A brew day at The Libertine Pub (Morro Bay, California) is unlike one at any other production brewery in the country. Tyler Clark, the brewpub’s owner and brewer stands over a steaming kettle with a super-heated rock held in a pair of metal tongs. Watching through a pair of yellow safety goggles, he dips the lava rock into the steaming wort.
The smell of caramelized wort wafts up, and steam dances like smoke on the surface of the barely rippling liquid before rising up to the low-hanging rafters just above that are coated in grain dust accumulated over two years of pouring milled grain into the nearby mash tun.
Known as stein brewing (stein is German for stone), this process of using superheated rocks—instead of steam or a direct fire—to heat the wort makes The Libertine unique among American breweries. (Try your hand at stein brewing with Clark’s Tart Golden Ale Recipe.) Others have employed the process, but only Clark and The Libertine use it full time. And as fascinating as the process is, it takes a backseat in importance to everything that happens next—namely, the spontaneous fermentation and oak aging.