This post outlines how to build a sourdough starter from scratch simply and quickly. In less than a week, with minimal effort, you will have a bubbly, active starter on your hands to use in all your favorite sourdough recipes.

A Weck jar holding sourdough starter doubled in volume.

A sourdough starter is a fermented mixture of flour and water that contains wild yeast and bacteria. It both leavens and flavors sourdough bread.

How? It’s time for a science lesson. 

Wild yeasts and bacteria exist everywhere, namely in flour, but also in the air and on your hands. When we mix flour and water and let it sit, wild yeasts begin searching for food, which they find in the flour: they convert the starch in the flour into sugar. As they digest this sugar, they produce two things: carbon dioxide, which makes the starter rise, and alcohol, which the wild bacteria drink up and in turn produce various types of lactic and acetic acids — these acids are what give the bread the sour flavor.

Cool, right? The wild yeasts and bacteria work symbiotically to both leaven and flavor our starter and ultimately our bread. 

3 Tips For Success

Because wild yeast and bacteria are the backbone of a sourdough starter, it is crucial that these microbes are happy for your starter to thrive: the happier they are, the more they multiply, the more powerful the starter you create.

Building up a colony of happy microbes takes time and care. Here are three tips for success:

Tip #1: Use Good Flour: Use freshly milled, stone-milled flour because the added minerals and nutrients provide better food for the microbes (yeast and bacteria) to thrive. If you have a local source, use it! Health food markets, co-ops, and stores like Whole Foods often carry freshly milled flour. See recipe box for a few online sources I love. Stone-Milled Flour = Rocket Fuel For Your Starter

Tip #2: Keep Your Starter Cozy: Ideally, you’ll attempt this project while it’s hot outside — I find 80ºF (26ºC) to be ideal. If you’re building your starter when it’s cold outside, find a place to keep it warm. See recipe box for some ideas. Invest in a reasonably priced ambient temperature thermometer to help you monitor the various warm environments you create:

Two jars of sourdough starter keeping cozy in a turned-off oven.

Tip #3: Use Pineapple Juice: Using pineapple juice in place of water initially can shorten the overall timeline for building a sourdough starter from scratch. This is because wild yeast cells prefer a somewhat acidic pH (which pineapple juice is) in which to grow.

How to Build a Sourdough Starter From Scratch, Step by Step

Day 1: Gather your materials: flour and pineapple juice or water.

A bag of Cairnspring Mills flour and a small jar of pineapple juice.

Pour the can of juice into a large bowl or ideally a straight-sided vessel on a tared scale.

A 2-quart container on a scale holding pineapple juice.

Add an equal amount of flour by weight. It should be about 192-193 grams of juice and flour each.

A 2-quart container holding pineapple juice and flour.

Stir the flour and juice together until the flour is absorbed.

A 2-quart container holding just-mixed flour and pineapple juice.

Cover the vessel. Record the date, time, and measurements — you will forget which day you started if you don’t. Let it sit at room temperature for 24 hours.

A covered 2-quart container with a post-it note on top.

Day 2: Uncover the vessel and…

A 2-quart container holding sourdough starter.

… give it a stir.

A two-quart container holding just-stirred sourdough starter aside a large spoon.

Re-cover the vessel, and record your work. Let it sit at room temperature for another 24 hours.

A covered 2-quart container with a post-it note on top.

Day 3: Uncover the vessel.

A 2-quart container holding sourdough starter.

Measure out 128 grams (about 1 cup) of flour and 128 grams (about 1/2 cup) of water:

A two-quart container holding sourdough starter aside a bowl of flour and water.

Add them to the vessel.

A two-quart container holding sourdough starter, flour and water not mixed together.

Stir to combine.

A 2-quart container holding sourdough starter.

Cover the vessel and record your work again. Let it sit at room temperature for 24 hours, stirring once or twice.

A two-quart container holding sourdough starter, covered with a post-it note on top.

Day 4: Uncover the vessel. You should see a little action (bubbles). Measure out 128 grams (about 1 cup) of flour and 128 grams (about 1/2 cup) of water:

A 2-quart container holding sourdough starter.

Add them to the container.

A 2-quart container holding sourdough starter, flour, water, and a spoon.

