Tracing the evolution of artists' materials and manufacturers' choices in painted magic lantern slides

Painted glass slides are fragile miniatures painted by hand on flat glass support to be projected with magic lanterns. Following the development of the magic lantern as the first optical instrument of projection in the mid-17th century, painted glass slides achieved the apogee of their production and use during the 18th and 19th centuries. Despite their widespread presence in collections and museums worldwide, the study of their materiality remains underexplored, posing challenges to their preservation.

This work investigates the colourants and binders used in 42 slides from Portuguese collections (Portuguese Cinematheque – Museum of Cinema and National Museum of Natural History and Science of the University of Lisbon) representative of the European production of the 18th and 19th centuries. A multi-analytical approach was employed, with minimal sampling restricted to paint areas detaching from the glass. Energy-dispersive X-ray fluorescence (EDXRF) spectrometry, Ultraviolet-Visible (UV–VIS) and Raman spectroscopies were favoured for in situ analysis, complemented by Fourier-transform infrared spectroscopy (FTIR) and Surface-Enhanced Raman spectroscopy (SERS) carried out on micro-samples. It was possible to detect the presence of mastic and shellac resins as binding components and to identify several colourants, including red ochre, cochineal-based lakes, geranium lakes, vermilion, yellow ochre, gamboge, Prussian blue, ultramarine blue, copper-green, and carbon-black, and fillers such as gypsum.

These results establish correlations between identified materials and historical sources, reflecting artists’ choices and evolving manufacturing practices. Distinct palettes and techniques were associated with manufacturers such as Philip Carpenter, Carpenter & Westley, W.E. & F. Newton, and Lapierre. The findings contribute to a deeper understanding of slide production techniques and support improved conservation strategies for these delicate and often overlooked heritage objects.