Light whipping cream is between 30 and 35 percent milk fat, and can also be whipped. White sugar and superfine sugar can be substituted cup for cup. Confectioners' sugar, also known as powdered sugar or icing sugar, is the very fine powdery sugar used in frostings and many candies or to dust the top of your favorite cake. There could be a couple of problems when candy doesn't set up properly. If the air is too humid, candy can turn out too soft or have that gooey sheen on its surface.
Candy needs to be made on a dry day.
You also need to be sure your pans, bowls and utensils are clean and dry before you begin. Moisture in bowls can affect whether candy gets firm, and flecks of sugar or other particles can affect the way it crystallizes. The other problem arises when candy isn't cooked to the proper temperature. Use a candy thermometer for best results, and be sure to cook your candy to the proper stage. For more about candymaking, read Visions of Sugar Plums in our Cooking Basics section.