How to cast a model

Materials you will need:

  • Plastic container/ bowl
  • Thick paint brush (you won’t mind ruining)
  • Vaseline petroleum jelly
  • Plaster of Paris
  • Water
  • Foam core
  • Stanley Knife
  • UHU glue
  • Air drying clay
  • Cutting mat
  • Plastic Sheet
  • Pencil

Note: All of these materials can be purchased at your local hardware store!

To being, gather the first round of materials, you will need to make a mould for your plaster. This will require; cutting mat, foam core, pencil and a Stanley knife.


Start by marking the measurements for your foam core model. Foam core is best used when casting plaster as it is easy to create the shape you desire as well will not hinder/stick to the material.

Then, cut the desire shape by using a stanley knife. Apply pressure to the beginning and end of your cut while lower your pressure in-between. This will determine a more accurate and cleaner cut.

Once the cut has been made, it is easy to simply snap the foam core off.

Note: make sure to add a few centimetres off your actual measurements as this will help during the casting process

Next, start gluing your pieces together. UHU glue is a reliable adhesive when dealing with foam core as most other glues tend to melt the foam!

As shown, glue the pieces while allowing a bit of space. This will ensure in stability and avoid leakage of the plaster.

To add shape and depth to your model, start placing and gluing pieces of foam core with your model as show to your liking.

Now to move on to the actual casting. Gather your materials; plaster, a thick paint brush, plastic container, air drying clay and Vaseline petroleum jelly.

For extra security, seal the edges of the model with air drying clay to avoid the plaster from leaking out and breaking through during the drying process

Once you are satisfied with your mould base, layer Vaseline on the inside as a releasing agent. This will make the plaster cast to come off more easily once it has been dried.

Note: lay a plastic sheet or any kind of protector during this process to avoid mess! (I used a garbage bag)

Once your mould has been made, you can now start making the contents to go in it: plaster!

Add the desired contents of your plaster on to a plastic bowl, then add water. It should be a 2: 1 ratio, however the consistency should be gooey and not watery. If it is too watery, add a bit more plaster. (this will speed up the drying process)

Use a thick paint brush or even your hands to mix the water and plaster, make sure there are no chunks in the mixture.

Pour in the mixture to the mould.
Gently shake the sides of your model to get rid of air bubbles.
Place a heavy weight next to your drying model it give it support and avoid collapsing.

And then we wait!

Allow the cast to completely harden by checking in every hour (best to leave overnight).  Then simply take off the foam core mould.

And voila! You should now have a casted model.

Don’t be afraid to experiment by adding colour to your cast, Acrylic works best!

Everyday materials can also be used for readymade moulds such as egg cartons, milk cartons, bowls etc.

Happy casting!