Maya Blue Research Articles

Comparative study of different indigo-clay Maya Blue-like systems using the voltammetry of microparticles approach

Using the voltammetry of microparticles approach, the electrochemical response of complexes prepared with indigo plus different clays in contact with aqueous electrolytes is described. Indigo presents a strong attachment with palygorskite and sepiolite in contrast to a weak attachment to planar clays (montomorillonite and kaolinite). Cyclic voltammetric and chronoamperometric data provide estimates of the variation of the concentration of indigo and dehydroindigo with the depth on clay crystals. The indigoids (indigo and dehydroindigo) penetrate more in palygorskite than in sepiolite, and this penetration is favoured by thermal treatments (very efficient up to 130 °C). The indigo concentration decreases monotonically versus depth, while the dehydroindigo one increases from zero in the external region of the crystals to a maximum at a depth between 40 and 80 nm and then decreasing rapidly. These facts are directly linked to the much higher resistance to acid attack of palygorskite–indigo pigments (Maya Blue) than sepiolite–indigo ones.

Maya blue–green pigments found in Calakmul, Mexico: a study by Raman and UV‐visible spectroscopy

AbstractAfter more than two decades of fieldwork in the Maya archaeological site of Calakmul, Mexico, numerous remnants of blue and green pigments have been reported on wall paintings, as well as on funerary paraphernalia, such as masks, miniatures and vases. The importance of these pigments is linked to the sacred values that Maya people associate with blue and green colours since pre‐Columbian times. These hues symbolise water, and are therefore associated with fertility and regeneration. This paper aims to perform a survey of the blue and green pigments used in the Early Classic and Late Classic periods in Calakmul (300–850 A.D.), in order to have a better understanding of their chemical composition and origin. Analyses were performed on microsamples using Raman and UV‐visible spectroscopies to evaluate the possibilities that these techniques can offer in future in situ researches on Mesoamerican archaeological materials and objects. With these analyses, we have documented a large blue–green chromatic palette, which includes the earliest Blue Maya and Green Maya known to date, as well as malachite, pseudomalachite and an unknown‐up‐to‐now blue‐green mineral pigment, veszelyite, used specifically for ritual objects. The results indicate a careful selection of imported products and the mastering of a complex ancient Maya pictorial tradition. Copyright © 2008 John Wiley & Sons, Ltd.

Spectroscopic analysis of a dye–mineral composite–a Raman and FT‐IR study

AbstractIn this investigation, we address the question of how organic thioindigo binds to inorganic palygorskite to form a pigment similar to Maya Blue. We also address how such binding, if it occurs, might be affected by varying the proportion of dye relative to that of the mineral, and by varying the length of heating time used in preparation of the pigment. In addition to samples of palygorskite and thioindigo both alone, four synthetic pigment samples were prepared; two samples of 8 wt.% dye, one heated at 170 °C for 3 h and one at 170 °C for 9 h, and two samples of 16 wt.% dye, one heated at 170 °C for 3 h and one at 170 °C for 9 h. All samples were examined using Fourier transform‐infrared (FT‐IR) and FT‐Raman spectroscopy. For the pigment samples, FT‐IR peaks at 1627 cm−1 are attributed to a downshifted CO stretching mode of thioindigo due to dye–clay interaction. This interpretation is corroborated by FT‐Raman CO peaks with 14 cm−1 shifts to lower wavenumber for the pigment relative to thioindigo alone. Additional Raman scattering between 550 cm−1 and 650 cm−1 also suggests dye–clay interaction through metal–oxygen bonding. We are thus led to the possibility of mostly hydrogen bonding between silanol and carbonyl at lower dye concentration, with a predominance of metal–oxygen bonding at higher dye concentration. Copyright © 2008 John Wiley & Sons, Ltd.

Digging that Maya blue

Science NewsVolume 173, Issue 9 p. 134-134 This Week Digging that Maya blue Rachel Ehrenberg, Rachel EhrenbergSearch for more papers by this author Rachel Ehrenberg, Rachel EhrenbergSearch for more papers by this author First published: 30 September 2009 https://doi.org/10.1002/scin.2008.5591730908AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume173, Issue91 March 2008Pages 134-134 RelatedInformation

The first direct evidence for the production of Maya Blue: rediscovery of a technology

Maya Blue is a colour that is more than a pigment; it had roles in status, ritual and performance, being daubed onto pots and people before sacrifice. Here researchers use experimental and historical evidence to discover how it was made, including direct scientific analysis of Maya Blue on a pot thrown into the sacred well at Chichén Itzá. The results indicate that the formation of the colour was actually part of the ritual.

