Sifting
Flour passes through a sieve so lumps break and air gets in.
What to do
- Sift the flour with the baking powder, when the recipe uses it, so it spreads evenly.
- Work over a bowl. Break whatever stays in the sieve and sift it again.
- Weigh after sifting if the recipe means sifted flour.
A common slip. A lump of baking powder leaves a bitter pocket in the cake.