How to Bake Sourdough in a Fan-Assisted Oven: UK Baker’s Guide

Most sourdough guides are written with American deck ovens or Dutch ovens in mind, leaving UK home bakers to piece together advice that was never quite meant for them. The fan-assisted oven — the standard in most British kitchens — behaves differently from a conventional oven, and those differences matter enormously when you are trying to produce a well-risen, deeply coloured loaf with a proper open crumb. This guide is written specifically for bakers working in British kitchens, using ingredients available in UK supermarkets and dealing with the particular quirks of fan ovens.

Understanding Your Fan-Assisted Oven

A fan-assisted oven, sometimes called a fan oven or convection oven, circulates hot air around the cavity using a rear-mounted fan. The result is a more even temperature distribution and faster cooking times compared to a conventional static oven. For most roasting and baking, this is an advantage. For sourdough, it introduces two specific challenges.

First, fan ovens dry out the surface of the dough quickly. Sourdough needs steam in the first 20 minutes of baking to keep the crust supple long enough for the loaf to fully expand. Without steam, the crust sets too early, the loaf cannot spring upward, and you end up with a dense, tight crumb and a pale, leathery exterior. The circulating air in a fan oven strips moisture away faster than a static oven would, making steam retention more critical.

Second, fan ovens run hotter than the dial suggests. As a general rule, reduce the stated temperature by 20°C when converting a recipe written for a conventional oven. So if a recipe calls for 250°C in a static oven, set your fan oven to 230°C. Many UK bakers get burnt bases or overly dark tops simply because they forget this adjustment.

Get to know your specific oven. Bake a few loaves and take notes. Some fan ovens have a stronger fan on one side, which means rotating your loaf halfway through the second bake phase helps even out the colour.

Building and Maintaining a Sourdough Starter in the UK

Before you can bake anything, you need a healthy, active starter. This is a live culture of wild yeast and bacteria maintained in a mixture of flour and water. Creating one from scratch takes around five to seven days.

What Flour to Use

In the UK, strong white bread flour is the most widely available option. Marriages, Doves Farm, and Shipton Mill are all reliable brands stocked in Waitrose, Ocado, and many independent health food shops. A 1.5kg bag of Doves Farm Organic Strong White Bread Flour typically costs around £2.50–£3.00. Whole wheat or rye flour gives your starter a more vigorous start because the bran contains more wild yeast and bacteria. Even adding 20% rye to your white flour starter dramatically improves its activity.

Creating Your Starter

• Day 1: Combine 50g of whole rye or wholemeal flour with 50g of lukewarm water in a clean jar. Stir well, cover loosely, and leave at room temperature (ideally 21–24°C).
• Days 2–3: You may see some bubbles forming. Discard half the mixture and feed with 50g of strong white flour and 50g of water.
• Days 4–7: Repeat the discard and feed process daily. By day five or six, the starter should be doubling in size within four to six hours of feeding and smelling pleasantly tangy, like yoghurt or mild vinegar.

British kitchens are often cooler than the ideal fermentation range, especially in winter. If your kitchen sits below 18°C, fermentation will be slow. Placing your starter jar near (not on) a radiator or in the airing cupboard can help. Alternatively, Aga owners have an advantage here — the top plate of a two-oven Aga maintains a consistent warmth that is close to perfect for starter development.

Ingredients and Quantities for a Standard UK Loaf

The following recipe produces one medium sourdough boule, suitable for a 25cm cast iron casserole dish or Dutch oven — a method that works brilliantly in fan ovens because the pot traps steam without any additional effort.

• 450g strong white bread flour (or a blend of 360g white and 90g wholemeal)
• 320g water (room temperature, filtered or left to stand overnight if using chlorinated tap water)
• 90g active starter (fed eight to twelve hours before use)
• 9g fine sea salt

UK tap water in many cities, particularly London, is heavily chlorinated and can inhibit fermentation. Leaving a jug of water on the counter overnight allows the chlorine to dissipate. Alternatively, a Brita filter jug, which costs around £20–£25, solves the problem permanently.

The Process: From Mix to Bake

Autolyse

Combine the flour and water (leave out the starter and salt at this stage) and mix until no dry flour remains. Cover and rest for 30–60 minutes. This rest period, called autolyse, allows the flour to fully hydrate and the gluten to begin developing without any kneading. You will notice the dough becomes smoother and more extensible when you return to it.

Adding Starter and Salt

Add the active starter to the autolysed dough and incorporate it thoroughly using your hands, squeezing the mixture through your fingers. After five minutes, add the salt and continue mixing for another two to three minutes. The dough will feel sticky and shaggy at this point — that is normal.

Bulk Fermentation

This is the long first rise, during which the dough develops flavour and structure. It typically takes four to six hours at 21°C. In a cooler British kitchen (18°C), expect six to eight hours. In a warm kitchen in July, it could be done in three.

During bulk fermentation, perform a series of stretch and folds every 30 minutes for the first two hours. To do a stretch and fold, wet your hand slightly, grab one side of the dough, stretch it upward as far as it will go without tearing, and fold it over the top of the dough. Rotate the bowl 90 degrees and repeat. Do this four times per set. After four sets of stretch and folds, leave the dough undisturbed for the remainder of bulk fermentation.