Quantum mechanical model for Maya Blue

AbstractThis work is about Maya Blue (MB), a pigment developed by Mesoamerican civilizations between the 5th and 16th centuries from an aluminosilicate mineral (palygorskite) and an organic dye (indigo). Two different supramolecular quantum‐mechanical models afford explanations for the unusual stability of MB based on the oxidation of the indigo molecule during the heating process and its interaction with palygorskite. A model considering indigo derivatives attached to several aluminates shows the principal features of the experimental visible spectrum of MB within the TD‐DFT methodology. Another model of an indigo oxidized species confined within an inorganic supramolecular cavity system, that involves about 170 atoms, was calculated after a large configuration interaction of single excited determinants within the NDOL approximation (Montero‐Cabrera et al., J Chem Phys, 2007, 127, 145102). It allows a correct reproduction and interpretation of the corresponding spectrum. This second methodology provides the most satisfactory results, being able to manage very big molecular systems at a QM level. Structural explanation for the unusual stability of MB is also provided. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008

Pre-columbian nanotechnology: reconciling the mysteries of the maya blue pigment

The ancient Maya combined skills in organic chemistry and mineralogy to create an important technology – the first permanent organic pigment. The unique color and stability of Maya Blue can be explained by a new model where indigo dye fills the grooves present at the surface of palygorskite clay, forming a hydrogen bonded organic/inorganic complex. Existing theory assumes the dye is dispersed inside the channels of an opaque mineral. Based on data from thermal analysis, synchrotron and neutron diffraction, ESEM and chemical modelling calculations, our new concept of Maya Blue structure resolves this contradiction and suggests some novel possibilities for more durable, environmentally benign pigments.

Synchrotron powder diffraction on Aztec blue pigments

Some samples of raw blue pigments coming from an archaeological rescue mission in downtown Mexico City have been characterized using different techniques. The samples, some recovered as a part of a ritual offering, could be assigned to the late Aztec period (XVth century). The striking characteristic of these samples is that they seem to be raw pigments prior to any use in artworks, and it was possible to collect a few μg of pigment after manual grain selection under a microscopy monitoring. All pigments are made of indigo, an organic colorant locally known as anil or xiuhquilitl. The colorant is always found in combination with an inorganic matrix, studied by powder diffraction. In one case the mineral base is palygorskite, a rare clay mineral featuring micro-channels in its structure, well known as the main ingredient of the Maya blue pigment. However, other samples present the minerals sepiolite (a clay mineral of the palygorskite family) and calcite. Another sample contains barite, a mineral never reported in prehispanic paints. We present the results of characterization using high resolution powder diffraction recorded at the European Synchrotron Radiation Facility (BM25A, SpLine beamline) complemented with other techniques. All of them gave consistent results on the composition. A chemical test on resistance to acids was done, showing a high resistance for the palygorskite and eventually sepiolite compounds, in good agreement with the excellent resistance of the Maya blue.

Organic/inorganic complex pigments: Ancient colors Maya Blue

Maya Blue is an ancient blue pigment composed of palygorskite clay and indigo. It was used by the ancient Maya and provides a dramatic background for some of the most impressive murals throughout Mesoamerica. Despite exposure to acids, alkalis, and chemical solvents, the color of the Maya Blue pigment remains unaltered. The chemical interaction between palygorskite and indigo form an organic/inorganic complex with the carbonyl oxygen of the indigo bound to a surface Al3+ in the Si–O lattice. In addition indigo will undergo an oxidation to dehydroindigo during preparation. The dehydro-indigo molecule forms a similar but stronger complex with the Al3+. Thus, Maya Blue varies in color due to the mixed indigo/dehydroindigo complex. The above conclusions are the result of application of multiple techniques (X-ray diffraction, differential thermal analysis/thermal gravimetric analysis, high resolution transmission electron microscopy, scanning electron microscopy, infrared and Raman spectroscopy) to the characterization of the organic/inorganic complex. A picture of the bonding of the organic molecule to the palygorskite surface forming a surface complex is developed and supported by the results of density functional theory calculations. We also report that other organic molecules such as thioindigo form similar organic/inorganic complexes thus, opening an entirely new class of complex materials for future applications.

