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
(See Mural Quick Reference Guide)