Philip Harben explains the need to aerate flour dough, and how to do it. Joan Robins illustrates the basic principles by making short paste, flaky paste, and basic cake mixture.

If a lump of paste made of plain flour and water is cooked, the gluten in the flour will cause it to set firm. The result will be hard and rubbery or board-like. But if the flour paste can be thoroughly permeated with air, so that what was solid and compact becomes open and sponge-like, then the result will be light and pleasant to eat. This lesson illustrates the 'manual' method of aeration in which the paste is so handled that air is introduced in the form of pockets (short paste) or layers (flaky paste).