Raman and infrared studies of synthetic Maya pigments as a function of heating time and dye concentration

AbstractMaya Blue is a famous indigo‐based pigment produced by the ancient Mayas. The organic/inorganic complexes inspired by Maya Blue have led to a new class of surface compounds that have novel applications to pigment industries. Materials analyzed in the present work are made by a synthetic route, and demonstrate chemical stability similar to that of the ancient Maya Blue samples. However, we have learned that stable complexes can be synthesized at much higher dye concentrations than used by the Mayas. Analysis by FT‐Raman and FT‐IR spectroscopy demonstrates the partial elimination of the selection rules for the centrosymmetric indigo, indicating distortion of the molecule. This distortion accounts for the observed color changes, as the molecular orbital structure is modified, allowing the complex to stabilize. The spectroscopic data also shows the disappearance of the indigo NH bonding, as the organic molecules incorporate into palygorskite material. A structural change of indigo to dehydroindigo during heating is suggested by this result. Infrared data confirm the loss of zeolitic water and a partial removal of structural water after the heating process. Evidence of bonding between cationic aluminum and dehydroindigo through oxygen and nitrogen is revealed by FT‐Raman measurements at higher dye concentrations. Copyright © 2007 John Wiley & Sons, Ltd.

Chemometric Study of Maya Blue from the Voltammetry of Microparticles Approach

The use of the voltammetry of microparticles at paraffin-impregnated graphite electrodes allows for the characterization of different types of Maya Blue (MB) used in wall paintings from different archaeological sites of Campeche and YucatAn (Mexico). Using voltammetric signals for electron-transfer processes involving palygorskite-associated indigo and quinone functionalities generated by scratching the graphite surface, voltammograms provide information on the composition and texture of MB samples. Application of hierarchical cluster analysis and other chemometric methods allows us to characterize samples from different archaeological sites and to distinguish between samples proceeding from different chronological periods. Comparison between microscopic, spectroscopic, and electrochemical examination of genuine MB samples and synthetic specimens indicated that the preparation procedure of the pigment evolved in time via successive steps anticipating modern synthetic procedures, namely, hybrid organic-inorganic synthesis, temperature control of chemical reactivity, and template-like synthesis.

Sourcing the Palygorskite Used in Maya Blue: A Pilot Study Comparing the Results of INAA and LA-ICP-MS

Maya Blue is an unusual blue pigment consisting of a clay-organic complex of indigo and the unusual clay mineral palygorskite (also called attapulgite). Used on pottery, sculpture, and murals from the Preclassic to Late Colonial periods largely in Mesoamerica, blue was the color of sacrifice and ritual. Did the palygorskite used to make Maya Blue come from a restricted source in Yucatán like Shepard, Arnold, Arnold and Bohor believed, or from widespread sources like Littmann argued? This report presents the results of a pilot study comparing INAA and LA-ICP-MS analysis of 33 palygorskite samples collected from different parts of the Maya area. These data reveal that it is possible to discriminate mineral source locations, and that it should be possible to determine whether the palygorskite used to make Maya Blue came from widespread sources or was traded widely from one or a few sources. Consideration of contextual information such as agency, landscape and language suggest that the Shepard/Arnold/Bohor hypothesis is more plausible than that of Littmann. No matter which hypothesis is supported, however, each has significant implications for the relationship of the diffusion of Maya Blue (or the knowledge of its production) to Maya social organization.

Indigo/Dehydroindigo/Palygorskite Complex in Maya Blue: An Electrochemical Approach

The voltammetry of microparticles methodology is applied to describe the electrochemistry of indigo and Maya Blue, a nanostructured organic−inorganic material, in contact with different MeCN electrolytes. The voltammetric response of synthetic specimens and genuine Maya Blue samples differ significantly from that of indigo microparticles, all being conditioned by the size-dependent insertion of electrolyte ions into the solid. Electrochemical data indicate that formation of Maya Blue involves a significant reorganization of zeolitic and/or structural water of the clay and confirms the presence of dehydroindigo accompanying indigo in the palygorskite matrix.

