I have a doorknob problem [somewhat similar] and maybe you can help. In the oldest part of our house [approx. 80 years], all of the doors have glass doorknobs with what appears to be brass plates. I want to remove them and thoroughly clean them since years of re-painting and lack of polishing have dulled them considerably. But, I am afraid of damaging them and want to proceed cautiously. Does anyone have a suggestion about the best way to proceed and what products to use?