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Non Destructive In situ Study of Mexican Codexes: Methodology and First Results of

Materials Analysis for the Colombino and Azoyu codexes.

S. Zetina1, J.L. Ruvalcaba2*, M. López Céceres3, T. Falcón1, E. Hernández1, C. González3,

E. Arroyo1

1Instituto de Investigaciones Estéticas, UNAM, Mexico

2Instituto de Fisica, Universidad Nacional Autónoma de Mexico (UNAM), Mexico. 3Biblioteca Nacional de Antropología e Historia, INAH, Mexico

Introduction

Little is known about manuscript painting practices in pre Hispanic Mesoamerica, around the

world just sixteen codices from pre-Hispanic Mexico survived the Conquest, most of them are

held at European collections. Even though the codices manufacture was spread during the

Postclassic period (1325-1521 A.D.), the features of the surviving pre-Hispanic and Early

Colonial documents show some technical differences that can be related to local traditions. The

only pre-Hispanic codex held at a Mexican Collection is Colombino Codex from Mixtec coast.

But many manuscripts produced in New Spain preserved the indigenous codex tradition and

practices. These manuscripts are an important information source of the materials used in the

writing and coloring tradition. Usually, organic colorants obtained from local plants, carbon

inks, and calcium rich preparation layers were employed. Nevertheless, there are few studies of

original manuscripts, done on a reduced amount of samples (Gonzalez C. 1998) and scarce

information has been obtained on this subject. In this research a specific non-destructive

methodology has been developed to carry out in situ general examination of the codices and the

analysis of inks, colorants and pigments. In particular, a comparative study between the pre-

Hispanic codex Colombino, and the colonial codex Azoyu I is presented. Previously the

colonial codex de la Cruz-Badiano has been studied using the same methodology (Zetina S. et

al. 2008).

The Colombino Codex tells the history of Mixtec lord Eight Deer Jaguar Claw (Carrasco D.

2001). The support is animal skin sewn with an agave thread. One side was prepared for

painting with a thick polished white ground. Colors were applied saturated and flat on sharply

defined areas. The proportion and regularity of the figures is constant. The color palette is

reduced: blue, green; red and yellow which are used saturated and diluted, and a bright orange

*Corresponding author: Apdo. Postal 20-364, Mexico DF 01000, Mexico. tel: +52 55 56225162 fax: +52 55 56225009 e-mail: sil@fisica.unam.mx

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found only in scarce details, which has almost disappeared; and black, in transparencies and

more opaque for the contour lines.

On the other hand, Codex Azoyu I was produced during the 16th century; the front section has a

pictographic tradition historical account of the Guerrero region of the Tlachinollan Caltitlan

reign between 1300 and 1565. In the Tlapa region, Nahua, Mixtec and Tlachinolla people

coexisted as today. In 38 pages, the document describes the conquest of about twenty places

located in eastern Guerrero. One folio has written words in Latin alphabet (23r). The support is

amate paper (made from an indigenous bark) screen folded in 28 pages. The historical section,

the most antique, covers the obverse. A calendaric frame delimits each page; the squares at the

center contain historical pictographs and were prepared with a slight wash applied over the

surface of the paper before painting. Pink, red, orange, brown, yellow, black and gray, blue-

green and green were found, in pale shades. Over the reverse, a genealogical section is depicted

in 11 pages, it is considered more recent than the other. The painting technique is quite similar

in the second version. There is a third later addition, a cartographic and economic section.

Methodology

Firstly, all the documents were digitally photographed after light calibration. We used

fluorescent tubes illumination daylight color temperature (Hanckok) and a Mac Beth

spectrophotometer in order to measure color temperature at 5700K. All the photographs were

taken with a digital camera Nikon D2x with and a 50 mm objective. Limited UV examinations

were carried out by a low power 8W UV lamp with long and short wave (365 and 254 nm

respectively). All the images were recorded by digital photography. Also IR reflectography was

performed with a lead sulfide vidicon tube (Hammamatsu C2741) with a sensibility range from

400 to 1800 nm and led array lighting (940nm). IR images were obtained by a digital shot

directly to the monitor.

In order to interpret the IR and UV images of the codex, a comparison with reference of

pigments, colorants, inks and other materials commonly used in manuscripts and illuminations

was fundamental. Reference standards were prepared on 100% cotton paper with

carboxymethyl-cellulose used as binder. Under IR illumination gypsum has a brilliant

appearance but iron gall inks have a medium absorbance and iron oxides appear very opaque.

On the contrary, different dyes and colorants (prepared as lakes or fixed into clays) are

transparent in different grades. Under UV lighting gypsum had a bright violet fluorescence

while lakes, cochineal and achiote plant showed also some kind of bright fluorescence. Iron

oxides and iron gall inks (even mixed with cochineal) had a dark violet response to UV.

After proceeding with imaging techniques, the manuscripts were analyzed using our SANDRA

XRF portable system. This device has a Mo X-ray tube and two sets of measurements were

carried out by two different X-ray detectors (CZT and Si-Pin) with a 75 W Mo X-ray tube. CZT

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detector is more suitable for pigments analysis while the Si-Pin detector may detect lighter

elements. Measuring time was 90 s at 40 kV and 30 mA with a X-ray spot of 1 mm dia. Only

qualitative measurements were carried out.

