Blackboards are fun to paint, so if I get a chance to stick one into an illustration I jump at it. It's also easier to work some words into the drawing that way, and words are marginally easier to contend with than drawing. This might be what makes one a cartoonist; not a facility for combining art and language, but an inability to decide which one you'd rather be using.
I don't know; whatever. This was done for an academic engineering association magazine, and the article detailed the sometimes-overwhelmingness of the academic life. I've only got a passing acquaintance with academia- a coupla years at a (very good) community college without graduating and a brief stint teaching illustration at the Maryland Institute of Art in Baltimore as an adjunct professor (I think it's called). It was a limited course of one day a week for a month, but pretty hands-on. I ran out of things to say really quickly, and the students probably wished they'd chosen one of the other professionals to learn from. But it was fun and interesting, and I did learn that as a teacher I lack the ability to teach.
I will attempt to teach you this; my secret to painting an interesting blackboard in watercolor. The board is a loose mix of two colors that I often use for a dull yet textured green: Daniel Smith quinacridone burnt orange and Holbein terra verte. They're opposites in several ways. The burnt orange is transparent and staining and the terra verte is opaque and floats above the orange. Put some of the orange down and flood it with the terra verte and it'll granulate quite nicely, then keep messing with it till satisfied. The white lettering is Schmincke's Calligraphy Gouache, which is very heavily pigmented and dense, and applied with a long, thin lettering brush. There, who says I can't teach? For extra credit, somebody please tell me why stints are always brief.