Stir to combine.

A 2-quart container holding sourdough starter, just mixed.

On this day, record your work again, and mark the height of your mixture with tape on the side of your vessel. Let it sit at room temperature for 24 hours, keeping a closer watch this time around.

A 2-quart container holding sourdough starter with its height marked by a piece of washi tape.

You will likely see some action…

A two-quart container holding sourdough starter increased in volume by 25%.

The mixture might even double in volume.

A 2-quart container holding sourdough starter doubled in volume.

And you should see lots of bubbles on the surface.

A 2-quart container filled with bubbly sourdough starter.

If your mixture is in fact rising, let it rise until it nearly doubles in volume; then drop a spoonful of it in water. If it floats, you’re in business. Note: Your starter might rise (and maybe fall) while you are sleeping — don’t worry if you don’t “catch” it at its peak. Continue on with the process that follows.

A spoonful of sourdough starter floating in a glass of water.

Spoon 128 grams of the starter into a new vessel.

A Weck jar on a scale holding sourdough starter.

Measure another 128 grams of flour and water each.

A Weck jar on a scale holding sourdough starter.

Add the flour and water to the starter.

A Weck jar on a scale holding sourdough starter, flour, and water.

Stir to combine.

A Weck jar will with just-fed sourdough starter.

Mark the height with a rubber band.

A Weck jar will with just-fed sourdough starter.

This original vat of sourdough starter is now your discard bucket. Transfer it to the fridge or use it in one of your favorite sourdough discard recipes: tortillas, crackers, pancakes, soda bread.

A 2-quart container filled with bubbly sourdough starter.

Day 5: When your starter doubles…

A Weck jar filled with sourdough starter doubled in volume.
A Weck jar filled with sourdough starter.

… and floats…

A spoonful of sourdough starter floating in a glass of water.

…you can do one of three things:

  1. Repeat this process: spoon 128 grams of starter into a new vessel and add 128 grams each flour and water. (Transfer the remaining starter to your bucket of discard.) Let the new starter rise until it doubles. Your starter will get stronger with every feeding.
  2. Transfer it to the fridge if you need to take a break from the process. You can pick up where you let off when you are ready.
  3. Test it out…

… in a sourdough bread recipe. I recommend starting with…

A jar of sourdough starter aside a vat of sourdough dough rising.

… focaccia, one of the easiest breads to make.

Sourdough focaccia.
Halved sourdough focaccia.
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A Weck jar holding sourdough starter doubled in volume.

How to Build a Sourdough Starter from Scratch

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Description

This post outlines how to build a sourdough starter from scratch simply and quickly. In less than a week, with minimal effort, you will have a bubbly, active starter on your hands to use in all your favorite sourdough recipes.

Notes:

Adapted from Peter Reinhart’s method, outlined in Perfect Pan Pizza (and many of his other books as well). 

If you are looking for guidance on how to feed, maintain, and store your already strong starter, see this post: How to Feed, Maintain, and Store a Sourdough Starter.

5 Tips for Success

  1. Use a scale to measure. It is the only way to measure accurately.
  2. Use a straight-sided vessel, which will help you more accurately see how much your starter is growing.
  3. Attempt this project while it’s hot outside or create a cozy place for your starter to rise: Ideally, the cozy place you create will be between 70ºF (21ºC) and 80ºF (26ºC).
    • Find a warm place in your kitchen (like on top of your refrigerator) to let it rest.
    • Invest in the Brod and Taylor Sourdough Home: I do not own this, but it gets good reviews, should you have the space for it
    • Build your own “sourdough home“: one of you ingeniously made a homemade proofing box by placing a seed heating pad in a box and covering it with a towel.
    • Try the warm oven trick: turn your oven on for 1 minute (at any temperature) and then turn it off. Consider sticking a post-it note to the oven to remind you that you have a starter in there so that you don’t accidentally preheat your oven and kill your starter.
    • Another idea: Turn the oven light on for 10 to 15 minutes, then shut it off. I caution against keeping the oven light on the entire time because it potentially will create a too-warm space (especially in a newer oven) that might kill your starter. A great tool to invest in is an ​ambient temperature thermometer​, as it will help you accurately gauge the temperature of the cozy spaces you create to help your starter thrive
  4. Use freshly milled stone-milled flour. If you have a source local to you, use it! Health food markets, co-ops, or markets such as Whole Foods often carry freshly milled flour. Here are a few mail-order options: 
  5. Water: If your water is RO or if you have concerns about your water, you can: 
    • Use water that you’ve left out overnight to ensure any chlorine has evaporated.
    • Buy spring water. In some places, letting water sit out overnight will not be effective, and your tap water may kill your starter.

