"You only need enough of one substance to turn it into another. Granted, the substances have to have similar chemical structures to begin with. Like I said before," He pointed to the river. "No matter how hard you try, you're not going to be able to transmute steel out of water. They're too different."

He frowned before continuing. "There's also limits on what kinds of things you can work with." He'd better tell her now before she got any ideas. "Don't even think about trying alchemy on humans. You'll only end up with a rebound." He waved his automail hand at her. "I know from experience."