The Clay Furnace is a furniture you can build (the Technology page).
In-game description
A beehive of clay with a fire in its belly: it smelts ore into ingots, and burns wood into charcoal. Load a batch and go about your day; it works while you're away. Upgraded at it, it grows into a Stone Bloomery and a Blast Furnace.SHOWN IN THE BUILD RING
Building it
It costs 12 
Stone, 4 
Wood, 2 Any Grass, 1 Water 3 Earth 2 Fire spirits. Take it down with DISMANTLE to get its cost back (see Building).
Upgrades
| Tier | Name | Upgrade cost |
|---|---|---|
| I | Clay Furnace | Built as it is |
| II | Stone Bloomery | 20 Stone, 6 Wood, 4 Bronze Ingot, 4 Beechwood Planks |
| III | Blast Furnace | 30 Stone, 8 Iron Ingot, 4 Glass, 10 Peat |
See Table Upgrades.
