I posted a review of the Kaweco AL Sport Stonewashed Blue pen in the pen reviews forum. Here. I am now adding a separate review of the Kaweco Midnight Blue ink that I used in that pen. I used a cartridge, and the AL Sport Stonewashed Blue pen has a F steel nib. Kaweco ink comes in 30ml bottles and packs containing 6 standard international sized cartridges. This Midnight Blue is lighter than some other blue-black inks, but it's a really well behaved dark blue, and it has some lovely shading. It isn't waterproof, but was reasonably water resistant. I moved the water around with my finger, then blotted it off, yet I can still see ink remains. It's a reasonably saturated ink. I would say it's definitely worth considering.