One of the things I tend to do here (which some surely dislike) is changing some micro-subjects to larger subjects (rarely smaller subjects - such as what maker of aftermarket pickups novices should put on their $130 pawn shop Chinese bass guitars with so-so necks, but whatever).
Broadening this topic,
The green that you see is copper verdigris mixed with hard scale. Hard scale is the real nemesis of brass instruments, and not so much loose dirt and scum (which certainly affect playing characteristics, but not the permanent welfare of the instrument).
Bathtub baths with Dawn detergent do not remove any hard scale, though they usually remove some of the dirt and scum (but often not in the knuckles between the valve casings - where the problematic dirt and scum - that which causes intermittent valve sticking, along with it being caused by hard scale deposits - actually hides).
Removing hard scale deposits safely (dissolving it);requires something safe, something acidic (not alkaline).
Personally, I don't view ultrasonic cleaning is particularly safe (though the equipment certainly is pricy - about the cost of a darn nice European made tuba), particularly if any dezinctfication has already occurred (as ultrasound has been known to blow holes in those weak spots).
My personal solution (to avoid the need for either ultrasound or static acid baths) is to (as I posted many times) generously drench the valve sections of my instruments with very inexpensive lamp oil (to lubricate but to also block the adherence of hard scale) before each time I play, and to jet fairly high velocity hot water through their valve sections (to remove loose dirt and scum, and with the main tuning slide removed) every few months. (This requires a rubber - not vinyl - hose, as the ends of vinyl hoses will come apart - usually scalding the person doing this
- when subjected to straight hot water tank heat. Obviously, a person must pay attention to avoid being scalded.)
@tofu
You can be annoyed with me for changing the subject, but just remember that I'm the one that did a near perfect job of straightening out your oem vintage 185 bell (which you seemed to judge as non-reparable) at no charge.
