So you have lined up all your ingredients on the kitchen counter like you see on TV, you've painstakingly followed the recipe instructions to produce one big gooey mass, which you in turn place in a preheated oven. After trying to keep yourself busy for an hour or so and avoiding the temptation of peeking into the oven prematurely, which if you succumb will ultimately ruin your efforts, you are usually graced with a scrummy home baked cake. But have you ever wondered what goes on in the process that leads up to and the actual baking of your cake, which produces such a stark transformation of ingredients?
Basically, it all comes down to science; a combination of chemistry and physics. I hear you groan, however, it's not as complicated or even as boring as it sounds (I was never very good at the sciences myself!). When you cream the sugar with the butter - that is use your electric beater to combine the two - the mixture turns pale and creamy, hence the verb to cream. Scientifically, what is happening, is that the motion of the beaters causes air to be incorporated into the cake mixture and these minute bubbles of air individually become trapped by a thin layer of fat, from the butter, consequently causing the mixture to change colour.
The air bubbles prevents your cake from resembling a lump of concrete when it returns from the oven, however, one more ingredient is required to ensure the air remains where it is throughout the baking process. In adding a quantity of beaten egg to the mixture, the egg white forms a protective coating around each air bubble. As the cake bakes and it's temperature rises, this coating hardens, which prevents the fats collapsing and the air escaping.
A cake rises in the oven because the hot temperatures cause the trapped air bubbles to expand. Meanwhile, the gluten in the flour has created a stretchy mass around these air bubbles contributing to the cakes growth. This expansion process should not be interupted i.e. opening the oven door in the early baking stage is a complete no-no! The sudden drop in temperature will cause the air in the cake to contract, rather than expand, and your cake will collapse. After about three-quarters of the baking time has surpassed, it is safe to take a peek (afterall, you don't want your masterpiece to be overbaked or ruined by a burned top!) The temperature of the cake will have reached that of the oven and the gluten will have ceased to stretch. As a result the shape of the cake is fully formed.
So that's what happens when your masterpiece turns from ingredients to mix to cake! If you are anything like me and patience is not your strong point, this small piece of knowledge will give you something to think about, a distraction from doing the terrible and interfering with your creation in it's final stages of glory! I wish you all a future of very happy baking!