The physics of perfect pizza

A Russian physicist living in Rome has analysed pizza-making and found why wood ovens are superior to electric ones: they give the perfect balance of well-cooked base and browned toppings.

Andrey Varlamov researches superconductivity at Italy’s Consiglio Nazionale della Ricerche (CRN). One day, he struck up a conversation with the pizzaiolos (pizza-makers) at his local café about the niceties of oven temperature. He was inspired to analyse heat flow between the brick base of the oven and pizza dough.

In doing so, he enlisted the help of materials scientist Andreas Glatz of the US Argonne National Laboratory, and Italian food anthropologist Sergio Grasso. Their findings, currently awaiting peer review on the pre-print site Arxiv, reveal why Italians insist on cafes with wood-fired ovens.

“I succeeded in explaining for myself Italian traditional behaviour,” Varlomov says. “It’s not just conservatism, it is the experience of hundreds of generations.”

The key, he and his colleagues found, was getting the correct balance of heat flowing into the base of the pizza via conduction from the bricks below, while using radiant heat to warm the toppings.{%recommended 4554%}

The local pizzaiolos divulged to Varlamov that the magic formula in the wood-fired oven was two minutes at 330 degrees Celsius. He calculated that in this scenario the temperature where the dough touched the bricks would be 210 degrees.

Varlamov then repeated the calculation for an electric oven, made of steel, and found that because of the higher thermal conductivity of the metal the temperature under the pizza would be much higher, around 300 degrees.

“That is too much! The pizza will just turn to coal!” Varlomov writes in the paper.

To achieve the perfect under-dough temperature, the electric oven needs to be reduced to 230 degrees. The problem is that the lower ambient temperature means there is now less radiation to cook the toppings. 

The amount of radiant heat emitted is subject to what physicists call the Stefan-Boltzman Law, which describes its proportionate relationship to the absolute temperature of any particular body.

The 100 degree drop in electric oven temperature thus, Varlamov and colleagues calculate, reduces the radiation by half. This means that the toppings will need double the cooking time, compared to that required in a wood-fired oven, and still will not have the authentic taste.

“You need the radiation from above, because it should be crisp,” the researchers write, while noting that electric ovens also change the sensory properties of pizza toppings in not altogether happy ways that wood-fired cookers don’t.

Varlamov’s study in Rome is ongoing. He is also researching the cooking of pasta, and the making of coffee. He cites “love” as one of the main motivations for Italian baristas to create great coffee for 70 cents. In contrast, Parisians use the same types of Italian-made coffee machines, and charge five euros for a cup of “liquid shit”. 

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