I've been using the recommended mix of Simple Green and water in my new ultrasonic cleaner. This worked well on parts and a recently inherited Ortgies pistol. There were a number of suggestion to add Lemi Shine to the mix, so today I did and cleaned a Walther PP I got at an auction yesterday.
The bluing on the frame was completely removed and the bluing on the slide is dull and mottled.
Since there was not bluing damage to the Ortgies, I'm going to say that the addition of the Lemi Shine to the Simple Green mixture is responsible for this rather expensive lesson.
Cheers(?),
Richard