Elk P. answered 05/05/19
Working artist for 10+ Years
The problem is the Staedtler ink, for sure. I've had the same problems myself! Some live and die by Micron or Rapidograph or whatever technical pens, but in my own practice I just eventually moved over to old-fashioned dip pens (like with a nib) because the black point of dipping ink is much deeper and doesn't "lift" like pen ink. This has to due with the density of particulates in the ink that has a higher sticking point to the paper, resulting in a higher opacity. That density of ink really can't move through the way pen barrels set up their tips because they're too viscous, but nibs hold the ink on the outside of the tip so working with a dip pen is basically controlled dripping! My favorite ink is Dr. PH Martin's Black Star (Matte) because it really is as black as space itself! Works really great for scanning, as well, since it's non-reflective. The important thing with more viscous inks, however, is taking good care of your dip pen or fountain pen so it doesn't get clogged or rusty. I do know some artists also use a brush with ink as well, which can create some fine effects. So you may want to look into that as well.
I'd say if you don't want to take the plunge into dip pens, I'd buy yourself some Microns of various thicknesses instead. Also, you may want to try getting a softer eraser in case you're erasing too hard. I reccommend Mars rubber erasers, those are my favorite! I feel like the blue Staedtler ones are a little too rubbery and don't have as much give as the Mars ones.
Let me know if that helped you out! There's a lot of tutorials online about what inks lift the least and how the opacity of inks fades over time among different brands, so be sure to look that up if you want to know more. Best of luck!
-Elk