Sodium Silicate Deflocculates Clay Slips

Slip casting is a common technique used for the mass production of complicated ceramic items. It is made by mixing dry clay with water along with an effective deflocculant like sodium silicate.

Pottery is the common method used to make pots, dishes and other items using clay or other ceramic materials. The potter fashions the piece on the wheel with his hands and it is then fired to give it a hard and durable form. However, there is another technique for making hollow ceramic and porcelain articles in complex shapes that cannot be fashioned on a potter’s wheel. This is known as slip casting of clay, usually along with sodium silicate.

Slip casting is a simple technique of pouring thinned clay into a mold. The mold is filled to the brim and the clay is allowed to settle inside. This allows the slip to build a thin layer inside the mold after which the excess material is drained out. The amount of time the clay slip stays inside the mold will dictate the thickness of the cast.

The clay is allowed to cure and demolded once it starts to separate from the sides of the mold. Usually, slip casting is done in plaster molds as the porous plaster will absorb the water from the slip and allow for quick casting.

When it comes to making the slip for casting, people usually assume that it is done by mixing clay with water. However, this requires a lot of water which in turn will take a long time to shrink and dry. Moreover, the clay may not disperse properly in the slip and will settle at the bottom of the mixture. This is why a deflocculant like water glass (chemical name – sodium silicate) is mixed with the clay before adding water. This will thin the clay or reduce its viscosity by dispersing its particles and thus require much less water. But it should be kept in mind that excess sodium silicate will have an opposite effect and will actually make the clay thicker or flocculate it!

Top quality liquid sodium silicate can be sourced from EnvironMolds at

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