(as excerpted from http://www.weddinggazette.com/)
It’s rich and creamy, is easily colored or flavored, and is used for fancy decorations like shells, swags, basketweaves, icing flowers, etc. Since it’s made almost entirely of butter (hence the name), buttercream has a tendency to melt in extreme heat, so it’s not recommended for outdoor weddings.
Martha Stewart’s favorite. This icing looks smooth and stiff and is made with gelatin and corn syrup to give it its helmet-like appearance (it’s really very cool looking). It looks best when decorated with marzipan fruits, gum paste flowers, or a simple ribbon, like Martha likes to do. Although not as tasty as buttercream or ganache, fondant does not need refrigeration so it’s the perfect icing to serve at your beach wedding.
A mix of confectioner’s sugar and milk or egg whites, royal icing is what the faces of gingerbread men are decorated with. It’s white, shiny and hard, and does not need to be refrigerated. It’s used for decorations like dots and latticework.
This chocolate and heavy cream combination is very dark, and has the consistency of store-bought chocolate icing. It can be poured over cakes for a glass-like chocolate finish or used as filling (it stands up wonderfully between cake layers). Due to the ingredients, however, it’s unstable—don’t use it in hot or humid weather or the icing will slide right off the cake.
Delicious, but by far the most volatile, fresh whipped cream is usually not recommended for wedding cakes because they have to be out of the fridge for so long. If you really want to use it (it looks extremely white and fresh, which goes beautifully with real flowers) just keep it in the fridge until the very last second.
An Italian paste made of almonds, sugar and egg whites that is molded into flowers and fruits to decorate the cake. They’re usually brightly colored and very sugary. Marzipan can also be used as icing.
This paste, made from gelatin, cornstarch, and sugar, produces the world’s most realistic, edible fruit and flower decorations. Famous cake designers like Sylvia Weinstock are huge fans of gum paste. One nice benefit: these decorations last for centuries in storage.
Piping is ideal for icing decorations like dotted Swiss, basketweave, latticework, and shells. It comes out of a pastry bag fitted with different tips to create these different looks, which can range from simple polka dots to a layered weave that you’d swear is a wicker basket.
If you boil sugar, water, and corn syrup it becomes malleable and the most beautiful designs can be created. Roses and bows that have been made from pulled sugar look like silk or satin—they’re so smooth and shiny.
These hard little sugar balls are painted with edible gold or silver paint, and they look truly stunning on a big ol’ wedding cake.