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Creating a new mural

"A successful mural can be a source of renewal or inspiration for a community, and is great for the mural business in general. A poorly executed or disproportionate mural by any artist is not only disappointing but can discourage potential clients from commissioning murals of their own." Eric Grohe (artist) in Just Paint (Golden Artist Colors Newsletter), Issue No. 10, p. 6.

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Creating a new mural is an exciting process. However, to ensure the mural survives for as long as possible, it is important to carry out the process during favourable climatic conditions and to use materials and an installation method that are durable in the exterior/public environment. Knowledge of health and safety issues during fabrication of the work and documentation of the entire process are also important.

Note: References to commercial products are solely for the purpose of providing examples and information to readers in their search for appropriate and useful products for their projects. Mention of specific products does not imply endorsement by the Canadian Conservation Institute, nor does it preclude the usefulness of other products.

Timing

Climatic factors must be considered when scheduling a mural project. What is uncomfortable for the artist is also likely to be a poor situation for paint application, drying, and curing. Outdoor murals should never be painted in extreme weather conditions — too hot, too cold, too humid, or wet.

Safety issues

Check into the health and safety issues and regulations relating to the materials and procedures that will be used for the mural. Some industrial paints and coatings emit toxic vapours and require precautions such as the use of personal protective equipment, e.g. organic vapour masks.

Be sure you understand the employer and employee responsibilities outlined in your provincial occupational health and safety regulations. These regulations govern the use of specialized safety equipment (e.g. ladders, lifts, scaffolding, and safety harnesses) by staff or contractors. For example, contractors and supervisory staff often require specialized training on safety and fall protection equipment. Some information is available on the website of your provincial Ministry of Labour. You can also view the standards referenced in the regulations of each province and link to each jurisdiction through the Canadian Standards Association (CSA).

Documentation

Keep records of all the materials used, including the surface preparation and any coatings applied, as well as the installation methods.

Photographs are ideal for documenting materials and procedures and can also be used for promotion and publicity. Close-up photographs of all parts of the mural will be useful for future restoration procedures. They may also be beneficial for those undertaking research and are an effective way to share information with other mural communities. Detailed photographs of sections of the mural will be helpful if treatment is required in the future.

Paint colour chips, paint samples, paint type, and pigment codes will be useful in the future to identify colour fading. They can also assist with maintenance and treatment.

Materials and methods of construction

Investigate the permanence and longevity of the proposed materials and methods of construction with other mural communities, product manufacturers, and conservators. Their experience can be invaluable to you, especially if you are considering new products or procedures. Information on the materials and methods of mural production is also available from Golden Artist Colours, Mural Routes Inc., the Chicago Public Art Group, and Rescue Public Murals. However, keep in mind that the recommendations of others must always be assessed in the context of your climate and environment.

The primary support

Murals can be created directly on a wall or on a separate support attached to a wall.

Mural of wagons and horses.
Image 1: Busy Wagons, by John Hood, , Town of Collingwood mural, Collingwood, Ontario; (artists' acrylic paint on brick wall).

Walls

If a mural is undertaken directly on the wall of a building, the wall is the predominant factor in the longevity of the mural. The wall must be in good condition and any loose material (such as dirt or flaking coatings) or repellent surfaces (such as release agents) must be removed. The primary enemy is moisture. Moisture in the wall, combined with the freeze/thaw cycles occurring in northern winters, can cause flaking of paint layers and sometimes spalling of the wall surface. Murals that are painted on old (red clay) brick walls are particularly prone to this kind of damage.

Moisture can originate from many sources:

  • the ground (rising damp);
  • within the building if the wall structure or insulation is inadequate;
  • openings such as cracks or joints that do not have adequate flashings or caulking;
  • deteriorated mortar;
  • water run-off from the roof, etc.

