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.

The starting point for this research was the requirement to produce replicas of Iron Age textiles from Hallstatt in Austria using traditional methods. Three traditional processing and dyeing methods using woad (Isatis tinctoria L.) were successfully recreated in an iterative experimental process: dyeing with fresh leaves, with green and couched woad and with woad pigment. During these experiments, several colours other than the typical blue also emerged. The light fastness of all colours was fairly good. Dye analysis using high-performance liquid chromatography with photo diode array detection (HPLC-PDA) showed that the most predominant component in the blue samples was indigotin. The colours mint, purple, beige and green were achieved when indirubin and flavonoids appeared in higher concentrations. The composition of the woad-related components detected on dyed samples enabled us to retrace the dyeing methods used. Antraquinones originating from madder (Rubia tinctorum L.) used in the madder–bran vat were also detected, but in different ratios to that of madder mordant dyeings. Further research is required to prove whether the components detected in reference samples can be used to identify woad dyeing or the use of madder–bran vats in historic/archaeological textiles. The ultraviolet–visible absorption spectra obtained by HPLC-PDA were used to calculate RGB values, which provide a better understanding of the colour observed