When I worked in a music store, we had a really big one in the repair shop. You could fit a tuba in it! I think they used a very dilute solution of Simple Green and a pretty strong acid (can't remember if it was sulphuric acid or HCl) It did wonders and we didn't leave stuff in there for more than 5-6 minutes. Whatever the solution was, it would turn some metals pink. One of the guys in the repair shop let a friend of his bring his gun in to clean it in there and it turned pink. I know raw brass would usually turn pink if left for too long.

But, yes, these things are great! The bigger they are, the noisier they get.