I have recently been experimenting with pen and ink . Firstly some using genuine Indian Ink and a dip pen. This of course is shellac based and is very dense black and dries to a glossy finish. Indian ink will clog up and ruin fountain pens. I wanted a waterproof ink so as to be able to add a watercolour over wash if desired. Most fountain pen inks are not or only partly waterproof. I saw that pen enthusiasts recommend Platinum brand Japanese Carbon Black as the best choice. I have found it very good for fine work on semi rough 100 % cotton watercolour paper. It is almost as dark as Indian Ink but dries matt and seems quite waterproof. One unusual think however is that I often mount my paper works on a gesso coated plywood using a thick gloss acrylic gel and when I did this today for my two latest drawings one turned from black to a mauve colour while the other did not! I imagine the gloss gel has permeated to the ink in one case and not the other. I will definitely be interested to see what happens as the gel dries over a day or two. The colour change is quite attractive but totally unexpected.