Catherine uses two palettes, for warm vs cool colours and mixes the colour on the rough-surfaced watercolour paper itself. In the early stages she let's the water do much of the work of blending the colours. She uses a 1" Pro Arte one-stroke flat brush which can hold and release a lot of colour, a smaller [2/5"] flat for taking off excess liquid from the paper [preferable to kitchen roll], and a rigger. 

The rigger, with it's 'flicky' extended hairs, is good for making slightly random marks.  Catherine observes that we are not naturals at recording randomness. Our marks are too regular in size and spacing if we're not careful. Techniques that introduce realistic randomness and bypass our need to control too much are all to the good. For instance, she used scrunched clingfilm on the 'moonglow' rocks, which draws the colour into some areas and away from others. She also used salt for a related effect.

The rigger was also used later on, of course, for precision marks such as 'filigreeing' the spray and edges of the wave where skilful use of the corner of the flat brush was perhaps not quite enough.

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