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