Mineral painting

Mineral painting or Keim's process, also known as stereochromy, is a mural or fresco painting technique that uses a water glass-based paint to maximize the lifetime of the finished work.
The name "stereochromy" was first used in about 1825 by Johann Nepomuk von Fuchs and Schlotthaurer. In the original technique, pigments were applied to plaster or stone and sealed with water glass to preserve and enhance the colors. The method was then improved in the 1880s by Adolf Wilhelm Keim and renamed mineral painting or Keim's process.
Keim's process.
Keim's process was reported in 1884 at the Royal Society of Arts in London, by chemist and craftsman Adolf Wilhelm Keim of Munich, as an improvement on the earlier stereochromy technique of Schlotthaner and von Fuchs.
The process.
Keim's focus on carefully preparing the painting ground came from his study of older frescos and their state of preservation. Keim reportedly labored for twelve years to refine his process.