I’ve had a Weber pizza stone for some time now and have spent some time trying to perfect pizza baking on my 47cm Weber kettle BBQ. I often found that my pizzas weren’t cooking all the way through or that the base was a little soggy despite the top being cooked. This, in addition to the fact that the baking process was actually taking significantly longer than the 11-or-so minutes that I was expecting it to take. All of this has suggested that the BBQ was never getting hot enough.
I have done what I can to try and ensure that the temperature in my 47cm Weber was as high as possible, including using a chimney starter and ensuring all coals are burning prior to being placed in the BBQ. In addition, I have placed the stone in place for the recommended 10 minutes prior to placing a pizza on.
A friend of mine recently suggested propping the lid on the Weber open in order to increase the amount of oxygen available to the BBQ. The first time I did this, the resulting pizza was very well cooked (slightly over-done on the base) in 12 minutes of cooking. This was something of a revelation, seeming slightly counter-intuitive. Doing this since has resulted in much better results.
The greatest issue with the kettle BBQ is that it does not feature a thermometer. There are a number of online guides on the subject of adding a thermometer to the lid of the BBQ, but without one, it is very difficult to know exactly what is going on. Adding a thermometer risks causing damage to the enamel paintwork, which in-turn risks rust, etc.