Before painting a mural on a wall, inspect the wall carefully to ensure it does not have a moisture problem:

  • Is there salt efflorescence or other signs of moisture damage?
  • How does water move over the wall during rainfall — does it flow over the surface or is it directed away?
  • Is a "wetting" pattern or area visible?
  • Are improvements necessary to divert water flow and drainage?
  • Do the caulking or flashing need improvements?
  • Have modifications to the wall resulted in areas of local instability?
  • Is there staining from metal attachments?
  • Are bathroom, laundry, or kitchen vents present?

Many different types of walls are suitable for murals:

  • Concrete block walls provide a good, stable support. Their smooth surface is convenient to paint on and can be economical in terms of paint and brushes. As long as the surface is well-prepared, the mural should remain in good condition.
  • Plaster or brick walls may or may not be suitable. Cracks, poor construction, poor insulation, or certain architectural features can allow moisture into the wall. On good brick walls, the odds of success can be increased by leaving the bottom few rows of bricks unpainted, or leaving an unpainted border around the mural. This provides an area for the wall to "breathe". However, such precautions will not prevent flaking paint and spalling of the brick surface if there is a moisture problem in the wall, or if the construction of the building allows interior humidity to move through the "porous" brick. Though some brick walls can be successful, older brick walls or red-clay brick walls are not considered a good choice.
  • Metal siding appears to be suitable, with many murals surviving well.

Separate supports

Many murals are painted on separate supports, which offer the following advantages:

  • the artist(s) can paint the mural within a studio and apply a protective coating in controlled conditions; and
  • the murals can be relocated if necessary.

Murals on separate supports require an armature or mounting system to attach them to a wall. Non-rusting metal fasteners or supporting armature are recommended. To ensure the mural is mounted effectively, seek the expertise of a qualified installer.

Many different materials can be used as the support for a mural:

  • Wood products that are designed for exterior use can be suitable for murals provided they are high-quality products with the following characteristics:
    • they are designed for long-term use;
    • they have excellent durability outdoors;
    • the surface is compatible with the painting medium;
    • they can be mounted easily to a wall;
    • they can be sealed to prevent the ingress of moisture; and
    • they are non-compressible and rigid so that permanent dents and other deformations cannot be made in the surface.

Marine plywood or sign painters' boards such as Crezon board are good choices. (Some artists have suggested that properly prepared and installed Crezon board lasts better than marine plywood.) Sign painters' boards are industrial plywood panels, made for exterior use, with a medium-density overlay that provides a nice painting surface. Be sure to choose a board with all-fir plys and no interior voids, and inspect it carefully prior to purchase to ensure there are no surface faults.

Laminated boards such as marine plywood and sign painters' boards require special precautions to prevent the ingress of moisture and the associated distortion and delamination of plys. The boards must be well primed; the edges and joints must be sealed; and flashing is required around the edges to prevent water seepage and direct water away.

  • Metals, whether a honeycomb panel with aluminum skins or a Dibond panel (aluminum skin over a polyethylene core), can also be a suitable support for murals. Such murals appear to be quite durable as long as the surface is properly prepared.
  • Alternative supports manufactured for the exterior environment have also been used, with varied success. However, before using a new industrial product as a support, try to see the product in use and answer the following questions:
    • Does the material flex?
    • Is it compressible or does it have a compressible core that can be dented?
    • Are repairs possible?
    • How must it be prepared and what paints are compatible with it?
    • Are priming materials and paints safe and convenient to work with?
    • What are the long-term properties?
    • Is a special installation system required?
    • Are all edges and points of attachment sealed against moisture and physically protected?

It is also a good idea to seek the opinions and references of others who have used the product.

Surface preparation

A mural cannot survive for long if the paint does not adhere well to the primary support. To ensure good adhesion, the surface must be clean, coherent, and properly primed. Some surfaces may need some additional preparation to ensure they have an adequate "tooth" for the primer.

