Wall Preparation: Each Surface Is An Individual

by Nathan Zakheim

(Published originally in the MCLA Newsletter, v. 3, n. 2, 1991)

Why is wall preparation important? I use high quality art materials and follow the manufacturer's directions for use. Why isn't that enough to produce the best and longest lasting result?

Walls are as uniquely individual as people. If one could use a stop-action camera to record the activity of the type of outdoor walls typically used for mural painting, we would see an amazing variety of ways in which they breathe, peel, swell, sweat, shudder, and exfoliate particles. Since such dramatic activity is occurring to these walls day and night, rain and shine, we should not be surprised that the murals painted on them are inevitably affected. Historically, wall selection and preparation has played a major role in the creation of the greatest mural masterpieces. Frescoes call for several layers of "arriccio" plaster on the entire surface of the wall prior to the application of a final "intonacco" layer into which the fresco pigments are introduced. Mosaics require specific engineering calculation to interface successfully with most murals. Bas reliefs, glass and ceramic, as well as wood reliefs also require considerable forethought and preparation. Today, acrylic polymer murals on exterior masonry walls have arisen as a popular form of production, but little thought has been given until recently to preparatory work prior to painting or to preservability once completed. Unlike former times, when the architecture and mural decorations were conceived as an integrated parts of a single concept, murals are often added to existing walls without particular regard for existing architectural motifs (if any) and more importantly, without a sense that the building and its mural decorations will "grow old together," ripening into a fused aesthetic unit that is preserved and revered for extended periods of time.Taking wall preparation as seriously as it was in earlier periods will assure us of a legacy of finely wrought murals that can be preserved by their communties for multiple decades as cherished community property.

I am planning to paint a mural on a very porous and friable stucco wall. Is the preparation of this wall going to be more difficult due to the porosity?

Quite the contrary! The porosity makes the introduction of consolidating materials a great deal easier. The basic limitation is the relatively high viscosity found in most consolidants. If a wall can absorb water readily, then a consolidant with a viscosity close to that of water will be able to fill or at least coat voids that are periodically filled with water. Unfortunately, few consolidants have a low viscosity. For this reason, a porous wall will accept a higher viscosity than a solid masonry wall.Consider, also, whether the stucco is well attached to the supporting wall. If areas are loose, they need to be reattached with special adhesives, or possibly replaced altogether. Pressure epoxy injection, expanding plasticized grouts, bridging materials, as well as coatings that can solve a wide variety of preparation problems for the mural artist.

Ideally, in the future a muralist will be able to draw on technical services that will properly prepare walls for him or her prior to beginning artwork. Building owners may include wall preparation in anticipation of a mural project. At this point, however, if we want if done right, we had best do it ourselves!