Differences between Grain and Malt Whisky.
Grain whisky production is a continuous process in a column (or Coffey) still using un-malted cereals that can be bought on price.
Single malt whisky is a batch process in a pot sill that has to be cleaned in between and uses only malted barley an extra process that adds to cost
Because of the way the grain distillation works the grain spirit produced is lighter in body and matures quicker than malt spirit.
Also the light grain spirit does not have the influence of kiln or smoke dried malt barley. Producing lightly flavoured whisky ideal for a cheaper infill to be used in blended whisky.