Discard: At the end of the first four days of the process, you’ll be left with a decent amount of sourdough discard, which you can use in countless recipes. Here is my collection of Sourdough Discard Recipes. 

Ingredients

  • 192 grams (about 1 1/2 cups) stone-milled flour, see notes above
  • 192 grams (about 3/4 cups) water or pineapple juice, see notes above

Instructions

  1. Day 1: Ideally, you are using a straight-sided vessel for this project; otherwise, a large bowl is fine. (Note: A straight-sided vessel allows you to truly see how much your starter is growing. I’m using this Cambro.) Stir together the flour and water (or juice) until the flour is absorbed. Cover the vessel. Record the date, time, and measurements — you will forget which day you started if you don’t. Let it sit in a cozy environment — 75ºF to 80ºF is ideal (see ideas above) — for 24 hours. If you remember, stir the starter once or twice over these 24 hours. 
  2. Day 2: Uncover the vessel. Stir the mixture. Re-cover the vessel, and record your work. Let it sit in a cozy environment for another 24 hours. If you remember, stir the starter once or twice over these 24 hours. 
  3. Day 3: Uncover the vessel. Add 128 grams (1 cup) of flour and 128 grams (about 1/2 cup) of water. Stir to combine. Cover the vessel, mark the height of your mixture with tape, and record your work again. Place it in a cozy spot. If possible, monitor your starter over the next 8 to 10 hours and if…
    • …your starter doubles or begins to double, feed it with 128 grams each flour and water. If it doubles again before it’s time for you to go to bed, skip to Day 5 and proceed with making the offshoot. If it doesn’t, let it in a cozy environment overnight. Then proceed with making the offshoot (step 5) in the morning. 
    • … you are not seeing much action, continue to let it sit in a cozy environment till the following day, stirring it once or twice. Proceed with Day 4 in the morning. 
  4. Day 4: Uncover the vessel. You should see some action (bubbles), and your starter should smell pleasant, not unlike a fruity yogurt. Stir it, then feed it with 128 grams each flour and water. Stir to combine. Cover the vessel, mark the height of your mixture with tape, and record your work again. Place it in a cozy spot. If possible, monitor your starter over the next 8 to 10 hours and if…
    • …your starter doubles or begins to double, drop a spoonful of it in water. If it floats, you’re in business. Skip to Day 5 and proceed with making the offshoot.
    • … your starter is not quite doubling, continue to let it sit in a cozy environment till the following day, stirring it once or twice. Proceed with Day 5 in the morning. 
  5. Day 5: At this point, you should be observing some activity in your starter, meaning the starter should have risen slightly (perhaps doubled but perhaps not) and fallen with bubbles transforming from big to small. You’ll now take a small portion of this mixture and build a new starter: Transfer 100 grams of the starter to a new jar or vessel, and add 100 grams of flour and 100 grams of water. Stir well to combine, then cover the jar. Mark the height with a rubber band. Let it sit in a cozy spot. Transfer the remaining starter to the fridge — this original mixture is now your sourdough discard and can be used in all sorts of recipes, see notes above. When your new starter doubles in volume, you can do one of three things: 
    • Repeat this process: spoon 100 grams of starter into a new vessel and add 100 grams each of flour and water. (Transfer the remaining starter to your bucket of discard.) Let the new starter rise in a cozy spot until it doubles. Your starter will get stronger with every feeding.
    • Transfer it to the fridge if you need to take a break from the process. You can pick up where you left off when you are ready.
    • Test it out in a sourdough bread recipe. 
  6. Maintaining your starter: Once you have a strong, active starter on your hands, follow the steps in this post: How to Feed, Store, and Maintain a Sourdough Starter.
  • Category: Bread
  • Method: Stir
  • Cuisine: American