Probing some organic ukiyo-e Japanese pigments and mixtures using non-invasive and mobile infrared spectroscopies

Abstract

Non-invasive identification of organic colourants in paintings still remains a challenging issue, especially in the case of extremely thin layers of paint on printed paper such as Japanese ukiyo-e prints. Because prints are fragile artworks, various non-invasive analytical methods need to be employed. The present work focuses on results obtained by combining fibre optic reflectance spectroscopy in the near-infrared range (FORS NIR) with mid-infrared (MIR) spectroscopy. The first step consists of identifying spectroscopic marker bands typical of some organic pigments (indigo, gamboge, cochineal, turmeric, safflower, dragon's blood). Some reference printouts involving paper substrate, binder and pigments (seldom used or as mixtures) were then investigated in order to establish a straightforward way to extract the marker bands of the pigments. Some data post-treatments were applied to the spectra, such as spectral subtraction, in order to abstract the signal from overlapping bands originating from both substrate and binder, and second derivative calculation to emphasise the pigment marker bands' frequency positions. These data treatments turned out to be relevant to extract information on the organic pigments of interest, even within complex mixtures.

Evidence of early amorphous arsenic sulfide production and use in Edo period Japanese woodblock prints by Hokusai and Kunisada

“…We are not often allowed to sample from Japanese woodblock prints, therefore, non-invasive techniques such as fiber optic reflectance spectroscopy (FORS), excitation-emission matrix (EEM) fluorescence spectroscopy, X-ray fluorescence (XRF), infrared (IR) or Raman spectroscopy have often been preferred to study the materials used in prints [11,12,15,16]. Some of these techniques, namely FORS, XRF and Raman spectroscopy, were applied to the characterization of the color palette used in the selected prints.…”

A blue can conceal another! Noninvasive multispectroscopic analyses of mixtures of indigo and Prussian blue

“…Among the methods currently used by research teams to identify the pigments, spectroscopic techniques such as visible reflectance spectroscopy, infrared spectroscopy, and fluorimetry have been proven to be complementary, rapid, and noninvasive for the study of fragile artworks. 12,[19][20][21] In most cases, these techniques allow the identification of the coloring matters; however, they present some limitations. Fluorimetry needs the presence of fluorescence chromophores to be relevant and some fluorescence inhibitors can mask the signal such as iron-based components like ochre.…”

Characterisation of organic colourants in ukiyo-e prints by Fourier transform near infrared fibre optics reflectance spectroscopy

“…A pattern visible at about 5780 cm -1 is correlated to the first CH stretching overtones and the bands observed at 4330 cm -1 and 4250 cm -1 are due to CH stretching and CH bending combinations, which is consistent with the intense CH stretching mode measured in the mid-infrared spectrum. 1 The spectrum of cochineal is characterised by weak bands mainly at 6955 cm -1 [2ν(OH)], between 5900 cm -1 and 5600 cm -1 [2ν(CH)] and at 4330 cm -1 and 4260 cm -1 [ν(CH 2 ) + δ(CH 2 )]. 17 Gamboge and dragon's blood are complex mixtures of several molecules including chromophores such as gambogic acid and dracoflavilium ( Figure 2) as well as gum and/or resin components.…”

“…Regarding these issues and the various materials used through times, adapted analytical strategies using non-invasive and contactless methods have been developed to investigate painted artworks. [1][2][3][4][5] Infrared spectroscopy is a selective and sensitive method that is in principle able to evidence most of the materials used in paintings. Since the 2000s, infrared reflectance spectroscopy has been applied to the identification of pigments, dyes and binders using various Fourier Transform Infrared spectroscopy (FTIR) sampling techniques in the mid-infrared range.…”