Originally Posted by Thunder
As far as I know, brass doesn't rust, it oxidizes.
and rust is iron OXIDE - same thing - Brass and copper-containing alloys have a small film of oxide that prevents further decay. An acid like vinegar (acetic acid) goes right thru that and eats away at the brass thus producing a green substance. There are few tobbaco products that contain that much green coloring so it's not from the gunk it's from the metal. Use hot water and baking soda to soften gunk build-up and render the hookah odorless. Use vinegar to displace rust on thick sheet steel hookah.