All these inks come in 30ml (1oz) glass bottles with droppers.
Black Star Matte and Bombay Black are difficult to tell apart. They seem to have the same black intensity. Black Star HiCarb is the darkest compared to all other black inks I've tested.
Let's talk about the Black Star Matte.
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 and dries to a matte surface. It holds up well to erasing.
It dries fast and is heavily pigmented so it leaves behind ink crust after drying. Definitely do not use it in fountain pens.
The ink clogged 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. Opening of the ink bottles is quite small though.
Below are some simple tests.
The ink is able to hold a sharp edge well.
Watercolour added on top of Black Star Matte.
This is a wonderful ink to get if you need a black ink for illustration or comic works. It's intensely dark but it still doesn't overthrow the Black Star HiCarb in terms of darkness.
It dries fast to a waterproof matte surface. Even concentrated areas dry to a matte surface.
Price is more expensive compared to other brands but it's a quality ink.
Try searching on Jackson's Art Supplies (UK) also.