Set of Erotic Lithophanes

six extremely rare erotic lithophanes of French or German origin dating from around 1840, each image 4x5cm, all in perfect condition. Lithophanes are translucent panes of bisque porcelain with a die-impressed image on one side. When illuminated from the back they reveal a hidden picture. The density and character of lithophane images change with the amount of light passing through them. The process was invented and patented by Baron Paul Charles de Bourgoing in 1827. Although developed in France, the process was perfected in Prussia by the Königliche Porzellan-Manufaktur (Royal Porcelain Manufactory) in Berlin and soon became very popular. Most of the lithophanes of this time depicted fables, pastoral scenes and vedute - erotic images were extremely rare and are even harder to find today.