Pear on wood - watercolor painting
© Susan Harrison-Tustain

Demystifying Warm and Cool (Color Temperature)

Warm and cool is a vast subject but I have a great, simple way of teaching it:

Anything with red or yellow is basically warm. Anything with blue is basically cool.

But within the red  spectrum there are warmer or cooler reds. Just as there are warmer and cooler yellows within the yellow spectrum and it is the same for blue.

Take a look at a colour wheel. Look at a tomato red - this is a red that is leaning toward the yellow section. This is the warmest of reds. Then compare that to a red such as Alizarin Crimson. Alizarin Crimson is leaning toward the blue section. Purples are even more cool because they have more blue in them of course. You can see these 'reds' are more blue than the tomatoe red. So naturally Alizarin Crimson is a cooler red.  So now you can understand what I mean when I say "we have warm and cool within each colour section."

So naturally you can determine where - within each colour section - they fall by taking note how warm or cool they are in relation to the others either side of them.

That is what it is all about. Determining how warm or cool a color is, is about looking at it "In relation" to what else is around it. It is the same for all colour groups. Blue is thought of as being cold. Yes - it is cold when it is put up against red. But within the blue section there are warm and cool blues. The warm blues would be leaning toward red. A good example of a warm blue is Ultramarine Blue Finest.

Naturally the cool blues will be furthermost away from red. So use your colour wheel to help you determine where your colours are and whether they are warm or cool in relation to the colours you are using in your painting as well as on the colors on the color wheel.

The colour temperature of each colour you use on your painting
will be compared to the colour next to it.

Take yellow for instance: Aureolin is a cool yellow because it has a touch of blue in it. This cools it down. Compare that yellow to Indian Yellow which has some red in it. Indian Yellow is a warm yellow. So you could create a painting that is totally yellow. There will be warm and cool passages within it if you use a variation of yellows or mixes of yellows. But you can still create the impression of form because you can use warm and cool yellows to help you mould shape and substance.

The overall feeling/mood/colour temperature of the painting will be warm because you are using yellow (which gives the impression of warmth when we look at it). But you would describe your shapes and also focal planes by placing warm and cool yellows next to each other. Or if you need to give the impression of a gradual roll on a ball or petal for example - you would graduate the colours beginning with warm or cool and then as the subject rolls away into the background for instance, you would then gradually introduce a yellow of the opposite color temperature.

This is how you create form. Naturally you could also mix a tiny touch of blue or red with your yellows to alter them - but still allow the yellow colour to be dominant. This will also alter the colour temperature as you would expect. Warm your Indian yellow even further by adding a tiny touch of red. Cool another yellow down by adding a tiny touch of blue. You will see what I mean when you experiment.

It is generally true to say 'shadows are warm and sunlight is cool' when affected by natural (outside) light.  Generally when painting something affected by the natural light (outside or inside) - you would use warm colours to describe shadows. Make the shadows dance with warm transparent darks and throw in a little splash of red or orange - it makes the shadow look alive.

Conversely anything that is affected by the sky (which is generally blue - or a cool colour) - these things are cool. So the sunlit highlights are cool and the shadows are warm when outside or affected by natural light.

Inside lighting often creates a warm highlight and a cool shadow.

A good exercise is to paint a ball using warm and cool yellows. You will see how it automatically gives you form.

I hope that helps.

It is not an easy subject to grasp - but I find that once my workshop students understand there are warm and cool colours within each main colour - they can then see what I mean by looking at a colour wheel. It is a great idea to make a colour wheel of your own palette.

Learn more about my Watercolor Painting Technique in my Watercolor DVDs.

Learn more about how to paint in my Free Art Lessons.

Here comes the next article to the  series of notes on Susan's Watercolor palette.

Article 4 - Shadow color mixes
Shall I use Blue and Yellow or should I use sap green?

When mixing a shadow color you have many choices. I always use a small amount of blue in my shadow mix to create a realistic shadow.

But sometimes I use Sap Green instead. Why? Because it gives a softer look to my shadowed area. Sometimes I require a softer look. This is often in subjects such as skin tone.

Sometimes adding Thalo Blue to a skin tone can create a large shift in the color temperature. It may cool the shadowed area down too much. By using Sap Green instead (which of course has a small amount of blue in it) you will find your shadow mix will give you a more natural in final hue. But there are times when Thalo Blue is required and is ideal.

I hope you can see that there are no hard and fast rules. Each variation has it's applications and benefits.

It is interesting to note that using mix of blue and yellow gives you more choice in your balance of colour versatility. A slight dominance of blue or yellow will give you more color choices.

In your shadow mixes you can use Aureolin Modern or you could use Indian Yellow - depending on the warmth you want (the glow).
You also have the advantage of being able to adjust the ratio of the hues. You can make the
mix favour blue or favour yellow or balance out to give a more neutral final hue.

If we think about our complimentary colors - it stands to reason that Sap Green can be used in a shadow on a pink skin tone. Try these different permeatations. Create a color mix chart for your reference. You will be amazed at all that you will learn from this.

Trial the hues in fine washes to see what suits your needs. You can always adjust the Sap Green by adding a touch of Thalo Blue or one of the yellows too.

Want to read the other Articles?

Article 1: What Transparent pigments does Susan Harrison-Tustain use?

Article 2 - How to compensate for too much red in skin tone

Article 3 - How to paint shadow areas in watercolor?

Watch this space to read the next article: Article 5: How to paint a light skin tone