gouache & bodycolor

We get a hint of what's involved in the use of gouache (pronounced "gwash") by considering the origins of the name: it comes from the Italian aguazzo, for "mud."

Like Italian, gouache is a continental European invention; it was transplanted to England via French and Italian decorative and landscape painters in gouache, working in London in the 18th century. Like mud, gouache is wet and opaque. The topic is also muddied by different definitions of what gouache is or how it should be used. And many artists react to gouache in watercolors as if it really were mud — it's probably the most vehemently controversial technique in watercolor painting.

The technique has a long and complex history. It first appears in the decorative and pictorial embellishments to medieval illuminated manuscripts. The earliest modern examples are nature paintings by the 16th century German artist Albrecht Dürer (the fur on that famous hare, for example), and continuing in a series of paintings by Gaspard Dughet (1615-1675, called "Poussin" in England). It reached a prolonged high point in the 18th century, particularly in France, in decorative works by the French painter François Boucher (1703-1770). Gouache was probably introduced to England by painters with French ancestry, such as Joseph Goupy (1689-1763) who was drawing master to the family of George I, or by painters who became influential in England after a career on the Continent (such as Marco Ricci, 1676-1729, Francesco Zuccarelli, 1702-1788, or Charles Clérisseau, 1722-1820). From around 1740 English topographical artists used the method frequently; Paul Sandby in particular handled bodycolor with considerable skill and variety, and knew Goupy, Zuccarelli and Clérisseau personally. By that time, use of gouache or bodycolor on the Continent had begun to decline into purely decorative painting on fans, screens and theatrical scenery. The Swiss topographical artist Louis Ducros (1748-1810), working in Italy on large format gouache and watercolor paintings, continued almost alone to use the medium in fine art works. In the 1830's the method was revived by several Victorian watercolor artists, who used it until the end of the century. 

First, some distinctions. The method of mixing watercolor pigment with an opaque white pigment in a watercolor vehicle (made with gum arabic) is traditionally referred to as gouache. The method of mixing concentrated watercolor pigments with a vehicle that is made with fish gelatin (isinglass jelly) or animal gelatin (size) — without the addition of any white pigment — is traditionally called bodycolor (or distemper in England). However, the two terms are sometimes confused or used interchangeably, both in historical writings and current usage: some "designer's gouache" paints are made with concentrated pure pigment in a watercolor vehicle, without any added white pigment.  

The core meaning in all cases is that gouache or bodycolor is an opaque watercolor paint. This arises from six properties that cause gouache technique to be different from transparent watercolor technique:



• Gouache has a much thicker paint layer, and beyond the minimal amount of paint required to completely cover the paper or support, the thickness of the gouache paint layer does not affect the apparent color. Unlike transparent watercolors, gouache can be painted on a white or tinted support, with little or no difference in the finished color appearance.

• Colors must be lightened by adding white pigment, as in oil paints; they are not lightened by dilution to show more of the white paper, as in transparent watercolors.

• Paints are not applied in glazes or tints (unlike oils and watercolors, where glazing one color over another is a common technique).

• The applied paint is not absorbed into the paper but remains on the surface in a thick layer, allowing for limited textural effects created with brushstroke variations in the surface of the paint (although gouache will crack when dry if laid on too thickly in "impasto" layers). Transparent watercolor is sometimes described (somewhat inaccurately) as "a stain on the paper," which only means that textural effects in watercolors are limited to pigment granulation, water based diffusion such as blossoming, brushwork, or the pinhole texture of rough finished papers made visible by unevenly applied paint.

• Gouache creates flawless, flat color areas, which are more difficult to attain in watercolors. Because of the concentration of pigment and filler, gouache is resistant to water induced variations in paint appearance such as blossoming or blooming.

• The paint covers all paint layers below it, so that the method of painting is more direct, especially for complex patterns such as leaves or flowers. In transparent watercolors, a dark background must be carefully painted around the white flower in front of it, and painters normally work by laying darker colors on top of light; but in gouache the background can be painted first, then the flower directly on top of it (just as in oil painting), and lighter colors can often be layered on top of dark if that is a more convenient way to work.

