Chiffon cakes are very light cakes based on vegetable oil, and require a special pan that will support the airy batter as it bakes. Most bakers use a tube chiffon cake pan, though a small round or square pan can be substituted in an emergency. The material of the pan can also affect the baking process, with dark-colored metal pans or glass producing browner cakes and heavy pans retaining heat better than light ones. Handling your chiffon cake properly is just as important as the pan, as it should be cooled upside down to prevent a dense result.
Most chiffon cakes are made from cake or pastry flour, separated eggs, and sugar, as well as vegetable oil and baking powder. The high oil content keeps the cake fresh even at cool temperatures, and the baking powder and beaten egg whites create a fluffy, foamy batter that rises to as much as double its original volume during the baking process. This batter may sink in the oven if it doesn't have enough support from the pan, however, producing a dense, unpalatable cake.
The best chiffon cake pan shape is the tube or Bundt pan, which has a slender central cylinder that supports the chiffon batter, producing a ring-shaped cake. If you don't have a tube pan available, you can substitute an 8- to 9-inch (20- to 23-cm) round cake pan. You can also use a half-sheet jelly roll pan to produce a very thin, broad chiffon cake suitable for cutting and rolling.
Most types of cake pans are made of aluminum or steel, often with a nonstick coating applied to the surface. Choose dark-colored metal pans over light ones, as they produce a more consistently-brown cake. Glass and ceramic tube pans are relatively rare and usually smaller than their metal cousins, but their greater thermal mass means that they retain heat well, baking very evenly. A silicone chiffon cake pan browns relatively poorly, but makes removing the cake and cleaning the pan very easy. Since silicone is flexible, you may need a cookie sheet or metal frame to stabilize the pan.
Even the best chiffon cake pan won't keep your cake fluffy if you handle it roughly after baking. While the cake is warm, its structure is still malleable, and it can fall. Always cool chiffon cakes upside down by supporting tube pans on a bottle threaded through the hole in the pan, or by supporting round or flat pans on glasses set at the corners. Don't let the supports touch the cake itself, and don't move the cake much before it cools completely.