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Outcome

Slip casting is one of the best pottery forming techniques for replicating models precisely, especially over a longer production run.

Materials

  • Ceramic casting slip (Defloculated)
  • Water for cleaning up

Equipment

  • Gypsum mould
  • Plastic jug (Size to hold the capacity of the mould)
  • Fettling knife
  • Rubber bands (Sliced car inner tubes)
  • Buckets for slip
  • Container to drain moulds

Step 1

Ensure your mould is clean and dust free.

Place mould on a strong level table.

Close mould securely with rubber bands

Place the slip bucket and all equipment within reach

Step 2

Double check the slip is smooth and has no lumps. If it does, strain the entire bucket with a fine sieve, into a clean bucket of the same size. The slip needs to be the consistency of smooth pouring cream.

Pour sufficient slip into the clean plastic jug.

Smoothly pour the slip into the cavity of the mould. Erratic pouring my result in lines or imperfections in the surface finish of the pot.

Step 3

As the water is absorbed into the gypsum (Plaster of Paris), so a wall of clay is deposited onto the inside of the mould, this becomes the wall of the pot. You may need to top up the mould with slip as the material settles. This happens within minutes of the initial pouring.

No blow gently on the surface of the slip in the mould, away from the wall. This will give you an idea of the thickness of the pots wall.

Once the wall is the required thickness (4-6mm) gently turn the mould onto the rim of the draining container. Slowly allow the excess slip to drain. Leave it for about 15 to 30 minutes, depending on the temperature and humidity. The excess slip must have all drained away and the pot  wall clearly formed and leather hard.

Step 4

You can now very carefully open the mould, ensure the mould does not catch the rim or sides of the pot. Carefully place the pot on a rigid board lined with a piece of telephone book paper. This allows the pot to move as the pot shrinks.

Once the pot is a bit harder, you can fettle any excess clay. Do not try to finish the pot until it is bone dry.

Once the pot is bone dry, you can sponge it with a damp sponge or fine scotchbright. If it has fine detail, handle with extreme care as to not damage the surface detail.

Step 5

Allow it to dry completely, then bisque fire.

Decorate and or glaze the pot

You now have a perfect pot, which can be replicated each time. If you want to increase the production volume, simply increase the number of moulds. It may be worth investing in a master mould then, as you can cast your own moulds.

We hope this simple Blueprint gave you an overview of Slip Casting Ceramics. 

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