Ginger beer starter is called a ginger “bug” (see ingredients above). Think of it as something similar to a sourdough or yogurt starter. The ginger bug is what ferments the ingredients, transforming them into something new. To make the bug, just throw some ginger along with some sugar or honey or any other source of simple carbohydrates in a shallow jar or ramekin. The amounts don’t matter much. Stir, then cover with a paper towel fixed in place with a rubber band. Let the mixture sit for a few days until it starts to bubble (you’ll see bubbles on the surface in a couple days), making sure to stir daily.

A few things to note here — the ginger is naturally covered in lactic acid bacteria and yeasts just waiting for a suitable food source and an anaerobic environment to start growing (as long as it’s organic… otherwise there’s a good chance it’s been irradiated). There’s no chance at all of this starter “spoiling.” It won’t make you sick. The idea is that by keeping everything submerged under water, an anaerobic environment, lactic acid bacteria and yeasts are the primary microorganisms that can thrive. Once they really get going, they out-compete anything else and take over. These lactic acid bacteria and yeasts are the “live cultures/ probiotics” that have been all the craze these past couple years. Supposedly they’re quite good for you. Anyway, by stirring the starter once a day or so, you can prevent any surface molds from starting, and you shouldn’t have any problems.

Carbonation is the process I warned about earlier: as the microorganisms feed, they release carbon dioxide. As it builds up, the ginger beer carbonates, and once it’s sufficiently carbonated, stick the ginger beer in the fridge. The cold temperature slows the microorganisms down, meaning that the process of carbonation will continue, but slowly enough that if you drink the ginger beer in a couple of weeks, it won’t change that significantly. It can be tricky to get the timing of when to stick the bottle(s) in the fridge, but it’s better to err on the side of too soon. Because the ginger beer is alive, you can always leave it out a little longer. If you leave it out for too long, again, it can explode. Sandor Katz suggests filling a plastic bottle up with some of the ginger beer as a useful metric. When the bottle gets pretty hard to squeeze, you know the pressure inside is right and the beverage is carbonated. At the very least, make sure you keep your ginger beer inside a paper bag or cardboard box when it’s carbonating, just in case you forget about it.