I don't understand how the gradation in tones is achieved. I understand that a darker area will have a deeper well and thus more ink than a shallower well, but I don't understand how that produces a darker tone on the paper.
For example, if the image consisted of two squares: square A is totally black and has the deepest well possible (e.g. Zone I) and square B is middle grey (Zone V), that will have a well that's not nearly as deep but it will still be below the surface of the plate. So far, so good. But, when the paper is pressed on the plate, what causes the ink for square A to produce a darker tone than that for B? There's more ink, yes, but why does more ink imply a darker tone? Is the paper less saturated?