During the summer Larry does ceramic sculpture in the barn. I’m sure there are many ways of slip casting stoneware but I thought I’d follow him around with my camera and show you how he does it.
20 years ago he made half a dozen plaster moulds by pouring the plaster between two different diameters of tar paper rolled into tube shapes. The moulds in this picture he varied by lining the tar paper with bubble wrap before casting the plaster.
To make a slip cast ceramic cylinder he starts by mixing water and clay to make the slip.
Then he situates his plaster mold on top of a board with a drilled hole in it which he uses a cork to plug. He temporarily seals around the mould with clay to prevent the slip from leaking out and places the slip bin underneath everything before filling the mould with slip.
The slip sets for about 15 minutes depending upon how thick you want the cylinder walls. When he thinks it’s been long enough he pulls the cork out and drains the slip back into the slip bin. Once this is done you can carefully move the mould (which now has a thin layer of slip in it) out of your way to dry.
Drying times vary depending upon humidity, slip consistency, and air temperature but these set for about 24 hours. Once the clay has separated from the mould (much like a cake separates from the cake pan when it’s done) you should be able to carefully lift the mould straight up and off of the cylinder.
The clay is still going to be damp and will need to dry completely, remaining fragile until bisque fired. After firing it can be glazed, or painted, or smoked, or some combination of all three depending upon what kind of color or surface texture you are trying to create.
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