Sourdough technique

    How to Get Large Blisters on Your Crust

    Large, shiny blisters come down to three things working together: proper fermentation, a cold proof, and strong steam. Here’s how to nail each one.
     
    How to Get Large Blisters on Your Sourdough Crust

    The core principles

    Blisters form when steam gets trapped just beneath the crust surface during baking. To make that happen consistently, you need the right dough, the right proof, and the right bake environment.
    1

    Build the right dough

    Hydration is your starting point. Aim for 70–75% or higher if your flour can handle it — wetter doughs blister more readily. Stick to white flour where possible, as whole wheat and rye-heavy doughs blister far less easily.

    Although I almost always include at least 20% whole-wheat or spelt flour in my recipes, I still achieve great blistering.

    When shaping, build tight surface tension and use as little bench flour as you can. Too much flour on the surface dulls the crust and actively works against blistering.

    2

    Cold-proof overnight

    After shaping, refrigerate the loaf for up to 12 hours. This long, cold retard does two things: it develops flavour and, crucially, it keeps the dough surface cool so it can blister before the crust has a chance to set.

    I place my bread in the fridge uncovered, which helps the blistering process a lot. Bake it straight from the fridge; don’t let it warm up first.

    3

    Bake hot with plenty of steam

    Preheat your oven thoroughly and bake at 250°C (480°F) if your oven allows it. Steam is non-negotiable during the first stage of the bake:

    Dutch oven — keep the lid on for the first 25 minutes to trap steam naturally. Add at least 2 blocks of ice cubes at the start.

    Open bake — use a strong steam source for the first 10–20 minutes.

     Whichever method you choose, ensure steam is present from the very first minute. Remove the lid or steam source for the second half of the bake to allow the crust to develop colour and become crisp.

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