Tortoiseshell or Polymer? Spectroscopic Analysis to Redefine a Purported Tortoiseshell Box with Gold Decorations as a Plastic Box with Brass

The study and preservation of museum collections requires complete knowledge and understanding of constituent materials that can be natural, synthetic, or semi-synthetic polymers. In former times, objects were incorporated in museum collections and classified solely by their appearance. New studies, prompted by severe degradation processes or conservation-restoration actions, help shed light on the materiality of objects that can contradict the original information or assumptions. The selected case study presented here is of a box dating from the beginning of the 20th century that belongs to the Portuguese National Ancient Art Museum. Museum curators classified it as a tortoiseshell box decorated with gold applications solely on the basis of visual inspection and the information provided by the donor. This box has visible signs of degradation with white veils, initially assumed to be the result of biological degradation of a proteinaceous matrix. This paper presents the methodological rationale behind this study and proposes a totally non-invasive methodology for the identification of polymeric materials in museum artifacts. The analysis of surface leachates using 1H and 13C nuclear magnetic resonance (NMR) complemented by in situ attenuated total reflection infrared spectroscopy (ATR FT-IR) allowed for full characterization of the object s substratum. The NMR technique unequivocally identified a great number of additives and ATR FT-IR provided information about the polymer structure and while also confirming the presence of additives. The pressure applied during ATR FT-IR spectroscopy did not cause any physical change in the structure of the material at the level of the surface (e.g., color, texture, brightness, etc.). In this study, variable pressure scanning electron microscopy (VP-SEM-EDS) was also used to obtain the elemental composition of the metallic decorations. Additionally, microbiologic and enzymatic assays were performed in order to identify the possible biofilm composition and understand the role of microorganisms in the biodeterioration process. Using these methodologies, the box was correctly identified as being made of cellulose acetate plastic with brass decorations and the white film was identified as being composed mainly of polymer exudates, namely sulphonamides and triphenyl phosphate.

Lithic economy and territory of Epipaleolithic hunter–gatherers in the Middle Tagus: The case of Pena d'Água (Portugal)

In Central Portugal (westernmost Eurasia) the transition from the traditional Pleistocene hunter–gatherer societies to the complex Mesolithic societies of the Holocene has been debated for decades. While some argue that these differences were a progressive phenomenon that started with the shift from the Pleistocene to the Holocene, others defend that the Late Pleistocene patterns were fairly similar to those of the Epipaleolithic and that the major shift was rapid, dramatic and triggered by the necessary adaptation to the 8.2 ka cal BP (8.09–8.25 ka cal BP) climatic event. The study of lithic raw material provenance might be useful for this discussion, since it has been suggested that the Magdalenian and Epipaleolithic populations from this region were collecting this resources within a close range territory, whereas the Mesolithic populations were acquiring them at longer distances. In this paper, we present the results from p-XRF, VP-SEM-EDS and μ-XRD analysis done on the Epipaleolithic lithic assemblage from Pena d'Água Rockshelter, and in some geological samples from secondary sources located ∼14 km from this site. This layer is of major relevance for this debate since it is dated from 8.19 ka cal BP. If the transition was gradual, it would be expected that this assemblage would show some traits of higher-complexity seen in the Mesolithic, namely of longer distance acquisition. However, our results indicate correspondence between the archaeological chert types and some of the geological sources. The differences seen between the archaeological specimens and geological samples are mostly present in traits that can be related with manufacture, handling and post-depositional phenomena. The results suggest that, in what concerns to the economy of abiotic resources, the Epipaleolithic populations living at the time of the dramatic 8.2 ka cal BP cold event, were performing a short range acquisition of lithic raw materials which reinforces the idea of continuity from the Late Pleistocene to the 8.2 ka cal BP event and an abrupt and dramatic shift soon after this phenomena.

