Well, maybe. I'll ask him. But, what he built is of a tradition of stone / brick construction with precise propotions, etc. What he does is build a fire in the thing and heat it up. Takes quite a while. Then, he cleans out the coals and bakes. The thing holds heat for a long time to do the baking.
As I said- a true piece of work. Even better, he has battled the city for years to comply with codes. Just keeps on keeping on.