HERA was employed to analyze a stained glass window. Plates typically exhibit strong absorption bands located at well-defined wavelengths. Since window glass manufacturing has changed throughout time, spectral characterization is a means to determine the composition of glasses and of their coloring agents, to assess the authenticity of ancient windows.
Here a portion of an artistic glass window at Santo Spirito Church in Milan (Italy) was back-illuminated by natural sunlight, and the camera recorded the transmitted light. We observed that blue tiles exhibit different transmission spectra and can be separated into 5 classes. In particular, we identified two blue tiles with negligible infrared transmission.