The feed can be wet or dry, depending on the subsequent process and the nature of the product.
Dry grinding is necessary with some materials due to physical or chemical changes which occur if water is added. It causes less wear on the liners and grinding media and there is a higher proportion
of fines in the product, which may be desirable in some cases.
Wet grinding is generally used in mineral processing operations because of the overall economies of operation.

The advantages of wet grinding are:
(1) It consumes lower power per tonne of product
(2) It has higher capacity per unit mill volume

(3) It makes possible the use of wet screening or classification for close product control
(4) It eliminates the dust problem
(5) It makes possible the use of simple handling and transport methods such as pumps, pipes and launders]