Rotring is a German technical writing and drawing instruments company based in Hamburg. They are pretty popular for their technical pens, of which I have several.
This reviews covers the Rotring drawing black ink. The ink is sold in either the large 250ml bottle or smaller 23ml bottles.
The big bottle comes with a tapered end you can use to refill smaller bottles. The smaller bottles also come with the tapered end that can be used to refill the Rotring technical pens.
I don't use my Rotring pens that often, and even so after months, there's no clogging. Since it's pigmented, it is not advised to use it inside fountain pens.
I've also used it to refill my Pilot Hi-Tecpoint pens.
Here's the ink test on cartridge paper. Below are close-ups. I've adjusted the exposure of the scan to retain the paper texture.
The Rotring ink is a pretty dark ink that dries to a neutral tone. It's a pigment ink so it's archival. Spraying fixative on it will not break the ink.
It has a fast drying time. It's waterproof when dry, and rubbing your finger over it will not smudge in any way.
Interestingly, the Rotring ink can dry to a slight sheen depending on the paper. On most occasions, I would consider it to be matte as I rarely see the sheen.
In the sketch above, I've used Rotring and Noodler's ink on the Strathmore 400 Series Mixed Media vellum surface paper 300gsm. The left and right are inked with the Rotring and they dry to rather even surface with slight gradation. As for the Noodler's ink, you can see that it was very patchy, and the colour tone is warmer. The point is, paper makes a difference.
Another strong benefit of the Rotring is after it dries, it will not smudge even even you rub across the surface, either with your finger or tissue. That means you will have little or no chance of your hand accidentally smudging the paper when the ink is dry, and also lesser need to clean your scanner's glass.
Here's a scan of Rotring vs Noodler's ink. Noodler's is darker, and has a warmer tone that you can detect when it's not applied so thick.
One thing to note. You'll need to shake the bottle if you haven't used the ink for a long time. That's to achieve a consistent black. Seems like the whatever black particles do settle down at the bottom of the bottle with time.
The picture above compares various brands of black ink. Top half of the square's a single layer wash and the bottom has a double layer wash.
Overall, it's a very good black ink. It's quite dark, dries fast. When it's dry it's smudge-proof.
It's safe for use in technical pens since Rotring makes this ink for their pens.
Both the big and small bottles have tapered ends so they can be used to refill the Rotring technical pens. Just the the small bottle is much easier to control
Search Jackson's Art Supplies (UK) too.