Sourdough Starter Basics

What is a sourdough starter?

A starter is a flour and water culture in which wild yeast and lactic acid bacteria grow together. The yeast makes gas that raises dough, and the bacteria make acid that gives the bread its tang. Each home culture is a bit different because it depends on the flour, the water and the kitchen.

You can make one from scratch or receive a portion from a friend. Either way, the care is the same, and a healthy culture can last for years.

Plan a small space for the jar. A clear container lets you see bubbles and rise, and a loose cover keeps out dust and insects while letting gas escape.

How do I make one from scratch?

Mix flour and water in a clean jar, cover loosely so gas can escape, and keep it at a comfortable room temperature. Each day, discard a portion and feed the rest with fresh flour and water. Over days the mixture begins to bubble and develop a pleasant sour smell.

Timing varies a lot with temperature and flour. Whole grain flour tends to start faster than white. Follow a published guide from a baking school or extension source for ratios, and be patient if the first week looks quiet.

• Use a clean jar and a loose cover
• Discard and feed on a steady schedule
• Keep it away from drafts and direct heat
• Judge by activity, not by the calendar

What do the smells and bubbles mean?

Early on, strange smells are common, including sharp, fruity or cheesy notes, as different microbes compete. These usually settle as the culture matures. A clear or grayish liquid on top is often called hooch and indicates the starter is hungry. Many bakers stir it in or pour it off before feeding.

A mature starter doubles or more after feeding, smells sour and yeasty, and has a bubbly, airy texture. Use that rise as your readiness test rather than the age of the jar.

Warm kitchens speed activity, while cool ones slow it. If your starter seems stuck, move it to a slightly warmer place before assuming something is wrong.

When is a starter spoiled?

Fuzzy mold, pink or orange streaks, or a truly rotten smell mean the starter should be thrown out. Do not scrape the mold off and keep using the rest. Wash the jar thoroughly and start again.

Hooch, a sour smell and a flat or sluggish culture are not spoilage. They are signs the starter needs feeding or a warmer spot.

Some bakers keep a very small amount of starter and feed it in a fresh jar each time, which keeps the culture clean and cuts down on flour use. Others keep a larger amount for frequent baking.

How do I keep a starter between bakes?

If you bake often, keep it on the counter and feed on a regular schedule. If you bake only now and then, store it in the refrigerator and feed it periodically. Take it out, let it warm up and feed it a couple of times before baking so it is active again.

Share extra discard with neighbors or use it in pancakes, crackers and flatbreads rather than throwing it away. Keep a spare jar of starter in case one batch is lost.

If you need to leave for a few weeks, ask a baking instructor or reliable guide about long-term storage methods. Many bakers keep a backup portion for exactly that reason.

Does flour or water type matter?

Flour matters more than most beginners expect. Whole grain flours feed the culture quickly, while white flour makes a milder starter. Unbleached flour is often recommended because additives can slow growth.

Chlorinated tap water can slow a young culture in some homes. If your starter is sluggish, let water stand for a while or use filtered water, and check with your water utility or extension office about your supply.

What can I do with the discard?

Discard works well in pancakes, waffles, crackers and flatbreads. It adds tang and uses flour that would otherwise be thrown away.

Keep discard in a covered jar in the refrigerator and use it within a short period. If it smells rotten or shows mold, throw it out.

Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.