Skills Rotation: Plaster Moulds

In this two week workshop we were taught how to create plaster moulds to produce press moulded pieces from clay. Last time I produced a plaster mould was 3 years ago during GCSE when I produced latex prosthetic makeup wounds, so I was excited to repeat the process at a higher skill level. 

We were told to bring in an object that we wouldn't mind getting ruined, and all I could really find was an old barbie doll from when I planned on making my own prom dress. I decided to create a two piece mould as I'd only ever made a one piece mould before, and prepared the object for moulding by removing the clothing and I pulled her head off so the hair didn't get stuck in the clay. I rolled out a clay base, then built up walls half way up the doll's body and outer walls that were at least 1 inch above the highest point of the object. I ensured there was a pouring hole and no undercuts, as well as adding key holes so the second piece would lock together with the first. 

Next I mixed the plaster by sprinkling the powdered plaster into a bucket of water and mixing it with my hand - squeezing out any lumps and removing air bubbles. I poured this into my clay forma and left it to cure for at least 24 hours before de-moulding.

For the second piece I followed the same process, but before I could do this I had to clean the object, wall up undercuts and add 3 layers of a soft soap release agent as I was adding plaster to plaster. 

Finally I cleaned my two piece mould with a damp sponge and it was then ready for me to make a cast from the plaster. 

I really enjoyed this process and I would like to try including it in my other college projects. However, next time I need to keep in mind the few mistakes I made:

• I used the doll's neck as a pouring hole but and built the walls around the legs so when the cast was made the material I pour into the mould would go straight through, so I would need to fill these gaps with clay before casting.
• Do not mix the plaster to vigorously as it can add air bubbles and make the plaster set before it's poured it into the clay forma.