CLASMAC: Congreso Latinoamericano de Arqueometría (CLA) y del Simposio Latinoamericano sobre Métodos Físicos y Químicos en Arqueología, Arte y Conservación del Patrimonio Cultural (LASMAC)

Caracterización e Imágenes de la Degradación uv del Carmín de Cochinilla

Caue Fereira - Instituto de Física, Universidad de Sao Paulo, Brasil - caue.ferreira@usp.br

A system (0.5 x 0,5 cm) formed by Canvas, Carmine Red and White Titanium (TiO2) + Linseed Oil (CCT) was degraded with the base being canvas, carmine red throughout the surface, and only half TiO2 + Oil.After drying, measurements were made in Atomic Force Microcospy(AFM) - Tapping Mode on both parts (Carmine and Ti), after approx. 18 days in the degradation chamber, the sample received approx 0.8 MegaJoule of UV radiation, and again measured in AFM - QNM Mode.We see that after degradation, the average height of the pigments (Titanium crystal and Carmine cluster) decreased by half of their height (124 nm to 77 nm for Ti and 20 nm to 6nm for Carmine), the surface became less rough, including revealing the fabric fibers. Something to note in carmine was also the formation of possible spherical clusters.This can show us, without damage to small samples, the potential of atomic force microscopy imaging and how the morphology since changes in the process, future investigations with other techniques being necessary , like SEM, SERS, etc.

  

Wood on Fire. Identification and analysis of particles adhering to archaeological charcoal through scanning electron microscopy

Maia del Rosario Rodriguez -CONICET - ARQAND -  maiadelrosario@hotmail.com

María Gabriela Aguirre - mgbaguirre@hotmail.com

Pilar Babot - CONICET - ARQAND - pilarbabot@csnat.unt.edu.ar

In Archaeobotany, optical microscopy -transmitted and reflected light, and scanning electron microscopy have become essential tools when carrying out the taxonomic identification of archaeobotanical remains and detecting features of a taphonomic nature. In the study of ancient charcoal that comes from archaeological sites, Anthracology, the use of microscopes has a long history, being initially an expensive and laborious tool (Badal García 1987-88) and currently, indispensable (Marguerie & Hunot 2007; McParland et al. 2010). In the 1970s, Vernet began to study charcoal by direct observations of carbonized material through the optical reflection microscope. This was a very important change in the methology for analysing anthracological remains (Badal García 1987-88), which was completed with the current use of the scanning electron microscope and the formation of experimental charcoal reference collections. The use of EDXS is less common in the study of archaeological charcoal (Vidal Matutano et al. 2019; Courty et al. 2020).

In our study area, which corresponds to Antofagasta de la Sierra in the Salty Puna of Argentina, the relationship between people and firewood is important due to the need to heat the living spaces in an extreme natural environment, to provide light and to allow food to be cooked. The wood fuel used has traditionally been supplied by plant species present in the low-sized shrubby flora typical of the high desert, while the lesser use of exotic firewood -at least from 150 km away, is still under study. Morphological traits of charcoal allowed to establish the collection of dead firewood from bushes that grow in the vicinity of the residential places and also the collection of fresh plants to be burnt for specific purposes –e.g. rituals, that grow in more distant places -approximately 10 km away.

In this work we present the results obtained on a series of elements detected in selected samples of ancient charcoal  which corresponnd to 9 plant taxa from several archaeological sites (6th to 20th centuries) through the use of SEM-EDXS Supra55VP (CIME, CONICET/UNT). The implementation of both techniques allowed the morphological and elemental characterization of the material studied, beyond the analysis of characters –structural and ultrastructural, that guide the precise taxonomic identification of the plants that were burned, and that allow the observation of the structural modification of wood due to the heat –e.g. vitrification process, Inclusions and particles adhering to the charcoal specimens were also identified. They include mainly hyphae and other fungal elements, followed in abundance by biomineralized particles -phytoliths and crystals, bacteria, ashes and other particles. We consider that the observation, registration and detailed compositional characterization of these types of elements present in the charcoal are useful to differentiate between the management of green or dead firewood, and to recognize residues of the processes and practices that were carried out in the combustion structures, as well as postdepositional aspects that affect the archaeological material –biodeterioration and others.