Bentonite is used as a bonding material in the preparation of moulding sand for the production of cast iron, steel, and non-ferrous casting. The unique properties of bentonite yield green sand moulds with good flowability, compactability, and thermal stability for the production of high quality castings. Almost all iron, steel malleable iron casting foundries are using Bentonite for cost efficient results. Bentonite is utilized in foundry to bind the sand grains into desired shapes. Bentonite helps in retaining the mechanical shape of the mould by making the particles of sands adhere to it and also making the surface impermeable. Strength and fusion point are the two important properties desired for selecting bentonite. Primary use is in the production of non-ferrous castings. Mixing ratio depends on the sand fineness and its quality, impurities, clay particles and fineness of sand will affect the Green strength properties.