The difference in texture between the soft and spongy side of the pizza crust and the crispy and crunchy side is typically the result of how the pizza is cooked and the distribution of heat during the baking process. This effect is most prominent when using traditional pizza ovens, but it can also occur to some extent in home ovens.
Here's how it happens:
Cooking Method: In traditional pizza ovens, the pizza is placed directly on the hot oven floor or a pizza stone. This means that the bottom of the pizza, which is in direct contact with the hot surface, gets exposed to intense and direct heat. As a result, it cooks quickly, creating a crispy and crunchy crust.
Oven Temperature: Traditional pizza ovens are usually much hotter than home ovens, reaching temperatures of 700°F (370°C) or even higher. The high heat helps to rapidly cook the crust, leading to the crispiness on one side.
Air Circulation: In a pizza oven, the hot air circulates evenly around the pizza, ensuring that the toppings and the top of the crust get cooked thoroughly. However, the airflow is not as prominent on the bottom side because it's in direct contact with the oven floor. This can lead to the creation of a softer and spongier crust on that side.
Cheese and Toppings: The layer of cheese and toppings on the pizza acts as a barrier, trapping steam and moisture during the baking process. This can contribute to a softer crust on the side facing up.
In home ovens, you can still achieve a degree of softness on one side and crispiness on the other by using a pizza stone or a preheated baking sheet placed on the oven's lowest rack. Preheating the baking surface helps mimic the direct heat from traditional pizza ovens, which can result in a crisper bottom crust.
In summary, the soft and spongy side of the pizza crust is typically the top side, which doesn't receive direct heat, while the crispy and crunchy side is the bottom, directly exposed to intense heat from the oven floor or a pizza stone. The combination of oven temperature, direct heat, and air circulation during the baking process contributes to this textural difference in the pizza crust.