Artists have use gouache since the Middle Ages. This story explains the difference between gouache and watercolor painting. Painting techniques are also described.
Gouache is often referred to as opaque watercolor. Because of its thicker consistency, it is easier to control than watercolor. The detail, which can be reproduced, and the ability to make corrections has made it a popular medium for illustrations and architectural renderings. Its opacity also allows an artist to paint on colored media.
Fine art painters have used gouache for centuries. In fact, this paint has been used as far back as the Middle Ages, when it was used for manuscript decoration. Luminaries in the art world, who have used gouache, include Winslow Homer, Edward Hopper, Mary Cassatt and Paul Klee. Henri Matisse painted pieces of paper with gouache for his famous cut outs.
Gouache is comprised of pigment and a gum arabic binder. Unlike water color, which is transparent, gouache is opaque. Opacity is achieved by either adding white, which is referred to as body color, or by a heavy concentration of pigment.
You can combine gouache with other media, such as pencil drawing and watercolor. If you are currently a watercolorist, you don’t need to buy dozens of tubes of color, because you can mix your current watercolors and gouache. Even if you decide not to mix the two types of paint, a limited palette of basic colors will provide you with all the range that you need. Remember that Vincent Van Gogh claimed that with red, blue, yellow, black and white he could create more than 70 colors.
In combining pencil drawing with gouache, keep in mind that while this paint is opaque compared to watercolor, it’s not that opaque that it will hide dark pencil marks. If you initially do a sketch, keep the pencil marks light unless you want the drawing to show through.
Differences Between Watercolor and Gouache
There are very few differences between watercolor and gouache. Both paints are comprised of pigment and gum arabic, which is the resin that binds the pigment to the substrate. The pigments are essentially the same, although the pigments used in watercolors are milled more finely.
Both are water-soluble and can be rewet and reworked. The re-wetting characteristic of gouache allows you to rework areas that you have painted. By re-wetting the paint, you can also employ subtractive techniques, lifting off some of the color with a sponge, rag or damp brush. Subtractive techniques can be especially effective for illustrations on toned paper, in which you sponge off some of the applied gouache to let the paper show through as a value in the painting.
As I stated earlier, higher concentrations of pigment and the addition of opaque white pigment and fillers, such as chalk, make gouache opaque. The better quality paints use more pigment and lower amounts of filler. Of course, the pigment is most expensive component in paint formulations. That’s why higher quality gouache paints, such as Winsor & Newton’s Designers Gouache, cost more.
Watercolor paints are comprised of higher ratios of gum arabic to pigment and typically more transparent pigments are used. However, watercolors can be comprised of opaque pigments. When a higher concentration of gum arabic is used, paints are less viscous and flow more readily but take longer to dry.
Gouache Painting Technique
The transparency or opacity of the paint affects how a painter works. Because watercolor paints are transparent, you will work light to dark, gradually building up color and value, as you would if you were applying transparent glazes on an oil painting.
Conversely, when working with gouache, painters typically work from dark to light, first building the shadows of the illustration. In this respect, painting with gouache is much like painting with oil paints. And because you can paint a light opaque color over a dark color, you can produce a painting with much fine detail and texture than with watercolors.
Keep in mind that when you are covering one color over another you will need to mix your paint to a consistency thick enough that it will have the need hiding power. Opaque colors with enough hiding power will also allow you to make corrections, in the way that people had used White Out to mask mistakes in the old days when there were typewriters. Transparent watercolors are not forgiving.
Because gouache is thicker than watercolor paint, you will probably want to use a stiffer brush than the sable brushes that many artist use when painting with watercolors. The thicker consistency of gouache can hold a brush stroke, which allows an artist to achieve an impasto effect.
Lettering with Gouache
My friend and veteran sign painter, Joe Balabuszko, points out that because gouache has a thick consistency and is opaque, artists and calligraphers have lettered with it with brushes and calligraphy pens. The advantage of gouache versus calligraphy inks, is that the inks tend to be a little runny and are transparent. What’s more, gouache dries faster than ink. And with gouache, the range of colors is much more extensive.
When lettering with gouache, you may want to thin the paint from its thick consistency that it comes out from the tube. Just add distilled water a drop at a time to the paint until you achieve the desired result. In addition to adding water, some calligraphers also like to add a little gum arabic to the mixture. Once you have achieved the consistency that you want, load your pen with the thinned paint, transferring the gouache to the nib using a brush.
Creating an Impasto Effect
Applying excessively thick applications of gouache, however, is not advisable. These thick applications or multiple layers of gouache are prone to cracking. Cracking can occur if an under layer absorbs the gum arabic from an over painted layer.
If you want to achieve an impasto effect, commercial thickening mediums are available, such as Schmincke’s modeling pastes. Winsor & Newton recommends trying either gloss or matte acrylic mediums with their Designers Gouache paints. Before trying this on your paintings, it is best to Test, Don’t Guess for each color that you are using. Some mixtures of medium and paint may not be chemically compatible. Use any mediums with gouache sparingly.
Since thick layers of gouache are prone to flaking off, some artists work on rigid supports. While white and colored papers are usually used for gouache painting, primed rigid substrates, such as wood panels and Masonite hardboard, or canvas, can be used for painting. Primers differing in consistency from coarse to fine are available.
Gouache dries quickly. Sometimes dark colors dry as a lighter color and lighter colors can dry darker. The more you thin a color, the more the colors shift in value as they dry.
When painting one color over another, make sure that the base color is thoroughly dry before painting another color. Overpainting a color that has not sufficiently dried can result in the two colors mixing and becoming muddy-looking.
If you need to thin the consistency of gouache paint, always use distilled water to prevent any alterations of the color caused by minerals in your tap water. Painting with washes, which have been thinned with too much water, can also be problematic. The reason is that the gum arabic is spread out too thinly on the substrate. Consequently the gum arabic resin loses its binding power. Only the powdery pigment loosely remains and easily dusts off the surface. To correct for this, you can add gum arabic to your paint. Just keep in mind that by adding gum arabic the paint will become less opaque.
Should You Varnish a Gouache Painting?
Generally, a gouache painting does not need a protective coating, if it is framed behind glass. However, if you are concerned about the paint dusting off the substrate, you can apply a protective coating. Opinions vary regarding coatings. Most painters advise against varnishing with an oil-based product. Instead, some use an acrylic varnish. Others use a non-yellowing, satin-finish product, such as Pebeo spray gouache varnish. Just be aware that any type of coating that you use will very likely change the appearance of the painting. The finish is typically glossier. And the colors may darken. If you decide to try a coating, always test the product first. When you Test, Don’t Guess, you will avoid any unpleasant surprises.