Dyes were used in Mexico since early pre-Hispanic periods for coloring of fibers, codex writing, and mural paintings, among other purposes. From the wide variety of Mexican dyes, only a handful has been studied at length. Moreover, few studies had been devoted to the identification of these substances in artistic or historical objects, in part, because of the lack of a suitable technique that complies with the nondestructive or microdestructive requirements that involves working with such objects. Surface-enhanced Raman spectroscopy (SERS) may provide the tool needed to identify the more than 20 dyes that can be found in Mexico and the first step would be acquiring their SERS spectra in laboratory conditions. To fulfill that goal, carminic acid, cochineal (Dactylopius coccus), achiote (Bixa orellana), muitle (Justicia spicigera), zacatlaxcalli (Cuscuta sp.), brazilwood (Caesalpinia echinata), and cempazuchitl (Tagetes erecta) SERS spectra were recorded in aqueous solution and directly on dyed wool fibers, using silver colloids as SERS substrate. Ag nanoparticles were prepared by chemical reduction with sodium citrate and characterized by UV-Vis spectroscopy and high resolution transmission electronic microscopy. Pure carminic acid was used for control SERS spectra and then samples of cochineal, achiote, muitle, zacatlaxcalli, brazilwood, and cempazuchitl were tested. Samples were prepared either by extraction from their natural sources or by dyeing the fibers; in both cases traditional recipes were followed. The acquired spectra may serve in future research as comparative references for the identification of the dyes present in cultural artifacts, and in the case of cempazuchitl, muitle, and zacatlaxcalli, these are probably the first reported Raman spectra of such plants.

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Painters often acquire a deep empirical knowledge of the way in which paints and inks behave. Through experimentation and practice, they can control the way in which fluids move and deform to create textures and images. David Alfaro Siqueiros, a recognized Mexican muralist, invented an accidental painting technique to create new and unexpected textures. By pouring layers of paint of different colors on a horizontal surface, the paints infiltrate into each other creating patterns of aesthetic value. In this investigation, we reproduce the technique in a controlled manner. We found that for the correct color combination, the dual viscous layer becomes Rayleigh-Taylor unstable: the density mismatch of the two color paints drives the formation of a spotted pattern. Experiments and a linear instability analysis were conducted to understand the properties of the process. We also argue that this flow configuration can be used to study the linear properties of this instability.

Jackson Pollock’s most celebrated abstract paintings were produced with the so-called dripping technique. By pouring liquid paint with the help of a stick or from a can, Pollock deposited viscous fluid filaments on a horizontal canvas, rhythmically moving around it. The intricate webs of lines, ubiquitous in his compositions, have fascinated art historians and scientists. Based on image analysis of historical video recordings, we experimentally reproduced the painting process. We conclude that Pollock avoided the appearance of the hydrodynamic instabilities, contrary to what was argued by previous studies. Pollock selected the physical properties of the paint to prevent filament fragmentation before deposition, and applied it while moving his hand sufficiently fast and at certain heights to avoid fluid filaments from coiling into themselves. An understanding of the physical conditions at which these patterns were created is important to further art research and it can be used as a tool in the authentication of paintings.

Although the use of cellulose nitrate paint by David A. Siqueiros (-) is well documented, when and how he used it is not well established. This article focuses on a technical examination of six paintings Siqueiros made between  and . The paintings analyzed come from two collections: Museo Nacional de Arte in Mexico City and The Museum of Modern Art in New York. Findings presented here show that Siqueiros did not use cellulose nitrate for a painting he made in , despite having made that claim decades later. Rather, evidence indicates Siqueiros used it in Mexico City just prior to his trip to New York in  where he established a workshop to further explore innovation in painting technique and focus especially on ways to paint without a brush. Examination of a small work from  or  by Jackson Pollock (-), who attended the workshop, confirms he also experimented with the medium. Afterwards, in , Siqueiros again altered his technique and materials in a way to suggest that rendering specific details in his paintings was more important than being restricted to the innovative "brush-free" effects developed in the workshop.

The Grolier Codex has been a controversial document ever since its late discovery in 1965. Because of its rare iconographical content and its unknown origin, specialists are not keen to assure its authenticity that would set it amongst the other tree known Maya codes in the world (Dresden, Paris Codex and Madrid Codex).The document that has been kept in the Museo Nacional de Antropología in Mexico City, after its exposure in 1971 at the Grolier Club of New York, has been analyzed by a set of non-destructive techniques in order to characterize its materials including paper fibers, preparation layer and colors composition. The methodology included UV imaging, IR reflectography and optic microscopy examinations as well as Particle Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectrometry (RBS) using an external beam setup for elemental analysis. All the measurements were carried out at 3MV Pelletron Accelerator of the Instituto de Física, UNAM. The aim of this work is to verify if the materials in the Grolier Codex match those found for other pre-Hispanic documents.From the elemental composition we concluded that the preparation layer shows the presence of gypsum (CaSO4), color red is due to red hematite (Fe2O3) and black is a carbon-based ink. These results agree with previous analyses carried out by Scanning Electron Microscopy (SEM-EDX) on few samples. However, the presence of Maya Blue in the blue pigment cannot be assured. The examination using UV and IR lights shows homogeneity in the inks and red color but dark areas that contain higher amounts of K in the preparation layer. This paper discusses the results obtained for the UV-IR examinations and the elemental analysis. A comparison with other studies on pre-Hispanic and early colonial codex is presented.

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