Q. Explain System and Parting sand?
System Sand: In mechanized foundries, where machine moulding is employed a so called "system sand" is used to fill the whole flask. Since the whole mould is made up of this system sand, the strength, the permeability and refractoriness of the sand must be higher than that of backing sand.
Parting sand: This sand is used to prevent adhering of two halves of mould surfaces in each moulding box when they are separated. Thus, to ensure good parting, the mould surface(at contact of cope and Drag)should be treated with parting sand or some other parting material. It is also sprinkled or applied on the pattern surface (before the moulding sand is put over it)to avoid its sticking and permit its easy Withdrawal from the mould. The parting sand is fine dry sand. There is other parting material also used in foundry.