Reading - Lighting the Lithopane
A lithophane or lithopane is an etched or molded artwork in thin very translucent porcelain that can only be seen clearly when back lit with a light source. It is a design or scene in intaglio that appears in gray tones.
A lithophane presents a three dimensional image - completely different from two dimensional engraving and daguereotypes that are "flat". The images change characteristics depending on the light source behind them. Window lithophane panel scenes change throughout the day depending upon the amount of sunlight. The varying lightsource is what makes lithophanes more interesting to the viewer than two dimensional pictures.
The word "lithophane" derives from Greek "litho", which is from "lithos" which means stone or rock, and "phainein" meaning "to cause to appear" or "to cause to appear suddenly". From this is derived a meaning for lithophane of "light in stone" or to "appear in stone" as the three dimensional image appears suddenly when lit with a back light source.
(taken from Wikipedia)