Distinguishing between seemingly identical inks using scanning µXRF and heat maps

Abstract

• Stages of writing and correction can be identified thanks to material analysis. • Seemingly identical inks can be distinguished with use of imaging µXRF. • The application of XRF heat maps allows identification of altered portions of text. • Stratigraphy of seemingly identical materials can be unveiled by µXRF and heat maps. This study will present a new approach to distinguishing writing inks that have the same elemental compositions and visual appearances. The approach is based on displaying the intensity of elemental distributions as heat maps that represent data recorded with a scanning µX-ray fluorescence spectrometer. The heat maps present the data so as to facilitate digitally identifying and distinguishing between inks used to produce, correct, and reink two medieval Torah scrolls. As ritual objects, Torah scrolls had to be written in accordance with exacting standards that evolved over time. This requirement led to successive stages of modifications, sometimes over centuries. Both vitriolic and non-vitriolic inks used to modify Torah scrolls can be visually identical to each other. Furthermore, different non-vitriolic inks usually have an identical elemental composition. The solid material analysis evidence and its presentation as heat maps made it possible to discriminate between original and altered portions of text that in some cases would have been impossible. Our interdisciplinary work brought together conservation, material science, paleography, and philology to enable the identification of complex stratigraphy in multiple stages of production, correction, and reinking.