Trendy though it may be, recreating an older spirit is no easy feat. It poses a unique set of challenges for distillers, in large part because Prohibition forced the bulk of small family operations to close.
"Following Prohibition, there wasn't any great race to get back in the business," said Pennfield Jensen, executive director of the American Craft Distilling Association. "They just kind of pulled up their roots and went on." That broke the chain of distilling handed down generation to generation, and resulted in the loss of many earlier mash bills, he said.
Surviving mash bills, if you can find them, aren't always easy to decipher, either. "George Washington's recipe was much easier than most would be, because he was a prolific note-taker," said Pickerell. "Though the recipe itself was never taken down, we have intricate detail of his grain purchases." That documentation, along with other known mash bills in the region, helped distillers determine the right ratios of that grain to recreate Washington's recipe. (Watch the video above for more on Washington's role as distiller.)
Differences over time in strains of grain and fruit available, and equipment used, add to the challenge of a perfect replication. "You can take that recipe that had everything from the exact ratios, weights or amounts of product and put it on a different still, and it's going to have its own fingerprint," said Brian Christensen, editor of Artisan Spirit magazine.
But modern adjustments to pre-Prohibition spirits may actually result in a preferable sip. Traditional moonshiners kept the best part of the distilling run for themselves, selling a blend of the harsher-tasting "head" and "tail" cuts, Ball said. Today's craft distillers sell only that best part. "In many ways, the things we're doing are the things the old men knew, but we're using sophisticated equipment for cleaner whiskey," she said. "Our whiskeys are much smoother than typical whiskeys because we've eliminated all those toxins."
(Read more: Roll out the barrel! Craft beer growth jumps again)