An Introduction and Recent Advances in the Analytical Study of Early Synthetic Dyes and Organic Pigments in Cultural Heritage

Abstract

This article reviews the research recently undertaken to characterise and identify early synthetic dyes (ESDs) and synthetic organic pigments (SOPs) as well as study their degradation pathways with a focus on cultural heritage applications. Since the invention of the first fully synthetic dye in 1856, these materials have been used in a variety of historic objects and artworks, such as textiles, furniture, prints, paintings, drawings, etc. The synthesis of new dyes and their implementation into pigment formulations were rapid phenomena, so that by the beginning of the 20th century, thousands of new molecules were patented and commercialised. This review will focus on these early formulations synthesised up to approximately 1914 and the outbreak of World War I. ESDs and SOPs represent a challenge from an analytical point of view. Molecular databases are fundamental for the unequivocal identification of these compounds, but reference materials are not always readily available. A combination of analytical techniques is often needed for characterisation, especially in the case of SOPs, which have both organic and inorganic components. Furthermore, the degradation of these molecules can jeopardise their detection in historic objects that have been exposed to light, humidity and temperature fluctuations. Nevertheless, ESDs and SOPs are important research tools. As the dates of their first synthesis are often known with precision, based on patent information, their detection can be used to refine the production date of objects. Additionally, their trade from Europe to the world and their adoption in artistic practices around the globe is an active area of research.

Evaluation of Calcarenite Degradation by X-ray Photoelectron Spectroscopy Analysis inside the Rupestrian Church of San Pietro Barisano (Matera, Southern Italy)

“…To better understand the obtained results, other experiments carried out in the SCN_00152 project on related topics are considered together with data from the literature [17,18,[20][21][22][23][24].…”

“…In the wide field of material science [21], XPS provides surface composition at the nanometer scale, and its contribution is thus crucial in determining the surface-dependent properties of materials in various environments inducing corrosion, adhesion, catalysis, biological interactions, etc. Considering its analytical depth, XPS is often proposed for the analysis of layered samples, such as archaeological finds, pigments in paintings, etc., in combination with microscopy and spectroscopy techniques of different categories and depth of analysis to achieve multi-dimensional information from the valuable merging of data that mutually confirm the overall outcome [22,23].…”