“Craquelure Anglaise: The development of film-formation defects in European 19th century oil paintings leading to paint failure and a loss of image integrity”

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Alligatoring: An investigation into paint failure and loss of image integrity in 19th century oil paintings

Publication . Marques, Raquel da Rocha; Carlyle, Leslie; De Viguerie, Laurence; Cardoso, Maria Isabel

"Alligatoring" or "Bitumen cracking" are terms used to describe extreme paint defects found in 19th century oil paintings. This paint failure in the form of severely disfiguring cracking and surface distor- tions often results in a loss of image integrity. This problem has been associated with the use of as- phalt/bitumen paint, with no clear understanding of the materials and mechanisms which contribute to the phenomenon. This thesis investigates this phenomenon from a multi-disciplinary approach that aims to con- tribute knowledge to the study of oil painting suffering from alligatoring. Part 1 focuses on the perception of the problem through a literature survey, and introduces the 19th century painting used in the case study. A thorough review of the literature showed the existing bias created by the perceived connection between appearance and cause, resulting in an association of paint film defects in brown paint with the use of asphalt/bitumen. Because of this, the overall focus of previous research has been the detection of asphalt, considering it in isolation and as the primary factor in the paint defect. This singular view has had significant implications in the study and analyses of paintings with alligatoring. It inhibited wider investigations and overlooked other materials present in the paintings that may be acting in combination or be more predominant in the deterioration mech- anism. The visual and chemical study of the oil painting O Cardeal D. Henrique recebendo a notícia da morte de D. Sebastião, by Marciano Henriques da Silva (1831-1873), painted in Rome in 1861, which exibits extreme alligatoring, offered specific challenges due to its complex and highly disrupted paint layer stratigraphy coupled with the uncertainty introduced by analytical detection limits. For that rea- son, a multi-analytical approach was carried out using Optical Microscopy, micro Raman Spectroscopy, Scanning Electron Microscopy with Energy Dispersive X-ray Spectrometry, X-ray Fluorescence, micro Fourier Transform Infrared Spectroscopy, Fourier Transform Raman Spectroscopy, Attenuated Total Reflection Fourier Transform Infrared Spectroscopy Microscopy, Pyrolysis-Tetramethylammonium Hy- droxide-Gas Chromatography/Mass Spectrometry and Time-of-Flight Secondary Ion Mass Spectrome- try. This research indicates that the deterioration of the painting might be related to the oil binder which has a high degree of oxidation, rich in polar fatty acids and diacids, combined with a lack of the xiv pigments that are capable of stabilizing the paint. The presence of the translucent lead azelate layer above the ground underlines the complexity of the paint layering, materials present, and possible mechanisms for degradation. Part 2 reports on new research carried out using the British colourman Winsor & Newton's 19th- century Archive Database to analyse their production records for “Bitumen” brown for oil tube paints. While there are a substantial number of published recipes in 19th century artist’s manuals for the use of asphalt/bitumen brown, for the first time W&N’s records offer a unique source of detailed infor- mation on the commercially prepared product which differs substantially in ingredients used and method of preparation. The critical analysis of W&N's production records for "Bitumen" revealed that their formulation became standardised in the 1850s and that their product was prepared in two sep- arate steps at two separate locations. Despite standarisation of the ingredients this research revealed that the company still found it necessary to make adjustments for each production run in order to achieve a uniform product. A production record from 1858 was selected and reconstructed, using where possible, histori- cally appropriate materials. W&N’s formulation for bitumen brown oil paint involved a complex mix- ture of ingredients, some of which were other proprietary products sold by the company (these were reconstructed individually using their production records and included drying oil, double mastic var- nish, lead acetate, purple lake and the gelled painter's Medium, megilp). The reconstructions were analysed using thermally assisted methylation with tetrame- thylammonium hydroxide, and pyrolysis comprehensive two-dimensional gas chromatography and compared with the starting material, Trinidad Lake asphalt, to determine how detectable this asphalt is after heat processing in lead treated linseed oil. Results show that asphalt markers identified in the Trinidad Lake asphalt disappear in the first stage of reconstructing W&N's "Bitumen" oil paint. This important finding offers an explanation for the paucity of analytical evidence in previous attempts to identify asphalt/bitumen in paintings where this material was believed to have been used. In addition to clarifying the analytical results obtained from the investigation of the painting, O Cardeal D. Henrique…, the reference samples produced from the W&N reconstruction illustrate the strengths and weaknesses of organic analysis of highly processed complex mixtures.

2023Tese de doutoramento

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Entidade financiadora

Fundação para a Ciência e a Tecnologia

Programa de financiamento

OE

Número da atribuição

PD/BD/135058/2017