Oh thank you guys so much! I think this is one of the best exercises I do to actually help my painting.
Alex the inks vary (I'm posting a link that shows the ones I use) I believe this is a WS sepia which holds the line after draw, but my favorite is a Sennelier shellac base that has a wonderful luster when dry, but unfortunately you spend more time unclogging your nibs than drawing. These are the shellac as a wash only.
Here's a demo I did for the wash technique:
Pen and Ink Wash Technique