'We are accustomed to seeing the landscape in colour, which makes us presuppose that we are aware of the tonal contrast,' says Paul Riley. 'Breaking down the tonal values into light, mid and dark doesn’t come naturally. This probably accounts for why so many watercolours can end up wishy-washy rather in the same way as the colour can get muddy'.

Understanding tonal values

Basically if the colour is light it will be light in tone; if the colour is dark, the tone will be dark. When it comes to primary colours, yellows are invariably light; red is darker and blue the darkest.

When evaluating the difference in hue, difficulties can occur with dark blues because of the depth of tone.

Try this

In order to see colours as simple tones, you can do this simple exercise using a smartphone, camera or tablet.

Take a shot in colour then convert it to greyscale black and white. Note how dark the red is.

Landscapes

Landscapes can consist of a lot of green, which may appear monotonous as a colour but when reduced to black and white many subtle varieties of tone make for an interesting image.

As an image, a purely tonal interpretation without the distraction of colour can be very satisfying.

Here a typical green landscape is reduced to greyscale.

The green trees and fields are pretty much monochromatic, which is reflected in the black-and-white image. Interestingly the black-and-white one has homogenised the view, making it a more interesting image.

Monochromatic colours

Choosing a specific colour for a monochromatic image can open up all kinds of possibilities for both the imagination and effects.

For instance, the predominance of greens in a landscape (see above) can appear rather dull unless relieved in specific ways.

However, if the same subject is treated monochromatically some interesting and illuminating effects can result.

Blues, pinks and greys, for example, can imbue the subject with different atmospheric effects.

When painting in watercolour I have specific mixes for the three different schemes.

Three groups of colours for painting monochromatic images

Top row: lamp black and Designers gouache for permanent white for highlights.

Second row is my pink/brown scheme consisting of raw sienna, burnt sienna and permanent rose. 

Third row is my blue scheme comprising phthalo blue (Cotman is intense), ultramarine and black. 

1. Pink/brown

For a pink/brown camaïeu I use a mixture of permanent rose, raw sienna and burnt sienna. The raw sienna gives the lightest tone, with the full intense burnt sienna the darkest.

The effect is one of rosiness, warmth and light. The feeling is sun-soaked and is very evocative for building-scapes. I first found myself using this scheme in Venice which, with the architectural details, created an otherworldliness. Seascapes can also benefit from this colour choice.

2. Blue/black

For blues it depends on which chromatic range best suits the subject.

By this I mean whether to use a red-biased blue as a base (ultramarine), or a yellow-biased blue (phthalo) plus black. The black knocks off some of the intensity of the basic blue, giving a little more range in the tones.

My choice for the basic mix depends on the subject matter: phthalo blue for pellucid atmospheres as it is a stain and therefore gives clean, clear transparent tones.

The more earthy appearance of ultramarine lends itself better to grittier subjects – landscapes with plenty of texture, leaves, bark and trees, rocks etc. There is nothing wrong with mixing these two blues but you will be playing with colour as well as tones, so the result will not be truly monochromatic (not that it matters!).

Some differences to note

It is interesting to note the difference between the pink scheme and the blue, in as much as the pink scheme is a smaller and therefore lighter tonal range, whereas the blue can go from very pale to the darkest possible, especially if using black as an additive.

Incidentally, you can substitute black with indigo, which is actually made from black and ultramarine, or Payne’s grey.

With the pink scheme it is well to choose a subject with a high luminance (light-coloured elements). The subtle close tones are easier to handle as a consequence.

The blue scheme can cope with low luminance, for example trees silhouetted against a night sky and night schemes in general.

3. Black and white

For a black and white monochromatic scheme I use lamp black plus Daler-Rowney white gouache. I know gouache is not pure watercolour but I use it only to add highlights and add texture.

The black/white or grisaille method cuts out all colour but gives a full tonal range to play with.

When considering the tonal range you have several options. For example you can choose a close, light range to depict a misty waterscape, or a dark close range to depict a nightscape. You could choose to paint solely in black and white, which is a brilliant way to depict reflected light.

This powerful contrast produces the greatest value of brightness and will seriously increase drama.

Dawn, Dittisham, watercolour on Saunders Waterford Not 300gsm, (50x70cm)

This blue/black image shows up well for a large tonal range. I used a damp sponge extensively to soften edges and create close tones.

Monochromatic painting techniques

When working in monochrome you don’t have to contend with the complex balancing job of mixing colour as well as tones, so you can enjoy experimenting with applying the watercolours in as many varied ways as possible.

The same rules apply – soft-edged close tones recede and appear furthest away and sharp-edged strong tonal contrasts appear nearest.

Wetting the paper first, either all over or locally, can give you those soft edges, then wait as the paper dries to add nearer and nearer objects.

I use all kinds of devices to add variety to the image, including masking techniques with masking tape and fluid.

I use a variety of brushes to apply the paint, even flicking and splattering to obtain textural variations.

A particularly useful way of introducing detail and texture is by use of a pen. I like to use a dip pen; I load the colour onto the pen with a filbert sable brush. I like to play with ways of obtaining tones using hatching, cross-hatching, both horizontal and vertical (for buildings), and diagonal for more organic subjects. Various concentrations of dots can also be used for tonal variety.

Wind over Water, watercolour on Saunders Waterford HP 300gsm, (57x76.5cm)

Although this abstract landscape is ostensibly a blue/black monochromatic image I have shown what happens when one other colour is added. This shows what can be done if the palette is limited, then enhanced.

Chiaroscuro

In any monochromatic painting exercise you need to manipulate light in order to reveal form and create depth. This is achieved through shading and tonal contrast. A form is invariably lit from one aspect, revealing a light and dark side.

When working in the landscape you are perhaps not aware of this, so in order to expose the form you may need to introduce a light source artificially and emphasise it. This is particularly useful when depicting buildings in the landscape.

To further the impact, strong contrasts of light against dark and vice versa can help considerably.

Frankly there is no end of fun to be had by limiting yourself to a monochromatic challenge. I recommend it.

Start by trying the two demos below.

Demonstration: Salute, Venice