Talking Color  

Color is an all-important aspect of our lives. It can affect our state of mind, inspire action, operate as a soothing influence or a call to action. In architecture, color has great potential to have a major effect on the environment and to create a unique aesthetic appeal in a particular space. Color is probably the first thing we notice about a space and sets the stage for our experience of it. For years, European architects have made good use of color in the built environment, while their American counterparts have tended to downplay it, gravitating to safe understated shades, and sometimes merely as accents or as afterthoughts rather than an integral part of the design statement.

Yet as research furthers our understanding of how color, light, and contrast affect emotion and sensory abilities, understanding how to use color has become a vital tool for architects and designers in every segment of the built environment from healthcare and education to industry, retail, and commercial exteriors and interiors. How to employ color effectively in a meaningful, integrated way and select the architectural coatings that will meet these goals, however, can be challenging.

This article will continue the conversation about color in the built environment, highlighting such aspects as the chemistry of color paints, new and traditional offerings in the marketplace as well as performance considerations and answers to some of the most frequent questions architects pose to paint manufacturers. Also covered will be “paint in action,” case studies of how exterior architectural paint has been used on buildings of note in the U.S.

Why Consider Color?

The fascination with color is longstanding and deep seated. Throughout the ages, the use and arrangement of color has led to the creation of beauty and harmony with an instinctive feel for its psychological effect. In the built environment, the colors of many structures provide unique insights into the culture and the materials available at that time in history, from the striking reds of Japan's Shinto shrines to the golden pyramids of Egypt and the multi-hued domes of St. Basil's in Moscow.

In long ago times, color was provided by readily available natural materials—red ochre, a form of iron oxide; yellow ochre, an iron silicate; black pigments from charcoal; white pigments from calcium sulfate, or gypsum; softer greens and pinks from vegetable dyes. Over the centuries, architects have created drama in buildings through color, be it derived from pigments, paints, stained glass, or mosaics. In recent history however, despite the emergence of color science, color has been the most neglected aspect of architectural design, taking a back seat to spatial dimension. Conservative choices, such as shades of whites, beiges, bronzes, metallics, and grays have remained the leading color choices for many years, arguably to create an aesthetic that will not seem quickly dated.

Still, building owners and architects are increasingly re-evaluating the power of architectural color, looking to color trends and using color to achieve certain goals. Restaurants are using color to stimulate the appetite, industrial designers to increase efficiency, relieve eyestrain, and reduce fatigue. Designers of schools are employing color to reference various developmental levels from bright primary colors for young children to more serene blues and greens conductive to study for older students. Healthcare designers use color to inspire confidence and promote the healing process, with some practitioners claiming the right colors and combination of colors can actually enable medical diagnosis and surgical performance.

There is increasing evidence that color has a profound effect on the human experience as well as in changing and improving the aesthetic appeal of particular areas. As color trends take stronger root and the power of architectural color is re-evaluated, architectural coatings will play an ever-increasing role. Accordingly, architects should become familiar with the fundamentals of these coatings and how to specify them for enduring aesthetic results.

The Chemistry of Color in Architectural Coatings

Architectural coatings are comprised of a resin and a pigment. The primary function of the resin is to provide adhesion, flexibility, hardness, moisture and chemical resistance, and resistance to UV light. Pigments provide the color and often determine the performance of a coating. It is the chemical resistance of the pigment that is key. Pigments are either inorganic or organic, and in some instances it takes both types to create a particular color space. Inorganic pigments are metal oxides and mixed metal oxides that have a high resistance to fade and are the most heat stable, chemically inert, UV- and weather-resistant pigments known. Generally, inorganic pigments are beige, tan, brown, and other earth tones.

Organic pigments, which are carbon based and often made from petroleum compounds, produce bright, intense colors; however, they are susceptible to fading and heat as UV and oxygen can penetrate organic pigments, breaking their chemical bonds.

The larger average particle size of inorganic pigments makes them opaque while the smaller particle size of organic pigments renders them transparent. In other words, organic pigments produce brilliant shades but with low coverage while inorganic pigments produce architectural coatings with high coverage and are used mainly where high opacity is required.

Applying Color to Metal—Coil and Extrusion

The way color on a building appears to a passerby is a function of the pigment itself, the substrate, and any clear coating applied over the color, as well as the method by which the paint has been applied. With architectural metal components, color is generally either spray applied or coil coated. Each method has its own unique characteristics. Coatings are generally applied to components that are already formed, while coil coatings are applied to flat metal that is later shaped into panels and pieces. Extruded and curtain walls components, then, will be spray applied, while roofing and side wall panels will be coil coated.

