The day before at my school in the Visual Development class I created a demonstration for a student who was struggling with the concept or free form drawing. That's the term I use for sketching with a non-erasable medium such as black line pen of marker. This is what I drew for her and then rendered in blue afterwards.
Today I finished an image that was related to the idea of free form drawing. Instead of drawing in black line first I instead sketched the concept in blue pencil and followed up with line.
One of the advantages of working in a permanent medium such as black line is that it takes away the option of erasing and thus develops a greater confidence in your ability to commit to the emerging composition. It's a great exercise for any artist who's looking to reach higher levels in the creation of their art.