Clean the primary support

  • wash the wall (if using a power washer, make sure not to damage the wall surface);
  • remove any loose material;
  • remove form release agents from concrete walls;
  • if there are any surface agents that could interfere with adhesion, remove them with solvents or household cleaners;
  • be wary of an existing coating on the surface, particularly if its composition is not known. It may not be compatible with the paint to be used; and
  • allow adequate time for the wall to dry.

Ensure the surface is coherent

  • inspect the wall carefully and note any surface damage;
  • fill in any cracks;
  • seek professional expertise and service if the wall requires extensive repair or if an additional surfacing is required;
  • if the wall needs extensive repair, it may not be a good choice for the mural; and
  • never paint over an existing architectural paint that is flaking or discontinuous.

Obtain an adequate "tooth"

  • for metals or laminated wood board with smooth, finished surfaces, lightly abrade the surfaces to provide a "tooth" for the primer;
  • "degrease" metal surfaces (e.g. with acetone, preferably outdoors) before sanding their slick surfaces; and
  • remove residual powder from sanding with a damp cloth.

Apply a high-quality primer

  • choose a primer that is compatible with the primary support and the paint to be used for the mural [technical representatives from architectural paint companies can provide advice on the best primer to use for a particular wall. Other mural programs/artists can offer insight into the success of specific primer/paint combinations];
  • do not dilute the primer; and
  • test and assess the adhesion of the primer to the primary support. [Apply the product to a small area on the surface and, when it dries, scratch the layer to test adhesion. Areas that appear to "resist" an even application or allow easy removal may require further cleaning and/or sanding.]

Additional instructions

For laminated wood supports, lightly sand the smooth surfaces to ensure good adhesion of the primer. Apply at least two or three layers of a water-resistant primer along all the edges of the board to prevent the ingress of moisture. Two layers of good-quality primer should also be applied to the front and back of the board.

For aluminum composite panels, lightly sand the surface and remove the dust, and then apply a primer that is compatible with the metal support and the painting medium. For more information, see Mayne, D. Working with Aluminum Composite Panels. City of Windsor Art Studio, .

For metal-clad surfaces, contact those familiar with the cladding product and its present coating (e.g. architects, cladding and paint manufacturers, or other artists/mural communities) for advice on degreasing the surface as well as suggestions for compatible primers and paints.

Paint

Above all, artists should know their materials. They should consult the product manufacturer, as well as other mural communities and mural artists who have used the product, to obtain technical information and advice. They should also monitor their murals over time to detect fading or deterioration of specific colours or products.

Many paints are suitable for murals, e.g. acrylic paints, silicate paints, and other industrial paints. Regardless of the paint chosen, it is essential that the pigments have high light stability. Some manufacturers conform to voluntary labelling standards, so look for rating scales and select only from the lightfast pigments. If a manufacturer has ratings on some products and not on others, the unlabelled pigments are likely of questionable lightfastness — and should be avoided.

When selecting paint, consult the manufacturer for answers to important questions such as:

  • Is the paint suitable for use in the outdoor environment?
  • Is it compatible with the support you are using?
  • Does it require any special preparation of the support?
  • Are there any other peculiarities of use?

Some paint manufacturers (e.g. Golden Artist Colors and Nova Color) work with artists on specific mural projects, and monitor the ongoing condition of the murals. They will be able to guide you toward the pigments and products that work best for outdoor murals. Other artists and mural communities are also a good source of information. Through experience, they are likely to be aware of which colours remain vibrant and which fade. Even when using the most stable pigments, always retain paint chips and paint samples as a reference for colour change and future restoration.

As outdoor mural programs have increased in recent years, so too have investigations into suitable mural materials. One common investigative procedure is accelerated ageing, which provides fast results but may not predict exactly how the paint will behave in the natural and harsh outdoor environment. Consultations with artists who have used the materials and/or monitoring outdoor murals produced with known materials can provide more accurate information. As more investigations into mural materials are carried out, more materials that are known to be stable should become available.

