has several good pages on negative painting. See the end of this blog for 4 other blogs on the subject.
Today we did three exercise to try to understand what negative painting is. Here is a simple explanation: The positive is the shape of an object and the negative space is the space behind the object. In this picture (the stencil) the positive shape of the leaves is on the left; the negative shape is on the right.
To do the first exercise, first use two colors to create a background. Salt to create a little texture.
When it is dry, trace the stencil and paint a color two values different around the shape. That is the negative. When that is dry, draw another shape, and paint around both of those shapes slightly darker values. Dry, and continue to draw and paint around the shapes until you are pleased with the picture.
For The second exercise, draw three circles onto the paper, and paint BEHIND them. I used yellow. T
Dry and draw three more circles, some ovelapping. Then paint around all the circles. (I used pale green) Now you can see white and yellow circles with green background. Then make three more circles, and paint even darker around those. Now I have white, yellow, and pale green circles with a darker green background.