Helping you create correct colour and tone in painting
A crucial part of any painting, whether a pet portrait or abstract picture, is the relationship in colour and tone. Tone is the degree of light and shade in the picture, it exists independently of colour and can be measured on a scale which progresses from white to black. The sense of colour is created by the eye’s reaction to light of certain wavelengths; pure colour exists only as light, and as far as painters are concerned, all colours are also modified by tonal value. Pigments are not pure colours, and their range and behaviour is completely different, so painters can only hope to imitate the true colours of nature, by being adept at using their palette and visual tricks. Paintings are not mirrors, but abbreviations of reality, which make sense if key colours, tones and outlines have an internal logic and consistency.
Controlling light
Since colour and tone both rely on light, it is a great help if both the lighting of the subject, and the surroundings in which the painter works, is carefully controlled. Portrait painters quite often like to light their subject from one direction, enabling them to become familiar and easily predict the way the light falls on a face. Others will favour painting at specific times of day when the lighting conditions are an average quality, and shadow lengths are suited the painters style. An additional technique uses diffused light, which softens light and removes harsh shadows. To accomplish this, paper saturated with drying oil and allowed to dry can be used to cover windows, or pasted onto screens to create the desired outcome. If you use pale coloured paper it also has the benefit of harmonizing the colours in the subject. This is also a useful trick if you are having to paint in a room which is subject to full sun. By contrast, badly lit studios should be painted white to reflect as much light as possible back into the room.
Using a Claude glass
A Claude glass is a black-coated mirror used to assess the tonal relationships in a painting. Being black, it denies the colours in the subject reducing them to tonal values. This then makes it easy to consider the tonal relationships in the picture with any mistakes quickly being shown. You can build your own Claude glass by coating one side of a piece of glass with black paint or by placing a piece of smoked glass in front of a mirror. For landscape scenes, it is useful to have a Claude glass with a curved surface, this lets you to consider the whole scene at once.
Your palette
Most of all, it is critical that you know and understand the colours you use on your palette. This will only come with experience, but to be a great colourist an artist has to know how colours relate to each other, how each individual colour reacts when blended and how well it performs as tints. Expert colourists exploit preferred colour effects, tending to use a limited palette of colours but knowing and understanding them perfectly.
