Too Hard: In cold weather, fondant can be harder to knead, but it?s certainly still usable. Simply knead it longer to make it pliable. It can also be very hard to knead fondant if it is too dry. When fondant is dry, it may also appear crumbly. To add moisture, knead in a few drops of water. Start by adding about ? teaspoon of water to a 24-ounce package. Knead, adding more as needed.