The cake came out level, baked through, and heavy. Nothing dramatic went wrong —
which is exactly what makes this one hard to diagnose. A classic sponge has no baking powder;
every bit of lift comes from beaten egg. So the question is only ever whether the air went in,
or whether it came back out.
The air never went in: underbeaten eggs
The most common cause and the easiest to misjudge. Eggs with sugar need beating until pale,
thick and roughly tripled in volume — five to eight minutes with a hand mixer,
not one or two.
The ribbon test: lift the beaters. The batter should fall in a ribbon that
sits on the surface for a few seconds before sinking. If it vanishes instantly, keep going.
The air never went in: the eggs were cold
Cold eggs will not take up air properly. Out of the fridge 30–40 minutes before,
or five minutes in a bowl of lukewarm water.
The air came out: the flour was stirred, not folded
Every stir knocks air out. Cut down through the middle with a spatula, sweep along the
bottom, lift over, turn the bowl a quarter. Stop the moment no dry flour shows —
over-folding does the same damage as stirring.
The air came out: fat got into the foam
A trace of yolk in whipped whites, or a greasy bowl, collapses the foam.
Wipe the bowl with a little vinegar before whisking whites.
And if the recipe includes melted butter, fold it in last and down the side of the bowl.
Poured into the centre it sinks and takes the air with it — which is why the cake is dense
at the bottom specifically.
Neither: the oven was too cool
An oven below temperature lets the batter spread and set slowly, so the structure never
catches the air it had. Properly preheated, and check with a thermometer —
most domestic ovens are 10–20 degrees off.
Reading the crumb
| The crumb | What caused it |
|---|---|
| Low and heavy throughout | Underbeaten eggs |
| Rose, but dense at the bottom | Butter or flour folded in badly |
| Rubbery, tight | Over-folded |
| Pale and flat | Oven too cool |
More on this:
Why sponge cake collapses ·
Why egg whites will not whip ·
Why cake cracks on top ·
Cherry Almond Pie