I have spent two days this week preparing the slip cast mild for my goblet. Because of the undercuts in the piece I had to make a mold with five sections so that I will be able to remove the piece after casting.
First I marked out on the print where I would build the walls out to make the mold. Or essentials where the seems would be. After marking out two sections it quickly became clear that 3 walls were needed in order to get the piece out of the mould.
I covered two thirds of the piece in clay leaving just the third visible that would be cast first.
I then smoothed out the clay walls.
I clamped wooden walls around the piece, filled any holes with clay and poured in plaster.
Once dry I took apart the mold and cleaned up the plaster a little. The I drilled in a half dome so that the next part of the mold would lock in.
I washed the plaster three times with soft soap. This was wiped off with a sponge and would keep the next plaster pour from sticking.
I then built the second wall and built up the wooden boards.
This was the result of the second pour after removing the walls and clay.
The process was repeated a third time to create the third wall.
This is the three walls completed and the process took about seven hours to get to this stage.
The top of the mold was then planed back.
Lock holes were drilled into the three walls at the top.
I then built walls around the mold and sealed for the pour.
This process was repeated for the bottom.
The five parts were then planed into one nice block.
This is the final reveal as I took out the 3D print.
The mould has now been placed in the drying cupboard and will be ready to use hopefully in three days time.