The above is a gouache resist. I have painted quite a few of these and left several in their black and white form. I like the suggestion of “block print” that they seem to carry with them. The full process for doing one of these can be found here.
This is the largest one I’ve painted and I was nervous about how it would take during the rinsing process. I didn’t need to worry. However, with another small one, I learned I must wait patiently for the ink to dry thoroughly and not rush it with a hair dryer. The hairdryer causes some ink to work through the gouache. A more clear image will appear if you allow the ink phase to air dry.