The key part of the aesthetic of lithophanes is how they’re lit. There are loads of options for this – some people turn them into lampshades, some mount them in back-lit frames. We wanted a small, evenly lit option to add the image of our unborn child to our workshop, and we came across the ideal solution in the form of LCD back-lights. These are designed to go behind LCDs and provide illumination. They should give even light across a rectangular area, and some electronics suppliers sell them. The downside of these is that they only come in the sizes of common LCDs – these tend to be a bit longer and thinner than most photographs, but are perfect for images of reclining foetuses.
We got an 84 × 45 mm light, so all we needed to do was crop our image to the same aspect resolution as this, then upload the image to a lithophane generator. There are a few available online, but we used the one at 3dp.rocks/lithophane. This provides some options of different shapes that might be useful if you’re trying to use your lithophane in different ways, but we went with just a flat lithophane.
This generates an STL file that we can import into our slicer as with any usual 3D print file. In the slicer (we used Prusa Slicer, but any should work), you can scale the object to exactly 82 × 45 mm. We had to unlock the aspect ratio as it ended up being out by about 1 mm without this, but it’s not noticeable in the final print.
Common wisdom dictates that you should print your lithophanes vertically, as this will give you better resolution (a large brim will help it stay attached to the print bed). We tried out a few ways of printing and for this style of image (where most parts are either very black or very white), we didn’t notice much difference between them printing vertically and horizontally (other than they printed much faster when lying flat to the print bed).
A few dots of superglue attached the lithophane to the back-light (we put them in areas that were dark so they didn’t affect the image in any noticeable way). That’s the image set up – we just need a way of providing power.
The back-light is basically just a white LED, plus appropriate diffusers and reflectors, so powering it is just the same as powering an LED (even down to the fact that they have a long leg and a short leg). Like many people, we have stacks of USB chargers lying around, so this was the obvious choice for sending electrons in. All we needed was a micro USB breakout board (these are available cheaply from a wide variety of vendors online) and a single 220 ohm resistor to limit the current.
We soldered these up, but needed a way to insulate the bare wires – after all, we didn’t want to put it down on a metal surface and accidentally short it out. We decided to use the hack-y option and cover everything in hot glue. It’s not an ideal solution, but it does work. Fortunately, we’ve been able to hide all the glue on the back, and who looks at the backs of pictures anyway?