Most mural artists have preferred materials and methods. However, planning committees should verify the appropriateness of the approach by seeking references from other cities with murals by the same artist.

Acrylic paints

The most common paint for murals is acrylic.

  • High-quality acrylic latex house paints are a popular choice, but they don't provide a large selection or vibrancy of colour. Although they can be mixed in a "palette" technique to modify the colours, the shades produced are often dull. For more information on specific paints being used, look for descriptions of major murals on artists' websites.
  • Artist-quality acrylic paints such as Golden Artist Colours, Stevenson Acrylic Paint, or Nova Color Artists' Acrylic Paint are also widely used.

Provided the paint is of high quality and the surface is well prepared, the main problem with acrylic paints is fading of certain pigments and dulling of the surface due to deterioration of the medium. Even with lightfast pigments, some colours may fade prematurely. Footnote 1

Two other problems have also been noted:

  • the acrylic medium can deteriorate when exposed to intense ultraviolet radiation, which can make the surface appear faded; and
  • the surface of dried artists' acrylic films remains soft and tacky at relatively low temperatures, which allows dirt and dust to become embedded in the paint surface.

To address these issues, Golden Artist Colours recommends adding a harder medium (GAC-200) to the acrylic paint to increase its durability, as well as using a two-part coating system on top of the paint. They are also seeing promising results with their solvent-based acrylics, the MSA colours (Mineral Spirit-based Acrylic resin colours).

Silicate paints

Silicate paints such as Keim Mineral Paints can also be used for outdoor murals. These paints combine a potassium silicate binder with inorganic fillers and natural earth oxide pigments. The paint penetrates into mineral (masonry) substrates (i.e. brick, concrete, stucco), forming a permanent bond that is integral with the surface. The palette of silicate paints is not as extensive as the palette of acrylic paints, but the inorganic pigments are durable and resistant to fading. Successful use of silicate paints also requires proper surface preparation and some working experience with the product. To view some examples of murals produced with Keim paints, see Eric Grohe Murals & Design and AlbanyMural.

Other industrial paints

Other industrial paint systems have been used with varying degrees of success. Before deciding on an industrial paint, assess it for:

  • permanence and longevity within the specific environmental context;
  • compatibility with the support material;
  • ease of use; and
  • toxicity.

Alternative media

As an alternative to paint, durable media such as coloured bricks, mosaic or sculptural metallic or ceramic pieces can be used to create a design (mural) on a wall.

Mural of people singing and dancing.
Image 2: Mosaic Mural Almonds and Wine by Cristina Delago, ; City of Toronto, Ontario; (frost resistant porcelain tiles, glass tiles and handcrafted porcelain tiles, exterior grade adhesives and grouts on cement board attached to the wall with Tapcon® screws and commercial grade caulking; grout sealer applied once a year.)
Photograph by Tomasz Majcherczyk,

Surface coatings

The application of a surface coating may increase the longevity of a mural by:

  • helping to prevent the photochemical breakdown of the paint medium;
  • providing some physical protection against atmospheric abrasives or minor damage; and
  • providing a surface against which some cleaning can take place.

However, surface coatings have been used with varying success. Some coatings have discoloured, peeled unevenly from the surface, developed a white haze (blanching or bloom), and been impossible to remove without damage to the paint. Given such unsightly problems, it is important to investigate a coating thoroughly before applying it to a mural. Contact the manufacturer to obtain information on the coating's properties and recommended use, and communicate with other communities or artists who have had experience with the product over a number of years. It is better not to apply a coating than to apply one that could have poor ageing properties.

To be a suitable surface coating for outdoor murals, the product should be stable (remain clear and coherent) and compatible with the paint and the primary support. For example, it must not dissolve the paint, and it must not make a brick wall completely impermeable to moisture. In addition, some coatings that are suitable for solid supports are not recommended for flexible supports such as banners. Although it is preferable that the coating be reversible (easily removable), finding a product that can be removed from an acrylic paint surface is likely impossible.

