Cold Proof Sourdough: How Long, What Temperature and Why
By Boulie · Published
The cold proof, also called a cold retard, is the single most useful trick for fitting sourdough into a normal life. You shape the loaf, put it in the fridge, and bake whenever suits you over the next day or two. It also makes the bread taste better and easier to score.
Here’s how long to cold proof, what temperature to aim for, and how to plan around it.
What a cold proof does
At room temperature the yeast and bacteria in your dough work quickly. In the fridge they slow right down, but they don’t stop. That has three effects:
- Flexibility. The proof stretches from an hour or two to many hours, so you choose when to bake.
- Flavor. The long, slow fermentation develops more acidity and a deeper, more complex taste.
- Handling. Cold dough is firm, so it holds its shape, scores cleanly and keeps a tight surface when it goes into the oven.
How long to cold proof sourdough
| Cold proof time | What to expect |
|---|---|
| Under 8 hours | Works, but you lose most of the flavor benefit |
| 8–12 hours | Mild flavor, an easy overnight bake |
| 12–16 hours | A comfortable window for most loaves |
| 16–36 hours | Noticeably more sour, still well behaved for most doughs |
| 36–48 hours | Very sour; watch for slackness |
| Over 48 hours | Risk of over-proofing |
These assume a fridge at about 3–5 °C (37–41 °F) and a dough that finished bulk fermentation at the right point. If bulk ran long or your kitchen was warm, stay at the shorter end.
The best fridge temperature
Aim for 3–5 °C (37–41 °F). Many home fridges run warmer near the door and on the top shelf, and every time the door opens the temperature climbs. If your loaves seem to over-proof in the fridge, put the banneton at the back of a lower shelf, or check the fridge with a thermometer.
When to put the dough in the fridge
The cold proof usually comes after shaping:
- Finish bulk fermentation at room temperature until the dough has risen about 50–75% and looks airy and domed. The bulk fermentation calculator estimates how long that takes from your dough temperature.
- Pre-shape, rest, then shape with good surface tension.
- Place the loaf seam-side up in a floured banneton, cover it so it doesn’t dry out, and put it in the fridge.
Some bakers let the shaped loaf sit at room temperature for 30–60 minutes before it goes in the fridge, especially when bulk was on the short side. In a warm kitchen, put it straight in.
Baking straight from the fridge
There’s no need to warm the dough up first:
- Preheat the oven and your Dutch oven or baking stone fully, usually for 45–60 minutes.
- Turn the cold loaf out onto parchment, score it immediately and load it.
- Bake as usual. Cold dough often gives a cleaner ear and a better shape.
If you poke the dough before baking, remember that cold dough springs back more slowly than warm dough, so read the poke test leniently.
A sample schedule
| When | What to do |
|---|---|
| Saturday 9:00 | Mix the dough using a starter at peak |
| 9:30–12:00 | Stretch and folds every 30–45 minutes |
| Around 14:00 | Bulk done (about a 50–75% rise at ~24 °C / 75 °F); pre-shape |
| 14:30 | Shape and put it in the fridge |
| Sunday 8:00 | Bake straight from the fridge (about 17–18 hours of cold proof) |
To have your starter peak at the right time for the morning mix, see the sourdough starter feeding schedule.
Troubleshooting the cold proof
- Loaf spreads and won’t hold a score: it probably over-proofed, often because bulk ran long or the fridge is warm. Shorten bulk or the cold proof next time. More in over-proofed sourdough.
- Dense loaf with a tight, gummy crumb: bulk was likely too short. The fridge slows fermentation, it doesn’t fix an under-fermented dough.
- Dry skin on top: cover the banneton with a shower cap, bag or tea towel.
- Too sour: shorten the cold proof, or use a younger starter.
How Boulie helps
A good cold proof starts with a starter at peak. Boulie learns your starter’s rhythm from each feed you log and predicts when it will peak, so you can mix at the right time. The guided bake mode then takes you through mixing, folds, bulk and shaping with alarms, so the loaf goes in the fridge on time.
Key takeaways
- 12–16 hours in a fridge at 3–5 °C (37–41 °F) suits most loaves; 8–48 hours works.
- Longer means more sour. Very long cold proofs risk over-proofing.
- Cold proof after shaping, once bulk has risen about 50–75%.
- Bake straight from the fridge: cold dough scores cleanly and holds its shape.
Frequently asked questions
How long should I cold proof sourdough?
Most shaped sourdough loaves do well with 8–48 hours in the fridge, and 12–16 hours is a comfortable window that fits an overnight schedule. Shorter gives a milder loaf, longer gives a more sour one. A dough that was already well fermented at room temperature needs less time.
What temperature should the fridge be for a cold proof?
Around 3–5 °C (37–41 °F). Fermentation keeps going at that temperature, just very slowly. A warmer fridge, or one that is opened often, speeds things up, so shorten the proof or watch the dough more closely.
Can you bake sourdough straight from the fridge?
Yes, and many bakers prefer to. Cold dough is firmer, easier to score and holds its shape better on the way into the oven. Bake it straight from the fridge in a fully preheated oven; there's no need to bring it back to room temperature.
Can you cold proof sourdough too long?
Yes. Fermentation slows in the fridge but doesn't stop. After two days or so many doughs start to become slack and very sour, and a dough that went in already over-proofed can go too far much sooner. If it spreads and the poke doesn't spring back, it's gone too far.
Should I cold proof during bulk fermentation or after shaping?
Both work. The most common approach is to finish bulk at room temperature, shape, then cold proof the shaped loaf in a banneton. Some bakers retard the bulk dough instead and shape the next day. Cold proofing the shaped loaf is simpler and gives easier scoring.