Slip Casting
Stages Involved
Pouring of slurry into a porous mould
Extraction of water into moulds through pores
Forming of solid layer on surface of mould
Excess slip removed (except solid cast)
Type of Casting
Drain Casting
Solid Casting
Advantages
Used for complex shaped products
For big/bulky products
Holloware such as teapots tembikar, sanitarywares,and figurines
Disadvantages
High reproducibility rate
Any form of ceramic suspension is possible as it is chemically stable with right concentration
Long processing time
Drying is needed for cast and working mould
Requires large working area
Important Criterion
Slip(Slurry) requires high solid content with controlled amount of water, with suitable of viscosity
Produced cast with good properties such as dense,solid with good green strength and not easily cracks
To enable flowability, transportation, casting
Viscosity level (fluidity) is prepared without sacrificing high solid content ( about 70% solids)
Viscosity increase, fluidity decrease
3 Parameters need to be controlled
Slip density
viscosity
thixotropy
Form of Casting
Bench Casting
Baterry Casting
Requirement of slurry
High solid content
Suitable slip viscosity
Suitable thixotropy
Stable and no chemical reaction
Addition of electrolyte ( known as deflocculant or dispersant) will reduce the viscosity to a minimum point before increasing the viscosity again
Common deflocculant: Na Silicate, Na Hexametaphosphate (Calgon), Na carbonate,Dispex, CMC
Viscometer
Torsional viscometer
Brookfield viscometer