This is the stage where the painting is being covered with permanent black ink. The black ink will be permanently left on the areas where there is no white tempera. This stage of the ink resist watercolor painting is to left dried overnight. Next will be the wash shere areas of whte temera is being washed away.
You can see from the above image that the tempera and black ink is being washed away from the paper surface. Warm water and a scrubbing brush is used for this step. This left only the lines and some areas of the painting where the black permanent ink has eat into the watercolor paper surface. After the paper is completely dry it is ready to be painted using watercolor, gouache, or Acrylic paint.
– Peter Lau