First of all, wood will not "torch off" at 380 F. Secondly the aluminum foil wrap keeps air from contacting the wood surface, so it can't, anyway. There seems to be some misunderstandings and confusion concerning various process of "heat treating" wood. I don't believe any of the processes use a vacuum. I do not know the details of the patented "Torrefaction" process, other than it was originally used as an alternative to chemical treatment for wood preservation, primarily at higher temperatures than most guitar wood is treated.
The patented "Thermowood" process was developed in Finland, originally for the same purpose. This is the process that my wood (other than the guitar sides) has gone through, and is the same process being used by several major instrument manufacturers, such as Fender, Gibson, and Music Man, to name a few. In fact, my wood has been on the same pallet as some of their's. This process heats wood to 180 C with no attempt to create a vacuum or introduce an inert atmosphere. Actually there is a slight positive pressure, about the equivalent to a breath of air, in the kiln
To my knowledge, there are currently 2 such kilns (manufactured by Jarvis) in operation in the United States, one here in northern Minnesota, and the other in Indiana. I am very familiar with the Minnesota operation. Just for grins, here is the inside of a Thermowood kiln looking out
And here is a pallet of my wood, mostly spruce tops with a few back billets and some 12/4 HOG for necks, just out of the kiln
The top 4 layers are somebody else's electric guitar bodies.
As I said, I treated my sides in a conventional oven after bending because the treated wood is almost impossible to bend. I first discussed this with the guy who operates the Thermowood facility and showed him a couple of samples. He said I was ending up with essentially the same thing. This works because the bent side has already been set into a shape by the bending process. I expect that a flat back plate would turn into a potatoe chip
Grant