Monday, May 13, 2013

Constructing a Dodecahedron

So one of the basic tenants of sacred geometry meditations is actually constructing the figures.  There is no better way to instill their symbolism and mathematical qualities into the mind. In the context of two-dimensional polygons and polygrams, construction is only done with a compass and ungraduated straight edge. Having been working with and meditating upon the three-dimensional geometric figures, I decided to apply this practice to constructing platonic solids. That, and having Ptah as a patron, I like building things.

For constructing such a thing out of wood, you will need:
  • Wood
  • A band saw
  • A disc sander
  • 5-minute, 2-part epoxy
  • Wood putty
  • Sand paper
  • A utility knife
  • Your favorite Bob Vila flannel shirt (optional).
There are variations on the tools you can use. For example, since I didn't have access to a band saw at the time I cut the twelve pentagons using a laser, from a vector file on my laptop.

You will need to begin by drawing 12 congruent pentagons onto a piece of wood, or multiple pieces of wood more likely. Ideally create yourself a perfect pentagon using a rule and compass or computer software can also do this for you. In either case, you will need a template to keep your pentagons consistent. To minimize the amount of wood needed, arrange these pentagons in a way that minimizes empty unused space on the wood. Make sure your lines are dark enough to see, and then take your piece of wood to your band saw. Be sure to wear safety goggles.

Take your wood to band saw and cut out your twelve pentagons. Error on the side of cutting outside the lines. You can sand these down later, but you can't add more wood back on. Again, these can be cut out by other means as well, such as with a laser.

Once you have your twelve pentagons, you will then need to take these pentagons to the disc sander. A disc sander is needed over any other type of sanding tool, because you can change the angle at which you are sanding, and the angle is the important part. We are now sanding the five edges, so that they will perfectly line up with the other faces of the dodecahedron when we get to the gluing process.

A dihedral angle is the angle between to joined faces of a polyhedron. The disc sander needs to be set to half of the dihedral angle, as the joining face will take up the other half of the angle. For a dodecahedron, the actual dihedral angle is about 116.6 degrees. Half of that would be 58.3 degrees, and this is what we need. However, the sander needs to be set to the complementary angle of 121.7 degrees (180 - 58.3). This can be set with a protractor. I personally cut out a piece of wood on the laser with the proper angle as a I didn't have a protractor handy at the time. Either way, it will not be exact, but you should get it as close as you can.

Set one of your pentagons on the disc sander, the side with the pencil marks facing you. Make sure you are wearing eye protection and begin sanding. Sand until you have sanded right on the pencil line. Keep the edge of the pentagon even with the face of the sander. Repeat the process five times per pentagon for all twelve of them.

11 out of 12 Faces Pieced Together
Then comes the fun, yet potentially frustrating, part. I like to use 5-minute epoxy, as it dries fast and holds very strong. If you can, I would use a dremel or some other tools to roughen up every edge that will be glued to another piece of wood, to give it some tooth to hold onto. Take three pentagons. Make sure they fit together nicely (you may need to do some adjusting here and there with the sander to get all the pieces to fit together). Mix up just enough epoxy to glue just these three pieces together. I recommend a plastic knife or a wooden popsicle stick for mixing and applying the glue. Keep in mind this kind of adhesive is serious, and will stick to things. Do not do this on your nice table. Do it on some newspaper in your garage. Make sure to follow the instructions. Usually you need to mix the two parts of the epoxy together for about 30 or so seconds. Apply the epoxy only to the parts of the wood you are currently gluing. The hard part is holding the three pieces together and constantly adjusting them to keep them in line until the glue dries. Making sure the glue is mixed together for the proper amount of time can make this process easier and quicker.

Those first three pieces are the hardest. After that, I recommend gluing one piece on at a time, adjusting each single piece with the sander as needed.

When you are done, it is very possible that there may be a gap between one or more of the edges. Use some wood putty to fill in any such gaps, and let it dry over night. Then sand down the wood filler with some sandpaper and use the utility knife to cut off any excess epoxy (cut away from your face, man).

Put on a coat of primer and then do with it what you will.

I recommend a series of meditations with the thing just as a plain white symbol. At some point you may wish to paint it in appropriate symbolism. This could be to paint it black or white, pertaining to the quintessence and the universe. You may also elect to paint the twelve faces in symbolism and/or colors of the zodiac.

The Easy Way Out

Or you could just use some sturdy, easier to use, material such as corrugated cardboard.  Cut out twelve congruent pentagons, tape together using your favorite tape.  For the dodecahedron, just know that three pentagons meet at every vertex (not that you could make it any other way).

Be warned that masking tape doesn't hold up very well under paint.  I made a set of all five Platonic Solids this way and had to use a layer of gesso on top of the paint to keep the tape from peeling.

The Five Platonic Solids Painted in Elemental Colors

Have fun.


  1. Have you thought of just glueing paper pentagons onto a 12-sided RPG die?

  2. That would work, I suppose. However, I find an important part of the exercise is in the actual construction. Also, a 12-sided die is generally very small.