Ice-nine is a material appearing in Kurt Vonnegut's novel Cat's Cradle. Ice-nine is supposedly a polymorph of water (invented by Dr. Felix Hoenikker), more stable than common ice (Ice Ih); instead of melting at 0 °C (32 °F), it melts at 45.8 °C (114.4 °F). When ice-nine comes into contact with liquid water below 45.8 °C (thus effectively becoming supercooled), it acts as a seed crystal and causes the solidification of the entire body of water, which quickly crystallizes as more ice-nine. As people are mostly water, ice-nine kills nearly instantly when ingested or brought into contact with soft tissues exposed to the bloodstream, such as the eyes.
In the story, it is developed by the Manhattan Project in order for the Marines to no longer need to deal with mud, but abandoned when it becomes clear that any quantity of it would have the power to destroy all life on earth. A global catastrophe involving freezing the world's oceans with ice-nine is used as a plot device in Vonnegut's novel.
ICE-9 is an album by Susumu Hirasawa. It is predominantly instrumental; Hirasawa plays guitar to different electronic soundscapes that occasionally include his voice. The title is an allusion to the 1963 science fiction novel Cat's Cradle.
The custom-made guitar played in the album is also named ICE-9. It was designed by Hirasawa, and was first used in the LIVE VISTORON concerts during 2004.