It is impossible to overemphasize the absolute indispensibility of a metronome when printing. Mine drives my wife and kids nuts and I've had to give up listening to music when I make prints, but nothing else has done more to improve my printing ability than this $30 device. You'll get that back in just a couple of printing sessions from the money you save on paper alone.

Michael Smith and Paula Chamlee use a metronome to make their contact prints and Ansel Adams always used one to make his enlargements. Try it and you'll know why.