How do you resurface and old clay pot?

Go WAY down to the bottom of this article and there is a section on how to do exactly what you want:

http://www.backyardboss.net/revamp-patio-pots/

Good luck!

Hello Maureen, First clean the pot with a hard bristle brush. Then soak it in a mixture of 25% vinegar and 75% water for 20 to 30 minutes. If the pot comes out clean, you're done. If not, continue the soaking process. When it comes out clean with a quick scrub, you're done. For tough stains or dirt you can soak it in pure vinegar. Then you should either wash it well with hot soapy water or run it thru a cycle in your dishwasher. This step is important because it will disinfect the pot. Then it's ready to plant. Hope this helps you. Good luck.

I sprayed some older clay pots that were chipping. My grand babies decorated a couple and wrote their names with the date. I sealed them with a clear spray varnish.