Mural Painting Tips and Techniques

A summary of the Artists’ Round-table held at the 5th National Mural Symposium, November 2001 prepared by John Hood

The intention of this session was to share ideas concerning media, methods and technical processes related to mural painting, and identify and speak to areas of delegates’ concern. Often a discussion of this nature raises as many questions as it answers, due to differing approaches and methods that artists employ; however this seems to be part of the process, and invites continued discussion and debate. Questions were posed and answers were supplied by the group at large.

What type of materials are used in the creation of “3D murals”?
The concern was with methods to erect supports or surfaces that are raised from the building surface. Among the solutions discussed was crezone, a plywood laminate bonded with adhesives that make it very stable in exterior applications. Traditionally used by sign painters for outdoor signage, it is available in different thicknesses and can be cut with a circular saw. It has smooth heavy paper external skin which gives a good ground for oil based and acrylic media. There are different types of laminated wood based products available from the building industry, some with resin or synthetic surface treatment that are designed for exterior cladding use and could be used for mural panels.

There are a number of considerations in the use of such products, however; firstly laminated products are by definition composed of a number of layers that have a “sponge-like” effect at the edges of the panels. Therefore it is of extreme importance to ensure that the edges of such panels have been carefully and thoroughly sealed with at least one and preferably two or more coats of a top grade water resistant primer that is known to be compatible with the panel system. Sealing the back of the panels with primer would be a good method as well. This procedure will help to prevent the separation of laminations at the edges of panels, an occurrence that renders a very undesirable appearance to a mural panel. Caulking the join lines between sheets is another important precaution against this type of damage.

Secondly, it is important to establish the chemical nature of the outer coating on products that are sold as “pre-primed” or “finished”. Some coatings are not designed to accept paint coatings. Check with the distributor or manufacturer. Obtain a spec sheet on the product and be sure to explain the intended use of the product. Some suppliers are not above selling you a product that is unsuited for the intended purpose, so use extra consideration when obtaining surface building materials. Conduct a test of the intended paint media on a small section of the intended surface material, prior to installation. Make a thinned solution of the paint media and apply it to the panel. It should flow smoothly, coat evenly and appear to sink into the surface a little. In the event that the media pools or beads, or takes on the appearance of water brushed over a waxy surface (the “wax resist” effect ) then the adhesion of the media is not acceptable. In this event, check the spec. sheet for an appropriate solvent. Break down the surface sheen with a light sanding and wipe with an appropriate solvent such as Varsol, Methyl Hydrate or a well diluted solution of Trisodium Phosphate (TSP). You want to obtain a matte surface which will allow thinned coats of paint to bond. Once you have achieved this effect you may install panels with confidence, but apply the same treatment to the entire surface. If you cannot achieve good adhesion with the test sample, look for a different sheeting material.

Another material that was discussed was Dibond. This is a rubber core sandwiched by aluminum sheets. It is available in standard sized panels and must be primed prior to painting. Similar products may be marketed under different trade names. It has the advantage of being impervious to cracking and puncturing, but care would have to be taken to use a primer that would adhere sufficiently well to the aluminum as well as providing an acceptable ground for your top coat media, whether oil or water based. As with all products, be aware of manufacturers specs and recommendations for use and follow them closely.

A further product available in Canada under the trade name Hardipanel may be worthy of consideration. This is a fibre cement panel composed of Portland cement, sand, cellulose fibres and glue additives. It is available in 4 foot widths and lengths of 8, 9 and 10 feet. A 4 x 8 sheet weighs 75lbs. This product comes pre primed and is designed to accept paint finishes on either a smooth or stucco finish. It is recommended for 100% acrylic top coats. It is designed to be installed with corrosion resistant nails, for vertical installation. It can be used like siding in building construction or can be set into frames for free-standing walls. Contact James Hardie Building Products Inc. 1-888-JHARDIE (542-7343) for further information of this product.

Most of the above products would be applied to a metal support structure which had been screwed to the building surface. This support structure should be constructed by a qualified installer. A wooden support structure could be employed, but it would have to be primed and sealed thoroughly to prevent saturation and subsequent transmission of moisture to the top panels. Again, as with all industrial products, care should be taken to follow manufacturers recommendations.

A product was discussed for peripheral waterproofing, Atex Novacolor. This is a water based rubber coating material which is designed for roof patching. A comprehensive examination of the potential mural site should be made to observe and detect moisture flow. It may be necessary to take the step of installing flashing or eaves troughs to divert water flow away from the surface of an installed mural. Moisture is one of the main causes of damage to outdoor murals.

The question of alternate materials for indoor large scale mural work was raised. The use of Bungee Banner was suggested for these applications. This is a strong canvas anchored and suspended by a bar mechanism and stretched taut by bungee cords. (a highly elastic tensile cord that clips to the bar at the edges and pulls the canvas taut). This type of system is widely used for exterior use where extreme longevity is not required. However, given that it is sufficiently strong to be erected and operate in wind and weather suggest that it would be highly permanent in an indoor environment, where sun and moisture would not cause depredations to the fabric.

A review of the discussion regarding different sorts of elevating mechanisms follows:

Scissor lifts: A type of life truck, electric, gasoline or propane powered, which lifts by the scissors effect of metal frame arms. Very safe as the weight is centered over the lifting platform. Not suitable for uneven ground. Maximum working height on the larger lifts is about fifty or sixty feet. Easy to learn to operate. Excellent for mural work. There can be an access gap between the lift’s ground height and the floor, as the work deck of the lift is about 4-6 feet off the ground in lowered position.

