My engraver forgot to turn on air assist for a job, the entire lens turned black. We tried to clean it with the regular solution and also with some acetone. Acetone got off some of the black in the center but a ring of black remains. I'm a bit hesitant to soak it in the acetone beyond a few seconds in fear of the lens coating coming off, has anyone tried soaking a lens in acetone to remove black spots? Any other methods that work to remove black spots?
See photo of the black on the lens below:
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