Left: Sketch of a character actor made with Pentel's Aquash Brush Pen Filled with Light Black ink. Click on the image to view the enlargement. (Very odd drawing paper that buckled if you even looked at it, hence all the shadows.)
I think the caption pretty much says it all. If you want to have some fun with the Aquash pen, which comes filled with light black ink, turn on an old 1960s TV show or black and white movie and sketch away.
I find this brush pen is a nice break from the saturated blacks of the Pentel Pocket Brush Pen. Sometimes I just like to be able to restate lines and have them become darker.