Why does my bread blow out on the bottom?

The bottom seam was not sealed well, creating a weak point. Pinch the seam firmly and place seam-side up in the banneton.

Does underproofing cause blowouts?

Yes. Underproofed dough has more oven spring. If scores are not deep enough, steam escapes elsewhere.

Can I prevent side blowouts?

Score more or deeper to give steam adequate escape. Check shaping for weak spots or uneven tension.

Blowout

Baking

A blowout occurs when steam escapes from somewhere other than your score marks—usually the bottom or sides. This happens when the score is inadequate or the dough has weak spots.

Try This Right Now

1The bread is still edible—blowouts affect appearance, not taste
2Note where blowout occurred for next time
3Score deeper and wider on your next loaf

Detailed Solutions

Deeper Scoring

Easy

Give steam a proper escape route.

Score at least 1/4 inch deep
Make scores long enough to span the loaf
Multiple scores distribute expansion
Score confidently—hesitation causes shallow cuts

Check Shaping

Moderate

Ensure no weak spots during shaping.

Create even tension across the surface
Seal the bottom seam well
Avoid trapped air bubbles
Check for tears before proofing

Why This Happens

Blowouts happen when expanding steam finds a weak point easier to escape through than the score marks. Contributing factors include: Scoring too shallow, Weak spots in dough surface, Poor seam sealing during shaping, Underproofed dough with too much oven spring, Trapped air bubbles.

Prevention for Next Time

Score deep enough—at least 1/4 inch—to create a proper vent
Seal the bottom seam well during shaping
Ensure even tension across the dough surface
Do not underproof—adequate proofing reduces explosive oven spring

Related Issues

Having other problems? Check out these related troubleshooting guides.

Underproofed No Ear Dough Tearing Flat Loaf