"According to Mythbusters, the surface of the mint Mentos is littered with many small holes that increase the surface area available for reaction (and thus the quantity of reagents exposed to each other at any given time), thereby allowing CO2 bubbles to form with a rapidity and in a quantity that are responsible for the "jet"- or "geyser"-like nature of the effusion. This hypothesis gained further support when rock salt was used as a "jump start" to the reaction."