Magic Lantern Glass Slides Materials and Techniques: the First Multi-Analytical Study

This paper presents the first systematic investigation of hand-painted magic lantern glass slides using multi-analytical techniques combined with a critical analysis of historical written sources of the painting materials and techniques used to produce them. The magic lantern was an optical instrument used from the seventeenth to the twentieth century that attained great success and impact on the entertainment industry, science, religion, and advertisement industry. The glass, colorants, and organic media of five magic lantern slides from the Museum of Natural History and Science of the University of Lisbon were studied. By means of energy-dispersive X-ray fluorescence spectrometry, the glass was characterized and the oxide quantification unveiled that the glass substrate was possibly produced between 1870 and 1930. Ultraviolet-Visible, Raman and Fourier transform infrared spectroscopies allowed the characterization of the colorants: Prussian blue, an anthraquinone red lake pigment of animal origin (such as cochineal), an unidentified organic yellow, and carbon black. The remaining colors were achieved through mixtures of the pure pigments. Infrared analysis detected a complex fingerprint in all colors, nevertheless, a terpenoid resin such as shellac was identified. Metal carboxylates were also detected, contributing to the assessment of the state of conservation of the paints.