Having sufficient but not excessive dough strength is extremely important when baking sourdough bread. We want our dough to be strong enough to hold on to the gaseous byproducts of fermentation but not so strong it's unable to expand and relax outward and upward in the oven. This guide on stretching and folding sourdough focuses on dough strengthening during bulk fermentation to get the dough strong enough—but not too strong. This just enough is the dough's strength sweet spot, the point which eventually yields a loaf with a tall rise and a beautiful internal structure.
Before we go in deep, I think it's helpful to state why the stretch and fold technique is useful quickly. At a high level, with each simple set of stretches and folds you:
I like to think of dough as soft taffy (although technically, bread dough is foam). Gasses can get trapped in this sticky and amorphous substance, get pushed and moved around, sometimes coalesce into larger bubbles, and sometimes smash and turn into smaller ones. If the blob is too stiff—like a thick and dried taffy, it resists stretching outward (high elasticity). If the blob is extremely stretchy—like taffy that's warm or fresh—it spreads outward without resistance (high extensibility).
So the goal is to get the balance right, to allow for some spread and expansion, but not too much. When the dough is first mixed, it's shaggy, weak, and falls apart readily (although not as much if you autolyse beforehand). After mixing and some kneading, the dough most along toward becoming stronger and able to hold shape. If the dough isn't mixed or kneaded to full development (e.g., full windowpane), adding in sets of stretch and folds during bulk fermentation will help continue its progress toward a stronger, more cohesive dough that's able to trap gas and hold its shape all the way to bake time.
First, let's look at what stretch and folds are, then how to do them.
What are stretch and folds?
In nearly every bread recipe (and usually sweet sourdough recipes, too) at this website, you'll find at least one set of stretch and folds during bulk fermentation, spaced out by some interval. I call them a set because I typically perform four stretches and four folds, one at each cardinal direction of the dough (North, South, East, and West), in each set.
First and foremost, these sets are performed to strengthen the dough. The act of stretching the bread dough up and over further develops the dough's gluten, bringing increased elasticity. But these sets also give you a chance to equalize the dough's temperature. Think, for example, about a dough that's sitting on a warm surface; the dough at the bottom of the container will be warmer than the top, which could mean varying fermentation rates throughout the dough (because, as we know, dough temperature is critical in bread baking).
These sets also give us a chance to check in with the dough to see how it's progressing through bulk fermentation. Instead of just letting it sit there for the 2 to 4 hour bulk fermentation, we are somewhat forced to look in on the dough, feel it, decide if it's moving quickly that day or is a little sluggish. These little opportunities are valuable moments to step back and assess the dough.
Compared to more-intensive dough strengthening, like the slap and fold technique, these folds may feel like they aren't doing much. But in fact, they are. Even a single set of stretch and folds adds a significant amount of strength to your dough, and the vigor of the stretches and folds plays a role as well (more on this later).
Recommended reading: The Importance of Dough Temperature in Baking.
How to stretch and fold sourdough during bulk fermentation
There are many ways to actually perform the stretching and folding, and in the end, it comes down to preference. Some methods are better for rectangular tubs, some are better with round bowls, and others are better for deep containers. While most of the photos in this post show my dough in a round container, the folding styles shown will also work for a square or rectangular tub. When I'm using a dough tub for larger dough quantities (4kg+), I typically opt for the “gentle” folding approach in the video below.
I generally perform two different methods for stretching and folding, a strong style and a gentle style. I choose between the two based on the dough's state at that moment: if the dough is weak and slack, a strong set is appropriate. If the dough is already strong, a gentle set will suffice. When I mix or knead the dough up front, and especially when using the slap and fold kneading technique, I do more gentle sets than strong ones as the dough is already well on its way to its ideal strength (more on this later).
Let's take a look at a strong set.
First, it's helpful to have a small bowl of water nearby to dip your hands into before touching your dough. This helps keep the dough from sticking.
Then, I use my wet hands to pick up a side of the dough, stretch it up, and fold it over. That's one of four for the set. Next, I rotate the bowl 180° (turn it, so you're now looking at the opposite side you just folded) and repeat. This results in a sort of tube shape in the container. Then, I rotate the bowl 90° and do another stretch and fold. Finally, rotate the bowl 180° and do the last stretch and fold over. You'll now have a neat package folded up in the container. Cover the dough, set a timer, and wait until the next set.
Simple, quick, effective. Let's look at some video of how to stretch and fold sourdough during bulk fermentation.
How to stretch and fold sourdough: strong set
Strong sets involve a little more stretch of the dough and impart significant strength. Notice I first quickly dip my hands in water to prevent them from sticking. With this strong set, I stretch the dough up and fold it all the way over to the other side. Then, rotate the bowl and continue. At the very end, I lift the dough to keep the dough gathered up in the bulk fermentation container.
How to stretch and fold sourdough: gentle set
I've heard these gentle stretch and folds called “coil folds,” but as long as I've been baking, I've called them folding under. But the important thing is they're very gentle yet still effective. You can see the dough is already rather strong before I start folding, so a gentle set is more than adequate. In the end, the dough is also neatly gathered in the container.
Leave the dough gathered up
Regardless of how you stretch out and fold your dough, I find it's always beneficial to leave the dough gathered up neatly in the bulk fermentation container. This means the dough has a smooth surface on top with the sides tucked in and down. Then, when the dough rises for the remainder of the first rise, the dough cleanly moves up in one solid mass instead of having some sections move up at one side and some on the other. Cleanly bundled dough allows you to assess the dough better as it rises during bulk fermentation.
