Build a Rainbow Lightbox to Make Pixelated Shadows

I saw this idea in an issue of Make:Magazine and was obsessed with recreating it for our museum, and to design a version that was smaller and modular. The effect is amazing, and would make a great coffee table if you're ambitious, but in small scale works equally as well!

The pixelated rainbow lightbox is hard to explain - see this video from the creators over at the Wonderful Idea Company (picture above of the original that I was privileged to see when visiting Maker Ed in California). The box itself is just any shape that can hold a bunch of mylar tubes sandwiched between two translucent diffusers.

This idea was originally created by a Japanese artist, Taizo Matsumura, and called “Hikari no Hako”. When light is projected on the box, the tubes reflect the light and it is passed through the diffusers. When light from an RGB LED lamp that has the different LEDs separated by a small distance comes through the box, the tubes remix the colors to create multiple hues. Because each of the tubes is passing along light separately, there is a pixelated effect.

I'll describe a couple of variants that I worked on developing in this Instructable, including a couple of boxes that you can 3D print using Tinkercad source files. This Instructable is entered into the Plastics Contest, so be sure to vote if you are inspired to create your own or get ideas for a project you're working on!

• A box or tube to hold the mylar tubes - anything from a toilet paper tube to cereal box to 3D printed enclosure
• Shiny mylar plastic - you don't need a ton, it's easy to buy 25ft rolls on Amazon but if you are making a small version just find a mylar balloon or two to cut up into strips
• A diffuser for each side. I used this Satin Ice Clear acrylic plastic from TAP plastics in 8" sheets for the 8" version, 4" samples for the 4" version. The Make:Magazine version links to a different way to build this, and you can also use plain old wax paper.
• Scotch tape
• A variety of round objects to roll the tubes around
• Scissors
• E6000 Glue
• 3D printer and filament if you are printing an enclosure
• If you want to take advantage of my 8" modular 3D printed design to attach multiple together, some 1/4" by 1/16" neodymium magnets like these
• A light source. I built one using a design from another project, I'll include more information about supplies for that in Step 7. This totally works when you put it up to a computer screen with a colorful GIF or cartoon running, or a cheap disco party light like this also is effective.

I'll explain my three different versions of enclosures in this step and the next two. What I had originally envisioned was an experience where kids could create their own out of toilet paper tubes to take home, experience a table like I'd seen at the Wonderful Idea Co., and participate in building a larger scale one made of 3D-printed magnetic "blocks" of the tubes and diffuser. The pandemic kinda put those grand visions on hold, but the modular version is a great size to get the full experience. This version is included below as an embedded TinkerCAD file. It's a little over 8" in size so you'll need a 3D printer that has a bed about that large.

I used a LulzBot TAZ 5. If your bed is smaller, have no fear! See the next step for a 4" version that fits on most mini 3D printer beds. I found this 8" version to take just about 8 hours to print on the fastest print settings (0.38mm layer height). PLA plastic is fine, I would avoid ABS or PETG because of how large/tall of a print this is and the resulting issues with layer delamination. Print with supports - it is just needed for the small inlay where the plastic will fit inside on the side that prints down, and should be very easy to remove.

If you are using this design and want to make a bunch of them to attach together, the recessed cylinders on the sides are for inserting the magnets - I would use superglue with those. Test out the magnet polarity and alternate them North/South in the same pattern on each side. If I were to design this differently for a large exhibit, I might use stronger magnets so tinker with this design a bit if that is how you decide to implement yours.

To test this whole concept out and make sure that the plastic I was going to order would work, I created this small version. If you have a smaller 3D print bed, this is the one for you. Print with supports, it's just needed for the inlay where the acrylic goes on the side that faces the bed and is easy to remove.

Another benefit of this design is the cost - acrylic can get expensive when you get larger sheets cut to your specifications. This design was built around the sample pieces that you can buy from TAP Plastics here. Total cost is only $4.00 plus $8.30 shipping for the plastic.

You don't have to 3D print an enclosure to make this all work, so don't fret if you don't have a printer or access to one. We'll be doing everything else the same way from here on out so follow those instructions. A small cereal/snack box with the sides cut out as a frame will work.

For a basic handheld version, I just used a toilet paper tube, wax paper, some rubber bands, and filled it with small rolled mylar tubes. If you go this route, don't buy a whole big roll of mylar - cut up a shiny mylar balloon instead, or find a smaller roll at your local craft store. It totally works, it's just a very small version. This one is best if you hold it up to a colorful cartoon or crazy animated GIF on a computer screen/iPad or phone.

