Why did my cake sink in the middle?

A cake rises because gas expands and then sets into a structure of cooked egg and starch. If the gas escapes before that structure firms — through a temperature drop, over-aeration or simply not enough time — the centre has nothing holding it up.

What you'll need

• Skewer or cake tester
• Oven thermometer (optional)

Step by step

1. Rule out underbaking first, because it is the most common cause.A skewer in the centre should come out clean or with a few dry crumbs. Wet batter means it needed longer regardless of what the recipe said.
2. Check whether the oven door was opened early.Cold air rushing in collapses a partially-set cake instantly. Do not open the door for at least the first three-quarters of the bake time.
3. Check the raising agent quantity.Too much baking powder makes a cake rise fast, over-expand and collapse. More is emphatically not better here.
4. Check your oven's real temperature with a thermometer.Domestic ovens are commonly 10-20°C out. A cool oven bakes too slowly for the structure to set before the gas escapes.
5. Consider whether the mixture was over-beaten after the flour went in.Over-mixing develops gluten and knocks out air. Fold flour in until just combined.
6. Check the tin size against the recipe.A deep mixture in a small tin cannot cook through in the stated time. The middle stays wet and sinks.
7. Use the cake you have rather than binning it.A sunken sponge makes excellent trifle, cake pops or a base for a layered dessert. Fill the dip with cream and fruit and serve it as it is.

Tips

• Weigh raising agents rather than using spoons. A heaped teaspoon can be nearly double a level one.
• Baking powder loses potency over time. If a tub has been open a year, replace it — it does expire.
• An oven thermometer costs very little and explains an enormous number of baking failures.

Common mistakes

• Opening the oven to check in the first half — The temperature drop collapses the uncooked structure immediately, and it will not recover.
• Adding extra baking powder for a better rise — Excess raising agent over-inflates the cake, which then collapses. It also leaves a soapy aftertaste.
• Trusting the recipe's time over the skewer test — Ovens and tins vary. The skewer is the only reliable indicator of a set centre.

Questions people ask