Color bias and the split-primary palette
What color bias is
Pigments are not pure. Cadmium Red Light reflects a lot of orange light as well as red, so it is a warm (orange-biased) red. Alizarin Crimson and Quinacridone Rose reflect some violet, so they are cool (violet-biased) reds. The same split exists for blues (Ultramarine leans violet, Phthalo and Cerulean lean green) and yellows (Cadmium Yellow Deep leans orange, Lemon Yellow leans green).
When you mix two primaries, their biases either agree with the secondary you want or fight it. Cool red (violet lean) + warm blue (violet lean) = clean violet, because both parents already contain violet. Warm red (orange lean) + cool blue (green lean) = a dull, greyed purple, because the orange in one and the green in the other are complements and cancel.
The split-primary palette
| Primary | Warm version | Cool version |
|---|---|---|
| Red | Cadmium Red Light / Scarlet / Vermilion Hue | Alizarin Crimson / Permanent Rose / Quinacridone Magenta |
| Yellow | Cadmium Yellow Medium or Deep | Lemon Yellow / Hansa Yellow Light |
| Blue | Ultramarine Blue (leans violet) | Phthalo Blue / Cerulean / Prussian (lean green) |
Plus Titanium White. From these you can mix a clean orange (warm red + warm yellow), a clean green (cool yellow + cool blue), a clean violet (cool red + warm blue), and every greyed version in between by crossing the biases. Student sets like the Winton and Magicfly boxes all contain a workable split primary set under their own names; the app’s set pages show which tubes they are.
Mixing clean secondaries
- Orange: Cadmium Red Light + Cadmium Yellow. Roughly 1 : 1; the red is stronger, so start with the yellow.
- Green: Lemon Yellow + Phthalo Blue (a dab) for bright spring greens; Lemon + Ultramarine for softer, slightly greyed greens.
- Violet: Alizarin or Permanent Rose + Ultramarine, about 1 : 1, lightened with white to see it. Cadmium Red + Ultramarine gives a brown-violet by comparison.
Calculated versions of these for Winton, Gamblin 1980 and Magicfly:
Burnt OrangeRecipe by paint setCoralRecipe by paint setLavenderRecipe by paint setTurquoiseRecipe by paint setMoss GreenRecipe by paint set
Mixing greyed secondaries on purpose
Most colors in a painting are greyed, so the “wrong” pairings are useful. Warm red + cool blue is the fastest route to the dusty violets of distant hills and shadowed fabric. Warm yellow + warm (violet-leaning) blue makes the olive greens of real landscape. Cool red + cool yellow makes a slightly greyed orange that sits better in skin than a cadmium orange ever will.
Dusty RoseRecipe by paint setOlive GreenRecipe by paint setPeachRecipe by paint setSage GreenRecipe by paint set
Finding the bias of your own tubes
Put a dab of each color next to white and pull a thin tint. The lean shows in the tint: a red that tints pink is cool, one that tints salmon is warm; a blue that tints towards sky is green-biased, one that tints towards lilac is violet-biased. Write it on the tube cap. In PaintMixLab the Calibrate feature does this measurement for you from a photographed swatch.
Questions
What is a split-primary palette?
Which red and blue make a clean purple?
Is Ultramarine a warm or cool blue?
