Scientific Results

A multi-analytical approach to studying binding media in oil paintings Characterisation of differently pre-treated linseed oil by DE-MS, TG and GC/MS

Year: 2012

Authors: Bonaduce I., Carlyle L., Colombini M.P., Duce C., Ferrari C., Ribechini E., Selleri P., Tiné M.R.

Autors Affiliation: Dipartimento di Chimica e Chimica Ind., Via Risorgimento 35, Università di Pisa, Pisa, Italy;
Departamento de Conservação cao e Restauro, FCT/UNL, Campus de Caparica, 2829-516 Caparica, Portugal;
National Institute of Optics (INO) del CNR, Via G. Moruzzi 1,56124 Pisa, Italy

Abstract: This article presents a multi-analytical approach to investigating the drying, polymerisation and oxidative degradation of linseed oil, which had undergone various treatments known to be undertaken during the nineteenth century in preparation for painting. The oil was mechanically extracted from the same seed lot then processed by different methods: water washing, heat treatments, and the addition of driers, with and without heat. The oil was prepared in 1999 within the framework of the MOLART project. We compared thermogravimetric analysis (TG), which yields macromolecular information, with gas-chromatography mass-spectrometry (GC/MS) and direct exposure mass spectrometry (DE-MS), which provide molecular information. This comparison enabled us to elucidate the role of pre-treatment on the composition of the oil. TG and oxygen uptake curves registered at a constant temperature helped us to identify the different physical behaviour of the oil samples, thus highlighting the presence of hydrolysed, oxidised and crosslinked fractions, as a consequence of the different pre-treatments. GC/MS was used to characterise the soluble and non-polymeric fraction of the oil, to calculate the ratios of palmitic to stearic acid (P/S), and azelaic to palmitic acid (A/P), and to further evaluate the effects of oil pre-treatments. DE-MS using chemical ionisation with CH4, enabled us to establish the chemical composition of the oil in different stages of ageing. DE-MS proved to be a useful tool for a simultaneous semi-quantitative characterisation of the free fatty acids, monoglycerids, diglycerides and triglycerides present in each sample. The combination of thermal analysis with GC/MS and DE-MS enabled a model to be developed, which unravelled how oil pre-treatments produce binders with different physical-chemical qualities.

Journal/Review: JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY

Volume: 107 (3)      Pages from: 1055  to: 1066

More Information: Università di Bologna, UNIBO. – Acknowledgements The authors wish to thank Dr. Joyce H. Townsend of the Conservation Department, Tate, London, for her valuable input and her careful reading of the manuscript. Prof Rocco Mazzeo of the University of Bologna is gratefully acknowledged for the valuable discussion of the results.
KeyWords: DE-MS; GC/MS; Linseed oil; Oil pre-treatments; TG
DOI: 10.1007/s10973-011-1586-6

Citations: 19
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