PREVENTING SURFACE CRACKS
The most common complaint is cracking that develops through the middle of the cheesecake during or after baking.
To Prevent Surface Cracking:
Bake the cheesecake in a water bath to keep the oven moisture high and the heat gentle. (A water bath is using a larger pan containing water in which to place the smaller cheesecake baking pan.)
Don't overbake the cheesecake. When perfectly done, there will still be a two to three-inch wobbly spot in the middle of the cheesecake; the texture will smooth out as it cools.
Cheesecake will shrink as it cools. Generously greasing the sides of the baking pan before pouring in batter will allow the cake to pull away from the pan as it cools and shrinks instead of pulling apart from the middle.
Cheesecakes have a tendency to crack, but they don't have to. This favorite American dessert can have a cracked surface for a number of reasons. One cause is air trapped inside the batter - a result of over-mixing. Once in the oven, the air bubble expands and wants to escape from the cake. As it finds its way out of the top of the cake, it creates a crack or crevice in the cake's surface. Another cause of a cracked surface is a drastic temperature change.
How to avoid cracks then? Be sure to mix your cheesecake batter well, eliminating all possible lumps in the cream cheese BEFORE you add the eggs. It is the eggs that will hold air in the batter, so add them last, and mix as little as possible once they are in the mix.
Also, be sure to cook your cheesecake gently. Use a water bath - wrap the bottom of your springform pan in aluminum foil and place it in a larger pan with water in it, just halfway up the outside of the springform pan. This will allow the cheesecake to cook more slowly and evenly.
Finally, cook your cheesecake slowly - at 325º F. After about 45 minutes, turn your oven off and leave the cheesecake inside the turned off oven for another hour. Cool at room temperature with a plate or cookie sheet inverted over the cheesecake to slow the cooling. Only then can you refrigerate the cake, which you will need to do for another 6 hours at least.
If after all this, you still have a crack, make a topping or a sauce for your cheesecake, and tell all your guests that you intentionally made a special crack in the top of the cake to hold more sauce!
***VERY IMPORTANT TIPS ON PREVENTING CRACKING***
Cheesecakes with cornstarch or flour added to the batter do not crack as easily from overbaking. The starch molecules will actually get in between the egg proteins preventing them from over-coagulating. No over-coagulating, no cracks!! Some bakers add extra insurance to a cheesecake recipe that doesn't contain cornstarch or flour, by simply adding 1 tablespoon to1/4 cup of cornstarch to the batter with the sugar.
With today's trend to produce larger and higher cheesecakes and to bake them without the benefit of a waterbath, they tend to overbake at the edge before the center of the cake has reached the temperature necessary to set (coagulate) the eggs. Here, your cheesecake will tend to form deep cracks upon cooling.
Don't bake your cheesecake at too high a temperature (I recommend baking cheesecakes at 300-325 degrees F at the highest) The egg proteins will overcoagulate from too much heat which eventually shrink when cooled, causing cracking usually in its center or tiny cracks all over its top. If you heat it up to fast or cool it down too fast you're also going to get cracks.