Scaffold: Metal frames and plywood covered decks, assembled to different heights. Can be erected to great heights but especially useful for mural work at one or two stories. More fatiguing to work than a scissors lift, but possibly cheaper for long term use and keeps the artist in good shape. Can be adjusted for use on uneven ground. Anything over three scaffold levels high must be base plated and jack-screwed to level and requires use of plastic fencing around the base for safety codes. For a one storey mural, a single or double cell height on wheels can be rolled along in front of the mural for a very cost effective work platform solution. A heavy base frame with automobile wheels and large rubber tires, like a kind of heavy wagon can be used to erect scaffolding on. This is useful on rough surfaces, and may be stabilized with outriggers.

Swing stage: Typically used by window washers and maintenance crews as well as muralists, the swing stage is a long narrow platform with safety rails. It is suspended from metal arms off the roof of the building, by process of counter weighting, and raised and lowered by electric motors on cables at either end of the stage. Can be used at skyscraper heights. Good for height work and safe if set up correctly, but must be installed by a qualified contractor. A mistake in the calculations of the counter weighting could have disastrous consequences. Relatively easy to learn to operate from scratch, but more care must be taken in its operation than a scissor lift. Important to avoid tangling or jamming the cables as they feed into the electric motors.

What is the best primer?
There is no economy to be gained by using low cost or economy products in any type of painting but especially with regard to primers for exterior mural work. The primer is the coat on which all subsequent treatments depend and as such must be of top quality to ensure a good life span for the finished work. In short, the use of top quality, top of the line products is highly recommended for priming applications.

For priming on Masonry or Stucco use the best quality available exterior latex primer. For situations where there may be holes in pointing or a rough surface, use a thicker formulation of latex primer known as block filler intended to fill in holes and cracks in a previously unpainted surface but may be used over old paint as well. For full treatment use a coat of block filler then a coat of regular primer. One of the brands of block fuller that was mentioned was Polycrack (#1 latex or #3 Alkyd). Some of the manufacturers whose products may be relied upon for quality are Pratt and Lambert, Pittsburgh Paints, Para, Benjamin Moore. For applications where stain coverage is required Zinsser Bullseye 1 2 3 is a high hide primer sealer that will cover fire damage, staining, and resists bleed through to provide an even topcoat over an uneven base and is a useful product. Pittsburgh Paints will sometimes send a scientist on site, on request, to advise appropriate materials, and will willingly provide a catalogue and material safety data sheet.

What kind of sealer (clear) coats over finished murals should be used?
The use of sealers can prove problematic. In the event that the decision is taken to employ a sealer coat, it must be done with the strict knowledge that the paint media and sealer coat are chemically compatible. Check material data sheets or with manufacturers to determine this information. Sealers tend to be highly non porous which can prove detrimental over surfaces, especially brick where moisture transfer is organic to the site. Sealers may change colour over time with a detrimental effect. Some acrylic varnishes are being manufactured which may prove highly compatible with acrylic painted murals. Check with Binney and Smith who manufacture Liquitex acrylics for their recommendations on sealers for exterior mural work. Acrylic varnishes must be applied with great care as over-brushing or over- rolling a wet application of clear coat can produce a milky or grainy effect in the finish which has an undesirable appearance when dry. If compatible and applied carefully sealers may add some life span to a finished piece, however, when in doubt avoid an extra coating over your paint system which may fail.

How important is the site location of a mural?
In order to get the best life span out of exterior mural work, always employ the following maxim: “site selection is absolutely critical to the life span and general success of the mural project”. Check the composition of the wall in question for efflorescence or signs of conspicuous moisture passage or damage. Look for a very dry inert site for best results and remember that a south or east facing site may be warmer to work on than a north or west exposure, but may exhibit fading comparatively sooner. Murals are more visually effective in shade than in direct sunlight, especially if there is a surface texture like brick pointing or stucco. When in doubt about the physical suitability of a site, consider other sites.

What is the best paint to use?
Finally, some of the paint media that were mentioned as tried and tested in mural application included but are not limited to: Stevenson (acrylic) Nova (acrylic) Golden, and Liquitex. The above mentioned materials are marketed as artists material and generally have high viscosity and good light fastness and mixing capabilities. Many artists paint murals with commercial latex paints, which are generally lower viscosity and may not mix as readily as pure pigment to obtain true shades, due to the admission of tertiary tones into the colour bases. This is not a problem where flat “line and tone” style of mural is desired and colour matches can be taken from manufacturers color chips. If a “palette mixing” style of mural is required where custom shades are mixed on site to render a painterly artwork following a maquette, then artist materials are probably a better choice. Commercial latex is generally used for spray applications, but the requisite thinning of media (and resultant loss of integrity to the binder in the paint) generally tends to preclude the use of spray technique for long term on-site murals.

Sady Ducros is an artist with a strong affinity for working with youth and the community, Sady has completed numerous outdoor murals and community art projects, as well as doing commercial murals. In the summer of 2001 Sady worked with Mural Routes as the Youth Coordinator for two murals on Kingston Road and also traveled to Sudbury where he coordinated a youth mural entitled Respect for Myths and Mirrors.

John Hood is an accomplished mural artist with numerous outdoor murals to his credit, John’s work can been seen across Ontario in towns such as Athens, Collingwood, Fort Frances, Kenora, Toronto and Welland, John has been affiliated with Mural Routes from its inception and as an ex-officio member of the board of directors, he continues to provide advice and assistance to Mural Routes.