Have you ever considered doing a painting with nothing but white and black pigments?  If not, you may want to give this some serious thought.  There is a lesson here well worth learning.

Seriously, no matter what the composition is, whether a landscape or a portrait, try painting it without middle values.  What is light, paint it white.  What is in shadows or shade, paint it black.  If you’re like me,  you’ll feel tempted to go gray, slipping in some middle tones.  Don’t do it..fight the urge!  Keep it white and black.

This teaches much about contrasting values.  Later, when you do the finished work in color, you’ll feel comfortable that you have a true handle on this issue.  For a study, it’s worth the effort.