Immigrant farmers of Irish and Scottish heritage developed Canadian whisky in the late 18th century. Without the means for traditional processing, alternative distilling practices were incorporated to give Canadian whisky its individual, characteristic flavor. Produced on the basis of cereal grains, the dominant, base ingredient is typically corn, with rye, wheat and barley being used as blending agents to produce a distinctive flavor. The actual recipe of a brand, in particular the portion of each of the cereal grains used, is what characterizes the whisky and sets it apart from its contemporaries. Canadian whisky also uses the unique process of clean heat, which eliminates the smoky flavor found in Scotch whisky. The vast majority of Canadian whisky is distilled in column or continuous stills to produce a very neutral, light product that is free of many of the congeners found in Bourbon and Scotch. The young whisky is then aged for a minimum of three years, in re-charred oak Bourbon barrels before the filtering and blending stages. Depending on the individual recipe, the flavoring whiskies used for blending may be produced in either pot or column stills, creating tastes that are both diverse and exceptional.