Preliminary Identification of Mixtures of Pigments Using the paletteR Package in R—The Case of Six Paintings by Andreina Rosa (1924–2019) from the International Gallery of Modern Art Ca’ Pesaro, Venice

Abstract

Frequently, the study of modern and contemporary paintings requires the taking of micro-samples to gain an in-depth understanding of the employed materials and techniques. However, since this procedure is characterized by its invasive nature, it must be carried out only if strictly necessary. This study aimed to evaluate the potentiality of K-means clustering to the corrected images of paintings to identify mixtures of pigments. This could assist in obtaining relevant preliminary information, facilitate the research process, and guide the sampling collection. Additionally, this method would be less expensive than the traditional multi-analytical approach as it would only require a modified digital camera, lenses, a color target and three computational resources for the processing of data (Imatest Master, Adobe Express—online, and R), out of which the latter two are freely available. The six paintings that have been selected for this study belong to the International Gallery of Modern Art Ca’ Pesaro in Venice (Italy) and have been depicted by Andreina Rosa (1924–2019), a Venetian artist. The artworks were thoroughly investigated mainly through non-invasive analytical techniques (FORS, RAMAN, ER-FTIR, EDXRF). Using cluster analysis, simulating mixtures, and calculating the color differences, it was possible to infer the existence of color mixtures of two/three detected primary colors from the examined images, which could be validated by the analytical results. Hence, it was concluded that samples taken from mixtures might suffice, since primary colors would be concomitantly analyzed.

Towards a More Sustainable and Less Invasive Approach for the Investigation of Modern and Contemporary Paintings

“…This study continues the research published in [20], which mainly focused on the identification of mixtures from the same six paintings of Andreina Rosa using the paletteR package in R. Here, the main aim is to present a better-optimized and user-friendly workflow for the extraction of colors from the corrected images of modern and contemporary paintings using two clustering methods, namely, K-means and Fuzzy C-means, the subsequent simulation of mixtures of the extracted primary colors, and the measurement of the color difference. The latter could emphasize the presence or the lack of pigment mixtures.…”

“…She preferred to use paints with a high tinting strength without applying varnish layers on her finished artworks. The six paintings that have been included in this study have been previously analyzed and, thus, similar to Guido Cadorin, and the presence or lack of mixtures was already known [19,20]. Their titles are Nudo Coricato (1948)(1949), Natura morta con lanterna (1950)(1951)(1952)(1953), Giulia con Michele (1954), Natura Morta (1954)(1955), Case sul lago (1954)(1955), and Variazione sul Tema Maiastra: Il Fiore per la Principessa (1989), and are also shown in Figure 1b.…”

“…The computational methodology was applied on the sixteen paintings by Guido Cadorin, Andreina Rosa, and Boris Brollo and the outcomes were confronted with the analytical results in order to validate it. This paper mainly presents the results obtained in the case of Boris Brollo as the materials that have been identified in the artworks of the other two Venetian artists had been already described in the previous publications [14,15,19,20]. In the case of Andreina Rosa, a comparison was required between the use of K-means clustering that was also employed in [20] and Fuzzy C-means clustering to check whether the latter performed better.…”

A Non-Invasive and Sustainable Characterization of Pigments in Wall Paintings: A Library of Apulian Colors

“…Differently, fiber optic reflectance spectroscopy (FORS) was widely applied in the colored surface characterization field, i.e., for the identification of pigments used in pictorial retouching [2], in manuscripts [3] and in modern and contemporary paintings [4,5], for the analysis of red chalk drawing [6], historical glass deterioration [7], dyestuffs in artistic textiles [8] and in wall paintings of artistic and archaeological sites [9][10][11]. Besides, it appears very useful to detect color changes connected to aging, pigment alteration and the presence of alteration products [12].…”

On Devotional Artworks: A Non-Invasive Characterization of Pigments of the Madonna della Croce Wall Painting in Triggiano (Bari, Southern Italy)

“…For the characterization of pigments in surface pictorial layers, in addition to the most common investigation techniques, including Raman spectroscopy and X-ray fluorescence spectroscopy, the current literature also provides numerous examples of the effectiveness of fibre optic reflectance spectroscopy [19][20][21][22][23], colorimetry [24][25][26] and portable digital microscopy [27][28][29].…”