Q. Can you explain Bentonite binders?

Its general composition is MgO.Al₂O₃.Sio₂.H₂O. it is formed by weathering of volcanic or igneous rocks. It is a creamy white powder. Its melting point is 1250- 1300^oc

The basic constituent which gives refractoriness to a clay is alumina. Of all clays bentonite is the most commonly used clay. It needs smaller amount of water to obtain a given degree of plasticity. This will result in less stream generation when the molten metal is poured into the mould, permitting a lower permeability in the moulding sand.