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A basic recipe for making a Cr logwood ink dating to 1847 was adapted in order to obtain hues varying from orange to dark brown. The inks synthesized were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy, liquid chromatography-diode array detection-quadrupole time-of-flight-mass spectrometry, and liquid chromatography-inductively coupled plasma-mass spectrometry to gain insight into the spectroscopic properties of the compounds responsible for the inks colors and to obtain Raman spectra that can be used for their non-invasive identification in works of art and in historic documents. It was observed that hematein and logwood oxidation products are present in the inks and that their relative proportions determine the inks hues. It was also found that relatively small variations in the basic recipe, such as in the temperature that the logwood and K2CrO4 mixture were heated at, gave inks with different hues. The Raman spectra acquired in the laboratory samples were used to characterize the ink used by Vincent van Gogh in Street in Saintes-Maries-de-la-Mer. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Fe- and Fe/Cu-based logwood inks were synthesized following recipes in nineteenth and early twentieth century manuals and were characterized by EPR, ESI-MS, FTIR, and Raman spectroscopies. This multi-technique approach allowed us to shed light on the structures of the complexes responsible for the inks’ colors and to obtain vibrational signatures that can be used to identify the different inks in works of art and in historic documents. Information on the nature and chemical properties of the complexes formed between a dye and a mordant is important as these determine, at least in part, their lightfastness. EPR permitted to determine the coordination environment of the metallic ions. The results of the ESI-MS analysis demonstrated, for the first time, the breakdown of the hematein molecule during the ink preparation, and that the colorants are formed by the complexation of the metallic ions by hematein breakdown products, mainly catechol and/or bicyclic compounds. The FTIR spectra obtained were found to be dominated by bands due to the binding medium and sulfates used as reagents. The Raman analysis showed that the characteristic features for the different inks studied depend on the historic recipe used, attesting to the challenges that their identification and characterization in works of art present. In the Raman spectra of the inks applied on paper, broadening of bands in the 750–400 cm − 1 range are observed when compared to the spectra of the inks’ powders, possibly due to the interaction of the compounds with the cellulose in the substrate. [ABSTRACT FROM AUTHOR]