I developed this system just for something quick and easy for my students to set up, but like it so much it's all I use outside of my larger charcoal set up. I have a couple more expensive stainless steel burners and an electric furnace that I don't even use anymore...
You can create reducing atmosphere inside the muffle by putting a piece of wood in at in the back. I also use a splint in the outer chamber to shield the muffle itself. The muffle is a little extra long and sticks out the back to make room for the wood chunk inside. If done right, all you get is a little patina, but no scale or decarb.
The refractory is so efficient that the cans never get hot. It's also such a nice light weight refractory that it heats up and cools down in seconds. So, you can turn it down between heats to save gas, although it's very efficient even with out doing that. It's nice to be able to bump the heat up or down so easy in general. It’s almost as “responsive” as a solid fuel forge.
I can forge about any size blade in it, but it is limited in size for heat treating. 4-5 inches
is about it for HT... good for EDCs though.
You can get another inch or so out of it if you pump the blade, but I don't like doing that too much. I just want to let it sit and soak.
Here's a few pieces that were forged and heat treaed with the weed burner rig.