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From Green to Brown
Publication . Palomar, Teresa; Calatayud, David G.; Oujja, Mohamed; Maestro-Guijarro, Laura; Aparicio, Mario; Mosa, Jadra; Koppermann, Bettina; Seliger, Léonie; VICARTE - Vidro e Cerâmica para as Artes; Wiley | Wiley-VCH Verlag
In 2009–2014, new glass panels were produced by the Stained-Glass Studio of Canterbury Cathedral (UK) and installed in St Peter's Church (Little Barrington, Burford), St Lawrence's Church (Mereworth, Kent), and Canterbury Cathedral. After a few years, some spots and stains have appeared on the greenish areas of the panels. The common factor is that the panels were produced using the same green enamel. The present work reports on the studies of the observed alterations in green enamels to propose possible degradation mechanisms. These studies are based on using different analytical techniques such as optical microscopy, scanning electron microscopy energy dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, laser-induced breakdown spectroscopy, X-ray diffraction, µ-Raman spectroscopy, profilometry, X-ray photoelectron spectroscopy, and UV–vis spectroscopy. The characterization of the fragments from the original panels showed that a brown layer of dark lead compounds was formed on the green enamel. The alteration occurred in a 3-step alteration mechanism divided into Pb2+ lixiviation from the enamel, formation of hydrocerussite (2PbCO3·Pb(OH)2), and transformation into scrutinyite (α-PbO2) and plattnerite (β-PbO2).
The colour palette of 16th-18th century azulejos
Publication . Bandiera, Mario; Veronesi, Umberto; Manso, Marta; Ruivo, Andreia; Vilarigues, Márcia; Esteves, Lurdes; Pais, Alexandre; Coentro, Susana; VICARTE - Vidro e Cerâmica para as Artes; LIBPhys-UNL; DCR - Departamento de Conservação e Restauro; Elsevier
This work provides an overview of the pigments used by Portuguese azulejo painters through the study of 34 glazed tiles belonging to the National Azulejo Museum in Lisbon, Portugal. The tiles are dated from the late 16th century to the early 19th century, with most samples attributed to the 17th and 18th centuries. Building on a previous study where the chemical composition of the 17th-century colour palette was characterised [1], we used a non-invasive methodology to further identify compositional differences among groups of colours spanning a wider timeframe. Blue, white, yellow, orange, purple, green and brown decorations were analysed by EDXRF to obtain qualitative and (in some samples) quantitative information on their chemical composition. µ-Raman spectroscopy was used to identify the main colouring agents. Finally, colorimetric measurements of the different hues of each colour were performed to address the relation between colour and chemical composition. Our results show that greens could be obtained through a copper-based pigment or by mixing lead-antimonate with cobalt-blue pigment. Although cobalt is the colouring agent of all blue decorations, compositional differences suggest the use of different types of raw materials or the addition of specific reagents to modify the hue. On the other hand, yellow hues ranging from lemon yellow to orange were manufactured by adding zinc, tin, or iron oxide to a lead antimonate base. Finally, a manganese ore was used to make the purple pigment. Overall, we noted that while the basic pigments remained the same, the colour palette was progressively widened during the 18th century. This was done by using more pure pigments (i.e., with less iron), by changing the ratio in pigment mixtures (i.e., blue and yellow), or by overlapping colour layers for artistic effects. Finally, the results of the chemical and colorimetric analyses are always influenced by the concentration of the pigment in the glaze, its thickness and the overlapping of pigments used by azulejo painters to expand the shades available for the final artistic composition.
Preliminary results of the first archaeometric study of three medieval glass assemblages from Almada, Portugal
Publication . Cristoforetti, Anna; Medici, Teresa; Villamariz, Catarina; Alves, Luís C.; Coutinho, Inês; VICARTE - Vidro e Cerâmica para as Artes; DCR - Departamento de Conservação e Restauro; Associação Profissional de Conservadores-Restauradores de Portugal (ARP)
In the late 1990s and early 2010, archaeological excavations were conducted in three neighbouring streets of the old part of the city of Almada (Lisbon South bay), where medieval residential complexes were brought to light. Among the materials found in the Pátio Prior do Crato and Rua Latino Coelho, a group of glass fragments is dated between the 14th and 16th centuries. In addition, the glass assemblage of Rua da Judiaria counts more than 1,200 fragments covering a time span from the 12th to the 19th century, including some objects that have been identified as luxurious due to their decorations. This work integrates archaeological and archaeometric research and focuses on glass dating between the 14th and 16th centuries from these excavations in Almada. The combination of results intends to provide a first glimpse of glass usage and circulation in the southern area of Lisbon during the late medieval period.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
Concurso de avaliação no âmbito do Programa Plurianual de Financiamento de Unidades de I&D (2017/2018) - Financiamento Programático
Número da atribuição
UIDP/00729/2020