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  • Writer's pictureMatt Suprunowicz

Sourdough I: How to Make and Maintain a Starter

Updated: Jul 28, 2023

How can we begin the bread making process at home?


This Lesson Plan is part the Nutrition Module of SustainEd Farms' virtual programming.

Background: Making a Sourdough Starter

Making a sourdough starter enables the home baker to continually source the foundation for a delicious bread for years to come. While the process itself requires some precise measurements and proper timing (including at least a week of careful observations), the mechanics of making a starter are extremely simple: mixing flour and water, and waiting. If you tend to your live culture properly -- feeding it when it needs and slowing the feeding process when you do not need the dough -- you’ll be able to make a fresh loaf of sourdough bread anytime you’d like. In times of potential food scarcity, having a reliable source of bread will surely be a delight!

Learning Objectives

Students will be able to...

  • Make and maintain a sourdough starter

  • Understand the basic scientific processes underlying the creation of a live starter

Academic Vocabulary

yeast /yēst/ noun. - a type of fungus that can be found in the air which facilitates the fermentation process of certain sugars

ferment /fərˈment/ verb. - the chemical breakdown of certain carbohydrates, producing heat and byproducts like alcohol

leaven /ˈlevən/ verb/noun. - the entity (or process itself) that facilitates the rising of bread


1. Gather your materials. You will need the following supplies:

A kitchen scale (not necessary, but highly recommended) · a glass jar (pint or larger) · a fork · a tea towel or cloth · flour (whole wheat, rye, spelt, komut) · water · measuring cups · additional flour and water, for feeding

2. Watch this Youtube video to see a demonstration of how to make a sourdough starter. Then, follow along with the remainder of the lesson by reading the steps below.

3. Using the kitchen scale, measure out equal quantities -- by mass -- of flour and water into separate measuring cups. This lesson will use 50 grams of water and 50 grams of flour. To do this, set a measuring cup on your scale and tare the scale (i.e. “zeroing” the scale so the scale reads “0 g” with the measuring cup on it). Then, using a spoon, slowly transfer water or flour into your measuring cup until the scale reads 50 grams. Repeat the process for the other ingredient, being careful not to spill any water or flour on the scale (which would make the reading on the scale higher than what you actually have in your measuring cup). If you are not using a scale, measure out ¼ cup of water and ⅓ cup of flour.

4. After you have the proper quantities of flour and water weighed out, pour both ingredients into your glass jar, and mix the ingredients together using a fork. Mix until the batter is thoroughly combined and it begins to give off a mild “doughy” fragrance -- it will resemble a thick paste.

5. Place your towel or cloth loosely on top of your jar, and set in a warm spot in your house for 24 hours -- preferably in a location that sits at 75-80 °F.

Sourdough Starter dough mix

sourdough starter dough mix covered by cloth

Wait and observe… You will want to watch your flour/water mixture for signs that wild yeast has arrived:

  • First of all, what is “wild yeast?” Where did it come from? What does it do? Why is it important?

    • Wild yeast is the fungus that causes the fermentation of the flour and water mixture.

    • Wild yeast is everywhere! The spores of the yeast are in the air, on your hands, and in the flour itself. With the right conditions (warmth and addition of water to the flour -- its food), the yeast is able to proliferate and multiply.

    • The yeast feeds on the flour and water mixture, producing alcohol (which is absorbed by a symbiotic bacteria and evaporated off during the baking process) and carbon dioxide (the byproduct of cellular respiration).

    • The carbon dioxide produced by the yeast culture leavens the bread (i.e. makes it rise), giving the bread the wonderful “airy” texture that humans enjoy.

  • What are the “good signs” I should look for?

    • Bubbles indicate that cellular respiration is occurring (carbon dioxide is getting released into the atmosphere), which means that your wild yeast has found its way to your flour mixture.

    • A good smell should accompany your starter -- something light, doughy, yeasty, or slightly sour smelling.

  • What are the “bad signs” I should look for?

    • The buildup of a brown liquid known as “hooch” may make its way into your starter. This is alright -- just pour off the odd-smelling liquid, and feed your starter (directions below) since this is a sign that your live culture needs to be fed.

    • If you encounter a bad smell -- something that resembles rubbing alcohol -- this may be an indication that something went wrong during your starter process. You may have to start over, which is totally fine (and easy)!

6. If bubbles have arrived by your second day, it is time to begin “feeding” your yeast culture. It is entirely possible that bubbles arrived, and then disappeared already. If you think this is the case, you can begin feeding your sourdough culture anyways (especially if the mixture has already grown in size). You can also wait another 24 hours to begin feeding -- make the choice you believe to be best from your observations.

📅General Feeding and Discarding Guidelines & Schedule Follow these steps to feed your yeast properly! Try to check back and feed the culture at the same time each day.

  1. On day 2 (or day 3), weigh out 50 grams of water and 50 grams of flour. Add these to your starter, and mix thoroughly. Continue to make observations, and leave your jar covered in a warm spot as before.

  2. On day 3 (or day 4), discard half of your starter (see last step for what to do with “discarded” dough). Then, feed your starter as described in step one. Watch for the rising and falling of your starter. The falling indicates that your starter is ready to be fed again, generally on the next day.

  3. On day 4 (or day 5), your starter should be visibly larger at this point, producing bubbles, and perhaps smelling more musty. You may consider moving your starter to a larger jar in order to let it grow more. You should discard about half of the starter once again, and use the same measurements (50 g water, 50 g flour) as before to feed it.

  4. Continue this discard/feeding schedule for at least a few more days, and continue to cover it and place it in a warm area. Your starter will become thicker and sticky, but should still smell pleasant.

  5. After about a week -- day 6 or 7 at the earliest, probably -- if your starter has grown, and displays all of the signs of being “good” (a strong, sour, pungent smell with lots of bubbles and a webbed texture) then you may attempt the “float test.”

  6. To perform the float test, drop a small portion (a teaspoon) of starter into a bowl of water. If the starter floats to the surface, your starter is ready to use. If it does not float, continue to feed the culture and make observations on its appearance. It may take several more days for your culture to become ready depending on the conditions you’ve created for its growth.

7. Once you’ve dubbed your starter ready, you can do one of many things:

  • The obvious choice is to use your entire sourdough starter to make your own loaf (or loaves) of sourdough → another lesson in itself!

  • If you don’t want to use your entire starter, and would rather keep it alive for bread baking to come, you have many options:

    • Continue feeding the sourdough as described above, and use the “discarded” portions to make loaves of bread.

    • Slow the rate of feeding by cutting your feeding and discarding portions in half.

    • Reduce the amount of starter you have by slowing your feeding schedule (cut your feeding portions in half) while maintaining your discarded portion until you have the amount of starter you desire.

    • Slow the growth of your starter by storing it in the fridge. To do this, feed and discard the starter as before, let the mixture stand at room temperature for a few hours, and then seal your jar with a lid before placing it into the refrigerator. Maintain the low growth starter by discarding some and feeding it (as before) once a week, letting it stand at room temperature, and then putting it back into the fridge.

Additional Resources:

Download the PDF version of this lesson plan:

Sourdough I_ How to Make and Maintain a Starter
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