I have an affinity for painting flowers and related scenery, so getting commissioned for a backyard mural with flowers and plants was a breath of fresh air. The challenge started when I visited the client's home and he showed me the wall to be painted.
Now, I don't know if you're familiar with the word efflorescence, but that is what I found on that backyard wall. Efflorescence (which means "to flower out" in French), in chemistry, is the migration of a salt to the surface of a porous material, where it forms a coating. It can look very much like mold, and its unattractive appearance raises concerns. While the salts brought to the surface are rarely harmful, the condition of efflorescence indicates that water is moving through the masonry in ways that are not intended.
When it comes to painting on a concrete wall with efflorescence, it isn't an easy task. It requires thorough preparation that starts with chemical power washing, then applying coats of water sealer and base coating. Wall preparation alone can take several days (to allow proper drying time between the steps of the process), and the procedure is not cheap.
One way to skip the prep process - and its cost - is not to paint directly on the wall. Rather, install a mural that is painted on polyester weave material, also known as solar screen fabric. A mural painted on screen is not only better-looking than artwork painted on concrete, but happens to be chemically more durable as well. It is water- and weatherproof as well as easy and quick to install.
At the end, the client and I were very happy with the installed mural. Come to think of it, the palm tree and the plants in front of the mural were probably happy too that they didn't have to suffer through a chemical power wash.