Glass
Flint Glass Prism by Fraunhofer, Inv. No. 579. Photo: Deutsches Museum
This prism Inv. No. 579 is made of flint glass, a glass with added lead. Consequently, flint glass exhibits a particularly strong chromatic dispersion.
Fraunhofer had been responsible for glass manufacturing at the "Optical Institute of Utzschneider, Reichenbach, and Fraunhofer" in Benediktbeuern since 1811. The challenge lay in producing glass that was as homogeneous as possible, free of bubbles or disruptive inclusions.
Special attention was paid to eliminating chromatic aberrations: because glass refracts different colors to varying degrees, looking through lenses resulted in distracting color fringes. This so-called chromatic aberration could be bypassed by cleverly combining two types of glass: flint glass with high chromatic dispersion and crown glass with lower chromatic dispersion.
