Conservation and restoration of Mesoamerican codices is the process of analyzing, preserving, and treating codices for future study and access. It is a decision-making process that aims to establish the best possible methods and tools of preservation and treatment. The conservation-restoration of Mesoamerican literature is essential for understanding the ancient civilizations of Mexico. Efforts of restoration have proved difficult due to their fragility and importance of preserving historical and evidential value. Non-invasive technologies have been a more recent advancement, making analysis and treatment of pre-Hispanic codices a delayed process. As analysis continues, digitization has also been a more recent and valuable means of making information accessible to a wider audience, thus contributing to further research and preservation.
Extant codices
The Pre-Hispanic world had a rich tradition of writing and tlacuilolli (the art of painting codices) before Spanish colonization of the Americas when almost every native document was destroyed. The mere thirteen existing pre-Hispanic codices are now separated into three groups according to geographical region and subject matter. The Mixteca group originated from the Mixteca region of southwestern Mexico and contains predominantly myths, royal genealogies and history. The codices from this group include Codex Zouche-Nuttall; Codex Vindobonensis Mexicanus I; Codex Selden; Codex Bodley; and Codex Colombino. The Borgia group are believed to have been created in the Mixteca-Puebla region of central Mexico and they contain calendrical and ritual information. This group includes the Codex Borgia; Codex Cospi; Codex Laud; Codex Fejérváry-Mayer; and Codex Vaticanus B. Maya codices contained calendrical, astronomical and ritual information and are well known for being the source of today's understanding of Maya civilization. The surviving pre-Hispanic Maya codices include the Dresden Codex; Paris Codex; and Madrid Codex (Maya).
Post-conquest and recovery
Almost all archives and codices of ancient Mesoamerica were destroyed as a result of conquest. Missionaries, physicians, and naturalists from Europe desired to understand and preserve aspects of native customs. Francisco Hernández de Toledo was sent to Mexico by the king of Spain in the 16th century to research medicinal properties of plants and native uses of plants. Friar Bernardino de Sahagún also made it his life's work to preserve the cultural heritage of the people of Tepepulco (present-day Hidalgo). Efforts such as these required them to learn native techniques to reproduce and preserve ancient knowledge in its traditional form. These preservation efforts were within a larger context of the assimilation of native people, and the documentation of native traditions by Europeans can be understood as a retelling through the lens of the conquerors. Much of what is known of Mesoamerican codex-making has been interpreted through these documents and reproductions. Preserving the last remaining codices means understanding how they were created; what materials and colorants were used; and what purposes they served. Recent efforts in codex preservation include non-invasive analysis; preventive conservation practices; digitization and reproductions.
Non-invasive analysis Non-invasive analysis through use of portable tools has been of vital importance to the conservation of Mesoamerican codices today. This is due to the delicate nature of the materials and pigments. “The multi-technique integrated approcach” of MOLAB in studying the Codex Cospi employed UV-vis absorption and emission to determine the sources of red colors on the pages. The reflectance spectra (absorbance maxima at 370,530 and 555 nm) indicated that there were features of “an anthraquinonic lake of animal origin”. The UV-vis reflection measurements were taken using a portable spectrophotometer. Portable devices ensure that the object is not over-handled. X-ray fluorescence (XFR), Infrared (IR) Spectroscopy, Raman spectroscopy, Ultraviolet-visible spectroscopy (UV-vis), Optical microscopy, and reference materials (historical documents and a preparation of Maya Blue) were all used in the analysis of Codex Cospi to determine the sources of the different colorants used. And this was done without having to remove samples from the codex.
The only invasive analysis carried out on the existing pre-Hispanic codices has been limited to small samples of the paper. In analyzing the Maya codices, analysis has confirmed the paper material as bark from “one or more species of the genus ficus" with a white layer of calcium carbonate. The only direct invasive analysis performed on the Madrid Codex consisted of an “examination of two bark paper samples” and was performed by Fudolf Schwede. Both non-invasive and previous destructive analysis has shown the use of carbon black was homogenous between Cospi, Codex Fejérváry-Mayer, Madrid Codex (Maya) and Codex Colombino. Recent technologies have enabled conservators and scientists to examine these documents without excessive handling or invasive sampling while much more has been discovered in regard to materials, colorants, and context.
X-ray fluorescence (XRF)
This method determines the chemistry of an object sample by measuring the fluorescent (or secondary) X-ray emitted from a sample when it is excited by a primary X-ray source.
Infrared (IR) spectroscopy
IR spectroscopy is used in determining and identifying the structural composition of an object. It measures absorption, emission and reflection of infrared light interacting with a molecule.
