The two most common reasons are cutting it too soon and underbaking. A loaf is done at 205–210°F (96–99°C) inside, and the crumb finishes setting as it cools — wait at least 60 minutes before you slice.
At least 60 minutes, better two hours: steam is still cooking the middle.
2
Check the inside temperature
A probe thermometer in the centre should read 205°F (96°C) or more.
3
Bake it darker
Leave it in for the last few minutes with the lid off until the crust is deep brown — usually 20–25 minutes.
4
Look for dense streaks
Tight, wet streaks near the bottom mean it was underproofed: give the next one a longer bulk.
5
Lower the water
Very wet doughs are harder to bake through. Try 70% instead of 80%.
6
Check your starter
A weak starter makes a slow, heavy dough. Use it at its peak, when it has doubled.
Why
Gumminess is starch that has not set — either it never got hot enough, or it was cut while still full of steam. Underproofed dough has fewer bubbles for the heat to travel through, so it bakes through last.
Questions
Can I put a gummy loaf back in the oven?
If you have not cut it yet, yes — ten more minutes. Once cut, toast the slices.
Why is only the bottom gummy?
Usually underproofing, or a baking stone or pot that was not fully preheated.
Is gummy sourdough safe to eat?
Yes, it is just underdone. Toast it and adjust the next bake.
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