by Tammy Schroeder
Metallic architectural paint coatings offer a vibrant, visual appeal on buildings. When applied to architectural aluminum products, the resulting finish provides a lively shimmer or sparkle. This is produced by the way visible light reflects off the metallic flakes contained within the coating. Understanding metallic coatings’ optical dynamics, composition, application, as well as performance will allow designers and specifiers to achieve the desired appearance and intended durability for their projects.
Aesthetic appeal and typical applications
Architectural aluminum building products’ painted finishes protect the metal and enhance aesthetics. Similarly, when used on the exterior, these products enclose the building to shelter occupants from the weather and define the structure’s architecture.
Most often, metallic coatings are selected for exterior building products such as wall panel systems, canopies, and sun shades. Curtain walls, windows, doors, and entrances—also popular applications for metallic coatings—have both exterior and interior surfaces, which allow for dual finish possibilities when thermal strut is utilized. Different colors or finish formulations can be applied to each surface to match a room’s interior decor, while maintaining a consistent exterior palette and climate-focused performance.
Large-scale, high-profile projects featuring metallic coatings include healthcare facilities, entertainment and sports venues, university buildings, transit centers, and corporate campuses. Smaller projects can also make a memorable impression with metallic coatings applied on an aluminum feature wall, main entry, or decorative accent.
With the exception of bright and exotic colors, nearly any hues can be created in a metallic paint. However, darker shades do not provide as much sparkle and bling as the lighter ones. Aluminum flake is used to create the popular sparkle. These metallic flakes can generate different looks, but the results are largely dependent on the paint production process, the paint line application techniques, and the finished material’s final installation.
Optical dynamics
The light reflectance of the metallic flakes within the coating gives these finishes their lively appearance. The size and reflectivity of the flakes in the coating, their orientation, and the degree to which they are all oriented in the paint coating will affect the brightness of the color. This is sometimes referred to as the ‘flop of the flake.’
Like tiny mirrors, the flakes that lie horizontal in the paint will reflect the most light. In an optimally applied metallic coating, the flakes are randomly oriented. This will achieve the greatest level of sparkle and depth.
If all the flakes in the coating were to lie horizontally, the maximum amount of light would be reflected. The surface would look very bright to the point of appearing almost solid rather than sparkling. If the metallic flake content is too high, the shimmer is also diminished and again, it will appear to be solid color paint rather than a metallic.
Taken to another extreme, if all the metallic flakes were to lie vertically in the paint, very little light will be reflected. The surface would appear very dark and possibly eliminate the coating’s intended brilliance.
Finish composition and application
The paint composition and application play a key role in achieving the preferred optical dynamics of a consistently random flake orientation in metallic coatings.
Generally, a metallic paint consists of three layers: The first layer is a primer coat, necessary to assist with paint adhesion to the metal. The second layer is the resin, pigment, and metallic flake that provide the color and sparkle. The third and top layer is a clear coat, which is required with metallic finishes in order to impart the ultraviolet (UV) and weathering performance characteristics and to prevent the metallic flake from oxidizing.
