Asked about the difference between watercolour and gouache, my students often answer, ‘Gouache paintings are opaque, chalky and watercolours are transparent’. In theory, yes.
Main differences
The same pigments are used in both media, but gouache particles are larger. Both paints typically have four ingredients – the pigments (natural, synthetic, mineral or organic), gum arabic, a binder that helps the pigments adhere to the surface as you work, additives and solvents.
The ratio of pigment to water with gouache is much higher and an additional white pigment (usually chalk or even acrylic) is also present. This gives gouache a ‘heavier’ texture and it’s less flexible than watercolour. Many artists see this as an advantage and use it very opaquely (less water added) but if used too thickly it is prone to cracking. A rigid support or heavyweight paper helps, but experience will teach you how to avoid this when using gouache in an opaque way.
Gouache is perfect for large areas of flat colour. It is important to mix enough colour before application as it is virtually impossible to feather, mix or ‘tie-in’ another flat wash of the same colour to give a seamless opaque passage of paint. Such even painting quality makes gouache paintings appear heavier, but this I believe is a redeeming feature of the medium, not a disadvantage.
If more water is added to gouache to make the paint more transparent, glazing techniques akin to watercolour are achievable. Interestingly, watercolour will always dry lighter than the colour first mixed – gouache won’t. However, if you add white to gouache there is a tendency for the paint to lighten as it dries.
It would appear, then, that gouache is actually more versatile than watercolour, but many of the techniques used with gouache are possible if you add white (Chinese, permanent or white gouache) to watercolour.
Traditionally, watercolour paintings are created from a succession of transparent layers to create depth in tone in paintings. The more layers you apply (especially using less water in your mixes), the darker the passage of paint will be. This formulaic way of working without the use of body-colour (continually working light to dark with thin glazes) can be seen as a very restrictive process.
Glowing Autumn Light – Buttermere, The Lake District, gouache, watercolour and pastel on Canson Moulin du Roy 140lb (300gsm) HP 100 per cent rag watercolour paper, (38x53.5cm).
The initial washes were very transparent wet-in- wet watercolour overlaid with more opaque and semi-opaque layers of gouache to add depth, especially to the shadow areas. Soft Rembrandt pastels were used to give the final colour notations in several areas for the all-important highlights.
Student or professional quality?
The quality of pigments varies from brand to brand. Students’ watercolours are inexpensive but the quality of saturation is often not as bright as the professional ranges because they contain lower-grade pigments and, quite often, more additives. Artists’ colours are made with higher-grade pigments and thus a little bit more expensive, but they give better results.
You can buy watercolours and gouache in pans or in tubes. Pans fit into paint boxes and are a great choice for many artists who like to travel light. Personally I prefer tubes as I find them quicker and easier to use for mixing colours – especially for large-scale work, on site or in the studio.
My choice for watercolour or gouache paints now is the Van Gogh range by Royal Talens; the colours are so highly pigmented that colours just radiate and a little goes a long way, so they last for ages. The tubes are clearly labelled so, when in the throws of painting, I can quickly identify the colour I need.
Bright Blue Ocean – Church Bay, Anglesey, Royal Talens Van Gogh gouache, Royal Talens watercolour and Rembrandt soft pastels on Canson Moulin du Roy 140lb (300gsm) HP 100 per cent rag watercolour paper, (38x53.5cm).
Layers of watercolour and gouache were applied to build depth, with less water added to the washes as the painting progressed. The final layers were light on dark and dark on light gouache, followed by soft pastels.
Mediums and supports
A number of acrylic mediums can be added to gouache but before adding them to your palette, test each colour by mixing it with the medium, then leave it to dry and observe what happens – there may be reactions such as granular or gelatinous effects. If you wish to maintain the characteristics of gouache paint, keep the addition of medium to a minimum. Or do as I do and experiment to see which results you like best.
Interestingly, acrylic mediums will increase the transparency of mixes with gouache. Gloss medium thins the paint film quite considerably, with very interesting effects. Water resistance with gouache can be achieved by adding small amounts of acrylic matt medium to your colours, and marbling effects are possible when adding a semi-transparent wash over a previous wash of colour mixed with acrylic matt medium.
Acrylic gesso primer can be used as a base layer with either watercolour or gouache. Royal Talens have three – Amsterdam Fine, Medium and Coarse gesso, which create great textures on which to paint.
Paper is considered the first choice for most artists as a support – but what kind? There are so many that it would be hard to list them all. My number one choice would be Canson Moulin du Roy 140lb (300gsm) Rough, Not or HP 100 per cent rag watercolour papers.
The Last Snows of Winter – Wharfedale, West Yorkshire, gouache, watercolour and Derwent XL Charcoal and Graphite on Canson Moulin du Roy 140lb (300gsm) HP 100 per cent rag watercolour paper, (38x53.5cm).
Primarily this painting is all about the complementary colours of red and green. Fluid washes of very bright greens, pale cerulean blue and crimson mixes were applied with big brushes, keeping the washes loose and free. As the painting quickly developed I was mindful to keep the translucency of the washes of watercolour and gouache rich and clean. Deeper washes, particularly for the bracken in the foreground, were mixed using stronger glazes of gouache – the opacity of those washes being a direct contrast to translucent washes of watercolour in the distance. Finishing touches using Derwent XL Charcoal and Graphite colours complement the opaque passages of paint.
Mixed media
One of the most exciting ways to use watercolour and gouache is in the same painting with other media. Gouache works better over watercolour. Watercolour can be applied very successfully over oil pastel; because oil and water don’t mix, oil pastels act as a resist, allowing the watercolour to sit beautifully between the pastel marks. It’s possible to work like this in layers.
Gouache is not poster paint!
While poster paint may appear to be similar to gouache, it is not. Poster paint is regularly made with much cheaper pigments and binders, and should never be considered a substitute for gouache.
GOUACHE AND WATERCOLOUR MIXES COMPARED
A. Royal Talens permanent rose gouache mixed with approximately 40 per cent water (far left). The next swatch was mixed with less water and the one next with a little white to create a flat wash. The swatch on the far right is pigment with even more white and is overlaid with Winsor & Newton Antwerp blue
B. Royal Talens rose madder watercolour mixed with approximately 40 per cent water (far left). The next swatch was mixed with less water and the one next with a little white to create a flat wash. The swatch on the far right is pigment with even more white and is overlaid with Winsor & Newton Antwerp blue. Interestingly the watercolour wash lifted slightly and mixed with the blue, whereas the gouache in the swatch above did not
C. Royal Talens permanent rose gouache mixed with an equal amount of Winsor & Newton Antwerp blue watercolour. Notice how the wash is quite dense in colour
D. Royal Talens rose madder watercolour mixed with Winsor & Newton Antwerp blue watercolour. A little water was added when wet to show the separation and slight granualisation of the mix
Robert Dutton teaches mixed-media painting and drawing at a number of venues in the UK and abroad and demonstrates nationally for art societies. To find out more about Robert’s art holidays and workshops visit www.rdcreative.co.uk or telephone 0113 2252481.
This feature is taken from the May 2017 issue of The Artist
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