Materials and Techniques

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Mural Materials and Techniques
A Mural Project
Portland Murals Gallery

From Seed to Celebration on SE Division (by Site Painters), a mural created using recommended techniques.

Note: this information was gathered n 2004; some of the links may be out of date.

Getting Started 

  A mural needs to withstand the stresses of wind, rain, sunlight, heat, cold, dust, dirt, 
moisture, pollutants, foot traffic, touching, and tagging.

  This section will explain how to prepare a wall, and how to design and paint a mural 
that remains attractive and colorful for many years, through all types of environmental 
(and human) stresses.

   In Portland, spring into summer is the best time to start a mural project, since 
moisture is one of the greatest hazards during the painting process. Very cold (below 45°) 
and/or damp weather compromises the strength of the paint film. In general, murals started 
after October in Portland are in danger of not being completed until the following spring.
 

Preparing the Wall

  An ideal site for a mural has a smooth, clean, east facing wall with the protection of an overhang or courtyard--but, of course, most mural sites are not ideal! See Selecting a Mural Site for more information.

  Good mural sites are also generally above arms length, therefore ladders and scaffolding are vital equipment.

  A great deal of time can be saved and physical strain avoided by using the appropriate ladder. Keep in mind how wide, firm, and flat the ground below the mural is and if any trees, shrubs, or power lines impinge on the work area. If the wall is too high for a ladder, scissors lifts and 
scaffolds can be rented from the following:

• Beaver State, 5920 NW Saltsman Rd., Portland, OR 97210. (503) 223-6104

• Star Rentals, 1735 SE MLK Blvd., Portland, OR 97214. (503) 231-7300

  When renting equipment, check to see that it has been well maintained. Rental companies 
will also set up and take down scaffolding. For large murals, this may be worth the added expense.

  When beginning wall preparation, remember that the mural will only be as durable as all the layers underneath it.

  Inspect the wall for potholes, dirt, and old paint to determine the necessary amount of preparation. Inspect the roof as well for tar. Inspect any false fronts and sides of the building for cracks and leaks. 

  Look for signs of poor water drainage such as broken drains and roof flashing, standing water on flat roofs flowing into the wall, or water from the other side of the wall pushing out to the exterior surface.

  Remove any weathered material from the wall (e.g., loose paint or masonry, frayed or splintered wood) until there is a stable surface. Also remove very old paint, which will lose its binding strength and become brittle or powdery. Paint exposed to lime leaching out of masonry walls will also break down.

  Be sure to wear a face mask when removing paint. See Safety Links for more information.

  Fill cracks and holes with pre-mixed sand or cement filler, or other appropriate exterior grade materials.

  If the wall is in very bad shape, consider using fascia (a single-faced surface attached flush to a building or other structure), which can be mounted on the wall after the mural is painted.

  Fascia has several advantages. It eliminates the need for scaffolding, reduces problems with weather, and can be removed for mural replacement or preservation.

  The best fascia surface is 4 foot x 8 foot Medium Density Overlay (MDO) board, either ½ or ¾ inch thick.

  MDO board is plywood made with a high quality paper that has been soaked with phenolic resin solids and laid on exterior grade plywood. Sign companies often use MDO.)

  When the mural is done, a professional sign company or professional carpenter can build a frame and mount the fascia to the wall.

  Whether using MDO board or painting directly on the wall, it is necessary to start with a base coat 
of primer.

  Primer acts as a glue for the paint and sets up the wall for the application of paint.  Primer also 
seals against moisture and rust, consolidates dry crumbly surfaces, and blocks stains. When using fascia, don't forget to prime the edges as well as both sides of the board.

  If the surface has been previously painted with a gloss paint, dull the surface with sand paper and/or steel wool so the primer can be better received. Note that certain surfaces such as wood and cinder block may require more than one coat of primer. Select an oil-based primer for oil-based paints, or an acrylic primer for acrylic paints.

  Because there are many kinds of primers to help with different conditions, it is wise to ask for second opinions about primer. See the links in Art Supplies for more information.

  Remember: test out a product on a small corner before committing the whole wall to it. Also see Wall Preparation for more information.

Designing the Mural

  Metro Murals does not recommend designing or painting the mural directly on the wall or fascia.

  Instead the lead artist should create a series of drawings to scale. (See Selecting a Mural
Teamfor more information on the duties of the various members of the team.)

  To begin, the lead artist, in conjunction with the community, should take the details of the mural's location into consideration when creating the design drawings. Two considerations might be:

• Will the mural be seen mostly by pedestrians who can take time to view the images and details?

• Is there a traffic light, bus stop, or park that will lengthen a motorist's viewing time?

  A rule of thumb: the shorter the overall viewing time, the simpler the design.

  View the wall from different angles and distances to determine appropriate image sizes, and look for surface glare and reflections from the wall’s surroundings that might interfere with the view.