In addition to helping you assess when the dough's fermentation time, when it comes time to divide it, you're working with a clean, smooth top that divides neatly and is easier to work with.
How many stretch and folds?
Ultimately, the number of sets of stretch and folds will depend on the dough composition (flour choices, hydration, amount of levain or starter, etc.) and how it progresses that day. The point of these sets is to move your dough along the spectrum from weak to strong, ever closer to the right amount of dough strength (which I call the “ideal dough strength” below). Some doughs need more help to get there; others are strong enough and need less help.
For most dough recipes, I start with a baseline of 3 sets of stretch and folds. If the dough comes out of mixing super weak, I'll increase that number, and if it's firm, I'll skip sets.
The best way I can help visualize this is with the diagram below. I see the dough as always moving from left to right, starting as a shaggy, weak mess. As you mix, knead, and strengthen, you begin to quickly move the dough toward the stronger side (the arrow's length below shows the rapid strengthening). During bulk fermentation, each set of stretch and folds (S & F) moves the dough farther along to the right. As discussed above, the strong sets move the dough farther, and the gentle sets a little less.
Eventually, your dough reaches the spot where it's strong enough, the ideal point at which it can rest for the remainder of bulk fermentation without intervention.
What is the ideal dough strength anyway? Well, there's no ideal; that's my imaginary point where I feel the dough is strong enough. As I'll discuss soon, that point depends on what's to come for the dough in the rest of the process. For example, if you're preshaping (which adds more strength to the dough), that ideal dough strength dashed line will move to the left as it needs less strengthening later.
Note that what's not shown in the diagram is the strengthening of the dough organically due to fermentation, but I'm ignoring that concept for now as we're focusing on mechanical strengthening.
How long to wait between sets of stretch and folds
The amount of time isn't super important; what is important is the dough state when you go to do your stretch and fold set. You want the dough to have relaxed outward, possibly spreading to fill your bulk fermentation container.
Consider for a moment a dough that's been stretched and folded 30 minutes ago, but when you go to give it another set, it's still gathered up in the center of your bowl, looking strong with defined edges. If you tried to give this strong dough a stretch and a fold-over, you'd be fighting the dough, forcing it to comply. Instead, give the dough more time to rest, let the gluten relax and become extensible again, and then perform another set (if at all).
Generally, I like to wait around 30 minutes between sets. Thirty minutes seems to be the right time for most doughs to relax and spread out in the bulk fermentation container—precisely when you want to give it another set.
However, if you've minimally mixed or kneaded the dough, and the dough is very slack and weak, you might need only 10 to 15 minutes rest between sets. In this case, sometimes I'll perform a few early sets spaced out by 15 minutes, then increase that time later as the dough strengthens.
How to know when to stop doing stretch and folds
This can sometimes be a tricky call to make, and you have to take your entire baking process into account. You must consider what else is happening to your dough after bulk fermentation: are you preshaping (if so fewer sets are needed)? Do you intend to shape the dough lightly or with a heavier hand (more sets and fewer sets needed, respectively)? Is the dough going to be retarded in the fridge overnight (potentially fewer sets as the cold temperature will bring strength)?
All of this goes back to the strengthening diagram I showed above. If you're moving that dashed ideal dough strength line to the left or right, you can adjust the number of sets required.
Before performing a set, I use my judgment right there and then. I ask myself whether the dough was mixed/kneaded longer than usual, has it has several sets already, does it have defined edges and look gathered up in the bowl, or how am I handling the dough later down the line—all of these help me assess whether I think the dough needs more strength.
Let's take a look at two examples. First, let's look at a weaker dough, one very early in bulk fermentation.
As you can see, the weak dough above still looks shaggy and sloppy; it doesn't have sufficient structure. It needs a set of stretch and folds (and I'd likely give it a strong set).
On the other hand, let's look at stronger dough.
The dough in the image above clearly looks smoother, has defined edges, and (drastically) domes downward at the edges. You can feel that it's stronger just by looking at the image. With the above dough, if I had already done a set or two, I'd leave it to rest until divide time1.
How does the autolyse technique effect stretch and folds?
In my guide to using the autolyse technique, I talk about how performing an autolyse can lead to a dough that's already stronger out of the gate. Usually, when I autolyse, I can get away with less mixing up front, and that's the point at which I usually adjust. But again, dough strength moves along a continuous spectrum. If I autolyse and mix for a long time, I'll likely need a few (if any) sets of stretch and folds. Alternatively, if I autolyse and mix gently, I might still need a set or two.
So, it all depends! Having an autolyse doesn't necessarily mean I need more or fewer stretch and fold sets, but it starts the dough at a stronger state.
Final words on how to stretch and fold sourdough
One final word on dough strength: remember that more stretches and folds do not mean you'll have bread with a more open crumb. This is a common misconception, the thought that a stronger dough will yield a loaf with a wildly open crumb and open interior. This goes back to what I said in the beginning: you want to find that ideal dough strength, that point at which your dough is strong enough to trap gas and hold its shape but not so strong it can't expand optimally in the oven.
Now that you know how to stretch and fold sourdough during bulk fermentation, check out my guide to proofing bread dough, which will be the baking step right after you shape the dough at the end of bulk fermentation.
if you're looking for a recipe that calls for several sets of stretch and folds, check out my best sourdough recipe—it's minimally mixed upfront and instead uses sets of stretch and folds to strengthen the dough. If you're new to baking sourdough bread, check out my new baker, start here guide.
And judging by the level of fermentation in the dough, it won't be long!↩