Warm and cool: how color temperature works in oil painting
Temperature is relative
Reds, oranges and yellows are warm; blues, greens and violets are cool. That is the easy half. The useful half is that within each hue there is a warmer and a cooler version: Cadmium Red is warmer than Alizarin, Ultramarine is warmer than Cerulean, Lemon Yellow is cooler than Cadmium Yellow. And a given mix is only warm or cool compared with its neighbour. A grey next to orange looks cool; the same grey next to blue looks warm. Mix for the relationship, not the label.
Warm light, cool shadow (and the reverse)
Under sunlight the lit side of an object is warm (the sun is yellow-orange) and the shadow side is cool (lit by blue sky). Under a cool north light or an overcast sky the lights are cool and the shadows comparatively warm. Under a tungsten bulb indoors the lights are very warm and shadows cool again. Decide which situation you are painting and keep it consistent: the fastest way to make a painting feel lit is to make every light pile lean one way and every shadow pile lean the other.
In practice: mix your light color, then make the shadow version by adding the complement and pushing the temperature the other way. A warm orange-pink skin light gets a shadow that is greyer and cooler (a touch of Ultramarine or Viridian in the Burnt Sienna), not just darker.
Light Skin ToneRecipe by paint setMedium Skin ToneRecipe by paint setPeachRecipe by paint setMauveRecipe by paint set
Temperature controls depth
Warm colors appear to advance and cool colors to recede. Atmospheric perspective is this effect at landscape scale: distant hills are cooler, lighter and greyer than the foreground because of the air between. Mix distance by adding your sky color to the local color — a little sky mix in the far trees cools, lightens and greys them in one move.
Sky BlueRecipe by paint setSage GreenRecipe by paint setLavenderRecipe by paint setForest GreenRecipe by paint set
Warming and cooling a mix
| To | Add | Watch for |
|---|---|---|
| Warm a color | A touch of its warm neighbour: yellow into green, orange into red, red into violet; or an earth (Yellow Ochre, Burnt Sienna). | Chroma may drop if the addition is a complement. |
| Cool a color | A touch of its cool neighbour: blue into green, violet into red, green into yellow; or white (which cools almost everything). | White also lightens; compensate with a darker cool if the value must hold. |
| Cool a shadow | Ultramarine or Viridian in dabs into the shadow mix. | Not black: black is dead rather than cool. |
| Warm a highlight | A little Lemon or Cadmium Yellow with the white. | Too much and it reads as yellow, not light. |
A temperature exercise
Paint a sphere twice from the same tubes: once with warm lights and cool shadows, once the reverse. Keep the values identical. The two spheres will look lit by different suns. Then paint a third with no temperature shift at all — it will look flat, however good the values are. That is why temperature matters.
Questions
What makes a color warm or cool?
Are shadows warm or cool in oil painting?
How do you make a color cooler without making it lighter?
