I had been hearing about Noodler's ink for years on sketching forums. It's a non-water soluble ink, so it won't run when you watercolor with it. A lovely friend just gave me an old fountain pen and a partial bottle of Noodler's to try. I'm having a fun time this week. I shifted from pen to pencil with my watercolor several years ago, but I had fun revisiting fountain pen and watercolor sketches in Paris. That was with ink that would run, and I kind of liked the looseness, but this has a neat, spontaneous, kind of graphic feel to it. I'm going to enjoy playing around with the ink as well as using the lovely pen.