1. Feed Your Starter: Take your active sourdough starter out of the fridge (if it’s already stored there) or from your counter. Discard all but about 50-100 grams of your starter. This helps maintain a manageable amount and ensures your starter gets a fresh meal.

2. Add Flour and Water: To the remaining starter, add an equal weight of flour and water. For example, if you have 50 grams of starter, add 50 grams of flour and 50 grams of filtered water. Use your kitchen scale for precise measurements.

3. Mix Thoroughly: Stir the mixture well with a rubber spatula or spoon until all the flour is fully incorporated and there are no dry pockets. The mixture should have a consistency similar to thick pancake batter.

4. Let It Activate: Cover your starter loosely with a lid or plastic wrap and let it sit at room temperature for 4-12 hours. You are looking for signs of activity: bubbles forming on the surface, an increase in volume (it should double or almost double), and a pleasant, slightly sour aroma. This step is crucial; you want to refrigerate an active, well-fed starter, not a hungry one.

5. Prepare for Storage: Once your starter has peaked or is very active, give it one last gentle stir. Make sure your storage jar is clean and dry.

6. Transfer to Fridge: Place the loosely covered jar of active starter into the refrigerator. A loose-fitting lid or plastic wrap with a small vent is important to prevent pressure buildup while still protecting it from drying out.

7. Weekly Check-In (Optional but Recommended): While in the fridge, your starter can typically go 1-2 weeks without feeding. However, if you plan to store it for longer, or if you notice a layer of dark liquid (hooch) forming on top, it’s a good idea to take it out, discard some, feed it, let it activate, and then return it to the fridge.