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DIY: Companion Cube

May 5, 2010
Best Friends Forever!

Best Friends Forever!

I’m not always a good gift-giver (I’ve gone so far as to give cookies that are accidentally on fire), but I had a bout of inspiration for the most recent birthday occurrence: make a companion cube! Perfect for any native of Internet land, these fun and lovable geometric friends will never give you up, never let you down, never run around or desert you.

So here’s how I made one, and how you can make one, too:

Step 1: Acquire a cube of Styrofoam

I had to get mine online ( It was around $13. Places like Joanne’s, Michael’s, and Wal-Mart don’t have huge cubes of Styrofoam available in-stores, and there aren’t many online, either. I used a 10-inch cube, which ended up being very large, as you can see in the photos. You could probably go as small as a 6-inch cube if you desire, but I imagine it would make the carving process more difficult.

Step 2: Acquire the other supplies

You’ll need to carve down the Styrofoam to get the Companion Cube details. Don’t worry, it’s not so difficult! I used a 6-inch foam-cutting knife from Wal-Mart, a sheet of very coarse sand paper, and a fine sanding sponge (also available at Wal-Mart). You’ll also need acrylic paint. Don’t use other paint. Get black, white, red and blue. I also had varnish, to cover the finished product, but I don’t even know if it has that much effect on Styrofoam, so I’m going to say it’s not necessary. You’ll definitely need a vacuum. Trust me.

Step 3: Plan

Find a photo of the Companion Cube on Google. Use different color marker to plot out where you’ll be carving. For mine, the purple is the deepest cut, the blue is the second-deepest, and the white is the shallowest. I used highlighter, and I don’t recommend it. It comes off a little too easily…

I'm trying out for the Blue Man Group

I'm trying out for the Blue Man Group

The process is much easier if you use plates or some other circular objects to draw the two circles in the middle of each face of the cube. A ruler will also be helpful to get straight lines on the corner pieces, and to make them even.

Step 4: Start carving

Very messy

Very messy

I started with the deepest part, that doughnut in the middle of each face. I had to cut off the rectangular corner pieces, since they started falling off. I carved each of them individually into the right shape, and put them aside for later. Using both the foam knife and the sandpaper, carve down the circle to a depth that seems acceptable. Use the fine sandpaper to smooth it down. Make sure that you carve around the center circle and corner pieces so that where they meet the main body of the cube, there are angles, not slopes.

Step 5: More carving

Shave down the center circle on each face, as well as the triangular corner pieces. I made the circle stick out about 1/2 an inch, and the corners almost an inch.

Step 6: Paint

Be careful not to get acrylic paint on your clothes. It doesn’t wash off. For the deepest part, you’ll use white and a good amount of black to make dark gray. Paint it, and wait for it to dry. Then, use white and some black to make light gray for the corner pieces and center circles. Paint and dry. For the hearts, I made a cardboard cut-out, so that they would all look pretty much the same. Use White, some red, and a drop of blue to make pink, and paint the heart. They’ll need three or so coats, so they stand out bright and pretty against the gray. The hearts don’t all face the same direction; they rotate. Keep that in mind. Then use the same pink, but with a little more blue for the lines that go through the middle. They’ll also need multiple coats.

After I painted everything, I reattached the rectangular corner pieces with toothpicks, since glue wasn’t working very well. I just stuck a toothpick through each face, and they held on well.


Caution: Keep away from incinerators.

2 Comments leave one →
  1. May 5, 2010 2:07 pm

    That looks pretty darn authentic! Funny thing is that I have never played Portal but have seen enough screens and cosplay and vids etc to feel like I have. I really should get it… I only hear rave reviews for it but I realize that it would become another dust covered game on my shelf :(

    • Amy permalink
      May 5, 2010 2:38 pm

      The great thing about it is you can sit and play through the whole thing in a few hours. Well, if you’re OK at puzzles, that is. I played it a friend’s house, which is your best bet. You don’t have to buy it, and you don’t have to feel bad about the dust :)
      It’s worth it!

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