I’ve wanted to draw something with a Bic biro for ages—that indigo blue kills me. Then I found that spraying a bit of isopropanol makes the ink run, and you get this great watery effect. (Though it seems to be only the magenta pigment that runs. The cyan doesn’t seem to run much).
Drawn on 300g brilliant white Clairalfa inkjet paper.
The Bob Mortimer (the bottom one) was the first I tried this way. It looks OK… but there are probably too many lines going on. Less is definitely more when you get it right. The drawings above Bob are more like it.