A Kiln can take up to 12 Wet Clay Jugs, and needs 6 Wood to fire. It takes 2 minutes for the Kiln to create Jugs.
Jugs are used for carrying water and sulphurous water. To fill, visit a waters edge and select the Water icon.
Everyone receives a single free jug from a School of Architecture when you first attempt to learn Pottery. The game will attempt to stop you from losing your last jug (for example, when trying to build with it) so try to always have extras.