Magic lanterns were the earliest form of image projector that greatly impacted global socio-cultural and academic practices and has regained great interest today with the re-enactment and new production of magic lantern shows. With the simultaneous use of sounds, the magic lantern was an audio-visual communication medium with a high impact between the 17th to the 20th c..
The educational reforms in Portugal, formalised by the creation of the new Statutes of the University of Coimbra in 1772, constitute the first written source instructing the academic use of magic lanterns in the country. This document indicates that the Philosophical Course would integrate the fundamental knowledge of Experimental Physics, which included the magic lantern within the scope of the study of light, among other objects and instruments used in optics. It was in this context that in February of 1773, three magic lanterns and a set of 52 hand-painted slides, gathered in the Cabinet of Physics of the Royal College of Nobles of Lisbon, were transferred to the University of Coimbra, constituting the earliest collection of slides known in Portugal. These 52 slides attributed to Italy were inventoried in two groups, with one being attributed to the Venetian landscape painter Giuseppe Zais (1709-1781). In 1840, the University of Coimbra’s collection increased with the addition of 14 slides and a phantasmagoria lantern bought from the Parisian optician J.G.A. Chevallier.
Currently, the Museum of Science of the University of Coimbra holds 58 slides, 44 from the 18th c. and 14 from the 19th c.. From these, a selection of 20 slides was studied for the first time. The glass support and painting materials were characterised by resorting to a multi-analytical methodology using: Energy-Dispersive X-Ray Fluorescence spectrometry to identify glass composition and additives in organic lakes; Ultraviolet-Visible and Raman spectroscopies to the colourants identification; Fourier Transform Infrared spectroscopy to obtain information on binders, colourants, and additives. Furthermore, stereomicroscopy was used to observe painting characteristics, techniques and conservation issues.
The complementary use of these techniques carried out mostly in situ, provided valuable insight into the materials and techniques used in producing these slides and allowed for evaluating their state of preservation at a microscopic level. Correlations between coeval slides and also whit written historical sources on hand-painted slides' production and what is analytically found in historical slides has been established.