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

Round and ring-shaped abrasions and whitish islands were observed with a digital microscope in a degraded area of blue paint in Jan de Bray’s (1626/7–1697) Judith and Holofernes, 1659, a Dutch panel painting from the collection of the Rijksmuseum in Amsterdam. Although whitish islands have been previously reported as degradation deposits in ultramarine paint layers, it was unclear in this painting if the islands were remains of abraded paint, degradation deposits, or both. Non-invasive and micro-sampling techniques were used to study the materials and damage phenomena. Two blue pigments were identified in the blue blanket: indigo and ultramarine. The whitish islands were characterized as remnants of an abraded and degraded ultramarine paint layer used for the midtones and highlights on top of an indigo-containing blue-gray underlayer. The authors propose a possible mechanism for discoloration and damage to the ultramarine paint layer. Deposits of palmierite, a lead-potassium-sulfate compound, were also detected in the blue paint layers of the blanket but are not considered a significant component of the whitish islands. The likely presence of alum in the indigo may explain a UV-induced visible fluorescence observed in the indigo-containing paint layers. Ultimately, the results of the study were used to inform the retouching stage of treatment.

The study of organic colourants employed in artworks is a fundamental topic for history and conservation research; however, the most critical aspect in such matter arises from the necessity of sampling. Instead of binding media and inorganic components, natural organic colourants often exhibit weak signals during non-invasive analyses, which can be easily masked in complex mixtures, such as paint layers. To overcome this problem, the preferred approach is to take a sample, extract the colourants and analyse them using specific analytical techniques. The proposed method of direct agar gel-supported liquid extraction, performed using a Pasteur pipette tip, offers a promising solution to this challenge. By extracting colourants without the need for paint sample removal, it minimises visible impact on the artwork while still providing sufficient material for spectroscopic and mass spectrometric characterization. The experimental approach, which involved mock-up of mixing different organic and inorganic pigments with different binders and subjecting them to artificial ageing, simulates real-world complex matrices and assesses the effectiveness of the extraction method. Photomicrographs were used to document the procedure's visible impact. Mass spectrometry and surface-enhanced Raman scattering spectroscopy, the techniques of choice for invasive analysis of organic colourants, were used on the analytes extracted from the gel. The method application on paint patches from historical catalogues, housed in the Stiftung Preußischer Kulturbesitz collection, adds practical relevance to the study and demonstrates the applicability of the technique to authentic artworks. The procedure enabled the identification of natural and synthetic colourants without compromising the integrity of the paint systems.

In 1982, eight people—archaeologists, colour scientists and analysts—met in a room in King’s Manor, York University, to discuss a subject of significance to them all: the analysis of dyes on archaeological and historical textiles

Material analysis of a purported late sixteenth- to early seventeenth-century Italian doublet from the Fashion and Costume collection of the Kunstmuseum Den Haag in the Netherlands revealed discrepancies in its material composition, indicating a different timeframe. This paper summarizes research carried out on this doublet, initially identified as one of the earliest surviving complete doublets from the early seventeenth century. Through scientific material analysis (X-ray imaging, liquid chromatography (UHPLC-PDA-HMRS) and electron microscopy (SEM-EDX)) of the velvet, lining and the decorative elements, combined with an extensive literature review, the object as it is now was determined to have been likely constructed or transformed in the early nineteenth century. It may have originated as a woman's or man's doublet or made from original ciselé velvet for historical representations in theatres or masquerade festivities popular in the nineteenth century.