I searched the group and found some references to cleaning very badly tarnished brass (in my case they are tubes for a carburetor, turned near black from a rough life I guess). Among the suggestions was ammonia and H2O, and vinegar and salt, ketchup, and a 2% nitric and H2O mix. In the shop the only thing I have from the above list is nitric, so I tried it.
I heated the water in a kettle, then poured it in a glass cup... added a splash of nitric and dropped in the brass tubes. It fizzled a bit, then after about 10 minutes or so, it was done the fizz. I added another splash of Nitric and bingo, that second bit really, really cranked up the results. These parts came out looking brand new... an outstanding before/after difference. I would estimate the first bit was at 3%, the second was at 7% or so... give or take..
This led me to a few questions. It seems the Nitric lost its punch after soaking the part in there for a bit? I am no chemist, so this may seem obvious to those in the know. Does a chemical reaction cause it to weaker as it gets working on cleaning the brass.
Because Nitric is kind of a pain in the butt to get, I was kind of hoping that I could have a little container of it that I could keep and just use it as I have parts to restore, then cap it off for the next time.... but from my experience today, I will have to neutralize and discard the batch after each round.
Any useful, positive info is very much appreciated!