I get this colour change all the time and sometimes I get the silver
turning a black/blue colour if I leave it in the ultrasonic too long,
normal colour is restored by using a deoxadiser, Tickopur J80U is
what I use, I also get the problem of gold doing the same thing, I
mostly do 9ct repairs and some times after a clean in the ultrasonic
it comes out looking like 18ct? again deoxadiser usually works. I
have tried everything, different cleaning solutions in the tank,
altered the cleaner to water ratio, I have even tried using bottled
water but to no avail. Its just a problem I have come to live with
and as a result all repairs go into the Tickopur after the
ultrasonic. One thing I have found though, is that pieces with old
lead/tin solder joints or gold plated findings realy discolour and
contaminate the rest of the item, this can end up having to repolish,
clean by hand, and tumble the item to get it back to normal.
Getting ready for another wet Paddy's Day.