I have been experimenting with pen and ink. Previously, I have used waterproof ink, with watercolour on top. This “pen and wash” technique depends on the ink staying where it’s put. See, for example, the urban sketch on this link.
Recently, inspired by the work of Nick Stewart https://quinkandbleach.wordpress.com, I have been trying non-waterproof ink.
Here are four sketches, done in the Hôtel de France, Sainte-Croix, Switzerland. Click an image to enlarge.
They are all done using only Robert Oster Signature Fountain Pen Ink, colour: Black Velvet. This ink has the property that is produces a chromatograph effect, blue and pink, as it runs and dilutes with water. See, for example, the left hand side of the “wineglass” drawing, where you see black, blue and pink.
I’m using a dip pen: the Pensive Pens Serendipity dip pen.
All of this is quite a challenge to accomplish, especially as the pictures were done in a Swiss dining room, on white tablecloths. No ink drops contaminated the pristine environment. But I had to be very careful.