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SLIP CASTING OF WHITEWARES (Definition (Slip casting is a ceramic forming…
SLIP CASTING OF WHITEWARES
Definition
Slip casting is a ceramic forming technique for the mass-production of pottery and other ceramics, especially for shapes not easily made on a wheel.
The technique is suited to the production of complex shapes, especially if with relief decoration and thin walls. Much modern fine factory porcelain is made by the technique, very often the entire production. It is also commonly used for sanitaryware, such as toilets and basins, and smaller pieces like figurines and teapots
An additive with deflocculant properties, such as sodium silicate, can be added to the slip to disperse the raw material particles. This allows a higher solid content to be used, or allows a fluid slip to be produced with a minimum of water so that drying shrinkage is minimised, which is important during slipcasting
Stages involved
Pouring of slurry or slip into porous mould :arrow_right: Extraction of water into moulds through pores or voids in mould :arrow_right: Forming of solid layer on surface of mould
:arrow_right: Excess slip or removed (except solid cast)
Advantages of slip casting
1)Used for complex products
2)Used for big and bulky products
3)High reproducibilty rate with smooth surface and fine details to original design
4)Any form of ceramic suspension
Type of Casting
Drain casting
The mould is inverted to drain excess slip after a semi-solid layer has been formed, thus producing a hollow product.
1) Slip is poured into mould cavity
2) Water is absorb into plaster mould to form a firm layer
3) Excess slip is poured out
4) Part is removed from mould and trimmed
Solid casting
To produce solid products, adequte time is allowed for entire body to become firm
1) Slip poured into mould
2) Water is absorbed
3) Finished cast
Requirement of slurry for slip casting
1) High solid content
2)Suitable slip viscosity
3) Suitable thixotropy
4) Stable, no chemical reaction and particles always in suspension
Factors influence casting process
1) Solid concentration and rheology of slip
2) Distribution of pores size in mould
3)Permeability of cast layer
Disadvantages of slip casting
1)Long processing time
2)Need to dry cast and working mould
3)Requires large working area
4)Problem relating to prefential allignment
