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Slice Tests the Kettle Pizza Grill Insert
The Kettle Pizza grill insert promises to help you turn your 22-inch Weber kettle grill into a fire-breathing pizza-cooking machine.
Why would you even need this thing and what does it do? Those seemed to be the questions everyone at the test-grilling last night had. Even though Mmmph beat us to the punch on testing his, we wanted to try it the way the manufacturer intended it before maxing out the heat the way Mmmph did.
OK. There are a couple schools of thought on cooking pizza on the grill. One is to simply grill the dough directly on the grate. We deal with grilled pizza here, and in fact it's our preferred method anytime the words "grill" and "pizza" wind up in the same sentence.
But whenever we mention grilled pizza on Slice, a fair amount of people drop by and say that they like to use a pizza stone on their grills. The issue we've always found with that method is, well, let me poke Kenji here and see if he'll drop some science on us ...
The Heat Is On
Frequent Slice readers may know this already, but for those who don't, a Neapolitan pizza cooks via two modes of heat transfer: The bottom of the pizza is cooked by conduction, the direct transfer of energy from the stone to the crust. The top of the pizza is cooked via convection, the transfer of energy via hot air.
Conduction is a much more efficient method of heat transfer, which is why in a professional oven, to cook a pizza properly, the base of the oven need only be around 750°F or so, while the air above must be significantly hotter—in the 1,000°F to 1,200°F range.
The problem with trying to cook a pizza on a stone in a regular kettle grill is that, as many people have pointed out, the stone gets really hot, and it's hard to get the air temp above the pizza hot enough to match it. The bottom of the pizza burns before the top takes on any color. You might think that raising the lid higher and adding an opening would have the opposite of the desired effect, lowering the temperature inside the oven and making the top cook even less efficiently, but this is not the case. The important thing to remember is that moving air cooks a lot more efficiently than still air (think: convection mode in an oven vs. standard mode. The only difference is a fan circulating the air).
So really, the goal when cooking a pizza on the grill should be to get as much hot air circulating over the top surface of the pizza as fast as possible.
The main advantage that I see to using the Kettle Pizza insert is that when you get the fire and positioning of the stone right, it creates good convection currents. With the coals banked in the back, hot air rises off the coals toward the domed lid, then gets pulled back down and out the oven door opening. This moving air cooks the top of the pizza a lot faster than the relatively still air inside a completely sealed kettle.
The trouble we had was getting the temperature hot enough—we went through nearly 30 pounds of coal before we hit a sweet spot—but once we were there, the grill maintained its temperature at well over 700°F for a good 45 minutes (with a stone temperature of around 550°F). At about 3 to 4 minutes per pie, that was long enough to crank out 8 pies in rapid succession and feed an equal number of hungry guests. After the pizzas were done, the coals were still hot enough to fire up an addtional 8 Chili Cheeseburgers and a couple of red-chile marinated skirt steaks. —Kenji
Thanks, Kenji! That makes perfect sense. Now, the low-down on how this thing worked ...
As Kenji said, this thing does appear to give some added benefit to your pizza cooking but does so at the cost of an enormous amount of fuel. It is sometimes a chore to keep the thing stoked. Our advice is to start with 3 to 3.5 chimneys' worth of charcoal if you want to achieve the temperatures this thing needs to work.
It's also imperative that you use the two-zone indirect fire that the manufacturer recommends. This ensures that you do not overheat the stone and cook the bottom of the pizza too quickly. (We tried an all-over coal placement and found that pizza bottoms cooked too fast that way.)
We also recommend cooking on a stone rather than a pan. Using the pan, we also found that the pizza bottom cooked too fast.
Do we recommend it? At $80 (about $105 after S&H) it is not the most expensive pizza-cooking gadget we've come across. My inclination would be as it always is -- just grill the pizza right on the grate.
But if you are looking for a Neapolitan-type crust and want a moderate edge over what a home oven can do for you, this might not be a bad option — as long as you understand its limitations and how to compensate for them.
Next up ... we want to get our hands on a Pizza Forge.