Icing the Cake
Achieving a perfectly smooth iced cake, while keeping crumbs out of the icing, is tricky but can be accomplished by following some basic steps.
Start by positioning the cake on a serving board then place on a cake decorating turntable. Use icing thinned with 3 to 4 tablespoons of corn syrup so it spreads easier or use Crusting Buttercream icing.
The key to keeping crumbs out of your icing is to never allow the spatula to touch the cake surface or to pull already spread icing from the cake surface.
You can also "crumb coat" your cake by lightly icing the cake first, placing the cake in the refrigerator or allowing a light crust to form, to seal in the crumbs before icing the cake.
Applying your icing with a Cake Icing Tip
Using a Cake Icing Tip and large Featherweight bag is the highly recommended to prevent crumbs getting into your icing.
Using a 16" Featherweight bag and tip 789 (Icer Tip) fill the bag half full with icing. Hold the bag at a 45° angle and lightly press the tip against cake. Starting in the center of the cake, squeeze a ribbon of icing in a continuous spiral motion to cover cake top, with last ribbon of icing over the edge of the cake top.
Start at the bottom of the cake to ice the sides. Using your turntable, squeeze the icing as you turn the cake slowly. Repeat until the entire cake side is covered.
Applying your icing with a spatula
Place a large amount of thin consistency icing on the center of the cake top. Using a spatula held at a 45° angle, spread the icing across the top, pushing toward the edges.
Spread the icing across the top, pushing the excess icing down onto the sides of the cake. Build up enough icing in front of the spatula to prevent pulling up crumbs.
Place a large amount of icing on your spatula and cover a section of the side of the cake at a time. Slide the spatula off from the side of the cake. Repeat until the side of the cake is covered.
Smoothing the icing
Smooth the sides first by holding the spatula upright with the edge of the spatula held at a 45° angle against the side of the cake. Slowly spin your decorating turntable without lifting the spatula from the side of the cake. Remove the excess icing from the spatula and repeat until the sides are smooth. Always check your excess icing for crumbs. If you see crumbs throw the excess icing away to prevent the crumbs returning to the cake.
Level the icing on top of the cake with the edge of your spatula.
Smooth the top using the edge of the spatula held on a 45° angle. Sweep the edge of the spatula from the rim of the cake to the center. Then slide the spatula off and remove any excess icing from the spatula. Rotate the cake slightly and repeat this procedure, starting from a new point on the rim until you have covered the entire top surface.
Finishing the icing
If you are using a Crusting Buttercream icing. Let the cake sit for 15 tp 20 minutes. Place a sheet of Viva paper towel on top of the cake. Smooth the top of the cake using your hands or fondant smoother, then smooth the sides of the cake. Repeat until the entire cake is smooth.
If you are using a non-crusting icing, it may help to dip the spatula in hot water, wipe dry, and glide the hot spatula across the entire surface. Repeat until smooth.