Green-sand Core
The inner mould, whose outside surface has been fashioned to correspond with the desired form of the inside of a casting, and which has been constructed exclusively from materials favorable to a successful issue without the intermediate process of drying consequent upon cores that are made from dry-sand material. The chief requirements in this mode of core-making are, first, a suitable core-bar, or arbor (see ARBOR), to carry the sand; second, a tough, strong sand for the lower hanging surface, the upper surface and the interior of the core being formed with sand as open as may be consistent with safety; and thirdly, an uninterrupted passage for the vents if they are open ones; but in large cores cinders are always preferable. See FACING-SAND; GREEN-SAND MOULDING.
Green-sand Moulding is the art of constructing moulds capable of resisting the destructive influence of molten metal without the subsequent drying incident to loam and dry-sand moulding. More skill is required to mould similar castings in green-sand than by either of the other methods, because the moulds cannot possibly be made as rigid and unyielding; therefore there must be superior ingenuity displayed to overcome these disadvantages. Every process connected with green-sand work must be worked with greatest care, provision for sustaining and anchoring cores and portions of mould must be made independent of the mould proper, and in all cases the efforts of the moulder are directed to a maintenance of all the parts of his mould in their exact position without actual contact, otherwise the incoherent material out of which he must necessarily form the mould will be shattered and the mould destroyed. This is by no means the case in loam and dry-sand moulding: the dried loam or sand is compact and hard, and in most cases capable of sustaining its several parts without fear of damage, in addition to which the dried moulds offer a surface always freed from moisture and gas-creating substances, the eradication of which in green-sand moulds must necessarily take place during the process of filling the mould with metal. See DRY-SAND MOULDING; LOAM-MOULDING.