Getting a good dmax with Gum Bichromate

I am struggling to create a gum print with a good dmax. Yet as I print more black layers, the image just gets muddy looking and loses definition. I am wondering if by printing a blue layer first, the black would look better.

Does any one have any suggestions? Would printing a Cyanotype layer work or is there a really nice blue pigment that I could mix into my black or lay down first?

I would appreciate any suggestions.

Do you cut back printing times between each layer? A black layer printed with 25% of the initial standard printing time can give you the punch you need whithout touching middle tones and highlights. in my workflow I keep gum/pigment and dichromate ratio constant between layers and print each subsequent layer with a shorter time. Then the density rises more in the shadows and less in the highlights. The result is a higher density range without mud in the middle tones and highlights.

And do you print on sized and hardened paper? If not you probably print a thin black pigment fog each layer. And these add up!

-kees