4 Material und Umwelt
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The earliest known recipes for iron gall inks include four basic ingredients: oak galls – pathological growths of oak leaves; metal salts – usually referred to as vitriol; a binder such as gum Arabic; and water. The final product differs in the elemental composition due to the multitude of recipes as well as differences within the composition of the ink’s ingredients. Nowadays, based on the qualitative and semi-quantitative evaluation of X-ray fluorescence data, it is possible to distinguish inks on the basis of the so-called fingerprint model. The first goal of our study was to determine to what extent the type of XRF spectrometer affects the quality of the ink evaluation. We tested two types of spectrometers, semi-stationary machines equipped with polycapillary focusing optics and a handheld spectrometer with a diaphragm collimator and a relatively big interaction spot.
The second goal was to address the issue of whether the ink composition might be affected by storage in a metal container. The presentation will discuss the role of the spectrometer type in the evaluation of a thin layer material such as ink.
We have also learned that the iron-gall ink composition might depend on the type of vessel in which ink was being stored.
While studying the socio-geographic history of inks, division 4.5 of the BAM (Bundesanstalt für Materialforschung und Prüfung) together with the Centre for the Study of Manuscript Cultures in Hamburg has developed a protocol for ink analysis.
It consists of a primary screening to determine the type of the ink, and a subsequent in-depth analysis using several spectroscopic techniques. The XRF elemental analysis aims primarily at identifying and characterizing metallic components of inks. Besides the instrumental methods, the paper presents an overview of historic inks in the period of transition from carbon inks of the Antiquity to iron-gall inks commonly used in the Middle Ages.
In the recent years multispectral imaging and X-ray Fluorescence element mapping have established themselves as a well working two step approach, when dealing with faded, erased or overwritten text in iron gall ink. During the last years a lot was done to improve the mere technical side of the techniques. Especially in the case of XRF mapping experiments the acquisition speed needed to be increased to allow mapping in the high resolution demanded by the challenges at hand. High resolution in moderate times can now be achieved, but with the price of proportionally increased amount of data that needs to be processed ideally in parallel to the measurement. The classical approach in XRF spectroscopy of elemental fitting of the spectral data does not even come close to fulfill any on the fly processing time constraints and will consume too much processing time in the foreseeable future. In this paper we will discuss the applicability of modern statistical data processing methods to XRF mapping of iron gall ink palimpsests. We will present a comparison of a new approach based on principle and independent component analysis (PCA and ICA) and the standard element mapping method. We will show that a reduction in processing time of almost two orders of magnitude can easily be achieved.
Our research aims primarily at recreating a socio-geographic history of inks, parchment, and papyrus and includes the comparative analysis of the writing materials of the Dead Sea Scrolls, ink and papyrus in Ancient and Hellenistic Egypt, and inks in documents from various contemporary medieval communities in Fustat (first nucleus of Cairo) as well as other medieval Jewish and Armenian communities.
The presentation shows the panorama of historic inks and our attempt to follow up the transition of the inks from those based on soot to the iron-gall inks commonly used in the Middle Age.
X-ray fluorescence analysis, due to its non-destructive nature and ist suitability to work with historic objects in situ, quickly became one of the most important methods for the evaluation of iron-gall ink. The main advantage of this qualitative and semi-quantitative method is that it makes it easy to differentiate between inks, based on the assumption that the differences result from the manufacture of the ink.
This work explores the question whether the ink ‘fingerprint’ results strictly from the elemental composition of the basic ink ingredients even if it is stored in vessels made of metals or metal alloys. In addition, we tested and compared the performance of three different XRF spectrometers.
We prepared various lab-grade inks according to historical ink recipes and measured the metal content of the ink deposited on sized cotton Linters paper with three types of XRF spectrometers: a simple hand-held device with an interaction spot of 4 mm and two devices equipped with poly-capillary Xray optics for line scanning and imaging. Since the exact elemental mass composition of the non-aged ink samples was known, we were able to evaluate the accuracy of the research procedure. Lab-grade inks were then aged in the metal jars imitating inkwells. The aging of the inks in the metal containers resulted in the significant change of the primary inks fingerprint as opposed to that of the control inks stored in glass containers. This effect was independently confirmed by the measurements conducted with every instrument we used. We will present a brief comparison of the results 43 achieved when using different spectrometers and a possible hypothesis explaining the processes that occurred.