The warm weather of summer brings thoughts of outdoor weddings in the garden or at the park. While outdoor settings are ideal for wedding photographs and low-cost decor, warm temperatures and high humidity can wreak havoc on iced (frosted) wedding cakes. No bride wants to cut into a cake that is a dripping mess of melted icing (frosting). The recipe for buttercream, a popular and tasty frosting choice, can be adjusted to help hold its form better under warm temperatures.
Add cornstarch to the recipe to thicken it slightly. This won't change the taste much but makes the icing more durable. Wilton.com recommends 30 ml (2 tbsp) cornstarch for every 230g (4 cups) of confectioners' sugar.
Substitute vegetable shortening for half of the butter in your recipe. This will maintain the buttery taste while adding extra stability, because the shortening holds up much better under high temperatures.
Freeze the cake the day before the wedding, if possible. If the cake will not fit in a freezer, consider freezing any decorative items, like buttercream flowers, and placing them on the cake the day of the wedding.
Transport the cake to the wedding in an air-conditioned vehicle, placing it somewhere that the air will reach, like the floor of the car, rather than the boot.
Store the cake indoors in as cool a location as possible prior to displaying it.
Place the cake in a spot that will not be in direct sunlight. If you have to have the cake in the sun, set up a temporary source of shade, like a patio umbrella, until the moment when the cake will be cut and displayed.
The more butter and other liquids the frosting has in it, the more prone it will be to melting. Other liquids you may want to add to the icing (frosting) -- like colouring, milk or flavours -- increase the chances that it will melt, so proceed with caution when adding to your icing (frosting).
All icing (frosting) will eventually melt if temperatures are high enough, so make sure the bride is aware of this fact and aim to have the cake cutting soon after you put the cake on display.