Once you have created your enclosure, it's time to roll up your sleeves and get making the tubes. This takes a lot longer than you might think! For the 8" version, probably set aside an hour or two and watch a movie to get them all rolled. For the smaller versions it's much simpler. I made a 24" by 24" version pictured above, I bet I put in 10-20 hours or more over the course of a few evenings in total to make all of those!

Cut a strip of mylar to the inside width of your enclosure so that it fits with minimal clearance between the diffusers. For the 3D printed 8" and 4" versions, it's 48-50mm in width. For the TP tube or whatever else you are using, just measure this distance. You can always trim the tubes afterwards if needed, but it helps to get the strip cut to the right width in the first place. You don't want them to flop around on the inside of your enclosure, but also not get pushed down too much by the diffuser. I made a jig for the largest version to cut the strips in exact lengths every time, but you don't need to do this.

Take your cut strip and roll it around something round. I used a film canister, 1/2" PVC pipe chunk, some random cardboard tube from the center of a roll of receipt paper or something, and a 1/4" paper straw. You want variety in the sizes, it makes for a cooler effect. I tried using tubes as large as a toiled paper tube (about 2" in diameter) but they tend to get crushed and deformed a bit when sandwiched in there with all the other tubes. You can make interesting teardrop/heart shapes this way, though, so experiment with that! If you are making a bunch of these, it can help to measure your predetermined length of strip for each different size tube you are making and cut them out first, but I honestly didn't do that and it was okay. If you are looking for high precision that is a good way to achieve it.

Now, you'll want to fill your enclosure up. You need two diffusers for each box you decide to make. Put one diffuser in - for the 3D printed versions, add a small amount of glue (not so much that it squishes out) along the inside of the enclosure, then push an acrylic piece in. Let this dry - E6000 says 24 hours for full cure, I usually give it an hour or two to set because I'm impatient then be gentle in handling. For precision, I bought this E6000 for jewelry making - it helps a lot to have that very small tip for this application. Don't use superglue, the fumes from that will cloud the plastic edges. Silicone is probably an okay substitute if you can't find E6000 or don't want to buy it, YMMV. For the wax paper version, tape it down or use rubber bands.

Once your first diffuser cover is in place, fill it up! I added them in random ways, and took the smallest tube I was rolling and shoved it into the small spaces between tubes. Fill it so that the tubes don't slosh around, but not so tight that they will crush each other. On our larger version they settled in place quite a bit after some moving of the exhibit around, but this is not an issue that I've seen with the smaller versions.

Once you are happy with how full and random your assortment of rolled tubes is, fit the other diffuser cover in place. I like to put it in place temporarily, shake the box so the tubes settle into place, then fill any gaps. For the 4" 3D-printed version, you have to glue or tape in place both diffusers.

On the 8" version I made a small overhang on one side, the side that prints down onto the bed. My intent there was twofold - you can just press fit the plastic diffuser in place instead of gluing in case you need to add more tubes or want to change the configuration. I was also going to have different school classes contribute to making each block and put their class name there, but again, the pandemic put those plans on hold!

I didn't take detailed photos of the light build but there are a few places I can send you for more info on that. As mentioned, this works with any light - white light just creates pixelated shadows, an animated GIF or colorful video/cartoon is cool to look at as well. For the full cool pixelated combo effect, an RGB LED that separates the LEDs by a small distance and combines the colors into white light is necessary. This is because the different colors diffract around whatever object is in between the light source and surface of the lightbox, and it separates the colors out to create different hues and combinations through the process of color addition. Any RGB light that works in this way will achieve the desired effect, see below for how I built mine.

To build my light, I reused an old base I had built for another activity called Light Play, based on this wonderful Instructable from the Exploratorium science museum in San Francisco. Follow both those links for information on how to build this style of light. Instead of the LED and driver specified there, substitute PART #: CREEXPG2-WW363 and choose Triple 3up and Warm White 3000K for the configuration. Also substitute a 350ma driver, PART #: 07027-D-350. There is more information on an alternative light build in the Make:Magazine description as well.

I found that when I built the light with just aluminum round stock as indicated in the Exploratorium build, there was not enough heat dissipation for the LED. I found this old neat heatsink from a PC that I took apart years ago, it worked well instead. I laser cut a cover to fit over the top and it's perfect. A larger, flat surface of aluminum might be best when you build yours - try hooking up the light attached to whatever you might use first to see how warm it gets before fully completing it.

Experiment with different lights to see what looks cool. The handheld versions are great to hold up to different sources of lights to get different patterns. Things like pasta strainers or cutouts of shapes from cardboard are neat to play with. Just your hand creates many cool effects - see what works best and if you build and test, share in the comments! The darker your surroundings are, the more clearly you will see the color combinations and shapes. Try making something motorized to pass an object in between the light source and screen - I think that will be my next version!