Why does the caramel topping on sticky buns sometimes come out smooth and other times it is crystalized?

Crystallization is the process by which a solute in a solution forms solid crystals. Several factors can affect the crystallization of caramel, including:

- The temperature of the caramel: Caramel is made by heating sugar until it melts and turns brown. If the caramel is heated too high, it can become over-cooked and start to crystallize.

- The concentration of the sugar in the caramel: If there is too much sugar in the caramel, it can become supersaturated and start to crystallize.

- The presence of impurities: Impurities, such as dust or dirt, can provide nucleation sites for the sugar crystals to form on.

- The cooling rate of the caramel: If the caramel is cooled too quickly, it can trap microscopic sugar crystals that can act as nucleation sites for further crystallization.

To avoid crystallization, it is essential to:

- Use a candy thermometer to ensure that the caramel is cooked to the correct temperature.

- Stir the caramel constantly while it is cooking to prevent the sugar from sticking to the pan and burning.

- Add a small amount of corn syrup or cream of tartar to the caramel to help prevent crystallization.

- Cover the caramel with plastic wrap while it is cooling to prevent it from drying out and crystallizing.