Liaisons dangereuses, conservation of modern and contemporary art: a study of the synthetic binding media in Portugal

Dissertação apresentada para obtenção do Grau de Doutor em Conservação e Restauro, especialidade de Ciências da Conservação, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaThis project is focused on the study of synthetic materials used by Portuguese artists in the twentieth century. The aim of the study was the molecular characterization of vinyl and acrylic polymers used since the 1960s and the study of their photodegradation and evolution over time. In modern and contemporary art, water based synthetic emulsions have been widely used as painting binding media, especially acrylic and vinyl based emulsions. In some countries like Portugal where the first aqueous emulsions used as paint binders were the poly(vinyl acetate) – PVAc – ones, both as household and artist’s paints, the study of vinyl polymers is of particular importance. In Portugal these emulsions were used by outstanding artists like Joaquim Rodrigo and Ângelo de Sousa since the 1960s. In order to guarantee the preservation of the artworks for the future generations it is essential to understand how these paints will behave upon ageing. The molecular photodegradation of PVAc was studied and the presence of degradation products on reference and model samples, as well as on dated artworks was investigated. Paintings by Joaquim Rodrigo and Ângelo de Sousa, and also a hand painted catalogue for the Sabu vinyl artists’ paints, were selected as case studies. The characterization of micro-samples from the artworks provided useful information on the real evolution of the polymer binder over time. Accelerated photodegradtion studies were performed by the exposure of PVAc films on an ageing chamber equipped with a xenon-arc lamp. The behaviour of PVAc (homopolymer) was compared with a commercial emulsion(Vulcano V7) and paint reconstructions prepared in the laboratory. The results achieved by means of infrared microspectroscopy (FTIR) point out the considerably stable nature of these binding media as no molecular evidence was obtained concerning the formation of other carbonyl functions, the disappearance of the PVAc carbonyl or the formation of hydroperoxides. The polymer photodegradation process was further studied by means of size exclusion chromatography (SEC), following the molecular weight distribution and correspondent average molecular weights. It was concluded that no side-chain reactions are taking place and that main-chain scission is the foremost degradation mechanism, although not affecting the polymer performance significantly. The influence of pigments, such as titanium dioxide and iron oxide, on the polymer’s stability was also considered and it was concluded that they do not promote degradation, which might be explained due to pigment encapsulation in inert materials inhibiting its photocatalytic behaviour. The photodegradation quantum yield was determined as 7.4 x 10-8 at 313 nm for PVAc homopolymer; therefore, degradation is quantified and comparisons may be performed for different polymers. A parallel study, according to a similar experimental approach, was undertaken on the stability of poly(methyl methacrylate) – PMMA – used as acrylic sheet by the Portuguese artist Lourdes Castro

The past and the future display of the slide-based artwork. Slides de Cavalete (1978-1979) by Ângelo de Sousa

Slides de Cavalete (1978-1979) is a slide-based artwork by the Portuguese artist Ângelo de Sousa (1938-2011). This paper explores issues related to the exhibition of Slides de Cavalete through the view of a conservator. In the absence of the artist, the display history of this work was traced with the aim of providing a base to substantiate the decision-making process of its exhibition and preservation. Published and unpublished documentation related to the exhibitions was consulted and personalities who could have witnessed the presentation of the artwork were interviewed. During this study it was understood that Ângelo de Sousa first presented the work projected on a canvas over an easel, for the exhibition A Fotografia como Arte/A Arte como Fotografia in 1979. In the two exhibitions carried out in 2017, the work was presented as a digital projection without the use of canvas and easel. This detachment from the first presentation, might have led to a misunderstanding of the work. Based on the conducted research and following the current procedures, display options for the exhibition of Slides de Cavalete are discussed.Slides de Cavalete (1978-1979) é uma obra de arte em suporte de diapositivos do artista português Ângelo de Sousa (1938-2011). Este texto explora questões relacionadas com a exposição de Slides de Cavalete através da perspetiva da conservação. Perante a ausência do artista, o presente artigo traça a história da exposição deste trabalho com o objetivo de fornecer uma base que possa auxiliar futuros processos de decisão, tanto em termos de montagem como de preservação da obra. Para tal, entrevistaram-se personalidades que testemunharam as apresentações anteriores deste trabalho e recorreu-se a documentação, publicada e inédita. Durante o estudo, percebemos que na primeira vez em que Ângelo de Sousa apresentou publicamente a obra, ela foi projetada numa tela sobre um cavalete, durante a exposição A Fotografia como Arte / A Arte como Fotografia em 1979. Já nas duas exposições realizadas em 2017, a obra foi apresentada como uma projeção digital sem qualquer recurso a tela ou cavalete. Consideramos que esta discrepância face à primeira apresentação pode conduzir a uma receção equívoca da obra. Com base na investigação desenvolvida, e respeitando procedimentos atualizados, este artigo discute possíveis opções de montagem numa futura apresentação de Slides de Cavalete.info:eu-repo/semantics/publishedVersio