In spray application, the coating comes out the tip of a gun, and most applications are electrostatic, that is, an electrical charge is given to the atomized paint, and the part is grounded, so an electrical field is established between the gun and the part. The paint travels along the electrical field to that grounded part. The advantage here is that electrifying the coating allows for efficient transfer to the substrate during application.

Coil coating is a continuous and highly automated process for coating metal before fabrication. In one continuous process, a coil of steel or aluminum that can be as wide as 72 inches and moving up to speeds as fast as 700 feet per minute is unwound and both the top and bottom sides are cleaned, chemically treated, primed, oven cured, top coated, oven cured again, rewound and packaged for shipment. Typically the applicator roll turns in the opposite direction of the strip, and thus the process is called reverse roll coating. This process can place a significant shear on the coating, but it allows for high levels of control of both film thickness and color.

The difference in the two application methods and their planes of application necessitates a different rheology for the coatings. Rheology is the science of flow and deformation. Flow phenomena can be very complex. The simple action of stirring paint in a can involves flow patterns that can be a challenge for exact mathematical analysis. In coil coating, the application plane is horizontal and a high shearing stress is applied to the coating for a brief period when the application roll meets the moving metal strip. Having only a horizontal application plane means that after application, the coating will not run or sag. As a result of coil rheology and application, coil films have a slightly more uniform appearance for color and gloss, and a more consistent dry film thickness with a slightly smoother flow pattern.

With spray, a high shearing stress occurs briefly at the gun tip where the paint is atomized and charged. Application planes for spray can be in any direction or angle and often are vertical. As a consequence of the multi-angle applications, the viscosity of spray coatings must build back higher and faster following release of shear stress in order to prevent the coating from sliding or running down the various angles on the part. Spray rheology and application means that the part may have a slightly less uniform appearance for color and gloss and a bit more variation in dry film thickness across the part. The flow pattern also will be slightly more irregular than a coil coating.

The coil and extrusion systems are basically the same polymeric systems, varying only in rheology. The coatings themselves have essentially the same durability. However, coil allows a greater variation in substrates, while extrusion is only used to coat aluminum.

What’s Available in Architectural Coatings

The coating industry is constantly refining and adding offerings to their product lines.

Lights and Brights—Colors That Work Within Warranties

In architectural building components, the chemical resistance of the pigment is crucial. This sometimes restricts color spaces that can be achieved, as no matter how well a coating is made, certain colors are more affected by the outside environment than others. For example, bright colors such as yellows, oranges and reds will fade faster.

Color warranties are based on the percentage of organic vs. inorganic pigments used to create the final color. Typically, standard warranties cover film integrity, chalk, fade of a coating, and gloss retention. Loss of film integrity, chalking, color fading and gloss retention are primarily the result of a breakdown of the resin system, and as the resin system degrades the coating surface gets rougher and gloss decreases and the pigment particles in the coating become exposed and more easily removed through natural processes. The use of a clear topcoat will improve the durability of any coating, whether “borderline” bright colors or otherwise. A manufacturer's color technicians, however, are challenged to select affordable pigments for coatings required for durable applications. High durability requirements limit color space and warranty options.

Pearlescents

Many designers often seek a metallic look for their colors. Pearlescent or nacreous coatings or pigments possess optical effects that serve decorative purposes, offering eye-catching luster and color effects. With micas and metallics, there is a visual appearance factor that is not seen in solid colors. Creating this look adds several other elements into the process because it actually involves tiny flakes of reflective metal or refractive mica pigments added into the paint mix. Their unique effect is achieved by light interference rather than light absorption. Pearselscent pigments are produced by placing a metal oxide layer on a mica platelet, with color and luster effects controlled by the coating thickness and the mica particle sizes.

In addition, manufacturers are now offering coatings in rich, pearlescent colors that appear to shift in color when viewed from different angles or sunlight. Whether an effect or pearlescent pigment, these coatings function according to the same principal. The pigment has a core material, which could be mica (either natural or synthetic) or a silica with a pigment (usually an iron oxide, titanium dioxide combination precipated on the surface). Both the change in color and the degree of color change is controlled by the composition and thickness of the core and the precipitated pigment.

