C-7 Foaming Spray is a highly explosive compound that is used in demolitions by UNSC forces. It is comprised of various chemicals that react to a signal electrical current shock sent through a detonation switch. It is liquid in vacuum, but once contact with a hard surface and oxygen occurs, it becomes a foaming, semi-solid adhesive resin.
- C-4 is short for "Composition 4", therefore it is likely that C-7 means "Composition 7." It is also likely that it is simply a codename based on the order in which it was developed, not an indicator of its explosive power (i.e. being 1.75 times more powerful than C-4).
- The most likely reason C-7 was developed was so that the users would be able to simply spray it onto the surface, or so they could spray it into hard-to-reach cracks etc.
- C-7 is another reference to 7.
- C-7 is a possible relative to the more lethal C-12 explosive.