Tracing poly(Vinyl acetate) emulsions by infrared and raman spectroscopies: Identification of spectral markers

Vinyl emulsions started to be used by artists in paintings at least since the early 1960s, being now present in several artworks worldwide. However, different vinyl formulations can result in distinct behaviours over time, and if some artworks are currently showing a good condition, others already show damages due to the use of compositions more susceptible to degradation. For this reason, it is fundamental to identify the main components in the vinyl acetate-based (VAc-based) emulsion. This work focuses on the molecular study of VAc-based emulsions by infrared and Raman spectroscopies. It aims at deepening the knowledge on the variability of the composite formulation and on the identification of characteristic bands and spectral profiles (identified as spectral markers) for both polymer and additives. To this end, a broad set of vinyl emulsions was gathered, including reference materials, historical commercial brands in use by Portuguese artists, and commercial brands collected from industrial companies. The entire set includes vinyl homopolymers produced for the purpose of the study and known formulations of vinyl homopolymers and copolymers, with and without plasticisers, according to technical data sheets and previous studies. Furthermore, unknown formulations have been included to validate the usefulness of the identified spectral markers. This set has been studied in the form of solid films deposited in glass slides by infrared spectroscopy in attenuated total reflection mode (ATR-FTIR) and micro-Raman spectroscopy (µ-Raman), both conducted in situ. As conclusions, the combined use of ATR-FTIR and µ-Raman proved to be very useful as different spectral markers were detected by each technique, confirming their complementarity. Besides the clear identification of vinyl acetate-based emulsions by both techniques, it was also possible to suggest spectral markers for the copolymerisation of vinyl acetate with vinyl versatate by µ-Raman, the stabilisation of the emulsion with poly(vinyl alcohol) by ATR-FTIR, and the addition of phthalates or benzoates plasticisers by both ATR-FTIR and µ-Raman.publishersversionpublishe

The role of optic nerve sheath ultrasonography in increased intracranial pressure: a systematic review and meta analysis

© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).Objectives: To review the optimal diagnostic cut-off of ultrasonographic optic nerve sheath diameter (ONSD) in the diagnosis of increased intracranial pressure (IICP). Methods: A systematic search was conducted of available studies assessing the use of ONSD ultrasonography in patients with suspected IICP. Meta-analysis of diagnostic accuracy of ultrasonographic ONSD was performed using a bivariate model of random effects to summarize pooled sensitivity and specificity. A summary receiver operating characteristics (SROC) curve was plotted. Accuracy measures associated with ONSD cut-off and predefined covariates were investigated with meta-regression. Results: We included 38 studies, comprising a total of 2824 patients. A total of 21 studies used invasive techniques as a reference standard estimation of IICP and meta-analysis revealed a pooled sensitivity of 0.90 (95% CI 0.85-0.93) and specificity of 0.87 (95% CI 0.80-0.91). Optimal ONSD cut-off values ranged between 4.1 mm and 7.2 mm. Meta-regression analysis showed that ONSD cut-off values of 5.6 to 6.3 mm were associated with higher pooled specificity compared to cut-off values of 4.9 to 5.5 mm (0.93, 95% CI 0.85-0.97 vs. 0.78, 95% CI 0.65-0.87; p = 0.036). Conclusions: Ultrasonography of ONSD shows a high diagnostic accuracy for IICP, with high pooled sensitivity and specificity. Additionally, larger cut-off values seem to significantly increase specificity without compromising sensitivity, which support their use as optimal ONSD cut-off. The overall high sensitivity of ultrasonographic ONSD suggests its usefulness as a screening tool for IIC, which may provide an estimate of when invasive methods are warranted. Clinical relevance: ONSD ultrasonography is a fast and cost-effective method with a high diagnostic accuracy to detect IICP. The optimum ONSD cut-off hasn't been established before, but we suggest the 5.6 to 6.3 mm range as the best for the diagnosis of IICP.DB has received funding from the Portuguese Foundation for Science and Technology [Fundação para a Ciência e Tecnologia – reference 2022.10667.BD] and Santa Casa da Misericórdia de Lisboa [Prémio João Lobo Antunes 2022].info:eu-repo/semantics/publishedVersio

Reproduction and testing of display options for the slide-based artwork slides de Cavalete (1978-1979) by Ângelo de Sousa: An Experimental Study

