The method of producing cast mirror glass was developed by the Frenchman Louis de Nehou around 1667 and used in the Hall of Mirrors in the Palace of Versailles.
The French King Louis XIV wanted a grand hall in the palace of Versailles featuring large windows and mirrors which created impressive reflections of light and strengthen his image as the Sun King. The Hall of Mirrors was built between 1678 and 1684. However, neither crown glass nor cylinder sheet glass could be buffed to give the even surface and gloss required for making the desired mirror gallery. Louis de Nehou therefore cast thick glass plates that could be ground and polished to perfection.
Cast mirror glass is made by pouring molten glass onto a casting table and smoothing it out with a heavy iron roller. It then undergoes a long, slow process in which it is ground with sand then polished with felt to achieve the required thickness and degree of fineness. The finished glass is very thick – but with almost uniform flatness and no optical distortions.