I have a brand new, albeit smallish, ultrasonic cleaner that was gifted to me. I tried it for the first time yesterday with parts from a grandfather clock that I recently acquired. The water went black and the parts do look somewhat cleaner but not the sparkling brass that I see in everyone's posts after a sonic bath. Is this because the parts were extremely filthy? Would multiple baths eventually get them completely clean? Should I hit them with the old brasso before going into the bath to rid them of some of the years of grime? Thanks!