2Type of cakeFrom what you've said, I'd say you're making a chiffon cake, with separate whipped egg yolks and egg whites. (Whole egg whipping for sponge cake. (Pure egg whites whipped to do angel cake) chiffon cake, then the whipping of egg whites is very important. This well done can be said to be successful 3/4. To beat to 9 points, egg white short peaks appear, the basin inserted a chopstick will not fall down.
3. The whipping of the egg whites I think the reason for your failure is that the egg whites are not whipped well. The natural will not be fluffy (because the egg white is by whisking the air into the hair) the next time you beat a few points of attention. Use fresh eggs. Otherwise, if the eggs are left for a long time, the egg white will become more alkaline and will not be easy to whip. The pots and utensils must be free of water, oil and egg yolks, otherwise it will be difficult to whip. You can also add some acidic additives such as cream of tartar, white vinegar, etc. to make it easier to whip. When beating, first beat out coarse foam, and then add sugar in 3 times now in winter can be in the water heating a little beat, of course, not too hot directly to the egg white on the boil is not. Can pay attention to these egg whites will certainly be whipped successfully.
4, mixing techniques cake batter mixing techniques is also very important. You can't beat the eggs in the basin like a circle mix, otherwise it is easy to get out of the gluten. You have to use the way to cut vegetables, be gentle.