Cool yellows are those that have a green bias.
Cool yellows are those that have a green bias. It is useful to have one cool and one warm yellow in a split primary palette. When mixing with other colours, a cool yellow will make pure bright greens when mixed with a cool (greenish) blue, mid greens when mixed with a warm (purple) blue, neutral oranges when mixed with a cool (purple) red and mid oranges when mixed with a warm (orange) red. To neutralise, add purple.
Pure bright greens – Cool Yellow + Phthalo Blue
Bright Blues – Cadmium Yellow Light + Cerulean
Mid greens – Cool Yellow + Cobalt Blue
Yellow Medium (warmer yellow) at left. Cadmium yellow medium or hansa yellow medium are warm yellows. All yellows may seem warm to you; however, when mapped to the spectrum cadmium or hansa lean toward the orange side of the spectrum, while the “cooler” lemon or nickel titanate yellow leans slightly toward the green side. Hansa yellow is a good alternative to cadmium if you want to save money or wish to avoid cadmium. Both are opaque and hold up well in mixture.
Lemon Yellow or Nickel Titanite Yellow (cooler yellow) at right. Compared to warm yellows, cool yellows have less of a red component, with an ever-so-subtle shift toward the green end of the spectrum. Lemon yellow is the traditional cool yellow; however, the cool attributes of nickel titanate (a pigment which many artists are unfamiliar with) are more apparent than those of lemon yellow. It is also very opaque and holds up well in mixture. For more information on nickel titanate yellow, see Nickel Titanate: The Coolest Yellow.
Alizarin Permanent (cooler red) at left is a magenta-like color, leaning closer to the violet side of the spectrum. As a transparent color, it needs to be mixed with other colors in order to achieve adequate covering power. Traditional alizarin crimson is not lightfast and has a tendency to fade. Instead, use Gamblin Artist’s Colors alizarin permanent, a lightfast alternative to traditional alizarin crimson.
Cadmium Red Light (warmer red) at right, as compared to alizarin, leans toward the yellow and orange side of the spectrum. (Cadmium red medium is also warm, but is darker than cadmium red light.) Napthol red or red “hues” serve as alternatives to cadmium red should you wish to save money or avoid cadmium. Both have strong covering power and hold up well in mixture.
Phthalo Blue can also be seen as a warm blue, (if mixed with white to make it brighter = Cerulean Blue) at left is a relatively warm blue, as compared to ultramarine blue, at right. When mapped to the spectrum, phthalo shifts slightly toward the green side of the spectrum, while ultramarine is closer to the violet.
Straight from the tube, phthalo is fairly dark. It is one of those colors whose brilliance is heightened by the addition of white. Caution: Phthalo is so intense that it easily overpowers any mixture unless used very sparingly. Tip: Pre-mix phthalo with a little white, as shown here, to help distinguish it from ultramarine on the palette. Or try manganese blue, which is very similar to phthalo, but not nearly as strong.
Ultramarine Blue It is a strong, transparent blue with a subtle shift toward violet with a slight red undertone. Straight from the tube, ultramarine is fairly dark. It is one of the those colors whose brilliance is heightened by the addition of white.
With the six colors of the expanded primaries palette, you can mix colors very close to these neutral pigments; however, I like to include them in the palette because it is sometimes helpful for painters to have a “go-to” neutral in their palette. For a complete review of these neutral pigments, see Neutrals: Selecting the Right Neutral Pigment for Your Palette.
Yellow Ochre (left) or Raw Sienna (right) are not essential to the expanded primaries limited palette. Similar colors can be mixed with the primaries listed above. However, they are included here because they are effective colors for underpainting, especially in landscape. They are classified as earth colors, but I often refer to them as neutral yellows: if you mix violet with its complement, yellow, you can get a color similar to yellow ochre or raw sienna. As compared to yellow ochre, raw sienna is darker and redder.
Burnt Umber is not used as a generic “brown” color, but as a neutralizing pigment that can be used to dull down other color mixtures. Burnt umber is not a pure neutral, which would have no color or temperature bias at all. It has a slightly reddish tint, which is revealed when lightened with white, as shown above. It’s worth noting that when ultramarine blue is added to burnt umber, it can easily be converted into a cool neutral. In fact, when burnt umber is added in relatively equal parts with ultramarine, it makes a rich, chromatic black. Thus, ultramarine and burnt umber together are very capable of creating a range of cool or warm neutrals. For other “go-to” neutral pigments like burnt umber, see Neutrals: Selecting the Right Neutral Pigment for Your Palette.
What about greens?
The following information about greens is included for the benefit of landscape painters, but I don’t generally recommend including greens in the expanded primaries palette.
Viridian Green (left), Sap Green (center) and Chrome Oxide Green (right)
Although, there are many green pigments available, I find that my green mixtures are richer and more varied if I mix them from blues and yellows. That said, if you want to include green pigments in your palette, it’s advisable to have both a cool green (viridian) and a warm green (sap). If I were going to choose only a single green for my palette, however, it would be chrome oxide green.
Viridian Green is a relatively cool green, with less of a yellow component. It is particularly good for starting mixtures for the cool, dark green shadows sometimes seen in nature. It can also be warmed with yellow pigments. As a transparent pigment, it needs to be mixed with more opaque pigments in order to achieve covering power. When lightened with white, it reveals a mint-like hue.
Sap Green is a relatively warm green, with a shift toward the yellow end of the spectrum. As a transparent pigment, it may need to be mixed with other, more opaque pigments in order to achieve covering power. When lightened with white, it reveals a yellowy-olive hue.
Chrome Oxide Green is a good choice for a single all-purpose green. It can easily be modified with the yellows and blues in your palette and it holds up so well in mixture that it can handle being manipulated in a variety of ways. Out of the tube, it is a medium-value, somewhat neutral olive color. When lightened with white, it reveals a pale yellowy-olive hue.
Mapping pigments to the spectrum
To understand the cool and warm varieties of each pigment, it is helpful to see where each falls along the color spectrum. The magenta-like alizarin permanent, for instance, lies closer to the violet end of the spectrum, while cadmium red light is relatively warmer and leans toward the yellow end of the spectrum.