Funding Information: Funding: This research was supported by Fundação para a Ciência e Tecnologia, Ministério da Ciência, Tecnologia e Ensino Superior (FCT/MCTES), Portugal, through CORES Ph.D. Doctoral Programme in the Conservation and Restoration of Cultural Heritage with the doctoral grant (SFRH/BD/52317/2013).Slides de cavalete | Easel slides (1978-1979) is a slide-based artwork by the Portuguese artist Ângelo de Sousa (1938-2011), composed of one-hundred colour slides. Each image was produced by capturing different proportions of red, green, and blue (RGB) lights to obtain colour gradations. The artwork was first presented in the exhibition A Fotografia como Arte/A Arte como Fotografia | Photography as Art/Art as Photography in 1979. Associated with this exhibition, documentary evidence was found during the present study providing specific instruction on how to display the artwork (possibly unknown until now). According to that documentation, the artist wanted the work to be projected on a canvas mounted in an easel with a 19th century semblance, using a slide projector. In the last two exhibitions, carried out in 2017, after the artist had passed, the work was displayed as a digital projection, without the previously mentioned sculptural components. It was considered that this deviation from the first presentation could have led to a misunderstanding of the work. Thus, an exhibition of this artwork was prepared in a room at the Library of Faculdade de Ciências e Tecnologia. This was built as an experimental laboratory, having as one of its important objectives to test the variability of the work projected with a slide projector and a digital projector, following the display setup defined by the artist. For four days, the visitors were shown the work displayed under these two distinct scenarios of presentation. The visitors were also asked to fill out a questionnaire, to capture their perception about the variance of the work. The data obtained in the questionnaire and during the exhibition reinforced the decision to expose Slides de cavalete using the original technology. The public preferred the quality and beauty of the image using the slide projector, highlighting as positive aspects more granularity and warmer hue as well as higher depth of the images. Additionally, the production process behind Slides de cavalete was studied, based on documentation discovered in the artist’s archive and on reproductions, to enrich our perception of the work, in particular the complexity of creating the sfumato effects, and to understand the impact of changing the display technology. The results obtained made it possible to identify the main steps of making these slides, and this knowledge was shared with visitors in a workshop, integrated in this experimental laboratory.publishersversionpublishe

Characterization and long-term stability of historical PMMA: Impact of additives and acrylic sheet industrial production processes

SFRH/BD/52318/2013 IF/00653/2015 UIDB/50006/2020 UIDB/04349/2020This work aims at understanding the influence of the production processes and materials in the properties and long term behavior of acrylic sheet, i.e., poly(methyl methacrylate) (PMMA), a material generally considered very stable in museum collections. A comparative study was conducted in samples from cast acrylic sheets produced in the early 2000s, from which manufacturing details were known, and samples provided by the artist Lourdes Castro from acrylic sheets she had bought in the 1960s. Transparent and red opaque cast acrylic samples, containing cadmium red pigment, were used. All samples were artificially aged in a solarbox with irradiation Λ > 300 nm for a total period of 8000 h, and alterations were followed by a multi-analytical approach which included Raman, infrared (FTIR-ATR) and UV-Vis spectroscopies; gravimetry; size exclusion chromatography (SEC); thermogravimetry (TGA); micro-indentation; colorimetry; and optical microscopy. Not all cast PMMA sheets presented similar stabilities. We have concluded that the production processes (which may include the polymerization conditions, the organic additives and the origin of the monomer) play a more important role in the properties and long-term behavior of these acrylic sheets than the presence of cadmium red and/or the age of the material.publishersversionpublishe

Applicability of single-shot and double-shot Py-GC/MS for the detection of components in vinyl acetate-based emulsions used in modern-contemporary art

Funding Information: This work was co-funded by the research project ‘Plastic Paints in Art: the impact of manufacturing processes on their long-term stability’, financed by national funds from FCT/MCTES ( IF/00653/2015/CP1293/CT0005 as well as UIDB/50006/2020 , UIDB/00286/2020 , and UIDP/00286/2020 ). We would like to thank Anthony J. Baragona (Institute of Conservation and Restoration, University of Applied Arts, Vienna, Austria) for helping with the English corrections. Publisher Copyright: © 2022This research explores the use of different pyrolysis-based techniques for studying the chemical composition of vinyl acetate (VAc) based emulsions widely used in modern-contemporary art and contributes to the understanding of their composition by the detection of different monomers and additives. For this purpose, six different commercial VAc-based emulsions from the early 21st century were analyzed for the first time by single-shot (SS) and double-shot (DS) pyrolysis – gas chromatography / mass spectrometry (Py-GC/MS). The results obtained were compared, and highlight the advantages of DS in comparison to SS for the analysis of VAc-based emulsions. Several different components assigned to plasticizers, surfactants, intermediates, and antioxidant families, were detected, mainly by the thermal desorption step of DS. The information gained by this research enriches the knowledge of the formulation of VAc-based emulsions, by considering for the first time a large variety of them. Moreover, it also points to the importance and the potential of DS Py-GC/MS for investigating these materials, which have been rarely explored with this technique.publishersversionpublishe

