I've been thinking and trying to understand why the relief might depend on the contrast index of the negative. Intuitively, it shouldn't. I mean, the relief depends on the amount of gelatin in the shadows. That is, on the shadow density. That is, on the contrast of the print. And I think it shouldn't matter whether the contrast of the print was attained by lowering the dichromate concentration, or by using a contrasty negative. As long as you get the same print contrast, you'll get the same shadow density and the same amount of gelatin in the shadows, ergo the same relief, regardless of the method you used to achieve that contrast, right?
But then I think I've found the answer. I think what really affects the relief is the concentration of pigment in the glop. If you use a low pigment concentration you'll need a thick layer of gelatin in the shadows to get deep blacks. A high pigment concentration will give you deep blacks with a thinner layer of gelatin.
So, I think that if you want a prominent relief you need to use a lower pigment concentration. Lower pigment concentration means intrinsically lower print contrast, so now you have to increase the contrast somehow, either by using a contrasty negative or by lowering the concentration of dichromate. But since there's a practical limit to how low you can go on dichromate, starting with a contrasty negative seems like the best option.
So, my guess is that a very contrasty negative is not mandatory for getting a strong relief, but it helps by allowing you to use less pigment and still get good contrast without resorting to impractically low dichromate concentrations.
Am I right?
Vaughn, how much pigment do you use for one liter of glop?