Thermal and Raman-spectroscopic analysis of Maya Blue carrying artefacts, especially fragment IV of the Codex Huamantla

Maya Blue, a pigment composed of very low concentrations of natural indigo and the clay mineral palygorskite, is one of the most brilliant blue dyes, intensively used for more than 2000 years in Mesoamerica. It is extremely stable against environmental attacks and was applied by the Indians for inside and outside mural paintings, ceramics, textiles and for colouring their famous codices. In the present paper it was studied as a powder (compared with modern synthetic indigo) and as colour on tissues, a Maya clay head, and fragment IV of the famous Codex Huamantla. Investigations using Raman spectroscopy in the visible and near-infrared range showed a high degree of correspondence among all Maya Blue-carrying samples and a good agreement with synthetic indigo. Additional spectral lines may be explained by a transformation of the planar indigo molecule when binding to the palygorskite lattice. Thermal investigations of the original “amatl” paper of the codex and of recent paper from fig-trees showed a high similarity and thus proved that this tree was chosen for paper making by Mayas, Aztecs and other Indian tribes. This was also true for the codex.

The invention of blue and purple pigments in ancient times

This tutorial review examines manmade blue and purple pigments appearing in antiquity. They were obtained by chemical synthesis from mineral starting materials and refer to chemical compounds: Egyptian Blue (CaCuSi4O10), Han Blue (BaCuSi4O10) and Han Purple (BaCuSi2O6), Maya Blue (x.indigo.(Mg,Al)4Si8(O,OH,H2O)24) and Ultramarine Blue (Na,Ca)8(AlSiO12)(S, SO4,Cl). The Egyptian and Chinese copper-based pigments are assumed to have been developed independently and are presumably an outcome of the historical developments in glazing techniques. A technology transfer from Egypt into China cannot be fully excluded but, based on the facts acquired up to now, looks less probable.

Crystal structure refinement of Maya Blue pigment prepared with deuterated indigo, using neutron powder diffraction

Maya Blue, a synthetic pigment produced by the ancient Mayas in pre-Columbian America, is the combination of a fibrous clay (palygorskite) and an organic blue dye (indigo). The main features of the structure of Maya Blue are already known, although the specific interactions occurring between clay and dye have yet to be completely explained. The details of the structure were studied using the Rietveld method on neutron powder diffraction patterns collected at POLARIS (Spallation Neutron Source ISIS) on a Maya Blue sample freshly synthesized using deuterated indigo. The position of the dye molecule in the structure of Maya Blue and the nature of its interactions with the clay framework were described. In the pigment, indigo lies within the palygorskite channels partially substituting the zeolitic water previously expelled during the synthesis. The dye and the water mutually compete to occupy the clay microchannels, although some portions may be empty, containing neither indigo nor water. Furthermore, the encapsulation of indigo increases the disorder in the disposition of the residual zeolitic water. The occupancy of indigo results to be higher in the orthorhombic than in the monoclinic polymorph, presumably for the faster loss of zeolitic water in the former polymorph during heating. The quantity of indigo in the pigment is rather low ( b axis. The stability of Maya Blue is guaranteed by strong H-bonds formed between the clay structural water and the indigo C=O group. All the present results are coherent with data obtained in previous studies.

On the Raman spectrum of Maya blue

AbstractMaya blue is a marvelous pigment with extraordinary properties. It was invented by the Maya around VII–VIII century and used by many Mesoamerican peoples in prehispanic times. It is made by encapsulating natural indigo into an inorganic clay matrix of palygorskite. The palygorskite–indigo mixture becomes acid‐resistant when a moderate thermal treatment is applied. The chemical reasons of the unusual stability of the pigment and the exact mechanism of interaction between the indigo and the clay are not well understood. We present a Raman study of different preparations of Maya blue and other mixtures of indigo with other inorganic materials. We found that the unheated mixture of indigo with palygorskite presents the same Raman spectrum as Maya blue, indicating that the differences with respect to the indigo spectrum are not due to the interaction produced during the thermal treatment, which makes the mixture acid‐resistant. Moreover, indigo mixed with other clays, like sepiolite or montmorillonite, presents a Raman spectrum very similar to that of Maya blue. Some chemical mechanisms that could explain these spectra, and the suitability of Raman spectroscopy for identifying Maya blue are discussed. Copyright © 2006 John Wiley & Sons, Ltd.

