Bourbon By Maggie Kimberl / September 14, 2015 You may have heard it said water is really important in making good bourbon, but you might not understand why. Part of the reason Kentucky is well-known for bourbon is because we have endless supplies of limestone filtered water, perfect for making whiskey. But why is limestone filtered water so important in making whiskey?“The water is a very important ingredient and is a key reason why the bourbon industry has flourished in Kentucky,” wrote Susan Reiger in Kentucky Bourbon Country. “The state’s limestone geology means that iron is filtered out of the water as it flows over the rock and becomes a sweet-tasting mineral water. Whiskey made from water containing iron would turn black, which is absolutely unappealing.”In fact, the same thing that makes Kentucky’s limestone filtered water superior for bourbon production is also one of the things that make Thoroughbreds flourish here. The calcium and other minerals in the water and bluegrass give horses strong bones.Limestone creek water at Woodford Reserve (image copyright The Whiskey Wash)A natural extension of this concept is found in a product much newer than bourbon- Old Limestone Bourbon Mixing Water. If you’re going to go to all the trouble of making superior bourbon with limestone filtered water, why would you splash tap water in it to drink?“I was talking to some friends at the bar one night and we were talking about the water crisis in California,” says Old Limestone founder Doug Keeney. “Someone said they’re going to make millions pumping water in and I looked at my bourbon and thought what about branch water?” (Bourbon and branch is one way to order bourbon with a splash of water.) Keeney went home and Googled branch water and found out no one was making it. His first product was actually called branch water, but he quickly discovered people didn’t want something with that name, so he changed the name to Old Limestone.Old Limestone is pumped out of a limestone aquifer 130 feet underground and filtered using reverse osmosis, so the mineral content remains intact. Keeney reports calcium and magnesium bond with the carbohydrates in alcohol, so when Old Limestone is mixed with bourbon it gives a smoother mouth feel. In a recent blind taste test, 16 out of 16 people were able to pick out both the branch water alone as well as bourbon and branch made with Old Limestone.Limestone filtered water makes all the difference in bourbon. Nothing else comes close.