Why did my cake shrink away from the sides of the tin?

As a cake bakes, water leaves the crumb and the protein and starch network contracts. That contraction is what pulls the edge fractionally clear of the tin, and bakers use it deliberately as one of the doneness tests. The fault version is the same process taken too far: keep applying heat after the crumb has set and it goes on losing water, shrinking and toughening, and the shrinkage becomes obvious rather than marginal.

Step by step

1. Decide whether it is actually a fault.Edge just clear of the tin, cake full height, crumb soft — that is a correctly baked cake. Gap you could put a finger in, top domed and hard, cake noticeably shorter than it rose — that is over-baked.
2. Check the oven temperature with a thermometer.An oven twenty degrees hot sets the outside early and then keeps driving water out of it for the rest of the stated time. This is the usual mechanism behind severe shrinkage.
3. Test doneness earlier than the recipe says.Start checking at 80 per cent of the stated time. A skewer with a few moist crumbs, a top that springs back, and the edge just beginning to draw in — take it out at that point, not five minutes later.
4. Look at how you greased the tin.A heavily greased or oiled side gives the batter nothing to climb. Cakes that need height — whisked sponges, chiffon, angel cake — are baked in ungreased or very lightly greased tins for exactly this reason.
5. Line rather than over-grease.Baking parchment on the base and a collar round the sides for a long bake. Parchment gives a surface the batter can hold and releases cleanly. See `choose-baking-paper-and-foil`.
6. Check for a shrunken cake that is also sunken.Shrunk in from the sides *and* fallen in the middle is not over-baking — it is a structural collapse, and the cause is elsewhere. See `why-did-my-cake-sink`.

Tips

• Shrinkage is a better doneness signal than a skewer in a rich fruit cake, where the fruit will wet a skewer no matter how long it bakes.
• Cakes carry on cooking in the tin for several minutes after they come out. Factor that in rather than adding time at the end.
• A cake that shrinks in a fan oven and not in a conventional one is being over-dried by the airflow. Drop the fan temperature a further 10°C.
• Silicone moulds flex outwards under the weight of batter, so the finished cake genuinely does sit clear of the walls. That is the mould, not the bake.

Common mistakes

• Treating the edge pulling away as the moment to worry — It is the moment to take the cake out. Waiting for it to look 'more done' is how the fault version happens.
• Greasing and flouring heavily to guarantee release — It costs you the grip the batter needs to climb, and parchment releases better anyway. See `stop-cakes-sticking-to-the-tin`.

If it doesn't work