← Back to STLKit3D Generators

I Spent 40 Hours Printing Flat Lithophanes: Here Are the Numbers That Actually Work

Most lithophane tutorials online repeat the exact same generic advice: "just use 100% infill and print vertically." But if you've actually tried doing that on a standard bed slinger, you've probably ended up with terrible ringing artifacts, knocked-over prints at hour seven, or muddy grey faces that only look good under direct sun.

After throwing away half a spool of failed white PLA test strips, here is the real breakdown of what works, what fails, and why certain settings ruin your contrast.

1. The Thickness Trap (0.8 mm vs 3.0 mm)

The whole secret of a lithophane is optical density. If your plastic is too thin, the highlights blowout and turn pure clear. If it's too thick, standard LEDs can't punch through the shadows.

Here are the boundary numbers that consistently gave me decent dynamic range across different spools:

• Minimum Thickness (Highlight Areas): 0.8 mm. Don't go down to 0.4 mm unless you want your print bed texture visible through the person's forehead. At 0.8 mm (with 0.20 mm layers), you get exactly 4 solid passes. That is stiff enough not to crack when you peel it off the PEI sheet.
• Maximum Thickness (Shadow Areas): 3.0 mm. Anything over 3.2 mm just becomes a dark silhouette block. 3.0 mm gives deep black shadows when backlit by a typical 5V USB LED strip.

2. Printing Flat vs Upright: Stop Ruining Your Z-Axis

Everyone says: "Never print flat, always print upright." That is half-true, but it comes with a huge catch.

When you stand a thin 80mm plate vertically on an Ender or any Cartesian printer where the bed flings back and forth on the Y-axis, momentum causes mechanical resonance as the print gets taller. By layer 300, the top of the photo will have fuzzy micro-shifts.

• If you print upright: Align the thin edge strictly along the Y-axis, never along X. That way, the violent bed jerks push along the spine of the piece, not against its face. And slap a wide 10 mm brim on it with 0.00 mm brim gap.
• If you print flat on the bed: It will print four times faster and never fall over. But you must drop down to a 0.12 mm layer height and keep your print bed immaculately cleaned with isopropyl alcohol. Any fingerprint grease will show up as a dark smudge in the final backlit photo.

3. The Infill Mistake

Do not set infill to 100% with a grid pattern. Your slicer will still try to draw tiny internal grids that leave weird ghost cross-hatching inside highlights. Instead, in OrcaSlicer, PrusaSlicer, or Cura:

1. Set Perimeters / Wall Loops to 12 (or anything high enough so the slicer generates zero internal infill).
2. Or set Infill Pattern to Rectilinear or Monotonic. This ensures the filament lines run consistently across the lighting path.

4. Filament Color Isn't Just "White"

This caught me off guard early on. Not all white PLAs behave the same:

• PLA+ / Pro (Opaque White): Avoid these if they contain heavy chalk or titanium dioxide pigments. Light barely cuts through 1.5 mm of it.
• Basic / Warm White PLA: This gives portraits a natural, warm candle-like glow.
• Cool / Cold White: Best for mechanical drawings, logos, and cityscapes where you want bluish-white contrast.

Quick Cheatsheet

If you're ready to slice: set walls to 10, layer height to 0.12 mm, keep your speed under 45 mm/s on outer perimeters, and use a clean white PLA. Grab the model from our STLKit3D Generator Hub and slice away.