Check out this project: http:just-a-bit-of-wet-clay.tumblr.com
The organizers are looking for artists to send in one ounce of wet clay in a normal envelope using a Forever stamp. The idea is to fire the pieces of clay as they arrive, recording the impressions left from mailing and delivery. All the pieces will be displayed in an exhibit in St. Petersburg, FL.
The exhibit explores "the archival nature of clay to the poetic and preposterous nature of a FOREVER* postage stamp."