I wish I could tell you. I suspect if it was water only it might be OK. I can say with confidence that alcohol and a cotton swab absolutely doesn't work.

 

No, don't do that or you may very well end up with a bare brass dial.

 

Agreed, that's a bad idea. My ultrasonic cleaner was able to cause the PVD coating on my glasses to flake off, and the paint or lacquer on a dial is much more delicate.

 

I'm no expert but from what I've read I would definitely not use any alcohol or anything too harsh, there is lot of delicate areas on most dials...decals, writing, lume etc... and all these will react differently to whatever you use to clean it with.

Your best bet would be to use only water, sparingly, and something soft to brush and wipe with. It's all trial and error and you have to take care around the delicate areas I mentioned.

It's all very risky and you have to start small and go slow. Most importantly be very very careful.

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Thanks for the help!

 

I would not put a dial in an ultrasonic with any fluid at all. If the dial-maker used any paint whatsoever in printing the text on the dial, it will flake off. I've even tried putting fired porcelain dials in a mild ultrasonic bath and, while the hairline cracks and crazing came out sparkling clean, the soldered dial feet fell right off the bottom of the dial. Every time I've put a dial in the old ultrasonic, something's gone wrong, so you take your chances for sure!

 

aside from the usual cautions, it would be helpful to know what watch and materials you are dealing with. And if it is a vintage watch of potential collector value, don't even touch it.