All watercolour paintings are a combination of two basic watercolour techniques – Working Wet-on-Wet and working Wet-on-Dry.
Wet-on-wet simply refers to the process of wetting part or the entire surface of the paper and laying a wash down or dropping in colour off the point of the brush usually before the shine has dried off the paper.
Wet-on-dry is simply painting directly onto a dry surface, whether or not there is already an existing layer of wash on the paper.
How do you choose what is the most appropriate approach for your subject?
The simplest rule is: the larger the area, and the lighter the tone, the softer the blend or ‘edge’ -– wet the paper first.
The smaller or more distinct the area, the more precise the ‘edge’ needed – work onto the dry paper.
If you want to paint a simple sky with a soft gradation of colour from deep blue to pale blue to almost white – wetting the paper first slows down the drying process so you have time to load up your brush and fill the area.
But if that sky has those colours and some dramatic clouds in the whiter area – then you have to wait until the first wash is totally dry and paint the clouds in after.
Use the back of your hand to check whether a sheet of paper is really ‘dry’; if it feels like damp washing, it is not properly dry. You can bend this rule to produce soft, fuzzy backgrounds by applying details, for instance, distant leaves or twigs, when the wash has dried to the point where there is no shine on the paper. It should be just damp enough to soften and blur the outlines.
Waiting for paper to be dry before adding a second wash is one of the most important rules towards successful watercolours – if after laying in the first wash you decide to add more colour over a wash which has only partially dried - the second wash begins to disturb the first and you get a muddy mess. To understand why, it is interesting to look at Watercolour paper is constructed.( see 'Paper')
A Lighter Shade of Pale
In watercolour it is the rule not to use white paint – lights are achieved by leaving the white of the paper (or ‘ground’) to show through. To do this you have several options – you can indicate in your underdrawing the areas which are white and make sure you don’t paint over these, or you can prevent the paint from reaching these areas by with either a physical block – Masking Fluid , or by quickly lifting out with a tissue the areas you want to remain light. The rule against white is simply that any white paint will have a ‘gouache’ or opaque appearance in the work and look clumsy in comparison to the transparency of the rest of the painting. Fine,light details in the middle of broad wash areas can only be achieved through the use of Masking fluid – a good tip is to use toothpicks for delicate tree branches , as once the fluid gets into the base of a brush it’s very hard, if not impossible to remove it. If you missed an area in your planning you still have a few more chances – you can lift out a small areas using the tip of a brush (old, worn brushes work best for this so don’t throw away a brush simply because it has lost its fine tip); you can sponge large areas out using a soft sea sponge; (good for ‘misty’ effects) or you can scrape tiny slivers of light along fence posts etc by using the flat of your craft knife. Just make sure the paper is absolutely dry before attempting this technique. And at a pinch you can use tiny amounts of white gouache or watercolour in small areas where they will add a bit of light but not look too obviously opaque. Once you have added an opaque paint into a painting you cannot rewet the wash – watercolour will remain stable when lightly rewet but white paint will float off! Watch out for this if you have used watercolour pencils to augment details in your painting – they are not waterproof like dried watercolour.
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