Water spots are usually dark - and darker than the rest of the patina all the way down to the untarnished brass. The best you can hope for is to keep your cleaning down to a small area so it's to leave most of the surrounding patina in place. 800 grit sandpaper with valve oil on it can be controlled pretty well, or a pencil eraser will take longer but might be easier to control - as far as keeping the area small. If you're looking towards a perfectly even patina as a "finish", that's a pretty tall order. All of those fake patinas that they put on saxophones (mostly, and sometimes on other instruments) are irregular by design, so that they look real.
I'm sure you can imagine yourself playing the instrument some outdoor concert where rain wasn't predicted and then a little bit of sprinkling begins to occur. What then?
Cleaning and polishing brass are - pretty much - synonymous.
These two...??
neither engineered nor designed, but existential.
(The one on the right was never "stripped", other than via use, and thanks to the crappy-seemingly-about-the-quality-of-1982-2nd-world-country-rattle-can factory lacquer.)
Continuously reminded of the cartoon of the old fat man holding his dull tuba and imagining himself as a young handsome man with a shiny tuba, I HOPE to somehow carve out time put a lacquer finish on both of these...
I'm thinking that a fat old man with a shiny tuba looks better - on stage, and a fat old man with an old brown tuba...and nearly all people hear with their eyes.
' silver plating...??
nope. I prefer shiny to smeary-grey/black.
