If you want to send a cake decorator into panic mode, mention you're planning a beach wedding. In August.
Ohhh, that melting buttercream! Those droopy fondant flowers ! All the bleeding colors!
Heat and humidity definitely don't do cakes any favors. But while you can’t control the weather, you can take a few crucial precautions to keep your cakes looking and tasting good.
Some cake fillings and decorations suffer more in the heat than others. On the hottest days, cake decorators usually steer clear of custard or bavarian cream, which can spoil or turn a cake soggy. Same goes for certain types of frosting, especially those that typically require refrigeration: Think cream cheese or whipped cream. Some kinds of ganache also suffer in the heat (chocolate candies melt in the sun, right?).
So what should you use instead? Buttercream or fondant tend to be the best bets for decorating cakes when the weather's hot and humid, but you'll need to make some adjustments to keep those ingredients in top shape, too.
The Buttercream Solution
When using buttercream in hot weather, you'll want to tweak the recipe to stabilize it. You can do this in a few different ways. Some decorators will substitute part of the butter with shortening, which doesn’t melt as quickly and holds its shape a bit better.
Another trick is to add some type of starch to the buttercream before using it to decorate the cake. Cornstarch (about two tablespoons per three cups of icing) makes the icing a bit sturdier, which will help it fare better in the heat.
There are other options, too. Powdered milk or melted marshmallows, when added to frosting and mixed thoroughly, add stability plus extra flavor. Or you could add meringue powder, gelatin or instant-pudding powder.
While it's true that many of these tricks will help stabilize whipped cream too, be super careful if you're planning to go that route on hot days. Whipped cream is extremely heat sensitive, so you'll still need to refrigerate it right up until the last moment.
The Fondant Fix
Fondant has a lower fat content than buttercream, plus it's often stabilized by gelatin — so it tends to hold up the best in the heat.
But that doesn't mean it's invincible: The hot sun can make delicate fondant shapes droop and food coloring bleed, so you'll want to keep your cake in as cool and dry a place as possible.
When you're decorating with fondant in hot weather, use common sense: This might not be the day to test out a flower design with the finest fondant tendrils, for instance. Sturdier decorating elements will help you avert disaster.
No matter what you do, the reality is that even the most beautifully planned, carefully stabilized decorations can get damaged in the heat. So be smart. Keep your cakes chilled until the last possible moment, and out of direct sunlight.
Finally, make sure to get any extra slices into the refrigerator or indoors as soon as you can. All those exposed cake fillings? Yup, they'll melt quickly in the heat, too. So get those delicious cake leftovers to a safe place ASAP!