I would NOT recommend fingernail polish remover (acetone) on a clay chip. You will likely dissoslve the chip. Acetone is OK on the inlay portion of a modern chip as it has a plastic coating.

You could try naphtha (Energine cleaning fluid). This is a less active solvent and will dissolve some kinds of paint. It won't hurt your chip.Occasionally, you will find that isopropyl alcohol (rubbing alcohol) will do the job.

If this doesn't work, I could only suggest an abrasive spray (sand blasting, in effect) using very small abrasive particles and working slowly.

Painting is a pretty effective way to cancel a chip, and you may just be out of luck.

DonL