How to Make a Dodecahedron Plant Pot Using Casting

This instructable shows how to make a dodecahedron plant pot using a method called casting.

Casting involves two parts - a mould and a core. The mould is the shape that you would like the product to be on the outside (in this case a dodecahedron) and the core is what you will take out to make a hole for the plant to go inside.

This instructable will show the drawing of the mould, cutting of the mould, the core, how to make the liquid plaster, and the final product.

Supplies are listed below

Supplies

Preparing the moulds:

A3 paper, ruler, protractor, large sheet (A3 size) of high impact polystyrene, and a cutting tool

Pouring the plaster:

2 cups of water, 3 cups of plaster, cutting tool (if necessary), bucket, stirring tool, drill (if necessary)

Step 1: Drawing the Mould

To draw your mould, you need an A3 piece of paper, a ruler, and a protractor.

Make a central pentagon with 4.5cm sides. To ensure that all sides are equal, each angle should be about 108 degrees.

Once completed this central pentagon, continue drawing 5 pentagons surrounding this central pentagon, with the same measurements.

Once finished the left side group pentagon, continue drawing as shown in the image above with the same measurements. You should have 12 pentagons in total (a dodecahedron is a 12 sided shape)

Step 2: Cutting Out Your Mould

After you have prepared your mould and the dimensions, you need to cut out your mould. It is now where you should use glue to paste your paper with the outline onto the high impact material.

There are three main cutting tools that are available - scissors, big stationary knife, and a small stationary knife. There are advantages and disadvantages of all methods. Scissors are good if you need to make the mould quickly, but can be hard to use and get into small spaces. The small stationary knife is precise, but will take a long time as multiple pushes are needed. I believe the best option is the big stationary knife, as it will cut quite quickly while being able to get into small spaces. Safety is somewhat a concern with this option, so be careful.

After this, you are just going to cut the outline of the dodecahedron. If using the smaller knife, ensure you put lots of pressure into your cuts. Use a ruler when cutting, this will help to prevent injuries (a safety ruler is preferable, as shown in the introduction.)

The final cut out is shown as an image.

Step 3: Preparing Your Mould

Once you have cut your mould, you have to manipulate it to get it into a dodecahedron shape. I recommend using light scoring (lightly cut into the shape.) You will also need to use your hands to bend the shapes. Remember to bend them at the lines that you drew (in between each pentagon.)

Use tape to put each side together.

When doing this step, you should also cut off one of the pentagons (this will be the open top.)

Step 4: Preparing Your Core

After you have prepared your mould, you also need to prepare your core. You can cut out a core using high impact polystyrene, or you can use a PVC pipe and cut out a circle with the same dimensions (to ensure that the cast does not run into the core.) The core that you use should leave some room for the plaster (I used a core about 4cm in diameter.)

Step 5: Making the Liquid Plaster

After you have prepared the mould and core, it is time to prepare the plaster (for the pour.) Firstly, pour the water into the bucket, followed by the plaster. Use a 2:3 ratio (2 parts water, 3 parts plaster.) I used a yoghurt cup and poured out 2 cups water and 3 cups plaster, and this was enough.

Once you have combined the water and plaster, use a stirring tool (I used a spatchula) and mix it together. After you combine, stir for about 1 minute, and do not wait as the mix is time sensitive. If you wait too long, it will harden and will be unable to pour.

Optional - If you would like the final product to be a different color, add 10-20 drops of food coloring. Number of drops and color is up to you - a darker color would needs drops of food coloring and a lighter color needs less drops.

Now, you are ready to pour!

Step 6: Pouring the Plaster

This is the most important step to get right as this is what makes the actual product.

First, just pour a little bit of the plaster inside to ensure that the plaster does not leak out of the mould. If it does, reinforce with tape.

Pour a bit more plaster and check how far it comes up when the core is added. Remember to have the closed side of the core facing down so the plaster doesn't come into the core.

Continue this process until the plaster reaches close to the top (about 3/4 full)

IMPORTANT: Do not place the core all the way to the bottom, leave some room between the core and the bottom of the mould.

Once finished pouring, use tape so that the core stays in place. Let set until hardened (20-30 minutes in my experience.) This is important so you can remove the core later.

Step 7: Final Touches

Once finished pouring and letting it set, you need to remove the original mould. Use a knife to cut open the high impact polystyrene. Ensure you do not cut into the plaster itself when doing this. After finishing this, you should also remove your core. Sometimes this is difficult especially if it has hardened too much or if plaster has gone into the core. Brute force is sometimes required but beware, this could damage the mould. The best method to remove the core is to gently move it back and forth until removed.

A drill can be necessary and helpful, but make sure to not use a heavy drill as this will damage the mould.

After removed, you have the final product! Enjoy using this geometric pot plant.