Fondant refers to a type of decorative icing traditionally comprised of vegetable shortening, confectioner's sugar, gelatin, glycerine and water. Making fondant shiny requires a substance that will not saturate the preparation; hydrophobic compounds, such as vegetable oil, piping gel and the aforementioned glycerine all add sheen to fondant when applied after it sets. In addition to adding shine to cakes and decorations, these ingredients fill in small pores and cracks on the surface of the fondant and prevent drying from air contact.
Coat the fondant with a thin sheen of glycerine with a pastry brush after it sets. Glycerine, the same ingredient in fondant that helps prevent cracking and provides pliability, also restores or adds lustre to cakes that have dried or need increased shine.
Spray the fondant with a thin layer of vegetable oil-based cooking spray. Hold the can approximately 12 inches from the cake and coat the surface of the fondant using a back-and-forth sweeping motion. If possible, place the cake on a rotating cake stand and slowly spin it while spraying.
Apply a thin coating of clear piping gel to the fondant with a pastry brush. Although this method works on all fondant, small items, such as decorations, are well-suited to the technique; their small size allows for shorter application time.
Adjust the setting on a steam iron to "Steam." Test the iron away from the fondant to make sure it has no clogs and disperses evenly. Press the "Steam" button to disperse steam on the fondant while holding the iron approximately 3 inches away.