Question

_________________ is used as the core coating medium.

(a) Fire Clay

(b) Plumbago

(c) Bentonite

(d) Cement

This question was posed to me in an online interview.

This intriguing question originated from Types of Binders in the Moulding Sand, Types of Base Sand in chapter Casting Processes of Foundry and Forging

Answer 1

Right choice is (b) Plumbago

To elaborate: Just like mould coating, Core coating is also done. It is known as Core washing, dressing etc. Core Surfacing is done my Plumbago or Silica Flour. Plumbago is obtained from plants and imparts a good finishing. It is applied by dipping, spraying etc.