Pizza Physics: Why Brick Ovens Bake The Perfect Italian-Style Pie
The ideal Italian pizza, be it Neapolitan or Roman, has a crisp crust flecked with dark spots — marks left by a blazing hot oven. The dough is fluffy, moist and stretchy, and the toppings are piping hot. A pizzeria's brick oven pops these out to perfection, but intrepid home cooks attempting to re-create Italian-style pizzas have more than likely discovered facsimiles are nigh impossible to produce.
"Even if you prepare [the pizza] the same way, you cannot get the same result with just your oven at home," says Andreas Glatz, a physicist at Northern Illinois University and pizza enthusiast.
The fact that you need a vaulted brick oven to bake a great Italian-style pizza is well-known, but Glatz and Andrey Varlamov, also a pizza-eater and physicist at the Institute of Superconductors, Oxides and Other Innovative Materials and Devices in Rome, wanted to know why. The secret behind a pizzeria's magic, they concluded in a paper published on arXiv.org last month, is in some unique thermal properties of the brick oven.
They started off interviewing pizzaiolos, or pizza makers, in Rome who were masters of the Roman style of pizza. For this, the bake lasts 2 minutes at 626 degrees Fahrenheit. (Neapolitan pizzas usually bake at an even higher temperature — at least 700 degrees.) That turns out a "well-baked but still moist dough and well-cooked toppings," Glatz says. The same settings in a conventional steel oven produce far less ideal results. "You burn the dough before the surface of the pizza even reaches boiling, so this is not a product you will want to eat," he says.
Brick versus steel
Chewing this over, the physicists realized the key difference lies in how much more slowly brick transfers heat to the dough compared with steel — a measure known as the material's thermal conductivity. A brick oven heated to 626 degrees will heat the crust to roughly 392 degrees, while the pizza top receives indirect heat from the oven and stays at 212 degrees as water boils off from the cheese and tomato sauce. Glatz says that after about two minutes, both the pizza top and crust reach perfection.
But pizza crust in contact with a steel oven at the same temperature will hit 572 degrees because the metal transfers heat far more rapidly than brick. That's much too high for dough, Glatz says, "so it simply burns." Unfortunately, because the top of the pizza must cook as well, simply lowering the oven temperature to 450 degrees doesn't work. While that will heat the crust to 392 degrees, the rest of the pizza won't receive enough heat to boil by the time the crust has cooked — resulting in cooked dough but undercooked toppings.
Home chefs could deploy a ceramic pizza stone in home ovens — which would work if home ovens could reach temperatures as high as 626 degrees. "But most electric ovens cannot get to those temperatures," Gatz says. Even at 550 degrees, the upper limit for many home ovens, the longer required bake time from the lower temperature will dry out your pizza. What's more, Gatz has still colder news for home cooks: "If you want the flavors of the smoke and the wood and the dry heat of a brick oven, there's no good emulation for this effect."
Switch up your style
"No matter what you do, a home oven is not going to deliver absolutely perfect Neapolitan pizza," he says. "I would honestly choose a style of pizza that doesn't require an extremely hot oven. Maybe more of a New York-style pizza." New York-style pizzas typically have dough with more fat — extra oil will help keep the dough "nice and tender" during a longer bake time, Lopez-Alt says.
Still, home cooks should not despair, Lopez-Alt notes. "You can get pretty close [to a Neapolitan pizza.]" Gatz and Varlamov's paper was right that a home oven doesn't reach the right temperatures, he says. "But they do have broilers."
Preheating a steel surface — like a pan or, possibly, the oven floor — in the oven to around 430 degrees will quickly cook the pizza crust, while the broiler would expose the toppings to direct heat and fast cooking.
"Steel at 500 degrees can burn the pizza in 60 to 90 seconds, so you want to be careful about that," Lopez-Alt says. "If the bottom is going to burn, pick it up and let it finish under the broiler." That should create a well-baked crust and finished toppings without drying out the pizza, he says. "It won't be exactly the same" as a Neapolitan pizza.
But it'll still be pretty good.