Why Is My Sourdough Starter Not Rising Troubleshooting Temperature And Flour Types

A sourdough starter is a living culture of wild yeast and lactic acid bacteria. When cared for properly, it becomes a powerful leavening agent capable of transforming simple flour and water into complex, airy loaves. But when your starter refuses to rise—no bubbles, no volume gain, no peak—it can be frustrating and confusing. The two most common culprits? Temperature and flour type. Understanding how these factors influence microbial activity is essential to diagnosing and fixing a sluggish or dormant starter.

The Science Behind Sourdough Fermentation

Sourdough starters rely on naturally occurring microorganisms—yeast and bacteria—that feed on the carbohydrates in flour. As they metabolize sugars, they produce carbon dioxide (CO₂) and organic acids. The CO₂ gets trapped in the gluten network, causing the starter to expand and rise. The acids contribute to flavor and preservation. This process is highly sensitive to environmental conditions and food source quality.

When fermentation slows or stops, it’s usually because one or more variables are out of balance. Yeast thrive between 70°F and 85°F (21°C–29°C). Outside this range, their metabolic rate drops significantly. Similarly, not all flours provide the same nutritional profile. Whole grain flours like rye or whole wheat contain more nutrients and minerals that microbes need, while refined white flours offer fewer resources unless supplemented.

Tip: Use lukewarm water (about 80°F/27°C) when feeding your starter to help stabilize temperature, especially in colder environments.

How Temperature Affects Starter Activity

Temperature is arguably the most influential factor in starter performance. Microbial activity increases with warmth and slows dramatically in cold environments. If your kitchen is below 68°F (20°C), expect slower fermentation. Below 60°F (15°C), many strains become nearly dormant.

In cooler homes, particularly during winter months, starters may take 12 hours or more to peak—or not rise at all. Conversely, temperatures above 90°F (32°C) can favor bacterial overgrowth, leading to excessive acidity that suppresses yeast. The ideal sweet spot for balanced growth is 75°F–80°F (24°C–27°C).

To test whether temperature is the issue, try moving your starter to a warmer location: near a radiator (not directly on it), atop the refrigerator, inside an oven with only the light on, or in a proofing box. Even a few degrees can make a dramatic difference.

“Temperature stability is more important than absolute warmth. Fluctuations stress the microbiome and delay consistent rising.” — Dr. Karl De Smedt, microbiologist and sourdough researcher at Puratos Center for Bread Flavor

Creating a Stable Warm Environment

If ambient room temperature is inconsistent, consider creating a controlled microclimate:

• Place the jar in a cooler with a mason jar of warm water (replaced every 6–8 hours).
• Use a seedling heat mat set to low (with a thermostat controller if possible).
• Store in a microwave or oven with the door closed but no heat applied—these spaces retain warmth well.

Monitor results over 2–3 feeding cycles. A healthy starter should double in size within 4–8 hours when fed and kept warm.

The Role of Flour Type in Starter Health

Flour isn’t just food—it shapes the entire microbial ecosystem. Different flours contain varying levels of starch, protein, enzymes, and micronutrients. These differences determine which microbes dominate and how vigorously they ferment.

Many beginners start with all-purpose white flour because it’s accessible. While usable, it lacks the bran and germ found in whole grains, which harbor more wild yeast and provide essential B vitamins and minerals that microbes need.

Best Flours for Reviving or Maintaining a Starter

Flour Type	Pros	Cons	Best For
Rye Flour (whole)	High enzyme activity, rich in nutrients, promotes rapid fermentation	Strong flavor, denser texture if used exclusively	Reviving sluggish starters, boosting activity
Whole Wheat Flour	Nutrient-dense, supports diverse microbes, widely available	Heavier rise, shorter shelf life after feeding	Daily feeding, building resilience
All-Purpose White Flour	Mild flavor, predictable behavior, good for consistency	Limited nutrition, may require more frequent feeding	Maintenance once active, baking
Bread Flour	Higher protein helps structure and gas retention	Still low in micronutrients compared to whole grains	Stable daily routines

For new or struggling starters, a blend of 50% whole rye or whole wheat with 50% all-purpose flour often yields the best results—providing both nutrition and manageability.

Tip: If switching flour types, do so gradually over 2–3 feedings to avoid shocking the culture.

