White stains on silver after ultrasonic

Hi everyone,

I have a small sterling silver jewelry production line and I've been encountering a problem with the ultrasonic.
After I use the ultrasonic to clean the pieces I would find sometimes some white haze on the pieces that wouldn't go off without polishing again. This happens for the most part with flat designs but can happen with others as well though will be less visible.
This happens to the pieces after the polish or even if I just get the pieces engraved by laser and need to remove the burn marks. So I don't think it has to do with the polishing compounds.

I use an ultrasonic machine with the water aimed at 80 degrees C and an ultrasonic compound in the water to clean it even further.

I tried to change through a few compounds in order to see if that was the reason and so far all of them presented the same problem.

Is anyone else encountering the same problem or found a solution to minimize it from happening?

Possible causes off the top of my head -
Parts impinging on each other or the body of the ultrasonic;
cavitation caused by the ultrasonic (too long in the tank will exacerbate it as will not degassing the cleaning solution);
mineral precipitation - you're running quite hot, so there's a fair chance.
I suppose there's a chance it could be electrochemical in nature, depends what else is in the tank with the jewellery.

I don't remember the water in Thailand being particularly hard, but it's possibly worth checking your process and ensuring you use distilled or deionised water and degas it. I'd work at a lower temperature too.

Failing that - contact the ultrasonic manufacturer and ask them what is going on.

Thank you for the quick reply.
I guess I could've given more information, Sorry about that.

I put the parts on a rack made from a wire so they are well separated and are away from the body of the machine.
The only thing in the tank besides the parts is the wire but this also occurred if I used a pair of tweezers with a rubber cover.
The water in the tank are distilled water and I've experimented with different temperatures going from 30 up to 80 and that had no effect.

I will contact the manufacturer and see what they can suggest. If there's anything else that comes to mind I'd appreciate it.
Thank you.

Hi,

I experienced similar spots on my sterling silver pieces few days ago. Was browsing in this forum for information... So I am just curious If the manufacturer had some suggestions in this situation?

Thanks!

I have been experiencing the same problem I now only use it as a bath with a toothbrush

I remember when I turned ultrasonic on for ~5 minutes it was OK. Last time I decided to wash my pieces very well and washed them for ~13-15 minutes and then white spots appeared. I guess one of the reasons can be duration (because everything else was the same, the temperature, the shampoo and etc) and more than 10 minutes is too much and not necessary.

Another interesting fact, that two rings turned to matte finish (while they were slightly polished with brass brush on flex shaft motor) only on the outside, they looked like they were took out straight from pickle. :(