A method of heat treatment of a non-metallic or metallic item is provided. The method includes at least one step A) of heat transfer between the item and a heat transfer fluid A′ including a fluid medium and nanoparticles. The heat transfer fluid has a heat transfer coefficient above the heat transfer coefficient of water. The method also includes at least one step B) of heat transfer between the item and a heat transfer fluid B′ including a fluid medium and nanoparticles. The heat transfer fluid B′ has a heat transfer coefficient different from the heat transfer coefficient of A′ and above the heat transfer coefficient of water. The heat transfer fluids A′ and B′ are different.