Sourdough starter not rising? It is probably not dead.

A starter that sits flat for a day or two is almost always hungry, cold, too wet, or too acidic. Fix those four things and life usually comes back within a few days.

By Morgan Reid, author of Sourdough Starter Rescue

What a stalled starter looks like

It stays flat for 24 to 48 hours after feeding. You might see a few tiny bubbles on top, but there's no dome and no doubling, and the texture looks pasty or watery. It may smell faintly sour, oddly sweet, or a little like apples or glue.

Check one thing first. Fuzzy growth, or pink or orange streaks, isn't a "won't rise" problem. That's contamination: discard and restart. Gray liquid on top (hooch) or a dry skin is fine, and simply means the starter is hungry.

The four usual causes

• Too cold. Below about 70°F (21°C), yeast work so slowly that bubbles escape before they add any height.
• Too hungry. Long gaps between feeds let acid build up while food runs out, and the yeast slow down.
• Too acidic. A sharp vinegar or pickle smell that stings your nose means the yeast are stressed in a low-pH bath.
• Too wet. A very thin starter behaves like soup: gas shoots to the top and pops instead of lifting the mix.

The fix, step by step

1. Warm it up. Find a steady 75 to 80°F spot: an oven with just the light on, the top of the fridge, or a proofing box set low. Don't go above about 85°F (29°C), and take the jar out before you preheat the oven. This step alone often changes everything.
2. Feed 1:2:2. Keep 20 g starter and add 40 g water and 40 g flour. If it smells very sour, do one 1:3:3 feed instead (60 g water, 60 g flour). Use 25 to 50% whole wheat or rye for the next 2 or 3 feeds.
3. Thicken it to trap gas. Aim for thick pancake batter: a ribbon off the spoon should sit on the surface for 2 or 3 seconds. If it pours like milk, stir in flour a teaspoon at a time.
4. Mark it and watch. Put a rubber band at the level and check at 2, 4, 8 and 12 hours. The highest point before the dome relaxes is the peak, and that's your next feeding time.
5. Repeat every 12 hours. Don't wait days. Steady food rebuilds yeast numbers. For an optional boost, use slightly warm water once, or do a single feed with 100% rye, then go back to your usual flour.

What success looks like

Within 24 to 72 hours you should see a gentle dome, bubbles threaded through the middle (not just froth on top), and a 50 to 100% rise between feeds. The smell shifts from flat to cleanly tangy, like yogurt or green apple. In a warm room, many starters double in 6 to 8 hours by day 3 or 4.

Judge by rise, smell and texture together. The float test is easily thrown off by how wet the starter is and how much you stirred it.

If it's still flat after three days

• Do a one-time 1:5:5 feed (20 g starter, 100 g water, 100 g flour) somewhere warm to dilute excess acid, then go back to 1:2:2 twice a day.
• Check the temperature at jar height with a thermometer. Countertops are often cooler than you think.
• Rule out chlorine: let tap water sit out overnight, or use filtered water for a few days.
• Make sure it isn't too thin. Thick pancake batter is your friend.

Sourdough Starter Rescue

The full guide: a 7-day plan to revive a dead or failing starter, plus a fix for every symptom, from hooch and mold to a starter that won't rise.

Read it on Amazon →

How long does it take a sluggish starter to rise again?

With warm, steady 12-hour feeds, most starters show a dome and a 50 to 100% rise within 24 to 72 hours.

What temperature does a sourdough starter need?

A steady 75 to 80 degrees F (24 to 27 C). Below about 70 F yeast slow down sharply; avoid going above about 85 F.