Heating with direct flames is not recommended: reason 1: Wood handles may burn out when heated so reason 2: Direct heat may damage the surface coating.
If you still need to heat it with a direct flame, please note: 1. If you are heating directly, please control the water under 500cc, so as not to get the water out of the spout and burn out when boiling 2. Adjust the fire to a small limit to prevent surface coating and handle.