People are often surprised when we tell them that we use painting knives instead of brushes. They point to some fine lines on a painting and ask if these were also painted with a knife. Yes, they were. We use brushes mainly for what we call back-painting, by which we mean covering an area of the white surface of the panel with a color that is better than white as a background before adding the details with knives.
For people who have never heard about knife painting we have to explain that painting knives are not like kitchen knives. They are more like miniature spatulas, usually triangular in shape. The photo on the left shows the large collection of knives that we have gathered over the years. The knives that are in current use are arranged in tubes or holes drilled in wood that are sufficiently separated from one another to keep them from touching each other. The fifteen positions arrayed around the palette enable us to use fifteen different colors at once while working on a painting. This arrangement reduces the boring task of unscrewing and screwing color tubes, helping us to maintain a wide range of colors.
By this arrangement we can use 10 different colors at a time, each one on a separate knife. We prefer knives because they allow us to control the colors better than we can with brushes.
Years ago, when we used brushes, we weren’t able to clean a brush between every application of paint. Consequently the brush continually mixed the pigments, making them muddy or desaturated. With the knife we can apply the pigments straight from the tube, wiping them between applications, so that the colors remain pure and bright. Where desaturated colors are needed, of course, we can mix the desired level of desaturation.
Another reason for painting with a knife is that it allows us to sculpt the surface of the paint so that each object reflects light as it would in real life. This gives the painting a depth that we could not accomplish with a flat surface. A field of grass looks soft because individual blades scatter the reflected light. When painting grasses or pine needles we use the edge of the knife, making thin ridges of paint that give the surface a third dimension. The ridges break up the light in the same way that real grass would, giving the surface a soft appearance.
Hard, flat surfaces like bark on tree trunks reflect light in patches while the cracks in between trap most of the light and thus appear dark to the viewer.
When painting bark we might underpaint with dark brown, then build up the bark by laying on ridges of paint, and finally, when the ridges have dried, use a technique called “scumbling” in which we run over the dry plates with our knives to add highlights, moss, or other features. Essentially, we are painting in three or four layers. The picture above illustrates the result of this technique. The photo was taken at an acute angle so that you can appreciate the three dimensional quality of the paint.