Plainsman Clays | SOAS
Soda Ash
Soda ash is sodium carbonate, and in ceramics it is used mostly as a deflocculant in casting slip. A very small amount thins a slip that would otherwise be too stiff to pour.
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Soda ash is a deflocculant, and it acts on the clay and on the water at the same time. The sodium attaches to the clay particles so they repel one another instead of clumping, and the carbonate takes calcium out of the water and drops it out of solution, so the same dose behaves differently in hard water and soft. A slip commonly uses a fraction of one part in a hundred of the dry clay weight, usually together with a second deflocculant. Past the optimum the effect reverses, and adding more makes the slip thicken again. Soda ash also absorbs moisture from the air and sets into hard lumps. Keeping this material stored in an arid or sealed environment helps to keep the product useful when you go to use it.
- Sodium carbonate, a deflocculant for casting slips
- The sodium acts on the clay, the carbonate on the calcium in the water
- A fraction of one part in a hundred of the dry clay
- Absorbs moisture and sets into lumps, store this in a sealed or arid environment
