Transparency
This is a commissioned painting I finished last week of Loyalsock Creek in Pennsylvania. This was a very difficult painting and I've posted it because I learned some useful layering tricks.
To faintly show the bottom of the creek, I applied an underpainting wash of yellow ochre in the water area, let it dry, and then built up the water with thin layers of oranges, browns and greens. At first, my water came out with a very dull, matte look and I couldn't figure out why. I was diluting the paint well with gloss medium and water, but it came out looking flat. After a lot of experimentation, I realized that the oranges, browns and greens I was choosing were too opaque. I knew that paints came in different transparencies, but I hadn't paid much attention before.
I ended up repainting over the water area with yellow ochre again, and starting over. I hunted through my paint box for the most transparent colors. Most professional quality paints show the transparency of each color by a hand-painted swatch on the tube:
You can see that the Quinacridone Burnt Orange on the left is much more transparent, because you can see the black crosshatches better than you can on the Raw Sienna. I remixed the layering colors of the creek using the transparent colors that I had, and when I painted the layers in again, the water looked much better.
I finished the painting off by painting in the white highlights, using the transparent Zinc White, and added more texture to the water with some washes of iridescent interference colors. Next time I'm shopping for paints I'm going to pay more attention to the transparency.