Wine and whiskey barrels don’t look the same. Wine barrels usually look newer, cleaner, and somewhat lighter in color. Wooden parts don’t have any defects on them, and hoops are made from zinc-coated steel. Whereas whiskey barrels’ staves are shabby, rough, and joined by blackened steel hoops (which are, mostly, to match the style). Whiskey casks may be covered with knots, which can cause leaks of the product. The reason is that coopers are simply using a better wood for wine barrels to avoid this. You don’t want bacteria to interfere with the complicated process of fermentation. For hard liquor, like whiskey, it’s not so vital. Also, considering the texture of whiskey, it’s less likely to leak through the small gaps, where wine would probably leak out. As a result, staves that do not meet standards for wineries are often used for making whiskey barrels.