Lithophane

A lithophane is a thin plaque of translucent material, normally porcelain, which has been moulded to varying thickness, such that when lit from behind the different thicknesses show as different shades, forming an image. Only when lit from behind does the image display properly.^[2] They were invented in the 19th century and became very popular, typically for lampshades, nightlights, or to be hung on windows. They could also be given stands, to be placed in front of a light source.^[3] The longest side of a lithophane is typically between 6 and 10 in (15 and 25 cm).

The images tended to be artistically unadventurous, mostly repeating designs from prints, or paintings via reproductive prints. A large number were rather sentimental domestic genre scenes, though there were also portraits, landscapes and religious subjects.^[4] The technique naturally produced images only in grisaille, tones of grey, but later ones were often painted in translucent paint such as that used for watercolours to give colour images. The name comes from Greek; lithos means "stone," and phainen, means "to cause to appear".^[5]

Invented in France in the 1820s, they rapidly became popular and produced in various countries. But Germany soon became the main producer, remaining so for the rest of the century. The largest producer was the Prussian Königliche Porzellan-Manufaktur (KPM) in Berlin, leading to "Berlin transparencies" becoming a common term for them in English.^[6] The Plauesche Porzellanmanufaktur in Plaue, Thuringia, Germany, was another large manufacturer, who continued to make them into the second half of the 20th century.^[5]

Their peak of production was perhaps from about 1840 to 1870.^[5] By the end of the 19th century lithophanes had largely fallen from fashion, but in recent decades they have had something of a revival, using in addition to porcelain, glass, plastic, and with 3D printing sometimes paper.^[7]