Irish whiskey, once the most popular spirit in the world, comes in several forms. If the whiskey is continuously distilled from unmalted grains, it is referred to as grain whiskey. This lighter and more neutral spirit is rarely found on its own and the vast majority of grain whiskey is used to make blended whiskey, a product made by mixing it with richer and more intense pot still product. Irish pot still whiskeys fall into two categories. Those made entirely from malted barley distilled in a pot still are referred to as single malt whiskeys. The second style of Irish pot still whiskey is single pot still whiskey, made from a mixture of malted and unmalted barley completely distilled in a pot still. This latter style has also been historically referred to as "pure pot still" whiskey and "Irish pot still whiskey".