PARKER QUINK PERMANENT BLUE-BLACK INK
Over the years this has been my go to blue black ink. It writes smoothly, dries quickly without bleeding through lesser quality paper, doesn’t fade over time, is a little bluer than some blue blacks (that tend to have a flatter tone), and is reasonably priced. I use this ink in my Parker 51 (both Aeromatic & vacuumatic), Duofold, and Estie, and really like the consistent line. Pick up a sample and give it a try if you are looking for an everyday blue black ink.