The Difference Between Varnishes, "Graffiti" Coatings, and Consolidants

Artists are often saturated with many options when it comes to choosing the right protective coating after painting their murals. Much of the information available, whether online or obtained at local paint stores, don't provide a complete picture of the long term challenges murals face as they age. Coating materials are often designed for blank walls, or painted walls–not fine art. Many of the options available either damage murals by not remaining optically clear, bind heavily to the painted surface and become permanently part of the fine artwork, or are products toggled together by graffiti removal companies interested in expanding their profits. Murals are fine artworks and they require precise materials with solutions for every situation they will encounter as they age.

Murals are materially different from painted walls in that they are created with multiple colors, over multiple layers, sometimes using diverse materials and techniques. Additionally, mediums and modifiers during the painting process makes each mural chemically diverse, all based on how the artist prefers to paint. Some artists will create murals using donated outdoor paint combined with fine art paints left over from their previous commission. All of this introduces dozens of variables that make most all commercially available varnishes and coatings unsuitable for short and long term preservation of outdoor murals.

So what is the difference between varnishes, sacrificial and non-sacrificial coatings, and consolidants? The options range between polymers, urethanes, siloxanes, polyolefins, and specialized resins and plastics. 

Coatings are incredibly diverse. When a mural artist goes on the search for a protective coating, it is usually to accomplish one of two goals: preserve a mural from UV degradation and the environment, or protect a mural from tagging or buffing. First, let's look at preservation coatings. 

Varnishes, like what are available in art stores, work by dissolving a resin in mineral spirits. They include additives that adjust the dry time or sheen, and some include ultraviolet light absorbers. In the short term, these products remain removable in mineral spirits, but as time goes by, the resins become brittle, and can delaminate and lose their solvency as UV light alters their chemical structure. Varnishes tend to be glossy and create a specular reflection that many artists dislike. Solvent-based varnishes are made with mineral spirits that are flammable and produce noxious fumes that can irritate the skin and lungs. Given that most murals average around 800 square feet, that is a lot of chemical exposure that artists will need to put themselves through!

While varnishes may preserve murals by binding additives to a paint surface, they are not as suitable for protecting against unwanted tagging or buffing. In those instances, artists turn to "anti-graffiti" coatings, which are often coatings designed for plain building substrates. Let's look at effects of protective coatings designed to prevent tags, bombs, or buff paint when used over murals.

Virtually all "anti-graffiti" coatings are designed to be used over blank walls because they depend on harsh solvents to work. When used to prevent tagging or buffing over acrylic or aerosol murals, "anti-graffiti" coatings discolor or chemically scar the sensitive paint beneath. These types of coatings, which are often sold at local paint stores and big brand hardware stores, are not suitable for fine art and will create multiple problems in the short and long term. These kinds of coatings depend on solvents to melt unwanted paint, and this often affects the coating and the artwork beneath. Such solvents discolor paint, weaken binders, and are hazardous to handle.

Non-sacrificial coatings, such as urethane and polyurethane coatings over time lose their opacity and film flexibility. Urethanes/polyurethanes are non-breathable and trap moisture, which when exposed to ultraviolet light, causes the film to crosslink and become brittle. We are regularly consulted by artists to address the removal of these difficult coatings because they quickly lose their performance and opacity, and before long, they begin to physically damaging the delicate paint layers of a mural. These “anti-graffiti” coatings are often paired with highly corrosive or toxic solvents that are not designed to carefully repair tags without damaging the paint underneath. Non-sacrificial acrylic-based polymer coatings tend to be soft and bind with solvent propellants used in tags.

Silicone and siloxane coatings, including polyoleofins and fluorinated coatings are very expensive, contain hazardous chemicals, and lose their performance after a few removals. They are not easily removable and bond permanently to the mural surface, restricting future restorations and in-painting.

Semi-sacrificial coatings are often not designed for fine art murals. They are instead developed for concrete or brick walls where specialty solvents can be used to remove tags. Each time, they lose their strength because the solvents used during each repair soften the integrity of the coating. In situations where murals are regularly tagged or bombed, most coatings fail to hold up to the needs of fine artworks.

Consolidants are a special class of resins suspended in solvents. There are several options available on conservation websites, but all are suspended in toxic and highly flammable solvents that put the user at risk of health hazards or worse. Consolidants must be of the highest purity or they will yellow in sunlight or become brittle. They must be carefully formulated or they risk film forming without adequate integration into the paint surface. Hazardous consolidants are limited in size because they are restricted by hazardous material shipping laws, which require customers to pay additional fees on top of regular shipping. When artists are on limited budgets, these materials end up being too costly and create far too much risk and exposure to toxic chemicals.

At MuralColors, we have created a specialized system that carefully balances the needs of fine art murals and artists–ColorShield and OverCoat. 

ColorShield is the first non hazardous consolidant for fine art murals that uses the highest purity resins available and a high concentration of high performing ultraviolet light absorbers and hindered amine light stabilizers that extend the life of paint. The resins are stable to a range of chemicals found in the environment and withstand repairs into the future. It ships easily and comes in various small and large sizes for residential murals or outdoor large wall murals. Use ColorShield with OverCoat when you need your mural to have the maximum longevity outdoors.

OverCoat is a balanced semi-sacrificial UV coating that further protects against ultraviolet light and remains resistant to tags and bombs, but completely removable using our specialized MuralWash soap. It is the first mural coating designed to be selectively removable without harsh solvents, allowing future maintenance without affecting the delicate paint surface. OverCoat is water based, can be used indoors on its own, or outdoors over ColorShield, and ships easily in small or large sizes. OverCoat is suitable for use on its own when tagging is not a concern, when indoors, or project budgets are tight, and high quality UV protection is needed.

Combined, these products offer artists a balance between high performance, safety, and longevity.

Interested in learning more? Call us at 323-601-5000 or reach us at hello@muralcolors.com