Tuesday, August 19, 2008

Phthalo Blue -- warm or cool?

QUESTION: Hi, I Have a question about M. Graham phthalocyanine blue 15.3.
Is it a warm or cool blue? Thank you, Debbie

Most Phthalo Blue is PB15 and lean to the the greenish side of blue. In recent years some manufacturer (including M.Graham) have added an additional Phthalo's to their line that has been altered to have a more "purple" blue look. Look for the Phthalo Blue (RS) which stands for red shade.

From the manufacturers information I find that M.Graham's Phthalo Blue PB15:3 is altered to be more of a "true blue" and is a structural variant of Phthalo Blue PB15 (that produces more greenish tones. )

Here is a link to the M.Graham site with more technical information about their watercolors.

OK........that said, let's talk about warm vs cool.

Warmer or cooler is relative. It depends on the two colors you are comparing.

Red is warm and blue is cool... and its easy to see which is which.

All blues are cool when compared to any red. But when we compare several colors of the same hue (in this case blues) Manganese blue might be cooler than Antwerp blue and Ultramarine might be warmer than Cerulean blue. You have to visually compare them to see where they fit on the color wheel.
Because warm vs cool is relative to the two colors you are comparing, I find it's much easier to describe a color by naming the secondary hue it leans toward than to try to distinguish the difference by warmer or cooler. Example: New Gamboge is a orangish yellow and Hansa Yellow is a greenish yellow.

When comparing Phthalo blue(GS) to French Ultramarine Blue, Phthalo is slightly greener than Fr. Ultramarine blue which to my eye looks slightly purplish. So I say Phthalo is cooler, because on the color wheel it is closer to the coolest hue which is blue-blue-green.

The Fr Ultramarine is on the warmer side because it has a touch of red in it thus it farther away from the coolest color and closer to the warmer hues.

Now to answer your specific question: It is my opinion that M Graham's Phthalo 15.3 is very near a true blue. It has been altered so it doesn't lean toward a green hue as with the Phthalo Green Shade (GS) or a purple hue as the Phthalo Red Shade (RS). So I guess I'd say it is neither warm nor cool by itself. If we compared it to another blue I could tell you if it was warmer or cooler than the other blue hue.

I hope that is sufficient. It's not a simple answer.

Thanks for asking!



Sharon Hicks said...

Hi Susie ... here's the way I see it ... the Colour Wheel was devised by 'bending' the two opposite ends of the Colour Spectrum until they joined and formed a circle. The spectrum has red at one end (the Warm end), and Violet at the other end (the Cool end). When the Wheel is formed from the Spectrum, these two 'ends' sit next to each other.

Common usage by anyone not familiar with the actual origins of the Colour Wheel will surmise that since Violet (purple) sits next to Red on the wheel, then it must be warmer than the Blue which sits on its other side.

However, if we look beyond the wheel to the original source - the Spectrum, we see that this is not the case at all. Violet is a cool colour.

Therefore, Ultramarine blue would be cooler than Thalo blue, which is actually closer to the warm end of the spectrum, and therefore would be warmer than Ultramarine.

This question of Ultramarine vs Thalo blue has been widely debated and tossed around, and I suspect part of the questioning comes from the fact that reference is being made to just the colour Wheel, which is in itself a slightly misleading tool because of the manner in which it was formed.


Susie Short said...

Thanks for your comment!
I guess the debate will continue.
Which blue is warmer and which is cooler becomes a matter of personal interpretation. Undisputedly all blues are cool.

Colleen Reynolds said...

i love this debate. I would say that we should consider why we might care which blue is cool and which blue is warm? When we are trying to achieve atmospheric perspective on a 2-dimensional surface, I submit that warmer, darker pigment pops things forward, right? I think greener blues tend to recede, and are therefore cooler; And the more violet blues tend to seem closer. If you have ever gazed out over receding mountain ranges into the distance, you will know that the blues get darker and more violet as the ranges are closer to the viewing point. So when painting, I would opt to use ultramarine blue for the closer mountains, and a high value cooler (greener) blue for the very distant mountains. Phthalo tends to be a greener blue, but since it is also a very intense (bright) hue, it breaks the "cool recedes" rule. Just my 2 cents.