What is Terre de Fer? It's a fine and very hard earthenware developed from 1860, it's obtained by adding with feldspar clay and kaolin. Very white, it's close to porcelain but is not translucent, which also earned them the name of "Opaque porcelain".
Its whiteness allows it not to require opaque enameling but a simple transparent glaze allowing the realization on the precooked earthenware very beautiful patterns, colored or not, which will be protected by this glaze. They will open the way to very artistic earthenware. It's a different brand from the stamp and it's a trade designation! These earthenware support the heat (but not the flame)!