Gum paste, also called pastillage, is a malleable, edible material for making cake decorations that dry to a brittle crispness. When shaping the gum paste, it should mold easily without breaking. Finding out why your gum paste cracks will be the first step to repairing the paste and avoiding future recipes of gum paste from cracking.
Too Much Sugar
Adding too much powdered sugar to the gum paste when making it from scratch will dry out the paste and cause it to crack. Add water 1 tsp. at a time to the paste and knead it until it becomes pliable enough to roll or shape. Stop adding water if the paste becomes sticky and knead 1 tsp. of powdered sugar into the paste to absorb the excess water.
Gum paste dries quickly when exposed to air. Trying to mold slightly dried gum paste will result in it cracking. Soften hardened gum paste by warming it. Microwave slightly hardened gum paste for 10 to 15 seconds on high power in the microwave to soften it. Knead the softened gum paste in your hands to make it more pliable for molding and prevent cracking again.
Preventing Drying During Storage
To keep gum paste from drying out too much in storage, keep it wrapped in at least two layers of plastic wrap to provide a double-layer barrier to the air. Place a damp towel on top of the plastic-wrapped gum paste to create a humid environment around the gum paste, which further prevents drying. Keep the towel-covered gum paste sealed in an airtight container at room temperature for up to one year.
When making shapes with gum paste, you must keep them supported until they dry. Without a support structure, the weight of the gum paste could cause the shaped portion to bend until it cracks and breaks off. Insert damp paper towels through loops for bows or under the curved edges of flower petals. Leave the gum paste shape untouched until it dries completely.