Animal species identification in parchments by light

Abstract

Recently, historical and conservation studies have attached an increasing importance to investigating the materials used in historic documents. In particular, the identification of the animal species from which parchments are made is of high importance and is currently performed by either genetic or proteomic methods. Here, we introduce an innovative, non-invasive optical method for identifying animal species based on light-parchment interaction. The method relies on conservation of light energy through reflection, transmission and absorption from the sample, as well as on statistical processing of the collected optical data. Measurements are performed from ultraviolet (UV) to near-infrared (NIR) spectral ranges by a standard spectrophotometer and data are processed by Principal Component Analysis (PCA). PCA data from modern parchments, made of sheep, calf and goat skins, are used as a database for PCA analysis of historical parchments. Using only the first two principal components (PCs), the method confirmed visual diagnostics about parchment appearance and aging, and was able to recognise the origin species of historical parchment of among database clusters. Furthermore, taking into account the whole set of PCs, species identification was achieved, with all results matching perfectly their proteomic counterparts used for method assessment. The validated method compares favourably with genetic and proteomic methods used for the same purpose. In addition to animals’ proteomic and genetic signatures, a unique “optical fingerprint” of the parchments’ origin species is revealed here. This new method is non-invasive, straightforward to implement, potentially cheap and accessible to scholars and conservators, with minimal training. In the context of cultural heritage, the method could help solving questions related to parchment production and, more generally, medieval writing production.

Recent developments in using the molecular decay dating method: a review

“…95 Red heat degradation of chrome-tanned leathers also depends on the same starting organism. 96 Alvarez et al 97 demonstrated the information content of an optical fingerprint of historical parchments. They were able to discriminate not only among different species but also among different manufacturers.…”

“…Red heat degradation of chrome‐tanned leathers also depends on the same starting organism 96 . Alvarez et al 97 . demonstrated the information content of an optical fingerprint of historical parchments.…”

Noninvasive quantitative assessment of collagen degradation in parchments by polarization-resolved SHG microscopy

“…Noninvasive approaches have been recently proposed for parchments, for instance, to identify the animal species ( 7 , 8 ). Regarding the degradation state, the current analytical techniques show some limitations.…”

Parchment characterization by multiphoton electron extraction spectrometry

“…A variety of techniques have been explored for characterization of parchments. These include laboratory analytical methods, such as inductively coupled plasma spectroscopy (ICP), ion chromatography, matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS), and several biomolecular techniques (Alvarez et al, 2019; Kirby et al, 2013; Teasdale et al, 2015). These techniques require complex sample pretreatments, handling procedures, and transport of the samples.…”

“…Almost nondestructive optical methods have also been utilized for parchments, including microscopy, Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy (especially synchronous fluorescence), Raman spectroscopy, laser induced breakdown spectroscopy (LIBS), and small-angle X-ray diffraction (Alvarez et al, 2019;Dolgin et al, 2007Dolgin et al, , 2009aKirby et al, 2013;Teasdale et al, 2015). For example, fluorescence and Raman spectroscopies had been used for the estimation of parchment deterioration.…”