Originally posted by Praktica*ist I have tried everything : alcohol, naphta, soapy water, vinegar. Nothing worked well : corroded surface.
If the piece you're trying to clean is not coated (just glass), you might want to try metal polish.
I had a filter that wasn't coated. It had spots that would not come out with alcohol, acetone, white vinegar, lens cleaner, lighter fluid. dish soap.
None worked so I figured what the heck and tried metal polish (Metal Glo Professional) was the name of it.
I gently rubbed the surfaces with a soft cotton cloth, wiped it clean and WOW the lens was clean and clear...no more spots...looks great.