Why does Kentucky bourbon taste so great? Underground limestone water could be the key

No one orders bourbon on the rocks with a dash of chlorine.

So when you're sipping Kentucky’s favorite spirit, those additives in purified water shouldn't linger in your ice, either.

More than 95% of the world’s bourbon comes from Kentucky, and our state is famous for it because a key ingredient is our fine, limestone water, which is naturally rich in magnesium and calcium. Arguably most distillery tours in Kentucky tout that coveted water, but it’s one thing to hear about it ― and it’s another to stand in the heart of an old quarry, listening to it rush from a limestone rock wall.

That's how I ended up spending a day in Highbridge Springs Water in Jessamine County, which is the home of Old Limestone Mixing Water. The family-owned business is more than 40 years old, but this premium, filtered, chemical-free bourbon mixing water has been making waves in the spirits world for about eight years.

How this aquifer became one of the first places to bottle water in Kentucky

On a balmy, hot day in early August, Linda Griffin, who co-owns the beverage company with her sisters, met me at the mouth of an old limestone quarry just outside of Wilmore. Kentuckians first began mining here in the mid-1800s, she told me, and once they left, the cave lived a short life as a mushroom farm. Her father, Bill Griffin, bought the farm and then shifted the old quarry into a storage business in 1982. He had the cave floor smoothed over with concrete and installed shelves that today store boxes filled with paper documents for lawyers, medical firms, and the University of Kentucky, among other clients.

The quarry’s aquifer was initially an afterthought, and all these years later, Griffin still laughs about the irony of it all.

Water and paper certainly don’t mix.

But the engineer, who installed the humidifier for the storage business 40 years ago, told the Griffins they had to do something with the water.

“Let’s bottle it, girls,” she remembers her father saying.

At the time Griffin and her sisters couldn’t believe it. This was well before companies like Coca-Cola and Pepsi dipped into the bottled water industry. Louisville had a bottled water producer, but in Lexington, the only place you could find bottled water in the grocery store was in the cleaning aisle to fill steam irons.

“In 1982, people were just laughing at us,” Griffin remembered.

“Are you kidding? I’ve got water,” seemingly everyone told them.

A limestone water bottled specifically for bourbon

Four decades later, pallets of bottled Highbridge Springs Water towered overhead as I gazed at the enormous limestone walls. Names like Toyota, Buffalo Trace and Kentucky State Parks filled cases full of custom label orders. This family-owned business hasn’t been able to keep up with brands like Dasani and Aquafina, but Griffin says, they’ve done well with private labeling.

As she led me away from the dry business side of the quarry and toward the aquifer, our feet carefully stepped around the puddles that dampened the cave’s floor from the summer humidity. A drop of water slipped from somewhere above and landed on top of my head.

The old quarry has a consistent, cool, unwavering 58-degree temperature even on the hottest days and the coldest nights. Over the years, Griffin’s staff has worked through heatwaves, snowstorms, and even a harrowing tornado warning without ever realizing what was happening outside 130 feet above the ground.

It’s impossible to know when, exactly, but at some point in the quarry’s history, limestone miners blasted into a wall with dynamite and hit the underground aquifer. The Griffins don’t know where the spring is drawing from, but they suspect it must be from miles away. Even during the drought of 1988 this accidental, manmade spring never stopped flowing.

The Griffins had been bottling water for more than 30 years when Old Limestone Mixing Water’s founder, Doug Keeney, first approached them about producing a water specifically for bourbon.

Keeney’s brainchild began like so many ideas do — at a bar. The Louisville-based author was sipping on bourbon when he noticed the water in his glass had an odd taste to it. He reasoned good bourbon needs good water, so he contacted the Kentucky producers whose water had the same limestone characteristics as the state's fine bourbon. Highbridge Springs Water and Old Limestone Mixing Water both start at the same underground aquifer in this Jessamine County cave, but Old Limestone has a second filter that elevates the original product.

It all sounds good on paper, but does this $5.99 liter of water really make a difference when you’re drinking Kentucky bourbon?

There is a way to find out.

'Releases the flavor of the bourbon'

Roy Noble, the general manager of Old Limestone, directed me to a placemat with four small sample cups.

“What is this, the Pepsi Challenge for water?” I asked him.

“Something like that,” he said.

First, he poured from a jug of distilled water that came from a big box store. As I sipped on it, the drink felt dull and flat.

Then he gave me a taste of a popular brand of water, and when I really focused on it, I could just barely taste something chemical-like. I Googled that company later, and yes, it does add the smallest amount of chlorine, among other chemicals, to its product.

The third sample came from Noble’s tap at his home in Lexington, and the bleach-like taste was even more pungent there.

“If you put any one of these in your bourbon, there you’re adding chemicals to it,” Noble told me. “It’s actually going to change the structure ... and makeup of it.”

By the time we got to Old Limestone, I’d tasted more hints and notes in water than I'd ever realized existed. This final sample was crisp and full-bodied. If there was such a thing as fine water, this was it. Later that evening when I used it to make ice, it did, remarkably, compliment the bourbon more than the rocks that came out of the ice maker in my kitchen.

“As we go through our process the water comes through the limestone, and it retains some of the calcium and magnesium,” Noble explained. “That’s what releases the flavor of bourbon.”

Kentucky’s limestone water produces the finest bourbon in the world, it's only natural the same water would make a better rocks pour than just about anything else.

More by Maggie: Kentucky only has one native, tropical fruit and it's very rare. Have you tried it?

Features columnist Maggie Menderski writes about what makes Louisville, Southern Indiana and Kentucky unique, wonderful, and occasionally, a little weird. Sometimes she writes about bourbon, too. Reach Maggie at mmenderski@courier-journal.com or 502-582-4053. Follow along on Instagram and Twitter @MaggieMenderski.

This article originally appeared on Louisville Courier Journal: Old Limestone Mixing Water elevates Kentucky bourbon's flavor