Molding materials include molding sand, backing sand, facing sand, parting sand, and core sand which are chosen based on their processing properties. The main ingredients of molding sand are base sand (silica sand), binder (clay or other), and moisture. Important properties of molding materials are refractoriness, permeability, strength, flowability, adhesiveness, and collapsibility.

1. Molding Material A large variety of molding materials is used in foundries for manufacturing molds and cores. They include molding sand, backing sand, facing sand, parting sand, and core sand. The choice of molding materials is based on their processing properties. Molding Sand Composition The main ingredients of any molding sand are: Base sand (Silica Sand) Binder (Clay binders, Other binders) and Moisture Vikrant Sharma, Assistant Prof. MITS Lakshmangarh

2. Vikrant Sharma, Assistant Prof. MITS Lakshmangarh

3. Properties Refractoriness: It is the ability of the molding material to resist the temperature of the liquid metal to be poured so that it does not get fused with the metal. The refractoriness of the silica sand is highest. Permeability: During pouring and subsequent solidification of a casting, a large amount of gases and steam is generated. If these gases are not allowed to escape from the mold, they would be entrapped inside the casting and cause casting defects. To overcome this problem the molding material must be porous. Strength: Property of holding together of sand grains. Flow ability: when it is packed around a pattern in a molding box, it should be able to fill all nooks and corners, otherwise the impression of pattern in mould would not be sharp and clear. Vikrant Sharma, Assistant Prof. MITS Lakshmangarh

4. Adhesiveness: ability of sand to stick to other bodies. If the molding sand does not stick to the walls of molding box, the whole mould will slip through the box. Collapsibility: 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. Vikrant Sharma, Assistant Prof. MITS Lakshmangarh