Keep frosting covered with a damp cloth until ready to pipe the frosting or spread it.
To store: For best results, do not leave sitting at room temperature for too long and store the mixture in the refrigerator when not in use. The mixture can be kept refrigerated in an airtight container for up to 2 weeks. Be sure to re-whip the mixture thoroughly before using.
Whether you are frosting a cake or piping decorations, the consistency of the frosting is key to getting the right results. Too soft and your decorations will droop. Too stiff and your frosting will be difficult to spread.
Preparing a perfectly smooth iced cake, while keeping crumbs out of the icing can seem like a tricky thing— but over the years we've developed some methods to make it easier. Start by positioning the cake on its serving board on the turntable. Remember to thin the icing with 3-4 Tablespoons of corn syrup so it spreads easier. The trick to keeping crumbs out of your icing is to glide your spatula over the icing, never allowing the spatula to touch the cake surface or to pull already spread icing from the cake surface. Some decorators prefer to "crumb coat" layers by lightly icing the cake first, allowing a light crust to form, then adding a top icing cover.