The great part about bluing and patina acids are if you don’t like the results you can scrub it off with white scotch bright pads in a matter of minutes and start over.

I feel a tube frame is a good idea, however it would be overkill for an interior door. Perhaps flat stock on edge/perpendicular to frame the door sheet metal. Pending the thickness of the door place layer(s) of sheet rock inside the cavity and weld the other sheet metal skin to capture/encapsulate ...

Take a look at the patina acids. They never disappoint.

I feel a tube frame is a good idea, however it would be overkill for an interior door. Perhaps flat stock on edge/perpendicular to frame the door sheet metal. Pending the thickness of the door place layer(s) of sheet rock inside the cavity and weld the other sheet metal skin to capture/encapsulate i...

You pretty much nailed it. Magnetic polarity from the magnet interfering with the active magnetic field of the arc.

If it works, yes $320 is a great deal for an AC/DC machine.