Understanding Watercolor Pigments

Watercolor paint is pigment, the colored powder, held in a binder of gum arabic with a little glycerine or honey to keep it flexible. The pigment is what gives the paint its color, its transparency, and the way it behaves on the paper. Two paints of the same name can behave very differently if they are made from different pigments, so learning to read the label is more useful than memorizing color names. This guide explains the properties that matter and how to build a small palette that behaves predictably.

Reading a paint label

Serious watercolor brands print a pigment code on the tube or pan, such as PB29 for ultramarine blue or PR101 for a red iron oxide. The letters name the pigment family, blue, red and so on, and the number identifies the exact pigment. A paint made from one pigment is called single-pigment and mixes cleanly. A paint made from several pigments, often to imitate a costly color, mixes less predictably. When two brands share a pigment code, they will behave alike, whatever the romantic name on the label.

Transparency and opacity

Transparent pigments let the paper and any layer below show through, which is what gives watercolor its glow. Opaque pigments cover what is beneath them and are used for solid shapes and highlights. Most pigments sit somewhere between. Transparency is what makes glazing possible, so a palette for layered work leans toward transparent colors, with a few opaques kept for specific effects. The glazing guide shows how transparent layers build depth.

Staining and lifting

A staining pigment soaks into the paper and is difficult to lift, even when wet. A non-staining pigment sits nearer the surface and can be lifted with a clean damp brush to recover a highlight or soften an edge. The phthalocyanine blues and greens and many modern reds stain strongly, while the earths and some traditional pigments lift easily. Knowing which is which tells a painter how much freedom there is to correct a passage, and which colors to use when a soft, liftable sky is wanted.

Granulation

Some pigments are heavy and settle into the texture of the paper as the water dries, leaving a speckled, mineral surface. This is granulation, and it is prized for stone, weathered wood, sea and shadow. Ultramarine, the cobalts, the earths and viridian granulate; the phthalocyanines and most modern organics do not. Granulation is a quality of the pigment itself and cannot be imitated by mixing, so a palette that includes one or two granulating colors gains a texture the others cannot give.

Lightfastness

Lightfastness is how well a pigment resists fading in light. Most reputable brands rate each color, often in two scales, one for how much the color changes and one for how much it stains or bleeds. For work meant to last, choose pigments rated in the highest category, and avoid the traditional but fugitive colors such as alizarin crimson and some of the rose reds for anything that will hang on a wall. The rating is printed on the label and is worth checking before a large painting is made.

Building a limited palette

A small palette that mixes well is more useful than a large one that does not. A sound starting set includes a warm and a cool of each primary: a cool blue such as ultramarine and a warm blue such as cerulean or phthalo, a cool red such as a quinacridone magenta and a warm red such as a cadmium or a pyrrole, and a cool yellow such as a lemon and a warm yellow such as a cadmium or a new gamboge. Add two earths, a yellow ochre and a burnt sienna, a granulating green such as viridian, and a neutral such as a payne's gray or a burnt umber. Ten to twelve pigments cover almost any landscape, and because each is single-pigment, they mix into clean secondary colors.

Mixing clean secondaries

Clean secondary colors come from choosing pigments that sit near each other on the color wheel and that are each single-pigment. A warm yellow and a warm red make a bright orange; a cool yellow and a cool blue make a clear green. When a mix turns muddy, the cause is usually that one of the two pigments already contains the third primary, or that the two are far apart in temperature. Mixing from single-pigment paints, rather than from convenience mixes that already combine several pigments, keeps the secondaries bright and the grays controlled.

Whites, blacks and neutrals

Watercolor has no true white paint in ordinary use; the white is the paper, and it is reserved rather than applied. An opaque white is kept only for small corrections or highlights, and it dulls the paper where it is used, so it is applied sparingly. Black is rarely used straight, because it deadens a mix; a dark neutral is better made by mixing a warm and a cool of the palette, such as burnt umber with ultramarine, which gives a dark that sits in the picture rather than on top of it. Learning to mix neutrals from the palette is a mark of a painter who understands the pigments.

Warm and cool of each hue

Every hue has a warm and a cool version, and the choice between them changes a mix. A warm red with a warm yellow makes a fiery orange; a cool red with the same yellow makes a duller, brownish orange. A cool blue and a warm yellow make a clean green; the reverse gives a grayer one. Learning to think in warm and cool, rather than in fixed color names, is the step that turns a palette into a working tool. The materials section places pigments beside paper and brushes, and the subject guides show the palette in use on sky, water and foliage.