User blog comment:LiamFrostveins/Elemental Manipulation/@comment-4536066-20130115160158/@comment-4536066-20130319234308

I don't agree that you would necessarily require fire runes to make steam. Steam is just water with high levels of kinetic energy on the molecular level, and if a mage can alter the molecular behavior of the water, he would be able steam from nothing but water and runic energy.

That said, the addition of fire would accellerate the molecular water naturally by heating it in a traditional manner, so would probably require less effort on the part of the mage.