A Beautiful Body: STI Color Matching

In the world of service truck bodies, white is the industry-standard color. But for many customers, white isn’t an option. They need a specific color match. We can do that!

White. It’s familiar. It’s timeless. And it provides benefits for fleets and owners in a couple of ways: First, it provides a neutral, high-contrast background that allows logos and lettering to be easily readable. Even if a company has specific brand colors, white can serve as a background canvas for that branding. Second, it’s efficient. White trucks are more readily available in a variety of configurations, and often as work-ready models. There is no need to wait for a custom paint job, and fleets may be able to intermix truck and/or body manufacturers with virtually no visual differentiation.

However, for many customers, white is not an option. Whether a specific color is part of their visual branding, an effort to match other truck(s) in their fleet, or to separate themselves from the competition, a custom color match is a must.

The Science of Color Matching

The color matching process can take a lot of forms. If we’re matching a stock OEM color on a new chassis, we can streamline many steps. But if fleets or owners are trying to match colors from different chassis manufacturers, different models, different years, and different age and weather exposure, it’s a much more detailed endeavor. So, how do we account for so many variables when trying to match a chassis paint color for a new body?

STI partners with PPG for our paint and finish products. The PPG color matching process begins by using a Prophet – a handheld spectrophotometer “scanner” that assesses color from multiple angles. It’s specifically used for automotive color match applications. The prophet is placed directly in contact with the surface of the chassis or vehicle to be matched. It measures the exact color and texture of a vehicle’s paint—crucial for mixing exact formulas. It then provides a color code that is up to 99% accurate. That’s not perfect. To account for that 1%, the system also provides an additional 15-20 color codes, rated on a discrepancy scale of 0-5, with 0 being the most accurate. This allows us to test slightly different formulas.

The testing is done by creating Spray-out Cards. Spray-out cards simulate actual vehicle finishes and enable our paint department to evaluate different paint formulas to achieve a perfect match. Often, we will create 7-10 slightly different cards that can be evaluated under natural light or color-corrected lamps. This will be followed with a visual comparison with the cards held next to the chassis in different lighting.

Lighting is important, but another variable to consider in the spray-out process is how using a cup gun for the spray-out will translate to an actual application using a pressure gun. Exact specifics of the spray-out process are documented so painters in the booth can accurately match the application on the approved card.

The completed cards are filed and stored to create a physical reference library for each vehicle make, model, and color code. Remember the white truck example? We currently have nearly 25 variations of approved white cards in our catalog to meet unique customer specs.

Perfect Color Requires Meticulous Prep

Perfect color matching doesn’t start with the topcoat. Achieving a great color match requires thoughtful preparation to ensure the best adhesion and durability of the color-matched topcoat. The first preparation step is to de-grease the steel body and accompanying doors and parts to remove any contaminants left after sanding and pre-wash. After degreasing and power-washing thoroughly, we finish with a chemical that will help our etch-primer fuse with the bare metal.

Once this wash procedure is complete, we blow off all water, vacuum any dirt particles on the inside of the compartments, and then finish with another blow-cleaning. Caulk is then applied to all seams on both the inside and outside of the truck, using a commercial-grade polyurethane adhesive/sealant that forms a permanent bond. This helps prevent later water infiltration that may result in rusting.

We then pull the body and corresponding parts into one of our 2 paint booths to begin priming. Once inside, we tack the product to remove any fine particles. Our priming process starts with an etch primer. It is applied in a single coat and left to air-dry for approximately 10-15 minutes. Afterwards, we apply a urethane primer. This acts as a barrier, seals the acidic etch primer, and provides a sandable surface for final topcoats. We apply 3 coats to ensure we have at least a 4-mil thickness to protect the surface. The primer coats are then baked for an hour. After baking, any defects, runs, or sags are sanded smooth, blown clean and tacked again. Finally, we re-caulk any pinholes. This provides a clean smooth canvas for the paint.

Our topcoat procedure entails applying 3 coats using a single-stage method. This means that the color pigment and clear coat are mixed together for application. The clear coat provides UV protection, neutralizing ultraviolet damage that can degrade the color pigments. Choosing a single-stage application provides UV protection throughout the color, as opposed to using a final clear coat on top of the paint that may get damaged or break down over time.

Inspection/Evaluation:

Finally, we conduct an assessment that includes a visual overview from our inspection team. Any pinholes and seams are covered, paint is touched-up, and imperfections are fixed or re-painted. Only then can we be confident that we have a truck worthy of being delivered to our customers.