Tangible facets of the art of painting glass slides for projection by magic lanterns
 
M. Vilarigues, V. Otero, A. Ruivo, C. Machado
 
 
Magic lantern is a central element of the history of the projection of images for mass media. It changed the face of educational and religious lectures, social gatherings and popular entertainment shows from the 17th c. to the 20th c. With the projection of images and the synchronised use of sounds, the magic lantern became the most impacting form of communication until cinema, with glass slides as the fundamental support of the images. Magic lantern glass slides are fragile items and most of those preserved today are part of the production lines of the end of the 19th c. and the beginning of the 20th c. manufactured with printing or photographic techniques. The hand-made slides from the 18th and 19th c. and of the beginnings of the magic lantern in the 17th c., are much rarer and their value is easier recognisable.
 
With this work we aim to establish a methodology that covers the characterisation of the glass substrate, paint composition and application techniques with in situ analytical techniques. The materials of the historical hand-painted and hand-coloured glass slides will be characterised in terms of the chemical composition of glass and paints and techniques of production. A multi-analytical approach based on complementary analytical techniques, namely Energy-Dispersive X-ray Fluorescence Spectrometry, Optical Microscopy and Ultraviolet-Visible and Raman Spectroscopies, has been adopted to characterise hand-painted slides from the collection of Cinemateca Portuguesa - Museu do Cinema, from the English producer W.C. Hughes, dated from the last quarter of 19th c. The optimisation of the in situ methodology is crucial when studying such fragile objects, particularly for these slides, as their paint layer is found between two glass slides, making it inaccessible to micro-sample. It was possible to identify painting materials advised in manuals on how to paint magic lanterns slide, in particular the one by Groom (1855, England), published in the same period of the production of these slides.
 
The information obtained from the material characterisation allows to clarify the production process of the hand-painted glass slides. The written manuals alone do not explain technological choices in full; the fraction of technical knowledge that people can verbalise is limited and does not include the practices that may have been used to respond to the concrete challenges of the materials, such as adhesion of the paint, search to achieve highly detailed drawings, transparent and bright colours. Ultimately, the historical object itself is the physical evidence of what was accomplished by the maker.