Oil paint is probably the most versatile medium in a painter’s arsenal. A layer of oils laid down by a brush can be thick, opaque, dry and textured; or it can form liquid pools of color, transparent and flowing. When oil painting was invented in Northern Europe during the early Renaissance, it was prized for the brilliant effects made possible by its transparency.

As I was starting to illustrate Hansel and Gretel (Dodd, Mead, 1984; now Dutton), I developed a hybrid technique of which I’ve become very fond, one that mimics a Renaissance oil technique but takes less time. The idea is to use oil paint as transparently as possible, as a coloring medium over a complete but monochromatic drawing or painting; this underpainting supplies the darks and lights, the shading and shadowing of the objects, and gives the hues over it a kind of glowing richness that is usually called “jewel-like.”

Renaissance underpaintings were commonly done in egg tempera on wood panel, or in oil on canvas. Because I prefer to work on paper, and because it’s relatively quick for me, I make my underpaintings in watercolor. The watercolor paper should be smooth enough to draw on in detail and to allow even-looking washes of color, but textured enough that watery washes don’t pool up while drying. I find 140 lb. Arches cold press paper to be just about perfect. I generally stretch it (dampen and let it dry taped to a board) if the painting will be much larger than about 8” on a side. To paint the underpainting I use black or sepia watercolor, which dries into a pretty stable paint layer. This is important for the next step. If a reason arises, I will sometimes fill an area with a non-neutral color. For instance, if I plan to paint a sky using a bright blue pigment but I want the sky to look muted and not too light in value, I might underpaint the sky in orange, the opposite of blue, to counteract the blue from underneath.

An early stage of a painting from Rumpelstiltskin: outlines have been drawn
lightly, and the watercolor underpainting begun with a rust color for the sky.

It’s quite possible to alter this stage. Instead of watercolor, use another medium, like acrylic paint or gouache. You can even use pencil, though pencil shading tends to be much paler than it looks, producing a value range from white to only a middle-gray.

Once the underpainting is done, I seal it into the paper using two coats of acrylic matte medium. Oils cannot be painted directly onto paper—the paints soak in and look bad, and the chemical action of the paint will eventually disintegrate the paper. I dilute the acrylic medium (one part water to three or four parts medium) to minimize any brushstrokes that might give this layer a texture of its own; it should cover the paper as smoothly as possible. I use a wide, flat housepainter’s brush and cover the image in light strokes, as few as possible, ideally not brushing over any part of it more than once (at least for the first coat) so that the wet medium doesn’t get a chance to dissolve the watercolor and drag it along on the paper. If your underpainting is in acrylics, it won’t dissolve; it will, however, introduce textured brushtrokes that show up in the final oil. Gouache is very water-soluble, and I would be careful with my sealant, which I would not dilute.

I let the acrylic medium dry for the better part of a day so that water won’t be trapped under the oils.

The remaining job is to paint the same painting all over again, using colors this time. Oil colors are not all the same—some pigments are transparent and some are opaque. (A color’s transparency or opacity can be determined by testing the colors.) The basic idea is to use the transparent ones, although a bit of opacity can sometimes work to keep brushstrokes from showing too much. I usually use soft brushes for the same reason, often with synthetic (imitation sable) bristles brushes made for watercolor (real sable is too expensive and wears out too quickly). Painting thinly and smoothly, either by diluting the paint in the brush with a fair amount of oil painting medium or by brushing stiffer paint out to a very thin film, you eventually color in your whole painting. I usually keep my paint quite liquid. Sometimes I’ll paint an area of color and let it dry, then paint a different color on top, modulating the tone as I use less or more of it, always trying to let the underpainting show through. But even when the underpainting seems invisible, its darks and lights leave their mark.

The underpainting has been completed and sealed in. Note the sepia watercolor for
the lower wall and black elsewhere. Oils have been laid in starting from the left.

I often don’t plan my colors in advance, but try them out as I go. For me, the beauty of this technique is that it is completely forgiving: every poorly chosen color can be wiped clean, right down to the acrylic layer, and started over.

All three of my Grimms’ fairy tale books—Hansel and Gretel, Rumpelstiltskin (Dutton, 1986), and Rapunzel (Dutton, 1997)—were painted with this technique. If you try it, I hope you find it fun, or use it as a jumping-off point for another technique of your own.

Finished painting