Abstract: A steam transformer (200) receives steam through a steam inlet (203), and the steam is mixed in a mixing zone (231) with water entering through a water inlet (205). Steam cooled by contact with the water exits the steam transformer through a cold steam outlet (216). Between the mixing zone (231) and the cold steam outlet (216) is positioned a demister (214) that restricts the passage of water droplets. The steam transformer (200) is used to condition the steam temperature in steam turbine and combined cycle turbine facilities when adjustment of steam temperature is required, such as for cold starts of turbines. The steam transformer (200) may be installed into a bypass circuit or directly inline. A number of differing configurations and designs are disclosed.