Beat those egg whites!

As promised, more cake tips!

Egg whites provide most of the structure for the cake. Well, it depends on the cake, I suppose—but generally, yes.
So here’s the low and dirty on egg whites, from Joe at Joe’s Bakery. Egg whites have very little flavor and are made up of about 90% water. The 10% contains the proteins, about half of the total proteins of the egg. These proteins are very different from the proteins in the yolk, and are one of the favoritest things of bakers. Why? Because “they have regions along their length that love water and other regions that hate water.” With just a bit of work these fantastic proteins can be “uncoiled” to create foams because they love the surface of bubbles. Hooray! Happiness all round, right? Joe goes on: “once all those proteins are arrayed at the surface of the bubble, they begin bonding to each other, if rather weakly. The network they create reinforces the wall of the bubble, preventing it from popping.”
He recommends using a hand mixer rather than a stand mixer, because with a hand mixer you can be sure to get all of those little corner bits missed by stand mixers.
He also recommends using some sort of an acid stabilizer (read: lemon juice, cream of tartar, etc.) after you have whisked it up and before you fold it into the rest of the recipe.

So. Some general tips on whipping egg whites:
*Temp: 
         *Make sure the egg whites are at room temp. Which means putting them out on the counter at least 30 minutes before you start. If you’re in a desperate hurry, you can put them into a bowl of very warm water for 5-10 mins. Don’t boil them. According to some people, boiled eggs are delicious in their own right. But not in eggs. Gross.
*Tools:
         *If you have a choice in the bowl you use, copper is best. Don’t have a copper bowl? Well, small, deep bowls with rounded bottoms are pretty fantastic when you’re dealing with 4 or 5 egg whites. For more than that, just use a larger deep bowl.
         *No aluminum bowls! No wooden bowls! Wooden bowls are great for salads, where their fabulous oil-absorbing (which we call “seasoning”) properties mean they make things tasty. Fats + egg whites=sadness. More on that later.
         *If you use a stainless steel or glass bowl, add cream of tartar or lemon juice.
*Add-ins:
        *Add an acid! Acid is a happy thing. It stabilizes and adds volume. Happiness.
        *1/8 tsp acid (lemon juice, vinegar, or cream of tartar) for each egg white (with the exception of meringues. In meringues, 1/8 tsp per two egg whites.)
        *Add the acid just as they begin to become frothy during beating
        *Don’t add sugar while you beat! They lose structure. Sadness.
*Method:
        *Begin at a slow speed before moving up to higher speeds.
        *Hand mixers are best. Stand mixers work too, but hand mixers are preferred.
        *Don’t overbeat them!
         *Don’t let them sit! More weeping happens.