(i) Refractoriness i.e., it should be able to with stand high temperatures.
(ii) Permeability i.e., ability to allow gases, water vapour and air to pass through it.
(iii) Green sand strength i.e., when a mould is made with moist sand, it should have sufficient strength, otherwise mould will break.
(iv) Good flow-ability i.e., when it is packed around a pattern in a moulding box, it should be able to fill all nooks and corners, otherwise the impression of pattern in mould would not be sharp and clear.
(v) Good collapsibility i.e., it should collapse easily after the casting has cooled down and has been extracted after breaking the mould. It is particularly important in case of core making.
(vi) Cohesiveness i.e., ability of sand grains to stick together. Without cohesiveness, the moulds will lack strength.
(vii) Adhesiveness i.e., ability of sand to stick to other bodies. If the moulding sand does not stick to the walls of moulding box, the whole mould will slip through the box.
Properties like permeability, cohesiveness and green strength are dependent upon size and shape of sand grains, as also upon the binding material and moisture content present in sand. Clay is a natural binder. Chemical binders like bentonite are sometimes added if clay content in natural sand is not
WHAT IS MOULDING SAND AND WRITE DOWN ITS PROPERTIES