Information on the behaviour of surface coatings on outdoor murals is generally lacking, although research has begun. For example, Mark Gottsegen, Administrator of the Art Material Information and Education Network (AMIEN), is developing a testing program to monitor how well coatings withstand the environment to which they are exposed (Mural Painting. Conjecture to Knowing a Manufacturer's Point of View). However, existing anecdotal evidence and the results to date do not allow for specific product recommendations.

Nevertheless, some artists and communities are having success with specific coatings. Automotive clear coats that contain ultraviolet filters and can be easily washed have been used successfully on murals executed on aluminum composite panels (Mayne, D. Working with Aluminum Composite Panels. City of Windsor Art Studio, ). Los Angeles mural groups have been recommending coating products such as Soluvar. Golden Artist Colours has specific recommendations regarding their own products Footnote 2 and artists appear to be following the recommendations with success. Footnote 3 Various other commercial products have also been used with apparent success. Many mural artists have become confident in the products they use — the coatings have become part of their technique and are routinely applied upon completion of their work.

The effectiveness of a surface coating will also depend on how and when it is applied. The application may not be successful if:

  • the surface is not clean and dry;
  • the application method is faulty;
  • the surface texture of the wall is not conducive to a clear, even layer; and
  • the environmental conditions are unsuitable for application and drying.

To ensure the application of a coating is successful:

  • know the product;
  • contact the manufacturer to inquire about its properties;
  • obtain advice on its behaviour from those who have used it;
  • test it to make sure it works on your support and paint surface; and
  • ensure it is applied properly (have a knowledgeable person supervise contractors).

For murals on a separate support, ensure that the paint and/or surface coating are applied over any fasteners/holes that are used to attach the support to a wall. This will help prevent the ingress of moisture at the points of attachment.

Anti-graffiti coatings

The first line of defence against graffiti should be proper site selection, lighting, maintenance, signage, and community buy-in. However, if a graffiti problem develops, or if locating the mural in a high-traffic or graffiti-prone area is unavoidable, an anti-graffiti coating may be appropriate.

Before applying an anti-graffiti coating, make sure it is appropriate for the wall surface and the climatic conditions in the area. Contact the manufacturer for information on its properties, recommended use, and removability (some products can only be applied and removed by a licensed firm, whose methods may not be appropriate for a mural). Information on the performance of a coating can also be obtained from municipalities who have used it.

Some anti-graffiti coatings are sacrificial, i.e. they are meant to be removed along with the graffiti. The recommended removal method for these coatings is often water under high pressure. Because this procedure is not appropriate for many wall surfaces or murals, a less aggressive removal method should be developed (in collaboration with the technical reps) and tested prior to using the product.

Some studies on anti-graffiti products and other protective surface coatings have been initiated in the last few years. For example, Tarnowski et al. have been studying anti-graffiti coatings on sandstone and marble (Tarnowski, A., X. Zhang, C. McNamara, et al. "Biodeterioration and Performance of Anti-graffiti Coatings on Sandstone and Marble." Journal of the Canadian Association for Conservation 32 (), pp. 3–16). In addition, artists in the Philadelphia Mural Art Program and students and faculty from the Winterthur/University of Delaware Art Conservation Program are collaborating on a project to explore new products (Kerr-Allison, A. Outdoor Public Murals: Materials, Advocacy and Conservation. Winterthur/University of Delaware Program in Art Conservation, ). They have begun testing a water-based ultraviolet-absorbing coating to determine if it:

  • protects the mural from exposure to ultraviolet radiation and weathering;
  • remains clear;
  • provides a barrier against dirt and graffiti; and
  • is safe to apply and remove.

After 3 years, the product appears promising in its performance on test surfaces. However, it has not yet been tested for removability or as a protective layer against graffiti.

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