I recall buying my first bottle of used (beg pardon, 'previously owned') Montblanc ink on fleabay. Yay! I thought; I'm significant now! I own an ink bottle shaped like a shoe!
It was black. It wrote black. And so on and so forth, until I had acquired a couple more bottles of black ink, all of which wrote...black.
But then something interesting happened. Seeing a review of PR Velvet Black, and being impressed with the brilliant corona produced by dropping it on a paper towel, Dr. I did a series of paper towel chromas, with four bottled blacks. The results were not what I expected. The Levenger Raven Black was...black.
The others were a surprise, and far more colorful. Now I wonder...is the Montblanc even a black? It sure writes like one. Waterman and Quink seemed very close in color components, but in daylight, and not scannage, Quink's corona was slightly more intense orange. Still, I don't think any of them were as much of a rainbow as the PR Velvet! Which clearly will be coming to my ink shelf soon.