I've been Ultrasonic cleaning brass cases for only a few months, but have started getting some odd results.
I made a solution of distilled water and cirtic acid obtained from a wine making store. Results were fantastic!
I filter the solution after a few uses by pouring it through paper towel in a funnel, then letting the liquid sit for a day or more. It gets a thick black precipitate on the bottom. I pour off the clearer liquid and use it for cleaning, and this has been working quite well for a few months.
The last few weeks when I cleaned my .45 cases, they come out multi-colored brass. I use Tarn-X to remove this coloring. The odd thing is my .38 brass still comes perfectly fine from the exact same solution. The cases are mostly Federal brass, but contain others as well.
So, is the solution just wearing out, or what???