Step-by-Step Guide to Revive a Non-Rising Starter

If your starter hasn’t risen in over 12 hours after feeding, follow this structured approach to diagnose and correct the issue:

1. Discard down to 20g: Remove all but 20 grams of your existing starter to reduce acidity buildup.
2. Feed 1:1:1 with whole grain flour: Add 20g whole rye or whole wheat flour and 20g lukewarm water. Mix thoroughly.
3. Place in a warm spot: Move to a location consistently between 75°F–80°F (24°C–27°C).
4. Wait 12 hours: Observe for bubbles, expansion, and aroma. It may not double yet, but signs of life are promising.
5. Feed again, transitioning back: Discard to 20g again, then feed with 20g all-purpose flour and 20g water.
6. Repeat every 12 hours for 2–3 days, keeping temperature stable.
7. Test float: Once the starter doubles within 6–8 hours, perform a float test—drop a small spoonful into a glass of water. If it floats, it’s ready to bake with.

This protocol resets the pH, replenishes nutrients, and reactivates dormant yeast. Patience is key—some starters take up to five days to fully recover, especially if previously neglected or refrigerated long-term.

Real Example: Bringing Back a Dormant Starter

Sophie had stored her starter in the fridge for three weeks while traveling. Upon returning, she fed it with all-purpose flour and left it on her countertop, which averaged 66°F (19°C). After two days, there was minimal bubbling and no rise.

Following advice from a local baker, she switched to twice-daily feedings using a 50/50 mix of rye and all-purpose flour. She placed the jar on a heating pad set to low, wrapped in a towel, maintaining about 78°F (26°C). By day two, small bubbles appeared. On day three, the starter doubled within seven hours. By day four, it passed the float test and successfully leavened a loaf of country bread.

Her experience underscores the combined impact of proper flour selection and temperature control—even a seemingly dead starter can rebound with targeted care.

Common Mistakes That Prevent Rising

Beyond temperature and flour, several habits sabotage starter development:

• Inconsistent feeding schedule: Irregular timing leads to erratic microbial populations.
• Using chlorinated tap water: Chlorine can inhibit microbial growth. Use filtered or bottled water if your tap is heavily treated.
• Over-discarding: Removing too much culture depletes the existing colony, delaying recovery.
• Sealing the jar tightly: While some airflow is fine, completely airtight containers can build pressure and limit gas exchange needed for healthy fermentation.
• Expecting immediate results: Especially with new starters, it can take 7–14 days of daily feeding before consistent rising occurs.

Tip: Label your jar with the time and date of each feeding. Tracking patterns helps identify what works—and what doesn’t.

Frequently Asked Questions

Can I use bleached flour for my starter?

Bleached flour is not recommended, especially in the early stages. The chemical processing can reduce nutrient availability and potentially harm developing microbes. Opt for unbleached all-purpose, whole wheat, or rye flour for better results.

My starter rises slightly but collapses quickly—is that normal?

A quick rise followed by collapse often indicates an imbalance—usually too much bacterial activity relative to yeast. Try feeding more frequently (every 12 hours instead of 24) and ensure you're using fresh flour. Also, verify that your environment isn't too warm, which favors bacteria over yeast.

How do I know if my starter has gone bad?

A healthy starter may develop hooch (a grayish liquid), have a strong sour smell, or show color variations depending on flour. However, discard immediately if you see pink, orange, or fuzzy mold. A rotten or putrid odor—not just sour—is also a red flag.

Troubleshooting Checklist

1. ✅ Is your kitchen below 70°F (21°C)? Consider warming the environment.
2. ✅ Are you using only refined white flour? Try introducing whole rye or whole wheat.
3. ✅ Have you fed the starter recently with fresh, unbleached flour?
4. ✅ Is the water free of chlorine or other disinfectants?
5. ✅ Has the starter been discarded and fed at least twice in the past 48 hours?
6. ✅ Are you observing it in a clear container with markings to track volume changes?
7. ✅ Have you waited at least 8–12 hours post-feeding to assess rise?

Run through this checklist whenever your starter underperforms. Most issues resolve within 2–3 days of corrective action.

Conclusion: Consistency Breeds Success

A sourdough starter is a partnership between baker and microbes. It demands regular attention, the right food, and a comfortable home. When it fails to rise, resist the urge to start over. More often than not, adjusting temperature and upgrading flour type will restore vitality.

Success lies not in perfection but in observation and response. Track changes, stay patient, and trust the process. With each feeding, you’re nurturing a unique culture shaped by your kitchen, ingredients, and rhythm.

💬 Have a revival story or a tip that saved your starter? Share your experience below—your insight could help another baker keep their sourdough dream alive.