Fondant is a smooth sugar paste coating added to give cakes a finished look. Perfectly prepared fondant has a shiny appearance once it dries, but if your fondant looks dull, you can save it. The secret to salvaging fondant with a matt finish is glycerine and oil. Glycerine is available in baking supply stores, and the oil is right at your fingertips.
Wash and dry your hands carefully. Rub your bare hands over the fondant-covered cake. Oil from your hands will add shine to the fondant on the cake, according to "The Cake Bible."
Dip the paintbrush into glycerine.
Apply a thin, even layer of glycerine to completely cover the dried fondant to add shine.
Glycerine is made from oils and other fats. This edible product is an ingredient in some fondant recipes to ensure that the finished fondant is shiny, but it can also be added to a cake after applying the fondant without changing the flavour of the dessert.