Good Morning Joe,
I've used battery acid before and it does work well, you get a very defined etch. As for the acid that was used in the pics, I mentioned in the text above the pics that I was using Nitric Acid...but the battery acid worked well for me, took a bit longer, but it gave a defined etch.
Does the battery acid cost $35 now?....geez, that stuff has really gone up, I don't remember it costing anywhere near that.
Ok, I just called Fisher Auto Parts and they have a 1.5 gallon container of undilluted battery for $13, and $20-something for a 5 gallon bucket. This is the same stuff that comes with a new "dry" battery and you add to it to get the battery going. Same stuff that I've used before and it works. It has to be strong enough to eat lead so that the battery will work as a battery and not a door stop.
I certainly don't want to mis-lead anyone...it has worked for me.