This kind of frosting relies on a combination of boiled sugar syrup and whipped egg whites. The process starts with water, cream of tartar, sugar, corn syrup and egg whites whisked together in a double boiler. As soon as the mixture reaches 140 degrees Fahrenheit, you must immediately beat the mixture continuously for five to seven minutes. If you stop beating or allow the heat to rise too much, the mixture will fall or the egg whites will overcook. After the frosting is done, allow it to cool for two to three minutes before using.

Seven-minute frosting is popular for use on summer baked goods because of its light texture and ability to resist heat. While simpler buttercream frostings often become crusty or lose their shape in hot weather, seven-minute frosting stays crisp and attractive. Because this food relies on egg whites, you should not freeze or refrigerate it. Exposure to sudden changes in temperature can cause the frosting to deflate or sweat, just like a meringue.

In the short term, this kind of frosting is quite stable. It sets up quickly after application, forming a crisp but not hard surface facilitated by bubbles of egg white. In the long term, seven-minute frosting stores poorly. It usually deflates within 24 hours, as the egg whites revert to a liquid state and the cake absorbs them. If you need a frosting that lasts longer but will hold up to heat, consider a cooked buttercream or another more stable recipe.

Pay attention to the other ingredients in your cake before choosing seven-minute frosting. This delicate, airy substance performs well on chocolate cakes, especially in warm weather, but you can't directly flavor it with chocolate. Adding fatty ingredients such as baking chocolate or whipped cream causes seven-minute frosting to deflate. For cakes that require these ingredients, substitute a fat-based frosting with greater stability.