Linking Infrared Spectra of Laboratory Iron Gall Inks Based on Traditional Recipes with their Material Components

Abstract

The question for discriminating iron gall inks is addressed by correlating their infrared (IR) spectra in liquid and dried states with the materials used in their formulations and considering their possible interactions. A series of laboratory inks were prepared according to historic recipes, mainly found in 19th-century documents, and were accordingly studied using Fourier transform infrared (FT-IR) spectroscopy. All ink formulations were based on Aleppo galls, ferrous sulfate, and gum arabic at variable proportions, with various added components, such as alum, vinegar, glycerol, sugar, silver nitrate, cloves, and white wine. Ingredients of the corresponding inks were recognized by means of their IR fingerprints in both their liquid and dried states, respectively. Although a few inks of distinct formulations showed discernible differences in their spectra, the majority showed quite similar absorptions. Principal component analysis and discriminant analysis were employed to successfully discriminate inks, based on their IR peaks. Spectra recorded in the liquid state, despite their broad absorption features, led to satisfactory discrimination of certain types of inks as most of their ingredients are reflected in their IR peaks. Spectra from dried inks contained similar information, which equally worked in a sufficient discriminatory way. Key IR peaks in the recorded spectra of inks made with the addition of special ingredients, such as vinegar, wine, alum, glycerol, and sugar, as well as those prepared with specific tannin-enhancing procedures, such as gall boiling, were located and used in the discrimination basis.

Study of Iron Gall Inks, Ingredients and Paper Composition Using Non-Destructive Techniques

“…On the other hand, the group of aromatic ring vibrations in the range of 1600-1400 cm -1 is better resolved in the commercial powder than in the galls. The same behavior is observed for the absorption frequencies related to the vibration phenols groups, close to 1000 cm -1 , and for carbonyl groups in the range of 1670-1820 cm -1 [15,17].…”

“…The Arabic gum FTIR spectrum also shows the absorption connected with the vibrations of the OH-group and the characteristic stretching vibrations of the COOH and COO-groups (1630 cm -1 and 1413 cm -1 broad peaks, respectively). The stretching vibrations of the C-O group are also visible at 1072 cm -1 and 1023 cm -1 [17]. The presence of alkynes and/or nitriles compounds, possible as contaminants, is also detected through the peak and shoulder at 2400-2250 cm -1 .…”

“…All of them, jointly with the 1638 cm -1 peak, related to the stretching and bending vibrations of the OH-group, showing a high content of water. The sharp peaks at 1093, 989, 610 and 536 cm -1 are associated with the stretching vibrations both, symmetric and asymmetric, of the SO 4 2group [9,15,17].…”

“…Due to the uniqueness of these manuscripts, non-destructive analysis techniques are increasingly demanded to characterize them. Among them, X-ray fluorescence (XRF) and proton induced X-ray emission (PIXE) have been used to characterize the elemental composition of the inks and paper [2,[11][12][13], Fourier-transform infrared spectroscopy (FTIR) or Raman spectroscopy are also used to study the composition and structural characteristics [9,[14][15][16][17]. Mössbauer spectroscopy has also been used to measure the percentage of Fe(II) in dried inks [18,19].…”

Study of red-emitting LaAsO4:Eu3+ phosphor for color rendering index improvement of WLEDs with dual-layer remote phosphor geometry

“…Mie-scattering theory is used for the study of LaAsO4:Eu 3+ phosphor scattering effects and the computation of the scattering cross section Csca for spherical particles as expressed in the following expression [22,23]. Meanwhile, the Lambert-Beer law is used to compute the transmitted light power [24,25]:…”