Google was not very helpful. It showed:
and
I searched his channel for "alum" and did not see anything else.
He made a video like the first one?
I am trying to find someone else dissolving broken bits with alum and I keep finding broken bolts in aluminum blocks, etc.
I stumbled across this, but videos are not loading right now:
I watched a couple of videos by this guy. I like how he drills a hole down a middle of a bolt and uses that to drill a starter hole in the middle of a broken bolt without risking damaging the threads:
He used a left-handed drill bit in a hinge drill kit to also make sure he did not damage the bolt hole.