Dehydroindigo: A New Piece into the Maya Blue Puzzle from the Voltammetry of Microparticles Approach

Combining a novel technique, the voltammetry of microparticles, with spectrometric, nuclear magnetic resonance, electron microscopy, and atomic force microscopy data, Maya Blue is detected in wall paintings of the Substructures A-3, A-5, and A-6, dated in the Early Classical period (440-450 a.c.), and the Substructure II-C, dated in the Late Preclassical period (150 b.C.), in the archaeological site of Calakmul (Campeche, Mexico), thus providing evidence on the use of the pigment 750 years prior to the date currently accepted. Electrochemical measurements, supported by spectrometric data, indicate that the presence of palygorskite-attached dehydroindigo, the oxidized form of indigo, contributes to the greenish color of Maya Blue. Enthalpy and entropy of attachment of such compounds to palygorskite are calculated from the temperature dependence of electrochemical data. Both attachment processes are endothermic, becoming thermodynamically spontaneous at moderate temperatures. Accordingly, ancient Mayas may modulate the hue of Maya Blue from turquoise to greenish blue by controlling the temperature during the crushing process.

SYNTHESIS AND ACID RESISTANCE OF MAYA BLUE PIGMENT*

Maya blue is an organo‐clay artificial pigment composed of indigo and palygorskite. It was invented and frequently used in Mesoamerica in ancient times (eighth to 16th centuries). We analyse in this paper one of the characteristics of Maya blue that has attracted the attention of scientists since its rediscovery in 1931: its high stability against chemical aggression (acids, alkalis, solvents, etc.) and biodegradation, which has permitted the survival of many works of art for centuries in hostile environments, such as the tropical forest. We have reproduced the different methods proposed to produce a synthetic pigment with the characteristics of the ancient Maya blue. The stability of the pigments produced using either palygorskite or sepiolite has been analysed by performing acid attacks of different intensities. The results are analysed in terms of pigment decolouration and destruction of the clay lattice, revealed by X‐ray diffraction. Palygorskite pigments are much more resistant than sepiolite pigments. It is shown that indigo does not protect the clay lattice against acid aggression. We show that Maya blue is an extremely resistant pigment, but it can be destroyed using very intense acid treatment under reflux.

Maya Blue: A Computational and Spectroscopic Study

Maya Blue pigment, used in pre-Colombian America by the ancient Mayas, is a complex between the clay palygorskite and the indigo dye. The pigment can be manufactured by mixing palygorskite and indigo and heating to T > 120 degrees C. The most quoted hypothesis states that the dye molecules enter the microchannels which permeate the clay structure, thus creating a stable complex. Maya Blue shows a remarkable chemical stability, presumably caused by interactions formed between indigo and clay surfaces. This work aims at studying the nature of these interactions by means of computational and spectroscopic techniques. The encapsulation of indigo inside the clay framework was tested by means of molecular modeling techniques. The calculation of the reaction energies confirmed that the formation of the clay-organic complex can occur only if palygorskite is heated at temperatures well above the water desorption step, when the release of water is entropically favored. H-bonds between the clay framework and the indigo were detected by means of spectroscopic methods. FTIR spectroscopy on outgassed palygorskite and freshly synthesized Maya Blue samples showed that the presence of indigo modifies the spectroscopic features of both structural and zeolitic water, although no clear bands of the dye groups could be observed, presumably due to its very low concentration. The positions and intensities of delta(H2O) and nu(H2O) modes showed that part of the structural water molecules interact via a hydrogen bond with the C=O or N-H groups of indigo. Micro-Raman spectra clearly evidenced the presence of indigo both in original and in freshly synthesized Maya Blue. The nu(C=O) symmetric mode of Maya Blue red-shifts with respect to pure indigo, as the result of the formation of H-bonds with the nearest clay structural water. Ab initio quantum methods were applied on the indigo molecule, both isolated and linked through H-bonds with water, to calculate the magnitude of the expected vibrational shifts. Calculated and experimental vibrational shifts appeared to be in good agreement. The presence of a peak at 17.8 ppm and the shift of the N-H signal in the 1H MAS NMR spectrum of Maya Blue provide evidence of hydrogen bond interactions between indigo and palygorskite in agreement with IR and ab initio methods.