Karl Smith on printing money

Karl talks about James Hamilton's description of QE, the Fed is not actually printing money said Jim.
Karl responds that the conclusions is a short cut, the Fed generally prints money, that is how it works.
I respond to Karl. The Fed has to occasionally unprint money if we are to follow a smooth path. The part about unprinting money is vaguely explained, but that is the problem, how do we unprint money if we want to a smooth changing economy?