Bulk fermentation is complete when the dough has grown by 50–75%, feels airy and jiggly when you shake the bowl, and shows bubbles on the sides and surface.

Shaping

Turn the dough out onto an unfloured work surface. Using a bench scraper and your hand, shape the dough into a tight round by dragging it toward you across the surface to build tension. Rest it uncovered for 20–30 minutes (the bench rest), then do a final shaping before placing it seam-side up into a floured banneton — a proving basket made from cane or wood pulp. A 750g banneton costs around £10–£15 from Lakeland, Amazon, or specialist baking retailers like Breadtopia. Dust the banneton generously with rice flour, which does not absorb moisture and prevents sticking far better than wheat flour.

Cold Prove

Cover the banneton with a shower cap or plastic bag and place it in the fridge for 8–16 hours. This retards the fermentation, develops a more complex flavour, and makes the dough much easier to score. Crucially for fan oven baking, the cold dough holds its shape far better when it hits the hot pot, giving you a better oven spring.

Baking in a Fan-Assisted Oven: Step by Step

Equipment You Need

• A cast iron casserole dish with a lid, or a dedicated Dutch oven. A 4–5 litre Lodge or Le Creuset works well. Expect to pay £30–£50 for a decent Lodge from Amazon, or considerably more for Le Creuset if budget allows.
• A bread lame or a sharp serrated knife for scoring.
• Oven gloves rated for high temperatures — standard oven gloves are often insufficient for removing a 230°C cast iron pot.
• An instant-read thermometer such as a Thermapen (around £65) or a cheaper alternative from Amazon (around £10–£15) to check the internal temperature of the baked loaf.

The Bake

Place your cast iron pot (with its lid) inside the oven and preheat to 230°C fan for at least 45 minutes to one hour. The longer preheat is important — the cast iron needs to be thoroughly saturated with heat, not just warmed on the surface. This is the single biggest improvement most home bakers can make to their results.

When ready to bake, remove the dough from the fridge. Working quickly, invert the banneton onto a piece of baking parchment, score the top of the loaf with confident, swift cuts at a shallow angle (about 30–45 degrees), and lower it into the hot pot using the parchment as a sling. Put the lid on and return the pot to the oven.

Bake with the lid on for 20 minutes at 230°C fan. During this phase, the steam trapped inside the pot does all the work a professional steam-injection oven would do in a bakery. Remove the lid and reduce the temperature to 210°C fan. Continue baking for a further 20–25 minutes until the crust is a deep mahogany brown. Do not be afraid of colour — an underbaked sourdough will have a gummy crumb regardless of how good the fermentation was.

The loaf is done when its internal temperature reaches 96–98°C. This is the most reliable way to know, and it removes all guesswork.

Cooling

Transfer the loaf to a wire rack and leave it to cool for a minimum of one hour before cutting. Ideally, wait two hours. The crumb continues to set as the loaf cools, and cutting too early results in a sticky, doughy interior even if the bake was otherwise perfect. This is one of the hardest parts of sourdough for new bakers to accept, but it genuinely matters.

Troubleshooting Common Fan Oven Problems

Burnt Base, Pale Top

Fan ovens often concentrate more heat at the bottom. Place your pot on the middle
shelf rather than the lowest runner, and avoid preheating a baking tray directly underneath unless you specifically need extra bottom heat. If the base still catches, place a spare tray on the shelf below to deflect some of the direct heat. For a pale top, remove the lid a little earlier or increase the temperature by 10°C for the final uncovered stage.

Loaf Spreads Instead of Rising

This is not always the oven’s fault. A loaf that spreads may be slightly overproofed, under-shaped, or lacking surface tension. However, fan ovens can make the issue more obvious because they set the outer crust quickly. Make sure your dough is properly fermented, shaped firmly, and baked in a fully preheated pot. Strong steam in the early stage also helps support oven spring.

Crust Sets Too Fast

If the outer crust hardens before the loaf has finished expanding, reduce the starting temperature slightly. For example, if you began at 230°C fan, try 220°C fan next time. Keeping the loaf covered for the first 20 minutes is especially important in a fan-assisted oven, as this shields it from the drying airflow and traps moisture where it is needed.

Uneven Browning

Many UK fan ovens have hot spots. If one side of your loaf colours faster than the other, turn the pot carefully after removing the lid, or rotate the loaf itself if baking on a stone or tray. Keep notes on your oven’s behaviour; sourdough improves enormously once you understand your own equipment.

Final Tips for Better Results

Use an oven thermometer if you can, because many domestic oven dials are inaccurate. Do not rely only on stated temperatures. Bake the same recipe several times before making major changes, adjusting just one variable at a time. In a fan-assisted oven, consistency matters more than chasing extreme heat.

If you are converting a recipe written for a conventional oven, a good rule is to reduce the stated temperature by around 10 to 20°C and monitor the loaf closely on the first attempt. Some ovens run fiercely, while others are surprisingly gentle, so treat these figures as a starting point rather than a rule.

Baking sourdough in a fan-assisted oven can produce excellent results once you adapt to the faster, drier heat. With a solid preheat, the right covered baking setup, careful temperature control, and a little observation, you can achieve strong oven spring, a crisp crust, and a well-baked crumb in an ordinary UK kitchen. Learn your oven, make small adjustments, and your sourdough will quickly become more reliable and more rewarding.