I have noticed the top of our kitchen table, in the morning, after reading the newspaper. It gets almost black with transfer of ink from the paper. Use a piece of the paper that contains a lot of print or a good dark B/W picture and try wiping the chip with it. The ink may rub into the relief. An earlier thread, a couple weeks ago mentioned the crud on played chips. Think of what that might consist of and try to duplicate the more benign components. Rub your fingers into your hair to pick up oils, get some newsprint on your hands. Stick your hands in a bucket of coins and get them REALLY BLACK AND DIRTY, and then just rub that around on the chips and wipe off the excess. The dirt and metal dust from coins and all the other items are some of the very components of wear.

I am sure some others may provide some other reminders of what might be in the crud on our chips but, frankly, I am trying to avoid going there.