Colours of deception? An investigation into historic Reeves watercolours

• First systematic study of suspected counterfeit Reeves watercolours. • Multi-technique analysis: FTIR, Raman, SEM–EDX, Orbitrap MS, PCA. • Dubious blocks show textual anomalies, unusual fillers, altered binders. • Evidence suggests counterfeit materials circulated in artist supply trade. • Findings reshape assumptions of authenticity in historic artworks. The authenticity of historical artist materials has long been a subject of interest in conservation and forensic studies yet formal investigations into counterfeit artist materials remain largely unexplored. This study investigated a set of watercolour blocks from the famous Reeves family, including samples suspected to be counterfeit due to inconsistencies in labelling. While historical records document fraudulent artist materials, no prior research has systematically analysed suspected counterfeit watercolours using advanced chemical techniques. The aim of this research was to determine whether the dubious Reeves & Sons watercolour blocks exhibit material discrepancies indicative of counterfeit. By comparing their composition with known historical formulations, deviations in pigments, binder content, and unexpected additives were assessed. A multi-technique analytical approach was employed incorporating physical separation, spectroscopy (FTIR, Raman and SEM-EDX), and high-resolution mass spectrometry (Orbitrap MS) to characterise organic and inorganic components. Principal Component Analysis (PCA) was used to detect patterns of formulation differences across samples. Of the eleven pigment blocks analysed, dimensional and textual inconsistencies, unusual filler compositions and deviations in material properties, such as gum composition, provided evidence that supports the interpretation that four blocks (F1, F2, F3, and F4) are likely fakes. Historical records confirm that similar counterfeits existed, reinforcing this conclusion. Additionally, control samples spanning over 150 years exhibit consistent and expected characteristics, further highlighting the anomalies in the dubious blocks. However, the possibility of undocumented manufacturing variations cannot be entirely dismissed. The findings stress the need for further research, particularly on binder composition and broader forensic methods for identifying forgeries across other artistic media, to refine authentication processes and ensure accurate historical documentation.