Introduction: Coolest DIY Icosahedron Stationary Holder

A great new addition to anyone's home. This instructable will be showing you how to create your own icosahedron pencil holder made out of plaster to show off to your friends or use on a day to day basis. It uses the techniques of casting and creating molds and can be colored to anyone's liking if they choose!



- Exacto-knife x1

- Tape x1

- Hot glue gun x1

- Steel ruler x1

- Pen x1

- Cutting mat x1

- Spatula x1

- Bucket x1


- High impact polystyrene sheets x1

- Plaster x3 yogurt cups (the ratio of plaster to water is 3:2)

- Water x2 yogurt cups (the ratio of plaster to water is 3:2)

- Blue watercolor (optional)

- PVC pipe/ connector x1

Step 1: Gather Your Equipment

Before starting, make sure you have all of your materials you will be using for the first part of the project, mold creating. You will need your pen, Exacto-knife, steel ruler(s), high impact polystyrene, and cutting mat ready.

Step 2: Drawing Your Net

Draw out your icosahedron net onto your high impact polystyrene sheet using your pen and steel ruler. Make sure to make each of the equilateral triangles in the net all have 5 cm sides to them. This will make sure your shape is well made and fits together.

You can choose to look and trace the shape provided above or even print it out. I used math, measurements, and the Pythagoras theorem in order to find the height of each triangle to create the shape although it may be easier to just print, cut, and trace the net onto your material.

Credits to:

3DLDF User and Reference Manual. Accessed 24 Nov. 2020.

Step 3: Cutting and Scoring Your Net

Cut out the outsides of your shape from the bigger piece of material but make sure not to cut out the lines lacing through the inside of the net. For those lines, you'll want to score the lines to make sure you can bend the net. In order to score, you must lightly cut through the polystyrene about halfway down or until it is bendable. Try not to cut through the triangles and pieces but if it happens, it can be fixed up in the next step.

Step 4: Folding and Taping the Net

Fold each line and scored edge inwards in a valley fold. Do this for every line including the lines in the middle of the net and do this slowly or the net could snap. If your net does snap, go ahead and tape it back onto the main net and make sure you tape the piece together on the outside of where you'll pour your plaster. Once all of your sides have been folded, construct the shape above and tape all the connecting edges together making sure everything is secure.

Once you have finished taping, it should look like the image above but we don't want to tape the whole shape together, or else there will be no place for the mold to be poured. So, fold back 2 of the top triangles of the mold that are next to each other and tape them down to the main body. Your final mold should look like the image above.

Step 5: Water Testing the Mold

Once you have finalized the net and taped it securely along all of its edges, perform the water test on the mold which includes putting water into your mold and holding it out. Observe whether any water leaks out of the seams of your mold. If it does, then retape your edges more securely. If it doesn't then congratulations, you have successfully made your icosahedron mold.

Step 6: Creating the Core

Once you have finished making your mold, take a PVC pipe that can fit in the hole you have created in your mold. If it fits, trace around the PVC pipe to create a circle. Cut the circle out and make sure that the circle fits right onto the PVC pipe like the above image.

Step 7: Gluing the Core Together

Apply hot glue to the edge of the PVC pipe as shown and glue the circle and PVC pipe together. Make sure that there are no holes on the outside of the core as if the plaster inside the mold seeps into the core, it will get stuck and won't come out. Once secured and glued, it should look like the picture above. If that's done, you have successfully completed the prep for the product and are ready to pour your plaster.

Step 8: Creating Your Plaster Mixture

To create your plaster mixture, you will need to pour in 3 parts of plaster to 2 parts of water into your bucket. This ratio can be scaled up or down but to measure, I just used 3 yogurt cups worth of plaster and 2 yogurt cups worth of water. Mix with a spatula until thoroughly combined and homogenous and try to get rid of any lumps of plaster you may see. Adding watercolor is optional but I decided to use blue watercolor to make my product look more aesthetic than white. I found that adding around 30-40 drops of watercolor makes the plaster thoroughly colored.

Step 9: Pouring and Drying

You're almost done! Pour in your plaster mixture into the mold until it is a little more than halfway full. Don't worry if it spills or leaks out, the plaster, once dried, can be easily scraped off hard surfaces. Once it is filled halfway, insert your mold immediately halfway into the mixture and tape the top to the sides of the mold. Try to center the core to your best ability and make the core depression halfway down the mold. Once it is positioned, let it dry for a day.

Step 10: Cutting and Final Polishing

Cut your dried cast out of the mold using your Exacto-knife and pull the mold apart. Then, pull out your core from your mold by twisting and pulling in one motion. If It doesn't come out properly, cut around the PVC core to release the core from the pencil holder. Sand down any roughness or unevenness on the product to make it polished and your final product is finished.