I painted the background on these tall paintings in a similar manner to the previous pair. First I put the canvas on the easel sideways and drew lines in white, black, yellow and blue. While the lines were still wet, I brushed over them with water, blending the colors but still leaving the lines showing.
When that background was dry, I turned the canvases to vertical and executed the same process, this time leaving out the black and adding alizarin crimson. I found that sometimes when I use black in the final stage, it can make the background too dark.
Now I have two canvases with backgrounds, ready to go.