Maya used the pigment through the Postclassic Period and even in the Colonial Period -- though its use declined and disappeared during the latter (around the end of the 1500s).

Color
Maya blue ranges in color from a light blue to green blue, and adjectives connected to its description include "vivid" and "radiant".  The color might be connected to iron as well as iron oxide nanoparticles, though it is also possible that it isn't -- an alternate theory being that it is the ratio of indigo dye to clay. Different shades may have been possible through different kinds of Maya blue recipes.

Indigo Dye
The genus Indigofera has species that can be used to produce indigo dye. The indigo dye the ancient Maya used could have come from different species, such as Indigofera suffruticosa (a shrub whose other names include Guatemala indigo, ti cafe, añil, wild indigo, añil de pasto or just indigo.

As for the way the ancient Maya made their dye -- that has yet to be discovered, and is therefore one of the lingering mysteries of Maya blue. For example, whether or not the dye was a liquid or reduced even further into chunks of dye (which would be ground up). 

The Clay -- Palygorskite or Sepiolite?
Of the resources thus far found in researching Maya blue, most tend to favor palygorskite as the clay that was used; (though some also include sepiolite in their definition. One book, Developments in Palygorskite-Sepiolite Research, states that sepiolite sometimes is found in Maya blue from the Aztec area.)

Also called attapulgite (an older name), palygorskite is defined by Encyclopedia Britannica Online as a fibrous magnesium aluminum silicate. It is a clay whose molecular structure is described as "fibrous", a kind of structure that has "channels" (or tunnels, as Handbook to Clay Science describes them). The "fibrous" structure, it is understood, is necessary for making Maya blue.

Production
It is now thought that it is not enough to mix indigo dye and palygorskite together -- the mixture has to be heated (Handbook says it must be 302 Fahrenheit), and for a couple of days.  As evidence, dehydroindigo (oxidized indigo dye) has been found in Maya blue, which may have formed when heated. Also, a blue color was only obtained, in studies I have found on creating Maya blue, when something else was added (such as acetone or diluted hydrochloric acid), so it is possible the ancient Maya had an acid or acids they could use.

How does the indigo dye bind to the clay?  It is thought that the dye is caught in the channels (or tunnels) of the palygorskite, perhaps at the ends of these channels. 

A Potential Ingredient: Copal
A theory also exists that Maya blue was made by using burning copal resin to bind the indigo and palygorskite. According to Developments, it is yet to be seen whether or not Maya blue could be created by adding palygorskite-indigo dye mix to melted copal -- which melts below 302 degrees Fahrenheit.

Resistance
A word connected to Maya blue is "stable". It is resistant to many things. For example, The Field Museum's Dr. Gary Feinman states that, "Maya blue is a very stable pigment. In other words, it does not rub of or wash off very easily." (Author's transcription.)

But Maya blue can resist more than rubbing and washing. Published in 2009, Electrochemical Methods in Archaeometry, Conservation and Restoration gives a list of things Maya blue can withstand. The book states that Maya blue is resistant to "...acids, alkalis, oxidants, reducing agents, organic solvents or biodegration."

How long can Maya blue resist attack? A study conducted by Rutherford J. Gettens involved putting samples of Maya blue from an incense burner in various liquids, including concentrated hydrochloric acid, concentrated sulfuric acid and concentrated nitric acid. After eighteen hours had passed the samples were still the same color.

Uses
The ancient Maya used Maya blue artistically for their murals, such as the murals at Bonampak, and figurines, such as those found on Jaina Island. Maya blue was also used as part of the color palette in codices. Also, it seems, they used it when preparing people and inanimate objects off as sacrifices.

What was the connection between Maya blue and making sacrifices? The understanding is that votives were covered with the pigment before they were sacrificed. As evidence, at the bottom of the Sacred Cenote, a layer of blue silt was found while it was being dredged. Dr. Feinman states that coating objects (and people) in Maya blue was an act used when making sacrifices to rain deities.


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