Prismatic Pool, Yellowstone

Here is one more of the Yellowstone series - Prismatic Pool. You can't but love the colours of the Grand Prismatic Spring - turquoises, oranges, dark and vibrant, shimmering, pulsating. It took me a couple of attempts to achieve the effect I wanted. I used indigo, phthalo green and cobalt turquoise for the water, with cling film spread over to break the surface. The orange is made of a thick mix of vanadium yellow, ruby red and a touch of ultramarine blue. And sepia is the perfect dark dark brown. I dotted the surface with iridescent oil pastel (rich gold, golden pearl and red copper) before applying the watercolour.

I'm happy with the colours and textures, but the shapes and composition aren't quite right. It looks more like a scene from Star Trek, with solar flares hitting the earth and distorting its surface. The ultimate test is whether I'm prepared to pay €50 to have it framed. The jury's still out on that one.