Characterization of medieval glass artefacts from Miranduolo site, Chiusdino, Italy

This archaeovitreological study deals with artefacts of Miranduolo site, Tuscany region (Italy), dated 1250-1350 AD. The Miranduolo site is a medieval hill-village dated from 7th to 14th century. The information obtained reveal that Miranduolo was under control of noble families, which displayed the social, economic and political power. It is marked by controlling the farmers and metal workers on the site, as well as having control over agricultural surpluses. No in situ glass workshop has been recovered, implying that the glass artefacts were imported. One aim of this work is application of SEM-EDS to visualize textural characteristics and thickness of the pristine glass and corrosion layers. Preliminary qualification and semi-quantification of major and minor chemical elements will provide the data on the glass group present and fluxes employed. The data obtained will be integrated with the one obtained by more sensitive techniques such as PIXE/PIGE and LA-ICP-MS. Twenty cross-sections of transparent glasses (colorless, azure, and different hues of yellow and) have been analyzed by VP-SEM. All the analyzed glasses display a homogenous matrix. Only four samples (MD 24, MD 139, MD 143, MD 259) show corrosion layers of various thickness with 2.25μm, 136-500 μm, 26.8 μm and 17.01 μm. EDS linescan analyses indicate strong depletion in the corrosion layers of Na and K, while Ca depletes to a minor extent. In general, both glass composition and the burial conditions were favorable for preservation. Samples can be classified as mainly plant ash Na-Ca-Si glasses made with both unpurified and purified Levantine ash. Only sample MD 243 is made from Barilla plant ash. Sample MD 139 cannot be classified into main compositional groups as K2O is 1.33 wt% and MgO 5.92 wt%. In 8 samples MnO content is lower than 0.8 wt%, meaning that in these samples MnO is naturally present. In other 12 samples, MnO above 0.8 wt% indicates deliberate addition as a decolorant agent to intentionally obtain different hues or the amount added was not successful in making the glass transparent. The results considering fluxes are compatible with archaeovitreological study from contemporary primary glass workshops in Tuscany. For determining the provenance of silica sources, further analysis with more sensitive techniques has to be carried out; Resumo: Este estudo “arqueovitreologia” lida com artefatos do local Miranduolo, região da Toscana (Itália), datados de 1250-1350 AD. O sitio de Miranduolo é uma colina vila medieval datada do séc.VII ao séc.XIV. As informações obtidas revelam que Miranduolo estava sob o controle de famílias nobres, que exibiu o poder social, económico e político. É marcado por controlar os agricultores e trabalhadores do metal no sitio, bem como ter controlo sobre os excedentes agrícolas. Não há na oficina de vidro in situ foi recuperado, o que implica que os artefactos de vidro foram importados. Um dos objetivos deste trabalho é a aplicação de SEM-EDS para visualizar características de textura e espessura das camadas de corrosão do vidro também como da áreas originais. qualificação preliminar e semi-quantificação de maiores e menores elementos químicos irá fornecer os dados sobre o grupo presente vidro e fluxos empregado. Os dados obtidos são integrados com os dados obtidos por meio de técnicas mais sensíveis, como PIXE / PIGE e LA-ICP-MS. Vinte secções transversais de vidros transparentes (incolor, azul celeste, e diferentes tons de amarelo) foram analisados por VP-SEM. Todos os vidros analisados exibir uma matriz homogénea. Apenas quatro amostras (MD 24, MD 139, MD 143, MD 259) mostram camadas de corrosão de várias espessuras com 2.25μm, 136-500μm, 26,8μm e 17,01μm. Análises Linescan EDS indicam forte esgotamento nas camadas de corrosão de Na e K, enquanto Ca esgota, em menor grau. Em geral, tanto a composição de vidro e as condições de depósito foram favoráveis para a preservação. As amostras podem ser classificados como vidros principalmente Na-Ca-Si feitas com cinzas de plantas do tipo levantino, não purificada e purificada. Apenas a amostra MD 243 é feita a partir de cinzas vegetais tipo “Barilla”. A amostra MD 139 não pode ser classificada em grupos principais de composição porque K2O é 1,33% em peso e MgO 5,92% em peso. Em 8 amostras, o teor de MnO é menor do que 0,8% em peso, o que significa que nestas amostras MnO está naturalmente presente. Em outras 12 amostras, MnO acima de 0,8% em peso indica adição intencional como um agente de colorante para obter intencionalmente diferentes matizes ou o valor acrescentado não foi bem sucedido em fazer o vidro transparente. Os resultados, considerando os fluxos são compatíveis com o estudo “arqueovitreologico” com as principais oficinas de vidro contemporâneos na Toscana. Para determinar a origem das fontes de sílica, uma análise mais aprofundada com técnicas mais sensíveis tem de ser levada a cabo.