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Mural Painting

Murals include a variety of techniques including fresco, encaustic, mosaic, stained glass and photography. Most contemporary artists will either paint on canvas and attach it to a wall or paint directly on the wall itself. The word mural is actually derived from the French word “mur” meaning wall. Acrylic paints have proven themselves to be one of the most durable paints available for exterior as well as interior mural painting.

Selecting a Mural Paint

The surface to be painted and the environmental exposure of that surface are important aspects to consider for selecting the right type of paint. The technique and painting style of the artist must also be included. No paint can withstand all environmental conditions such as sun, rain, cold, heat, acid rain and air pollution. Acrylic water emulsion paints however, have proven themselves to be one of the most durable paints available for exterior as well as interior mural painting.

Advantages of Using Liquitex Acrylics for Murals

Liquitex is the original artist's water-based acrylic emulsion paint. It offers the advantages of a wide range of unique permanent colours, great versatility in mediums, clear resin system, superior adhesion, detailed label information, and technical support. Liquitex makes two types of acrylic paint and acrylic paint markers suitable for murals:

Liquitex Soft Body Professional Artist Colour
  • Consistency similar to heavy cream. Can be spray applied.
  • Dries to a smooth, even surface with good leveling that shows little or no brush marks.
  • Pigment load is equal to Heavy Body Artist Colours and is ideal for large mural coverage. Available in large containers.
  • Flat paint film catches less dirt and requires less cleaning over time.
Liquitex Heavy Body Professional Artist Colour
  • Heavy-bodied paints have a smooth, thick, and buttery consistency with oil-like performance.
  • Used in mural applications for a heavy build up of paint texture (impasto) and brush stroke.
Liquitex Professional Paint Markers
  • Precision nibs for ultimate control 
  • Dries to a smooth, even surface.
  • Flat paint film catches less dirt and requires less cleaning over time.
  • Use together with Liquitex Heavy Body, Soft Body or Spray Paint 

Coverage:

  • Soft Body Concentrated Artist Colour will cover approximately 400 sq. ft /gallon.
  • Coverage is reduced with a rough surface.
  • Coverage is extended when spray applied and surface is well sealed.
  • To double paint coverage of either Medium or Heavy Body Acrylic, mix 1 part Acrylic Colour to 1 part Liquitex Opaque Extender or Gel Extender Medium.
  • Use these mixtures during underpainting of murals to economically double the volume of paint. For best permanence, the top layers of the mural should be painted using Lightfastness I rated colours with no Opaque Extender added.

Mural Surfaces

False and Separate Walls

  • The best support for mural painting is a false wall erected in front of an existing wall.
  • This eliminates the dangers inherent in expansion and contraction of plaster and masonry. It also protects against cracking, peeling and water damage and allows for easy removal of the mural.
  • The mural wall can also be a stretched canvas panel or canvas adhered to a rigid panel. A false wall for interior murals allows the artist to paint the mural in the studio rather than on location.

Existing Walls

  • Murals can also be painted on existing wall surfaces. Proper surface preparations must be observed to insure longevity of the mural.
  • A surface that has been previously painted will not be as permanent as a surface that has never been painted or has been stripped of all existing paint.
  • The surface must be free of any previous oils and silicones or paint may peel. Paints and oils can be removed with the proper solvents or by sand blasting before painting.
  • Surface must be "dust" free and not subject to extreme moisture behind the wall to be painted (unless waterproofed).

Surface Preperation

The longevity of a mural is directly related to the surface preparation. Selecting a Surface

  • It is important that the surface does not contain moisture. New concrete may not be free of moisture for 2 to 3 months after drying.
  • Make sure the surface will not get wet from water seeping through existing outside walls. Moisture can be absorbed behind a substrate and cause the paint to peel from the surface. (A leading cause of failure)

Cleaning the Surface

There must be no grease, wax or oil on the surface and the surface needs to be structurally sound and free of loose particles and dust.

  1. Remove all existing loose particles or damaged painted surfaces. If the wall has been painted with oil paint or is peeling, strip all existing paint.
  2. If the surface has been painted with acrylic paint, sand entire surface.
  3. Clean surface with a degreaser, such as TSP mixed with warm water.
  4. If mold or mildew is present, use a stiff brush and scrub with a mixture of 1 part bleach and 3 parts water. Rinse twice with warm water and allow to fully dry.

