What Is a Lithophane? How the Backlit Image Works
Definition
A lithophane is a thin panel of translucent material whose thickness varies with an image: thick areas block light and appear dark, thin areas let light through and appear bright. The picture is only fully visible when the panel is lit from behind.
Also called: litho, backlit photo print.
Lithophanes began in 19th-century Europe as carved porcelain plaques set in windows and lamps. 3D printing revived them: a printer can vary thickness layer by layer, exactly what the technique needs.
How it works
Light passing through plastic dims as the plastic gets thicker. A lithophane maps the photo's dark areas to thick plastic and its bright areas to thin plastic. Unlit, it looks like a pale, textured panel. Lit from behind, the photo appears.
Making one
The image to STL tool builds flat and curved lithophanes in your browser. The full process, with settings and fixes, is in how to make a lithophane.
Lithophane vs filament painting
A lithophane is usually one color and needs light behind it. A filament painting stacks several colors and reads in normal light.
Questions
What material is best for printing lithophanes?
Plain white PLA is the standard choice. Matte or natural white gives an even glow; silk and colored filaments scatter light unevenly.
How thick should a lithophane be?
A common starting range is 0.8 mm for the brightest areas and 3 mm for the darkest, printed at 100 percent infill.