The color shifting paint is applied in a three-coat system; the colors consist of a primer, basecoat (to enrich color) and pearlescent mica coat with mica flakes or combinations of mica and aluminum flake. The color shift paint is available for both extrusion and coil products. The color is controlled not only by the topcoat and pearlescent mica coating, but also by basecoat. It is the mica flakes that create the consistent, iridescent gradient look. The basecoat consists of ceramic and inorganic pigments. The pigments are best suited for long-life external use on monumental high-rise structures and pre-engineered buildings, including architectural and residential metal roofing systems, composite and insulated metal wall panel systems, and metal roofing and wall panels systems. Many such pigments are available in a range of gradient pearlescent colors from white to silver and can be ideal for architects interested in achieving effects from a silvery color with a hint of a distinctive quality to a dramatic glittering aesthetic. Typically, these paints carry advanced weathering protection.

Special Effects Pigments

Some pigments have been manipulated to produce special effects. Textured coatings from simple to complex, for example, can be used to emphasize certain elements, design or color, strengthen a coating or mimic a design style. The texture is achieved by adding an additive to the coating that creates the effect when baked in the oven.

Print coatings are another type of special effect pigment. Many companies want distinctive coatings that differentiate their brand image—a need that is being increasingly met by new coil coating technologies, unique coatings, ink and film systems, and multifaceted prints with reduced cycle times. In this process, a base top coat is applied to a coil then a patterned coil applies an ink coat to create the desired decorative pattern. Metal panels can be made to look like wood, granite, tile, stone, camouflage, various levels of weathering, or virtually any desired effect.

Solar Reflective Coatings

With rising energy costs and the growing global demand for energy reduction, there is an increased need for cool coatings. Roofs, particularly, can benefit from cool coatings as they are one of the least energy efficient components of the building envelope.

Both Solar Reflectance (SR) and Thermal Emittance (TE) are important factors in relation to the temperature a roof will reach in direct sunlight. SR refers to the amount of solar energy that is reflected by the roof. TE is the amount of heat energy a roof can reemit in the form of infrared energy into the atmosphere. Both are measured on a scale from 0.00 to 1.00, with 1.00 being the most reflective or emissive. The closer the values are to 1.0, the more efficiently heat is reflected and emitted. The greater the amount of solar energy reflected from the roof surface, the less energy the building will need to cool down. In fact, peak cooling energy demand may be reduced by up to 15 percent.

One way to a cooler roof is via solar reflective pigments, which have been altered physically and chemically to reflect infrared radiation, while still absorbing the same amount of visible light—this keeps the temperature of the roof lower, and reduces the amount of heat transferred into the building below. They are the same color as less reflective pigments, yet stay much cooler. Cool roofs can influence the “heat island,” a term used to describe built-up urban areas that are hotter than their surrounding rural areas. The urban heat island effect is common to cities in industrialized nations where the outside air temperature is 5 to 10 degrees Fahrenheit hotter than outlying areas.

In addition to contributing to LEED points in the Sustainable Sites, Energy and Atmosphere and Materials and Resources areas, solar reflective coatings can contribute to the credit for Heat Island Reduction, providing they have an SRI equal to or greater than the designated values set by LEED. The accompanying figure shows SRI targets for LEEDv4.

Solar reflective pigments are also used on wall panels and extrusions to keep a building and its components cooler than bare aluminum, anodized aluminum, or steel. It is important to note, however, that it can be difficult at times to achieve the required solar reflectance and also the desired color match. In some cases a specified solar reflectance is simply not achievable in the desired color space.

What Architects Want to Know

Following are questions often posed by designers to manufacturers of architectural coatings.

How Do Swatch Book Colors Translate to Architecture?

Sometimes architects will request a color from a book of swatches, and that can raise issues if the specified coating requires a long-term warranty. To coat a piece of paper such as in a swatch book, essentially any pigment will do because there are no durability requirements. Pigments used on building components must do more than just show a color, however. They also have to be durable to the elements, which adds more chemistry to the equation. When the color choice is submitted to a manufacturer, there may be only a very limited palette of pigments that have the requisite durability to meet the desired warranty.

Further, color is not as simple as red, blue, yellow or green. There are countless variations on the color spectrum, and hitting the mark with color is a complex process that involves effort, technology and chemistry. Color is defined by the chemistry of a pigment and the type of light that shines on it. Using only one light source, a given color could be matched with multiple pigment combinations, but change the light source and these matches will look visually different from one another—they are considered a Metameric match. Colors that shift relative to one another when a light source changes are said to be metamers, or to be exhibiting metamerism.

