A multi-analytical study of historical coated plaster surfaces: the examination of a nineteenth-century V&A cast of a tombstone

Risdonne, Valentina, Hubbard, Charlotte, Puisto, Johanna and Theodorakopoulos, Charis (2021) A multi-analytical study of historical coated plaster surfaces: the examination of a nineteenth-century V&A cast of a tombstone. Heritage Science, 9. p. 70. ISSN 2050-7445

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Official URL: https://doi.org/10.1186/s40494-021-00533-0

Abstract

A multi-analytical study was designed to characterise historical coated plaster surfaces. The method was applied to investigate the surface coatings of the nineteenth-century plaster cast of the tombstone of the Presbyter Bruno that belongs to the Victoria and Albert Museum collection. At first, selected samples of the object were examined with Visible Light Reflectance and Ultra-Violet Fluorescence Optical Microscopy (VLR- and UVf-OM respectively) and Scanning Electron Microscopy (SEM) demonstrating a consistent stratigraphy featuring a bulk, an interface and an uppermost layer. The latter layer appeared to consist of an aged coating and dirt. Overpainted and repaired areas of the object generated samples that had additional layers on top of the aforementioned stratigraphy. A layer that seemed to be an additional surface varnish or a coating that had not been absorbed to the bulk has been observed in a couple of samples. Elemental characterization was carried out with energy dispersive X-ray spectroscopy (EDS) and further analyses were performed with X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy with focal plane array (FPA) imaging which confirmed that the bulk of the object is made of gypsum plaster containing mostly silicate and carbonate inclusions. Gas chromatography/mass spectrometry (GC/MS) and pyrolysis-GC/MS with extraction methods based on n-propanol followed by pentafluoropropionic anhydride (PFPA), tetramethylammonium hydroxide (TMAH) and 3-trifluoromethylphenyltrimethylammonium hydroxide (m-TFPTAH) were performed to detect organic media. The results suggest that the organic medium used for the surface coating is a diterpenic resin that contained silicon, aluminium and traces of other inorganic elements. The organic medium of overpainted areas was based on alkyd resins and the in-paints were characterised as a blend of silicon and barium at varied concentrations. This multi-analytical approach can generate a better understanding of manufacturing, component materials and conservation issues of coated plaster objects.

Item Type: Article
Additional Information: Funding information: This research was funded by the Art and Humanities Research Council (2017-21 AHRC/CDP Northumbria University and Victoria and Albert Museum - AH/R00322X/1) and supported by the Henry Moore Foundation (HMF Research and Travel Grant - 2018).
Subjects: F100 Chemistry
F400 Forensic and Archaeological Science
W700 Crafts
Department: Faculties > Arts, Design and Social Sciences > Arts
Depositing User: Elena Carlaw
Date Deposited: 11 May 2021 14:15
Last Modified: 23 Jun 2021 15:00
URI: http://nrl.northumbria.ac.uk/id/eprint/46139

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