The colloid matter is usually combined with the pigment, which may be made up in dry cakes or moist in tubes. More rarely, it is dissolved in water, and the brush is dipped in the solution before taking up the colour. Varieties of gum are the most common colloids, the usual being gum arabic, derived from the acacia. Pastes of flour or rice, egg yolk or white, animal size or the casein of cheese have also been used. The binding medium may also include a wetting agent such as ox-gall or a thickener such as gum tragacanth, starch or dextrin, and, nowadays, a fungicide and bacteriacide. Further agents may be added while painting; glycerin to retard the drying of the pigment, alcohol to accelerate it.
The first proper list of watercolour pigments was given in Edward Norgate’s Miniatura or the Art of Limning (c. 1630), written for Sir Théodore Turquet de Mayerne and later widely circulated. Norgate listed the varieties of white, yellow, red, green, blue, brown and black—24 in all—that could be bought in apothecaries’ shops for artists to grind themselves. These pigments were derived from natural materials and were to be combined with gum arabic and ‘sugar candy’ to ensure that they dried ‘smooth and even’. Subsequent writers have refined Norgate’s recipes and enlarged his range of pigments without altering the basic principles, and the process remains essentially the same today. The establishment of artists’ colourmen in the large European cities and the rapid expansion of pigment choice during the 18th century did little to change working practices. Artists long preferred to grind their own colours and even now often choose to work with a basic set of about 15 pigments rather than use all the hundreds available.
The production of colours in small hard cakes, begun in England by the Reeves firm c. 1780, was, however, a crucial development. Portable watercolour boxes, available from the early 18th century, were readily adapted to these and developed into the boxes with pans or cakes of colour used from the 19th century onwards. Tube colours, containing additional glycerine as a plasticizer, are currently preferred by most professionals. Modern pigments are generally synthetic and, being very fine-ground, produce smooth and regular washes rather than the granular effects so vigorously exploited by earlier artists; however, they are also exceptionally pure and lend themselves to a wide range of colour mixes. Colours are mixed on watercolour palettes or on china plates or saucers.
So that washes flow steadily over the paper without running out of control of the brush, the studio watercolourist generally works on an easel or drawing board inclined at an angle of 5° to 10°. The paper, first moistened and stretched, is mounted over a frame or board and held tight and smooth. If working outdoors on a large scale, the artist may use a folding easel. Brushes must be strong but pliant and should not abrade the damp paper. They should readily twist to a fine point when required (traditionally this was done in the mouth). Early Chinese painters turned to deer, fox, rabbit and even to rats’ whiskers or kingfishers’ beaks for appropriately fine hairs. More recently, expensive brushes have been made from red sable, more economical ones from camel-hair. Artists in the 18th and 19th centuries used broader brushes than those now preferred. Early brushes were set into quill handles; from the mid-19th century onwards these were replaced by wooden handles with nickel or aluminium fixings.
In its pure form a watercolour is made with pigment and colloid, with water as the only vehicle, so that it is transparent. The colour sinks into the paper without completely hiding its tone. Watercolourists have always exploited their papers, sometimes choosing textured or granulous papers to retain pockets of colour, or toned papers to modify the colour values, sometimes leaving patches of paper bare to act as highlights. Pure watercolour is therefore applied over white or pale buff paper. Artists continue to prefer fine, handmade rag papers rather than machine–made varieties.
Watercolour may be applied in a broad wash, laid down with a full and well-soaked brush, or in separate brushstrokes or stipples with relatively little water. The swift application of a flat or tonally gradated wash is a fundamental skill. Additional washes may be laid over the initial one, sometimes while it is still wet. When using transparent washes, pale ones are applied first and the darker ones laid over them; each preceding wash, and the paper beneath, will contribute to the final effect. A wash may be smooth or broken. The latter effect is achieved by dragging a lightly damped brush, charged with dry or almost dry colour, on its side across the paper so that patches of pigment remain trapped in the surface recesses. To develop or alter effects, damp colour may be lifted, ‘stopped’ or blended by a variety of methods. Rags, blotting paper, india-rubber, bread pellets, a brush handle, penknife or finger nail have served widely to remove colour and to expose the paper. Since the medium is resoluble when dry, more radical transformations may be achieved by wiping over the entire watercolour or even holding it under a tap; other washes may then be floated over it or dabs of stronger colours run in.
Watercolour may be made opaque by the addition of a further agent. In this form it is called Gouache or, traditionally, bodycolour. The extra ‘body’ is usually Chinese white, an opaque white originally based on lead and later on oxide of zinc, which is added to all the colours. Barium sulphate or precipitated chalk may also be added to the pigments as opaque extenders. To obtain the greater opacity and flexibility required of gouache, both pigment and glycerine are used in larger proportions than for transparent watercolour. The medium is favoured by designers and illustrators, who need to achieve flat, even fields of colour, and also by miniature-painters, who appreciate its possibilities for a jewel-like texture. Although it will not leave the paper visible, gouache is often applied to toned papers. Whereas in pure watercolour, tonal gradations must be anticipated, and a dark one can only be reduced by thinning down or washing out with water, with gouache a pale colour may be laid over a dark. Gouache can be used exclusively or combined as a heightening agent with transparent watercolour; the latter requires great skill and is rarely entirely satisfactory. Some artists prepared their paper with white gouache and then painted over it in transparent watercolour, thus producing great brilliance of tone, a result similar to that achieved by oil painters—for example the Pre-Raphaelites—when painting over a pale ground.
© 2009 Oxford University Press