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DIAGNOSIS OF MURAL PAINTINGS - THE CASE OF THE MARITIME STATIONS OF ALCÂNTARA

Diagnosis is a fundamental step to be considered prior to any conservation and restoration intervention. In order to be able to preserve artworks in the best possible way, it is necessary to know the original materials used, to understand how they age (and deteriorate), to identify the mechanisms and sources of decay in order to proceed to their mitigation. This is one of the goals of project ALMADA, which has a multidisciplinary team made up of conservators-restorers and Heritage Science researchers.

Almada's wall paintings dating back to the first half of the 20th century have already undergone total or occasional conservation and restoration treatments. The series of wall paintings at the two maritime stations of Alcântara, in Lisbon, are among the most documented cases at this level, perhaps due to their monumentality, artistic, and historical importance.

From 1971 to 2000, reports from the inspection and mural painting work campaigns of José de Figueiredo Institute (IJF) gave an idea of the anomalies present and their recurrence over the years. As already reported in Newsletter 7, it is with this Institute, still a reference in the field of conservation and restoration in Portugal, that interventions in these pictorial nuclei began after the artist's death in 1970.

As of 2020, the research team of the ALMADA project, and its collaborators, began to climb the scaffolding to get to know the murals up close together with students (Fig.1). Between 2020 and 2022, several analytical campaigns were carried out at the two stations, approximately 1.5 km apart, with the aim of mapping the main forms of alteration currently visible and identifying the underlying causes with a view to implementing future conservation and restoration measures.

Figure 1. Three phases of fieldwork undertaken from 2020 to 2021. From left to right: observation in raking light, portable optical microscopy of paint layers, and survey of structural elements on the roof of the Maritime Station of Rocha do Conde de Óbidos. Image MGil2023-Project ALMADA ©. All rights reserved.
 

The research activities encompassed the identification and characterization of the main deterioration features attaining the paint layers by visual inspection, technical photography in the Vis, Vis-Rak, and UV; h-OM and h-EDXRF, complemented at Hercules laboratory by OM, XRD, FTIR, and SEM-EDS of the microsamples.
Moreover, the identification of structural anomalies, as well as the validation of existing documentation regarding geometry and structural elements, were also carried out. This study was carried out by the Department of Civil Engineering of the University of Minho under the responsibility of Alberto Barontini.To this end, widespread sample measurements were taken, and a detailed photogrammetric survey of the most deteriorated parts of the building at Rocha do Conde de Óbidos was conducted. Nondestructive evaluation strategies were applied to support this research, particularly thermographic inspection (Fig.2).

The results show that the mean deterioration features found in both painting sets are flaking and powdering of paint layers (Fig.2). The colors that are most affected are light greens, yellows, browns, and blacks made with natural and different types of synthetic pigments (eg. Green Earth, Fe, Cr, and Cd-based pigments and PG’s). The occurrence and activity of gypsum and other sulfates found on the paint surface and underneath mortars can be highlighted as the main decay phenomena. The poor condition of the structural elements, the original building materials, and the past building repairs, combined with a particularly aggressive external environment (e.g., air traffic pollution, sea spray), are the likely sources of water infiltration and sulfate present on the paint structure.

The geographic location of the two stations on the Lisbon riverside is of added concern, given the forecasts of worsening weather conditions for the coming decades. Future analyses of humidity and temperature parameters, as well as measurements of the amount of incident solar radiation, will provide a more concrete view of the impact on the deterioration mechanisms that are still active.

 Figure 2. Details of the 1971 intervention and tests carried out with adhesives at the Maritime Station of Rocha do Conde de Óbidos. Image Inês Cardoso2023-Projeto ALMADA ©. All rights reserved.

The field work produced alerts about the poor condition of some of the paint layers, leading to an SOS intervention on one of the murals at the Maritime Station Alcântara in 2021. The results would also contribute to the success of the candidacy presented by the Administration of the Port of Lisbon (APL) to the Word Monuments Fund in 2022, with the aim of safeguarding and enhancing this cultural heritage.

However, for the future conservation of these murals, in addition to information about the original materials, it is important to know the products used in past interventions and determine their behavior almost five decades after the first intervention held by the IJF (Fig.3 and Fig.4).
 

Going to backstage

Rubric showing the ongoing scientific research and participants
Diagnosis

Photo: Graphic documentation of the state of conservation of the paintings at the Maritime Station of Rocha do Conde de Óbidos. In the photo, Verónica Martinez Quiceno and Youssef Mohamed A.M., Archmat Erasmus Master Mundus students in Archaeometry- University of Évora, Portugal (2021-2023 edition). MGil2023- Project ALMADA© all rights reserved.