The leavening in a chiffon sponge comes from both a chemical agent, baking powder, and the air whipped into the egg whites. This can make it a more practical choice in certain situations than the genoise type of sponge, which does not use a chemical leavener. The vegetable oil contributes moisture and gives the cake a longer shelf life than one made with butter. Another plus is that chiffon cakes tolerate freezing (and thawing) without a significant loss of quality.
The popularity of the chiffon method lessened somewhat in the professional industry following the introduction of the emulsifier method, which is even more convenient and practical in a professional setting, although overall flavor is sacrificed to some extent. Additional information contrasting these and other methods of making sponge cakes is found in the chapter introduction.
In the following recipes, Chiffon Sponge Cake I is used to create round layers that are to be split and filled. Chiffon Sponge Cake II is preferable to use for sheets; it is moister, making it easier to roll when the batter has been spread in a thin layer, or to slice into two layers when the batter is baked in a half-sheet pan.