I recently made myself a tiny watercolour paintbox, using an old tin that originally had a dried up stamping ink pad in it. I filled one side with DAS airdry clay and pushed 6 semi-circular depressions into it with the round end of a menthol inhaler. And let it dry – it took about a week. Then I gave it a couple of coats of white acrylic paint to seal it. Once it was dry, I squirted a blob of good quality liquid watercolour from tubes into the little holes – Lemon Yellow, Vermilion, Crimson, Pthalo Blue, Purple and Green. Then I let them dry out before taking it out into the field.
It works pretty well. The paints get wet, dry out, get wet again with no impact upon their quality. Here’s one I did earlier in the summer using ballpoint pen with the watercolours.
Waiting for shearing (Ewes, not the lambs) 
