These lanterns have been field tested for heat conductivity: Tea lights are recommended, as after four hours of burning, the lantern can still be picked up by hand by the container. The handle, however, does become warm. Although indoor use is preferred, they can be used outdoors on dry evenings. A moisture resistant sealant has been applied. However, direct sunlight and rain could alter the lantern appearance. Please note, light intensity will vary depending on the candle used and the darkness of the room. The above pictures were taken in a pitch black room.