A hoary bat that is...
Scratch board is a medium that is sort of the opposite of pen and ink. You apply ink on clay coated paper and then scratch away the ink where you don't want it. You will often see scratch board that has been pre-inked in black, but the disadvantage to that is you don't always want the whole surface to be black. Whoa. Imagine if I had to scrape away black around the whole bat. It's much better and faster to only paint the areas that need it. I'm learning that science illustration is learning how to make the most efficient yet effective illustration. Ha! Despite that, it is still pretty time consuming. I guess some things you just can't speed up.