Applying the Ground (Priming the Surface)

After the surface has been cleaned, it must be prepared to accept the paint.

Fixing Cracks and Uneven Surfaces

  • For smooth surfaces: Brush on one coat or spray two coats of Liquitex Matte Medium.
  • For rough surfaces: Trowel on one-two coats of Liquitex Matte Gel Medium.
  • Allow to fully dry. Mediums are clear/ translucent when dry and cloudy/milky when wet.
  • Painting can proceed over these sealing coats, however at least two coats of gesso are recommended.
  • Most artists prefer a white surface to use as a basis for the mural cartoon or sketch and to establish colour relationships.(By using gesso)

Priming The Surface

  • Apply Liquitex Acrylic Gesso for a white ground, Liquitex Coloured Gesso for a coloured ground, or Liquitex Clear Gesso to maintain some visibilty of the original surface.
  • If necessary, thin gesso with no more than 50% Matte Medium. Brush or spray apply.
  • For spray application, thin gesso with a mixture of 50% Matte Medium and 50% water. This mixture reduces tooth and absorption. Over thinning with water alone can cause cracking or result in poor adhesion.
  • Multiple coats of gesso can be applied and wet sanded to produce a smooth ground. Wet sanding will make a flexible surface (canvas) somewhat brittle.

Various Mural Surface Preparations

New Wood:
  1. Sand surface.
  2. Seal with 1 coat of Matte Medium.
  3. Apply 1-2 coats of gesso.
  4. Paint with Medium or Heavy Body Artist Colours.
  5. Apply isolation coat of Gloss Varnish.
  6. Let dry 48 hours.
  7. Apply 1-2 coats of Matte or Gloss Soluvar.
Painted Wood:
  1. Remove loose material.
  2. Sand or Strip.
  3. Seal with 1 coat of Matte Medium.
  4. Apply 1-2 coats of gesso.
  5. Paint with Medium or Heavy Body Artist Colours.
  6. Apply coat of Gloss Varnish.
  7. Let dry 48 hours.
  8. Apply 1-2 coats of Matte or Gloss Soluvar.
New Masonry:
  1. Must be dry, cured, and dust free.
  2. Apply Matte Medium for smooth surfaces, Matte Gel Medium for rough surfaces.
  3. Apply 1-2 coats of gesso.
  4. Paint with Medium or Heavy Body Artist Colours.
  5. Apply isolation coat of Gloss Varnish.
  6. Let dry 48 hours.
  7. Apply 1-2 coats of Matte or Gloss Soluvar.
Painted Masonry:
  1. Remove loose material.
  2. Clean. Sand or Strip.
  3. Must be dry and cured.
  4. Apply Matte Medium for smooth surfaces, Matte Gel Medium for rough surfaces.
  5. Apply 1-2 coats of gesso.
  6. Paint with Medium or Heavy Body Artist Colours.
  7. Apply isolation coat of Gloss Varnish.
  8. Let dry 48 hours.
  9. Apply 1-2 coats of Matte or Gloss Soluvar.
New Sheetrock:
  1. Apply an acrylic emulsion compatible industrial sealer such as Aqualock.
Unprimed Painted Metal:
  1. Remove grease, dirt and solvents.
  2. Sand surface.
  3. Wash with a prep solution for the painted metal being used.
  4. Apply an acrylic emulsion compatible primer (auto parts stores are a good source).
  5. Apply Matte Medium for smooth surfaces and Matte Gel Medium for rough surfaces.
  6. Apply 1-2 coats of gesso.
  7. Paint with Medium or Heavy Body Artist Colours.
  8. Varnish with isolation coat of Gloss Varnish.
  9. Let dry 48 hours.
  10. Clean with mineral spirits and apply 1-2 coats of Matte or Gloss Soluvar.
 

Painting

Choosing Colours

Since outside murals are subject to the harshest environmental conditions, colour selection is very important. The Liquitex Hand Painted Colour Chart and "How to Mix and Use Colour" Book, list all colours along with their lightfastness rating, mass tone, tint, glaze and colour intermixes. All Liquitex Acrylic Colours list on their label the permanency of pigments used according to the standards established by the American Society for Testing and Materials (ASTM). Refer to Liquitex Technical Information for more information on Lightfastness Ratings. Only Category I pigments are recommended for outdoor mural painting.