Many of these points have caused gouache to be especially popular with architectural or commercial artists; some types of gouache paints are even labeled "designers' colors." The flat color fields photograph and reproduce very well, which makes gouache ideal for photoreproduction artwork. Gouache does not undergo a chemical change when dry and therefore can be rewetted and reworked, just like watercolors. And the more direct painting method and rapid drying times mean that a project can be completed relatively quickly.

Because gouache is nearly ideal for illustration and photoreproduction, manufacturers have designed lines of gouache paint with more brilliant but fugitive colors (especially in the red, magenta and violet range). These colors display or photograph very well, and commercial art is not intended to last. But this means artists who use gouache for permanent artworks must exercise caution in their choice of paints.

This is not easy to do. Even reputable manufacturers may not include pigment information or lightfastness ratings on the paint tubes, which complicates the task of avoiding fugitive colors. You must write to the manufacturer, or obtain a marketing brochure, to get the pigment or lightfastness information. Be sure that the lightfastness information is "in conformance with ASTM-D5067," the labeling rules for watercolor paints. If this assurance is lacking, the tests may not be interpretable or trustworthy. If no lightfastness ratings have been done, rely on the pigment evaluation in the guide to watercolor pigments.

The similarity between oil and gouache painting techniques allows watercolor artists who use gouache to emulate the free, vigorous style and strong contrasts of value that are possible with oils. However, gouache will crack or discolor if applied too thickly, so texture is created by the surface of the paint, not its thickness. Standard watercolor brushes can be used, although the same brush should not be used for both gouache and watercolors if the gouache is made with a white filler. However, because gouache is relatively thicker than transparent watercolor, a stiffer synthetic or acrylic brush may work better than a natural hair brush.

Gouache paintings are typically done on hot pressed papers or smooth art boards, since the paint imparts most of the texture and these surfaces help to create a perfectly flat paint film. Tinted papers are also more commonly used, since the tint is easily covered wherever desired, but lends a pleasing background hue in unpainted areas.

In practice, because the opacifier or white pigment dilutes the colored pigment, more pigment must be added to compensate, so both white pigment and a higher concentration of pure watercolor pigment may be necessary to get opaque paints across the full range of hues in a paint line. (Some watercolors, such as chromium oxide green (PG17) or venetian red (PR101) are sufficiently opaque without much change from the watercolor formulation). Some transparent pigments cannot be made opaque without filler. Very dark pigments, such as blacks and browns, must be made opaque through pigment concentration, since white filler would lighten the value. Finally, white pigment is necessary to bring out the full vibrancy of a dark, strongly tinting pigment such as phthalo blue (PB15) or dioxazine violet (PV23), which would merely appear black at higher concentrations. Even so, the concentrated pigment type of gouache is often better for fine art purposes. To my knowledge, only M. Graham (Artists' Gouache), Holbein (Designers Gouache) and Winsor & Newton (Designers Gouache) make gouache in this way; other brands rely primarily on white pigment.

Gouache is usually made with the same gum arabic vehicle as ordinary watercolors. A good quality gouache contains the following ingredients:

• dry pigments
• distilled water
• inert pigment (blanc fixe or precipitated chalk)
• binder (gum arabic)
• plasticizer (glycerin and/or dextrin)
• preservative

Sometimes a wetting agent, such as ox gall, is also added to improve milling or handling characteristics. Dextrin, a syrupy medium derived from heated corn or potato starch, is also sometimes used to make the texture of the paint creamier.

With the exception of the impermanent, "brilliant" pigments mentioned above, the pigments used are the same as those found in transparent watercolors. (However, pigments that are ordinarily transparent in oil or watercolor can act as opaque colors in gouache, and often yield somewhat different color effects.) Gouache has a greater proportion of binder to pigment than is found in transparent watercolors, so gouache produces a continuous paint film of considerable thickness. For this reason, gouache pigments are not ground as fine as watercolors, because gouache is typically not used in thin washes or tints — instead, it is diluted with white paint.

