Substrates

Substrate selection is often defined by a mural's location. When working on the exterior of a building, (whether it be made of wood, cement, masonry metal etc.), and on interior surfaces as well, it is important to know how to prepare the substrate before beginning to apply paint. Different substrates may require specific techniques and materials. If not done correctly, the life span of the mural may be cut short.

Generally, it is always a good idea to take a substrate down to its original surface. Trusting the Integrity of previous coatings can put mural work in jeopardy. It is also difficult to determine if these coatings will be compatible with other products that are being used.

If an artist chooses to overpaint a surface that is already painted, he or she should consider the type of the existing paint and its physical condition. If the paint is a waterbased polymer (commonly referred to as latex), chances are good that the acrylic paints will adhere sufficiently. If it is a high gloss oil paint (or of unknown materials), then it must be abraded (or removed) for good adhesion. If the existing paint film is deteriorating, then it is best to have it removed (sand-blasted, power-washed, scraped, etc.). It is critical to wash any painted surface, even a newly painted surface, with soap and water to remove dirt and grime prior to application of acrylic products.

Previously painted high gloss surfaces can be cleaned and dulled in one step by using a household abrasive cleaner. Cleaner must be washed off completely with clean water. Mold and mildew must be removed by hand-scrubbing with a mixture of 1 part household bleach to 3 parts water.

CAUTION: Never add ammonia or ammonia-based cleaners to bleach! Wear goggles and protective equipment while cleaning. After scrubbing with a brush, allow the solution to sit on the surface for 10 minutes before thoroughly rinsing off with clean water.

If there are cracks and grooves in the substrate, the method for filling and smoothing these gaps will depend on the nature of the substrate itself. Artists should consult an area architectural coatings store for recommendations on the best product available.

Once the surface has been cleaned, a primer coat will give better adhesion for the paint. One key feature to look for in a primer is whether or not it can be painted over by latex paints. This should ensure that the primer will he a compatible surface for the adhesion of waterborne acrylics.

To determine the best primer for a specific surface, we suggest artists contact their local supplier of architectural coatings. Such companies have extensive experience with priming the broad spectrum of building supplies, and typically have specific primers for the surface the mural is to he painted on. Their recommendations will also take the environmental concerns of the area into account. Architectural and maintenance paints are competitively priced, meaning that a product that costs more than a similar product will typically perform better as well.

When painting on brick, concrete, or other masonry surfaces, we recommend use of a masonry conditioner that can be purchased from a commercial coatings supplier. In some cases, muralists will want to consider painting on panels (wood, aluminum, fiberglass, etc.) rather than directly onto a wall. There are various reasons an artist may choose to work on panels. Sometimes the existing substrate is too difficult to work on. It could also be a matter of convenience since painting on panels will usually allow an artist to work in his or her studio.

Painting on panels is a good alternative for someone who doesn't have access to scaffolding or other equipment. It can be much easier than painting off a ladder all day. Panels can also be a safer, cleaner way to work with groups of children or other large groups of people. If artists choose to work on panels, they will want to make sure they choose the right kind of panel for the right situation. Preparation of panel substrates will also depend upon the chosen material.

(See Mural Quick Reference Guide)