For the background of the female Lazuli Bunting painting, I decided to see what would happen if I first painted the ground with white gesso, let it dry, then paint a medium blue gray in acrylics over it and let it dry, then paint a layer of mixed gesso with a gouache light blue paint. However, the gouache in the bottle had separated over time into a separate pigment section and medium section. The medium still had some pigment in it, but it was very liquidy. So I mixed the colored medium with the gesso and found that they were repelling each other, but I managed to cover the entire background with a light blue color. Almost immediately, the background began to crackle with big cracks that reminded me of tree limbs, a definite benefit to the painting I was planning. After the crackling completed, I sprayed the entire background with a fixative spray so that I could paint freely with acrylic over the crackle background.
Prior to this happy discovery, I had only known one way to form crackles, other than the two-part bottled crackle solutions available in artist supply stores. That way was putting a layer of glue between two layers of acrylic paint. I’d like to hear about other ways to use paints and mediums to make creative backgrounds. I recently read about dripping alcohol onto layers of acrylic paint, but that article indicated that the 70% isopropyl alcohol did not work well, while the 91% solution did work well.