Logwood Writing Inks: History, Production, Forensics, and Use

Abstract In the 16th century, the Spanish brought logwood from Mexico to Europe. Its extract was used for textile dyeing. The French introduced the logwood tree to Western Hispaniola, which became Haiti in 1804. Around 1880, Haiti exported most of its logwood to France. In 1847, Runge introduced the black chrome-logwood ink as an alternative for iron-gall ink, because the latter attacked the steel writing nibs. The most important constituents of logwood are hematoxylin and hematein. Due to the profitable import conditions from Haiti, chrome-logwood ink became the cheapest and most commonly used black writing ink in France. This could explain why Vincent van Gogh, during his French period, used it for writing and drawing and why most of the French postcards from the first half of the 20th century, studied in this publication, were written with chrome-logwood ink, while most of the Dutch postcards were written with an iron gall ink.</jats:p

Crystal violet: study of the photo-fading of an early synthetic dye in aqueous solution and on paper with HPLC-PDA, LCMS and FORS

The photo-fading of crystal violet (CV), one of the earliest synthetic dyes and an ink component, is examined both in solution and on paper. Aqueous solutions of CV were exposed to UV light (365nm) and samples were taken at constant time intervals and analysed with a High Performance Liquid Chromatography-Photo Diode Array (HPLC-PDA) and Liquid Chromatography-Mass Spectroscopy (LC-MS). Demethylation products were positively identified. Also, deamination probably occurred. The oxidation at the central carbon likely generates Michler\u2019s ketone (MK) or its derivatives, but still needs confirmation. To study CV on paper, Whatman paper was immersed in CV and exposed to UV light. Before and after different irradiation periods, reflectance spectra were recorded with Fibre Optic Reflectance Spectrophotometry (FORS). A decrease in CV concentration and a change in aggregation type for CV molecules upon irradiation was observed. Colorimetric L*a*b* values before and during irradiation were also measured. Also, CV was extracted from paper before and after different irradiation periods and analysed with HPLC-PDA. Photo-fading of CV on paper produced the same products as in solution, at least within the first 100 hours of irradiation. Finally, a photo-fading of CV in the presence of MK on Whatman paper was performed. It was demonstrated that MK both accelerates CV degradation and is consumed during the reaction. The degradation pathway identified in this work is suitable for explaining the photo/fading of other dyes belonging to the triarylmethane grou