Bentonite

Bentonite's montmorillonite mineral structure swells in water, forming a colloidal gel network that suspends glaze ingredients and prevents sedimentation. Even at very low dosage (0.1–1%), bentonite provides significant stabilisation of ceramic glaze slips, engobes, and casting slips.

Bentonite is used at very low dosages — typically 0.1–1.0% by weight of the dry batch — due to its high swelling capacity and colloidal activity. Higher dosages can adversely affect the rheology, making the slip too thick or reducing casting rate in sanitaryware production.

Bentonite acts as a colloidal binder in the ceramic slip, improving the cohesion between ceramic particles during drying. This better bonding reduces differential drying stresses, lowering the tendency for crack formation as moisture evaporates from the green ceramic body.

Yes. Bentonite is used in casting slips to improve rheological stability and green strength, and in glaze formulations to prevent glaze settling and improve adhesion of the glaze layer to the ceramic body before firing.

Iron, manganese, and other colouring impurities in bentonite can cause discolouration (grey, cream, or brown tones) in the fired ceramic glaze or body. High-purity white bentonite grades are specifically refined to minimise these impurities, ensuring no adverse effect on the fired whiteness of premium ceramic products.