In my book Sourdough, I detailed how to begin a sourdough starter culture using a yeast water method whose vigor I find encouraging to many beginning bakers. However, all you really need to get a culture bubbling is some quality flour and pure water to farm the microbes responsible for fermentation. Set it in a warm spot (70 to 75°F is ideal), and in about 1 week, you will have a responsive culture that is ready to leaven bread.
In a small bowl, stir together 60 g / ½ cup flour and 60 g / 6 tablespoons water to form a thick and sticky mixture with no dry lumps remaining. Cover loosely with cheesecloth or a clean towel and set in a warm location for 2 to 3 days or until you detect a light, boozy scent and see bubbles breaking the surface. Discard half and add another 60 g / ½ cup flour and 60 g / 6 tablespoons water and stir to combine. Replace the cheesecloth and allow to ferment at room temperature for 8 to 12 hours. The mixture should be bubbly and active after this time.
Discard half of the mixture and add another 90 g / ¾ cup flour and 90 g / ½ cup plus 1 tablespoon of water. Allow to ferment again for 8 to 12 hours. Once it is fragrant with a creamy, yeasted scent, perform the float test by dropping a dollop of the starter into a cup of water. If it floats, the wild yeast is active enough to produce carbon dioxide gases as a by-product of fermentation. If it sinks, perform one or two more feedings or extend the feeding time before trying again.
Once your new culture passes the test, feed it daily with equal parts flour and water to the weight of the starter. (For example 90 g starter + 90 g water + 90 g flour = a 1:1:1 ratio.) This will produce a starter that is 100% hydration for the recipes in this book. Feed it daily if kept at room temperature, or store it in the refrigerator and feed it weekly, always discarding (or using!) some, but not all, of the
original starter before each feeding. I like to keep at least 2 heaping tablespoons of starter (about 50 to 60 g) on hand at all times.
Store your starter in a jar with a loose-fitting lid to prevent it from drying out. Mason jars with a flip top lid are excellent, as the rubber gasket can be removed, allowing the lid to be fully closed but still loose.
Sarah Owens is a New York City based cookbook author, baker, horticulturist, and instructor. She was awarded a James Beard for her first book Sourdough and released her second in August 2017 titled Toast & Jam with Roost Books. Sarah curates private dining events, cooks for public pop-up dinners, and teaches baking and preservation gobally. Her subscription and wholesale bakery BK17bakery.com is located seaside in Rockaway Beach where she also teaches the alchemy and digestive benefits of natural leavening.