How to Use a Painting KnifeIf you’ve ever spread frosting on a cake, you have an idea of the textural possibilities when using a painting knife to create an oil painting. Different from painting with a brush, this process can help you achieve a variety of effects, from the sweeping strokes associated with impasto to refined details. Enjoy this technique article on everything there is to know to get started using a painting knife.
Painting Knife or Palette Knife?The terms painting knife and palette knife are often used interchangeably when describing the technique of applying paint to a surface with the blade of an artist’s knife. Both tools are made of either plastic or of wood and metal. Both are available in a variety of blade shapes and sizes. A palette knife handle is generally straight, having at most a slight bend. The purpose of the palette knife is to mix colors or clean the surface of the palette. On the other hand, a painting knife has a deep bend in the handle that keeps the artist’s knuckles out of the paint. As its name indicates, a painting knife is used for actual painting. For the remainder of this article, when I use the word knife, I’m referring to a painting knife. A palette knife handle is generally straight, having at most a slight bend. The purpose of the palette knife is to mix colors or clean the surface of the palette. On the other hand, a painting knife has a deep bend in the handle that keeps the artist’s knuckles out of the paint. As its name indicates, a painting knife is used for actual painting. (Note: For the remainder of this article, when I use the word knife, I’m referring to a painting knife.) A knife with a metal blade has more spring to it than one with a plastic blade. Both metal and plastic blades have rather dull edges, and although some blades have a sharp point, a painting knife isn’t so much a cutting tool as it is a spreading tool. Choose a painting knife for its shape, as different shapes will create a variety of effects. The way you hold the knife, its angle to the board, the amount of paint on the blade and the direction you pull it through the paint or drag it on the surface all add to the painterly options and effects available to you.
Surface and Paint ConsistencyI’ve found that the painting surface for a piece done with knives must be firm to prevent the paint from cracking as it dries. Ampersand Gessobord works well, and there are many other suitable surfaces on the market. I begin my painting knife pieces with an underpainting done in oil thinned with an odorless paint thinner, such as Gamblin Gamsol, and applied with a No. 10 or 12 bristle brush. With broad, loose strokes, I cover the white of the board, establishing color and value. The values of the underpainting are often a bit darker than those I anticipate using for the finished painting The values of the underpainting are often a bit darker than those I anticipate using for the finished painting because light over dark yields a more desirable result. Because some areas of the underpainting will be visible in the finished painting, I choose underpainting colors that are analogous (near each other on the color wheel) to final layer colors. When painting with knives, mix your colors on a palette, but don’t add any medium that will thin the paint. You need the paint to be thick so that it will maintain its shape and stay where it’s put.
Wielding the Painting KnifeApply paint with a knife as you would spread frosting on a cake—working the texture to achieve the desired thickness and swirls. I hold the knife as a conductor would hold a baton and change the angle of the knife to the board to achieve the desired effect. A clean palette knife is essential when changing colors. To remove paint from the blade, simply wipe it with a clean cloth or paper towel. Carefully inspect the painting knife after each stroke once paint has begun to accumulate on the board. Nothing is more frustrating than making a mark in the water area, for example, and realizing that dark green from the tree area was on the knife.
Choosing the Painting Knife SizeSmooth, relatively flat areas can be painted with a large blade, so the larger painting knife in my collection is used for laying in large areas of paint—water or sky, for example. Used on its edge, the midsized blade creates effects like reflections, masses of trees or thin lines that add texture and detail. I can also dip the small, rounded tip of this blade into paint, which I can then carefully apply to create details. I use my smallest knife for small edges in trees or other details. Occasionally I use a knife with a ¼-inch square tip for making a mark that could be a distant building or window. The corners of the blade are also excellent for creating fine detail. Keep in mind that you can use painting-knife techniques with other paint applicators. Cutting expired credit cards into different-sized strips lets you create custom shapes for applying paint. For large areas, try a metal or plastic ruler.
Sgraffito and ScumblingIn order to give an edge between the sky and trees a varied, atmospheric appearance that suggests distance, use the edge of a clean painting knife held at a 45-degree angle from the surface of the board. Connect the sky to the trees with up-and-down strokes of the knife, allowing it to gently touch the paint in the sky and in the trees. These strokes exemplify the technique of sgraffito, gently scraping the surface of the board to expose some of the early underpainting and blend a bit of the two areas. The goal of the sgraffito is to keep this edge soft; remember that trees are a rounded mass going back into the distance. This technique can be tricky; there’s nothing about this particular part of the process that resembles spreading frosting. The movement of a painting knife through the paint will result in some serendipitous painterly strokes. Work carefully as the top edge of a tree mass is created, making some edges more pronounced; others soft. With a clean palette knife, you can use the technique of scumbling by pulling a bit of paint from the sky into the trees or some paint in the trees closer to the sky. You can also use scumbling to create “sky holes” within tree branches.
Drying PeculiaritiesAs your paint begins to dry, a “skin” forms that will pull and drag as another layer of paint is applied, often creating an undesirable effect. When a painting session is finished, ridges in the paint must be neither disturbed nor covered with more paint until the drying process is further along. Completed paintings done with relatively thick paint must be allowed to dry for six months or more. The surface of the paint dries to the touch more quickly, but closer examination will reveal soft inner layers that can be easily damaged. I recommend applying a finishing varnish after many months—up to a year if the paint is quite thick.
The Frosting on the CakePainting with a painting knife is fast-paced, exciting and fun, producing finished pieces that evince textural qualities and expressive gesture. What’s more, after creating a few of these pieces, you’ll find that frosting a cake will be a snap.
This article by Deborah Quinn-Munson on painting in oils with a painting knife, first appeared in a past issue of The Artist’s Magazine.