Dr Martin's Black Star is a waterproof india ink.
Here's the description on the bottle:
Specially formulated non-clogging india ink for use in technical pens. Dries waterproof and completely matte with no reflection. Reproduces without glare. Excellent for use as a flat black wash.
There are also three small icons of a technical pen, brush and air brush.
The ink is very black, dark. It's advertised to dry into matte surface. That's is not different from most other ink so I don't see what's the big deal. I've yet to see black ink that dries into a gloss or semi-gloss, except perhaps certain gel ink.
I've tried the ink in a brush pen, Lamy (fine and medium) and Hero fountain pens.
This is quite a dangerous ink to try with fountain pen. Well, you shouldn't use india ink on fountain pens anyway. For this ink, I won't recommend it even if you use your pen frequently.
It dries fast and is heavily pigmented so it leaves behind ink crust after drying. I suspect that it's not suitable for use in technical pens either.
There's a tendency for the tip to dry up even when capped. Each time when the tip is dry, you have to flex the tip to get the ink flowing again, or you have use the convertor to force the ink out if it's really blocked.
The ink chocked up my Hero fountain pen and brush pen, and I had to wash them out.
This ink should probably be used only with dip pens and brushes.
Watercolour and Dr Martin's Black Star Waterproof India Ink