Caramel can crystallize if sugar crystals form during the cooking process. Here are some tips to prevent crystallization and ensure a smooth caramel: 1. Use a clean, dry pot or saucepan to cook the sugar. Any water droplets or residue can cause the sugar to crystallize. 2. Avoid stirring the sugar mixture too much once it begins to boil. Stirring can introduce air bubbles that can cause the sugar to crystallize. 3. Use a candy thermometer to monitor the temperature of the sugar mixture. The sugar should reach a temperature of 320-350°F (160-177°C) to create a caramel without crystallization. 4. If you notice any sugar crystals forming on the sides of the pan, use a pastry brush dipped in water to wash down the sides of the pan. This will dissolve any sugar crystals and prevent them from falling into the sauce.