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Casting lesson - Splice Moulds

I am looking for ways to reproduce some of the objects inherited from my parents and am considering making a mask or some kind of body sculpture with them. Splice moulds were suggested as a way forward to to do this, I took along some of the ceramic Egyptian souvenirs to get started with, along with the cardboard from toilet rolls & a glue stick.

Items needed: Hot glue gun, cutting block, dowel, Risers (thinner stick bits).

Use a board to work on, cut the dowel to about 1 to 2 cm long. Glue the dowel the down to the board as this will be your pour hole, and the object to the dowel. Try and consider the detail and which way the silicone will flow around the object. If possible stand any detail if forward and mark the sides you will cut to get the item out of the mould.

I was also trying to cast a bell as I knew this would be tricky but wanted to experiment with a difficult object as well something more straight forward. Here as well as the pour hole we added risers, at the end and lowest point of the object, this is important as it allows any trap air in the silicone to rise out of the mould without missing any area. Then I put the toilet rolls around the objects and glued them to the board, trying to be as neat as possible,(not that simple),so as to prevent any holes around the base of the roll.

Next: SPRAY YOUR OBJECTS WITH RELEASE AGENT - VERY IMPORTANT!! Or you objects will not come out of your mould.

To mix the silicone you mix the silicone amount + 10% silicone catalyst. Stir well all around to get the mixture even, then place in the gas tank, this will remove any air from the mixture.

Switch on the Gas tank and turn the taps on the tank the opposite ways to how they are normally facing, this will remove the air from the tank. Slid the lid on & press down so the pressure seals it shut, the mixture will bubble and rise, as it goes back down turn machine off, return the taps to the normal position and take out your mixture, Its a lovely silky constituency. Mark 1cm above your object then try to pour around the object, between it and the side of the rolls trying not to spill any over the side, (this is really hard!). This way the object has more chance of staying upright, also you can see if there any holes in the base, if liquid begins to seep out use the glue gun to stop it. It takes about 24 hours to set.

To release the object pull it out of the cardboard roll and cut with a scalpel down the sides of the mould until you can it slid out. When you have holes in your object cut the the strands of silicone on one side of the mould, they will replicate when you cast your object. Also it's good to make the pour hole slightly bigger around the top, so you can pour your substance easily into the mould when casting.

Jesmonite Casting

Jesmonite is good to use as it's like plaster but tougher, colour can also be added in the form of jesmonite power, I went for the blue. Tape up moulds to stop leaking.

Jesmonite mixture is 2.5 powder to 1 jesmonite liquid, then add colour. The pigment is strong so not much is needed, I think I used a little too much. Then pour into mould.

Give it another 24 hours to set, remove tape and slide out object. Remove the pour hole with a small hack saw under an extractor fan as the dust is toxic.

I was really pleased with the results, the details that is retained is very close to originals apart from the bell, I had stuck on it's side and didn't work at all, it fell apart as it came out, it may have better more successful with the open bit facing upwards. I need to experiment further with this.

I did return to continue casting some more objects just before the Christmas holidays, however I read the scales wrong and didn't put enough silicone catalyst in the mixture. After 2 days it was clear it wasn't going to set and had leaked everywhere! I had the glorious job of pulling out my ceramic objects and cleaning them off with white spirit.

NB: I want to learn more and play with what I can create in this process, this is a good way of helping me developing my ideas in sculpture.

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