Tuesday, October 27, 2009

Practical Colour Wheel

In colour theory there are many versions of the colour wheel.  Often the wheel is used to show the relationship of the primary, secondary and tertiary colours.  The primary colours are Blue, Yellow, and Red.  These cannot be mixed by any set of colours.  On the other hand, the secondary colours are Green (Blue + Yellow), Orange (Red + Yellow), and Violet (Blue + Red).

Although I want to keep this simple, I use the colour wheel below when I teach.

Practical Colour Wheel

Pardon the photographic distortions.  This wheel consists of 12 pigments (there are many more).  The purpose of using specific pigments is to give painters reference to colours they may use in their paintings.  You will notice that there are more than one Blue, Red, Yellow.  This implies that one could use a variety of primary colours.  More on that later. 

The colour pigments are set on a gray background.  This gray is mid way between White and Black.  The gray was mixed by combining two of the pigments on the wheel.  The mixture looks black and that mixture is placed on the left hand margin at the bottom.  Then adding white in increments we get 10 shades all the way to white.  The increments are shown on the left margin.  There are a number of purposes behind this arrangement.  First, each of the pigments will mix to a grey with their opposite pigment on the wheel.  Such pigments are called complements.  However, you should note that these are not exact complements and as a result form lively grays.  Exact complements do exist, but they are not common.  In addition, each paint maker's pigments will mix differently (especially student grades which are full of fillers).  Second, each pigment has its own value (the range between light and dark) and the value scale along the left margin gives a reference to where the pigment might fall.  Many people have difficulty with value when colour gets involved.  Third, the pigments on a gray background give some insight into the influence of a colour when surrounded by another colour.  Complements are the furthest away from each other on the wheel, something like opposite poles of a magnet.  I you want a pigment to pop, put its complement beside it.  Make it a little bit lighter and a hell of a lot brighter (less gray).  Lighter refers to the value, and brighter refers to its chroma.  On the wheel see this in action with the yellow.  Fourth, these are all high chroma pigments used on this wheel.  Earth colours are not shown.  They are grayed versions of the colours shown and can be mixed.  The corollary to this is that mixing colours will gray them.  More on this later.  Fifth, the right side of the wheel is the "cool" side and the left side is the "warm" side.  Be aware that each colour is relative to the other.  For example, Ultramarine is colder than Cobalt Blue.  The colours at the bottom of the wheel are the coolest.  Finally, this gives a plan for laying out the pigments on the palette (However you choose to lay out your palette keep it the same each time to facilitate blind mixing).

Here are the pigments starting from 12 o'clock;
Cadmium Lemon Yellow
Permanent Green Light
Viridian Green
Cerulean Blue
Cobalt Blue
Ultramarine Blue
Dioxy Violet
Mineral Violet
Alizarin Crimson
Cadmium Red Deep
Cadmium Red Light
Cadmium Orange

Yesterday turned out gray again.  Painting in the overcast pretty much every day this month gives good exercise but it is fatiguing.  This information on colour gives me a good review so that I will be able to paint in a sun key if and when it returns!

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