Greensand Casting Sand

Green sand is moulding sand that is used damp: fine silica sand bound by a little clay and water, so it packs firm round a pattern, holds a sharp shape, and lets steam escape when hot metal is poured. 'Green' means unbaked, not the colour. Bentonite clay is the usual binder; the mix is tempered with water until a squeezed handful holds its shape and breaks cleanly.