I saw this on FB the other day and thought I'd share.
Terra cotta is ceramic clay that has been partially fired in a kiln. A terra cotta clay pot heater is an effective way to heat a small space, such as a boat, shed or small room. Metal hardware inside the terra cotta heater helps heat the terra cotta; three pots nesting inside one another create pockets of heat that are radiated slowly and steadily from the porous clay to the air surrounding it. Terra cotta is heat resistant, so the flame from the candle inside it will not compromise the integrity of the clay.
Read more: http://www.ehow.com/how_12094083_mak...#ixzz2pqHLSwd0
http://www.survivalpunk.com/ceramic-flower-pot-heater/ Maybe not....