I’ve mentioned a time or two that I live in the scenic North Georgia Mountains. The town I live in has around 1,700 people, and not a whole lot else. Tourism is a big industry in my little town and the surrounding area, so many of the retail establishments we enjoy we owe to visitors. One of my family’s favorite places to go for pizza is in the town just north of us, Blue Ridge, GA. The name of the place is Blue Jeans Pizza and Pasta Factory.
Blue Jeans has an impressive brick oven where they cook the pies, and my kids love it especially because they can watch the pizzas being made. In addition to good food and sports on an enormous big screen projection television, Blue Jeans offers yet another opportunity to Think Thermally® while stuffing my face.
On one of our very first visits I inquired about the brick oven of which they seemed so proud. The manager informed me that they “precisely maintain” the temperature at 600°F. I didn’t want to get into a discussion of how precise the temperature was, I was curious about the general level of heat energy required to get my Meat Special just the way I like it.
So where’s our thermal lesson? Well let’s look at how they get the pie from concept to table. We watch the guy in the apron roll out the dough, stretching it, throwing it into the air (my kids especially like that part) and then onto the round screen. They add sauce, some cheese, a bunch of different meats, then some more cheese, and into the brick oven it goes, 600°F for 10-12 minutes, with a rotation about halfway through to ensure even doneness. Then out it comes, onto that shiny disc they use, they slice it and then bring it to me, piping hot and ready to eat.
So, I do what most of us do, I grab a slice and place it on my plate, and shake on some parmesan. Try as I might though, I can’t wait long before I have to have a bite. So I gingerly pick it up, firmly grasping the crust, using the index finger of my other hand to support the pointy end of the slice, and then carefully take a bite. Why carefully, you may ask? Like you don’t know; it’s hot! If I’m not careful I’ll burn my mouth. If I don’t bite through all the way and pull the slice away, the cheese and toppings will slide off and blister my chinny-chin-chin. Let’s be honest, it’s happened to the best of us.
But, I’m able to hold the crust just fine though without burning my fingers. The crust went into the oven at the same time as the rest of the pie, why doesn’t it burn my fingers? Are my fingers hotter than the inside of my mouth? No, probably not. The difference is thermal capacitance. Simplified, thermal capacitance is a measure of a material’s ability to store heat. Water has 3,500 times the thermal capacitance of air. If I have a cubic foot of air and a cubic foot of water at the same temperature, there are more units of heat energy in the cubic foot of water than the cubic foot of air.
How does this apply to my slice of pizza? The crust is full of air. The dough rises as it cooks, there are pores in the crust, and the pores are full of air. The sauce has a high moisture content, a greater ability to store energy. So, when the whole pizza is pulled from our 600°F brick oven, the crust at the edges cools more quickly than the sauce does, so it won’t burn my fingers when I pick it, whereas the sauce will burn my lips, tongue, chin (or whatever else) if I’m not careful.
There’s thermal magic everywhere we look, even when we’re kicking back watching The Braves and eating pizza. Keep Thinking Thermally!