Assessing the impact and suitability of dense carbon dioxide as a green solvent for the treatment of PMMA of historical value

Surface cleaning of plastic materials of historical value can be challenging due to the high risk of inducing detrimental effects and visual alterations. As a result, recent studies have focused on researching new approaches that might reduce the associated hazards and, at the same time, minimize the environmental impact by employing biodegradable and green materials. In this context, the present work investigates the effects and potential suitability of dense carbon dioxide (CO2) as an alternative and green solvent for cleaning plastic materials of historical value. The results of extensive trials with CO2 in different phases (supercritical, liquid, and vapor) and under various conditions (pressure, temperature, exposure, and depressurization time) are reported for new, transparent, thick poly(methyl methacrylate) (PMMA) samples. The impact of CO2 on the weight, the appearance of the samples (dimensions, color, gloss, and surface texture), and modifications to their physicochemical and mechanical properties were monitored via a multi-analytical approach that included optical microscopy, Raman and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopies, and micro-indentation (Vickers hardness). Results showed that CO2 induced undesirable and irreversible changes in PMMA samples (i.e., formation of fractures and stress-induced cracking, drastic decrease in the surface hardness of the samples), independent of the conditions used (i.e., temperature, pressure, CO2 phase, and exposure time)

Occurrence of non-toxic bioemulsifiers during polyhydroxyalkanoate production by Pseudomonas strains valorizing crude glycerol by-product

While screening for polyhydroxyalkanoate (PHA) producing strains, using glycerol rich byproduct as carbon source, it was observed that extracellular polymers were also secreted into the culture broth. The scope of this study was to characterize both intracellular and extracellular polymers, produced by Pseudomonas putida NRRL B 14875 and Pseudomonas chlororaphis DSM 50083, mostly focusing on those novel extracellular polymers. It was found that they fall into the class of bioemulsifiers (BE), as they showed excellent emulsion stability against different hydrocarbons/oils at various pH conditions, temperature and salinity concentrations. Cytotoxicity tests revealed that BE produced by P. chlororaphis inhibited the growth of highly pigmented human melanoma cells (MNT-1) by 50% at concentrations between 150-200 μg/mL, while no effect was observed on normal skin primary keratinocytes and melanocytes. This is the first study reporting mcl-PHA production by P. putida NRRL B-14785 and bioemulsifier production from both P. putida and P. chlororaphis strains

Primary adrenal insufficiency in adult population: a Portuguese multicentre study by the Adrenal Tumours Study Group

INTRODUCTION: Primary adrenal insufficiency (PAI) is a rare but severe and potentially life-threatening condition. No previous studies have characterized Portuguese patients with PAI. AIMS: To characterize the clinical presentation, diagnostic workup, treatment and follow-up of Portuguese patients with confirmed PAI. METHODS: This multicentre retrospective study examined PAI patients in 12 Portuguese hospitals. RESULTS: We investigated 278 patients with PAI (55.8% were females), with a mean age of 33.6±19.3 years at diagnosis. The most frequent presenting clinical features were asthenia (60.1%), mucocutaneous hyperpigmentation (55.0%) and weight loss (43.2%); 29.1% of the patients presented with adrenal crisis. Diagnosis was established by high plasma ACTH and low serum cortisol in most patients (43.9%). The most common etiology of PAI was autoimmune adrenalitis (61.0%). There were 38 idiopathic cases. Autoimmune comorbidities were found in 70% of the patients, the most frequent being autoimmune thyroiditis (60.7%) and type 1 diabetes mellitus (17.3%). Seventy-nine percent were treated with hydrocortisone (mean dose 26.3±8.3 mg/day) mostly in three (57.5%) or two (37.4%) daily doses. The remaining patients were treated with prednisolone (10.1%), dexamethasone (6.2%) and methylprednisolone (0.7%); 66.2% were also on fludrocortisone (median dose of 100 g/day). Since diagnosis, 33.5% of patients were hospitalized for disease decompensation. In the last appointment, 17.2% of patients had complaints (7.6% asthenia and 6.5% depression) and 9.7% had electrolyte disturbances. CONCLUSION: This is the first multicentre Portuguese study regarding PAI. The results emphasize the need for standardization in diagnostic tests and aetiological investigation and provide a framework for improving treatment.info:eu-repo/semantics/publishedVersio