Coral – from prototype to casting

Here is a series of images showing the making of one version of “Corals” for the installation.

Pouring the plaster blank.

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Turning the blank on a lathe.

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Staight off the lathe.

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On the right, after shaping.

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Burying half of “Coral” into oil clay to start the moldmaking process.

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Securing the mold area with cottle boards.

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Then I carefully add a layer of water-based clay on top of the oil clay to make a smooth, even surface that goes just up to the midline of the prototype.

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After I pour the plaster and let it set, I remove the cottle boards and seperate the two sections. I no longer need all the clay.

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After cleaning up the plaster section, it goes back in the cottle boards for a second pour. Prepping the plaster with layers of oil soap and mold release is crucial for getting sections to release from each other, especially when you pour plaster on plaster.

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Just after the second pour.

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The two sections apart and prototype removed. I’m still not done though. This is going to be a three part mold.

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Now the mold is strapped together, empty and upside down. I’ve carefully made a clay seal so that I can make the bottom section of the mold. This will make sure the piece sits steadily on a lowered rim rather than a flat base that would make it wobbly.

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Putting the cottle boards on and getting it ready to pour the bottom of the mold.

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So now I have all three sections I included a hole in the bottom section of the mold for a section of plastic tubing. This will act as the drainage hold when I pour the liquid clay, “slip,” into the mold.

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The setup for pouring the slip into the mold. There is a hole in either end with plastic tubing inserted. For the pour, I’ve blocked up the drainage hole on the bottom with oil clay, and jerryrigged it. After I pour the slip, I let it sit for a while. The plaster soaks up the water in the slip closest to it, thus slowly building thickness. The longer you let the slip set, the thicker the clay wall will be.

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When the slip has set enough, I put a bucket on the floor between the stools, unplug the drainage hole and let all the excess slip drain out into a bucket. I can use that slip again.

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I let the castings set up over night and take them out of the molds the next day. So here are some castings straight out of the mold. The one on the right is the one we’ve been looking at.

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And here is a casting of Coral after I’ve done some hand shaping and smoothing. So there you have it, from prototype to casting. Eventually, I’ll add images after bisque firing, glazing, and the grand finale. Long process, isn’t it?

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One comment on “Coral – from prototype to casting

  1. dewd! you are a pro at the slipcasting. nicely executed, and I am fond of the form – can’t wait to see what a series will produce…
    hearts, rachel

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