1. Prepare Your Workspace and Jar: Gather your sourdough starter, flour, and filtered water. Make sure your starter jar is clean. If you’re due for a full jar cleaning, now is a good time to transfer a small amount of starter to a clean jar before feeding.

2. Assess Your Starter: Look at your starter. Does it have any liquid (hooch) on top? This is normal and indicates it’s hungry. Pour off most of the hooch, or stir it in if it’s just a small amount.

3. Measure Out Your Starter: For a typical feeding, you’ll want to use a ratio of 1:1:1 (starter:flour:water by weight). For example, if you want to maintain 100 grams of starter, you’ll take 50 grams of your existing starter and discard the rest (or use it for discard recipes). Then you’ll feed it with 50 grams of flour and 50 grams of water. This ensures you’re not constantly growing an enormous amount of starter.

4. Add Flour: To the measured starter in your jar, add the measured amount of unbleached all-purpose or bread flour. Gently sprinkle it over the starter.

5. Add Water: Pour in the measured amount of room-temperature filtered water.

6. Mix Thoroughly: Using a spoon or a small spatula, mix the flour, water, and starter together until there are no dry spots of flour remaining. The mixture should be smooth and have the consistency of a thick pancake batter. Scrape down the sides of the jar to keep it tidy.

7. Mark the Level: Place a rubber band or use a marker on the outside of the jar to indicate the current level of your freshly fed starter. This will help you visually track its rise and fall as it becomes active.

8. Cover and Wait: Loosely cover the jar with its lid or a piece of plastic wrap. Do not seal it tightly, as the starter needs to breathe and expand. Leave it at room temperature (around 70-75 F or 21-24 C) for 4-12 hours until it doubles in size, becomes bubbly, and passes the float test (a small spoonful floats in water). Once active, you can use it for baking or place it in the refrigerator until its next feeding.