Through the limelight: Analysing the earliest collection of magic lantern glass slides in Portugal

Abstract The magic lantern, developed in the mid-17th century, was the first optical instrument for projecting transparent images - the magic lantern glass slides. It became a powerful tool for scientific and religious education, entertainment, and advertising throughout the 18th and 19th centuries. This study presents the first multi-analytical characterisation of 20 hand-painted glass slides from the historical collection of the Science Museum of the University of Coimbra (Portugal). A predominantly in situ approach combining Energy-Dispersive X-ray Fluorescence (EDXRF) and Ultraviolet-Visible (UV-VIS), complemented by Fourier Transform Infrared (FTIR) and Raman analysis of micro-samples. The results provide valuable insights into the painting materials and techniques used and allow for an assessment of their conservation state at the microscopic level. By identifying different glass compositional groups and colourants, this study establishes correlations with historical written sources and comparable European slides, contributing to a better understanding of artists' practices and supporting attribution and preservation decisions.