Results

Figure 1 shows the calibrated digital photography of one folio of the Colombine codex as well

as the corresponding UV and IR images. The examination of the complete document showed

similar behaviors for the entire codex. The homogeneity of the materials and depictions may

correspond to a single writing period. The UV red color fluorescence is quite similar to the

cochineal colorant. Instead the yellow colorant presents a bright fluorescence and its identity is

unknown. Under IR illumination the colors are transparent or presents a light grey tone, similar

to the organic materials features.

Considering the imaging techniques results and reflectivity and fluorescence observations, XRF

measurements focused in 6-8 folios in order to get representative data. XRF results for the

Colombine indicate the presence of S, K, Ca, Mn, Fe, Cu, Zn, Sr and Pb in the leather.

Nevertheless in the ground only S, Ca, K Fe and Sr were detected. A comparison of with a

gypsum reference match with the S/Ca ground ratio. On the other hand the black and the red

colors did not show any significant difference by comparison to the ground X-ray ratios. This

means that the black may be carbon and the red a colorant. The yellow color presents a similar

behavior but with an increase in the K content by a factor of 7. K contents may be used for an

identification of the yellow colorant. Besides the detected ground elements, the green and blue

colors presents Si, Mn, Ti and an increment of Fe by a factor of 5 or more (figure 1). This result

suggests the use of clay to fix these colors. Perhaps, the green color was produced by mixing the

yellow and the blue colorants.

On the other hand, the calibrated image as well as the UV and IR imaging for the first part of

the Azoyu codex is shown in figure 2. Several differences have been observed between the

epochs but the sections seem homogeneous. For the first part, the preparation layer is gypsum in

the interior frame. Several corrections may be observed from UV images. Red color has

fluorescence similar to the cochineal one. Blue color may correspond to indigo. The interior

frame presents the gypsum fluorescence. No preparation ground has been observed for the

calendaric frame.

The main XRF results for the Azoyu codex are shown in table 1. Colorants were used for the

first and second parts but European pigments and mixtures, mainly for green colors, appeared

only in the latest section. Carbon and iron-gall inks were used in the three sections. Despide the

European influences, we may consider that the earlier epochs of the Azoyu codex were written

and painted following pre-Hispanic traditions in the use of materials for colors. Further material

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comparisons with other codexes may suggest its main cultural manufacturing trends: Nahua,

Mixtec or Tlachinolla.

Figure 1. The Colombine codex (a) folio 7, (b) UV imaging 365nm (c) IR reflectography, 940

nm led illumination. XRF spectrum from green and blue region is shown. Clay presence was

identified for these colors.

Figure 2. The Azoyu I codex. (a) folio 18, 1st epoch (b) UV imaging 365nm (c) IR

reflectography, 940 nm led illumination. Only in the white area of the historic frame, gypsum

was identified in the ground by XRF.

a b

c

aa bb

cc

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Table I. Identification from XRF results of the colors and inks used in the Azoyu codex in its

three sections.

Color 1st Epoch 2nd. Epoch 3rd. Epoch

Red organic organic minium (Pb)

Pink organic organic minium and lead white

Yellow organic organic limonite (Fe oxides)

Green organic organic dark.: organic light: limonite + indigo

Blue organic (indigo) organic (indigo) organic (indigo)

White gypsum gypsum lead white

Black carbon carbon carbon

Inks carbon-irongallic inks carbon-irongallic inks iron gallic inks

Conclusions

From our UV-IR imaging and XRF measurements we may conclude that the composition of the

Colombine codex is very homogeneous. Colorants were applied on a gypsum ground layer and

carbon inks were used. Blue color was prepared by colorant fixed to clay, while green may be

made from blue and yellow superposition.

In the Azoyu codex, although it is a colonial one, colorants are in the first and second epochs,

while only in the last epoch colorants are replaced by European pigments. This means that the

pre-Hispanic traditions and the use of colorants remained.

In contrast, the colonial de la Cruz-Badiano codex has different features but also dyes are

present. From material point of view, this codex is diverse to the Colombino and Azoyu ones.

UV-IR imaging works perfectly for a general prospection of the document, then XRF may be

applied on representative areas. Further analyses are required using Raman and FTIR

spectroscopies for organic compound characterization.

Acknowledgements

This research has been supported by the Mexico CONACyT grand U49839-R.

References

Carrasco D. (2001). Colombino-Becker codex in The Oxford Encyclopedia of Mesoamerican

Cultures vol. 1 Oxford University Press, Oxford. 231-232.

Gonzalez Tirado C. (1998). Análisis de pigmentos en ocho códices mexicanos sobre piel, M.Sc.

thesis, The Monfort University, Leicester.

Zetina S., Ruvalcaba J.L., Falcón T., Hernández E., González C., Arroyo E., López Cáceres M.,

(2008). Painting syncretism: A non destructive analysis of the Badiano codex, 9th

International Conference on ART2008. Jerusalem, Israel. In CD.