Paint Application

Painting can proceed after surface preparation. The drawing can be scaled up using a grid system or transferred to the surface with chalk or cartoon and "fixed" with a spray coating of 50% Matte Medium and water.

Thinning Colours during Painting

  • If acrylic colours need to be thinned use a mixture of 50% water and Gloss Medium & Varnish or Matte Medium. To slow drying, use Slow-Dri Fluid Medium.
  • Do not use water only for thinning. Outside murals exposed to weather need maximum film integrity. Too much water will weaken the paint film. Temperature, Moisture and Humidity During Exterior Painting.
  • Ideal temperature: 65° - 75° F; Lowest temperature: 50°F.
  • Varnish application during rain may trap moisture, hinder adhesion and cause clouding. Painting must be absolutely dry.

Adhesion Test

To ensure proper adhesion, a test should be done either on a surface similar to the actual mural surface.

Directions:

  1. Apply the paint or medium to prepared surface and let dry thoroughly. Wait 72 hours for acrylic paint to cure before continuing. (longer in more humid conditions).
  2. When completely dry, score surface in a crosshatch pattern using a sharp knife.
  3. Apply masking tape firmly to scratched surface and firmly burnish.
  4. Remove masking tape slowly.

If any paint comes off with the tape, good surface adhesion has not been achieved. Either a different surface preparation is necessary or the particular support is not suitable for the paint or medium tested.


Finishing

Final Protective Varnishes

After the mural is complete, a final protective varnish should be applied to extend the life of the mural and protect it from weathering, pollution and dirt. The varnish should be a removable type such as Liquitex Soluvar to allow the removal of pollutants, dirt and graffiti. Mural varnishing occurs in two steps:

  1. Isolation varnish layer
  2. Removable varnish layer

Soluvar Gloss and Matte Final Picture Varnish Application

  1. Apply 1-2 layers of Gloss Varnish as an isolation barrier. This barrier physically separates the painting from the Soluvar Varnish and seals the surface. This allows a more even application of Soluvar Varnish and protects the painting surface when the Soluvar Varnish needs to be removed.
  2. To insure proper adhesion, clean surface with a lint free rag lightly dampened with mineral spirits.
  3. Apply 1-2 layers of Soluvar Varnish. Let dry 24 hours between coats.

Intermix Gloss and Matte Soluvar Varnish for a variety of sheens. Soluvar Matte Varnish contains matting agents that settle during storage. Gently stir with a wooden dowel or brush handle until completely re-dissolved. Do not shake.

Removing Soluvar Final Picture Varnish

  • If the mural becomes dirty or abused, removing the varnish can restore it. Cleaning will not affect the underlying painting if the varnish was properly applied.
  • Remove varnish in clean, well-ventilated area.
  • Wear a duel filter respirator (NIOSH approved) and neoprene gloves. Dampen a small piece of lint free, soft, white cloth with mineral spirits (not "odorless") or turpentine — nothing stronger. Do not use ketones or paint removers.
  • Work in small sections to assure procedure is working.
  • Work horizontally. Apply mineral spirits generously and allow it to lay on surface for 15-30 minutes. Check periodically. Longer times may be necessary, depending upon age of artwork and strength of mineral spirits. If varnish is not dissolving or dissolving slowly, use a higher strength mineral spirits or turpentine. Cover surface with plastic to slow down evaporation of mineral spirits. Stronger mineral spirits are not labeled as such, but have a stronger odor.
  • Rub cloth gently over a 1 square-foot area until varnish starts to dissolve.
  • Using a clean cloth and clean solvent, rub the area again to remove residue. Repeat this procedure for the entire area to be cleaned. If any paint colour shows on the cloth, stop immediately and allow the surface to dry.
  • Allow painting to dry before reapplying a fresh coat of Soluvar Final Picture Varnish.

For outdoor murals we would also recommend using a finishing layer of an outdoor varnish to increase the durability of your artwork. A good option would be a yacht varnish. This ultra-tough varnish can be pciked up at most hardware or DIY stores.

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