Sometimes color matches submitted to a design team for approval may look off the mark under fluorescent office lights. It is important to take into account the kind of light source used to view the coated panel. Colors are matched using a daylight illuminant or source, and if the color match is viewed under fluorescent lighting, the chip and the match may not appear to be as close as desired.

In an ideal world, samples to be matched are first analyzed in reflectance spectrophotometers. Every pigment has its own reflectance curve or “fingerprint.” From there, manufacturers can determine a sample's pigmentation and thus avoid producing a metameric match. In knowing the pigmentation a manufacturer will also know the extent of that pigment's durability. In some cases, only a metameric match will be possible under certain warranty considerations. When a metameric match must be submitted, manufacturers default toward a daylight (D65) light source for the match—this simulates the spectrum of visible light at noon, a roughly even distribution at all visible wavelengths. While metameric matches are frequently accepted to acquire the desired warranty, sometimes a less durable pigmentation match with a clearcoat application will be specified with a reduced warranty proposal.

Are Coatings Fire Rated?

Fire ratings are expressed as a duration of time, such as 1 hour, 1.5 hour, or 2 hour, for which a passive fire protection system can withstand a fire resistance test protocol. These hourly ratings are based on ASTM E-119 Fire Tests of Building Materials. Hourly fire ratings, however, are assigned only to complete assemblies of structural materials for buildings, not to coatings themselves. The principle variables for a fire rating determination are the number of layers in the wall or flooring; the type and thickness of the metal or wood; the type, thickness, and arrangement of the sub-girt, fastener numbers and composition; and the type and density of the insulation. The composition of a thin layer of an exterior organic surface coating on a wall panel assembly, when compared to the aforementioned variables, would have no significance in the final fire rating, particularly when the vast majority of fires originate inside a structure.

More to the point for surface coatings would be the Flame Spread and Smoke Developed Indices. A study on the flammability of paint was conducted by the National Paint and Coatings Association on a wide variety of paint products and systems over a variety of substrates. The study's determination was, “…conventional paints and coatings do not increase the flame spread of either non-flammable or flammable substrates upon which they are applied. …any fuel contribution or smoke density increase is insignificant when compared with the contribution of the substrate itself.” Test methods are defined in ASTM standard E-84. The Flame Spread and Smoke Developed Index for all varieties of paints tested ranged from 5 – 15 and 0 – 20, respectively. Class A or I ratings range from 0 – 25, Class B or II from 26 – 75, and Class C or III from 76 – 200 with reference standards being asbestos cement board at 0 and red oak flooring at 200. On the basis of this testing all conventional paints and coatings (including PVDF systems) have been assigned a Flame Spread Rating and Smoke Developed Rating of Class A or I when applied over Class A or I rated surfaces.

How Many Coats are Needed?

Many architects work with AAMA (American Architectural Manufacturers Association) specifications, which don't call for a certain number of coats. Instead, they provide minimum total dry film thickness requirements and other end use specifications, such as gloss retention, chalk rating and color fade following a period of exterior exposure. The number of coats applied to a component can vary, depending on the project specifications. It is often two or three coats, or sometimes two coats of color and a clear coating that constitutes a third coat. A third coat will add an extra barrier layer and will protect better against UV degradation and hydrolysis, which are the principal mechanisms of coating degradations in an exterior environment.

Color: The Conversation Continues

Color in the built environment is a growing trend. The potential exists for architects to use color effectively and integrate it so as to support occupant comfort and efficiency in a wide range of settings. As has been seen in several high profile structures, architectural coatings can contribute to the aesthetics and functionality of a structure consistent with intended use and environmental concerns. Yet when considering appropriate colors, it is important for an architect to be aware of what constitutes color and what factors can impact the appearance of a given component. There will be projects where the design requirements are in conflict in terms of color and performance requirements. Architects who are knowledgeable of the coating system performance capabilities when establishing or meeting specifications for a given project will be helping to ensure that the potential of color is realized on their project.

 

For over 200 years, Valspar has been a leader in the art and science of coatings that excel in both beauty and function. Its expansive range of superior coatings comes to life through a full palette of colors and surface textures to meet the most demanding environmental conditions and designs. www.valsparcoilextrusion.com