So I tried cleaning out a few junker horns with a diluted mix of CLR because I read somewhere that would work. One of the horns is in raw brass, the other in very shoddy lacquer. I even cleaned a silverplate sousaphone neck just to see what would happen there. I was pretty pleased with the cleaning action, especially on the valves, but I got a reddish rose color in quite a few places, especially on the raw brass horn. I let it soak for about 20 minutes and then I rinsed it. On the semi-lacquered horn, the only place I got the red color was right on the mouthpiece receiver, but I only let it soak for about 10 minutes. On the sousaphone neck, I got a little on the raw part that would insert into the instrument, again soaking for about 10 minutes. So my questions are: Did I create a problem that wasn't already there? (All these instruments were at least 10 years old and were beginner student instruments - so never really taken care of). If I did create a problem, is there a way to fix it? If I didn't create it, and the problem was already there, is there a way to chem clean your instrument without exacerbating the problem? Did I get more red rot on the raw horn because I let it soak longer or because it is raw?