First, determine if your recipe calls for Fed, Active, Ripe, or Unfed Starter. (Most of our Sourdough Bread recipes call for Ripe Starter).
Sourdough starter can live forever – if you regularly give it a bit of attention. In other words, you need to clean their house occasionally and feed your sourdough starter regularly.
Sourdough starter is full of living colonies of yeast and lactic acid bacteria. These beneficial microbes consume the carbohydrates and proteins in the Starter. During this process, they ferment and convert those starches into CO2. It is this CO2 gas that provides leavening to your sourdough bread.
When these microbes run out of food, they get hungry and start to slow down. If you leave them alone too long, the whole colony will die (and take your neglected Sourdough Starter out with it).
We keep a 100% Hydration Starter. A 100% hydration sourdough starter is a sourdough culture that is kept and fed with equal weights of water and flour. (If you do not have a kitchen scale, that equates to about 2/3 to 3/4 cup of water for every cup of flour.)
So, for example, if your recipe calls for 200 grams of starter, you will discard all but 300 grams of your unfed starter and add 150 grams of flour and 150 grams of water to produce 600 grams of active starter. After making the recipe you will have 600 grams of starter left to either put in the fridge for up to a week, or for active bakers leave at room temperature to begin the process again the following day.
Healthy Sourdough Starter Stages
Fed Starter – Fed Starter is an active, healthy starter that has been fed within about 2 hours. By hour 2, it will be producing little bubbles on the surface.
Active Starter – Starter is Active about 5 hours after feeding. By hour 5, you should be able to watch large bubbles actively rising through the Starter and making their way to the surface.
Ripe Starter – Starter is considered Ripe about 8 hours after feeding. The volume has doubled, and the top is just beginning to show signs of sagging under its own weight.
Unfed Starter – Unfed Starter is a healthy, vigorous Starter that has not been fed for 12 hours or more. By hour 12, it collapsed after Ripening and is ready to be fed again or put in the fridge until next time. (Note that this is NOT neglected Starter that has not been fed in days.)
Discard – Sourdough discard is the portion of your sourdough starter that you get rid of when you do a feeding. It should be healthy and vigorous, with some small bubbling activity.
If you are not up to making bread, you can always use up extra starter discard by making pancakes, waffles, etc.
Float Test: If you’re still unsure whether it’s ready to use drop a small amount, about 1 tsp, into a glass of water. Do this when the starter is at a peak height before it collapses. If it floats to the top it’s ready to use. If it sinks, your starter should be fed again.