Digital BW, The Print

Why am I getting a "solarized" effect in the very dark areas of some 
of my prints ?
It's not really solarised in the traditional sense - but it's like 
a "blotchy-ness" in the black areas.
setup= MIS Sepia Quadtone ink/1160/PS6/Windows98SE
thanks
Frank

On which paper(s) Frank?

>Why am I getting a "solarized" effect in the very dark areas of some
>of my prints ?
>It's not really solarised in the traditional sense - but it's like
>a "blotchy-ness" in the black areas.
>setup= MIS Sepia Quadtone ink/1160/PS6/Windows98SE
>thanks
>Frank