Here are some go-to signs of what an active starter will look like:
The starter has doubled in size (I track this growth by putting a rubber band on the outside of my jar)
You can see plenty of bubbles on top and all throughout the starter. Some may be small or large, either is great a sign!
Your starter has a pleasant yeasty smell to it, not super sour or pungent.
If all of these are present, then your starter should be all set to bake homemade bread!
If you are still a bit unsure, one test that I have used in the past is the float test. To do so, fill a drinking glass with lukewarm water and drop a spoonful of your sourdough starter in the cup. If your starter floats, it is ready to use! If it sinks to the bottom of the cup, then allow your starter more time to ferment.
How to Feed and Maintain Your Sourdough Starter:
You made it through the entire process of developing your own bubbly starter, but you're wondering, "Now what?"
Maintaining your sourdough starter to survive and thrive for years to come is quite simple. There are two main practices.