The Frasch process is a method to extract sulfur from underground deposits. It is the only industrial method of recovering sulfur from elemental deposits. Most of the world's sulfur was obtained this way until the late 20th century, when sulfur recovered from petroleum and gas sources became more commonplace (see Claus process). In the Frasch process, superheated water is pumped into the sulfur deposit; the sulfur melts and is extracted. The Frasch process is able to produce high-purity sulfur.