Making Plaster Mould of Julie's Hand
Health and Safety - Goggles, gloves and dust masks should be worn when using plaster of paris. The dust can be very irritable against skin and when in eyes. If does get in eyes, simply wash out with water or at the nearest eye cleaning kit. Overalls or long sleeves should also be worn. Plaster gets very hot when curing so it is important to wash any spillages away. When set, its very heavy so take precautions when moving the mould.
- Plastic sheet
- Hot glue gun
- Hot glue stick
- Plaster of paris
- Water
- Scales
- Clay
- Wax soap
- Sponge
There are many different techniques I could use to make the hands for my stop motion puppet. After watching multiple youtube tutorials and surfing the internet for the best approach, I decided to try a couple. My first attempt was made by drawing round my own hand so that I could get the right shape. This was then scanned onto my computer and scaled down to fit my animation puppet. To work this out, I simply worked out the scale first and then applied that to the scanned version. For example to work at 1:25, I would take my hand measurement and divided it by 25. Then taking some thin wire, I began to create the skeleton of the fingers. As I am going to be casting the hand in plaster, I sculpted the hand out of plasticine because it can easily be taken out of the mould. For the casting, I started by creating a small box around the hand from thin plastic sheets and a hot glue gun to stick it together. Its very important to make sure there are no gaps for the plaster to leak out of as this will cause a mess and could effect the moulding process. I then built up clay around the hand so that only half of the plasticine hand was showing. As this is a two-part mould, it means that I can insert the wire skeleton into the casted hand. To make sure that the two halves fit together perfectly and to ensure the cast is accurate, I needed to create some little notches that will jigsaw together. To create these, I simply pressed a wooden dowel into the clay. I also had to create a pour hole in which the casting material will be inserted into when cast. It’s important to leave a big enough hole in a funnel shape as it needs to be wide enough to stop the casting substance from clogging the hole.
While the clay was still damp, I mixed up a small amount of plaster and poured it over the mould. I took a small pot starting with roughly a 1/4 pint of water and then sprinkled the plaster powder into the water little bit at a time. It needed to be the consistency of yoghurt. Too much powder and the plaster wont set. This was left for roughly 25 minutes before the plaster had completely set. I then took this out of the mould and repeated these same steps with the other side. The clay as this is no longer needed, then I rebuilt the plastic sheet walls so that the opposing side of the hand was facing up. To stop the plaster from sticking to the already moulded half, I used some wax soap on a damp sponge. Its important to cover all the mould with bubbles with a couple of layers otherwise the two mould pieces will stick together. To test if the plaster is fully coated and “water-proof’, I dripped a small amount of water onto the surface. If the plaster absorbed the water there aren't enough layers; if the water sits on the top, then its ready to cast the second half. This was left for another 25 minutes until the plaster cured. I peeled away the plastic sheets and took the two pieces apart. I found the jigsaw notches had broken off, so if I was going to do this again, I wouldn't press the dowel in so deep as this made the outward pieces more vulnerable for snapping.
