Q: After I polish a piece of jewelry, I wash it by hand with hot water and dishwashing soap, then I’ll throw it in the ultrasonic cleaner, and even after that it still has residues from the polishing compounds. What can I do to get this stuff off?
A: First, I’d suggest skipping the manual wash. It’s easy to accidentally scratch a finely polished piece that way, and if the ultrasonic is having trouble, hand washing won’t have done much good.
Is the ultrasonic solution hot? If not, heat it—it should be just too hot to comfortably touch. If this sonic cleaner isn’t a nice unit with built-in heat, it’s possible to use a small cheap immersion heater, the kind sold in 5 and dime stores for a couple of bucks, intended to boil a cup of tea in a hotel room. One can rig one of those up to sit in the corner of an unheated ultrasonic to give the rig a heater for a whole lot less than the built-in ones cost, and they last pretty well. I usually got a year out of each of them before they’d die, until I finally bought a better cleaner.
Then, if the cleaning solution isn’t concentrated enough, one can always try mixing it up a little stronger, or if it is not ammoniated, and is safe to mix with ammonia (always check first—never mix chlorine compounds with ammonia), adding some can help. Also, if 5 to 8 minutes isn’t doing it, try leaving it in longer. Some of the less expensive cleaners can take quite a while to break down some of those residues. If you can afford a steam cleaner, by all means, get one. The combination of the steamer and the sonic cleaner is far more effective than either one alone.
And here’s another thought. Long before we had fancy ultrasonics or expensive high pressure steam cleaners, jewelers cleaned out that gunk with a “boil-out” pot. Even today, many jewelry shops have one going in addition to the sonic and steamer. Some polishers prefer it. It is simply a saucepan or pyrex beaker on a hotplate or gas burner, just barely boiling, containing a strong solution of TSP cleaner. Leave a piece simmering in there for a half hour, and I’d be very surprised if any polish compound was left. The key parts here are the strongly alkaline cleaner, since polish compounds are grease and wax based, and the boiling temperature. Lower temps don’t do it anywhere near as well, if at all. The boiling temp is what really loosens those wax and grease binders, allowing the solution to dissolve them away.