Australian Dark Rum - Heavy or dark, is made in traditional pot stills with a slow fermentation of up to 12 days. Brown rum, which is different to dark rum, is aged six years in oak barrels. As far as comparison goes, it's similar to brandy, bourbon, or whiskey. A fine brown rum should be enjoyed like a cognac. Dark or brown rums are heavily flavoured and should be used only as an accent in a cocktail, never as a base. But then with the advent of premix's this base is combined to be enhanced with cola, lemonade, soda, and dry ginger ale.