Raman spectroscopy
A technique used to detect molecular vibrations. Used in the chemical analysis and characterization of solids, liquids and gases.
UV-vis
Ultraviolet-visible (UV-vis) spectroscopy determines the concentration of analytes in a solution through light absorption or reflectance.
Optical microscopy
This method employs the use of an optical microscope to analyze a sample.
Digital microscopy
Digital microscopy employs a microscope that has a digital camera attached. This allows for images of a sample to be viewed and analyzed on an electric monitor display.
In situ analysis
The existing pre-Hispanic codices have been examined in situ while employing different MOLAB techniques. These techniques include digital microscopy, Raman, UV-vis reflectance, and emission spectroscopy. To avoid stress, damage, and movement, supports were created by conservators to imitate the zigzag screenfold structure of the codices. In examining the fragment Cortesiano, part of the Madrid Codex, a specially designed support was created to hold the document vertically so that the images would be visible without having to handle them during analysis. The colorants, stylistic elements, and material components allow a better understanding of certain differences, as well as technical relationships between the codices, which contribute to the overall knowledge of the codex-making tradition in Mesoamerica.
Infrared spectroscopy allowed for analysis of the white layer covering on each side of the Codex Cospi and Codex Ferjérváry-Mayer to be identified as a composition of gypsum and calcium carbonate. The white layer on the Codex Ferjérváry-Mayer is “composed of a mixture of two different hydration forms of calcium sulfate: gypsum and anhydrite (anhydrous calcium sulfate)”. In all the codices that were analyzed, the white layer on the back and front of each codex were identical in composition which provides evidence that the white background was “prepared in a single moment, independently from the painting sessions”. Analysis between the codices have indicated “clear-cut division between the Borgia group and Mixtec codices,” which have gypsum-based paint covering an animal skin support, in contrast with the Maya codices which have a calcium carbonate-base covering a paper support.
Preventive conservation and agents of deterioration
Preventive conservation is the process and practice of eliminating or slowing the effects of agents of deterioration. It requires constant assessment of environmental factors that put the collection at risk and must consider the effects of certain agents of deterioration on the various materials that make up the collection. The agents of deterioration that may put a collection at risk are physical forces; theft; fire; water; incorrect temperature; incorrect relative humidity (RH); pollutants; dissociation; pests; and light. This practice has become interdisciplinary and often requires a collective knowledge of science, “chemistry, physics, biology, engineering, systems science, and management” all while considering different value systems of different cultures.
Materials
The Borgia Group are composed of long strips of deer hide folded like an accordion and sized with white gesso. The covers consist of hide or wood attached to each end. The Maya codices, in contrast, are composed of a long strip of bark paper, or Amate, folded in the same accordion-like, screen-fold way as the Codex Borgia group. The most important codices were likely adorned with jaguar fur covers, although there is only documentational evidence of this.
In applying preventive conservation techniques to the preservation of Mesoamerican codices, the material composition of these objects put them at high risk. The colorants used on each of the codices are both organic and inorganic making the composite nature of these books difficult to preserve. The “detection of orpiment on the verso of Codex Cospi and on both sides of Codex fejérváry-Mayer” proved most unexpected as an inorganic pigment containing high amounts of arsenic trisulfide in the Raman spectrum. As some of the codices contain inorganic pigment, such as carbon black, they require attention to environmental pollutants that might react with or change the chemical structure (such as corrosion or dissolution of constituents). Along with the organic and inorganic pigments, gypsum and calcium carbonate were other compounds detected through analysis.
Organic materials such as bark paper, deer skin, and colorants are highly susceptible to deterioration from fluctuations in RH as well as incorrect RH. Furthermore, organic materials are hygroscopic (absorbing and emitting water). These materials attract mold, insects, rodents and other pests, and they are highly sensitive to light. The complex organic components of Mesoamerican codices, along with their fragility due to age, require a strictly controlled environment that limits exposure to light and maintains correct RH and temperature. “It takes time for objects made from hygroscopic materials to adjust to changes in RH”, which “can range between a few hours (such as a sheet of paper) to several weeks (such as a wooden sculpture)”. Although short-term fluctuations may be tolerated, damage can result in situations where the extreme change in temperature or RH remains long enough for the object to respond.
Through assessing all the possible risks, conservators develop strategies that aim to balance these risks with the appropriate risk management strategies. Digitization and sharing of information are of utmost importance for improving the field of Conservation-restoration. A push toward digitization and digital records management will also work to prevent risks of dissociation.
Treatment of Post-Hispanic codices