Prior to the Victorian Age, the primary additives used to create gouache were lead carbonate (PW1), precipitated chalk (artificial calcium carbonate), or blanc fixe (barium sulfate). The major drawback to the lead filler is that it turns black on exposure to sulfur, so chalk or blanc fixe were used instead. Both fillers were augmented in 1834 when Winsor & Newton introduced an especially dense and finely powdered grade of zinc white, made specifically for watercolors and marketed under the name "Chinese white." Gouache or bodycolor was widely used in 18th century watercolors, and with the advent of Chinese white became the dominant watercolor method in Victorian watercolors. (Nowadays titanium white produces the cleanest, most opaque and most lightfast tints and color mixtures.)

winsor & newton designers' gouache

These paint swatches show representative paints from Winsor & Newton's designers' gouache color line. These paints are only partly opaque when tested against the opacity bars on white paper, but in general have good hiding power and mix well with one another.

Gouche paints show limited activity wet in wet, but almost no blossoming when rewetted. This is usually a good thing, since the lack of reactivity to water or rewetting is what gives gouache paintings their flat, even color. But this highlights the relative similarity between gouache and oils, in contrast to transparent watercolor textures.

gouache diffusion (top) and blossoming (bottom)

As the figure shows, there is very limited mixing of the colors as they diffuse wet in wet (top), and almost no blossoming when pure water is painted onto the colors when they are still moist (middle). Even when a pure black color is painted wet in wet and then pure water is added as it dries (bottom), the result is smoothly graded color density, rather than the sharp irregularities common in transparent watercolor. (All these examples use Winsor & Newton's designer's gouache.)

Gouache can be used in combination with transparent watercolor in three ways:

• Pure gouache white can be applied as highlights or details to a transparent painting, for example to draw the filaments of a spider web over a shadowed background, or to tip in the white of a gull's wings against a stormy sky. Colored gouache can be used in the same way, to accent forms or clarify details.

• Pure chinese white can be applied as a ground over the entire paper that is then completely painted over by transparent watercolors. Several 19th century English watercolorists, such as John William North, coated the entire support with a ground of chinese white before painting.

• The entire silhouette of a figure or dominant object can be defined in white, then the flesh tones, clothing or surface colors painted over this foundantion in transparent colors, with the rest of the painting completed in transparent colors on untreated paper. This makes the figure or object appear more dominant or more brightly colored than the rest of the image.

Purists object to all of these techniques. In the purist view, the preferred method to create highlights is either to reserve the white (by the use of a blocking agent, such as resist or tape) or to remove any color with a sponge or knife to reveal the bare paper underneath. And the last method is flatly rejected as a method to turn transparent watercolors into something they're not — something indistinguishable from oil painting.

Gouache works well when combined with most brands of transparent watercolors, but here again it is not without problems. When overpainting in layers, some paints will bleed through or "stain" the layers painted over them; the extent of this staining depends on the pigments underneath and above, and the thickness of the paint layers. Experience or preliminary testing will indicate the problem paints and painting methods.

Because of the opacifying additives, gouache also has a tendency to appear whitish or to have a matt finish. The Victorians controlled this with a very quick, light application of moderately diluted gum arabic solution as a varnish. Modern paints may blur or bleed under this treatment. Sometimes spray synthetic varnishes will work, and sometimes not. Always test the coating on a painting sample to make sure the gouache does not react badly to the treatment.

Gouache can be made more water resistant by adding small amounts of an acrylic binder or acrylic matt medium. However, gouache should not be used with acrylic paints: some colours react chemically and may change hue or turn lumpy when mixed with acrylic chemicals; mixing with acrylic medium also turns the finished gouache colors glossy.

Gouache also will crack if applied too thickly or in too many layers; or if the paintings have been rolled up rather than kept flat. And if gouache is applied in several layers, the dry coats underneath will tend to draw moisture and vehicle from the fresher coats, causing them to crack or flake. This can be remedied by adding gum arabic to the subsequent layers, but this in turn can increase the transparency and surface glossiness of the dried paint.

In other respects, gouache paintings should be handled just like finished watercolors: matted and framed under UV shielding glass or plastic.

Gouache is commonly available in standard watercolor "large" tube sizes (14-15ml, and occasionally 30ml). It is not available in dry pan form. Tube paints have an average shelf life of 3 to 5 years. Although attempts have been made by several manufacturers to produce gouache in small (4 oz.) jars, evaporation remains a problem. The binder and pigment may also separate (the pigment settles to the bottom) in jars. Subsequent settling of the pigment results from the increased amount of gravity on the larger mass of paints found in jars. Tube paints, used up within a few years, remain the optimal packaging solution.