Introduction: Multiplying Chocolate Puzzle

About: I enjoy 3D printing, Arduino electronics, and DIY.

Puzzle Directions:

Rearrange the broken pieces of chocolate so that there are two more rectangles of chocolate than when you started.


This Instructable will show you how to 3D print and decorate a puzzle that creates the illusion of pulling chocolate out of thin air (But don't eat it!).

My design is a variation of "Unlimited Chocolate" video produced by SoFlo []. However, there are some key differences (discussed in Step 10).

If you want to solve this puzzle yourself, stop before Step 5 when the solution is revealed on the wrapper.

Step 1: Materials

  • PLA filament*
  • 3D printer
  • Brown spray paint**
  • Color printer or printing service
  • Aluminum foil
  • Cardboard
  • Tape
  • Scissors
  • Cardboard cutter (optional)

* I used white filament to 3D print the puzzle pieces (which I later spray-painted brown). If you have brown filament, go ahead and use it; just skip Step 4. However, I think spray-painting produces a more realistic chocolate look.

**Choose a dark-brown, glossy, paint+primer spray paint that bonds to plastic. I used Rust-Oleum 2X Ultra Cover in Gloss Kona Brown (see picture above). NOTE: You must be 18 years or older with a valid ID to buy spray paint in many states in the U.S.

Step 2: Design 3D Printed Pieces

I used Fusion 360 to 3D model the broken chocolate pieces. (I designed the chocolate bar in multiple pieces. I did not print the entire bar and cut it into pieces afterwards.)

Here is the basic design process I used:

  1. Sketch and extrude 1 rectangle of chocolate.
  2. Use the rectangular array tool to create a 4x4 grid of chocolate.
  3. Use the combine tool to form the 16 individual bodies into 1.
  4. Draw construction planes and use them to split the bar into the various puzzle pieces.
  5. Sketch and extrude the "Instructables" text on each rectangle (I used the font "Grill Sans MT Ext Condensed Bold").

Don't worry; I provided the .stl files for each of the chocolate bar pieces in the next step, so you don't have to model them from scratch.

Step 3: 3D Print Pieces

Attached are all 9 of the chocolate puzzle piece .stl files. (The names of each file refer to the relative initial position of each piece in the puzzle) If you have a reliable 3D printer, you can print a couple pieces at a time (I wouldn't recommend printing them all at once though).

Here are the print settings I used:

  • 3D printer: Monoprice Maker Ultimate
  • Filament: White PLA
  • Layer height: 0.1 mm
  • Shell thickness: 0.4 mm
  • Bottom/Top thickness: 0.4 mm
  • Fill density: 20%
  • Support type: none
  • Platform adhesion type: Raft
  • Orientation: [see image above]

Step 4: Spray Paint 3D Printed Pieces

Here are some tips on spray painting the puzzle pieces:

  • Only use spray paint intended for plastic.
  • Spray paint outside, away from things you do not want paint on.
  • Avoid spray painting when it is humid or windy outside.
  • Paint the pieces on something disposable, like a medium-sized cardboard box.
  • Follow all directions on the paint container.
  • Don't hold the can too close to the pieces, the force of the spray paint may move the pieces.
  • Apply just enough paint to completely cover the pieces.
  • Spray the part from all angles.
  • Before turning the pieces over and painting the second side, wait for the first side to completely dry.
  • Make sure the pieces are not sticking to the cardboard box (especially the portions with wet paint).

Step 5: Design and Print Puzzle Wrapper

Attached is a PDF of the wrapper design. Just color print it on standard copy paper. If you do not have a color printer, just take the file to any office supply store and they will print it for you (it should cost less than a dollar).

I used Microsoft Word to design the wrapper and Autodesk Autocad to sketch the puzzle setup and solution. These are the fonts I used: "Haettenschweiler" for the main logo, "Century Gothic" for the secondary text, and "Franklin Gothic Medium" for the Puzzle Facts. To make the wrapper the correct size for the puzzle, I used the Size tool (located on the right end of the Format tab in Word).

Step 6: Cut Out Wrapper, Aluminum Foil, and Cardboard

Cut out the following materials:

  • Color copy of the wrapper - cut along the outer thin black line (do not cut out each individual rectangle) and fold along the
  • Aluminum foil - tear a piece the size of two pieces of copy paper (if you lined the papers up against their long sides). Be careful using scissors to cut aluminum foil, as it may dull the scissors' blades.
  • Cardboard - cut a 3 inch by 6 inch piece. I used a serrated Canary Cardboard cutter (which makes it extremely easy to cut cardboard), but scissors will work.

Step 7: Fold Wrapper

To make the aluminum foil wrapper:

  1. Tape the cardboard in the center of half of the aluminum foil sheet (make sure the shiny side is facing down).
  2. Fold the aluminum foil in half over the cardboard.
  3. To make the edges smooth, fold over about a half inch of foil on each of the edges.
  4. Fold the long sides of the foil around the chocolate bar pieces.
  5. Fold the paper wrapper around the foil and tape the edges together as shown in the picture. It should be loose enough to easily slide the wrapper off.
  6. Fold up the ends of the foil wrapper so it makes a flat, rectangular seam.

Step 8: Assmeble Final Product

The chocolate puzzle pieces should be nicely wrapped up inside the foil at this point. If you are giving the puzzle to someone else to solve, make sure they don't see the solution under the back flap.

Step 9: How to Solve

Follow the piece movements in the images. The key to this puzzle is flipping the center triangle piece over and shifting the other pieces to the right. This will result in two V-shaped channels on the other side of the chocolate bar with the exact same volume as the two rectangles that were removed.

Step 10: Inspiration

The inspiration for this puzzle came from the Unlimited Chocolate video produced by SoFlo [].

According to most explanations of the video, the extra piece of chocolate comes from the slivers of chocolate left out when the pieces are shifted over; so little is removed that to the human eye it looks like a whole chocolate bar. However, the common explanation is incorrect. At one point in the video, the person's hand passes completely over the top piece of chocolate and the piece changes. The image above shows the piece before and after the hand. This video is not an optical illusion, it is slight-of-hand!

When I was creating my variation of the puzzle, I noticed that something was not adding up in the video. It took several replays of the video for me to figure out what was going wrong. Since SoFlo's version of "Unlimited Chocolate" cannot be recreated in real-time, this led to me developing my own version (which features two angled cuts that fill in the missing rectangles).

Step 11: Mistakes and Thoughts

If I learned anything from making this Instructable, it is to double check your work! Somehow I managed to design, print, cut, fold, and take pictures of the chocolate wrapper without noticing that there was an "A" missing in the big "INSTRUCTBLES" word on the front. Luckily I realized my typo and fixed before publishing. Always double check :)

Creating this Instructable gave me the opportunity to try spray-painting a 3D printed part. It turned out great. It is somewhat hard to tell in the photos, but the 3D printed pieces look just like real chocolate. At only $4 a can, it is much cheaper than buying different colors of filament, doesn't require much more work, and produces a good-looking final product.

Puzzle Challenge

First Prize in the
Puzzle Challenge