This is a process I learned from Kathie George. It's similar to batik painting on fabric.This process involves painting watercolors into sections of absorbent kinwashi paper that have been outlined with paraffin wax. The wax acts as both a reservoir to contain the colors and as a resist to preserve the white of the paper.
Light colors are painted first and hot wax is applied over the areas that should remain those colors. Then overlay and blocks successively darker watercolor paints.