Why a Sourdough Starter Rises and Falls
You feed your starter, watch it climb up the jar, then come back to find it has sunk. Or you feed it before bed and wake up wondering whether anything happened at all.
With an established sourdough starter, rising and falling is a normal part of fermentation. It rises as gas builds up inside the mixture. It falls when that expanded mixture can no longer maintain its height and gas escapes. Falling alone doesn’t mean the starter has died.
Understanding this cycle makes the jar much less mysterious. It also helps you spot when your starter has been busy while you weren’t watching.
What makes a starter rise?
A starter contains a living community of yeast and bacteria. After feeding, the microorganisms use sugars available from the flour. Yeast produces carbon dioxide during fermentation, and some bacteria contribute gas too.
That gas forms bubbles. When the mixture holds those bubbles, it expands and rises up the jar. In a wheat starter, the flour’s gluten helps it retain gas.
There are two things happening together: gas is being produced, and some of that gas is being held in the mixture. The height you see depends on both.
This is why changing flour or adding more water can change the appearance of your starter. A mixture that releases gas easily may bubble away without climbing as high as a thicker one.
Why does it eventually fall?
Fermentation keeps changing the mixture after the first bubbles appear. Sugars are used, acidity develops, and the starter’s structure changes. Over an extended fermentation, a wheat starter can become less able to hold the gas inside it.
As gas escapes and the expanded structure settles, the level drops. The starter may leave a mark around the jar showing where it reached its highest point.
People often describe this as the starter “running out of food”. That is a useful shorthand for a starter left too long between feeds, but a falling surface doesn’t tell you that every bit of food has disappeared or fermentation has stopped. Gas production and gas retention both affect the result.
The yeast hasn’t simply vanished because the starter is lower in the jar.
Follow one feeding cycle
You don’t need to catch every tiny change. These are the main stages to notice:
| Stage | What you might see | What it tells you |
|---|---|---|
| Just fed | A freshly mixed starter at its marked starting level | This is your reference point for the feed. |
| Rising | More bubbles and an increasing volume; the top may be rounded | Gas is building up and being retained. |
| At its peak | The highest level for that feeding cycle; the rounded top may flatten | The starter has reached its maximum visible rise. |
| Beginning to fall | A slight settling at the surface | For our baking method, this is still part of the ideal window. |
| Well past its peak | A lower level, often with residue higher on the glass | The starter has already risen and fallen; feed again before baking. |
This describes a typical established wheat starter. Different flours and gluten-free blends can give a less obvious rise and fall.
For the full baking-readiness checklist, see how to tell when your sourdough starter is ready.
“I fed it last night and nothing happened”
This is something we hear from customers. They feed the starter, put it away or go to bed, then check it many hours later. By then, it may have completed its rise and fallen back close to its starting level.
Before assuming it hasn’t worked, look above the current level for a high tide mark. A band of dried starter or bubbles higher up the glass can show where it has been. A clean jar makes this easier to distinguish from smears left during mixing.
The aroma can help too. With our wheat starter, a pleasantly yeasty smell becomes more sour as it moves further past its peak. Strong alcohol or acetone-like smells are signs we associate with a very hungry starter, not simply one that has just started to settle.
Smell gives you another clue, rather than an exact timestamp. Read it alongside the marks on the jar and what you know about the feed.
Try a daytime feed
One observed feeding cycle can explain more than several overnight guesses.
- Use your usual measured feeding quantities and a clean jar.
- Mark the starting level with a rubber band or your jar’s silicone band.
- Note the feeding time and the temperature near the jar.
- Check every couple of hours, and more often when it is rising quickly or nearing its peak.
- Take a quick photo at each check so you can compare the levels.
A starter-care jar with a level marker and a thermometer makes this convenient, but an ordinary clear jar, rubber band and digital scales are enough to get started.
Keep the flour and feeding quantities consistent while you observe. That makes it easier to recognise the effect of temperature instead of changing several things at once.
Why does the cycle change from one feed to the next?
Temperature: Within a suitable range, warmer conditions generally speed fermentation and cooler conditions slow it down. We suggest around 24–27°C for observing activity. Avoid direct sun and uncontrolled heat. A warmer day can mean the starter peaks before your usual checking time.
The size of the feed: Keeping 50 g starter and adding more fresh flour and water changes the feeding ratio. A larger feed relative to the retained starter will often take longer to reach its peak under otherwise similar conditions. It is not a guaranteed number of extra hours.
Flour and consistency: Different flours absorb water and hold gas differently. A slack mixture may release bubbles readily, while a thicker one may hold them longer. Keep using the feeding ratio recommended for your particular starter and flour.
You don’t need to memorise a timetable. Take note of the conditions and learn what your starter does in your kitchen.
What should I do if it has already fallen?
If it is at its peak or only just beginning to fall, that is our preferred baking window.
If it has fallen substantially, give it another feed before baking. It may still ferment dough, but the dough can take much longer, which makes a beginner bake harder to judge.
For an established wheat starter, take 50 g starter into a clean jar and feed with 50 g bakers flour and 50 g water, weighed with digital scales. Mark the level, keep it comfortably warm and watch it rise again. Use the specific feeding quantities for rye, spelt or gluten-free starters.
Our starter-readiness guide includes the flour-specific ratios and examples for preparing a larger amount while keeping a small starter.
What about gluten-free starters?
Gluten-free starters ferment too, but their structure behaves differently. Our Organic Gluten-Free Starter fed with brown rice flour shows much subtler signs: very small bubbles, a layered appearance and a pleasantly yeasty, slightly sweet aroma. Don’t expect the same dramatic rise as a wheat starter.
With our recommended gluten-free flours, the rise is more noticeable. Our Easy Rise Gluten-Free Starter also shows visible bubbles and a noticeable rise once activated and fermenting. Doubling is not a universal requirement.
The practical lesson is the same: learn the response of your starter to its feed. Our readiness guide covers the differences between the two gluten-free starters and includes the brown rice starter video.
Quick questions
Has my starter died because it collapsed?
Falling alone doesn’t mean it has died. It usually shows that the expanded mixture has passed its peak and settled. Check its feeding history and conditions, then observe its response to the next feed.
Does stirring a starter make it fall?
It can. Stirring releases trapped gas, so the level can drop immediately. That drop doesn’t show that the microorganisms have suddenly become inactive. For observing a feeding cycle, leave the mixture undisturbed after marking its starting level.
Should I feed it again whenever I see small bubbles?
Small bubbles show activity, but aren’t a reason by themselves to feed again. Give the starter time to develop and follow its feeding instructions. Watching a full cycle helps you avoid confusing early activity with its peak.
Is this the same as a new starter going quiet after its first rise?
Not necessarily. This article describes an established starter. A new culture made from scratch can have an early burst of activity before its longer-term community becomes established. One early rise doesn’t prove it is ready to bake with. Follow the make-your-own starter guide for that process.
Get to know the jar
Mark the level, use scales and give yourself a chance to watch one full cycle. A fallen starter becomes much less worrying once you recognise where it has been.
When your freshly fed starter is ready, put it to work in our Beginner Sourdough Recipe. Take your time and enjoy it. Every bake is an opportunity to learn.
Let’s bake some bloody good bread!