This ink is *not* waterproof for me. I bought a bottle for ink-and-watercolor sketches because I've been hearing for years that it's waterproof. Nope! I sketched a few lines, went over them with a wet brush. Smudged like crazy... I thought maybe I had not let it dry enough, so I sketched a few more lines and waited until the next day before swishing a brush over it. Nope; same large amount of smudging. Would be fine for line-and-wash (though I prefer the way my Quink black washes out), or for addressing envelopes that might go through rain in the post (lines were still quite legible, just now in a gray fog), but I'm glad I tested it before I ruined a sketch with it. I should've heeded JetPens' tests of this ink before I bought it.
This ink is *not* waterproof for me. I bought a bottle for ink-and-watercolor sketches because I've been hearing for years that it's waterproof. Nope! I sketched a few lines, went over them with a wet brush. Smudged like crazy... I thought maybe I had not let it dry enough, so I sketched a few more lines and waited until the next day before swishing a brush over it. Nope; same large amount of smudging. Would be fine for line-and-wash (though I prefer the way my Quink black washes out), or for addressing envelopes that might go through rain in the post (lines were still quite legible, just now in a gray fog), but I'm glad I tested it before I ruined a sketch with it. I should've heeded JetPens' tests of this ink before I bought it.