Understanding colour temperature in landscape painting

Why temperature does more work than value

Most painters learn early to organise a landscape by value — light, mid-tone, dark. It's sound advice, and it will get you a readable painting. But stand in front of a real view with a brush in your hand and you'll notice that value alone gives you a flat, slightly dull result. What makes a scene feel like a place, with air in it and sun on it, is colour temperature.

Temperature is simply the warmth or coolness of a hue relative to its neighbours. A red is warm next to a blue, but cool next to an orange. Nothing is warm or cool in isolation; it's always a comparison. That's good news for the landscape painter, because it means you can suggest blazing sunlight without a single tube of bright orange — you just need something cooler nearby.

Learn to see temperature and you'll find you can hold a viewer's eye, push a hill back three miles, and make a wet Cumbrian afternoon feel genuinely damp. It's the most useful tool in the box, and the one most often left there.

Warm light, cool shadow

The oldest rule in landscape painting is that sunlight is warm and shadow is cool. On a clear day it holds up beautifully. Sunlight arrives filtered through atmosphere and reads golden or amber; the shadowed side of a wall or a tree receives only skylight, which is blue. Paint the lit planes with a warm mix and the shadowed planes with a cool one and the form will turn convincingly in space.

The rule bends, though, and you need to know when. On an overcast day the light is cool and diffuse, and shadows are barely darker than the light — sometimes subtly warmer, because light bounces off warm ground and grass into them. In the last twenty minutes before sunset, shadows can go violet, green-grey or even a warm brown, depending on what's reflecting into them. Always paint what you see rather than what the rule promises.

Reflected light matters enormously here. A white cottage wall in shade isn't grey-blue all over; the lower portion picks up warmth from the path, and the underside of the eaves may bounce a little green from the hedge. Those shifts are small in value but big in temperature, and they are what stop a shadow looking like a hole cut in the canvas.

Distance, atmosphere and the temperature of air

Temperature is your most reliable depth cue after scale. Because we look through more atmosphere at distant objects, they shift toward cool — usually blue or blue-violet in Britain. A near tree trunk might be raw umber and burnt sienna; the same species a mile off will be closer to a soft blue-grey with only a whisper of its local colour left.

Two cautions. First, aerial perspective also lightens and softens, so push temperature and value together. Second, the shift isn't always cool: a distant ridge at sunset, lit directly by low sun, can glow warmly pink or apricot while the middle distance stays cool. That contrast is one of the most beautiful things in landscape painting, and it only works if you've kept the middle distance genuinely cool.

A useful habit is to decide early where your coolest colour and your warmest colour will sit, then make everything else fall between them. Your warmest note might be a sunlit stone wall in the foreground; your coolest, a band of shadowed woodland or a distant hill. Once those two anchors are set, every other mix has a job to do.

Mixing warm and cool greys

Most of a landscape is grey of one sort or another, which is why grey mixing trips up so many painters. Tube greys and black-based mixes flatten everything. Instead, build chromatic greys from complementary pairs and then lean them warm or cool:

• Cool grey: French ultramarine with a touch of raw umber, or cerulean with alizarin crimson. Add white sparingly — it cools and desaturates fast.
• Warm grey: burnt sienna or transparent red oxide with a little ultramarine, or yellow ochre with a violet. These hold their warmth even when lightened.
• Green greys: viridian or terre verte with alizarin, invaluable for British foliage and damp stone.
• Never use black neat for shadows. Mix a dark from ultramarine and burnt sienna and you'll get a shadow that still breathes.

Keep a scrap of paper beside you and lay out a row of five greys from your warmest to your coolest before you start. It takes two minutes and saves an hour of mud.

Reading the light through a British day

Our weather gives us a superb range of temperature problems. On a bright June morning, shadows are cool and blue, greens are warm and yellow-shifted where the sun catches them, and the whole scene is high in contrast. By mid-afternoon the light has warmed and lowered; greens cool slightly and shadows fill with bounce light. Under a flat grey sky, the light is cool and the shadows are weak — the painting then depends almost entirely on small temperature differences and on the variety of your greens.

Coastal light is cooler and cleaner than inland light, and Scottish or Welsh hill country often gives you a violet-blue distance that near-ultramarine can barely reach. Fenland and the chalk downs give warmer, hazier horizons. Sketch the same view in three different weathers and you'll learn more about temperature than any book can teach you.

Outdoor sketching drills that build the habit

Take a small board, a limited palette — ultramarine, burnt sienna, yellow ochre, a red, a green, white — and a set of postcard-sized sheets. Work fast and often.

• Ten-minute temperature studies: one tree, two mixes only. Warm light, cool shadow. No detail.
• Three-value sketches: block the scene in three shapes, then make sure each shape is a distinct temperature as well as a distinct value.
• Squint and compare: squint at the view, then at your sketch. If your warm and cool read as separate families, you're winning.
• Same view, three times of day: morning, afternoon, dusk. Note the temperature notes in the margin.

Do this for a season and you'll stop seeing a green field and start seeing a warm yellow-green in the sun, a cool blue-green in the shade, and a soft blue-grey hill beyond them — which is, after all, what's really there.