Instead of swelling as a whole loaf, my loaf will often expand in the oven off to the side or the bottom - looking 'blown out', a big tear. This results in a loaf that leans to one side, doesn't rise well, or generally doesn't look good.

Why is this happening and what can I do about it?

4 Answers 4


Blowing out happens because the extra expansion of the bread in the oven, called oven spring, expands further than the skin of the bread can accommodate.

The protein sheets that make up risen bread can toughen when they dry out. When the bread is introduced to the sudden high heat of the oven the water and alcohol vaporizes, filling the loaf with gas. If the outer gluten sheets were allowed to toughen or if the spring is just to great then the sheets have to tear to make room. The tear will happen wherever the sheets are weakest. This seems to be usually in the ugliest spot possible for a blowout.

It would be possible to reduce the spring by baking at a lower temperature but the spring is desirable and results in a lighter texture. The solution must come, therefore, in softening the gluten or controlling the expansion.

Fat softens bread so this problem happens mostly with lean doughs. One possible solution for some breads is to increase the amount of fat in the dough.

Keeping the surface of the dough moist will also help. Keep the dough covered while it is proofing and spraying it with water when it goes in the oven, and, if possible, having a humid environment in the oven will keep the proteins from drying out.

The traditional solution with lean doughs is to allow the blowout to occur but control the direction. In this way the loaf can be both light and attractive.

Slashing the surface of the loaf releases some of the pressure and allows the baker to have some control over the direction of expansion.

  • 9
    I don't think the "yeast goes into overdrive". Instead, I think the yeast quickly dies and the CO2 bubbles that have already been produced by the yeast expand greatly as they are heated. May 11, 2012 at 6:45
  • @HighlyIrregular- You are quite right of course. Corrected. Aug 10, 2012 at 1:42

If you mostly dislike the direction it expands to and the irregular shape of the loaf, you may try to help it a bit. First, take care when forming the loaf – try keeping the last fold crack (as created before the last proof) on the bottom of the loaf when it goes to the oven and slash the surface with a sharp knife or razor, to promote expanding upwards.

The oven inside and the loaf surface must be humid enough or the slashes will dry up and close before the loaf expands.


If you are having issues that it is blowing out on the sides... Like a big tear, then this is probably linked to your questions about steam? If there is not enough hydration in the air surrounding the bread, oh boy, big problems. I had often seen guys pull racks of french bread out of the oven which they had either a. forgot to engage the steam cycle, or b. started it late. As I'm sure you know, when you put the bread in the oven, the yeast goes on a feeding frenzy, which produces more co2, which is what is causing the jump. the steam in the oven is actually retarding the ability of the bread to jump. If there is not enough / no steam present, the bread finds the weakest spot, and tears - all because of this supercharged yeast activity.

I hope that's what you are asking, if not, my apologies.

  • It most certainly is. :)
    – rfusca
    Feb 23, 2012 at 20:57
  • 1
    @rfusca: to ensure proper humidity add a container on the bottom of the oven when you turn it on, so that it will be very hot when the oven will be at temperature. When you put the bread in, quickly throw a handful of ice cubes in the container on the bottom and close the oven. The ice will quickly evaporate ensuring a good level of humidity in your oven.
    – nico
    Feb 24, 2012 at 12:58

I would suspect that your method of final prep may be causing the problem. If you are folding the dough to form your boule or batard you need to ensure that the seam is pinched together and then flipped to be on the bottom of the loaf otherwise you may get a side blowout. It may also be that your slashing is not deep enough to control the expansion.One way to help the loaf is to do the slashing when you place the bread in the oven on the stone or rack as sometimes the slash will close if done to early or not deep enough. You get some very nice expansion patterns when you slash the bread on the stone. Finally don't be shy with the knife or razor, slash at least 1/4 inch or more will help stop the blowouts.

  • 1
    Interestingly- slashing shallowly and at an angle can promote more expansion because the slashes will tear open gradually without drying out the way a deep vertical cut will. Mar 27, 2012 at 15:43

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