Make Heavenly Leaven like your Local Baker

by Heather

Before starting on this journey, I had never even heard the term “leaven” before. Once I started baking sourdough, I learned that the term leaven is both a noun and a verb. This sent me on a quest for understanding leaveners, and I’m still figuring it out as I go, but here’s what I’ve learned so far.

Technically speaking, a leaven is basically whatever provides the rise in your baking. There are two primary types: chemical leaveners and natural leaveners.

Baking Soda or Baking Powder?

Chemical leaveners such as baking soda and baking powder are used prominently in baking. They work by released carbon dioxide gas into your dough or batter as a result of exposure to acid, liquid or heat, depending which leavener we’re talking about.

Natural leaveners include yeast, both wild and commercial. Commercial yeast changed the bread baking game when it was invented, but the taste was changed, and some flavor sacrificed. This is why, after thousands of years, we are still baking with wild yeasts.

When I use the word leaven, I’m most likely referring to the little concoction you will make from your starter that gets incorporated into your sourdough. Your leaven provides the rising power for your bread. Before you even start Day One of the sourdough process, you have to make sure your starter is healthy and active. If you’re not sure, try feeding it twice daily for several days and watch for activity: a predictable rise and fall, and visible gas bubbles. Clear mason jars are great for storing starters; just don’t tighten the lid all the way. Back it off a little bit to allow gases to escape, which will give room for the physical rise of the starter.

Take notes during this process if it’s new for you. Write down the date and time of feeding, how you fed, what it looked and smelled like before, and what happened after you fed it. This will help you notice a pattern (“Oh, my starter rises fully three hours after feeding”) which will deepen your knowledge of and connection with your starter.

Once your starter is healthy and active, bubbling away on the countertop, you can make your leaven. The leaven must be used in your bread dough, so you only need a leaven if you’re planning to bake. It’s like the middleman between your starter and your sourdough. You’re now ready to begin Day One – Leaven Day.

Follow the steps below to ensure you make leaven like a professional baker. Let me know what you think in the comments below, including if you made it and if you changed anything. I would love to hear your feedback!

Heavenly Leaven

Use your healthy, active starter to build your leaven the night before you plan to prepare your dough. I call this Day 1 of the Sourdough Process – Leaven Day!
5 from 1 vote
Prep Time 10 mins
Fermentation Time 1 d
Total Time 1 d 10 mins


  • 100 grams Lukewarm Water
  • 50 grams Healthy, Active Starter
  • 50 grams Whole Wheat Flour
  • 50 grams White Flour all-purpose or bread flour


  • On Leaven Day (the day before you plan to make your dough), feed your starter first thing in the morning and leave it on the counter. In the evening, you will make your leaven.
  • In a larger-than-normal mason jar, pour in water. Add starter, close lid tightly and shake to incorporate.
  • Open the jar and add both flours. Using a bread knife, stir it all together until it’s sticky and there is no dry flour remaining. (Look through the bottom of the jar to make sure there’s none hiding!)
  • Leave on the counter overnight – it should take 8 to 12 hours to ferment appropriately. It will have doubled or tripled in size, and will be light and bubbly with a sweetly sour smell.
  • To test readiness, take a glass of warm water and drop a small amount of your leaven in it. If it floats, it’s ready for baking. If it sinks, it needs more time to ferment. Recheck every 30 minutes or so.
  • When it passes the float test, you may begin mixing your sourdough!
Keyword Leaven, Sourdough

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Carol May 24, 2019 - 7:56 pm

5 stars
Great advice!

Karen September 10, 2020 - 3:18 pm

What size mason jar is considered “larger than normal?” Is a 1qt jar large enough?

leavenly September 15, 2020 - 9:18 am

I use a 32 oz jar, which is a quart, so yes! That’s perfect!

Sher September 17, 2020 - 2:55 am

My leaven deflated after 10 hours 🙁
Can I remove 50g and add 100g flour+100g water to activate it again?

leavenly October 24, 2020 - 9:06 pm

Hi Sher, that’s actually quite common and may not even be an issue! Did you try the float test with your leaven? Mine tends to start deflating around 8-9 hours but still passes the float test and makes exceptional bread. Give the float test a try, and if it sinks, then yes – it needs a little boost. I would simply add 2 tbsp whole wheat flour and 1 tbsp water, stir it into the leaven, and recheck in half an hour. If it still sinks, keep checking every 30 minutes until it floats! 🙂


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