"Unity? "Hakone" Matte Black Tetsubin Teapot/Wood Stove Humidifier. The "Hakone" Teapot is an elegant cast iron tetsubin teapot inspired by highly prized Japanese antique teapots still in use today. It's large 3 liter capacity and robust construction makes it uniquely suited for use as a wood stove humidifier, as well as it's traditional use of heating water for tea. The enamel lined interior makes it rust-resistant and easy to clean.