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by Jay Beswick
(Published originally in the MCLA Newsletter, v. 1, ns. 2,3, 1988)
To insure the legacy of street art murals, those of us who plan them should consider the permanence of the sites we choose. Upon inspection, murals in our area were found to be suffering from defacement, color fade, atmospheric weathering and poor adhesion. Restoration can be difficult, though possible with most problems, except adhesion. Most artists plan their work according to esthetic vision, not always taking into consideration material problems; and certain weathering characteristics exist on walls and bridge abutments on sites chosen to date that didn't receive prior consideration. With current available technology, such as peel coatings, we need advance planning that includes consideration of compatible substrates with a careful evaluation of site location.
The following explains product failures we've experienced when reviewing existing murals. To protect an investment of time and energy I am recommending a series of steps that will preserve and extend the artist's vision. With many art treasurers in need of stabilization at a time the original artist is unavailable, we must look back and learn from our past experiences.
With a natural concrete substrate on a bridge abutment or wall, when that wall is a retaining barrier for soil and vegetation opposite the mural, the muralist must consider the problem of moisture intrusion. In those cases where soil and shrubs are retained directly adjacent to and above the level of the mural, the concrete or block substrate may develop problems with moisture retention when rain and the water from sprinklers and water drainage saturates the concrete, remaining in the soil until the water exits by evaporation or by channeling around or through its painted barrier. The effect to the artwork is: blisters, popping, and partial delamination of the mural.
The second effect is the deposit of efflorescence, or simplified water soluble salts and minerals, beneath the mural. Here what takes place is called a capillary action when, much like a sponge touching a water source, water and salts from the soil are drawn through a wall or concrete material. The efflorescence shows up as a white powdery substance, which remains on the wall when the water evaporates or recedes. The salts become corrosive and the powder composition acts to break the intercoat adhesion between the mural and the substrate the mural is painted on.
To prepare a surface in advance to insure the greatest longevity and future preservation of the artwork, a suitable priming system should be selected that promotes the maximum moisture resistance and intercoat adhesion between the mural and selected primer.
The expanding paint technology in the field of Industrial Chemical Coatings provides several suitable priming options. Leading the market are two-component epoxy systems known for their durability, but weak as an exterior finish, with limited resistance to ultra-violet exposure. The epoxy system is best, with superior adhesion properties; but a second application of a simplified primer or the use of a background paint by the muralist within four (4) to 24 hours is recommended, after the epoxy is applied. Once primed, the muralist has only to complete the painting before proceeding with the last steps to promoting the art's longevity.
The final step for long-lasting protection is the application of a 2-component clear polyurethane coating. This final protection should provide a cleanable surface that is graffiti-resistant, chemically resistant to various cleaners, and corrosive-resistant to atmospheric and environmental factors, including the effects of exhaust residue. In addition, the product should be light or U.V. stabilized. For this final stage there are dozens of manufacturers who claim they have what the muralist needs. At this point, the artist is either extending or decreasing the life of the mural, as all such products are not the same.
To protect his work effectively, the muralist should test the selected system against a small area of his mural to check the product's compatibility with the mural paints already in place. Many 2-component paints contain reactive solvents that cause other paints to craze, bleed or dissolve. Some coating manufacturers have researched this possibility and provide primer options, including waterbase priming systems that dry clear and provide a protection or barrier coat between the mural and the final protection coating.
Other options available are peel-paints which, when applied under the mural, allow future relocation by peeling and removing the work to another site.
Though the application process sounds cumbersome, with two primers prior to the mural application and two protection coatings after the art work is complete, these extra steps will prevent costly future maintenance and insure the legacy of the artist's efforts.