Experimenting with silicone rubber

Plaster casting step 3

With my plaster casts I created silicone rubber impressions.


What you will need:



Rubber mixing bowl

Plastic spatula

Rubber gloves

Work bench


Here is what I did:

  • The amount of silicone you will need depends on the depth of your plaster casts.
  • Mix four heaped table spoons of silicone with one cap full of catalyst.
  • Mix well until the  viscosity of the mixture changes and becomes stiffer when stirring.
  • From arms height, drizzle the liquid into the centre of the plaster cast.
  • When you have dropped all of the mixture into the cast, give it a vigorous shake/tap to disperse the air bubbles.
  • Leave to set for a couple of days.
  • When the silicone is set you can peel it away from the plaster mould.


The plaster casts can be used indefinitely to create as many impressions as you like.

Happy experimenting!


Plaster Casting

Step two – working with clay / plaster casting

To view the first step in this process please see my previous post on Working with clay.

Once I was satisfied with the markings on my clay pieces it was time to cast them in plaster.

If you are new to plaster casting and would like to try it for yourself follow the instructions below.



What you will need:

Casting Plaster

Rubber Bowl

Cold tap water


Work bench


What to do:

  • Half fill a mixing bowl with cold tap water.
  • Sprinkle a hand full of plaster powder into the bowl.
  • Repeat this step a hand full at a time until the plaster begins to form a heap onto of the water’s surface.
  • Once the plaster powder has formed a heap, stick your hand into the bowl and begin mixing the plaster with the water.
  • Break up any lumps you can feel.
  • If the mixture feels runny you will need to add more plaster (it should be the consistency of double cream.
  • Once the desired consistency is reached, dribble handfuls of plaster over your clay moulds.
  • When you have covered the clay with a thin layer of plaster, gently give it a shake to disperse of any air bubbles.
  • The surface of the plaster will begin to thicken and become cheese-like. Use a ruler to square off any spillages of plaster.
  • Dribble another layer of plaster over the first layer and repeat until you have built up about four layers.
  • Use the ruler again to square off any spillage’s.
  • Cover with clingfilm and leave to set for a few days.


To view the final steps in this process please see my next posts on Plaster casting part two and Experimenting with silicone rubber.