My Sourdough Starter Isn’t Doubling In Size: What Can I Do?

Sourdough bread has gained immense popularity in recent years, with many enthusiasts cultivating their own starters at home. However, one of the most common challenges faced by beginners and even experienced bakers is a starter that doesn’t double in size, indicating weak fermentation activity. If you’re facing this issue, fret not. Let’s explore the reasons behind this problem and the solutions to get your starter back on track.

Your sourdough starter might not be doubling in size due to factors like insufficient feeding, suboptimal temperatures, poor flour quality, or the use of chlorinated water. Ensuring a warm environment, regular feeding, and using quality ingredients can enhance its activity and growth.

1. Optimal Temperature

Temperature is an instrumental factor in the behavior and vitality of a sourdough starter. At the core of this is the metabolism of the yeast and bacteria that constitute the starter. They have a particular temperature sweet spot, ranging from 78°F (25°C) to 82°F (28°C). When temperatures dive below this range, the metabolic activities of these microbes slow down, often leading to a starter that seems dormant or sluggish. In colder environments, you might notice a lack of bubbles, a thinner consistency, or even a decline in the starter’s volume.

Creating a conducive environment for your starter is pivotal. Consider relocating your starter to warmer locations in your household. Commonly overlooked spots include atop the refrigerator, which tends to be warmer due to the heat released from its coils. Alternatively, placing it inside an oven (ensuring it’s switched off) with just the light on can also provide gentle warmth. 

For those who seek more control over the environment, there are specialized tools available. Heating pads, when set on a low setting, offer a consistent warmth that’s ideal for a starter’s growth. Likewise, a proofing box can be a game-changer. These boxes allow for precise temperature settings, ensuring your starter always stays within its preferred range.

2. Feeding Frequency and Ratio

Just like any living organism, the microbes in a sourdough starter require sustenance. The balance and frequency of this sustenance can dictate the overall health and vitality of the starter. Feeding it sporadically or not providing ample food can starve the microbes, leading to a decrease in their activity. This might manifest as a reduction in the starter’s rise, a lack of bubbles, or a change in its aroma.

Especially in the formative days of a sourdough starter, regular and balanced feedings are crucial. This not only provides consistent nourishment but also aids in establishing a robust microbial community. 

A general guideline for beginners is to feed the starter once or twice daily. This feeding should ideally follow a 1:1:1 ratio, where equal parts of the starter, water, and flour are mixed together. As the starter ages and stabilizes, its feeding requirements might change. It might become more resilient, demanding less frequent feedings.

3. Flour Quality

Flour is the primary food source for the yeast and bacteria in your starter, but not all flours offer the same nutritional value. The inherent nutrients and minerals present in the flour can either support or stifle the growth of these beneficial microbes. Some flours, especially those that are bleached or heavily processed, may lack the essential nutrients required to nourish and maintain a lively sourdough starter.

Embracing whole grain flours can be transformative for your sourdough starter. Flours like whole wheat or rye are more nutritionally dense than their processed counterparts, and they often retain more of the bran and germ. These components are rich in minerals, vitamins, and other nutrients that can invigorate a starter. 

Transitioning from a bleached all-purpose flour to a whole grain variant can often lead to noticeable improvements in the starter’s activity, consistency, and aroma. Remember, just as a balanced diet benefits us, the right flour can significantly impact the health and vigor of your starter.

4. Water Quality

Water is an integral component of your sourdough starter. However, many municipal water sources contain chlorine or chloramine, added as disinfectants. These chemicals, while effective in ensuring potable tap water, can be detrimental to the yeast and bacteria cultures in the starter, potentially slowing their growth or even harming them.

When it comes to feeding your starter, the quality of water you use is as crucial as the flour. Opting for filtered or dechlorinated water can enhance the health of your starter. If you’re unsure about investing in a water filter, a simple hack is to leave tap water uncovered in a vessel overnight. 

This resting period allows most of the chlorine to evaporate naturally. Some water sources might have chloramine, which doesn’t evaporate as easily as chlorine; in such cases, using bottled spring water can be a beneficial alternative.

5. Starter Age

When embarking on the sourdough journey, one of the common challenges faced by bakers is managing expectations around the activity of a new starter. Young starters, especially those that are less than a week old, can often seem sluggish or even inactive. This can lead to doubts about the starter’s viability and potential success.

Time and patience are key when nurturing a young sourdough starter. The initial days of a starter’s life are marked by fluctuations in activity as different microbial populations establish themselves and find a balance. 

It’s not uncommon for a starter to take a week or even longer to show steady signs of fermentation, like consistent rising, bubble formation, and a pleasant tangy aroma. During this period, it’s essential to remain diligent, continuing with regular feedings and ensuring a conducive environment for growth. 

Over time, as the beneficial yeast and bacteria stabilize, the starter will display more predictable and vigorous activity. Remember, good things come to those who wait, and a well-nurtured sourdough starter is worth the patience.

6. Too Much Acidity

Over time and with infrequent feedings, the accumulation of acids, primarily lactic and acetic acid, from the fermentation process can become excessive in the sourdough starter. This heightened acidity can affect the pH balance of your starter, making the environment less hospitable for yeast and bacterial activity. An overly acidic starter might not only exhibit reduced activity but could also impart an overly sour or off taste to your bread.

Balancing the acidity of your starter is paramount for its overall health and for achieving desired bread flavors. If you find your starter becoming sluggish due to an acidic overload, it’s essential to intervene promptly. A thorough refreshment can rejuvenate your starter. 

By discarding all but a tablespoon of starter and introducing fresh flour and water, you’re diluting the accumulated acids and providing a more balanced environment for the microbes. Consistent feedings thereafter can further help in stabilizing the pH and restoring the starter’s vitality. It’s crucial to monitor its behavior and adjust feeding ratios or frequencies as needed to prevent another acidic buildup.

7. Contamination

A sourdough starter is a thriving microbial community consisting mainly of wild yeast and lactic acid bacteria. However, it’s also susceptible to invasion by undesirable microbes from the environment, which can outgrow and suppress the beneficial ones. Signs of contamination can range from off-putting odors to mold growth or an unusual change in color.

Maintaining hygiene is a proactive step to minimize the risk of contamination. Always ensure that the containers, utensils, and even your hands are clean when handling the starter. Should you notice signs that point towards contamination, it’s a judgment call on whether to discard and begin a new or attempt a rescue. 

Rescuing entails transferring a small amount of the starter to a fresh, clean container, discarding the rest, and beginning regular feedings with fresh flour and water. This process, much like the one for an overly acidic starter, aims to suppress unwanted microbes and allow the beneficial ones to regain dominance. If the signs of contamination persist despite these efforts, it’s safest to discard the batch and start fresh. Your health should always be a priority.


A sourdough starter is a living entity that requires care and attention. If your starter isn’t doubling in size, there’s usually a reason that can be addressed. By understanding the needs of your starter and making necessary adjustments, you can enjoy the rewarding experience of baking with a robust and active sourdough starter.


Hey there! I'm Sam, your go-to pal for all things sourdough. I've been baking and kneading for 10 fun-filled years, and I can't wait to share the joy of turning simple ingredients into heavenly sourdough bread with you. Grab your apron and let's dive into this amazing world of sourdough bread together on this blog.

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