Master Crumb

Beginner's Guide to Sourdough Starter

Creating a sourdough starter is easier than you think. With just flour, water, and patience, you can cultivate the wild yeast that will leaven your bread for years to come.

What is a Sourdough Starter?

A sourdough starter is a fermented mixture of flour and water that contains wild yeast and lactic acid bacteria. These microorganisms are naturally present in flour and the environment. When you create a starter, you're providing the ideal conditions for them to thrive.

Unlike commercial yeast, which is a single strain bred for fast, predictable rising, a sourdough starter contains a diverse community of microorganisms. This diversity is what gives sourdough its complex flavor, chewy texture, and better digestibility.

What You'll Need

  • Flour: All-purpose or bread flour works well. Whole wheat or rye can speed up the process.
  • Water: Filtered or bottled water is best. Chlorinated tap water can inhibit fermentation.
  • A jar: A glass jar (at least 500ml/1 pint) with a loose lid or cloth cover.
  • A kitchen scale: For consistent measurements.
  • A warm spot: Ideally 24-27°C (75-80°F).

Day-by-Day Instructions

Day 1: The Beginning

Combine 50g flour and 50g water in your jar. Mix until no dry flour remains. The consistency should be like thick pancake batter. Cover loosely and place in a warm spot.

Day 2: First Signs

You may see small bubbles forming—this is good! Discard half the mixture (about 50g) and add 50g flour and 50g water. Mix well, cover, and return to the warm spot.

Don't see bubbles? That's normal. The yeast population needs time to establish. Continue with the feeding schedule.

Days 3-4: Building Activity

Continue the daily feeding: discard half, add 50g flour and 50g water. You should start seeing more consistent bubble activity and a slightly tangy smell.

Days 5-7: Getting Stronger

Your starter should now be doubling in size within 4-8 hours after feeding. The smell should be pleasantly sour, like yogurt or overripe fruit.

If it's not doubling yet, keep feeding! Some starters take up to 14 days to become fully active, especially in cooler environments.

Day 7+: Ready to Bake

Once your starter reliably doubles within 4-6 hours after feeding and passes the float test (a small spoonful floats in water), it's ready to use!

The Float Test

To check if your starter is ready to bake:

  1. Fill a glass with room temperature water
  2. Drop a small spoonful of starter into the water
  3. If it floats, your starter is ready!
  4. If it sinks, feed it and try again in a few hours

Tips for Success

Temperature Matters

Yeast activity increases with warmth. If your kitchen is cool (below 20°C/68°F), try placing your starter:

  • On top of the refrigerator
  • Near (not on) a radiator
  • In the oven with just the light on
  • In a proofing box or warm water bath

Consistency is Key

Try to feed your starter at roughly the same time each day. Consistent feedings help establish a predictable rising pattern.

Don't Give Up Too Early

It's common for starters to be very active around days 2-3, then become sluggish for a few days. This is normal! The initial activity comes from different bacteria that eventually give way to the desired lactic acid bacteria.

Once It's Established

After your starter is active and reliable, you have options:

  • Room temperature: Feed once or twice daily if you bake frequently
  • Refrigerator: Feed once a week if you bake less often

Your starter will develop more complex flavors as it matures. Many bakers find their starters improve significantly after a few months of regular use.

Common Questions

Why do I have to discard?

Discarding keeps your starter manageable and ensures you're always feeding it fresh flour. Without discarding, you'd quickly have enormous amounts of starter, and the yeast would run out of food. Don't throw away the discard—use it for delicious recipes!

Can I use whole wheat or rye flour?

Yes! Whole grain flours contain more wild yeast and nutrients, which can help establish your starter faster. Many bakers use whole wheat or rye for the first few days, then switch to all-purpose for maintenance.

My starter smells like alcohol or acetone. Is it okay?

A boozy or nail-polish-remover smell indicates your starter is hungry and has consumed all its food. Feed it more frequently or with a higher ratio (try 1:2:2 instead of 1:1:1).

How do I know if my starter has gone bad?

A healthy starter can smell quite strong—tangy, yeasty, or even a bit funky. However, if you see fuzzy mold (usually pink, orange, or black), discard everything and start over. A thin layer of liquid on top (hooch) is normal and just means your starter is hungry.