Abstract
A new analytical method was developed to non-destructively determine pH and degree of polymerisation (DP) of cellulose in fibres in 19th–20th century painting canvases, and to identify the fibre type: cotton, linen, hemp, ramie or jute. The method is based on NIR spectroscopy and multivariate data analysis, while for calibration and validation a reference collection of 199 historical canvas samples was used. The reference collection was analysed destructively using microscopy and chemical analytical methods. Partial least squares regression was used to build quantitative methods to determine pH and DP, and linear discriminant analysis was used to determine the fibre type. To interpret the obtained chemical information, an expert assessment panel developed a categorisation system to discriminate between canvases that may not be fit to withstand excessive mechanical stress, e.g. transportation. The limiting DP for this category was found to be 600. With the new method and categorisation system, canvases of 12 Dalí paintings from the Fundació Gala-Salvador Dalí (Figueres, Spain) were non-destructively analysed for pH, DP and fibre type, and their fitness determined, which informs conservation recommendations. The study demonstrates that collection-wide canvas condition surveys can be performed efficiently and non-destructively, which could significantly improve collection management.
Highlights
Salvador Dalı i Domenech (1904–1989 Figueres, Spain) is probably the best known surrealist painter
NIR spectra of cellulosic materials have been discussed in several publications[14,33] and the spectra of painting canvases show the same features as discussed in previous studies
In order to develop a non-destructive NIR method, a reliable set of analytical data obtained on reference canvas samples similar to the unknowns (Dalı paintings) was required
Summary
Salvador Dalı i Domenech (1904–1989 Figueres, Spain) is probably the best known surrealist painter. It is well recognised that his world was continuously in uenced by contemporary scienti c thinking, and his fascination with science is well documented in paintings such as Galacidalacidesoxyribonucleicacid (1963), known as Homage to Crick and Watson (Discoverers of DNA). It is perhaps be tting that his paintings are subjected to scienti c analysis beyond the paint surface. The purpose of this work was to look at what the reverse of the paintings can reveal about the works of art. Due to the desire and pressure to exhibit iconic works of art, their material state and tness to withstand handling and travel needs to be assessed.
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