Negative Painting is a painting technique, often used in watercolor. In short, it means creating the shape of an object by painting what is behind first, and thus giving an object a shape before it is painted. In watercolor, you often paint from the back to the front, which means that you first paint what is at the back of a motif, then paint what is next to the back, and so on, until you finally paint the part of the painting that is closest to the viewer.
When you paint in this way, you are often forced to paint around an object, it can be a house, or a fruit, whatever is in front of the background, it is very important that this object gets a credible shape right from the start. It therefore takes a bit of planning and drawing before you can achieve a negative painting.
The drawing is the skeleton on which the whole painting is built, without a stable skeleton the rest of the painting collapses. This is especially obvious when making a negative painting, without a sensible drawing it is almost impossible to create the shape of e.g. an apple by painting around it. I usually tell my students that all lines that are important in a painting should be drawn, less important lines are not drawn, you just ignore them.
Follow the lines
If you have drawn a perfect apple and are going to paint the background, you will find, if you are right-handed, that it is much easier to paint the surface to the right of the apple, it is difficult to paint to the left of the apple because you can not use the brush tip for the contour around the apple, the solution is simple: turn the paper upside down, then you can follow the lines equally easily on both sides.
Reserving highlight for dark details
Small dark details, which will later be painted black, seem unnecessary to paint around, you can easily paint them afterwards with dark color on top of the background. But I think it looks dead and dull when you paint that way. I always paint around all the little dark things to later fill in with dark color, but not all the way to the edge, the white highlights, though only small, that arise between the background and the dark detail do a lot to highlight the detail. As an example of what I mean, I have chosen a still life.
Plan for grass and the like
In watercolor it is not possible to change lines afterwards, if you paint a straight line in front of a house where grass grows, you can not later remove it by painting grass straws on top. It is important to constantly plan for what is in front of an object. It can be grass, branches or a crease in a canvas, always think of what is in front of an object.