Why It Whips

• It's the high fat content of heavy cream that makes it possible to whip. When the wires of your whisk or beater pass through the cream, they forcibly burst the globules of milk fat in the heavy cream. Like the droplets of oil in a salad dressing, the fats in the cream have a natural tendency to seek each other out and join back together. But the relatively firm milk fats tend to trap air as they form new globules, making air bubbles. As you continue to whip, the bubbles become smaller and finer, eventually forming a smooth, stable foam.

Why It Melts

• These bubbles of fat and air in whipped cream are relatively fragile. After the cream is whipped, gravity begins to slowly erode the light and airy foam. The bubbles at the bottom of the cream begin to pop under the weight of the remaining cream, and over time the foam deflates visibly. The process is quicker at room temperature, and especially a warm room temperature. That's because the milk fat that traps the air is firm at refrigerator temperatures, resisting deflation, but softens dramatically at room temperature.

Maximizing Whipped Cream

• You can maximize your foam's live expectancy by following a few basic steps. First, have the cream, bowl and mixer as absolutely cold as you can make them. The colder the cream is to begin with, the longer it will hold up. Second, keep the foamy whipped cream -- or the decorated dessert -- refrigerated for as long as possible. This slows the cream's deflation. For a less conventional approach, try whipping your cream in a mini food processor or with an immersion blender. You'll get slightly less volume than you would with a conventional mixer, but the finer-textured foam holds up better over a period of hours.

Add a Stabilizer

• Restaurant professionals sometimes need their whipped cream to remain attractive for a day or two, which requires stronger measures. Professionals often add 1 to 2 tablespoons of piping gel to their cream, a clear and flavorless gel ordinarily used for cake decorating. Alternatively, you can dissolve 1 teaspoon of unflavored gelatin for every 1 cup of cream, and add it in a thin stream while whipping the cream to stiff peaks. In a pinch, you can use instant vanilla pudding to stabilize your cream. Adding 1 to 2 tablespoons for each 1 cup of cream will help it hold its shape beautifully, though it yellows the color noticeably.