Decided on my trip to the Fountain Pen Hospital last week to add a bottle of Montblanc ink to my collection, if nothing more than to have one of their distinctive ink bottles. I have a lot of blue inks, but very few blacks--the Noodler's and Montblanc increased my collection 100%, for a total of 4 (or 3.5 really, since one ink is a limited edition bottle half the size of a regular ink).
What was surprising was then I swatched the shades to get a sense of the different blacks. The Montblanc Mystery Black was quite thin and almost watery on the paper, even thought I made sure to shake the bottle so that there was no possible separation. The Mystery Black also has a definite purple hue to it that I rather like, although this picture doesn't show the shading very well. I think you can see it best in the last streak of color on the bottom of the swatch.
Interestingly, J. Herbin's Perle Noir was a medium black, definitely a nice dark shade but also a bit thin on color. The surprise was Noodler's Old Manhattan Blackest Black. This really is the blackest black ink of the three, it looks like liquid coal it's so dark.
Now the test for the Montblanc Mystery Black is to see what it looks like in writing. I've loaded up my Pelikan M205 Clear Blue fine nib fountain pen and will compare it to the Noodler's Old Manhattan still in my Parker Latitude. Should be interesting, and I'll have more to report at a later date.