Volume 45, Issue 2-3 - Special Issue: Non- and micro-invasive analyses to support the conservation of written heritage; Guest Editor: Federica Cappa

The effects of selected conservation treatments on brown inks have been investigated using inks prepared following historic recipes and applied to pure cellulose paper. Tests were carried out on both freshly prepared and on artificially preaged samples to enable the evaluation of the effects of ageing phenomena on the colour stability of the inks. The behaviour of the inks was studied by observation of changes occurring during treatment, accompanied by colorimetric measurements before and after the treatments. The goal of this study was to assess the risks posed to objects containing such inks by the selected treatments and to facilitate the design of safe treatment strategies for such objects.

A comprehensive study was conducted on four aged leather pieces of British origin that were utilized in book binding, dating back to the period between 1832 and 1860. The objective of this study was to characterize the thermal, structural, and deterioration properties of these historical leather fragments. Additionally, this study included two newly acquired leather samples of Indian provenance, proposed as potential replacements for this historical leather. The investigative process employed Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX). Through the FTIR analysis, distinct spectral shifts were identified in the amide A band, indicating a disruption of hydrogen bonding within the aged leather. XRD diffractograms revealed the presence of amorphous phases in the aged leather specimens, signifying the deterioration of their triple helical structure. Notably, DSC analysis provided insight into the denaturation of the collagen-tannin matrix inherent to the historical leather, underlining the transformative effects of time on this intricate material composition. Under SEM analysis, cracks, fibre deterioration, and a general weakening in structural integrity were observed in the aged leather fragments. The EDX data identified one of the new leather samples as chrome-tanned, while the remaining samples exhibited characteristics consistent with vegetable-tanned leather.

Material analysis was carried out on four manuscripts from Northern Thailand, which included two palm-leaf manuscripts and two paper manuscripts. The two palm-leaf manuscripts MS 6 and MS 7 were found to have been written in the traditional method, wherein text was incised on the surface of the leaves, and then soot applied to the surfaces, confirmed by the identification of carbon ink. MS 7 additionally showed the presence of trace levels of iron in the ink, either from soot paste or from the stylus used for inscribing. The paper manuscript MS 3 was written in iron-gall ink, with sections written using a methyl-violet based ink while MS 4 was written in carbon ink. The paper used in the case of MS 3 was found to be machine made, while khoi fibres ( Streblus asper ) were used for making the paper used for MS 4. A combination of traditional and modern pigments, like molybdenum orange, was used for decorating the edges and cover. The results improved our understanding of these manuscripts in particular, and also provided us with insights about the rapid adoption of modern materials and their incorporation into the production of written artefacts from Northern Thailand in the late 19th and early 20th centuries.

Implementing biomolecular techniques in the study of written cultural heritage has led to a steady development of biocodicology and the study of DNA and proteins in parchment in the past years. In this context, matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) has gained increasing attention as a powerful tool to study the ancient writing support. With a particular focus on the main components of parchment – different types of collagens – proteomic applications of the technique are highlighted. The review summarises advances in biocodicological studies focusing on manufacturing aspects and conservation treatments. Herein we further investigated proteomic studies on animal skin to prove the potential of MALDI-MS imaging (MALD-MSI) to broaden our knowledge and take studies on damage assessment and degradation of parchment to another level.

The Dagulf Psalter is a precious Carolingian manuscript on calf parchment, dated to 793–795. Its unique and high historical value required a non-invasive, multi-analytical approach to gain insights into the material composition of gold and silver inks, pigments, and dyes used for writing and illuminations. Elemental mapping based on X-ray fluorescence analysis (XRF), Fibre Optics Reflectance Spectroscopy (FORS) measurements, and hyperspectral imaging (HSI) gave complementary information on colour media and their brilliant shades. Knowledge of the material composition of inks, dyes, and pigments is of crucial importance not only for art historical research, but also for the preservation of the manuscript, as it is known that among other factors, silver inks and some pigments can lead to deterioration of parchment supports. The purple dye orchil and blue indigo were used for painted backgrounds on the initial folios. Lapis lazuli was found in decorative frames on these folios. Orchil, indigo, and lapis lazuli also appear in decorations of small initials throughout the manuscript. Red lead, ochre, cinnabar, orpiment, and lead white were also found in various painted details. Gold and silver inks of high purity were identified. The proof of chlorine in the silver ink indicates the presence of corrosion products.

Copper complexes, also called “copper soaps” when referred to carboxylate compounds, have become a concern in the conservation of historical artefacts. These complexes are suspected to play a significant role in degradation processes such as darkening and cracking of painting layers. Here we propose the Continuous Wave Electron Paramagnetic Resonance spectroscopy (CW-EPR) as a tool for the identification of these species. EPR spectroscopy is a micro-invasive and non-destructive technique that is highly sensitive to paramagnetic species, including radicals, crystal defects, and transition metal ions, e.g., Cu(II) and Fe(III). We have selected the verdigris (copper acetate) pigment combined with many organic binders, e.g., egg tempera and gum Arabic, as mock-up systems because of the known degradation tendency of the copper-based pigment. We would like to demonstrate that a precise analysis of the experimental spectra assisted with the calculus of the main magnetic quantities could lead to a good characterization of the copper complexes (or “soaps”).

Cyanotypes are known to de-colourize with alkalis; however, not much research has been done to regain the lost information. This research examines two possibilities to bring back the information: one is to utilize elemental mapping by X-ray fluorescence spectroscopy analysis to regain the image non-invasively, and the second, to treat the cyanotype with acidic solutions. Both methods brought back the image to the extent that the information could be obtained. As photo reproductions, one of their greatest values is the information they convey. This research could be significant in that it opens possibilities to regain the lost information.

Palm leaves are an important carrier for written heritage in southwest China, Tibet, and India. Due to the very nature of the material, many ancient palm leaf manuscripts are facing acidification and other types of degradation. Therefore, scientific research and conservation are of utmost importance. To study material properties and aging mechanisms of palm leaf manuscripts, their basic composition, physical and chemical properties, we studied infrared spectra, internal microstructure, and changes within the structure before and after aging of commonly used local talipot leaves. The results show that aging and deterioration of talipot leaves are mainly due to their acidic production process and high lignin content. The uneven distribution of longitudinal and transverse fiber bundles makes talipot leaves prone to longitudinal splitting. These findings provide important references for the conservation and long-term preservation of palm leaf manuscripts.

Influenced by the spreading route of Buddhism, palm leaf manuscripts in China are mostly distributed in Yunnan province and Tibet. The ink of palm leaf manuscripts from Yunnan province is left in the incisions, while the ink of palm leaf manuscripts from Tibet is written on the surface. The two inks have different compositions and application techniques, which may lead to varying degrees of flaking and ink loss. Application technique and ink composition are crucial for conservation measures. In this study, non-destructive analysis techniques including a portable digital microscope, Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF) were undertaken to analyse the characteristics and preservation condition of inks applied with different techniques on palm leaf manuscripts. Morphologies indicated that the interaction of ink and support influence the type and extent of ink loss. FTIR and XRF results showed significant differences in ink composition between incised palm leaf manuscripts from Yunnan and surface-written manuscripts from Tibet. Manuscripts from different periods within the same region exhibited similarities in ink composition. This paper significantly contributes to understanding properties of inks, offering an essential reference for ink consolidation.