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Print the Rainbow

How to Get Iridescent First Layers

Picture of Matthew Mensley
by Matthew Mensley
Aug 2, 2019

Achieve funky colorful first layers using diffraction grating, in this inexpensive and unusual trick.

File this one under ‘weird stuff you can do to your prints.’ Found on the r/3Dprinting subreddit, did you know you can imbibe your glossy first layers with a technicolor shimmer that is pretty damn magical?

It turns out it is possible when printing on surfaces that diffract light by nature of their structure. Molten plastic extruded onto an insanely fine-textured surface will pick up the negative of said surface and then itself diffract the light. Pretty neat!

One such method of magicking this effect on your first layer is to print on top of diffraction grating. Available in several grades — much like sandpaper and its levels of coarseness — these sheets of polyethylene pack in thousands of parallel reflective lines into a small area. These tightly packed lines bend light all out of shape into its component wavelengths, resulting in rainbow-hued refraction.

For a better explanation of what’s going on, the video below is a popular starting point.

We’ve yet to try it but would expect that repeated printings will eventually degrade a sheet of diffraction grating. Think of it as a consumable; good for the occasional face-down print that needs extra ‘wow’ factor.

Alternatively, other industrious Redditors have pointed out their success using a more common household object — compact disks. Turns out, if you strip away the metallic foil (itself sometimes encased beneath an additional disc of PC) from a CD, you expose the texture that diffracts. Fix a CD processed in this way to your print bed, make the necessary print offsets, and it’s possible to cheap your way to the same result.

Diffraction printing on a cd
3D printing on a CD. Still from a video posted by u/2016AprilsFool on subreddit r/3Dprinting

There are probably other ways to achieve such an effect on the first layer of a print. This is the first we’ve heard of it, and we can’t wait to try it out.

Have you experimented with diffraction grating for your printing? How did it turn out? Let us know in the comments below.

Lead image credit: JunOneDor, via Reddit/Imgur

License: The text of "How to Get Iridescent First Layers" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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