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.

Visible-induced spectrofluorimetry as a non-invasive tool for the in situ identification of early synthetic dyes in cultural heritage objects dating back to the late 19th or early 20th century

“…Significant shifts in fluorescence maxima were observed in samples that underwent artificial ageing through light exposure, particularly in the case of rhodamine dyes (Figure 3), which contrasts with previously reported behavior for some of the most commonly used natural dyes [1]. Moreover, previous studies have demonstrated that the composition of a given dye can vary depending on the production technique, which has evolved over time in certain cases, such as with basic fuchsin [10]. Consequently, the modern version of this dye may contain different proportions of its components.…”

“…Finally, the same score plot reveals that the emission spectrum of the fuchsia silk sample closely matches that of the model dyed with magenta II, one of the original components of basic fuchsin. This early triarylmethane dye differs from its modern counterpart, which is now predominantly composed of new fuchsin (the tri-C-methylated form) [10], making the contemporary dye less similar to the historical sample. In this case as well, HPLC-MS analysis confirmed magenta II as the main dye present in the fuchsia silk of the statuette's robe.…”

Visible-induced spectrofluorimetry as a non-invasive tool for the in situ identification of early synthetic dyes in cultural heritage objects dating back to the late 19th or early 20th century

“…Significant shifts in fluorescence maxima were observed in samples that underwent artificial ageing through light exposure, particularly in the case of rhodamine dyes (Figure 3), which contrasts with previously reported behavior for some of the most commonly used natural dyes [1]. Moreover, previous studies have demonstrated that the composition of a given dye can vary depending on the production technique, which has evolved over time in certain cases, such as with basic fuchsin [10]. Consequently, the modern version of this dye may contain different proportions of its components.…”

“…Finally, the same score plot reveals that the emission spectrum of the fuchsia silk sample closely matches that of the model dyed with magenta II, one of the original components of basic fuchsin. This early triarylmethane dye differs from its modern counterpart, which is now predominantly composed of new fuchsin (the tri-C-methylated form) [10], making the contemporary dye less similar to the historical sample. In this case as well, HPLC-MS analysis confirmed magenta II as the main dye present in the fuchsia silk of the statuette's robe.…”

Chemistry of 19th-Century Swiss Postage Stamps

“…Minor signals, eluting earlier, were also observed, but their identities remain uncertain and could correspond to degradation or other debrominated products of the eosin Y dye. 41 , 42 …”

“…Minor signals, eluting earlier, were also observed, but their identities remain uncertain and could correspond to degradation or other debrominated products of the eosin Y dye. 41,42 Finally, the burgundy red 15C Cross and Numeral Zst 64B Raman spectrum shows peaks at 1668, 1566, 1479, 1326, 1291, 1161, 934, and 656 cm -1 (Figure S4d, Supplemental Material). While some peaks could indicate the presence of aromatic nitro group, no conclusive identification could be made.…”

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].…”

Visible-induced spectrofluorimetry as a non-invasive tool for the in situ identification of early synthetic dyes in cultural heritage objects dating back to the late 19th or early 20th century

“…Significant shifts in fluorescence maxima were observed in samples that underwent artificial ageing through light exposure, particularly in the case of rhodamine dyes (Figure 3), which contrasts with previously reported behavior for some of the most commonly used natural dyes [1]. Moreover, previous studies have demonstrated that the composition of a given dye can vary depending on the production technique, which has evolved over time in certain cases, such as with basic fuchsin [10]. Consequently, the modern version of this dye may contain different proportions of its components.…”

“…Finally, the same score plot reveals that the emission spectrum of the fuchsia silk sample closely matches that of the model dyed with magenta II, one of the original components of basic fuchsin. This early triarylmethane dye differs from its modern counterpart, which is now predominantly composed of new fuchsin (the tri-C-methylated form) [10], making the contemporary dye less similar to the historical sample. In this case as well, HPLC-MS analysis confirmed magenta II as the main dye present in the fuchsia silk of the statuette's robe.…”

Chemistry of 19th-Century Swiss Postage Stamps

“…Minor signals, eluting earlier, were also observed, but their identities remain uncertain and could correspond to degradation or other debrominated products of the eosin Y dye. 41 , 42 …”

“…Minor signals, eluting earlier, were also observed, but their identities remain uncertain and could correspond to degradation or other debrominated products of the eosin Y dye. 41,42 Finally, the burgundy red 15C Cross and Numeral Zst 64B Raman spectrum shows peaks at 1668, 1566, 1479, 1326, 1291, 1161, 934, and 656 cm -1 (Figure S4d, Supplemental Material). While some peaks could indicate the presence of aromatic nitro group, no conclusive identification could be made.…”

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].…”

Visible-induced spectrofluorimetry as a non-invasive tool for the in situ identification of early synthetic dyes in cultural heritage objects dating back to the late 19th or early 20th century

“…Significant shifts in fluorescence maxima were observed in samples that underwent artificial ageing through light exposure, particularly in the case of rhodamine dyes (Figure 3), which contrasts with previously reported behavior for some of the most commonly used natural dyes [1]. Moreover, previous studies have demonstrated that the composition of a given dye can vary depending on the production technique, which has evolved over time in certain cases, such as with basic fuchsin [10]. Consequently, the modern version of this dye may contain different proportions of its components.…”

“…Finally, the same score plot reveals that the emission spectrum of the fuchsia silk sample closely matches that of the model dyed with magenta II, one of the original components of basic fuchsin. This early triarylmethane dye differs from its modern counterpart, which is now predominantly composed of new fuchsin (the tri-C-methylated form) [10], making the contemporary dye less similar to the historical sample. In this case as well, HPLC-MS analysis confirmed magenta II as the main dye present in the fuchsia silk of the statuette's robe.…”

Chemistry of 19th-Century Swiss Postage Stamps

“…Minor signals, eluting earlier, were also observed, but their identities remain uncertain and could correspond to degradation or other debrominated products of the eosin Y dye. 41 , 42 …”

“…Minor signals, eluting earlier, were also observed, but their identities remain uncertain and could correspond to degradation or other debrominated products of the eosin Y dye. 41,42 Finally, the burgundy red 15C Cross and Numeral Zst 64B Raman spectrum shows peaks at 1668, 1566, 1479, 1326, 1291, 1161, 934, and 656 cm -1 (Figure S4d, Supplemental Material). While some peaks could indicate the presence of aromatic nitro group, no conclusive identification could be made.…”

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].…”