In the kitchen at Cozy HQ, a large glass jar holds a slimy, two-inch thick disc floating in murky brown liquid.

The disc is alive; it’s a SCOBY, an acronym for “symbiotic culture of bacteria and yeast.” Essentially, it’s a colony of organisms that ferments things, including the sweet tea in which it bathes. Eventually the SCOBY will turn the tea into kombucha, a tart beverage packed with probiotics and a hint of carbonation.

Rob Galanakis, Cozy’s VP of engineering, is the person behind the project. He keeps the company fridge stocked with kombucha by fermenting one batch at a time in the large jar before transferring the drink to smaller bottles.

“It seemed like a nice thing to do,” he says. “I like to make and share food.”

His role as kombucha maker—and SCOBY caretaker—earned him the title “fermenter in chief.”

For two-and-a-half years, Rob lived in Iceland, where he worked for a video game developer. While he was there, he developed a taste for new foods, from fermented shark to dried fish with butter. He also ate a lot of skyr, an Icelandic sour yogurt, but he couldn’t find anything comparable when he moved back to the U.S.

In search of a replacement for the probiotic health benefits of the yogurt, he started buying and drinking kombucha. Then he realized he could make the drink himself.

He made a few batches at home (his son loves the stuff), and when he saw some Cozyans drinking store-bought kombucha, he had an idea. Rob bought a five-gallon glass jar, got a SCOBY from one of his wife’s friends, and brewed his first batch of kombucha at the office using loose tea, cheesecloth, and some near-boiling water from an instant hot water dispenser.

Since making that first batch of kombucha, Rob has experimented with different ingredients. He replaced black tea with yerba mate then coffee (black tea is best, he reports). He’s also made other fermented foods and shared them at work: pickled eggs in beet juice, mead, sauerkraut, and non-alcoholic berry sodas.

Since the SCOBY grows vigorously, and can take on what Rob says is “much more than the mass of a small dog,” he’s peeled off layers for coworkers who want to make their own kombucha at home. One time Rob turned a layer of the SCOBY into bite-sized dehydrated nuggets using his food dehydrator. The result? Scoby Snacks.

Even though the SCOBY isn’t on payroll, Design Director Dave Handlong thought it needed a name. Now it’s known as Scoby Macguire, which beat out runners-up Scoby Bryant and Scoby Keith.

When a batch of kombucha is fermenting, Rob tastes it daily to see if it’s reached the perfect equilibrium of tart and sweet. Sometimes, when that day arrives, he’s too busy with work to move the kombucha into bottles. After all, the evolution of the kombucha isn’t something he can predict, part of the beauty of fermentation.

“You can guide the process,” he says, “but ultimately, you’re not in total control.”

Rob doesn’t follow an exact recipe, which leads to surprises and variations in flavors. It’s all part of the fun, he says.

Here’s Rob’s approximate recipe for kombucha:

  1. Use about 10-15 tablespoons of plain loose black tea per gallon of finished kombucha. Put the tea into a piece of cheesecloth and tie it with a string to form a “teabag.” Make sure the water has room to circulate inside the bag.
  2. Steep the tea at a relatively low temperature (150-170℉) for a couple hours. Be sure to brew a highly concentrated tea, so you can cool it off by diluting it with cold water (step four).
  3. After the tea is brewed, remove the teabag and add granulated sugar to taste. Use less sugar for a shorter ferment and lighter flavor, or more sugar for stronger sweet and sour flavors. Rob usually aims for an overly sweet Southern-style sweet tea.
  4. Add cold water bring all the liquid to room temperature. Add some existing kombucha (about 10% by volume) and your SCOBY. Add room temperature water to achieve your target volume. If your SCOBY sinks, don’t worry, it’s probably just the water temperature or new environment.
  5. Taste each day to see how it’s coming along. You should taste the result of fermentation after a couple days. If you don’t, give it longer. If your SCOBY is on the surface and has no mold on top, it’s probably fine. If it’s been totally on the bottom of a week and your tea has no bubbles if you stir it, you may have a problem. When in doubt, remember to trust your tastebuds and believe in your SCOBY.
  6. You can improvise in countless ways, which is part of the fun!

If you’re interested in learning more about wild fermentation, Rob recommends reading “The Art of Fermentation” by Sandor Ellix Katz.