This is a rectangular prism made of styrofoam. You can create cool volumes with this or make it into a nice decoration.

Step 1: Materials and Tools

The tools required for making this prism are fairly easy to obtain. You will need a hot glue gun (with several gluesticks), a metal straight edge (I used a metal ruler), a long blade preferably with a length that is long enough to chop your desired prism in half, and a little bit of sand paper.

The materials are as simple as that, styrofoam balls! You can use a variety of foam balls with any size/diameter. I chose to use 1", 1.5", and 2.5" balls and switched off between the smooth and rough spheres. The spheres provide a rigid form that really becomes helpful in the later part of this process.

Let's get started.

Step 2: Some Preliminary Steps

First we are going to need to create some additional "tools" for this process.

Using the straight edge, place on the reverse side of a sheet of sand paper and cut out a square. Then at each edge, cut into each diagonal without splitting the square. Then apply hot glue to the back of the surface and glue onto a styrofoam ball. Be careful not to burn yourself when attaching the sand paper to the sphere as the glue is hot enough to be felt on the back. This will be used for sanding down the edges of the balls to give more surface area for the glue to attach to each other. Make one for each size ball.

I made a small foamboard "mold" that were the dimensions of my prism. This helped to keep my proportions under control an guided where I would attach the styrofoam.

Now we can do the cool part.

Step 3: Assemble Spheres

When choosing to attach spheres to each other, use the sandpaper ball of the desired size and sand away a small portion of where you plan to attach. NOTE: The glue gun is extremely hot. It is hot enough to melt the styrofoam. DO NOT intentionally inhale the fumes. Then using the hot glue gun, apply a decent amount, without melting the styrofoam, to the sanded portion and attach the spheres. Continue doing this process until you accumulate a "mass" that is larger than your desired prism dimensions. Don't forget to use whatever guide, in my case a box, as reference for where to glue your spheres.

Step 4: Paint

If you want the finished block to have color

Step 5: Trim the Edges

The styrofoam makes it easy to manipulate with sandpaper and a knife. Using the blade, begin cutting off edges of the mass to fit the dimensions of the prism. Then use the sandpaper and smooth that whole surface down. You can treat it much like a piece of wood when sanding, in other words, you can grab the whole thing slide it across the paper. Make sure to continuously gauge the sizing of your prism when cutting. I suggest trimming and sanding down one side to get a flat surface before moving onto the other "faces" of the prism. The choice grit is dependent on what finishing you want, I chose to have a smoother finish so my sandpaper is 220 grit. Be careful when cutting, You are handling a long blade so be careful much like you would other cutting tools.

Alternatively, if you own a

Keep going until you eventually start trimming it into a prism.

Step 6: Touch Up and Polish Prism

Now you are done!

You can continue to polish or cut edges off. You can paint it but do not spray paint it (the paint "eats" away at the material unless you want it to look more like a cracker texture). If you want, you can even cut straight down into the prism.