From Susan Tschantz
To paint a yellowish sky at the horizon with a bluer sky above without getting a green color from mixing the yellow and blue, I first underpaint the sky using yellow ocher, then I let this dry before adding any blue.
I start from the top, and using wide horizontal strokes the full width of the canvas, I pull the yellow ocher down to the horizon, so it fades out almost white. If I need to reload the brush, I start back into the darker color, again, pulling down until I get an even blend to the horizon. (I don’t want any edges where I stop and pick up or put down the brush.)
Then I let this dry, before I start working with my blue sky. I lay on the blue, with the darkest on the top and edges, pulling down to fade out, leaving some yellow ocher visible. By the time your brush gets to the horizon there is little blue paint on it, and what you do have will allow the yellow to show through. There might be a slight greenish tinge, but there often is in the sky. The darkest blue in a sky is always overhead, and it fades out towards the horizon.
I make sure after I apply the blue to use sweeping brush strokes with a wide brush to smooth out the brush strokes, but I don’t overblend. I want the variations! Only once this is finished do I start painting clouds.
Tip from: Susan Tschantz