  Note that if the wall is textured (bricks, stucco, etc.), details will be lost in the shadow patterns. The painting will need to be bolder than the texture of the wall.

  Mural design should also take into account that while the mural is part of the building, the building is also a part of the mural. Colors interact and the color of the building could frame the mural.

  After the lead artist incorporates the ideas and images created by the community and produces a series of design drawings to scale, it's time to transfer the design.

  To transfer the design to the wall the artist needs to reduce the composition to a line art "cartoon."

  Cartoons are drawn to scale according to the measurements   taken of the actual mural space. (Make sure the measurements of the wall are accurate!) There should be no color or shading on the cartoon: if it is necessary to do a color mock-up, make copies of the cartoon and color those in.

  The most effective method of transferring the drawing to the wall is the "grid method" described in 
the four steps below.

2. Draw the same grid on the cartoon.

3. Cut the copy of the cartoon into the grid squares.

4. Have members of the community team draw the square they will be painting into the same grid square on the wall using pencil, conte crayon, or pastels.

  The grid method not only yields a much better mural than a freehand method, it helps build 
personal relationships. Since each image in the gridsquares must match up with the images above, below, or next to one another, members of the community team must negotiate with each other to 
make the images work.

  Two other methods of transfer include the projection of images: 

• On the wall, use a projector and trace the outline of the image directly onto the wall (this can 
  be a slow process, and the image is often distorted).

• Onto paper that's been cut into grid square sizes (as with the grid method), trace the projection, and do a graphite transfer to the wall (also a slow process).

  Snap or chalk lines are inexpensive and great for transferring sketches to the wall, and for making other straight lines within the grid.

  Charcoal, chalk, pencils, and/or construction crayons are helpful in sketching the outline of the figures in the mural. 

  Ordinary construction crayons are durable and cheap, and will hold up in most weather conditions. If the design is transferred to the wall in charcoal, chalk, or pencil it’s a good idea to go over the lines with a non-water soluble colored pencil (such as Berol Prismacolor). This step will save the drawing in case of 
rain (always possible in Portland).

  Now that the wall is prepared, the mural is designed, and the design is transferred to the clean and completely dry surface of the wall, it’s time to paint!                            

  Be careful about painting in direct hot sunlight, since this can weaken the paint/surface bond of the mural.

  In selecting paint for a mural, it is important to look for quality and durability. Poorly performing 
"cost saving" supplies can compromise the longevity of the mural and waste many hours of designing and painting.

  Below are some essential supplies:

• Masking tape. Necessary for keeping paint off parts of the mural that won't be painted.

• Small containers. Get containers with airtight lids for storing mixed colors for later touch-ups 
  and repairs. Be sure to reference the color on the container.

• Brushes. For a crew of ten, each crew member will need at least six high-quality brushes in a variety of sizes. Be sure to include detail brushes, even though they are usually the most expensive. Avoid inexpensive brushes, particularly those made of hog hair, which loose shape and shed.

  When painting, always using the largest manageable brush for a particular area. The coarser the surface, the beefier the brush needs to be

  There are several kinds of paint from which to choose:

• Oil-based paints for professional sign painters go on smoothly, blend well, have high color, need only one coat, and do not need varnish. But they do need turpentine or mineral spirits for clean-up, and (caution!) they do contain some lead. One-Shot sign paint is a good and popular oil-based paint. It dry quickly and furnishes proper brushing consistency with perfect working properties.

• Acrylic paints for professional artists blend well and clean up more easily than oil- based sign paints. Note that acrylics may require a Gesso primer underneath and a marine varnish on top.

• Exterior house paints are more cost effective than either oil-based sign paints or acrylic paints made for professional artists. Disadvantages include the need for multiple coats, a shorter life expectancy, and less concentrated pigments. Be sure to get top-of-the line house paints. 
  Acri-lite (Miller Paint) is an example of a good paint with both UV and mold protection. Plus the varnish is mixed into the paint.

  When selecting paints, check for the "lightfastness" rating. See How to Test for Lightfastness for more information. Also see The Problems with Fading Colors.

  Many bright colors fade easily. The following are good colors to use for outdoor surfaces:

• Red: red iron oxides (mars, burnt sienna), quinacridone red, and scarlet

• Yellow: yellow iron oxides (mars, raw sienna, yellow ochre) and titanium yellow 

• Green: light green oxide, green gold, and phtbalocyanine green

• Blue: pthalocyanine blue, cerulean blue, cobalt blue, and manganese blue

• Brown: brown iron oxides

• Black: mars black

• White: titanium white (non-chalking type)

  Note that oranges can be mixed from reds and yellows, purples from blues and reds.

  Colors should be made more transparent and flowing with a clear acrylic medium--not with water, which weakens the paint film and bonding.

  The following brands of paint are some of the best: