In Sanders' sample, he believes the magnesium is ocean salt, while silicon, mixed with a small amount of copper, is the essential ingredient in synthetic rubber. The rubber, in liquid form, is the base into which the fuel is mixed before being poured into a container where it hardens into solid fuel. If a solid motor cracks, you have a disaster. It burns too fast and blows up. If dropped, it has to withstand breaking.
Aluminum powder is the preferred fuel.
Calcium is mixed with a perchlorate to provide the pyrotechnic effect. Silicon, mixed with a small amount of copper, is the essential ingredient for synthetic rubber which, in liquid form, is the base into which aluminum powder, calcium and a substance that provides oxygen are mixed, then poured into a container where it hardens into solid fuel, waiting for use.