Why Sourdough Collapses in the Oven (and How to Prevent It)

Short answer: when a loaf collapses in the oven, the gluten ran out of strength to support the gas before the crust set. Catch it earlier in proof or build more dough strength.

What "collapse" looks like

Oven collapse comes in three flavors:

• Total collapse: dough deflates the moment it hits the oven, ending up flatter than it went in
• Mid-bake collapse: dough rises in the first 10 minutes, then sinks
• Side collapse: one side bulges out and the loaf tips during bake

Each has a slightly different cause but the umbrella diagnosis is the same: the dough was past peak when you tried to bake it.

The over-proofed signal

Pre-bake checks:

• Finger-dent test: dent stays, doesn't spring back at all → over-proofed
• Surface looks slack, almost wet
• Dough flattens immediately when turned out of the basket
• Score marks don't open; dough deflates instead

If you see two of these, the collapse is coming.

What's happening underneath

Two things together cause collapse:

1. Gas overproduction — yeast made more gas than the gluten can hold
2. Gluten breakdown — long fermentation has weakened protein bonds, especially in high-hydration dough

By the time the loaf hits the oven, the gluten can't stretch fast enough to handle thermal expansion. The gas escapes; the dough sinks.

The most common timing errors

How to catch the window

The peak proof window is wider than most beginners think. Use these signals:

• Dough has risen 50–75% from shape (use a clear container or aliquot jar)
• Gentle press leaves an indent that springs back slowly (not fully)
• Dough domes; doesn't flatten
• Surface still has tension when poked

If the dough has risen 100%+ and feels slack, bake it now or accept a flatter loaf.

Build more dough strength

If your collapse pattern repeats even with on-time bakes, your dough doesn't have enough strength. Common causes:

• Hydration too high for your flour (drop to 70%)
• Not enough folds during bulk (do 4 sets in the first 2 hours)
• Skipped lamination (do one mid-bulk lamination for high-hydration dough)
• Over-fermented levain (use levain when it just peaks, not when it's deflated)

The cold retard rule

Cold retard slows but doesn't stop fermentation. A 12-hour retard at 38°F is roughly equivalent to 2 more hours at room temperature.

If you cold-retard for 18+ hours and your starter is strong, you risk over-proof in the fridge. Pull it earlier, or keep cold retards under 12 hours.

Score depth matters

Shallow scores on a fragile loaf can cause side collapse — the dough wants to expand but can't open up the score. Score 1cm deep on overproofed dough; the bread needs the help.

A rescue plan for borderline dough

If you suspect over-proof but haven't baked yet:

1. Flip dough out of basket onto parchment
2. Preheat your vessel hot (500°F)
3. Score deeply
4. Bake immediately
5. Don't bother with steam — the loaf needs to set fast

This gets you a flatter but edible loaf. Don't extend bake time hoping for spring; it's not coming.

Prevention plan

For the next bake:

• Levain at peak, not past
• Bulk to 50–60% rise visible
• Cold retard 10–12 hours
• Bake straight from fridge
• Score deep, bake hot

Most "collapse" loaves come from a single overproofed bulk. Catch the bulk on time and the rest of the bake forgives a lot.

When collapse is a flour problem

Some flours just don't handle long fermentations:

• Soft wheat flours (cake flour, AP) → no
• Bread flour → fine for 12-hour bulks
• High-extraction or whole grain → shorter ferments, more frequent folds

If you're experimenting with rye or whole wheat blends, expect collapse to be more common. Drop hydration 5% and shorten bulk by 1 hour from your usual.