Thursday, September 5, 2019

Master Class: Ultramarine Blue – Cool or Warm?

Same ultramarine blue square in the center, but surrounded by different colors.
Each square of ultramarie looks a little different, depending on what's surrounding it.

Cool or warm?  Well, it's both.  Or can be.  In some ways, it all depends on what you were taught and what art instruction books you've read.  One book will call it warm; another, cool.  To avoid fistfights among artists, it's best simply to describe the color as a blue that leans toward violet.  Other blues, such as cerulean and manganese, lean toward green.  Cobalt is the one blue that doesn't lean either way, and I call it the “primary” blue.

Whether a particular color is cool or warm also depends on context.  Surround ultramarine blue with hot orange, and it might seem quite cool.  Surround it with a neutral grey, and—to my eye—it takes on a warm cast.

We often think of blue as being generally a cool color.  If we look at the spectrum, at one end we have the warm colors of red, orange and yellow.  At the other, we have the cooler colors of green, blue and violet.  Red, orange and yellow “feel” warm to us because our limbic cortex (the so-called “lizard brain”) associates these colors with fire, whereas green, blue and violet “feel” cool because we associate them with ice.

Interestingly, when we are talking about light, as in a spectrum, the temperatures are actually reversed.  In physics, red, orange and yellow have longer wavelengths which require less energy to create them and thus less heat; these are considered cool.  Green, blue and violet have shorter wavelengths which require more energy and thus more heat; these are considered warm.  In the colors of visible light, red is the coolest and violet, the warmest.  The light from a yellow candle flame has a color temperature of about 1850°K (degrees Kelvin).  The light of the clear blue sky toward the pole can be 15,000°K or greater.

If this last paragraph confuses you, don't worry.  It has nothing to do with painting.  Instead, when you pick up a brush, rely on your lizard brain to tell you what looks warm and what looks cool.  And remember, too, that the temperature of a color is influenced by the other colors around it.

Here are two paintings in which each sky is painted with a different blue.  What kind of day does each blue suggest to you?

Cerulean Blue
(Gamblin's cerulean blue has phthalo blue in it.)
Perched 14x11 Oil - Available

Ultramarine Blue
Stand Alone 12x9 Oil - Available


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